Influences of various parameters on shear stiffness of bolted joints subjected to shear load

Abstract

AbstractParameters which affect shear stiffness characteristics of bolted joints subjected to shear load should be elucidated in order to design mechanical structures for functionality focusing not only on their strength and self-loosening but also on their shear stiffness. In this study, we have both experimentally and analytically investigated the behaviors of a bolted joint subjected to shear load and primary parameters which determine the shear stiffness characteristics of bolted joints. The experiments have been conducted applying the shear load four times repeatedly on clamped plates of a bolt/nut assembly with washers. We measured the shear stiffness of bolted joints and the shear load at which the slippage started to occur between the clamped plates. Four types of washers were used in the experiments with different contact areas on the clamped plates in order to reveal the effect of contact area of washers. We also conducted FE analysis under the same conditions. As the results, it was seen that the shear stiffness slightly increased with an increase in the clamp force of bolted joint. The shear stiffness was not influenced by the number of loading cycles. It was also seen that the amount of rotational deformation in the bolted joint depended on the slippage between the clamped plates. Although the rotation deformation was very small until the slippage occurrence, the rotational deformation remarkably increased after the slippage occurred. In general, it is well-known that the joining portion of lap jointed plates by spot welding, for example, slightly and rotationally deformed, but it has never been elucidated that the inclination angle due to the rotational deformation depends on the slippage between the clamped plates in the bolted joint. It was also seen that the shear stiffness until the slippage occurrence increased with an increase in the contacting surface area between the clamped plates. Although we investigated the effect of surface roughness of the clamped plates only in the experiments, we cannot clearly reveal its effect on the shear stiffness. But it is seen from the FE analysis result that the friction coefficient between clamped plates had a slight influence on the shear stiffness. The result shows that the shear stiffness of bolted joint mainly depends not only on the slip resistance between the clamped plates but also on increase of the contact surface between the washers and clamped plates. The results can be applied in order to control the shear stiffness of lap-jointed plates by spot welding and so on.