基于位错密度演化的高频振动时效微观机理研究

Research on microcosmic mechanism of high-frequency vibratory stress relief based on dislocation density evolution

摘要:

为了揭示高频振动时效消除残余应力的微观机理,探讨了高频振动载荷作用下的位错密度演化特性对残余应力松弛的影响规律。分别采用Williamson-Hall(WH)法和小孔法分析高频振动前后Cr12MoV钢淬火试样的位错密度和残余应力。在实验研究的基础上,采用微观动力学理论,建立晶粒多自由度系统,分析高频振动激活位错运动的机制,进一步采用晶体塑性理论,建立高频振动作用下的位错密度演化控制方程,分析高频振动时效消除残余应力的微观机理。结果表明：材料内的位错在高频振动的作用下激活运动,产生位错累积和位错湮灭两个演化过程,其中材料内的位错湮灭过程占据主导地位,从而降低了材料内的位错密度；位错密度的降低减小了材料内的晶格畸变程度,从而松弛了材料内的残余应力。

Abstract:

In order to reveal the mechanism of the high-frequency vibratory stress relief, the effect of the evolution of the dislocation density with the help of high-frequency vibration on the residual stress relaxation. The Williamson-Hall (WH) method and the hole-drilling method were used to evaluate the dislocation densities and the residual stresses in the Cr12MoV steel quenched specimen before and after high-frequency vibration. Based on the experimental results, the multi-freedom system of the crystal grain was developed based on the microscopic dynamics theory in order to analyze the mechanism of high-frequency vibration activated dislocation motion. In addition, the governing equation of the dislocation density evolution with the aid of high-frequency vibration was proposed in order to reveal the microcosmic mechanism of the high-frequency vibratory stress relief. The results show that the dislocations inside the materials were activated with the help of high-frequency vibration. The dislocation density evolution process mainly consists of the dislocation accumulation process and the dislocation annihilation process. And the dislocation annihilation process has a dominant process with the help of high-frequency vibration, which results in that the dislocation density inside the materials can be reduced. The degree of the lattice distortion can be reduced due to the decrease of the dislocation density. As a result, the residual stress inside the materials can be relieved by the high-frequency vibratory stress relief.