Concise Principle Of Crack Propagation And The Theory Of Tangent Modulus In Fracture Mechanics

This thesis presents a new analysis and simplification to the energy principle of crack propagation by using the concept of crack-circle and strain energy principle in elastic mechanics. The analytic models of crack propagation motivity and its length measurement and angle measurement, the displacement of crack propagation motivity and the angle of crack propagation motivity, are builded. The consistency of the energy criterion and the stress intensity factor criterion to Model I crack is discussed concisely, and the new method to calculate linear critical fracture stress is presented.The basic frame of the theory of tangent modulus in fracture mechanics is builded, and the new method of tangent modulus factor to calculate nonlinear critical fracture stress is presented. The limitation of COD approach is proved in theory by using the relationship of the PL(C, E) Model of the method of tangent modulus and the COD experience formula. At the same time, this thesis shows that the PL(c, m) Model of the method of tangent modulus factor is clear, convenient and more exactitude by comparing with present COD approach.