| 1. |
- Mousavi, Mahmoud, 1983-, et al.
(författare)
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Non-singular antiplane fracture theory within nonlocal anisotropic elasticity
- 2015
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; , s. 854-861
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Tidskriftsartikel (refereegranskat)abstract
- Abstract In the present paper, the distributed dislocation technique is applied for the analysis of anisotropic materials weakened by cracks. Eringen’s theory of nonlocal elasticity of Helmholtz type is employed. The non-singular screw dislocation within anisotropic elasticity is distributed to model cracks of mode III. The corresponding dislocation density functions are evaluated using the proper crack-face boundary conditions. The nonlocal stress field within a plane weakened by cracks is determined. The crack opening displacement is also discussed within the framework of nonlocal elasticity. The stress singularity of the classical linear elasticity is removed by the introduction of the nonlocal theory of elasticity. The general anisotropic case and the special case of orthotropic material are studied. The effect of material orthotropy is presented for a crack which is not necessarily aligned with the principal orthotropy direction. ", keywords = Cracks; Anisotropy; Fracture mechanics; Dislocations; Nonlocal elasticity; Integral equations, isbn = 0264-1275, doi=https://doi.org/10.1016/j.matdes.2015.09.068
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| 2. |
- A. B. Marçal, L., et al.
(författare)
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Spatially resolved structural and chemical properties of the white layer in machined Inconel 718 super alloy
- 2024
-
Ingår i: Materials and Design. - 0264-1275. ; 239
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Tidskriftsartikel (refereegranskat)abstract
- Inconel 718 is one type of nickel-based alloy used for a large range of applications, including gas turbines and aeroengines components. Although mechanical and thermodynamic properties of this material have been deeply studied in the past years, a method able to investigate local properties of the thin white layer formed on the alloy surface after machining remains challenging. Here, a 90 nm X-ray beam is used to probe the local strain, crystal orientation, and chemical composition of grains in the white layer. Data reveals mosaicity induced by the tool during machining. The high spatial resolution, combined with crystal lattice sensitivity, shows that the average grain size is around 30 nm throughout the white layer, while the strain is anisotropic nearest to the surface. Results provide new insights on the basic properties of the white layer in super alloys, revealing important information about the impact of finish machining which might help to explain fatigue and cracking formation on these materials during their usage phase.
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| 3. |
- Aitomäki, Yvonne, et al.
(författare)
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Vacuum infusion of cellulose nanofibre network composites : Influence of porosity on permeability and impregnation
- 2016
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 95, s. 204-211
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Tidskriftsartikel (refereegranskat)abstract
- Addressing issues around the processing of cellulose nanofibres (CNF) composites is important in establishing their use as sustainable, renewable polymer reinforcements. Here, CNF networks of different porosity were made with the aim of increasing their permeability and suitability for processing by vacuum infusion (VI). The CNF networks were infused with epoxy using two different strategies. The permeability, morphology and mechanical properties of the dry networks and the resulting nanocomposites were investigated. Calculated fill-times for CNF networks with 50% porosity were the shortest, but are only less than the gel-time of the epoxy if capillary effects are included. In experiments the CNF networks were clearly wetted. However low transparency indicated that impregnation was incomplete. The modulus and strength of the dry CNF networks increased rapidly with decreasing porosity, but their nanocomposites did not follow this trend, showing instead similar mechanical properties to each other. The results demonstrated that increasing the porosity of the CNF networks to ≈ 50% gives better impregnation resulting in a lower ultimate strength, a higher yield strength and no loss in modulus. Better use of the flow channels in the inherently layered CNF networks could potentially reduce void content in these nanocomposites and thus increase their mechanical properties.
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| 4. |
- Alam, Md. Minhaj, et al.
(författare)
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Analysis of the stress raising action of flaws in laser clad deposits
- 2013
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Ingår i: Materials and Design. - : Elsevier BV. - 0261-3069 .- 0264-1275 .- 1873-4197. ; 46, s. 328-337
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Tidskriftsartikel (refereegranskat)abstract
- Fatigue cracking of laser clad cylindrical and square section bars depends upon a variety of factors. This paper presents Finite Element Analysis (FEA) of the different macro stress fields generated as well as stress raisers created by laser cladding defects for four different fatigue load conditions. As important as the defect types are their locations and orientations, categorized into zero-, one- and two-dimensional defects. Pores and inclusions become critical close to surfaces. The performance of as-clad surfaces can be governed by the sharpness of surface notches and planar defects like hot cracks or lack-of-fusion (LOF) are most critical if oriented vertically, transverse to the bar axis. The combination of the macro stress field with the defect type and its position and orientation determines whether it is the most critical stress raiser. Based on calculated cases, quantitative and qualitative charts were developed as guidelines to visualize the trends of different combinations.
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| 5. |
- Alam, Md. Minhaj, et al.
(författare)
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Generalising fatigue stress analysis of different laser weld geometries
- 2011
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 32:4, s. 1814-1823
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional elastic-plastic finite element analyses was carried out on a laser welded box beam in order to study the impact of the geometrical aspects of the joint type and weld root on the fatigue stress behaviour. Different experimental and hypothetical weld geometries were studied. Characteristic root shapes, measured by the plastic replica method, and critical geometrical aspects were classified and then studied by FE-analysis with respect to their impact on the maximum stress. The simulation of hypothetical transition geometries facilitated the identification of trends and the explanation of part of the phenomena. However, quantitative geometry criteria were only partially suitable to describe the relations. The results have shown that the combination of throat depth, local surface radius and its opening angle determines the peak stress value and its location. Beside extended throat depths, particularly larger toe radii and the avoidance of small opening angles and of surface ripples reduces the peak stress. The explanations were developed in a generalising manner, accompanied by illustrative and flow chart description.
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| 6. |
- Alimadadi, Hossein, 1983, et al.
(författare)
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Corrosion properties of electrodeposited nanocrystalline and amorphous patterned Ni-W alloy
- 2009
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Ingår i: MATERIALS & DESIGN. - : Elsevier BV. - 0261-3069 .- 0264-1275 .- 1873-4197. ; 30:4, s. 1356-1361
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Tidskriftsartikel (refereegranskat)abstract
- Nickel-tungsten with satisfactory corrosion properties is a promising alloy to replace hard chromium. Relatively high adhesion between copper substrate and electrodeposited Ni-W alloy results in patterned morphology due to crack formation. In this work, corrosion resistance of patterned Ni-W alloys comprising 0-26 at.%.W were studied by potentiodynamic polarization and EIS in a medium containing Cl-. It is shown that corrosion resistance of single phase Ni-W is superior to amorphous and dual phase coated layers. It is also found that crack density is the dominant affecting factor on corrosion resistance of amorphous Ni-W alloys.
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| 7. |
- Andres, Britta, 1986-, et al.
(författare)
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Cellulose binders for electric double-layer capacitor electrodes : The influence of cellulose quality on electrical properties
- 2018
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 141, s. 342-349
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose derivatives are widely used as binders and dispersing agents in different applications. Binders composed of cellulose are an environmentally friendly alternative to oil-based polymer binding agents. Previously, we reported the use of cellulose nanofibers (CNFs) as binders in electrodes for electric double-layer capacitors (EDLCs). In addition to good mechanical stability, we demonstrated that CNFs enhanced the electrical performance of the electrodes. However, cellulose fibers can cover a broad range of length scales, and the quality requirements from an electrode perspective have not been thoroughly investigated. To evaluate the influence of fiber quality on electrode properties, we tested seven samples with different fiber dimensions that are based on the same kraft pulp. To capture the length scale from fibers to nanofibrils, we evaluated the performance of the untreated kraft pulp, refined fibers, microfibrillated cellulose (MFC) and CNFs. Electrodes with kraft pulp or refined fibers showed the lowest electrical resistivity. The specific capacitances of all EDLCs were surprisingly similar, but slightly lower for the EDLC with CNFs. The same electrode sample with CNFs also showed a slightly higher equivalent series resistance (ESR), compared to those of the other EDLCs. Graphite dispersions with MFC showed the best dispersion stability.
