振动时效中结构动态参数变化机理的探讨

Preliminary Exploration of Engineering Mechanism underlying Variations of Dynamic Structural Parameters During Vibration Aging

本文探讨在振动时效中，金属材料的位错密度和晶格扭曲程度对结构动态参数的影响机理．即含有残余应力的构件，在振动时效期间，晶格扭曲程度和位错密度变化的结果是金属材料内部发生一定的塑性变形和微塑性变形，降低了残余应力；同时，材料结构的阻尼减小，刚度降低。

It is a well-known experimental fact that variations of the dynamic structural parameters can reliably reflect relaxation of residual stresses.In this paper the authors explore preliminarily the engineering mechanism underlying this experimcntal fact.The authors' exploration starts with taking what is useful in existing experimental findings not directly related to vibration aging. Fig.2 shows that increase in dislocation density is directly responsible for reduction of elastic modalus. Fig. 1 shows a bysteris loop; it is known that with inereasing true strain the loop becomes smaller and damping is reduced. The authors' preliminary dynamic model for vibration aging is consistent with the above-mentioned experimental findings not related to vibration aging. It is mathematically cxpressed by Eq. (2). It is believed that the authors' model and Eq.(2) can be used to retain benificial residual stresses (generally compressive) longer and to quicken the relaxation of undesirable residual stresses (generally tensile).