Critical Conditions For Nano Scale Crack Propagation In Materials By Phase Field Crystal Method

With the rapid development of science and technology, many structural functional nanomaterials have appeared in people’s life. Due to the limitation of material manufacturing equipment and material characterization technology, it is difficult to directly observe the crack growth behavior of the nano scale in the actual research process.With the rapid development of electronic computer, many problems in fracture mechanics of materials can be solved by computer through numerical calculation. The phase field crystal method (PFC) can be carried out from the theoretical research of atomic diffusion time scale and spatial scale changes on the structure of the material. For example, research materials in the structure of dislocation slip and climb, dislocation annihilation between the transition between the internal structure of the material, substrates such as phase field crystal method of material science. The latest cutting-edge research focuses on:the effect of external stress factors into the crystal phase field model, PFC model was established with strain and dislocation dynamics theory, which are applied to the fracture mechanism and mechanical properties of creep failure behavior of material structure, For example Elder use PFC method under applied uniaxial tensile stress crack propagation conditions on the material micro structure simulations conducted a preliminary study. At present, nano scale research on crack concept has been considerable development, and the fatigue crack under external load strain growth under critical conditions and crack propagation behavior, crack bifurcation and internal contact free energy change system of few researches. In view of this, we will use the phase field crystal model (PFC model) to study the critical conditions of crack propagation under the action of single and double axle dynamic loads and static loads. The main results of this study are as follows:1. Structural materials when subjected to an external should force and the occurrence of crack growth, the crack propagation perpendicular to the loading direction in the direction of the external load, load should be less stress on the specimen crack extension rate is obviously lagging behind to load large strain of the specimen.2. The critical strain uniaxial constant strain is larger than the critical strain under biaxial constant strain crack propagation.3. Crack propagation is very sensitive to temperature changes, the lower the temperature, the greater the crack growth resistance, the higher the temperature, the more the thermal vibration atoms, the easier the crack growth.4. After applying dynamic loading system that free energy gradually rise, crack extension hole connected effect and crack dissociation extension phenomena. The strain can be concentrated on the application of the strain.In this study, the phase field crystal method is used to study the crack growth behavior of materials, and the theoretical results are consistent with the experimental results, which have important guiding significance for the design of structural functional materials.