考虑塑性应变记忆恢复的循环棘轮本构模型研究

在统一粘塑性循环本构理论框架下，以Ohno-Abdel-Karim非线性随动硬化模型为基础，建立了一个循环本构模型。模型通过引入塑性应变幅值记忆效应，并在塑性应变记忆项中加入恢复系数，提高了对循环硬化材料单轴棘轮行为的预言能力。将模型应用于316L不锈钢单轴棘轮行为的描述中，模拟不同平均应力、应力幅值下的棘轮应变，均与实验数据吻合较好，证明本文改进的本构模型能合理地描述循环硬化材料的单轴棘轮行为。

Cyclic ratcheting constitutive model considering plastic strain memory recovery

Ratcheting, a cyclic accumulation of inelastic deformation occurred in the engineering materials subjected to asymmetrical stress-controlled cyclic loading, can make the deformation of the structures exceed the designed limitation or shorten the fatigue life of engineering components. Based on the framework of unified visco-plasticity, a new cyclic constitutive model is proposed to describe the ratcheting behavior of cyclic hardening materials on the basis of Ohno-Abdel-Karim model. As we know, the level of cyclic hardening increases with the increase of plastic strain amplitude in the cyclic deformation tests for cyclic hardening materials. Then, the memory surface for maximum plastic strain amplitude effect is introduced to reflect the effect and the dynamic recovery coefficient is added to the plastic strain memory term to reflect the effect of maximum plastic strain on isotropic deformation resistance. The definition of the Tanaka’s non-proportionality is adopted to describe the multiaxial ratcheting deformation with different multiaxial loading paths. Then, the proposed model is adopted to describe the stress-strain responses of 316L stainless steel (which is a kind of cyclic hardening material ) under uniaxial tension, strain-controlled cyclic loading and stress-controlled cyclic loading cases. Comparing with the corresponding experimental results, it can be found that, the uniaxial and multiaxial ratcheting of 316L stainless steel can be reasonably described by the proposed model. Furthermore, the model can also reflect the various degrees of non-proportional addition hardening with different proportional and non-proportional loading paths properly. To sum up, the capability of the proposed model to predict the uniaxial and multiaxial ratcheting behavior of cyclic hardening material is well improved by introducing the effect of plastic strain memory recovery. It is believed that the proposed model is useful for the design and fatigue life prediction of engineering components.