A general method to predict the crack propagation of anodic dissolution corrosion fatigue is developed in this paper. Crack propagation of corrosion fatigue is presented as the result of the synergistic interactions of mechanical and environmental factors, and corrosive environment accelerates crack propagation mainly in term of anodic dissolution. By studying the variation of mechanical energy and electrochemical energy of anodic dissolution during the crack propagation process, an explicit expression of crack propagation rate is derived by the conservation of energy. The comparisons with experimental data demonstrate the validity of the proposed model. Moreover, the applicable upper-limit crack length for steady crack propagation is determined and the crack propagation life is evaluated.
The interfacial molecular structure of materials with different lattice constants is simulated by using the method of molecular dynamics （MD）. Potential of modified analytical embedded atom method （MAEAM） is used for nominterfacial atoms. To simulate the state of interracial atoms, further modifications are applied to the MAEAM potential based on the first- principle simulation results. It is concluded that a small change of potential may greatly influence the interfacial molecular structure. Void and diffusions can be observed in the simulation results. It is also found that the pre-existed dot defects before bonding can decrease the number of interfacial defects greatly, thereby, can increase the strength of the interface.
Dongwei Ren Jinquan Xu 1(School of Naval Architecture and Civil Engineering,Shanghai Jiaotong University,Shanghai 200240,China)
Fracture theory is a classic,but not a well-dealt with,difficulty in solid mechanics. This paper has proposed the concept of characteristic fracture length of materials from the fact that fracture happens with area failure rather than point failure in materials. A unified theory is then proposed,which can be applied both to smooth and defected materials (whether with micro or macro defects). Brittle fracture tests with specimens of different sizes of holes are carried out to examine the fracture theory. It is found that the fracture stresses obtained by experiments agree well with those predicated by the presented fracture theory. Though the brittle fracture is the focus of the paper,the concept of characteristic length can be easily extended to fatigue or other failure problems.
