Evaluation of the Tightening Process of Elastic Angle Control Method and Proposal of a Practical Tightening Operation

Abstract

Various clamping methods are used to tighten bolted joints according to its configuration, bolt size, the magnitude of bolt preload, etc. Elastic angle control method is sometimes applied to tighten important structures such as large-scaled diesel engines, where bolt preloads need to be controlled with high accuracy. Its tightening operation is explained in JIS B 1083. However, the relationship between axial bolt force and nut rotation angle and the guideline for the amount of snug torque, shown in JIS, are not necessarily sufficient from the practical point of view. In this paper, an equation relating axial bolt force and nut rotation angle is proposed to improve the accuracy of Elastic angle control method, in which the effects of interface stiffness due to surface roughness and the inclined angle existing at nut loaded surface are incorporated, and its tightening process is comprehensively studied by experiments. Based on the derived equation, a practical tightening guideline is proposed, which is effective when Elastic angle control method is used together with torque control method.