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81.
《Science & Technology of Welding & Joining》2013,18(2):176-186
AbstractThe objective of the present paper is to investigate the effect of including the tool probe in the numerical modelling of three-dimensional heat flow in friction stir welding (FSW). The heat flow close to the probe/matrix interface is investigated. In the models presented, the heat is forced to flow around the 'probe hole'. In this manner, the material flow through the probe region, which often characterises other thermal models of FSW, is avoided. This necessitates controlling the convective heat flow by prescribing the velocity field in the narrow shear layer at the tool/matrix interface. As a consequence the sliding, sticking, or partial sliding/sticking condition can be modelled. Six cases are established, which are represented by three stages of refinement of the heat source model, combined with two different contact conditions, i.e. full sliding and full sticking. 相似文献
82.
《Science & Technology of Welding & Joining》2013,18(2):184-191
AbstractThis paper describes an autocompleting friction welding method that was carried out to weld with an insert piece set between fixed base metals. The base metal was low carbon steel, and the faying surface of the fixed specimen had a 10 mm diameter. The effect of the thickness of the insert piece (insert thickness) on the joining phenomena was investigated. When the insert thickness was 3˙2 mm and the friction welding conditions were a friction speed of 27˙5 s–1 and friction pressure of 36 MPa, the insert piece had a shear fracture toward the circumferential direction in the peripheral portion of the weld interfaces by the initial peak produced during the friction process. The joint also had cracks at the adjacent region of the weld interfaces, although it had the same tensile strength as the base metal. On the other hand, the joint made using the insert piece with a groove on its peripheral portion had the same tensile strength as the base metal, where it fractured. This joint also had 90° bend ductility without cracks. In this case, the optimum insert thickness was 4˙0 mm, and the thickness at the bottom of the grooves (groove bottom thickness) was 1˙2 mm with an 11 mm inner groove diameter, and the friction welding conditions were a friction speed of 27˙5 s–1 and friction pressure of 36 MPa. In conclusion, a sound friction welded joint was made by an autocompleting friction welding method. 相似文献
83.
《金属精饰学会汇刊》2013,91(3):136-140
AbstractThis paper provides an overview on how plasma deposited coatings can significantly enhance the surface properties of metallic components. Two plasma processing technologies known as physical vapour deposition (PVD) and plasma enhanced chemical vapour deposition (PECVD) are introduced. Examples of the coatings deposited using these two processes are discussed. Among the coating application areas outlined are their use to increase the wear life of tools, to improve decorative finish and to enhance medical device biocompatibility. 相似文献
84.
《腐蚀工程科学与技术》2013,48(6):477-480
AbstractStress corrosion cracking (SCC) behaviour of a wrought magnesium alloy (AZ61) friction stir weldment was assessed in ASTM D1384 test solution at two strain rates. The analyses have shown that both the parent and the weldment are susceptible to SCC at a nominal strain rate of 10–6 s–1. Fractographic evidence clearly reveals the susceptibility, especially of the fine grained region of the friction stir weld nugget to SCC. The susceptibility to cracking has been observed to increase with decreasing strain rate and under this condition (10–7 s–1), the behaviour of the parent and the friction stir weldment were nearly the same. 相似文献
85.
《Materials Science & Technology》2013,29(2):191-196
AbstractInternal friction and shear modulus measurements were carried out in a Ti32Zr18Ni50 alloy to study the effect of martensitic transformation on hydrogenation properties. The temperatures of martensitic transformation and austenitic transformation weredetermined. The results were compared to those obtained by electrical resistivity and differential scanning calorimetry techniques. The experiments showed two peaks of internal friction, one associated withdislocation relaxations and the other with phase transformations. The microstructurecharacterisation was carried out by scanning electron microscopy. The phase (Ti, Zr)2Ni was found mainly precipitated in grain boundaries. Some experiments were carried out in specimens with previous plastic strain and another set of samples was tested in a hydrogen atmosphere.With increasing plastic strain, the amplitude of the peak associated with dislocations decreased. Hydrogen addition during the testsled to an increase in the temperature of maximum internal friction. 相似文献
86.