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| 8. |
- Asnafi, Nader, 1960-
(författare)
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Springback and fracture in v-die air bending of thick stainless steel sheets
- 2000
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 21:3, s. 217-236
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Tidskriftsartikel (refereegranskat)abstract
- In this investigation, the attention is focused on the springback and fracture of thick stainless steel sheets. Nine different stainless grades and various thickness are tested. The thinnest sheet is 7.9 mm, whilst the thickest sheet is 31.3 mm. A consistent analytical model is constructed for prediction of the springback, the inner sheet radius prior to and after unloading, and the smallest die width. The springback calculated by this analytical model is in all cases smaller than that found experimentally. The correspondence between theory and practice, is however, very good, although the shift in the position of the neutral axis and thinning are neglected in the theoretical analysis. Fracture did not occur in any of the conducted bending operations. It is commonly assumed that fracture in v-die bending is related to the reduction in the cross-section area at fracture, Z, in tensile testing. Z was greater than 70% for the majority of the studied materials. It is shown that particularly the mode of fracture (fracture through shear bands or by necking) should be studied in future investigations.
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| 9. |
- Balpande, A. R., et al.
(författare)
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Excellent specific strength-ductility synergy in novel complex concentrated alloy after suction casting
- 2024
-
Ingår i: Materials and Design. - 1873-4197 .- 0264-1275. ; 242
-
Tidskriftsartikel (refereegranskat)abstract
- Lightweight alloys are known to improve the fuel efficiency of the structural components due to high strength-to-weight ratio, however, they lack formability at room temperature. This major limitation of poor formability is most of the time overcome by post-fabrication processing and treatments thereby increasing their cost exponentially. We present a novel Ti50V16Zr16Nb10Al5Mo3 (all in at. %) complex concentrated alloy (Ti-CCA) designed based on the combination of valence electron concentration theory and the high entropy approach. The optimal selection of constituent elements has led to a density of 5.63 gm/cc for Ti-CCA after suction casting (SC). SC Ti-CCA displayed exceptional room temperature strength (UTS ∼ 1.25 GPa) and ductility (ε ∼ 35 %) with a yield strength (YS) of ∼ 1.1 GPa (Specific YS = 191 MPa/gm/cc) without any post-processing treatments. The exceptional YS in Ti-CCA is attributed to hetero grain size microstructure, whereas enormous strength-ductility synergy is due to the concurrent occurrence of slip and deformation band formation in the early stages of deformation followed by prolonged necking event due to delayed void nucleation and growth. The proposed philosophy of Ti-CCA design overcomes the conventional notion of strength-ductility trade-off in such alloy systems by retaining their inherent characteristics.
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| 10. |
- Belov, Ilja, et al.
(författare)
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Finite element modeling of silver electrodeposition for evaluation of thickness distribution on complex geometries
- 2016
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 90, s. 693-703
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Tidskriftsartikel (refereegranskat)abstract
- The paper reveals benefits of multi-disciplinary computer simulation and parametric studies in the design of silver plating process for improved coating distribution. A finite element model of direct current silver plating is experimentally validated for an Assaf panel without agitation. The model combines tertiary current distribution with Butler-Volmer electrode kinetics and computational fluid dynamics at a very low flow-rate. The effect of charge transfer coefficients on the throwing power of the process is quantified for the studied geometry, and variation of cathodic current density and exchange current density is investigated. A simpler model based on secondary current distribution is employed to quantify the effect of electrolyte conductivity on the throwing power of the process. A model combining tertiary current distribution and computational fluid dynamics has been developed and experimentally validated for simulation of complex telecom component electroplating in agitated electrolyte. The effect of current density on the process throwing power is quantified. Recommendations regarding modeling methodology and the effect of electrochemical and process parameters on the thickness distribution have been developed.
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| 11. |
- Bhattacharjee, Rahul, et al.
(författare)
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Synergy of nanocarriers with CRISPR-Cas9 in an emerging technology platform for biomedical appliances : Current insights and perspectives
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 224
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Tidskriftsartikel (refereegranskat)abstract
- Genetic editing technologies have emerged as a potential therapeutic tool in various biomedical fields owing to their applications against cancer, neurological diseases, diabetes, autoimmune disorder, muscu-lar dystrophy, bacterial infections (AMR), and cardiovascular diseases. CRISPR is one such valuable genetic editing tool with extensive therapeutic appliances but with a major challenge in terms of deliv-ery. Herein, we have strived to exploit a synergy of nanocarriers and CRISPR against the aforementioned diseases for their medical applications and explicated their clinical significance including the enhanced delivery via endosomal escape and environmental factors such as light, pH, and stimuli. In addition to highlighting the delivery strategies of nano-carriers for CRISPR and their characterization, we have expounded on the reliant factor of the CRISPR-Cas Complex.
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| 12. |
- Björklund, Stefan, 1969-, et al.
(författare)
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Function-dependent coating architectures by hybrid powder-suspension plasma spraying : Injector design, processing and concept validation
- 2018
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 142, s. 56-65
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Tidskriftsartikel (refereegranskat)abstract
- The attractive properties achieved by Suspension Plasma Spraying (SPS), combined with the availability of high throughput capable plasma spray systems that permit axial feeding, provide encouragement to explore use of suspensions for next generation functional applications. This paper deals with realization of coatings with various pre-determined function-dependent architectures by employing a hybrid powder-suspension feedstock. Some illustrative application-relevant coating architecture designs are discussed, along with the specific benefits that can accrue by deploying a multi-scale powder-suspension feedstock combination. An elegant feedstock delivery arrangement to enable either simultaneous or sequential feeding of powders and suspensions to enable convenient processing of coatings with desired architectures is presented. As proof-of-concept, deposition of layered, composite and functionally graded coatings using the above system is also demonstrated using appropriate case studies
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| 13. |
- Blixt, Kevin, et al.
(författare)
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Grain boundary and particle interaction: Enveloping and pass-through mechanisms studied by 3D phase field crystal simulations
- 2022
-
Ingår i: Materials & Design. - : Elsevier BV. - 0261-3069 .- 0264-1275. ; 220
-
Tidskriftsartikel (refereegranskat)abstract
- Grain boundary interaction with second-phase particles having different degrees of coherency is investigated using the phase field crystal (PFC) method. Both the enveloping and pass-through mechanisms are studied with regards to grain boundary pressure, passage time and interface evolution. It is found that coherent particles exert a stronger retardation effect on grain boundaries compared to incoherent particles, with regards to both pressure and time, but also that this benefit is limited to a small range of misfit values. The simulations also show that the mobility is not a constant during particle passage, as commonly assumed, which means that grain boundary pressure cannot easily be extracted from the grain boundary velocity. Furthermore, the complex evolution of the pass-through mechanism and the transient behavior for intermediate coherencies is also investigated. The highest drag force is found to occur at the switching point between enveloping and pass-through. As part of the study, the advantages of using PFC for this type of analyses are also highlighted.
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| 14. |
- Borkar, Hemant, et al.
(författare)
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In-situ EBSD study of deformation behavior of Al-Si-Cu alloys during tensile testing
- 2015
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 84, s. 36-47
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Tidskriftsartikel (refereegranskat)abstract
- This study deals with the microstructural aspects of the deformation behavior in Al-Si-Cu alloy A380. This has been carried out with in-situ tensile testing coupled with EBSD analysis. The alloy specimens having different microstructures with two different secondary dendrite arm spacing (SDAS) of 9 µm and 27 µm were produced by the unique gradient solidification method. The study of misorientation distribution and texture evolution was performed with different tools in EBSD analysis. The texture was not significantly affected by deformation in both types of alloy specimens. With increase in the deformation, the microstructures are characterized by degradation of EBSD patterns and generation of substructures including low angle boundaries (LABs) and high angle boundaries (HABs). In both the microstructures with low and high SDAS, the boundaries were concentrated around eutectic phases; however this behavior was more pronounced at higher SDAS. The increase in the fraction of LABs with deformation was much higher in the microstructure with higher SDAS than with lower SDAS. This localized strain concentration was especially attributed to the large and elongated eutectic Si particles and Fe-rich intermetallics. The lower mechanical properties obtained at higher SDAS are the result of inhomogeneous strain distribution in the microstructure.
