| An anisotropic model of continuum damage mechanics has been developed to predict the creep-fatigue life of solder joints. With the help of the finite element method, the stress, strain and damage fields of the time-dependent and temperature-dependent solder can be obtained. The main advantages of this model include: (1) It can predict the initial crack location and time and the subsequent crack growth paths. (2) The damage analysis is almost the same as in traditional viscoelastic finite element analysis. (3) It can be applied to a complex structure with any loading. (4) It provides a full-field damage investigation of the structure. This damage theory can be used for various solder joints and also can be applied to analyze the creep-fatigue problems of other ductile and temperature-dependent materials. Other approaches such as fatigue formula methods and J-integral analyses are also discussed in this study. All failure criteria discussed herein can be treated by the finite element program included in the thesis.;Over ninety experiments including uniaxial creep tests, uniaxial fatigue tests, tension-torsion tests, moire tests and bimaterial tests were performed to validate the new model. Furthermore, the straddle board experiments from reference (128) were also used for comparison. These validations and comparisons indicate that this model can adequately predict crack growth paths and fatigue lives of solder joints.;A finite element program has been established in this study. The program includes linear elastic analysis, elastic-plastic analysis, viscoelastic analysis, viscoplastic analysis, damage analysis and contact analysis. |
