Effects of Accuracy of the Nut Bearing Surface on Tightning Condition of Hollow-Type Bolted Joint. 1st Report. Relationship between Accuracy of the Nut Bearing Surface and Strain Distribution in the Axial Direction of Hollow-type Bolt.

Abstract

In order to accurately measure axial tension in bolted joint at the initial tightening and to evaluate the change in the axial tension in the joint, it is important to clarify the strain distribution of the cylindrical part tightened initially. As a first step, the effects of form accuracy of the nut bearing surface on tightening performance were investigated by FEM analysis and experiments. The obtained results were as follows. Peripheral strain distribution on the internal surface of hollow-type bolted joint is affected by the form accuracy of the nut bearing surface. The strain distribution depends on the height and number of asperities as a model of the height of summit and the number of waviness on the nut bearing surface. The trends of analytical results by FEM approximately agree with those of the experimental results. The effect of form accuracy on the range of strain distribution can be classified into three regions due to the height of asperities. It is found that as a guide for the design of bolted joints, the methods with FEM and with correlation coefficient are useful for the classification of the form accuracy.