| 1. |
- Abdalla, Abdalla M., et al.
(författare)
-
Synthesis and characterization of Sm1-xZrxFe1-yMgyO3 (x, y = 0.5, 0.7, 0.9) as possible electrolytes for SOFCs
- 2018
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 765 KEM, s. 49-53
-
Konferensbidrag (refereegranskat)abstract
- The novel perovskite oxide series of Sm 1-x Zr x Fe 1-y Mg y O 3 (x,y = 0.5, 0.7, 0.9) were synthesized by solid state reaction method. X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and conductivity analysis were carried out. XRD patterns of sintered materials revealed the shifted Bragg reflection to higher angle for the higher content of Zr and Mg. This is related to the ionic size of the dopant elements. Rietveld refinement showed that all compounds crystallized in cubic space group of Fm-3m. SEM images showed that the grains were well defined with highly dense surfaces makes it potential as an electrolyte material in solid oxide fuel cells (SOFCs) or gases sensors. Impedance spectroscopy at 550-800 °C shows that conductivity is higher at higher temperature. Sm 0.5 Zr 0.5 Fe 0.5 Mg 0.5 O 3 shows the highest conductivity of 5.451 × 10 -3 S cm -1 at 800 °C. It was observed that 50% molar ratio of Mg and Zr doping performed highest conductivity.
|
|
| 2. |
|
|
| 3. |
- Ambrozinski, Lukasz, et al.
(författare)
-
Development of Lamb waves-based SHM systems
- 2012
-
Ingår i: Key Engineering Materials. - : Trans Tech Publications Inc.. - 1013-9826 .- 1662-9795. ; 518, s. 87-94
-
Tidskriftsartikel (refereegranskat)
|
|
| 4. |
- Andersson, Tobias, et al.
(författare)
-
3D-Simulation of Heat Flow in Indexable Drilling
- 2023
-
Ingår i: Key Engineering Materials. - : Scientific.Net. - 1013-9826 .- 1662-9795. ; 955, s. 53-62
-
Tidskriftsartikel (refereegranskat)abstract
- In machining, the heat flow into the workpiece during the cutting process is often a major concern. The temperature rise can lead to substantial residual stresses or elastic in-process deformations which may result in the dimensional tolerance requirements being violated. In the present study a modelling strategy is developed for determination of the heat load during indexable drilling. The heat load on the workpiece is determined from 3D thermomechanical Coupled Eulerian Lagrangian analyses of orthogonal turning for various chip thicknesses and cutting speeds. The determined heat load is then transferred to a 3D transient heat transfer analysis of the indexable drilling process for the determination of the temperature field. Thereby, this modelling technique avoids the complex cutting process that is performed in real cutting simulations and thereby reducing the computational complexity of the problem considerably. The simulated temperatures are compared with experimentally measured temperatures and some conclusions are drawn regarding the modelling approach.
|
|
| 5. |
- Antti, Marta-Lena, et al.
(författare)
-
Thermal expansion behaviour of high melting point oxides
- 1999
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 164-165, s. 279-282
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal expansion characteristics of the reinforcement and matrix constituents in ceramic composites have a strong influence on a number of aspects of the composite performance. Thus the toughness and strength of the composite can be influenced by local residual stresses due to the thermal expansion mismatch of different phases. Moreover, in individual polycrystalline phases, local stress variations from grain to grain, generated as a result of anisotropy of thermal expansion in combination with anisotropy of elasticity can influence strength and toughness in similar ways. In the present study, reported data on the thermal expansion coefficients of oxides having potential as constituents in high temperature composites are reviewed and complemented with additional measurements made using high temperature X-ray diffraction
|
|
| 6. |
- Ashkin, A., et al.
(författare)
-
Investigation of α-sialon formation by high temperature X-ray diffraction
- 1994
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 89-91, s. 373-380
-
Tidskriftsartikel (refereegranskat)abstract
- A technique for following sialon formation in situ by high temperature x-ray diffraction (HT-XRD) was developed. The composition chosen for study was an yttrium α-sialon with x = 0.4. Powder compacts containing silicon nitride, aluminum nitride and yttria powders were pre-sintered at 1350 °C and then studied by HT-XRD at temperatures between 1450 and 1580 °C and nitrogen pressures of 0.11 MPa. The furnace was made from graphite coated with porous silicon nitride/silicon carbide. The coating prevented silicon carbide formation in the sample up to 1600 °C. X-ray diffraction results show the formation of a Y10Al2Si3O18N4 phase at 1350 °C, which dissolved to form α-sialon and other phases at higher temperatures. The amounts of α-sialon formed are similar to the amounts reported by other authors. An empirical method was used for the calculation of activation energy for the silicon nitride to α-sialon transformation and resulted in a value of 330 kJ mol-1.
|
|
| 7. |
- Asp, Leif, et al.
