Reliability Design Of Thread Connection And Its Tightening Process Research

As the basic structure in the vehicle final assembly, thread connection’s reliability concern the vehicle’s overall performance, for example the thread connection structure in chassis parts related to the safety performance of the vehicle. The key to ensure the reliability of thread connection structure lies in the reasonable selection of thread fasteners and reasonable control of its prestressing force. However, due to the slowly development of the domestic automobile industry, it is insufficient in choice of the thread fasteners and the control of prestressing force. For example due to scattering difference of the prestressing force is too large, in order to ensure reliable connection of the thread structure, engineer usually choose more bigger safety coefficient, although there is no risk to lead to overload damage, its prestressing force is relatively low. This is not conducive to give full play to the efficiency of the thread fasteners. At the same time, because the prestressing force is relative too small, there is disadvantageous for loose resistance performance and fatigue performance of the thread fasteners. Meanwhile, tightening craft is also related to thread connection’s quality, if tightening process is not controlled stably, then tightening quality also can cause many uncontrollable results.From the angle of ensuring thread connection reliability, this paper systematically analyzed the thread fasteners’ design and tightening process through the method of combining of the theory and experiment, so as to provide a certain theoretical basis for the reasonable design and choice of thread fasteners and reasonable control of its prestressing force.This paper research content consist of the following several aspects:(1) To study the method of controlling the prestressing force, and based on the stress-strength interference theory, this paper introduced the thread connection reliability’s mathematical principle, and put forward the calculation method of reliability.(2) Through the tightening experiment it got the key impact factors of the torque coefficient, and also put forward the torque coefficient’s control strategy. After analyzed the economic superiority of the reliability design, it illustrated the advantages of reliability design from a technical and economic aspect.(3) To ensure the reliability of tightening process, statistical process control method was used to systematically analysis the thread connection’s tightening process, a reasonable process was put forward to guarantee tightening tools’ precision, and showed the control chart’s drawing process of the static torque.