FEM Stress Analysis of Mechanical Behaviors in Bolted Joints Under External Loadings

In designing bolted joints, it is necessary to know the stress-changes in bolt loads and the stress distribution at the interfaces between clamped parts when external load is applied to the joints. The ratio of variation of bolt load to external load is called the load factor. The load factors have been studied. However, the load factors for bolted joints using bolt with flange have not been studied. In the present paper the mechanical behaviors of bolted joints in which bolt with flange are used such as the load factor and the contact stress distributions at the bearing surfaces are analyzed using Finite Element Method calculations in the case where the clamped parts are two hollow cylinders. The effects of factor such as flange slope angle on the value of the load factor, the contact stress distribution and permanent set at the bearing surfaces are examined. Variation of permanent set at the bearing surface when the external load is applied has not studied. In the experiments, to examine the load factor for the joints using a bolt/nut with flange, the variations of bolt load under the external loading were measured. The calculated results of the load factor show a fairy good agreement with the measured results. In addition, engineering formula for calculating the spring constant of bolt and nut with flanges are proposed.