(författare)
-
Delamination criticality in slender compression-loaded composite panels
- 2002
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 221-222, s. 3-16
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a damage tolerance model based on the assumption of delamination criticality in compression loaded slender composite panels is outlined. In particular, the verification of the model by comparison between numerical predictions and experimental results is reviewed. Growth of shallow delaminations in slender panels is shown to be promoted by the global buckling of the panel. Consequently, care must be taken if structures with delaminations are to be allowed to buckle. In the paper, application of the model for aircraft design is briefly discussed. The overall predicted panel behaviour agrees with observations for test coupons. However, very small geometrical changes are shown to have tremendous effects on the predicted behaviour. Consequently, in structural design one must consider the sensitivity of geometrical conditions on the predicted behaviour. Therefore, reduction of the structural item into a design element is suggested. To generate conservative designs the suggested design element is to represent the worst case
|
|
| 8. |
- Aydin, Gökçe, et al.
(författare)
-
Towards Laser Metal Deposition of Modified PH 13-8Mo Powder
- 2023
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 964, s. 85-90
-
Tidskriftsartikel (refereegranskat)abstract
- Modified PH 13-8Mo alloy exhibits a good combination of corrosion resistance and mechanical properties for demanding applications in aerospace, petrochemical, and tooling industries. Additive manufacturing, specifically the laser metal deposition process with powder as feedstock (LMDp), has the potential to be utilized in these industries. However, very limited knowledge on the LMDp of this alloy currently exists. The aim of this work was, therefore, to deposit a multi-track single layer of modified PH 13-8Mo alloy as a first step towards 3D geometries, and to analyze the resulting microstructure by using Optical Microscopy, Scanning Electron Microscopy, X-Ray Diffraction, Electron Backscatter Diffraction, and micro-hardness. It was found that the multitrack single layer was free from major defects. The microstructure was heterogeneous, and it consisted of a martensitic matrix and small amounts of δ ferrite, austenite, and AlN. The results of this research will be used to tailor the microstructure and properties of future 3D additively manufactured components.
|
|
| 9. |
|
|
| 10. |
- Bergström, L, et al.
(författare)
-
Interparticle forces and rheological properties of ceramic suspensions
- 1999
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 159-160, s. 119-126.
-
Tidskriftsartikel (refereegranskat)abstract
- Dispersants have a profound influence on the suspension properties of ceramic slurries. We will illustrate the effect of polymers and polyelectrolytes on the colloidal stability and the rheological properties in both aqueous and non-aqueous media. We have related direct measurements of polymerically induced interparticle forces to the rheological properties of different ceramic systems. Simple estimates of the effective volume fractions of non-aqueous, polymerically stabilized silicon nitride suspensions gave a reasonable correspondence between calculated and measured polymer layer thicknesses. We show that PAA stabilize zirconia by an electrosteric mechanism; also, we found an excellent agreement between the presence of bridging attraction and poor colloidal stability at low surface coverage. In addition, the van der Waals forces have been quantified by theoretical calculations and direct measurements.
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
- Botero, Carlos, et al.
(författare)
-
Functionally Graded Steels Obtained via Electron Beam Powder Bed Fusion
- 2023
-
Ingår i: Key Engineering Materials. - : Trans Tech Publications, Ltd.. - 1013-9826 .- 1662-9795. ; 964, s. 79-84
-
Tidskriftsartikel (refereegranskat)abstract
- Electron-Beam Powder Bed Fusion (EB-PBF) is one of the most important metal additive manufacturing (AM) technologies. In EB-PBF, a focused electron beam is used to melt metal powders in a layer by layer approach. In this investigation two pre-alloyed steel-based powders, stainless steel 316L and V4E, a tool steel developed by Uddeholm, were used to manufacture functionally graded materials. In the proposed approach two powders are loaded into the feeding container, V4E powder on top of 316L one, preventing their mixing. Such type of feeding yields components with two distinct materials separated by a zone with gradual transition from 316L to V4E. Microstructure and local mechanical properties were evaluated in the manufactured samples. Optical Microscopy, Scanning Electron Microscopy and EDX on the polished cross-sections show a gradual microstructural and compositional transition from characteristic 316L at the bottom of the specimens to the tool steel towards the top. Nanoindentation experiments confirmed a consequent gradient in hardness and elastic modulus, which gradually increase towards the top surface of the samples. The achieved results provide great possibilities to tailor the composition, microstructure, mechanical properties, and wear resistance by combining different powders in the powder bed AM technology. Potential applications include the tooling industry, where hard and wear-resistant materials are demanded on the surface with tougher and more ductile materials in the core of the tool.
|
|
| 14. |
|
|
| 15. |
- Broitman, Esteban, et al.
