A New Computer Tracking Method for Crack Tip Propagation

According to the COD (crack opening displacement) criterion of elasticity-plasticity fracture mechanics, we can decide whether the structures including crack are safe or not. However, the theory basis of the COD criterion, which is Dugdale model, is not agree with the fact crackle. In order to research the displacement field around the fact crack tip, tracking the location of crack tip is very important. So, a new computer tracking method is provided to track the crack tip and measure the movement curve of the crack peak. Because the crack opens slowly, the similary between the front and back images of crack tip propagation is high. The computer tracking method based on the optimum image correlation algorithm is feasible. By the tracking experiment of the samples of thin paper and lumber block including the premade crack under the action of gradual loadings, the crack tip is successfully tracked. And the moving curve of the crack tip is also obtained. In this way, the computer tracking method provides a new dynamic experiment means to quantitatively analyze the stress-strain fields around the crack tip according to the images of displacement fields around the crack peak at the next work.