ABSTRACT
This presentation discusses a method of utilizing Finite Element Analysis (FEA) to determine mean and alternating stresses within bolted joints. This method is particularly useful for evaluating unconventionally designed joints. On preloaded joints, the external load (in this case an alternating load) is shared by both bolts and flanges. Only through FEA can the mean and alternating stress be determined accurately for each component. In order to determine stresses in the joint components, this unique FEA method can be applied. This method involves a forced closed “gap element” to preload the joint.
In the first step of the method, the bolt is loaded and the flange is restrained to simulate actual stress conditions within the joint introduced by the bolt torque, without external load. Then, the bolt and the flange are coupled together through a gap element, so that when a gap is closed by arbitrarily high forces, the same stress conditions are achieved as in the first step.
Now, the alternating load is added, and from resulting stresses, the mean and alternating stress can be determined.
Finally, the fatigue risk can be assessed using conventional cumulative fatigue methodology.