(författare)
-
Structural and Mechanical Properties of CNx and CPx Thin Solid Films
- 2012
-
Ingår i: Key Engineering Materials. - : Trans Tech Publications. - 1013-9826 .- 1662-9795. ; 488-489, s. 581-584
-
Tidskriftsartikel (refereegranskat)abstract
- The inherent resiliency, hardness and relatively low friction coefficient of the fullerene-like (FL) allotrope of carbon nitride (CNx) thin solid films give them potential in numerous tribological applications. In this work, we study the substitution of N with P to grow FL-CPx to achieve better cross- and inter-linking of the graphene planes, improving thus the materials mechanical and tribological properties. The CNx and CPx films have been synthesized by DC magnetron sputtering. HRTEM have shown the CPx films exhibit a short range ordered structure with FL characteristics for substrate temperature of 300 degrees C and for a phosphorus content of 10-15 at.%. These films show better mechanical properties in terms of hardness and resiliency compared to those of the FL-CNx films. The low water adsorption of the films is correlated to the theoretical prediction for low density of dangling bonds in both, CNx and CPx. First-principles calculations based on Density Functional Theory (DFT) were performed to provide additional insight on the structure and bonding in CNx, CPx and a-C compounds.
|
|
| 16. |
- Chen, YuHong, et al.
(författare)
-
Identification of Fe-containing phase in oxidation process of BOF slag
- 2017
-
Ingår i: Key Engineering Materials. - Zürich : Trans Tech Publications. - 1013-9826 .- 1662-9795. ; 726, s. 564-568
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the Fe-containing phases in BOF slag were identified before and after oxidized with atmospheric air. XRD and SEM with EDS results showed that The element Fe existed in slag in the form of calcium ferrite, wustite solid solution and hematite. Mg solid solute in wustite. After oxidized, magnetite became the major mineral phase in slag and Mg+ replace the Fe2+ of magnetite crystal to form spinel
|
|
| 17. |
- Diószegi, Attila, et al.
(författare)
-
Surface Turbulence at Flow of Gray Cast Iron
- 2011
-
Ingår i: Key Engineering Materials. - Switzerland : Trans Tech Publications. - 1013-9826 .- 1662-9795. ; 457, s. 422-427
-
Tidskriftsartikel (refereegranskat)abstract
- Gray cast iron has been investigated with respect to surface turbulence during mould filling. Different levels of flow velocities have been provoked in a vertically parted sand mould. The thermal resistant transparent front side of the mould permitted the observation of the flow pattern due to high speed camera registration. The registered frames including the liquid surface were investigated using image analyses. The results show good correlation between the average flow velocity and the liquid iron surface extension. Consequently it has been demonstrated that an increased absorption of hydrogen and nitrogen during mould filling is dependent on the level of liquid surface turbulence.
|
|
| 18. |
- Dragan, Krzysztof, et al.
(författare)
-
Remote monitoring of fatigue cracks growth in the aircraft structure based on active piezosensor network during the full scale fatigue test
- 2014
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 588, s. 249-256
-
Tidskriftsartikel (refereegranskat)abstract
- One of the major issues from a structural integrity point of view of the aircraft structure is an appropriate health monitoring technology delivery for the damage tolerant philosophy. This paper presents a development of a system for fatigue crack growth monitoring and early damage detection in the PZL 130 ORLIK TC II turbo-prop military trainer aft structure. The maintenance system of the aircraft shifts from the safe-life to the hard-time. The aircraft started Full Scale Fatigue Test (FSFT) which will continue up to 2013. In the article a built block approach for the system design, signal modeling, sensing and signal processing as well as damage detection is presented. Taking into the consideration a previous experience of AGH as well as AFIT, a network of PZT transducers was deployed in the aircraft structure hot-spots. The system components are: remote monitoring unit, signal analysis, graphical user interface, sensor self-diagnostic tools, and data classification model. Description of damage detection capabilities are delivered in the paper. In particular some issues concerning the proposed damage indices and its application to crack growth estimation models are discussed. Fishers Linear Discriminant is used as a method to obtain effective crack growth predictors and one of the self-diagnostic tools used in the system. The results of the data collected from specimen fatigue tests are delivered and cross-validation technique is used to evaluate a classification model based on the damage indices derived.
|
|
| 19. |
- Dworakowski, Ziemowit, et al.
(författare)
-
Application of artificial neural networks for damage indices classification with the use of Lamb waves for the aerospace structures
- 2014
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 588, s. 12-21
-
Tidskriftsartikel (refereegranskat)abstract
- Lamb waves (LW) are used for damage detection and health monitoring due to the long range propagation ability and sensitivity to structural integrity changes as well as their robustness in different applications. However, due to the dispersive character and multimode nature of LWs, analysis of the acquired ultrasonic signals is very complex. It becomes even more difficult when applied to a complex structure, for instance, an aircraft component with riveted joints and stringers characterized by difficult geometries. Therefore, numerous approaches to the evaluation of damage indices have been proposed in the literature. In this paper, comparison a number of damage indices applied to LWs testing in aircraft aluminum panels. The damage indices, known from the literature have been selected from the application point of view. Artificial neural network has been used for the classification of fatigue cracks and artificial damages induced in the specimens taken from a real aircraft structure. Article presents results of simulation, data analysis and data classification obtained using selected and dedicated neural network. The main aim of the presented research was to develop signal processing and signal classification methods for an aircraft health monitoring system. The article presents a part of the research carried out in the project named SYMOST.
|
|
| 20. |
- Elmquist, Lennart, et al.