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| 15. |
- Brandau, Benedikt, et al.
(författare)
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Absorbance study of powder conditions for laser additive manufacturing
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 216
-
Tidskriftsartikel (refereegranskat)abstract
- Absorbance is often used for simulations or validation of process parameters for powder-based laser materials processing. In this work, the absorbance of 39 metal powders for additive manufacturing is determined at 20 laser wavelengths. Different grain sizes and aging states for: steels, aluminum alloys, titanium alloys, Nitinol, high entropy alloy, chromium, copper, brass and iron ore were analyzed. For this purpose, the absorbance spectrum of the powders was determined via a dual-beam spectrometer in the range of λ = 330 - 1560 nm. At the laser wavelengths of λ = 450 nm, 633 nm and 650 nm, the absorbance averaged over all materials was found to increase by a factor of 2.4 up to 3.3 compared to the usual wavelength of λ = 1070 nm, with minimal variations in absorbance between materials. In the investigation of the aged or used powders, a loss of absorbance was detectable. Almost no changes from the point of view of processing aged and new AlSi10Mg powders, is expected for laser sources with λ = 450 nm. The resulting measurements provide a good basis for process parameters for a variety of laser wavelengths and materials, as well as a data set for improved absorbance simulations.
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| 16. |
- Bressi, Sara, et al.
(författare)
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An advanced methodology for the mix design optimization of hot mix asphalt
- 2016
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 98, s. 174-185
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Tidskriftsartikel (refereegranskat)abstract
- The bitumen quantity to add to asphalt mixtures depends on the surfaces of aggregates and filler to be coated. The formulas currently available in the literature have limitations such as considering all the fillers with the same specific surface or the aggregates with spherical or cubical shapes. This paper aims to define an analytical approach for the determination of the optimal dosage of bitumen in HMA proposing new methodologies to go a step further in the resolution of the above mentioned approximations. Indeed, new surface area factors were calculated to determine the aggregates surface considering their real shapes and volumes. Afterwards, the authors proposed a detailed characterization of two types of fillers and the critical filler concentration, introduced by Faheem and Bahia, was used to calculate the minimum amount of bitumen for maintaining the mastic in a diluted state and filling the voids in the mixtures. Finally, a verification of the formula developed was carried out with specific laboratory tests. These results allow the challenge of revising the method of calculating the specific surface of the aggregates and filler to be addressed with the final goal to include them in a new mix design optimization for HMA.
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| 17. |
- Buck, Dietrich, et al.
(författare)
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Moisture- and mould-resistance : modelling of edge-sealed cross-laminated timber using multi-modal assessment leveraged by X-ray computed tomography
- 2023
-
Ingår i: Materials and Design. - 0264-1275. ; 230
-
Tidskriftsartikel (refereegranskat)abstract
- Edge-sealing, which involves treating the edges of wood products, improves water resistance. This study investigated the feasibility of edge-sealed cross-laminated timber (CLT) panels to reduce capillary water uptake, thereby resisting mould formation. The water and vapour permeabilities of ten characteristically different single-layer sealant coating systems were systematically determined. X-ray computed tomography (CT) scanning methodology was used to enhance detection of material characteristics beyond the standard coating permeability assessment. Moisture content was observed to change during the specimens’ absorption and desorption depending on the sealant system applied. The results revealed different characteristics of coatings during the water absorption and desorption stages. Findings from this study were used to develop recommendations regarding the water resistance of coating systems, curing time, susceptibility to mould formation, and industrial applicability. Results suggest that edge-sealed CLT could minimise the risk of mould formation, which can occur at worksites with minimal weather protection. The method developed in this study provides a basis to evaluate new coating systems and determine which use case is the best for a particular coating type. This study also incorporates insights from industry to identify future research orientations, which may pave the way for new designs and assessment techniques.
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| 18. |
- Buck, Dietrich, 1990-, et al.
(författare)
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Moisture- and mould-resistance: multi-modal modelling leveraging X-ray tomography in edge-sealed cross-laminated timber
- 2023
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 230
-
Tidskriftsartikel (refereegranskat)abstract
- Edge-sealing, which involves treating the edges of wood products, improves water resistance. This study investigated the feasibility of edge-sealed cross-laminated timber (CLT) panels to reduce capillary water uptake, thereby resisting mould formation. The water and vapour permeabilities of ten characteristically different single-layer sealant coating systems were systematically determined. Multi-modal assessment leveraged by computed tomography (CT) scanning methodology was used to enhance detection of material characteristics beyond the standard coating permeability assessment. Moisture content was observed to change during the specimens’ absorption and desorption depending on the sealant system applied. The results revealed different characteristics of coatings during the water absorption and desorption stages. Findings from this study were used to develop recommendations regarding the water resistance of coating systems, curing time, susceptibility to mould formation, and industrial applicability. Results suggest that edge-sealed CLT could minimise the risk of mould formation, which can occur at worksites with minimal weather protection. The method developed in this study provides a basis to evaluate new coating systems and determine which use case is the best for a particular coating type. This study also incorporates insights from industry to identify future research orientations, which may pave the way for new designs and assessment techniques.
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| 19. |
- Cabo Rios, Alberto, 1990, et al.
(författare)
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Ex-situ characterization and simulation of density fluctuations evolution during sintering of binder jetted 316L
- 2024
-
Ingår i: Materials and Design. - 1873-4197 .- 0264-1275. ; 238
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Tidskriftsartikel (refereegranskat)abstract
- Efficient density evolution during sintering of the as-printed component is vital to reach full densification and required properties of binder jet (BJT) components. However, due to the high porosity and brittle nature of the green compact, analysis of the microstructure development during sintering is very difficult, resulting in lack of understanding of the densification process. Density development from green state (57 ± 1.6 %) up to full density (99 ± 0.3 %) was characterized by high-resolution synchrotron X-Ray computed tomography (SXCT) on BJT 316L samples from ex-situ interrupted sintering tests. Periodicity of density fluctuations along the building direction was revealed for the first time and was related to the layer thickness of ∼ 42 µm during printing that decreased down to ∼ 33 µm during sintering. Sintering simulations, utilizing a continuum sintering model developed for BJT, allowed to replicate the density evolution during sintering with a mean error of 2 % and its fluctuation evolution from green (1.66 %) to sintered (0.56 %) state. Additionally, simulation of extreme particle size segregation (1 µm to 130 µm) suggested that non-optimized printing could lead to undesirable density fluctuation amplitude rapid increase (∼10 %) during sintering. This might trigger the nucleation of defects (e.g., layer delamination, cracking, or excessive residual porosity) during the sintering process.
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| 20. |
- Čapek, J., et al.
