Numerical life estimation after fatigue failure of a complex component

Failure of a large ethylene‐reciprocating compressor was found to be due to fatigue growth of cracks in the crosshead of one of the cylinders, initiated at material defects near stress raisers. Total fatigue crack growth time was required in order to identify the cause of the failure. The applied stress field near the initiation sites and along fatigue path was estimated using FEM. The stresses were found to vary steeply and become partly compressive along a large part of the fatigue crack path. A weight function based on numerical method was developed, which was able to predict exactly the shape of the crack front during propagation. Fatigue crack initiation was traced to a disassembly 6 months before final failure. This failure was found to be jointly the result of non‐conformities in manufacture and maintenance.