Papers by Keyword: Residual Stress

Abstract: In this paper, the distribution law of residual stress normal to the welding joint in LY12 aluminum alloy was measured by the combination use of hole drilling and electrical-measurement method. The experimental results indicated that it was an effective way to measure the residual stress of LY12 aluminum alloy with thickness of 6 mm by applying hole drilling. The distribution of residual stress vertical to welding joint is quite obvious. The residual stress increases as the distance away from the welding joint decreases. The value of the longitudinal residual stress is higher than that of the transverse residual stress. But they are all smaller than the value of ultimate stress in LY12 aluminum alloy. The heat treatment after welding can greatly improve the tensile strength of the weldment.

Abstract: This article deals with influence of the milling cutter tool’s geometry on tension in surface layer of workpiece. It describes, whether the tool brings the residual stress into the surface and its measurement by the magnetoelastic method based on the Barkhausen noise principle. The correct choice of the tool and cutting parameters has significant influence on surface layer of the component and extends so its lifetime and dependability. In this way we try to comply with permanent growing on the machine component.

Abstract: Weld distortion and residual stresses are two major issues in the fabrication process. Numerical techniques are being tried out to accurately predict the structural integrity of the welding. Interpass time in the multipass welding is an important parameter which influences the weld distortion and residual stresses. In this study two pass tungsten inert gas (TIG) welding of 6 mm mild steel plates has been analyzed using Finite element analysis (FEA) software Sysweld and parametric study is conducted with different interpass time. The temperature distribution, distortion and residual stresses are calculated using three dimensional finite element model (FEM) considering phase transformations in the material. The transient thermo-metallurgical analysis followed by elasto-plastic analysis is carried out using temperature dependent and phase dependent material properties. The material deposition in the multipass welding is numerically simulated using chewing gum method, where dummy phase and dummy material are assigned for the element activation. The phase proportions are calculated by assigning suitable phase kinetics parameter extracted from continuous cooling transformation (CCT) diagram of a given material. Experiments are conducted for validation after given edge preparation and using same material as filler wire. The FEM analysis is carried out for eight cases with different time interval between passes, starting from 30 s to 240 s in the steps of 30 s. FEM results are verified with experimentally measured values. It is found that the time interval between passes has less influence on the residual stresses but significantly affects the distortion and phase proportion due to the first pass preheating effect on second pass and second pass postheating effect on first pass.

Abstract: Two groups of 304 stainless steel samples different in thickness were prepared by Laser Prototyping, one of which was treated by high-frequency micro-forging. The residual stress on the sample surface was measured by strip cutting method. The results showed that the surface residual stress of the samples was tensile stress, which increased with thickness, and the residual stress began to drop while the thickness of samples arrived at a certain value. Therefore high-frequency micro-forging could regulate the surface residual stress state of the samples. Specifically, micro-forging could transform the tensile stress into compressive stress, which rose with the increase in thickness of samples and tended to be stable afterwards.

Abstract: Study on Stress-strain model of metallic materials with residual stress. First of all, Stress-strain model of metallic materials with residual stress was analyzed, then, derivation of a stress-strain model was done. Finally, according to the model of stress and strain analysis and derivation of results, taking diaphragm spring as an example, using methods of derivation of kinds of material obtained from this model portfolio, using finite element modeling tools, calculate the relationship between load and deformation. The test result indicated that, using the method of many kinds of material model combination can get the higher precision of calculation.

Abstract: To meet different electrical or optical functionalities, thin films are often of multiple layers processed at high temperatures. Substantial residual stresses can therefore develop in such thin film systems due to the disparate thermal properties of the individual material layers. High stresses can lead to mechanical failure of the systems and thus understanding the residual stresses in thin film systems is important. This paper presents a systematic way to characterize the residual stresses in epitaxial, polycrystalline and amorphous layers by using X-ray diffraction (XRD) techniques. The single-point XRD pattern renders the stresses of crystalline layers and the scanning XRD gives the curvature of the whole film. Based on the newly-developed analytical model, the residual stresses of each layer can all be determined.

Abstract: In order to reveal the adjustment principle of prestressed cutting on the residual stress of hardened bearing steel GCr15, a three-dimensional thermal elastic-viscoplastic finite element model was developed using an Arbitrary Lagrangian Eulerian (ALE) formulation. Several key simulation techniques including the material constitutive model, constitutive damage law and contact with friction were discussed, simulation of chip formation during prestressed cutting was successfully conducted. At the prestresses of 0 MPa, 341 MPa and 568 MPa, distributions of residual stress on machined surface were simulated and experimentally verified. The results indicated that residual compressive stress on machined surface were achieved and actively adjusted by utilizing the prestressed cutting method; meanwhile, within the elastic limit of bearing steel material, the higher applied prestress leads to the more prominent compressive residual stress in the surface layer and subsequently the higher fatigue resistance of the part.

Abstract: In this paper, plasma transfer arc welding using hard faced material Colmonoy which is deposited on a annular groove of a circular grid plate made up of SS 304 was studied. Hard face deposition made by Plasma Transferred Arc Welding (PTAW) on a annular groove of a grid plate at relatively high temperature, generates residual stresses due to differential shrinkage of the molten deposit, process-induced thermal gradients and difference in coefficients of thermal expansion between the colmonoy deposit and base material SS 304. However, the magnitude and distribution of the residual stresses vary depending on the heat input, deposition process, and the geometry of the component. Finite element analysis of residual stress is performed with commercial FEA package of ANSYS 12.0 which includes moving heat source, material deposit, temperature dependent material properties, metal plasticity and elasticity. Coupled thermo-mechanical analysis is done for welding simulation and the element birth and death technique is employed for simulation of filler metal deposition. Finally residual stress is evaluated so that annealing is performed accordingly to relieve residual stresses in order to carry out fracture analyses thereafter.

Abstract: We have researched the residual stress in super-smooth glass ceramics using nano-indentation technology, according to the characteristic that the residual stress in the process of pressure is sensitive to the pileup around the indenter, we can determine the changing area, then combine this with the elasto-plastic contact theory, thus the residual stress calculation formula is obtained. By the continuous strain obtained by a spherical indenter and the research on the yield stress and stress-strain curves of microcrystalline glass through spherical indentation experiments, we can get the rule which can tell us how the residual stress of the microcrystalline glass changes with the depth from surface. This research helps to improve the processing quality as well as the performance of the super-smooth surfaced microcrystalline glass, obviously it has a wide application prospect.

Abstract: Through study on the regulation of tensile strength and reduction of area after artificial aging and natural aging for SWRH82B wire rod, indicate that the tensile strength of wire rod unchanged through artificial aging or natural aging treatment while the reduction of area changes significantly the reduction of area is effected by aging temperature and aging time. Reduce the residual stress in the wire rod and lattice distortion is the main reason for reduction of area improving the composite brittle inclusions in the wire rod are not good for the rod plastic recovery.