Mechanical Properties And Low Cycle Fatigue Life Of Solder Under Multiaxial Loading

With high precision, quick response, low consume and convenient operation, the micro type tension-torsional fatigue testing machine can be used for mechanical property tests of metal and other materials. The testing machine software were developed to control the axial and torsional movement at the same time by Delphi. The software can control the load and the position of the machine and gather the test data.In this paper, pure tension and pure torsional test, torsional fatigue test and multiaxial ratcheting test were conducted on 63Sn-37Pb and Sn-0.7Cu. The result have shown that the stress-strain relationships, yield stress, shear yield stress, tensile strength, shear strength of the solders have strong strain rate-dependence. But the elastic modulus and shear modulus have not apparent strain rate-dependence. The solders are shear fracture and cyclic softening materials. The axial stress and shear strain amplitude affect the ratcheting strain and the fatigue life in the multiaxial ratcheting test greatly.It was shown that equivalent strain approach and some critical plane approaches gave life prediction on unsafe side for the solder with ratcheting strain. Without considering the ratcheting strain, these approaches can't be used to predict fatigue life of solder in multiaxial ratcheting test. Considering the ratcheting strain, the Coffin model gave good prediction, and most of the predicted values fell within a scatter band of 2.