Showing papers on "Viscoplasticity published in 1971"
••
TL;DR: In this article, the authors present the formulation of the thermodynamic theory of a rate-sensitive plastic material within the framework of thermodynamics of a material with internal state variables, while the components of the inelastic deformation tensor appear as internal state parameters.
Abstract: Publisher Summary This chapter reviews the thermodynamic foundations of the theory of viscoplasticity. The essential feature of viscoplasticity is the simultaneous description of rheologic and plastic effects of a material. The necessity for simultaneous consideration of viscoelastic and plastic properties of a material is indicated by the experimental investigations of dynamic loads. The thermodynamic theory of elastic-viscoplastic materials presents for finite strains two basic difficulties. The first of these is connected with the kinematic description of plastic deformation. The second difficulty concerns the problem of choice of thermodynamic variables of state. The chapter discusses development of the thermodynamic theory of plasticity for finite strains using the rate-type theory, and generalized the inviscid theory of plasticity to nonisothermal finite deformations. The principle of material frame indifference called “invariance requirements under superposed rigid body motions,” was used and explored the thermodynamical restrictions. The chapter presents the formulation of the thermodynamic theory of a rate-sensitive plastic material within the framework of thermodynamics of a material with internal state variables. In this thermodynamic theory of an inelastic material, the deformation tensor and temperature are considered as thermodynamic state variables, while the components of the inelastic deformation tensor appear as internal state parameters.
330 citations
01 Jan 1971
TL;DR: In this article, the endochronic theory of viscoplasticity was used to give quantitative analytical predictions on the mechanical response of aluminum and copper under conditions of complex strain histories, such as cross-hardening, loading and unloading loops, cyclic hardening as well as behavior in tension in the presence of a shearing stress.
Abstract: : The endochronic theory of viscoplasticity developed previously by the author is used to give quantitative analytical predictions on the mechanical response of aluminum and copper under conditions of complex strain histories. One single constitutive equation describes with remarkable accuracy and ease of calculation diverse phenomena, such as cross-hardening, loading and unloading loops, cyclic hardening as well as behavior in tension in the presence of a shearing stress, which have been observed experimentally by four different authors.
26 citations
••
01 Jan 1971TL;DR: In this article, a theory of viscoplasticity was developed on the basis of the concept that the current state of stress is a functional of the entire history of deformation and temperature, but the history was defined with respect to a time scale which is in itself a property of the material at hand.
Abstract: In Part I of this work, a theory of viscoplasticity (of which the theory of plasticity was a part) was developed on the basis of the concept that the current state of stress is a functional of the entire history of deformation and temperature,
but the history was defined with respect to a time scale which is in itself a property of the material at hand.
3 citations
••
TL;DR: In this article, the behavior of viscoplastic material under dynamic load was considered for two cases; that is, a longitudinal impact of a rigid mass on a finite rod and a normal impact of the finite rod on a rigid wall.
Abstract: Behavior of viscoplastic material under dynamic load was considered for two cases; that is, a longitudinal impact of a rigid mass on a finite rod and a normal impact of a finite rod on a rigid wall. Constitutive equation of Bingham type was modified by taking strain-hardening effect into account. As governing equations of the problems were of nonlinear type with moving boundaries, the difference method was employed to solve them. Numerical results for distributions of particle velocities and of strains and their variations with respect to time differed even qualitatively from the results obtained by a theory without strain-hardening. Experiments on a soft mild steel containing 0.015% carbon were conducted. It was found that the numerical results and experiments for permanent strain distribution agreed well. Variations of strain distribution with respect to time during impact were observed by a high speed camera and numerical results were found to predict the behavior qualitatively.
1 citations
••
TL;DR: In this article, an analysis of the dynamic problem of a hollow sphere is presented, where the medium is assumed elastic/viscoplastic, satisfying Mises condition, isotropic hardening and viscoplastic incompressibility.
••
TL;DR: In this article, a non-associated flow rule is proposed for rigid-viscoplastic material, which is an approximation to the exact associated constitutive equations based on Huber-Mises yield condition.
Abstract: A certain form of non-associated constitutive equations for rigid-viscoplastic material is postulated. These equations are linear in stresses and are regarded as an approximation to the exact associated constitutive equations based on Huber-Mises yield condition. A limit transition to the perfectly plastic material and loading-unloading criteria are discussed in detaile. An important feature of the new equations is that their linear form is preserved after integration over the shell thickness. The non-associated flow rule is shown to be particularly useful in the dynamic problems for rotationally symmetric shells. An example of the application of the approximate theory is given.