(författare)
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Influence of laser powder bed fusion scanning pattern on residual stress and microstructure of alloy 718
- 2022
-
Ingår i: Materials & design. - : Elsevier Ltd. - 0264-1275 .- 1873-4197. ; 221
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Tidskriftsartikel (refereegranskat)abstract
- A comprehensive investigation is undertaken on the effect of laser scanning pattern on the microstructure of cylindrical samples made of Alloy 718 processed by Laser Powder Bed Fusion. It is observed that the common alternate direction scanning of the laser results in a more homogeneous microstructure than the less common concentric line scans where significant microstructural heterogeneities are seen between the edges and the center of the sample. The investigation focuses on the precipitation, crystallographic texture, grain size, grain morphology and residual stresses utilizing synchrotron X-ray diffraction, neutron diffraction and electron microscopy. The heterogeneous microstructure of the sample processed with the concentric laser pattern influences the chemical composition of the matrix, which alters the reference “strain free” interplanar spacing used for evaluating the residual strain. The investigation underlines the significance of the processing parameters on the homogeneity of the microstructure and the effect of the chemical variations on the determination of residual stresses in materials such as Alloy 718, where strong local chemical variations occur because of different types and extent of precipitation. © 2022
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| 21. |
- Carlsson, Bo
(författare)
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Selecting material for the exterior panel of a private car back door by adopting a total cost accounting approach
- 2009
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 30:3, s. 826-832
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Tidskriftsartikel (refereegranskat)abstract
- A total cost accounting approach for material selection is demonstrated by analysing the suitability of some light weight materials for use in the exterior panel of a back door to a private car. For pre-selection purposes, the suitability of using low alloy steel, aluminium, SMC and a hybrid GMT/aluminium material as construction material for the exterior panel of the back door are compared by taking into account differences in production cost, cost associated with excess mass, cost of probable failures and damages, maintenance and operational costs, end-of-life cost, and cost associated with probable ecological damage. From one manufacturer's point of view and considering only the production cost for the installed part of the back door, steel is the best alternative for large production volumes. However, this is not the case when taking into account all costs. All the other materials seem better and exhibit essentially the same qualities. The main reason is lower fuel consumption. The results of the suitability analysis nicely reflect the relative importance of the various factors contributing to the total cost but the suitability analysis also points to the need of performing a more advanced analysis taking into account also aspects like safety and ease of surface treatment.
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| 22. |
- Carosio, Federico, et al.
(författare)
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Clay nanopaper as multifunctional brick and mortar fire protection coating : Wood case study
- 2016
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 93, s. 357-363
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Wood is one of the most sustainable, esthetically pleasing and environmentally benign engineering materials, and is often used in structures found in buildings. Unfortunately, the fire hazards related to wood are limiting its application. The use of transparent cellulose nanofiber (CNF)/clay nanocomposites, with unique brick-and-mortar structure, is proposed as a sustainable and efficient fire protection coating for wood. Fire performance was assessed by cone calorimetry. When exposed to the typical 35 kW/m2 heat flux of developing fires, the time to ignition of coated wood samples increased up to about 4 1/2 min, while the maximum average rate of heat emission (MARHE) was decreased by 46% thus significantly reducing the potential fire threat from wood structures.
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| 23. |
- Celma Cervera, Carlos, et al.
(författare)
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Contact-induced deformation and damage of rocks used in pavement materials
- 2017
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 133, s. 255-265
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Tidskriftsartikel (refereegranskat)abstract
- Performance of stone-based construction materials, such as asphalt and unbound aggregate mixtures is defined to a great extent by the mechanics of the stone-to-stone interactions. Accordingly, the Discrete Element Method (DEM) is gaining popularity as a modelling tool to investigate the mechanical behavior of these materials. Contact and failure laws defining particles force-displacement relationships and the propensity of particles to break are crucial inputs for the DEM simulations. The present study aims at providing an experimental contact mechanics basis for the development of physically based stone-to-stone interaction laws. The attention is focused on investigating stone's force-displacement relationship and damage characteristics at pure normal loading for two stone materials used by the road industry. Experiments are performed at spherical contact profiles for cyclic and monotonically increasing loads. The emphasis lies on the evolution of contact compliance and accumulation of contact induced damage. The effect of surface roughness on the materials response is examined through comparative experiments performed on the specimens with different roughness values. Optical and environmental scanning electron microscopy (ESEM) observations of the contact induced damage at the material surface are presented and discussed in the context of contact mechanics. The implications of the reported experimental findings on the development of mechanics based contact and failure laws for the DEM modelling of stone-based construction materials are discussed.
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| 24. |
- Ceschini, Lorella, et al.
(författare)
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Effect of Fe content and microstructural features on the tensile and fatigue properties of the Al-Si10-Cu2 alloy
- 2012
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 36, s. 522-528
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Tidskriftsartikel (refereegranskat)abstract
- As the automotive industry has to meet the requirements of fuel efficiency and environmental concerns, the use of aluminium alloys is steadily increasing. A number of papers have been published about the correlation between microstructure and mechanical properties of the widely used A356/A357 aluminium alloys, while relatively few data are available on others hypoeutectic Al-Si alloys, such as Al-Si-Cu alloys with higher Si content. In this work the effect of different amounts of Fe and Mn on the tensile and fatigue behaviour of the AlSi10Cu2 casting alloy was studied. The reason of this study comes from the fact that cast components are mostly made by secondary Al alloys that inevitably contain Fe, which in turn forms intermetallic compounds, negatively affecting the mechanical behaviour of the alloy. Fatigue specimens were subjected to hot isostatic pressing (HIP) before tests, in order to eliminate the internal pores (gas pores and interdendritic shrinkages) and therefore to solely investigate the effect of microstructural features, rather than solidification defects, on the fatigue propagation stage. The microstructural characterization of the alloy was carried out by optical and scanning electron microscopy. Proof and ultimate tensile strength, as well as fatigue life of the investigated alloy were greatly enhanced by high Fe and Mn content, which reduced the micro-crack propagation rate; on the contrary Fe, without Mn, negatively affected the elongation to failure.
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| 25. |
- Ceschini, Lorella, et al.
(författare)
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Effect of Microstructure and Overaging on the Tensile Behavior at Room and Elevated Temperature of C355-T6 Cast Aluminum Alloy
- 2015
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 83, s. 626-634
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Tidskriftsartikel (refereegranskat)abstract
- The present study was focused on the microstructural and mechanical characterization of the Al–Si–Cu–Mg C355 alloy, at room and elevated temperature. In order to evaluate the influence of microstructural coarseness on mechanical behavior, samples with different Secondary Dendrite Arm Spacing (SDAS) (20–25 μm for fine microstructure and 50–70 μm for coarse microstructure), were produced through controlled casting conditions. The tensile behavior of the alloy was evaluated at T6 condition and at T6 with subsequent high temperature exposure (41 h at 210 °C, i.e. overaging), both at room and elevated temperature (200 °C). Microstructural investigations were performed through optical and electron microscopy.The results confirmed the important role of microstructure on the tensile behavior of C355 alloy. Ultimate tensile strength and elongation to failure strongly increased with the decrease of SDAS. Larger SDAS, related to lower solidification rates, modify microstructural features, such as eutectic Si morphology and size of the intermetallic phases, which in turn influence elongation to failure. Overaging before tensile testing induced coarsening of the strengthening precipitates, as observed by STEM analyses, with consequent reduction of the tensile strength of the alloy, regardless of SDAS. A more sensible decrease of tensile properties was registered at 200 °C testing temperature.
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| 26. |
- Chen, Feng, 1987-, et al.
(författare)
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A state-of-the-art review of intrinsic and enhanced electrical properties of asphalt materials: theories, analyses and applications
- 2020
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 195, s. 109067-
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Tidskriftsartikel (refereegranskat)abstract
- In pavement engineering, a variety of promising application technologies are found relying on a thorough understanding of the intrinsic (mainly dielectric) electrical properties of asphalt binder and concrete materials. Meanwhile, the electrical properties of asphalt materials can be further enhanced by introducing conductive additives into and it has been brought to light that, the electrically conductive asphalt is becoming an emerging subject of interest that caters to the concept of a multifunctional pavement future. In context of these, this paper presents a holistic overview of the intrinsic and enhanced electrical properties of asphalt materials, including the theoretical analyses, as well as the corresponding applications in the practice. From such a state-of-the-art review, it is worth noting that: i) an improved understanding of asphalt material has been achieved by an in-depth examination of its electrical properties; ii) the increased significance of the research domain as a whole and, the key importance of multidisciplinary collaborations for future successes, have been indicated.
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| 27. |
- Choi, Young Won, et al.
