The ratcheting behavior of the “unsymmetric two-bar system” was investigated by numerical experiments. The two bars are restrained to the same length and are subjected to a constant load. One bar sees cyclic temperature variations, while the other bar is kept at constant temperature. The material models employed are rate independent plasticity (kinematic hardening) and the viscoplasticity theory based on overstress (VBO) matched to represent the cyclic neutral 6061 T6 aluminum alloy elastic and inelastic deformation behavior. For simplicity, temperature-independent material properties were assumed. Numerical analyses were performed to investigate the effects of rate of thermal loading and temperature range. Elastic-inelastic shake down is ultimately achieved due to work hardening. There is a strain range increase until it reaches a steady value. Kinematic hardening and VBO predict almost the same strain range, which, for the case of VBO, is nearly rate-independent. The behavior for both material models is very different for the mean strain. For VBO, the number of cycles to shakedown is rate-dependent and is considerably larger than for kinematic hardening. Finally, the steady-state mean strain and strain range are computed directly for VBO.

Issue Section:
Research Papers
Topics:
Viscoplasticity, Temperature, Hardening, Kinematics, Aluminum alloys, Cycles, Deformation, Materials properties, Numerical analysis, Plasticity, Steady state, Stress, Work hardening
1.
Gokhfeld, D. A., and Sadakov, O. S., 1995, “Steady Cyclic State of a Structure: Methods of its Direct Determination,” Inelastic Behaviour of Structures Under Variable Loads, Z. Mroz, D. Weichert, and S. Dorosz, eds., Klu¨ver, Dordrecht, and Boston, pp. 449–461.
2.
Ko¨nig
J. A.
, and
Maier
G.
,
1981
, “
Shakedown Analysis of Elastoplastic Structures: A Review of Recent Developments
,”
Nuclear Engineering and Design
, Vol.
66
, pp.
81
–
95
.
3.
Krempl, E., 1996, “A Small Strain Viscoplasticity Theory Based on Overstress,” Unified Constitutive Laws of Plastic Deformation, A. S. Krausz and K. Krausz, eds., Academic Press, New York, NY.
4.
Megahed
M. M.
,
1981
, “
Influence of Hardening Rule on the Elasto-Plastic Behavior of a Simple Structure under Cyclic Loading
,”
International Journal of Mechanical Science
, Vol.
23
, pp.
169
–
182
.
5.
Miller, A. K., ed., 1987, Unified Constitutive Equations for Plastic Deformation and Creep of Engineering Alloys, Elsevier Applied Science.
6.
Miller
D. R.
,
1959
, “
Thermal-Stress Ratchet Mechanism in Pressure Vessels
,”
ASME Journal of Basic Engineering
, Series D, Vol.
81
, pp.
190
–
196
.
7.
Polizzoto, C, 1995, “Elastic-Viscoplastic Solids Subjected to Thermal and Loading Cycles,” Inelastic Behavior of Structures Under Variable Loads, Z. Mroz, D. Weichert, and S. Dorosz, eds., Klu¨ver, Dordrecht, and Boston, pp. 95–128.
8.
Yao, D., 1987, “Theory of Viscoplasticity Based on Overstress with Applications,” Ph.D. thesis, Rensselaer Polytechnic Institute, Troy, NY.
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