Experimental characterisation of a CuAg alloy for thermo‐mechanical applications. Part 1: Identifying parameters of non‐linear plasticity models

Abstract

Despite the wide use of copper alloys in thermo‐mechanical applications, there is little data on their cyclic plasticity behaviour, particularly for CuAg alloys. This prevents the behaviour of the materials from being correctly described in numerical simulations for design purposes. In this work CuAg0.1 alloy used for thermo‐mechanical applications was tested by strain‐controlled cyclic loading at 3 different temperatures (room temperature, 250°C, 300°C). In each test, stress‐strain cycles were recorded until the alloy had completely stabilised. These cycles were then used to identify material parameters of non‐linear kinematic and isotropic models. The focus was on plasticity models (Armstrong‐Frederick, Chaboche, Voce) that are usually implemented in commercial finite element codes. Simulated cyclic responses with the identified material models were compared with experiments and showed a good agreement. The identified material parameters for the CuAg alloy under investigation can be used directly in finite element models for cyclic plasticity simulations, thus enabling a durability analysis of components under thermo‐mechanical loads to be performed, particularly in the field of steel‐making plants.

Acceleration techniques for the numerical simulation of the cyclic plasticity behaviour of mechanical components under thermal loads

“…In the FEM model 8-node elements were used. The thermal flux proposed in [14] was 50% increased to reach a maximum temperature close to 300 o C for which material parameters are available in [15]. The convection coefficient is 48000 W/m 2 K and temperature of the cooling water is 40 °C.…”

“…Since the component is free to expand, no mechanical constraints were imposed on the numerical model. The nonlinear mechanical analysis was performed assuming temperature dependence of material parameters and considering combined (nonlinear kinematic + nonlinear isotropic) model with parameters taken from [15].…”

“…As material, it was assumed a CuAg0.1 alloy, whose properties, listed in Tab. 1, were experimentally obtained in [15,16,17].…”

Experimental characterisation of a CuAg alloy for thermo‐mechanical applications. Part 2: Design strain‐life curves estimated via statistical analysis

“…If the median strain-life line is written as in Equation 1, the intercepts and slopes of the elastic and plastic components can be recovered by inverting Equation 3:…”

“…2 Part 1 of this article showed how material parameters of nonlinear kinematic and isotropic plasticity models could be identified from experimental cyclic data at 3 different temperatures. 3 To estimate the mould service life, computed stress and strain cycles need to be compared with the material fatigue curve. Unfortunately, as with cyclic plasticity data, experimental strain-life curves for Cu alloys (and especially for CuAg type) are also rare in the literature.…”