Papers by Keyword: Adiabatic Shear Band (ASB)

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Authors: Xin Long Dong, Lai Ze Li, Ying Qian Fu, Feng Hua Zhou
Abstract: The adiabatic shear bands (ASB) of the thick-walled cylinder have been studied by many researchers in the recent years. The onset and evolutions of the multiple shear failure of metal cylinder under explosive loadings are affected by many factors such as the characteristics of the impulsive loadings, the dynamic behavior of the materials, etc. In this work, a tube compression driven by electro-magnetic forces is introduced, which enables to carry out the experiments of the spontaneous evolution of multiple adiabatic shear bands in metal tube. The FEM simulation was conducted to investigate the evolution process of strain localization with coupled thermo-mechanical analysis. The FEM results show that ASB initiates when the stress drops rapidly and strain growth and not when it reaches the maximum shear stress. Once the shear band is formed, elastic unloading occurs beside the shear band. The different behaviors of the damage introduced in the strain softening model affect the initial nucleation strain and the distribution of ASBs. With the increase of material damage softening, the initial strain of shear band decreases and the number of shear bands increases.
Authors: Ji Lin Yu, Xin Long Dong, Jiang Yue Zhang
Authors: Li Ma, Yang Hu, Jian Xin, Gui De Deng
Abstract: Adiabatic shear band (ASB) is a typical response of materials under high strain rate loading. Based on the instability analysis of the thermo-viscoplastic constitutive model, a new rate-dependent failure criteria is proposed, which links dynamical evolution of ASB with macro mechanical critical conditions, and is successfully applied to account for the shear fracture mode of cylindrical structures subjected to explosive loading. Using finite element method, the transient failure procedure and shearing fragments induced by ASB is simulated, and the calculated fracture profile shows a good agreement with the experimental results. The failure analysis indicates that the rate-dependent failure criteria, as well as impulsive loading, govern the shear damage mode of the structures.
Authors: J.F.C. Lins, Hugo Ricardo Zschommler Sandim, K.S. Vecchio, Dierk Raabe
Abstract: We report the results of the microstructural characterization of a Ti-bearing IF-steel deformed at high strain rates (» 6.104 s-1) in a split Hopkinson bar. The shock-loading tests were performed in hat-shaped specimens to induce the formation of adiabatic shear bands (ASB). The samples were deformed at 223 K and 298 K. High-resolution electron backscatter diffraction (EBSD) reveals the development of an ultrafine-grained structure within the ASB. A closer inspection reveals the presence of deformation twins in grains adjacent to the shear band. These twins bend towards the ASB suggesting that mechanical twinning occurs before the flow associated to shear banding. The results of microtexture have indicated the presence of a sharp <111> g-fiber texture in the ASB for both temperatures.
Authors: Chun Zheng Duan, Zhao Xi Wang, Min Jie Wang, Wei Sen Kong
Abstract: The component distribution of adiabatic shear banding during high speed cutting(HSC) is important to understand the phase transformation during formation of adiabatic shear band and mechanism of serrated chip formation. This paper analyzed element distribution inside and near the adiabatic shear bands formed during HSC of 30CrNi3MoV high strength steel using electronic probe. It was found that there is no obvious element segregation, but carbon element tends to gather towards adiabatic shear band’s boundaries. The density of carbon inside the shear bands tends to increase with the increase of cutting speed. The results indicated that the diffusion and gather of carbon may occur during formation of adiabatic shear band. The diffusion mechanism may be short-range diffusion driven by high-speed deformation and high temperature rise.
Authors: Qing Wen Ding, Yu Ren, Cheng Wen Tan, Jing Zhang, Xiao Dong Yu
Abstract: A Split Hopkinson Pressure Bar system was employed to investigate the compressive dynamic mechanical behaviors of Ti-10V-2Fe-3Al (Ti-1023) alloy with lamellar microstructure, over a broad strain rates ranging from 1500/s to 5100/s. The results reveal that the strain rate has a significant effect on the flow stress of Ti-1023 alloy, and there exists serious thermal softening as the strain rate exceeds 3200/s. The critical strain rate of fracture for this alloy is 2300/s. The microstructure examination indicated that adiabatic shear bands (ASBs) bifurcate more intensely with the increasing of strain rate. Micro-voids nucleate either in the ASB or interface between shear band and matrix bulk. Finally, fracture of this alloy proceeds through the nucleation, growth and coalescence of these voids and cracks along the ASBs.
