Ductile Fracture Prediction of Automotive Suspension Components

Characterization of the plastic and ductile fracture behavior of a ferrous casting commonly used for the steering knuckle of an automotive suspension system is presented in this work. Ductile fracture testing for various coupon geometries was conducted to simulate a wide range of stress states. Failure data for the higher stress triaxiality were obtained from tension tests conducted on thin flat specimens, wide flat specimens and axisymmetric specimens with varying notch radii. The data for the lower triaxiality were generated from thin-walled tube specimens subjected to torsional loading and compression tests on cylindrical specimens. The failure envelopes for the material were developed utilizing the test data and finite element (FE) simulations of the corresponding test specimens. Experiments provided the load-displacement response and the location of fracture initiation. FE simulations were conducted to calculate all the stress states, Lode angles and strain components at the point of fracture initiation. Finally, comparisons of the predicted fracture load with data from physical tests are presented for a load case of the steering knuckle, which introduces complex stress states.