PLASTIC REGION BOLT TIGHTENING CONTROLLED BY ACOUSTIC EMISSION MONITORING

摘要

Troubles related to bolt relaxation and fatigue have occurred in many fields. In the automotive industry, plastic-region tightening method is recognized as a good technique for preventing the relaxation and fatigue of bolts. However, this method requires a special torque wrench and involves a complicated procedure for stable tightening. Therefore, it is important that a new tightening method and a wrench that simplifies plastic region bolt tightening are developed. Two types of tensile tests using a torque wrench and a tensile tester were conducted for two different strength bolts. The Mahalanobis distance (MD) technique was utilized for discriminating acoustic emission (AE) signals from noise signals. We found that we can monitor the yield point of a high-strength bolt during loading by AE monitoring combined with the MD technique. Here, we conducted a feasibility study for controlling plastic-region tightening by AE techniques.