Abstract
Ratcheting failure of materials and structures subjected to low cycle fatigue in the presence of significant mean stress is of great interest to researchers. In this experimental and numerical study, the response of 316L stainless steel samples was observed in symmetric strain control uniaxial test followed by post-stabilized monotonic test, uniaxial and biaxial ratcheting tests, in order to determine the Chaboche model parameters and to evaluate ratcheting prediction using finite element analysis. The critical elastic limit was initially obtained from incremental uniaxial cyclic tests. The Chaboche parameters were subsequently extracted from experimental hysteresis and post-stabilized monotonic stress plastic-strain curves using two optimization technics, namely, the Particle Swarm Optimization (PSO) and Genetic Algorithm (GA). The two optimization methods were compared for efficiency, in terms of time and accuracy. The PSO method presented higher efficient results and was subsequently used to derive the parameters from hysteresis and post-stabilized monotonic curves. Different values (by definition) of elastic limit were also used. The Finite Element commercial software ANSYS was utilized with the Chaboche model to predict the uniaxial and biaxial ratcheting behavior of 316L stainless steel pipe. The comparison between experimental and the numerical simulation demonstrates that adopting post-stabilized monotonic curve rather than hysteresis curve and with accurate elastic limit obtained from incremental loading test improves ratcheting prediction significantly.
Highlights
Load-bearing engineering components are frequently exposed to random loading and the risk of occurrence of ratcheting is increased significantly [1,2,3,4,5]
The stress-plastic strain parameters determined using the Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) schemes are calculated after setting 244 MPa as the elastic limit, which was obtained from incremental uniaxial test result in
Incremental uniaxial test pre-hardening an from experimental uniaxial and hysteresis
Summary
Load-bearing engineering components are frequently exposed to random loading and the risk of occurrence of ratcheting is increased significantly [1,2,3,4,5]. Pressure vessels and piping system, structures operating in earthquake zones, airplane landing gears and nuclear reactors are typical examples of such components and structures [6,7,8]. Structures subjected to stress cycles beyond the elastic limit oblige a trustworthy design, especially in the presence of a significant mean stress from loads such as dead weight or internal pressure [1,6,9,10]. Among the available models in commercial software, the Chaboche model is the most powerful [14]. This model overpredicts ratcheting strain under either uniaxial or multiaxial loading when compared with experimental results [13,15,16,17]
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