تعیین خصوصیات تجربی یک آلیاژ CuAg
Abstract
1-Introduction
2-Non-linear hardening models: theoretical background
3-Plasticity models: identifying parameters from experimental data
4-Low-cycle fatigue curves
5-Conclusions
References
Abstract
The cyclic response and low-cycle fatigue strength of a CuAg0.1 alloy for thermo-mechanical applications are investigated by isothermal strain-controlled fatigue tests at three temperature levels (room temperature, 250°C, 300°C). Both cyclic and stabilized stress-strain responses are used for identifying the material parameters of non-linear kinematic (Armstrong-Frederick, Chaboche) and isotropic models. The identified material parameters are used in numerically simulated cycles, which are successfully compared to experiments. Linear regression analysis of experimental fatigue data allows the “mean” low-cycle fatigue curves to be estimated. Approximate statistical methods are finally adopted to evaluate the design low-cycle fatigue curves at prescribed failure probability and confidence levels.
Introduction
Copper alloys have an optimal combination of high conductivity and good mechanical properties, which makes these materials suitable in thermo-mechanical applications in which components are subjected to high thermal flux combined to mechanical loads. An example in continuous casting plants is a mold (or crystallizer), which is a long (~1m) hollow component where the molten steel starts to solidify. Owing to the high temperatures of the molten steel, the mold is subjected to a high thermal flux − also varying over time (due to plant switch on/off) − which may cause a network of thermal cracks to appear on the inner surface. In the design phase, finite element modeling can profitably be used for simulating the mold thermo-mechanical response and to compute stresses and strains, which, combined with fatigue curves, allow the mold service life to be estimated. Numerical modeling requires suitable plasticity models, calibrated on experimental data. Conventional molds are usually made by CuAg, CuCrZr, or sometimes CuNiBe alloys [1]. While thermo-physical and mechanical properties in the literature mainly refer to CuCrZr alloys, data for CuAg alloys are far more scarce [1]. Aiming to provide a contribution, this work will experimentally characterize a CuAg0.1 alloy for thermomechanical applications by using low-cycle fatigue tests at three different temperatures (room, 250 °C, 300 °C). Stress-strain data recorded in each test are used for identifying parameters of non-linear kinematic and isotropic plasticity models. Numerical simulations using the identified material parameters are next compared to experimental cyclic responses.