(författare)
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Predicting the stacking fault energy of austenitic Fe-Mn-Al (Si) alloys
- 2020
-
Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 187
-
Tidskriftsartikel (refereegranskat)abstract
- Aluminum and silicon are common alloying elements for tuning the stacking fault energy (SFE) of high Mn steels. Today the theoretical investigations on the Fe-Mn-Al/Si systems using Density Functional Theory (DFT) are very scarce. In the present study, we employ a state-of-the-art longitudinal spin fluctuations (LSFs) model in combination with DFT for describing the magnetic effects in Fe-Mn based alloys at finite temperature. We find that the traditional DFT-floating spin results fail to explain the experimental trends. However, the DFT-LSFs approach properly captures the Al-induced increase and Si-induced decrease of the SFE of the base alloy in line with the room-temperature observations. This finding highlights the importance of LSFs in describing the Al/Si effects on the SEE of Fe-Mn based alloys. We point out that the effects of the non-magnetic Al and Si additions on the SEE are in fact determined by the magnetic state of the host matrix. In addition, we estimate the role of carbon addition in the alloying effects of Al and Si. The present results provide a convenient pathway to access the important mechanical parameters for designing advanced high-strength alloys.
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| 28. |
- Ciripova, Lucia, et al.
(författare)
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Prediction of mechanical properties of Fe–Cr–Mo sintered steel in relationship with microstructure
- 2012
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Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275 .- 0261-3069. ; 35:1, s. 619-625
-
Tidskriftsartikel (refereegranskat)abstract
- The contribution deals with the evaluation of required thermodynamic conditions for proper sinteringand prediction of tensile and yield strength of Cr–Mo-pre-alloyed sintered steel. The material used inexperiment was Fe–1.5 Cr–0.2 Mo pre-alloyed water atomised steel powder with addition 0.3–0.7% ofgraphite. Three different sintering routes were used applying sintering at 1180 and 1250 °C for 40 and60 min in 10%H2 + 90%N2 atmosphere of different purity. The influence of sintering conditions on themicrostructure and mechanical properties of sintered Fe–1.5Cr–0.2Mo–(0.3–0.7)C steels is analyzedand mechanical properties are predicted. Results indicate that very accurate prediction of mechanicalproperties can be achieved for sintered steel with bainitic microstructure (higher carbon content) andhigher differences were obtained for ferritic–pearlitic microstructures. High sensitivity of mechanicalproperties on sintering atmosphere purity for chromium prealloyed powder steel was identified.Required sintering atmosphere composition and purity for successful sintering of studied material wereevaluated.
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| 29. |
- Croné, Philip, et al.
(författare)
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Continuum plasticity modelling of work hardening for precipitation-hardened martensitic steel guided by atom probe tomography
- 2022
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 215
-
Tidskriftsartikel (refereegranskat)abstract
- An analytical flow stress model, based on isotropic strain gradient plasticity theory, for precipitation hardened materials, is proposed and evaluated against tensile data on a 15 wt% Cr - 5 wt% Ni (15-5) PH stainless steel. The 15-5 PH material was aged at 500 °C for 1 h, 2 h, 5 h and 50 h to obtain a wide range of precipitate sizes. Detailed characterisation of precipitates was obtained using atom probe tomography (APT). A second material, a 15-5 stainless steel without added Cu was heat treated to obtain a similar matrix microstructure as in the 15-5 PH, but without Cu precipitates. Tensile testing revealed that the heat treated 15-5 PH material covered the full range from under- to overaged conditions. The analytical model, which accounts for stress reducing effects of plastic relaxation around particles, manages to capture the experimental data in a very satisfying manner using only a total of three tunable parameters. It is believed that the proposed model can offer an alternative to the much more commonly used work hardening models based on the internal variable approach.
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| 30. |
- Cui, Luqing, et al.
(författare)
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Revealing Relationships between Microstructure and Hardening Nature of Additively Manufactured 316L Stainless Steel
- 2021
-
Ingår i: Materials & Design. - : Elsevier. - 0261-3069 .- 0264-1275. ; 198
-
Tidskriftsartikel (refereegranskat)abstract
- Relationships between microstructures and hardening nature of laser powder bed fused (L-PBF) 316 L stainless steel have been studied. Using integrated experimental efforts and calculations, the evolution of microstructure entities such as dislocation density, organization, cellular structure and recrystallization behaviors were characterized as a function of heat treatments. Furthermore, the evolution of dislocation-type, namely the geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs), and their impacts on the hardness variation during annealing treatments for L-PBF alloy were experimentally investigated. The GND and SSD densities were statistically measured utilizing the Hough-based EBSD method and Taylor's hardening model. With the progress of recovery, the GNDs migrate from cellular walls to more energetically-favourable regions, resulting in the higher concentration of GNDs along subgrain boundaries. The SSD density decreases faster than the GND density during heat treatments, because the SSD density is more sensitive to the release of thermal distortions formed in printing. In all annealing conditions, the dislocations contribute to more than 50% of the hardness, and over 85.8% of the total dislocations are GNDs, while changes of other strengthening mechanism contributions are negligible, which draws a conclusion that the hardness of the present L-PBF alloy is governed predominantly by GNDs.
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| 31. |
- Da Silva, Adrien, et al.
(författare)
-
Additive Manufacturing by laser-assisted drop deposition from a metal wire
- 2021
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 209
-
Tidskriftsartikel (refereegranskat)abstract
- The subject of Additive Manufacturing includes numerous techniques, some of which have reached very high levels of development and are now used industrially. Other techniques such as Micro Droplet Deposition Manufacture are under development and present different manufacturing possibilities, but are employed only for low melting temperature metals. In this paper, the possibility of using a laser-based drop deposition technique for stainless-steel wire is investigated. This technique is expected to be a more flexible alternative to Laser Metal Wire Deposition. Laser Droplet Generation experiments were carried out in an attempt to accurately detach steel drops towards a desired position. High-speed imaging was used to observe drop generation and measure the direction of detachment of the drops. Two drop detachment techniques were investigated and the physical phenomena leading to the drop detachment are explained, wherein the drop weight, the surface tension and the recoil pressure play a major role. Optimised parameters for accurate single drop detachment were identified and then used to build multi-drop tracks. Tracks with an even geometry were produced, where the microstructure was influenced by the numerous drop depositions. The tracks showed a considerably higher hardness than the base wire, exhibiting a relatively homogeneous macro-hardness with a localised softening effect at the interfaces between drops.
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| 32. |
- Da Silva, Adrien, et al.
(författare)
-
Influence of aluminium powder aging on Directed Energy deposition
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 218
-
Tidskriftsartikel (refereegranskat)abstract
- The use of aluminium alloys for Additive Manufacturing is of high interest for advanced geometries and lightweight applications. In Directed Energy Deposition, a powder stock is processed with a laser beam, which offers a high process flexibility. However, aging of the powder feedstock during storage or after recycling remains fundamentally challenging for aluminium alloys because of their sensitivity to oxida-tion and porosity. In order to investigate these effects, AlSi10Mg powder batches were aged in different conditions and processed by Directed Energy Deposition. The results showed that powder aging does not significantly change the particle size or morphology, but it introduces more oxygen and hydrogen in the powder. The oxidation of the particles reduces the laser beam absorbance of the powder and increases wetting of the melt pool, which affects the track geometry. A 3.5 to 4.2 times higher porosity was observed in the material deposited from aged powder, which are most likely hydrogen pores causedby the increased hydrogen content in the aged powder. The tensile properties of the parts built with aged powder showed 19.0% lower yield strength, 14.2% lower ultimate strength and 99.2% higher elongation, which are most likely the results of the coarser microstructure and increased porosity.
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| 33. |
- Dai, J. H., et al.
