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Transformation thermomechanics in an Fe-based shape momory alloy

铁基形状记忆合金的相变热力学

基本信息

批准号：
09650112
负责人：
TANAKA Kikuaki
金额：
$ 2.05万
依托单位：
Tokyo Metropolitan Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650112/
关键词：
Shape memory alloy Unified thory Transformation condition Thermomechanical loads Transformation surfarce Martensitic transformation Back stress Strain recovery

项目摘要

A transformation condition, which depends on the thermodynamic generalized forces and the internal variables, was introduced to describe the start and progress of the martensitic transformation. A set of evolution equations for the internal variables were derived by solving a conditional extremum problemcomposed of the dissipation inequality and the tranformation condition. The thermoelastic, rate-type, constitutive relations and the evolution equations govren the behavior of the alloy. The transformation condition introduced was proved to be judt the transformation driving force discussed in metallurgy. The concepts of the "isotropicphardening" and the "kinematical hardening" were developed theoretically.The martensite start condition and the austenite start/finish conditions were determined experimentally under the multiaxial stress state. The martensite start surface, represented by an oval cone, was asymmetric in the stress-temperature space, thus approving the theory with the third invariant of the stress deviator. The austenite start consition was given by a plane in the stress-temperature space. The direction of the plane depends on the martensite variants induced during loading, whereas the posion of the plane the amount ofthe martensite. The austenite start plane translates depending on the amount of martensite. In case many martensite variants are induced during loading, the austenite start condition is represented by a polygonal cone.

引入了一个依赖于热力学广义力和内部变量的相变条件来描述马氏体相变的开始和过程。通过求解由耗散不等式和变换条件组成的条件极值问题，导出了一组内部变量的演化方程。热弹性关系、速率型关系、本构关系和演化方程决定了合金的行为。证明了所介绍的转化条件可以判断冶金学中所讨论的转化驱动力。从理论上提出了“各向同性硬化”和“运动硬化”的概念。实验确定了多轴应力状态下的马氏体起始条件和奥氏体起始/结束条件。马氏体起始面以椭圆锥体表示，在应力-温度空间上不对称，从而证实了应力偏差第三不变量的理论。奥氏体的起始形态由应力-温度空间中的平面表示。平面的方向取决于加载过程中马氏体的变化，而平面的位置取决于马氏体的数量。奥氏体起始面随马氏体的数量而变化。当加载过程中诱发多种马氏体变异体时，奥氏体的起始条件用多边形圆锥体表示。