Cross With Cracks In Three-point Bending Beam Dynamic Stress Intensity Factor, Weight Function Method

Weight function method simplifies considerably the process of solving for stress intensity factors. The important feature of the weight function is that it depends only on the geometry of the cracked body. If the weight function is known for a given cracked body, the stress intensity factor due to any load system applied to that body can be determined by using the same weight function. Developing a simple and efficient method can be applied to many complex engineering issues.In this thesis, a new method is presented to calculate the dynamic stress intensity factors of the three-point bending beam with the spreading-open type crack. Firstly, the equations for stress intensity factors under two reference loading conditions are applied on, and weight function for beam containing an edge crack can be worked out. Secondly, the history and distribution of dynamic stresses in the three-point bending beam are derived by vibration analysis. Finally, the dynamic stress intensity factors equations for beam with an edge crack subjected to impulsive load are given in dynamic weight function method. And the law of the stress intensity factor is got when it changes with the crack length.In order to be verified easily, the numerical computation is carried out with ANSYS software at the same time. A two dimensional finite element analysis of three-point bending beam based on FEM has been carried out study the dynamic stress intensity factors. The model of three-point bending sample is built to get the crack opening displacement of different sample dimension. The dynamic stress intensity factor can be calculated from the crack opening displacement by FEM at different time. The results of dynamic weight function analysis indicate that the precision of the dynamic stress intensity factor is satisfactory and this method can simplify calculation.Moreover, loading rate have a great impact on the dynamic stress intensity factors. We will develop an in-depth study of the relationship between the dynamic stress intensity factors and loading rate based on current research. Computer programs are edited, several examples are computed.