On the Deformation and Interface Pressure Distribution of the Bolted Joint with the Hexagon Socket Head Cap Screw

Abstract

In this paper, the relationships between the counterbore size and the deformation or interface pressure distribution of the bolted joint with a hexagon socket head cap screw are considered in detail by the Finite Element Method using a model of three contact bodies. The following results are found. (1) The smaller counterbore depth makes larger the deformation of the top surface of the jointed element because of the local deformation by the pressure at the bolt head bearing surface. (2) The smaller bearing surface height of the counterbore makes larger the concentration of the pressure distribution upon the circumference of the bolt hole because of the local deformation of the joint interface. (3) Depending upon purposes to improve the deformation or interface pressure distribution, it is more effective to enlarge the thickness of the jointed element with the enlargement of the counterbore depth or bearing surface height of the counterbore. (4) The effective area of the connecting force becomes minimum at about O. 6 of the ratio of the bearing surface height to the jointed element thickness. (5) A graphic method is proposed which can be guide for design of bolted joints with cap screws.