Failure analysis of loom crankshafts in textile industry by fretting-fatigue

One of the most important machine elements of industrial looms are the crankshafts. Those el-ements are considerably large (3.6 m length in this case) and typically designed for infinite life. Nevertheless, this paper presents the results of the failure analysis performed on several crank-shafts from synthetic canvas looms. Three fractured crankshafts were reported during the last year. The fractured components were analyzed based on material characterization methods, hardness measurements, stress calculations and finite element modeling to identify if the crankshafts were properly designed for fatigue applications. The finite elements model was coherent with the static and dynamic loads calculations, according the Von Misses criterion the static safety factor was 30 while the fatigue safety factors was 3.5. The failure occurred due to fatigue initiated by fretting induced by several root causes. Three main causes were identified, inadequate heat treatment, material selection problems and the inadequate bushing adjustment that induced the heating and superficial deformation and consequently the fretting corrosion.