(författare)
-
Influence of Primary Austenite on the Nucleation of Eutectic Cells
- 2011
-
Ingår i: Key Engineering Materials. - : Trans Tech Publications. - 1013-9826 .- 1662-9795. ; 457, s. 61-66
-
Tidskriftsartikel (refereegranskat)abstract
- The solidification of gray cast iron starts with the precipitation of primary austenite. This phase nucleates either as columnar or equiaxed dendrites depending on whether nucleation occurs on the mould wall or on particles and impurities in the melt. In this work, the nucleation of primary austenite and its influence on the eutectic solidification has been investigated using different amounts of iron powder as inoculants. Besides, the influence of different cooling rates was also examined. Within each austenite grain there is a microstructure, and this microstructure was investigated using a color etching technique to reveal the eutectic cells and the dendritic network. It is shown how the cooling rate affects the dendritic network and the secondary dendrite arm spacing, and how the microstructure can be related to the macrostructure through dendrite arm spacing. The secondary dendrite arm spacing is a quantification of the primary austenite belonging to the primary solidification, and it will be shown how the eutectic cell size is related to the secondary dendrite arm spacing. The total amount of oxygen influences the microstructural dimensions. This effect, on the other hand, is influenced by the cooling rate. The number of eutectic cells versus eutectic cell size show two distinct behaviors depending on whether being inoculated with iron powder or a mixture of iron powder and commercial inoculant. The addition of a commercial inoculant decreases eutectic cell size and increases the number of cells, while iron powder almost only changes cell size.
|
|
| 21. |
- Elmquist, Lennart, et al.
(författare)
-
On the Formation of Shrinkage Porosity in Gray Iron Castings
- 2011
-
Ingår i: Key Engineering Materials. - : Trans Tech Publications. - 1013-9826 .- 1662-9795. ; 457, s. 416-421
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of shrinkage porosity is a concern in the production of high-quality gray iron castings. In this work, a geometry known to generate this type of defect was used to investigate some of the parameters that influence its formation. The geometry is based on the presence of a migrating hot spot that at the end of the solidification is located close to the interface between the casting and the mold. The occurrence of shrinkage porosity at this position was investigated and the cavities examined using a scanning electron microscope equipped with EDS. It is believed that this type of defect is in contact with the atmosphere during solidification. The risk for shrinkage porosity decreases with increasing carbon content. The effect of high levels of molybdenum and phosphorus was investigated and shown to influence the defect formation. Inoculation is used to control the nucleation and the effect of high levels of inoculants was also examined. The microstructure was investigated by the use of a color etching technique, and the quantification considered eutectic cell size and secondary dendrite arm spacing. The quantification was done on the microstructure in the vicinity of defects as well as in areas without porosity.
|
|
| 22. |
|
|
| 23. |
- Falk, Lena, 1956
(författare)
-
SiAlON Microstructures
- 2009
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 403, s. 265-268
-
Tidskriftsartikel (refereegranskat)
|
|
| 24. |
|
|
| 25. |
- Gamstedt, E. Kristofer, et al.
(författare)
-
Fatigue dissipation and failure in unidirectional and angle-ply glass fibre/carbon fibre hybrid laminates
- 2002
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 221-2, s. 35-48
-
Tidskriftsartikel (refereegranskat)abstract
- The tensile fatigue behaviour of unidirectional 0degrees, [+/-10](4S) and [+/-45](4S) carbon fibre/glass fibre hybrid composite has been investigated. The dissipation was measured by the stiffness, hysteresis loss and temperature field of the specimen surface in an insulated testing chamber. The hysteresis loss correlates well with the increase temperature. Microscopic studies show frictional sliding of longitudinal crack faces between carbon and glass fibre bundles to be the main source of dissipation for on-axis specimens. With increasing off-axis angle the primary loss mechanism became cyclic shear deformation of the polymer matrix. With a finer dispersion of the constituents of the hybrid, the growth of these longitudinal cracks or of zones of inelastic matrix shear deformation. would be suppressed, which would result in a more fatigue resistant material. A localisation of heat generation sets in just prior to final failure. Damage and heat localisation lead to impending failure. If the parameters that control localisation were better understood, it would be possible to improve the fatigue resistance of the material by sensible microstructural design.
|
|
| 26. |
- Ghassemali, E., et al.
