关键词: 预紧力, 螺栓连接, 螺纹, 螺纹面数学模型, 应力分布

Abstract:  It was difficult to accurately determine the thread stresses on the bolts under pre-tensionsing conditions， which might lead to strength fracture and premature loosening of the threads， and the reliability of the bolt joints was compromised. Currently， the contact state of the thread surfaces was usually described by stresses under an absolute coordinate system. However， the simulated stress direction was at an angle to the actual thread surface. The analysis results were not intuitive. Therefore， a thread mathematical model was derived and the extended stress analysis method of thread contact surfaces was proposed. Then， the finite element model of bolt joints was established for the structural characteristics of bolts. And the accuracy of the model was verified by tests. Finally， the extended stress analysis method was applied to study the thread surface stress and the distribution characteristics of bolts. The results show that the maximum error between the simulated preload and the testing preload is only 5.78%, where the accuracy of the simulation model is demonstrated. The extension stress analysis method may reflect the continuity and monotonicity of the stress distribution on the thread surfaces, and the method also reflects the optimal preload. The decreasing rate of the stress on the same layer thread is inversely proportional to the stress. From the stress analysis， the reason why the stresses on the thread are mainly concentrated in the first three turns is illustrated. The thread extension stress analysis method proposed herein is more intuitive and accurate. The paper may provide theoretical support for the anti-loosening analysis and reliability analysis of bolts.

Key words: preload, bolt joint, thread, mathematical modeling of threaded surface, stress distribution