軸直角方向負荷下でのボルト-ナット締結体のすべり・ゆるみ挙動 : 第2報,限界相対すべり量及びボルト頭部の傾き係数の評価(<小特集>締結・接合・接着部の評価技術)

Abstract

Most of machines and products have many joint portions (e.g. fastening, welding and adhesive joints) for the efficient productivity and maintainability. Especially, the thread joint has been frequently used for these purposes. However, troubles such as loosening of bolt and fracture or failure at joint portion have often arisen, thus many attentions have been paid on the improvement of the strength and reliability of the thread joint. In this paper, we present the investigated results of the sliding and the loosening behavior of bolt-nut fastener under the transverse loading condition. Firstly, the critical relative slippage (S_<cr>), less than the displacement in which the thread joints can keep the fastening, is experimentally obtained from cyclic loading test. When the relative slippage exceeds S_<cr>, the Fastening preload rapidly decreases. Then, this critical relative slippage is estimated according to the theoretically obtained equation considering the bending deformation of bolt and the geometrical constraint condition. The inclination compliance (k_w) that represents the pseudo-rigidity at the bolt head portion in this equation is evaluated by comparing the experimental result with the corresponding analytical one. In consideration of the nonlinearity of k_w with respect to the Fastening preload, the critical relative slippage is well determined by the formula for arbitrary Fastening preload.