A Thermomechanical Study of Stress and Fatigue in Shape-Memory Alloys with Applications to Micromechanical Structures

CMS 9800006 PI：P. Papadopoulos UC Berkeley 摘要 多晶形状记忆合金在一般三维应力状态和有限运动学下的理论、实验和计算研究 是 进行更好的 理解 他们的不确定性 在应激反应和 疲劳 寿命预测 的 数学结构 的 利用连续热塑性对超弹性和形状记忆效应进行宏观模拟。固-固相变与屈服函数相关联，而速率型本构方程被假定为非弹性应变和硬化变量的演化。 应力响应来自于比自由能函数，该比自由能函数被计算为所有活性相的比自由能加上与它们之间的转换相关联的自由能的加权平均值。 这里分析的系统有许多重要的应用， 生物工程 和对照 的 复合智能结构 ***

CMS 9800006 PI: P. Papadopoulos UC Berkeley ABSTRACT A combined theoretical, experimental, and computational study of polycrystalline shape memory alloys in the presence of general three dimensional stress states and finite kinematics is conducted to better understand their uncertainty in stress response and in fatigue life prediction. The mathematical structure of continuum thermoplasticity is exploited for macroscopic modeling of superelasticity and shape memory effect. Solid -solid phase transitions are associated with yield-like functions while rate type constitutive equations are postulated for the evolution of inelastic strain and hardening like variables. The stress response is derived from a specific free energy function calculated as a weighted average of specific free energies of all active phases plus the free energies associated with the transformations between them. The systems analyzed here have numerous important applications in bioengineering and in the control of composite intelligent structures. ***