(författare)
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Theoretical investigation of the phase stability and elastic properties of TiZrHfNb-based high entropy alloys
- 2019
-
Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 182
-
Tidskriftsartikel (refereegranskat)abstract
- First principles calculations are performed to study the effects of alloying elements (X = Al, Si, Sc, V, Cr, Mn, Cu, Zn, Y. Mo, Ta, W and Re) on the phase stability and elastic properties of TiZrHfNb refractory high entropy alloys. Both equimolar and non-equimolar alloys are considered. It is shown that the calculated lattice parameters, phase stability and elastic moduli of equimolar TiZrHfNbX are consistent with the available experimental and theoretical results. The substitutions of alloying elements at Ti, Zr, and Hf sites with various contents show similar effects on the phase stability and elastic properties of the TiZrHINb-based alloys. The substitutions on Nb site are found to generally decrease the stability of body centered cubic phase. Close connections between the charge densities at the Wigner-Seitz cell boundary and the bulk moduli of TiZrHfNb-based alloys are found. The present results provide a quantitative model for exploring the phase stability and elastic properties of TiZrHINb-based alloys from the electronic structure viewpoint. Elsevier Ltd.
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| 34. |
- Davoodi, M.M., et al.
(författare)
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Concept selection of car bumper beam with developed hybrid bio-composite material
- 2011
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 32:10, s. 4857-4865
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Tidskriftsartikel (refereegranskat)abstract
- Application of natural fibre composites is going to increase in different areas caused by environmental, technical and economic advantages. However, their low mechanical properties have limited their particular application in automotive structural components. Hybridizations with other reinforcements or matrices can improve mechanical properties of natural fibre composite. Moreover, geometric optimizations have a significant role in structural strength improvement. This study focused on selecting the best geometrical bumper beam concept to fulfill the safety parameters of the defined product design specification (PDS). The mechanical properties of developed hybrid composite material were considered in different bumper beam concepts with the same frontal curvature, thickness, and overall dimensions. The low-speed impact test was simulated under the same conditions in Abaqus V16R9 software. Six weighted criteria, which were deflection, strain energy, mass, cost, easy manufacturing, and the rib possibility were analyzed to form an evaluation matrix. Topsis method was employed to select the best concept. It is concluded that double hat profile (DHP) with defined material model can be used for bumper beam of a small car. In addition, selected concept can be strengthened by adding reinforced ribs or increasing the thickness of the bumper beam to comply with the defined PDS.
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| 35. |
- Davydova, Alexandra, et al.
(författare)
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Thio-olivine Mn2SiS4 thin films by reactive magnetron sputtering : Structural and optical properties with insights from first principles calculations
- 2018
-
Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 152, s. 110-118
-
Tidskriftsartikel (refereegranskat)abstract
- Thio-olivines such as (Fe,Mn)(2)(Si,Ge)S-4 have been proposed as candidate earth-abundant materials for single and multi-junction solar cells. In this work we present the first investigation of Mn2SiS4 thin films prepared by reactive magnetron sputtering deposition, using a composition grading approach. Precursor instability in ambient conditions is observed, revealing the oxidation/hydrolysis of Si-S bonds from the as-deposited film as a blocking mechanism for the ternary compound formation. Structural, morphological and optical properties of the annealed Mn2SiS4 films are reported for the first time. Resulting Mn2SiS4 films have orthorhombic Pnma structure and are polycrystalline. Raman active modes at 325 nm excitation are observed at 262, 320, 400 and 464 cm(-1). From room temperature photoluminescence at 532 nm excitation the band gap is estimated to be about 1.9 eV, but a high optical absorption coefficient of > 10(4) cm(-1) was only obtained at E > 2.8 eV.First principles calculations are used for better understanding of opto-electronic properties. From the calculations, Mn2SiS4 is suggested to have a band gap of about 1.73-1.86 eV depending on the magnetic configuration of Mn and slight indirect nature. The slow absorption onset is interpreted by strong anisotropy due to one of the components of the dielectric function.
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| 36. |
- Dehestani, Mahdi, et al.
(författare)
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Mechanical properties and corrosion behavior of powder metallurgy iron-hydroxyapatite composites for biodegradable implant applications
- 2016
-
Ingår i: Materials and Design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 109, s. 556-569
-
Tidskriftsartikel (refereegranskat)abstract
- Nine Fe–HA composites were fabricated via powder metallurgy method by varying the amount (2.5, 5, 10 wt%) and particle size (< 1 Όm, 1–10 Όm, 100–200 Όm) of hydroxyapatite (HA) as a bioactive phase in the iron (Fe) matrix. X-ray diffraction did not detect any phase changes in HA after the sintering process. Uniaxial tensile tests measured the strengths of the composites. Polarization and immersion tests estimated the corrosion rates (CR). Yield strength, tensile strength, and ductility of the composites decreased with increasing HA content and decreasing HA particle size, whereas their corrosion rates increased. The strongest composite was Fe–2.5 wt% HA (100–200 Όm) with σy = 81.7 MPa, σu = 130.1 MPa, fracture strain of 4.87%, and CR = 0.23 mmpy. The weakest composite was Fe–10 wt% HA (< 1 Όm) which did not exhibit plastic deformation, fractured at σu = 16.1 MPa with 0.11% strain, and showed the highest CR of 1.07 mmpy. This study demonstrates how the relative particle size between Fe and HA determines the mechanical and corrosion properties of Fe–HA composites, thereby aiding in enhancing future resorbable implant designs. The model can also be used when designing other bioactive composites (i.e. Ti–HA, Mg–HA) via powder metallurgy.
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| 37. |
- Deng, Dunyong, et al.
(författare)
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On the formation of microstructural gradients in a nickel-base superalloy during electron beam melting
- 2018
-
Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 160, s. 251-261
-
Tidskriftsartikel (refereegranskat)abstract
- Electron beam melting (EBM) is one of the most widely used additive manufacturing (AM) methods for metallic components and has demonstrated great potential to fabricate high-end components in the aerospace and energy industries. The thermal condition within a melt pool and the complicated thermal cycles during the EBM process are of interest but not yet well-understood, and will significantly affect the microstructural homogeneity of as-manufactured nickel-base superalloy components. To establish the thermal profile evolution during electron beam melting of nickel-base superalloys, Inconel 718 (IN718) is manufactured and characterized in the as-manufactured condition, on account of its representative segregation and precipitation behaviours. The microstructure gradient within a build, specifically the Laves phase volume fraction evolution, is rationalized with the solidification condition and the following in-situ annealing. Precipitations of carbide/nitride/carbonitride, delta and gamma/gamma are also discussed. Hardness is measured and correlated to the Laves phase volume fraction evolution and the precipitation of gamma/gamma . The results of this study will (i) shed light on microstructure evolution during the EBM process with regard to thermal history; and (ii) deepen the current understandings of solidification metallurgy for additive manufacturing of Ni-base superalloys. (C) 2018 Elsevier Ltd. All rights reserved.
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| 38. |
- Dippo, Olivia F., et al.
(författare)
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Color and pseudogap tunability in multicomponent carbonitrides
- 2022
-
Ingår i: Materials & design. - : Elsevier Science Ltd. - 0264-1275 .- 1873-4197. ; 217
-
Tidskriftsartikel (refereegranskat)abstract
- The design and tailoring of material color for both aesthetic and functionality is an ongoing topic of materials science and engineering research. In this work, a method is developed to tune and predict color and pseudogap energy of any compositional variation of B1-rocksalt structured Group 4 and 5 transition metal carbonitride. Optical properties of bulk multicomponent transition metal carbonitrides were characterized using reflectivity spectra. Optical pseudogap energies were extrapolated using the Tauc method, and color appearance was quantified in the Commission Internationale de lEclairage (CIE) Lightness*Chroma*hue (L*C*h) color space. Variations of color parameters chroma and hue were analyzed in terms of pseudogap energies and electronic band structures. Compositional variations were utilized to predictably tune aspects of the electronic structure, including the specificity of electronic transitions and the energy at which they occur, to tailor the materials color appearance and facilitate the formation of new carbonitride colors.
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| 39. |
- Dongale, T. D., et al.