Authors: Xin Xu, Lin Wang, Deng Hui Zhao, Wen Wen Du
Abstract: In this paper, the shock phase transformation of β phase in Ti-5Al-5Mo-5V-3Cr-0.5Fe (Ti-5553) was investigated. Split Hopkinson Pressure Bar (SHPB) and light gas gun were employed to investigate the dynamic properties under high strain rates from 1000s-1 to 3500s-1. Microstructure characterization was carried out by optical microscopy (OM), scanning electronic microscopy (SEM) and transmission electron microscope (TEM). The experimental results demonstrate that the Ti-5553 alloy with β phase exhibit no obvious strain rate hardening effect with the high strain rate from 1000s-1 to 3000s-1. However, compared with the quasi-static compression test results (10-3s-1), this alloy shows an evident strain rate hardening effect, with the yield strength significantly improved. Second time loading indicates light gas gun dynamic tensile loading and then SHPB dynamic compression loading in Ti-5553 alloy with β phase. The results show that the shock-induced β to αʺ martensite phase transformation dramatically influences the postshock mechanical properties of these alloys. The yield strength of this alloy decreased after the shock wave effect of light gas gun, its ductility increasing. Higher shock pressures yielded an increased dislocation density and a gradual increase in the yield strength. Adiabatic shear band (ASB) exists in second time loading Ti-5553 alloy under 103s-1 strain rate. SHPB loaded the alloy: The results show that the Ti5553 alloy with β phase is adiabatic shear failure in high strain rate (3000s-1).
Authors: Y.G. Ko, Y.G. Kim, S. Namgung, Dong Hyuk Shin, Sung Hak Lee
Abstract: In this study, dynamic deformation behavior of submicrocrystalline aluminum alloy was established with respect to equal-channel angular (ECA) pressing routes such as A, B, and C. After 8-pass ECA pressings, the deformed samples, regardless of the routes applied, were consisted of ultrafine grains together with high dislocation density near the boundaries. Microstructural observation revealed that the sample deformed via route B showed more diffused diffraction pattern than those deformed via route A and C, suggesting the fact that route B was most effective for a rapid evolution in the grain boundary orientation from low-angle to high-angle characteristics. In the torsion tests, the shear stress decreased once reaching the maximum point. This maximum was the highest in the sample deformed via route B, and decreased in the order of the route C and route A. The dynamic deformation was explained based on microstructural uniformity associated with ECA pressing routes.
Authors: Jiang Hua Deng, Chao Tang, Yan Ran Zhan, Xing Ying Jiang
Abstract: In order to solve the problem of rivet head tending to crack in riveting, the effect of die forms on TA1 rivet deformation and microstructure was investigated by experimental method from macro and micro aspects in electromagnetic riveting. The results show that rivet material axial and radial flow can be controlled using different die forms, and thus the distribution of adiabatic shear band and grains in two sides of that in formed rivet head can be changed. With flat head die, severe axial and radial flows result in the nonuniform deformation and crack is prone to produced in rivet head. The adiabatic shear band of rivet head is obvious and grains in both sides of that deform severely. Material radial flows of rivet head are well constrained by spherical and 400 head die. The deformations are relatively uniform and the adiabatic shear bands are not obvious. It is an effective way to avoid crack formation and improve riveting quality using different die forms.
Authors: Tong You Cao
Abstract: Four different heat treatment routes which were called step quenching were taken and accordingly different morphology dual-phase samples have been obtained. It is found that Maximum shear stress increases with martensite volume increases. They have the following relationship: Maximum shear stress = 1.14(MVF)2 – 90.7(MVF) + 24266 MPa. Adiabatic shear bands and cracks led by them are important signs during the dynamic torsional tests
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