《Materials Science & Technology》2013,29(11):1336-1340
AbstractDamping behaviours of the open cell microcellular pure Al foams fabricated by sintering and dissolution process with the relative density of 0·31–0·42 and the pore size of 112–325 μm were investigated. The damping characterisation was conducted on a multifunction internal friction apparatus. The internal friction (IF) was measured at frequencies of 1·0, 3·0 and 6·0 Hz over the temperature range of 298–725 K. The measured IF shows that the open cell pure Al foam has a damping capacity that is enhanced in comparison with pure Al. At a lower temperature (~400 K), the IF of the open cell pure Al foams increases with decreasing relative density, with decreasing pore size and with increasing frequency. The IF peak was found at the temperature range of 433–593 K in the IF curves. It is clear that the IF peak is relaxational type and the activation energy associated with the IF peak is about 1·60 ± 0·02 eV. Defect effects can be used to interpret the damping mechanisms. 相似文献
87.
《Materials Science & Technology》2013,29(10):1243-1248
AbstractElectromagnetic stirring using multiple induction coils has been investigated as a method of preparing semisolid FC20 alloy. The effects of additions of titanium, zirconium, and boron on the microstructure of the FC20 alloy have also been studied. The electromagnetic flux density increased with input voltage and was higher at the wall of the container than near the centre of the coil. The microstructure of the alloys varied with cooling rate: the higher the cooling rate, the smaller the particle size and the greater the degree of sphericity. The additions of titanium, zirconium, and boron also improved the alloy microstructure. 相似文献
88.
《Materials Science & Technology》2013,29(11):1370-1376
AbstractA parametric study was carried out to evaluate the influence of friction stir processing (FSP) parameters (tool rotation speed and feed rate) on the superplasticity of the weld nugget. Dynamically recrystallised AA 2095 thin sheets with a fine grain size of 2 μm were welded using four feed rates and three rotational speeds. High temperature tensile testing was employed to understand the significance of the FSP parameters and to optimise the parameters for maximum elongation. The tool rotation speed was found to be the most decisive parameter for controlling superplastic behaviour. A strain rate sensitivity of 0·68 was measured for the highest rotational speed at the optimum superplastic forming (SPF) temperature of 495°C. A maximum percentage 'elongation to failure' of 550% was achieved for the sheets subjected to FSP at 1000 rev min?1 and 4·2 mm s?1, compared with 475% obtained for the base metal at the optimum SPF temperature and strain rate of 495°C and 10?3s?1, respectively. 相似文献
89.
《Tribology - Materials, Surfaces & Interfaces》2013,7(2):91-98
AbstractFor several years different types of nanoparticles have been considered and studied as potential friction modifying lubricant additives. Some nanoparticles can reduce the friction coefficient by 30–70%, depending on the base oil and the experimental conditions. In the present study, an experimental analysis on tribological properties of inorganic fullerene-like metal dichalcogenides was performed in comparison with MoS2 2H layered structures. Tribological tests were carried out on a pin on disc tribometer in ambient air. Several contact conditions are analysed in order to realise boundary and mixed lubrication regimes. The experimental study was performed on a mineral base oil, and particle concentration effects were analysed. Antifriction properties were evaluated by measuring the friction coefficient and are presented as generalised Stribeck diagrams. Inorganic fullerene-like WS2 and MoS2 nanoparticles present interesting friction reduction properties when tested in boundary and mixed lubrication. 相似文献
90.
J. D. Owen 《纺织学会志》2013,104(7):313-343
The bending behaviour of square plain-weave fabrics spun and woven from nineteen different fibres, each in a range of cover factors, has been studied. It is shown how this behaviour is determined by the mechanical properties of the fibre and the frictional and geometrical restraints within and between yams in the fabric. The effects on these restraints of cover factor and of relaxation in wet finishing and in heat-setting are examined. Factors affecting cloth stiffness are summarized, and it is shown that two quantities, an elastic component and a frictional component, are required to specify the bending behaviour with reasonable completeness. 相似文献