Search

Purpose: The purpose of this study is to show how gradual strength degradation of metal beams under cyclic bending up to fatigue failure is simulated based on a new elastoplasticity model free of any yield criterion. Design/methodology/approach: A new approach is proposed toward accurately and explicitly prescribing evolution of non-uniform stress distribution on beam cross-section under cyclic bending and, as such, gradual degradation of the bending strength can be directly determined. Findings: Explicit results for the bending response in a whole cyclic process up to fatigue failure are obtained and the fatigue characteristic curve is for the first time simulated directly between the curvature amplitude and the cycle number to failure. Originality/value: First, explicit and accurate determination of the non-uniform stress distribution on beam cross-section is achieved with asymptotic softening effects. Second, degradation of the bending strength can be directly deduced cycle by cycle. Finally, the relationship between the bending moment and the curvature is calculated using new and efficient numerical algorithms, thus bypassing usual time-consuming calculations with finite element procedures. Numerical results are presented and in good agreement with experimental data. [ABSTRACT FROM AUTHOR]

High‐efficiency algorithms are proposed for numerically integrating elasto‐plastic rate equations for the purpose of simulating metal failure effects under repeated loading conditions. Results are obtained with a newly established elasto‐plasticity model which can automatically simulate both low and high cycle fatigue failure effects, with reference to neither damage‐like variables nor ad hoc failure criteria. Novelties are incorporated in a few respects. First, multiaxial loading processes with arbitrarily changing principal stresses and axes can be treated in a broad sense beyond usually treated proportional loading cases. Second, by means of the commonly used J2‐invariant of the deviatoric stress, multiaxial loading cases can be directly treated just as in the uniaxial loading case. Third, high cost in time consumption can be considerably reduced in evaluating both low and high cycle failure effects. Numerical examples are presented for simulating uniaxial and multiaxial fatigue failure effects and simulation results are in good agreement with experimental data. Results show that the computation speed with the new algorithms exceeds 600 times faster than usual integration algorithms. [ABSTRACT FROM AUTHOR]

A new criterion for predicting metal failure effects under cyclic loading conditions is derived from an innovative elastoplasticity model established most recently. As compared with usual approaches, novel results with this new criterion are presented in four respects: (i) both low and high cycle fatigue effects can be simultaneously simulated in a unified and direct manner; (ii) cumbersome trial‐and‐error procedures in identifying numerous unknown parameters can be bypassed; (iii) time‐consuming numerical procedures are not involved in treating responses in cyclic loading processes; and, for the first time, (iv) data sets for fatigue failure can be simultaneously matched for various cases of the cyclic stress ratio. Numerical examples show that model predictions are in accurate agreement with test data. [ABSTRACT FROM AUTHOR]

A finite strain J2‐flow model of von Mises type for elastoplastic behaviors of metals is proposed with a new characterization of the evolving yield strength. It is intended for providing solutions to a few unresolved issues concerning a simultaneous simulation of realistic hardening and softening effects for metals up to failure. Such issues are concerned with three respects, namely, how to ensure that the simulation is accurate in the sense that sufficient uniaxial experimental data for both hardening and softening effects can be matched with no errors, how to ensure that the simulation is explicit in the sense that any implicit trial‐and‐error iterative procedures in identifying numerous parameters can be bypassed, and how to ensure that the simulation is of broad applicability in the sense that any given uniaxial data for metals can be automatically matched. With the new model proposed, solutions to such issues are obtained by presenting an accurate and explicit form of the yield strength function that automatically matches any given test data. Numerical examples with realistic hardening‐to‐softening transition effects are presented for the first time for the finite strain responses of both uniaxial stretching and simple shearing up to the eventual failure. [ABSTRACT FROM AUTHOR]