| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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
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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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| 5. |
- 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
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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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| 6. |
- 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
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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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| 7. |
- Davoodi, M.M., et al.
(författare)
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Concept selection of car bumper beam with developed hybrid bio-composite material
- 2011
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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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| 8. |
- 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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| 9. |
- 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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| 10. |
- Jomehzadeh, E., et al.
(författare)
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An analytical approach for stress analysis of functionally graded annular sector plates
- 2009
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Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275 .- 0261-3069. ; 30:9, s. 3679-3685
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, an exact analytical approach is used for bending analysis of functionally graded (FG) annular sector plates. The governing equilibrium equations are obtained based on the first order shear deformation plate theory. Introducing an analytical method, the coupled governing equilibrium equations are replaced by independent equations in term of transverse deflection and a new function. Using an equivalent flexural rigidity, the solutions of FG annular sector plates can be easily extracted from equation of homogeneous annular plates. Also, it is shown that the present method can provide accurate results. Finally, the effects of power of functionally graded material (FGM), plate thickness, inner to outer radius ratio and boundary conditions on the deflection and stresses of a functionally graded annular sector plate are studied.
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