Showing papers on "Shear band published in 1975"
TL;DR: In this paper, the authors investigated the hypothesis that localization of deformation into a shear band may be considered a result of an instability in the constitutive description of homogeneous deformation.
Abstract: T his paper investigates the hypothesis that localization of deformation into a shear band may be considered a result of an instability in the constitutive description of homogeneous deformation. General conditions for a bifurcation, corresponding to the localization of deformation into a planar band, are derived. Although the analysis is general and applications to other localization phenomena are noted, the constitutive relations which are examined in application of the criterion for localization are intended to model the behavior of brittle rock masses under compressive principal stresses. These relations are strongly pressure-sensitive since inelasticity results from frictional sliding on an array of fissures; the resulting inelastic response is dilatant, owing to uplift in sliding at asperities and to local tensile cracking from fissure tips. The appropriate constitutive descriptions involve non-normality of plastic strain increments to the yield hyper-surface. Also, it is argued that the subsequent yield surfaces will develop a vertex-like structure. Both of these features are shown to be destabilizing and to strongly influence the resulting predictions for localization by comparison to predictions based on classical plasticity idealizations, involving normality and smooth yield surfaces. These results seem widely applicable to discussions of the inception of rupture as a constitutive instability.
2,411 citations
TL;DR: In this article, a tensile deformation of polystyrene was carried out under pressure up to 4 kbar and the authors showed that the pressure-transmitting fluid (silicon oil) acts as a stress crazing and cracking agent.
Abstract: Tensile deformation of polystyrene carried out under pressure up to 4 kbar has shown that the pressure-transmitting fluid (silicon oil) acts as a stress crazing and cracking agent. Unsealed specimens showed a brittle-to-ductile transition at 2.95 kbar, while specimens sealed with Teflon tape and rubber showed the same transition at only 0.35 kbar. Analysis of the stress-strain curves for the sealed specimens indicated that the pressure dependency of the craze initiation stress differs from that of shear band initiation stress. The brittle-to-ductile transition occurs when the initiation stresses of both processes become equal. The principal stress for craze initiation showed almost no pressure dependency, suggesting that crazes initiate when the principal stress level of the tensile specimen reaches a critical value irrespective of the applied hydrostatic pressure. Similarly, no pressure dependency was observed for the principal ductile fracture stress. The pressure dependency of yield stress agreed well with a non-linear pressure dependent von Mises yield criterion.
60 citations
TL;DR: In this paper, tensile and compression tests have been carried out over a range of temperatures between 78 and 360 K to determine the micromechanisms of deformation and the mode of fracture.
Abstract: Tensile and compression tests have been carried out over a range of temperatures between 78 and 360 K to determine the micromechanisms of deformation and the mode of fracture. In compression, deformation occurred by shear band propagation whereas, in tension, deformation was restricted to crazing followed by fracture. Anomalously low crazing stresses were observed for tests on specimens immersed in liquid nitrogen. Analysis of the mechanism of fracture confirmed previous work relating crazing and fracture and the fracture model has been modified slightly to take account of additional features observed in failure of crazes at high temperatures.
31 citations
TL;DR: In this article, a nonlinear pressure-dependent von Mises criterion and the enthalpy energy density concept were combined to predict the pressure dependence of Young's modulus, and the onset of the shear banding was proved to relate to the energy density stored in the specimen.
Abstract: Tensile deformation of poly(methyl methacrylate) carried out under hydrostatic pressures up to 4 kbar has shown that the pressure-transmitting fluid (silicone oil) strongly affects the mechanical properties of this polymer. Unsealed specimens fractured in a brittle manner at almost the same strain of 5% in the whole pressure range examined, while specimens sealed with Teflon tape and rubber showed a brittle to ductile transition at only 0.25 kbar. At this pressure, the craze initiation and shear band initiation stresses were found to become equal. The pressure dependence of the shear band initiation stress could be expressed well with a “nonlinear” pressure-dependent von Mises criterion and the onset of the shear banding was proved to relate to the enthalpy energy density stored in the specimen. The combination of the nonlinear pressure-dependent von Mises criterion and the enthaply energy density concept enabled us to predict the pressure dependence of Young's modulus.
29 citations
01 Jul 1975
TL;DR: In this article, a fracture criterion was proposed to predict the occurrence of cracks in metal-working processes based on the formation of a shear band between large voids, and the fracture strain was estimated for a material by applying the McClintock analysis to small void coalescence.
Abstract: : The objective of this investigation was to develop a fracture criterion applicable to the prediction of the occurrence of cracks in metal-working processes. A model for large void growth was proposed, and the deformation mode was calculated by the elastic-plastic finite-element method. The results of the calculation showed the formation of a shear band between large voids. The proposed fracture criterion is that the growth and coalescence of small voids along this shear band is the final process of fracturing. The fracture strain was estimated for a material by applying the McClintock analysis to small void coalescences. The proposed model offers an explanation for some important aspects of experimental observations of ductile fracture.
2 citations