The component under design in this example is a lug assembly which is welded onto a base plate and is loaded in the opposite direction by a cyclic load acting at the top of the lug. The finite element analysis was carried out to simulate the load applied to the assembly during normal operation. (A sinusoidal distributed load variation was applied around the hole.) The design life objective is 100 years of service.

Now that all three major fatigue life prediction methods have been introduced, this exercise will use all three methods of fatigue analysis to analyze various parts of the lug assembly. Namely, you will use the Total Life approach to determine the useful life of the welded connection. For the non-welded part, you will use the Crack Initiation approach to investigate crack formation due to stress concentrations at the hole followed by Crack Growth. This will also illustrate the different fatigue life design philosophies.

Since you should be quite familiar with the job setup procedure by now, only brief explanations are provided in this exercise. To begin, open a new database and call it lug_weld. Import the MSC Nastran model and results using the file lug_weld.op2 as has been done in previous exercises.