Fatigue damage in fieldshapers used during electromagnetic forming and welding processes at high frequency impulse current

Fieldshapers used in electromagnetic forming and welding processes are prone to have fatigue damage. During each test, impulse current passes through the coil that induces an eddy current cycle and a cyclic Lorentz force on the fieldshaper. Thus, the failure of the fieldshapers during service is associated with the cyclic loading conditions during a decaying high frequency electric current pulse. Repetition of the current pulse that causes the damage and eventually results in a failure which is similar to that occurs during a fatigue problem. Therefore, firstly mechanical and fatigue properties of the new material proposed for the fieldshaper (Siclanic alloy) were characterized. Then various fatigue loading cases with input voltages of 6-8.5 kV were investigated to predict the influence of dynamic cyclic loading on the fatigue damage. This study provides a clear understanding of the fatigue damage due to electromagnetic loading and establishes a linear correlation to predict the life cycle for an input electric current. The predicted fatigue damage locations are also in good agreement with the crack formation and their distribution on the filed shapers used in service.