| 1. |
- Afshari, Davood, et al.
(författare)
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On Residual Stresses in Resistance Spot-Welded Aluminum Alloy 6061-T6 : Experimental and Numerical Analysis
- 2013
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Ingår i: Journal of materials engineering and performance (Print). - : Springer Science and Business Media LLC. - 1059-9495 .- 1544-1024. ; 22:12, s. 3612-3619
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Tidskriftsartikel (refereegranskat)abstract
- In this study, an electro-thermal-structural-coupled finite element (FE) model and x-ray diffraction residual stress measurements have been utilized to analyze distribution of residual stresses in an aluminum alloy 6061-T6 resistance spot-welded joint with 2-mm-thickness sheet. Increasing the aluminum sheet thickness to more than 1 mm leads to creating difficulty in spot-welding process and increases the complexity of the FE model. The electrical and thermal contact conductances, as mandatory factors are applied in contact areas of electrode-workpiece and workpiece-workpiece to resolve the complexity of the FE model. The physical and mechanical properties of the material are defined as thermal dependent to improve the accuracy of the model. Furthermore, the electrodes are removed after the holding cycle using the birth-and-death elements method. The results have a good agreement with experimental data obtained from x-ray diffraction residual stress measurements. However, the highest internal tensile residual stress occurs in the center of the nugget zone and decreases toward nugget edge; surface residual stress increases toward the edge of the welding zone and afterward, the area decreases slightly.
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| 2. |
- Andersson, Daniel C., et al.
(författare)
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A Numerical Study of Material Parameter Sensitivity in the Production of Hard Metal Components Using Powder Compaction
- 2014
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Ingår i: Journal of materials engineering and performance (Print). - : Springer Science and Business Media LLC. - 1059-9495 .- 1544-1024. ; 23:6, s. 2199-2208
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Tidskriftsartikel (refereegranskat)abstract
- Modeling of hard metal powder inserts is analyzed based on a continuum mechanics approach. In particular, one commonly used cutting insert geometry is studied. For a given advanced constitutive description of the powder material, the material parameter space required to accurately model the mechanical behavior is determined. These findings are then compared with the corresponding parameter space that can possibly be determined from a combined numerical/experimental analysis of uniaxial die powder compaction utilizing inverse modeling. The analysis is pertinent to a particular WC/Co powder and the finite element method is used in the numerical investigations of the mechanical behavior of the cutting insert.
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| 3. |
- Fu, Qilin, et al.
(författare)
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Anti-vibration Engineering in Internal Turning Using a Carbon Nanocomposite Damping Coating Produced by PECVD Process
- 2014
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Ingår i: Journal of materials engineering and performance (Print). - : Springer-Verlag New York. - 1059-9495 .- 1544-1024. ; 23:2, s. 506-517
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Tidskriftsartikel (refereegranskat)abstract
- Machining dynamic stability has been enhanced through a damping coating based on a novel carbon-based nanocomposite material. The coating was synthesized using a plasma enhanced chemical vapor deposition method, and deposited on to the round-shank boring bar used for internal turning and tested during machining. Comparisons between an uncoated and a coated boring bar were carried out at 0.25 mm and 0.5 mm depth of cut using a five times length to diameter ratio overhang, which are typical conditions known to generate detrimental mechanical vibrations. From sound pressure measurement it was found that the measured absolute sound level during process could be reduced by about 90% when using the tool coated with damping layer. Surface roughness measurements of the processed workpiece showed decreased Ra values from approximately 3-6 mu m to less than 2 mu m (and in 50% of the cases < 1 mu m) when comparing an uncoated standard tool with its coated counterpart. Moreover, it was found that the addition of an anti-vibration coating did not adversely affect other tool properties, such as rigidity and modularity.
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| 4. |
- Ivanov, Dmitry, et al.
(författare)
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Simulation of Stress and Strain for Induction-Hardening Applications
- 2013
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Ingår i: Journal of materials engineering and performance (Print). - : Springer Science and Business Media LLC. - 1059-9495 .- 1544-1024. ; 22:11, s. 3258-3268
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Tidskriftsartikel (refereegranskat)abstract
- The possibility to manage stress and strain in hardened parts might be beneficial for a number of induction-hardening applications. The most important of these benefits are the improvement of fatigue strength, avoidance of cracks, and minimization of distortion. An appropriate and powerful way to take the stress and strain into account during the development of a process is to make use of computer simulations. In-house developed and commercial software packages have been coupled to incorporate the electromagnetic task into the calculations. The simulations have been performed followed by analysis of the results. The influences of two different values of quenching intensity, strength of initial material structure, strength of austenite, surface power density-frequency-time combination, and workpiece diameter on the residual stress are studied. The influence of quenching intensity is confirmed by the series of experiments representing the external hardening of a cylinder with eight variations of quenching intensity. Measured by x-rays, the values of surface tangential stress are used as a dataset for verification of the model being used for analyses.