(författare)
-
Investigation of microstructure and hardness in microfoming of pure copper pins
- 2010
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 447-448, s. 381-385
-
Tidskriftsartikel (refereegranskat)abstract
- Microforming is defined as the process of production of metallic micro-parts with sub-millimeter dimension. There is as strong interaction between the scale of the microstructure and the size of the part affecting material flow, the so-called "size effect" in microforming processes. Conventional forming rules cannot be directly applied to the micro-scale forming. To better understand the implications for part geometry and properties, further investigation of the material flow related events is necessary. The aim of this work is to investigate microstructural evolution of pure copper during a micro-extrusion process - for production of micro-pins with diameters varying from 300 to 800Όm - by means of optical microscope (OM). Qualitative strain gradient distribution could be observed by those pictures. The results showed that change of micro-pins diameter and die angle affect the microstructure and strain distribution of the final product remarkably, that affect the mechanical properties of the pin formed. Furthermore, microhardness results were consistent with the microstructural observations. © (2010) Trans Tech Publications.
|
|
| 27. |
|
|
| 28. |
- Goh, C. S., et al.
(författare)
-
Magnesium and Aluminium carbon nanotube composites
- 2010
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 425, s. 245-261
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon nanotubes are one of the most exciting discoveries of nanosized materials in the 20th century. Challenges to create materials applicable for industrial applications involve both the incorporation of the carbon nanotubes into the material and to ensure that they do not agglomerate. Aluminium and magnesium based materials are among the metals that can benefit from the incorporation of carbon nanotubes. The fabrication of Aluminium carbon nanotube composites has challenges from reactivity and degradation of the carbon nanotube additions; hence the powder metallurgy route is preferred. Magnesium based materials on the other hand do not have this limitation and both the powder metallurgical route and the casting route are viable. Among the benefits of adding carbon nanotubes are increased yield strength and stiffness. Here is important that the effect is significant already at very low addition levels. This makes it possible to increase strength without having a significant detrimental effect on ductility. In fact, for magnesium alloys ductility can be improved due to the activation of additional slip planes improving the normally low ductility of HCP structure materials. © (2010) Trans Tech Publications.
|
|
| 29. |
|
|
| 30. |
|
|
| 31. |
- Joffe, Roberts
(författare)
-
Performance of non-crimp fabric composites in shear
- 2010
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 425, s. 45-59
-
Tidskriftsartikel (refereegranskat)abstract
- Experimental results of performance of non-crimp fabric composites are presented in this paper. In order to characterize in-plane shear properties of these composites, tensile and compression tests of [±452]S specimens were carried out. Two directions of loading are considered: warp (Shear warP: SP) and weft (Shear wefT: ST). This corresponds to laminates with the following lay-up: SP = [+45/-45/+45/-45]S; ST = [-45/+45/-45/+45]S. Although both types of laminates are cut from the same plate, mechanical performance in tension is rather different: laminate cut in weft direction exhibit higher shear modulus, shear strength and shear strain at failure than samples cut in warp direction. Fractography showed that different behavior of the materials is caused by much earlier damage initiation and accumulation in SP laminates. Analysis of images obtained from optical microscopy indicated that premature failure is most likely caused by stitches that prevent free rotation of bundles (shear deformation).
|
|
| 32. |
|
|
| 33. |
- Kao-Walter, Sharon, et al.
(författare)
-
A Finite Element Analysis of a Crack Penetrating or Deflecting into an Interface in a Thin Laminate
- 2006
-
Ingår i: Key Engineering Materials. - Switzerland : Trans. Tech. Publications. - 1013-9826 .- 1662-9795. ; 312, s. 173-178
-
Tidskriftsartikel (refereegranskat)abstract
- The crack tip driving force of a crack growing from a pre-crack that is perpendicular to and terminating at an interface between two materials is investigated using a linear fracture mechanics theory. The analysis is performed both for a crack penetrating the interface, growing straight ahead, and for a crack deflecting into the interface. The results from finite element calculations are compared with asymptotic solutions for infinitesimally small crack extensions. The solution is found to be accurate even for fairly large amounts of crack growth. Further, by comparing the crack tip driving force of the deflected crack with that of the penetrating crack, it is shown how to control the path of the crack by choosing the adhesion of the interface relative to the material toughness.
|
|
| 34. |
- Kono, Jun, 1987, et al.
(författare)
-
Factors for Eco-Efficiency Improvement of Thermal Insulation Materials
- 2016
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 678, s. 1-13
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal insulation material is an important component to reduce the environmental impact of buildings through the reduction of energy consumption in the operation phase. However, the material itself has embodied environmental impacts for the value it provides. Eco-efficiency is a method that quantifies relation between the environmental performance and the created value of a product system. This study investigated contributing factors of the eco-efficiency of thermal insulation materials to support decision making of material manufacturers. For the improvement of eco-efficiency, the assessment was made in two scopes: investigating the contributing factors of impact caused at production processes; and thermal performance through thermo-physical properties. For quantifying environmental impacts, cradle-to-grave life cycle assessment (LCA) of each materials were made. The life cycle impact assessment (LCIA) indicators used were ReCiPe H/A and global warming potential (GWP100a). For the assessment of production process, the inventories of the materials were assigned to six categories: heat, chemicals, electricity, transportation, raw materials and wastes. Among the assessed materials, contribution of electricity and heat within the production process was large for foam glass which had the highest potential to improve the eco-efficiency which was by factor 1.72. The analysis on relation between thermo-physical properties and eco-efficiency based on product data of the materials highlighted the importance of density as an indicator upon development and use. Although density often gains less attention, the finding suggested the effectiveness of improving the efficiency by having lower density without compensating the performance of the materials.
|
|
| 35. |
- Koptyug, Andrey, 1956-, et al.
