Mechanical Properties And Fatigue Damage Studies On SnAgCu Lead-free Solder

In this paper, uniaxial tension experiments at different temperatures and different strain rates and low cycle fatigue experiments at regular temperature on SnAgCu lead-free solder were carried out to study separately the mechanical properties and fatigue damage of the material.Uniaxial tension test results showed that the ultimate tensile strength, yield stress and saturation stress of the material have strong correlation with temperature and strain rate. These three stress with temperatures and strain rates were fitted separately with experimental data by using the least square method, and the relationships between stress and temperatures and strain rates were calculated. There were some work hardening features on at regular temperature and high strain rates. However, there were softening features on for the most of uniaxial tension experiments. Because of the strong correlations with temperatures and strain rates of the SnAgCu solder, this paper had the Anand model to characterize stress-strain relationships in the experimental process. Based on the experimental data, nine parameters of the Anand model was calculated. Finally, comparisons were made between the Anand calculate stress-strain curves and experimental curves. It showed that Anand model could characterize the stress-strain behavior at different temperatures and strain rates.Low cycle fatigue tests were conducted at regular temperature, different strain range and loading frequencies using total strain controlled. Since the internal organization of the material altered during the experiment process, properties of the material would also alter. This would result in the reduction of the max stress of each cycle. Then the damage value was calculated from the reduction of the stress amplitude. The damage values calculated from experimental data were analyzed fully and fitted with damage evolution model. Final results showed that the damage evolution could well simulate the experimental data for the total strain range of1%, but not well for the total strain range of2%. The reason is that for the total strain range1%, external factors could not affect the damage evolution of the material significantly, while for the total strain range of2%, external factors had unignorable influences on the damage evolution of the material.