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| 5. |
- Kahl, S., et al.
(författare)
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Composite Aluminum-Copper Sheet Material by Friction Stir Welding and Cold Rolling
- 2013
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Ingår i: Journal of materials engineering and performance (Print). - : ASM International. - 1059-9495 .- 1544-1024. ; 22:8, s. 2176-2184
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Tidskriftsartikel (refereegranskat)abstract
- An aluminum alloy and a pure copper material were butt-joined by friction stir welding and subsequently cold rolled. The cold-rolling operation proved to be very advantageous because small voids present after friction stir welding were closed, the interface area per material thickness was enlarged, a thin intermetallic layer was partitioned, and the joint was strengthened by strain hardening. Tensile test specimens fractured in the heat-affected zone in the aluminum material; tensile strengths of the joints exceeded the tensile strengths of the base materials and were as high as 335 MPa. During soft annealing of the composite material, a 6-8-μm-thick intermetallic layer was grown at the interface. Nevertheless, tensile fracture still occurred in the heat-affected zone of the aluminum material. Electrical resistivity of the joint was smaller than resistivity of the aluminum material. Production of such composite material would result in coiled sheet material that could be subjected to further treatments such as electroplating and forming operations in an efficient and economically viable manner. The new composite material is promising for emerging automotive and industrial electrical applications.
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| 6. |
- Kroupa, Ales, et al.
(författare)
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Current problems and possible solutions in high-temperature lead-free soldering
- 2012
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Ingår i: Journal of materials engineering and performance (Print). - : Springer Science and Business Media LLC. - 1059-9495 .- 1544-1024. ; 21:5, s. 629-637
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Tidskriftsartikel (refereegranskat)abstract
- The substitution of lead in the electronics industry is one of the key issues in the current drive towards ecological manufacturing. Legislation has already banned the use of lead in solders for mainstream applications (T M≈220 °C), but the use of lead in the solders for high-temperature applications (>85% lead, T M≈250-350 °C) is still exempt in RoHS2. The search for proper substitutes has been ongoing among solder manufacturers only for a decade without finding a viable low cost alternative and is the subject of intensive research. This article tries to map the current situation in the field of high-temperature lead-free soldering, presenting a short review of current legislation, requirements for substitute alloys, and finally it describes some existing solutions both in the field of promising new materials and new technologies. Currently, there is no drop-in replacement for lead-containing solders and therefore both the new materials and the new technologies may be viable solutions for production of reliable lead-free joints for high-temperature applications.
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| 7. |
- Olupot, Peter Wilberforce, et al.
(författare)
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Study of Glazes and Their Effects on Properties of Triaxial Electrical Porcelains from Ugandan Minerals
- 2010
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Ingår i: Journal of materials engineering and performance (Print). - : Springer Science and Business Media LLC. - 1059-9495 .- 1544-1024. ; 19:8, s. 1133-1142
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Tidskriftsartikel (refereegranskat)abstract
- Kaolin, ball clay, feldspar, and sand were collected from deposits in Uganda, milled and sieved to particle sizes of 45, 45, 53, and 25 μm, respectively. Three porcelain bodies and five glazes were formulated from them. The glazes were applied on porcelain specimens and subsequently evaluated for their effects on properties of porcelain samples. The formulated specimens were investigated using dilatometry, Steger test, FEG-SEM, XRD, 4-point bending, dielectric strength, and fracture toughness tests. A porcelain specimen consisting of 68% SiO2, 19% Al2O3, 4.7% K2O, and a glaze RO:0.57Al2O3:4.86SiO2 exhibited MOR of 105 MPa with Weibull modulus of 5.6 and a dielectric strength of 18 kV/mm upon firing at a heating rate of 6 °C/min to 1250 °C and holding for 2 h. The microstructure of the high-strength specimen exhibited round mullite needles, quartz, and glass. Holding samples for 2 h at peak temperature resulted in a 22% increase in MOR compared to 1 h holding. Glazing further improved strength by 67% for the best sample. Compressive stresses in glaze contributed to the strengthening effect. The dielectric and mechanical strength values obtained qualify the formulated sample for application in electrical insulation.
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