A Finite Element Analysis Of Elasto-plastic Field Near The Tip Of A Crack

First,this article presented the development history and research's actuality of the fracture mechanics.And introduce some theory of the fracture mechanics,including:stress intensity factor, plastic correcting of small scale yield,slip-line theory of elastic-plastic fracture etc.This article developed some the theoretical principle of finite element method,compare some different elements form in finite element method,dicuss the difference between fractal interpolation function in finite element method,choose the best element's form of the elastic-plastic fracture field's finte element calculate programme; Derivation the elementary theory of isoparametric element,choose the best geometry's format of the element.Introduce the Gaussian integral,choose the best number of the Gaussian integral point.And in the introducing for the finte element method,I emphasize introducing the elastic-plastic full scale constitutive relation for the programme.In this article,I used the finte element programme do some works.The principal working of the thesis is as follows:1. Compares the elastic-plastic numeriacl solution with the elastic-plastic analytic solution of Thick-walled Tube, and validate the programme works well.2. Analyse the requests form crack-plate model in finte element's computing,give us the best scales in element division form, element division scale, constringency precision and passivation.3. In the analysis of center cracked plate (CCP) and double edge cracked plate (DECP), I compare the fist term of surrounding crack-tip between CCP and DECP, validate the similitude between CCP and DECP.4. Discuss the crack-tip field of CCP, analysed that when the loading P =0.1P_L,in a small area plastic stress field of crack-tip,the stress is big,and it will changed along with distance from the crack-tip.5.Analyse the infection of different length/width (L/W) scale for the crack-tip field of CCP, validate Leever Radon(1982),Lei and Neale(1997)'s viewpoint:In CCP , due to the stress intensity factor ,when speccimen length is at lease twice the specimen width (i.e. L/ W≥2.0) in elastic condition.And the conclusion is tenable in elastic-plastic condition.I propound hypothesis for this.6. According to the parameters of crackle body, programs is also made to automatic generate input files of finite element computation and draw a figure to the data, it realizes the case of the pretreatment working automation.