Study On Fatigue Fracture Property And Life Prediction Of Notched Electroplated Copper Film

In this paper, smooth and notched specimens for free-standing with 11.5μm thickness were produced based on LIGA-like process and fabrication flow of electroplated copper film. Tension-tension fatigue test was carried out. The local stress and strain at notch root was calculated by elastic-plastic finite element method, which was verified by Neuber's method. Based on the analysis of fracture and finite element analysis, the fracture at the notch was determined. On the stress and strain of fracture state, fatigue lives of the notched were predicted. The results showed a good agreement with the test lives by the Dowling damage theory.First, electroplated copper film was made by LIGA-like progress. Tension-tension fatigue test was carried on the SHTMADZU MMT-11N micro-mechanical fatigue testing machine. S-N curve, cyclic stress-strain curve and other fatigue properties were obtained. It was found that fracture occurred near the location of peak point at notch root and the fracture mode was mainly intracrystalline fracture.Then, the local stress and strain at notch root was calculated by FEM. Comparison between FEM and Neuber's results showed that the local stress and strain calculated by FEM can be used to estimate the fatigue life. In FEM analysis, the dangerous area was near the notch root within±14.2 degree region measured from the notch curvature center, which agreed with the experimental observation.Finally, fatigue lives of notched specimen were predicted by several damage models, which were found that it had a better result on considering only the elastic strain. It also found the amplitude of stress had a greater effect on fatigue life and mean stress introduced smaller life prediction results. On the stress and strain of fracture state, fatigue lives of the notched were predicted, distributed between an error factor of 2 line and showed good agreement with the test lives.