(författare)
-
Triply Periodic Minimal Surfaces Manufactured by Electron Beam Powder Bed Fusion : Approaches and Challenges
- 2023
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 964, s. 91-96
-
Tidskriftsartikel (refereegranskat)abstract
- Sheet-based gyroids with different unit cell size, wall thickness, porosity gradients and manufacturing modalities were manufactured using electron beam- based powder bed fusion (E-PBF) using ‘melt’ and ‘wafer’ themes. Aim of the research is to understand the challenges of the designing, manufacturing and post-processing of such structures and their characteristic features.
|
|
| 36. |
- Kou, S.Q.
(författare)
-
Fracture systems caused by mechanical indentation in medium or hard rocks
- 1998
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 145-149, s. 941-946
-
Tidskriftsartikel (refereegranskat)abstract
- Fracture systems in brittle rocks induced by indentation are presented. These are based on numerous experimental results. Two models have been developed to account for the experimental observations and elucidate the failure mechanisms induced during indentation. One model concerns the indentation depth and the other describes the length of radial/median cracks remaining in the rock. Equations deduced from both models correlate well with experimental results in the laboratory. Modification of the equations makes it possible to take the fracture systems in the deep underground into consideration. The equations can serve for general use in many medium or hard rocks with different dimensions of indenters
|
|
| 37. |
- Laarz, E, et al.
(författare)
-
Aqueous silicon nitride suspensions: Effect of surface treatment on the rheological and electrokinetic properties
- 1997
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 132-136, s. 285-288
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of surface treatment on the colloidal stability and rheological properties of concentrated aqueous silicon nitride suspensions has been studied. Oxidized, leached and as-received, non-treated powders were studied using electroacoustic and rheological methods. At pH=10, the silicon nitride powder is well dispersed irrespective of surface treatment. However, the viscosity was affected by the surface treatment; oxidation caused a slightly higher and leaching a significantly lower viscosity. Several possible causes of the leaching effect on viscosity was discussed, e.g. leaching causing a smooth particle surface or facilitating break-up of strong, liquid immobilizing agglomerates. Additionally, the effect of added dispersants – anionic small molecules and polyelectrolytes – were also briefly mentioned.
|
|
| 38. |
- Li, Fengfu, et al.
(författare)
-
Corneal implantation with collagen-copolymer matrices
- 2005
-
Ingår i: Key Engineering Materials. - : Trans Tech Publications. - 1013-9826 .- 1662-9795. ; 288-289, s. 389-392
-
Tidskriftsartikel (refereegranskat)abstract
- A transparent matrix composed of collagen and poly(N, N-dimethylacrylamide-coacryloxysuccimide), 8mm in diameter and 350 mu m thick was implanted into pigs corneas using the lamellar keratoplasty (LKP) technique. No adverse immune or inflammatory reaction was observed during 4 month implantation period. Regenerated nerve filaments were observed in the subepithelial region and stroma by confacal microscopy. The endothelium of the operated eye was not touched by LKP and remained similar to that of the contra lateral (not operated) eye. The implant remained transparent over the four-month post-operative period, and clinical topography showed reconstitution of a smooth cornea surface. These preliminary results indicated that a new, functional cornea was re-established from the implanted biosynthetic matrix. This bio-synthetic matrix may have applications in other tissue engineering areas,, especially where innervation is important.
|
|
| 39. |
- Li, Lianchong, et al.
(författare)
-
Fracture Behavior in a Rock Pillar Subjected to Coupled Thermo-Mechanical Loading
- 2006
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 324/325, s. 443-446
-
Tidskriftsartikel (refereegranskat)abstract
- Using RFPA code, analyses have been carried out to investigate the stability of a rock pillar in a experiment for nuclear waste repositories, the numerically obtained stress field, temperature distribution, failure pattern of the pillar rock and associated AE events are all agree well with the in-situ data. Minor fracture initiation may take place in the vicinity of the boreholes after heating. Heating induces minor spalling at central pillar wall for 0.5 m sections below the tunnel floor, but the area of spalling is found to be limited. The core of the pillar remains intact for stress conditions corresponding to 120 days of heating which not only prove that the proposed technique provides a powerfully alternative and effective approach for the study on thermal-mechanical-damage coupling mechanism but also provide meaningful guides for the experiment design and associated applications.
|
|
| 40. |
- Li, Shuai, et al.
