熱負荷を受けるボルト締結体の軸力と曲げモーメントの簡易推定法

抄録

Bolts and nuts are the most commonly used machine elements to clamp multiple parts and structural members. When a bolted joint is subjected to thermal load, the bolt preload varies greatly or to some extent and the bending moment may be generated in the bolt body, due to differential thermal expansions among clamped parts. The variations of bolt preload and bending moment sometimes cause failure or fracture of the bolted joint, and it may lead to fatal accidents of machines and structures. In this paper, a simplified method for estimating the variations of bolt preload and bending moment with time is proposed using elementary theory of solid mechanics. The required input data are the surface temperatures around the bolted joint, which can be measured by thermography without touching the target structure. The effectiveness of the proposed method is demonstrated by comparing the estimated values with those obtained by three-dimensional Finite Element Analysis.