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In this paper, a novel unified plasticity methodology is proposed to allow the coupling of rate- and temperature-sensitivity of engineering alloys as well as the non-linear kinematic hardening behavior often observed during cyclic loading. The proposed methodology is general in the sense that an arbitrary constitutive model may be chosen for the viscoplastic part, as well as the cyclic part. We adapt our model with a physically-motivated viscoplasticity flow rule and a nonlinear kinematic hardening model. In contrast with other unified plasticity models, the simplified theory involves few material parameters that can be readily calibrated from standard mechanical tests. The capabilities of the proposed theory are demonstrated for a hot rolled annealed 304L stainless steel supplied by Vimetal Peckover. The model is tested with stress–strain curves obtained from standard tensile and cyclic uniaxial tests at various strain amplitudes and strain-rates, and good accuracy of the response is obtained for strains up to 15%, within a temperature range of 293–673 K. We note that the cyclic plasticity model in our adapted theory can be readily enhanced with ratchetting, mean stress relaxation, strain amplitude history, Masing effects or other complex capabilities.

The austenitic stainless steel E309L filler is a commonly used material for in-situ crack repairs of hydro-turbines due to its high weldability, mechanical and chemical compatibility with the turbine's base material. However, experimental data for the as-welded E309L filler is scarce. In this paper, the mechanical properties of as-deposited 75% Ar/25% CO 2 flux-cored arc welding E309L austenitic stainless steel are investigated. The material is shown to be rate- and temperature-sensitive. Furthermore, although the directional nature of the welding/repair process might suggests otherwise, the response is found to be isotropic. Finally, a classic three-dimension Johnson-Cook plasticity theory is implemented and reproduces the experimental results with good accuracy.

In this paper, the industrial hammer peening process is optimized using multi-objective, sequential approximate optimization, which is a mathematics- plus finite element- based algorithm. Since the number of design and objective variables is significant, the global optimization problem is split into two, more manageable multi-objective subproblems. The use of surrogate modelling together with an intensification and diversification strategy for solving the optimization subproblems allows for significant computational cost savings without loss of accuracy. Additionally, we propose a Bayesian inference criterion-based sensitivity approach for "filtering-out" design variables which do not significantly affect objectives variables. Finally, guidelines for selecting appropriate Pareto optima are given using N?1$N-1$ Pareto diagrams, where N is the number of objective variables.

Interconversion of viscoelastic material functions is a longstanding problem that has received attention since the 1950s. There is currently no accepted methodology for interconverting viscoelastic material functions due to the lack of stability and accuracy of the existing methods. This paper presents a new exact, analytical interconversion method for linearly viscoelastic material functions expressed as Prony series. The new algorithm relies on the equations of the thermodynamics of irreversible processes used for defining linearly viscoelastic constitutive theories. As a result, interconversion is made possible for unidimensional and tridimensional materials for arbitrary material symmetry. The algorithm has been tested over a broad range of cases and was found to deliver accurate interconversion in all cases. Based on its accuracy and stability, the authors believe that their algorithm provides a closure to the interconversion of linearly viscoelastic constitutive theories expressed with Prony series. © 2012 Springer Science+Business Media, B. V.