(författare)
-
A Polymer Complexing Route for Low Temperature Synthesis of Perovskite Lanthanum Aluminate Powder
- 2010
-
Ingår i: HIGH-PERFORMANCE CERAMICS VI. ; 434 - 435, s. 863-867
-
Konferensbidrag (refereegranskat)abstract
- Lanthanum aluminate powders were prepared via a polymer complexing method by using PEG as complexing agent. The LaAlO3 powder was characterized by XRD and SEM. The influence of processing parameters such as molar ratio of PEG monomers to metal cations (PEG:Men+) and aging process on the phase purity and powder morphology were investigated. The calcined powder with the PEG:Me ratio larger than 2:1 may contain the secondary phase, namely La2O3. The formation of phase pure LaAlO3 powder occurs when the PEG:Men+ ratio is 1:1 or enough gelation time is involved. Although the phase pure powder is obtained by this PEG method, all the single phase LaAlO3 powders are found to have seriously aggregated particles. The weakly agglomerated powder morphology is only found in the powders which contain La2O3.
|
|
| 41. |
- Lindgren, Lars-Erik, et al.
(författare)
-
Dislocation density based plasticity model coupled with precipitate model
- 2013
-
Ingår i: Advances in Engineering Plasticity XI. - : Trans Tech Publications. ; 535 - 536, s. 125-128
-
Konferensbidrag (refereegranskat)abstract
- A dislocation density based plasticity model is applied to two variants of steels. One is an austenitic (fcc) stainless steel with ordered precipitates and the other is a Ti-Nb microalloyed (bcc) steel. Precipitate distributions are measured and this information is combined with appropriate precipitate hardening models. The flow stress model is also calibrated for an nickel-based superalloy where it is combined with a model for precipitate growth.
|
|
| 42. |
- Liu, J., et al.
(författare)
-
Investigation of process parameters in superplastic forming of mechanical pre-formed sheet by FEM
- 2010
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 447-448, s. 437-441
-
Tidskriftsartikel (refereegranskat)abstract
- Conventional superplastic forming has been applied in automotive and aerospace industries for a few decades. Recently, superplastic forming combined with mechanical pre-forming process has been reported to be capable of forming non-superplastic AA5083 at 400°C to a surface expansion of 200 % [1]. In this paper, finite element modeling (FEM) was used to develop the combined forming process by using the non-superplastic material AA5083-O. The simulation follows the experimental sequence and was divided into two phases (mechanical pre-forming and superplastic forming). A conventional creep equation based on tensile test data was adopted as a material model for the simulation. The pressure cycle and forming time was simulated according to the actual process route. The thickness distributions obtained from simulation validated the capability of the model to be used for this case. The influence of different parameters, such as holder force, friction, and punch depth was investigated by comparing the final sheet thickness and level of material draw-in. It was found that the punch depth played a significant effect on the uniformity of thickness distribution, from which a more uniform formed part can be obtained by using the punch with higher depth during mechanical pre-forming phase. © (2010) Trans Tech Publications.
|
|
| 43. |
- Lundmark, P., et al.
(författare)
-
Modeling thermo-mechanical properties of damaged laminates
- 2003
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 251-252, s. 381-388
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a theoretical framework which allows us to determine the whole set of thermo-mechanical constants of the damaged laminates a function of crack density in different layers. In this approach closed form expressions are obtained which contains the ply properties, laminate lay-up and crack density as the input information. It is shown that the crack face opening and crack face sliding displacement normalized with respect to load are important parameters in these expressions affecting the level of properties degradation. They are determined in this paper using generalized plain strain FEM analysis results for non-interactive cracks. The methodology is validated and the possible error introduced by the non-interactive crack approach is estimated comparing with the 3-D FEM solution for cross-ply laminate with two systems of orthogonal cracks in plies. A limited number of experimental data are presented and used for further verification. [Material: GF/EP.]
|
|
| 44. |
- Makaraviciute, Asta, et al.
(författare)
-
A QCM-D Study of Reduced Antibody Fragments Immobilized on Planar Gold and Gold Nanoparticle Modified Sensor Surfaces
- 2014
-
Ingår i: Key Engineering Materials. - : Trans Tech Publications. - 1013-9826 .- 1662-9795. ; 605, s. 340-343
-
Tidskriftsartikel (refereegranskat)abstract
- An immunosensor is an analytical system consisting of specific immune system molecules coupled to a signal transducer. Immunosensor sensitivity depends on the type of immunorecognition ligands used, immobilization influence on their activity and orientation on the surface. Quartz crystal microbalance with dissipation (QCM-D) was employed to investigate the immobilization of antibodies against bovine leukemia virus antigen gp51 (gp51). Disulphide bridges of antibody hinge region were reduced chemically to yield two “half” antibody fragments (Frag-Ab), each having a single antigen binding site and free sulfhydryl groups that were used for immobilization. Frag-Ab were immobilized on planar gold and gold nanoparticle (AuNP) modified QCM-D sensor surfaces from initial solutions of different concentrations. Higher Frag-Ab surface density values were obtained on AuNP modified surfaces at all tested antibody concentrations. Frag-Ab/gp51 specific interaction was registered and it was determined that the highest sensitivity was exhibited by Frag-Ab immobilized at the lowest surface desities on both types of investigated surfaces. Specific gp51 interaction with Frag-Ab and non-specific binding to bovine serum albumin modified surfaces were
|
|
| 45. |
- Musalek, Radek, et al.
