Research On The Fracture Based On Digital Image Correlation Method And Numerical Simulation

In this paper,we apply digital image correlation method to study the mechanical properties of gypsum material in the split test.First we programme the calculation program based on digital image correlation theory and use the GPU parallel algorithm to accelerate the program.We studied the displacement field of the gypsum block during the process of cracking and analyzed the properties of some aspect according to the data r ecorded in the test,including the relationship between pressure and displacement,the process of crack propagation and penetration,and the pattern of main crack propagation.Also,some numerical experiments were performed on the ABAQUS and compared to th e test result in order to make a deeper understanding on the constitutive relation of gypsum.First of all,we apply the digital image correlation theory to programme a program which can measure the displacement field according to the photograph based on the C++ language and CUDA parallel programming platform.Calculating the displacement field,strain field and drawing the color map,showing and saving the results is the basic functions of the program.Furthermore,the function of amending the rigid body r otation and pre-treatment and posttreatment are designed depending on the specific demand.A series of gypsum block split test are performed in use of the program and triaxial apparatus,which measured the curve of pressure and displacement and full field displacement.We divided the test process into three stages: the linear elastic stage,the development of plastic and microcracks stage and the crack penetration to destroy stage due to the pressure and displacement curve.We can get the process of the cr ack development,and the change of the displacement field near the crack including the displacement gradient on the both sides of the crack,and even pattern of the springback of the new boundary after the main crack opening,and describe the significant influence on strain calculation while the crack is extending.We analyze the destroy order and the pattern of middle and on both sides of the up and down of the block.In the numerical simulation part,concrete damage plasticity is used to simulate the quas i static loading process.This model can describe the reduction of the modulus while plasticity grow and damage accumulate which accords well with the test.We apply the two-layer viscoplasticity model to simulate the mechanical properties of gypsum in different loading rate in order to reflect the influence of viscidity and loading rate.The numerical simulation results are in good agreement with the test results during different loading rate which indicates the two-layer viscoplasticity model can explain the viscidity of gypsum well.