(författare)
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Bifunctional nanoparticulated nickel ferrite thin films : Resistive memory and aqueous battery applications
- 2021
-
Ingår i: Materials & design. - : Elsevier Ltd. - 0264-1275 .- 1873-4197. ; 201
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, excellent non-volatile memory and aqueous battery properties of solution-processable nickel ferrite (NFO) nanomaterial were demonstrated. In the case of non-volatile memory property, the device operates on ±2 V resistive switching voltage and shows double valued charge-magnetic flux characteristics. Excellent endurance (103) and retention (104 s) non-volatile memory properties with a good memory window (103) were observed for NFO memristive device. The conduction and resistive switching mechanisms based on experimental data are provided. Furthermore, the present work investigates the electrochemical performance of the NFO thin film electrode in the different electrolytes (viz. Na2SO4, Li2SO4, and Na2SO4: Li2SO4). It was revealed that the NFO thin film shows improved electrochemical performance in Na2SO4 electrolyte with a high specific capacity of 18.56 mAh/g at 1 mA/cm2 current density. The electrochemical impedance spectroscopic results reveal that the NFO thin film electrode shows low series and charge transfer resistance values for Na2SO4 electrolyte than other electrolytes. The diffusion coefficient of different ions (DNa+, DLi+ and DNa+:Li+) were found to be 9.975 × 10−10 cm2 s−1, 3.292 × 10−11 cm2 s−1, 2 × 10−10 cm2 s−1, respectively. A high diffusion coefficient was found for Na+ ions, indicating rapid Na+ transport with NFO thin-film electrodes © 2021 The Authors
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| 40. |
- Dorri, Samira, et al.
(författare)
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Effects of stoichiometry and individual layer thickness ratio on the quality of epitaxial CrBx/TiBy superlattice thin films
- 2023
-
Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 228
-
Tidskriftsartikel (refereegranskat)abstract
- Studies of single crystal artificial superlattices (SLs) of transition-metal (TM) diborides, which is instru- mental to understand hardening mechanisms at nanoscale, is lacking. Here, CrBx/TiBy (0001) diboride SLs [x,y E 1.7-3.3] are grown epitaxially on Al2O3(0001) substrates by direct-current magnetron sputter epitaxy. Growth conditions for obtaining well-defined SLs with good interface quality are found at 4 mTorr Ar pressure and 600 degrees C. 1 -mu m-thick SL films deposited with modulation periods A between 1 and 10 nm, and A=6 nm SLs with TiBy-to-A layer thickness ratios F ranging from 0.2 to 0.8 are studied. SLs with A=6 nm and F in the range of 0.2-0.4, with a near stoichiometric B/TM ratio, exhibit the high- est structural quality. The effects of F and stoichiometries (B/TM ratio) on the distribution of B in the SL structures are discussed. By increasing the relative thickness of TiBy, the crystalline quality of SLs starts to deteriorate due to B segregation in over-stoichiometric TiBy, resulting in narrow epitaxial SL columnar growth with structurally-distorted B-rich boundaries. Moreover, increasing the relative thickness of under-stoichiometric CrBx enhances the SL quality and hinders formation of B-rich boundaries. The SLs are found to exhibit hardness values in the range of 29-34 GPa.(c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 41. |
- Ekstrand, Gunnar, et al.
(författare)
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On testing of the stiffness and the dent resistance of autobody panels
- 1998
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 19:4, s. 145-156
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study has been to establish a platform which can be used in future attempts to set up at least a reasonable (scientifically based) company standard for stiffness and dent resistance tests. Stiffness and dent testing equipment was developed and used in this investigation. This equipment, which is mounted in a mechanical testing machine, consists chiefly of three parts: a table, on which the panel is placed; a fixture, which is used to restrain the panel; and a punch, with which the panel centre is loaded. Two different punches are used: a flat-headed punch of diameter 100 mm in the stiffness tests and a hemispherical punch of diameter 25 mm in the dent resistance tests. The boundary conditions play a significant role in the stiffness and the dent resistance measurements. The largest stiffness is obtained with the boundary configuration case I, whilst the boundary configuration case IV yields the smallest stiffness. The attained experimental results show that the thicker the sheet thickness at the panel centre, the greater will be the panel stiffness. The greater the panel radii (the more severe the springback), the smaller the stiffness. The experimental results show too that the larger the initial yield strength, the higher is the dent resistance. The thicker the sheet, the higher is the dent resistance. The purpose of this study has been to establish a platform which can be used in future attempts to set up at least a reasonable (scientifically based) company standard for stiffness and dent resistance tests. Stiffness and dent testing equipment was developed and used in this investigation. This equipment, which is mounted in a mechanical testing machine, consists chiefly of three parts: a table, on which the panel is placed; a fixture, which is used to restrain the panel; and a punch, with which the panel centre is loaded. Two different punches are used: a flat-headed punch of diameter 100 mm in the stiffness tests and a hemispherical punch of diameter 25 mm in the dent resistance tests. The boundary conditions play a significant role in the stiffness and the dent resistance measurements. The largest stiffness is obtained with the boundary configuration case I, whilst the boundary configuration case IV yields the smallest stiffness. The attained experimental results show that the thicker the sheet thickness at the panel centre, the greater will be the panel stiffness. The greater the panel radii (the more severe the springback), the smaller the stiffness. The experimental results show too that the larger the initial yield strength, the higher is the dent resistance. The thicker the sheet, the higher is the dent resistance.
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| 42. |
- Ekström, Erik, et al.
(författare)
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Microstructure control and property switching in stress-free van der Waals epitaxial VO2 films on mica
- 2023
-
Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 229
-
Tidskriftsartikel (refereegranskat)abstract
- Realizing stress-free inorganic epitaxial films on weakly bonding substrates is of importance for applications that require film transfer onto surfaces that do not seed epitaxy. Film-substrate bonding is usually weakened by harnessing natural van der Waals layers (e.g., graphene) on substrate surfaces, but this is difficult to achieve in non-layered materials. Here, we demonstrate van der Waals epitaxy of stress-free films of a non-layered material VO2 on mica. The films exhibit out-of-plane 010 texture with three inplane orientations inherited from the crystallographic domains of the substrate. The lattice parameters are invariant with film thickness, indicating weak film-substrate bonding and complete interfacial stress relaxation. The out-of-plane domain size scales monotonically with film thickness, but the in-plane domain size exhibits a minimum, indicating that the nucleation of large in-plane domains supports subsequent island growth. Complementary ab initio investigations suggest that VO2 nucleation and van der Waals epitaxy involves subtle polarization effects around, and the active participation of, surface potassium atoms on the mica surface. The VO2 films show a narrow domain-size-sensitive electrical-conductiv ity-temperature hysteresis. These results offer promise for tuning the properties of stress-free van der Waals epitaxial films of non-layered materials such as VO2 through microstructure control (C) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 43. |
- Elbashir, Sana, 1984-, et al.
(författare)
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Thermodynamic modelling assisted three-stage solid state synthesis of high purity β-Ca3(PO4)2
- 2024
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 238
-
Tidskriftsartikel (refereegranskat)abstract
- A three-stage solid state synthesis assisted by thermodynamic modelling was developed to prepare highly pure (>99 %) beta tricalcium phosphate (β-TCP) powder. The optimal synthesis temperature was experimentally determined to be 1000 °C in good agreement with the theoretical calculations. The synthesis design described here has substantially improved the product quality and eliminated the presence of secondary phosphate phases compared to one- and two-stage methods investigated in this work. A comprehensive characterization of the material's structural, vibrational, and morphological characteristics was conducted. Rietveld refinement of the X-ray diffraction data confirmed the high purity of the samples. The crystal structure of the prepared β-TCP was determined and the refined unit cell parameters agreed well with the reference values. From infrared and Raman spectral analyses, the characteristics of β-TCP were observed and discussed in details. Furthermore, the morphology and elemental composition of the products were examined and found to be homogenous and impurity free. The reproducibility of the material was scrutinized and showed no significant data variations. Using our three-stage synthesis method, it is possible to produce β-TCP powder of high purity with consistent repeatability.