(författare)
-
Evaluation of failure micromechanisms of advanced thermal spray coatings by in-situ experiment
- 2014
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 606, s. 187-190
-
Tidskriftsartikel (refereegranskat)abstract
- Identification of failure mechanisms of thermal spray coatings by means of traditional fractography of failed parts is often troublesome. The reason for this is a highly inhomogeneous character of the coating microstructure and harsh in-service conditions which may obscure evidentiary fractographic marks. In this study, failure evolution of advanced thermal barrier coating (TBC) prepared by plasma spraying was studied in-situ at high magnification in a scanning electron microscope under well-defined laboratory conditions of three-point bending (3PB). © (2014) Trans Tech Publications, Switzerland.
|
|
| 46. |
- Nilsson, M., et al.
(författare)
-
A Critical Appraisal of the Interfacial Toughness of Ceramic Matrix Composites Using Indentation Techniques
- 1999
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 161-163:675-680, s. 675-680
-
Tidskriftsartikel (refereegranskat)abstract
- Advanced ceramic matrix composites provide a challenge for both manufacturer and user necessitating better techniques to critically appraise their properties. Interfacial toughness and the change of this property with application time at elevated temperature in hostile environments is of paramount importance for structural integrity/reliability of these materials. The present study investigates two such composite systems; a mullite matrix reinforced with silicon carbide fibres, and a novel oxide composite using sapphire fibres within an alumina-zirconia matrix. The interfacial toughness between the fibres and matrix was evaluated using nano- and micro-indentation fracture toughness methodologies. The results are interpreted in terms of recent theoretical interfacial fracture mechanics analysis by Hutchinson and Suo[1] for cracks approaching and extending along an interface. Nano-indentation has also been used to evaluate the intrinsic elastic/plastic properties of the CMC materials
|
|
| 47. |
|
|
| 48. |
- Pitchford, J. E., et al.
(författare)
-
The effect of particle migration on the creep-rate of nanocomposites
- 2006
-
Ingår i: Key Engineering Materials. - : Trans Tech Publications, Ltd.. - 1013-9826 .- 1662-9795. ; 317-318, s. 445-448
-
Tidskriftsartikel (refereegranskat)abstract
- The tensile creep behaviour of a mullite-SiC nanocomposite containing 5 vol% of SiC particles deformed under stresses from 4 to 50 MPa at 1400°C has been studied. After grain-size effects had been accounted for, the creep-rate of the nanocomposite was found to be approximately 30× less than that of the monolithic mullite. It is suggested that this reduction is caused not by a threshold stress but by the extra work required to drive diffusion in the low diffusivity SiC particles so that they can move with the grain boundaries during creep. A model is presented which predicts the rate of creep under these conditions and gives reasonable agreement with the experiments at low stresses.
|
|
| 49. |
|
|
| 50. |
- Selin, Martin, 1979-
(författare)
-
Using Regression Analysis to Optimize the Combination of Thermal Conductivity and Hardness in Compacted Graphite Iron
- 2010
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 457, s. 337-342
-
Tidskriftsartikel (refereegranskat)abstract
- In cast iron there is a contradictory relationship between thermal conductivity and strength. In many applications it is desirable to optimize the material properties to obtain both sufficiently high thermal conductivity and sufficiently high strength. The aim of this paper is to investigate how various microstructure parameters and alloying elements affect thermal conductivity and hardness in compacted graphite irons. It was found that the fraction of ferrite, the fraction of cementite, nodularity and content of carbon and silicon are parameters that influence the thermal conductivity and hardness the most. Based on these five key parameters linear regression equations were created for calculation of thermal conductivity and hardness. Ferrite and carbon have a positive influence on the thermal conductivity, while silicon, cementite and nodularity have a deleterious effect. All parameters except ferrite have a positive influence on the hardness. This is because the thermal conductivity is dependent on the movement of free electrons, and therefore unfavourable growth directions and grain boundaries which impede the electron movement will reduce the thermal conductivity. Ferrite has quite high thermal conductivity, while cementite has poor thermal conductivity, due to an unfavourable crystal structure. Nodular shaped graphite has a lower thermal conductivity than compacted graphite which explains the deleterious influence of nodularity. The soft ferrite phase will reduce the hardness value, while increasing the fraction of harder graphite nodules and harder cementite phase will increase the hardness. To investigate how these five parameters affect the combination of hardness and thermal conductivity, values for hardness and thermal conductivity were calculated for all combinations of key parameters in given intervals, using two linear regression equations. From these it is possible to predict the combination of parameters which gives a particular combination of hardness and thermal conductivity in compacted graphite iron.
|
|
