被締結物がクリープ変形するねじ締結体における軸力低下に及ぼす平座金の効果

抄録

Recently, reduction in weight of automobiles is required to solve environmental issue. In case of clamped parts made of lightweight material such as Magnesium or resin for bolted joints, creep deformation occurs in a high temperature environment, and the axial bolt tension decrease. Conventionally, a plain washer has been used as one of the methods for preventing from the deformation of contact surface. In this study, investigated the method of suppressing axial bolt tension reduction due to creep with a plain washer in a bolted joint been investigated by experiment and FEM analysis. In the case of using a plain washer, the residual rate of axial bolt tension and residual axial bolt tension was improved. The plain washer dimension was changed. Increasing the outer diameter of plain washer, the residual axial bolt tension was improved and axial bolt tension reduction increased. Increasing the thickness of plain washer, the progression of deformation at contact surface could be suppressed. Contact surface deformation by creep is considered to be related to contact surface stress distribution and stress inside the bolted joint. It was found that when the contact surface stress is large at the outer diameter side of the contact surface, the stress near the bolt hole inside the bolted joint decreases and the creep strain decreases. From these results, it was possible to grasp the influence of the plain washer in the bolted joint causing creep deformation and to define the design guidelines.