螺纹紧固件咬死失效的热力学分析和试验研究

The seizure failure of threaded fasteners is a typical failure form during the tightening process. In view of the lack of thermodynamic model of friction heat generation for the micromorphology on the thread surface in the tightening process which causes the mechanism of seizure failure unclear, and the lack of quantitative evaluation indication of seizure failure, an asperity model was firstly established. Subsequently, the heat accumulation and temperature rise models for the asperity on the thread surface were established based on HERTZ contact theory. The mechanism of seizure failure was revealed theoretically. Then repeated tightening experiments were carried out on threaded fasteners by torsion-tension testing machine to study the variation of various fastening parameters. The indication system for evaluating the seizure failure was proposed, including the tooth fluctuation of the angle-torque curve, and the over 50% increase rate for the torque coefficient and thread friction coefficient. the testing method and indication for quantitatively evaluating the anti-seizure performance of thread fasteners were put forward by recording the tightening times when the seizure failure occurred. The influences of nut material, bolt/nut clearance, surface hardness difference and thread friction coefficient on the anti-seizure performance of threaded fasteners were systematically obtained.