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Elastoplastic material models
Published in Jamshid Ghaboussi, David A. Pecknold, Xiping Steven Wu, Nonlinear Computational Solid Mechanics, 2017
Jamshid Ghaboussi, David A. Pecknold, Xiping Steven Wu
In a multiaxial state of stress, the initial yielding of course occurs as the stress point reaches the initial yield surface. It was shown in an earlier section that in perfect plasticity, the yield surface remains unchanged. However, with hardening material behavior, the yield surface changes as the material is loaded beyond the first yield. The hardening rule specifies how the yield surface is assumed to evolve.
Investigating the effective stress function algorithm for the thermostructural analysis and design of liquid rocket engines thrust chambers
Published in Journal of Thermal Stresses, 2021
Bilotta et al. developed a novel method to solve incremental elastic-plastic analysis of structures based on a sequential quadratic programming of the finite step equations [14]. This method is very robust and efficient when adopted for elastic-plastic cases. Mahbadi and Eslami proposed the method of successive approximation to solve plasticity problems since the history of loading becomes an important factor and should be taken into account [15]. Furthermore, the method is capable of handling plasticity loading and unloading and moving of the yield surface (e.g. the kinematic hardening model). Kojic and Bathe developed the “Effective Stress Function” (ESF) algorithm in which the stress state is identified when a specific variable, the effective stress, is solved [16]. Then, the same authors developed a more general algorithm called “the governing parameter method” which can be considered as a generalization of the ESF algorithm [6]; in fact, in this method, a different parameter can be identified instead of the effective stress function. In the frame of the present work the main scope is to demonstrate that the “governing paramater/ESF algorithm” is well suited to study rate independent plasticity and time dependent creep phenomena occurring in the ligament of the cooling channel of a liquid rocket engine thrust chamber. Since the peculiarity of the test case under investigation is such that the main parameter of the stress/strain field is the effective stress, the original ESF algorithm has been considered. The numerical model employing the ESF algorithm has been implemented in a Fortran based finite element code developed by the author.
Numerical investigation of the hull girder ultimate strength under realistic cyclic loading derived from long-term hydroelastic analysis
Published in Ships and Offshore Structures, 2023
Going back to the literature, most ultimate strength investigations are considering a perfect plastic material model, where the yield surface remains unchanged. However, in reality, the yield surface may change size, shape, and position. In the case of plane stress, the yield surface can be seen as the boundary of a region in the stress space in which both loading and unloading of a structure produces only elastic strains. A typical Von Mises yield surface for plane stress is illustrated in Figure 4 with a solid grey line.