Low Cycle Fatigue Assessment of Nodular Cast Iron GJS-500-7

Sammanfattning

Nodular cast iron is widely used at Scania in a variety of components. This thesis aims to assessthe low cycle fatigue properties of the nodular cast iron GJS-500-7, a widely used cast iron gradeat Scania. A total of 40 uni-axial test specimen were cut out of 5 serially produced Scania parts.Monotonic uni-axial tests were performed to verify the casting process and enabled the implemen-tation of a new material curve in Abaqus. A large number of uni-axial low cycle fatigue tests wereperformed for a variety of strain ratios. A combined Basquin and Coffin-Manson axial fatiguemodel was fitted and three separate kinematic hardening models were fitted by experimental dataand implemented into Abaqus. Low cycle fatigue testing in force-control was performed simulta-neously for verification of cyclic models. The performance of the three models were evaluated inthe ability to recreate the strain in force testing. All three kinematic models, linear, multi-linearand Chaboche, failed to recreate the mean strain from the ratcheting effect which occurred in theforce-controlled testing, but were sufficient in their ability to capture the amplitude in the strain-time signals. The multi-linear model was not stable for this analysis. The linear model performedthe best and is recommended for use in cyclic analysis. An acceptance criterion for total strainamplitude in GJS-500-7 can not be fully recommended, however recommendation is made forthe use of strain-controlled alternating points which have been used historically for dimensioningagainst low cycle fatigue.