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| 44. |
- Ericsson, A., et al.
(författare)
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Transient nucleation in selective laser melting of Zr-based bulk metallic glass
- 2020
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 195
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Tidskriftsartikel (refereegranskat)abstract
- The crystallization rate during selective laser melting (SLM) of bulk metallic glasses (BMG) is a critical factor in maintaining the material's amorphous structure. To increase the understanding of the interplay between the SLM process and the crystallization behavior of BMGs, a numerical model based on the classical nucleation theory has been developed that accounts for the rapid temperature changes associated with SLM. The model is applied to SLM of a Zr-based BMG and it is shown that the transient effects, accounted for by the model, reduce the nucleation rate by up to 15 orders of magnitude below the steady-state nucleation rate on cooling, resulting in less nuclei during the build process. The capability of the proposed modelling approach is demonstrated by comparing the resulting crystalline volume fraction to experimental findings. The agreement between model predictions and the experimental results clearly suggests that transient nucleation effects must be accounted for when considering the crystallization rate during SLM processing of BMGs.
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| 45. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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Bobbin and conventional friction stir welding of thick extruded AA6005-T6 profiles
- 2016
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Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 108, s. 114-125
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Tidskriftsartikel (refereegranskat)abstract
- Conventional and bobbin friction stir welding processes (FSW and BFSW, respectively) were employed for joining 10 mm thick extruded AA6005-T6 profiles. The FSW and BFSW techniques were employed using two sets of parameters resulting in slow and fast processes. In general, the bobbin tool enabled welding with faster welding speeds than the conventional FSW technique. A comprehensive in-situ thermal analysis was performed using thermocouples. It was evident that, in a like-for-like comparison, i.e., employing the same set of welding parameters, the BFSW technique introduces a somewhat higher peak temperature, however, lower heat input and, more importantly, a higher cooling rate than the conventional FSW. Accordingly, a somewhat finer microstructure was formed in the stir zone of the BFSW samples than in the FSW ones, resulting in higher hardness values, and slightly higher ultimate strengths in the BFSW samples.
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| 46. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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Microstructural characterization and formation of α' martensite phase in Ti-6Al-4V alloy butt joints produced by friction stir and gas tungsten arc welding processes
- 2013
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Ingår i: Materials and Design. - : Elsevier BV. - 0261-3069 .- 1873-4197 .- 0264-1275. ; 47, s. 143-150
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Tidskriftsartikel (refereegranskat)abstract
- The obtained microstructures of a Ti-6Al-4V alloy welded by Gas Tungsten Arc Welding (GTAW) and Friction Stir Welding (FSW) were investigated and evaluated quantitatively. In the GTAW method, the effect of current was examined so that the samples were subjected to various currents between 90 and 120. A. In the FSW process, samples were welded by different rotational speeds (450-850. rpm). Non-destructive tests including Visual and Radiography Tests (VT and RT) were used to identify defect-free samples. The microstructural studies by electron microscopes revealed formation of different phases in the weld area of the samples welded via mentioned methods. The recorded peak temperatures in the weld regions compared favorably with the expectations about the evolved microstructures. A bi-modal microstructure was just obtained in the FSWed sample with a peak temperature below β transus temperature (T<995°C). α' martensite phase, which is an acicular and strengthening phase in this alloy, was only observed in FSWed specimens.
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| 47. |
- Espinoza-Cuadra, J., et al.
(författare)
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Effect of Sr and solidification conditions on characteristics of intermetallic in Al–Si 319 industrial alloys
- 2010
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 31:1, s. 343-356
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Tidskriftsartikel (refereegranskat)abstract
- An experimental study was carried out to determine the effect of strontium (Sr) on the characteristic of intermetallic phases, particularly the Al5FeSi phase which present morphology of platelets or needle-like. The results showed that within the range of variables studied, the modification process caused the disappearance of the needles and only occur the precipitation of phase α (chinese script-like). Refinement of the intermetallic phases occurs in conjunction with the refinement in grain size. Both parameters depend strongly on local cooling rate (T), temperature gradient (G) and apparent rate of solidification front (V). In the case of equiaxed structures the refinement of grain size and intermetallic occurs with increasing local cooling rate and temperature gradient and decrease the apparent rate of solidification front. In the case of columnar structures, refinement of grains and intermetallic requires the increase in values of the three variables indicated. Moreover, the addition of Sr resulted in the modification of silicon eutectic, as noted in others research works.
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| 48. |
- Feng, Shuo, et al.
(författare)
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Predicting laser powder bed fusion defects through in-process monitoring data and machine learning
- 2022
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Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 222
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Tidskriftsartikel (refereegranskat)abstract
- Industry application of additive manufacturing demands strict in-process quality control procedures and high product quality. Feedback loop control is a reasonable solution and a necessary tool. This paper demonstrated our preliminary work on the laser powder-bed fusion feedback loop: predict local porosity through in-process monitoring images and machine learning. 3D models were rebuilt from in-situ optical tomography monitoring images and post-build X-ray CT images. They were registered to the original CAD. Dataset for machine learning was assembled from those registered 3D models. The trained machine learning model can precisely predict local porosity caused by lack of fusion and keyhole with multi-layer monitoring images. It also indicates the optimal processing window. It is impossible to be sure about the occurrence of defects in a layer based only on the abnormality of a single layer, and vice versa. Defects in a layer can be caused by improper parameters or anomalies in current layer or subsequent layers; defects in one layer can also be eliminated by proper parameters in the following layers. The work laid the basis for the next step feedback loop control of pore defect.
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| 49. |
- Fiegl, Tobias, et al.
(författare)
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Effect of AlSi10Mg0.4 long-term reused powder in PBF-LB/M on the mechanical properties
- 2021
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Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 212
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Tidskriftsartikel (refereegranskat)abstract
- Laser-based powder bed fusion (PBF-LB/M) is a well-established additive manufacturing (AM) process capable of producing high quality parts with excellent mechanical properties. Industrial applications of additively manufactured parts require the usage of fresh powder which makes the process expensive, especially in case of AM machines with enlarged build envelopes. Processing long-term reused powder fits to economic yields with the drawback of increased porosity and incorporated oxides. In this study, a detailed analysis of components made of virgin and long-term reused AlSi10Mg0.4 powder is provided. The experiments reveal that process parameters qualified for the virgin powder are not working offhand for the reused powder, as an increase of porosity from less than 1 % up to 3 % and a decline of tensile strength as well as yield strength of about 15 % are observed. The results indicate that powder degradation, which is based on the formation of hydroxides and oxides, has a significant impact on as-built microstructure as well as mechanical properties of additively manufactured parts. The amount of hydrogen and oxygen is measured for different powder conditions and the powder ageing process of AlSi10Mg0.4 is discussed in detail.
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| 50. |
- Fjellstedt, J., et al.
(författare)
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Experimental investigation and thermodynamic assessment of the Al-rich side of the Al-B system
- 2001
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Ingår i: Materials & design. - 0264-1275 .- 1873-4197. ; 22:6, s. 443-449
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Tidskriftsartikel (refereegranskat)abstract
- The phase relations in the Al-Ti-B system are of great importance for the manufacturing of Al/TiB2 composites. To describe the phase relations, the relations in the binaries Al-B, Ti-B and Al-Ti must be known. The description of the binary Al-B system has been found to be poor. The Al-rich side of the Al-B phase diagram was studied using DSC, on alloys ranging from 0.5 up to 6.4 at ·% B. The Al-rich part of the phase diagram was assessed using the experimental data and data found in the literature. The eutectic temperature was found to agree well with the literature. However, the peritectic temperature was found to be 914°C. Above the peritectic temperature a metastable primary precipitation of AlB2 below the AlB12 liquidus line was suggested. This type of degenerate peritectic reaction is similar to what has been found in Fe-based materials. This behaviour also explains the difficulty in the determination of the peritectic point by experimental means. © 2001 Elsevier Science Ltd. All rights reserved.
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