EXPERIMENTAL IDENTIFICATION AND MATHEMATICAL-MODELING OF VISCOPLASTICMATERIAL BEHAVIOR

Authors
Citation
P. Haupt et A. Lion, EXPERIMENTAL IDENTIFICATION AND MATHEMATICAL-MODELING OF VISCOPLASTICMATERIAL BEHAVIOR, Continuum mechanics and thermodynamics, 7(1), 1995, pp. 73-96
Citations number
25
Categorie Soggetti
Mechanics,Thermodynamics
ISSN journal
09351175
Volume
7
Issue
1
Year of publication
1995
Pages
73 - 96
Database
ISI
SICI code
0935-1175(1995)7:1<73:EIAMOV>2.0.ZU;2-W
Abstract
Uniaxial torsion and biaxial torsion-tension experiments on thin-walle d tubes were carried out to investigate the viscoplastic behavior of s tainless steel XCrNi18.9. A series of monotonic tests under strain and stress control shows nonlinear rate dependence and suggests the exist ence of equilibrium states, which are asymptotically approached during relaxation and creep processes. Strain controlled cyclic experiments display various hardening and softening phenomena that depend on strai n amplitude and mean strain. All experiments indicate that the equilib rium states within the material depend on the history of the input pro cess, whereas the history-dependence of the relaxation and creep behav ior appears less significant. From the experiments the design of a con stitutive model of viscoplasticity is motivated: The basic assumption is a decomposition of the total stress into an equilibrium stress and a non-equilibrium overstress: At constant strain, the overstress relax es to zero, where the relaxation time depends on the overstress in ord er to account for the nonlinear rate-dependence. The equilibrium stres s is assumed to be a rate independent functional of the total strain h istory. Classical plasticity is utilized with a kinematic hardening ru le of the Armstrong-Frederick type. In order to incorporate the amplit ude-dependent hardening and softening behavior, a generalized are leng th representation is applied [14]. The introduction of an additional k inematic hardening variable facilitates consideration of additional ha rdening effects resulting from the non-radiality of the input process. Apart from the common yield and loading criterion of classical plasti city, the proposed constitutive model does not contain any further dis tinction of different cases. The experimental data are sufficient to i dentify the material parameters of the constitutive model. The results of the identification procedure demonstrate the ability of the model to represent the observed phenomena with satisfactory approximation.