tailieunhanh - Calculation of fracture mechanic parameters via fem for some cracked plates under different loads

This paper describes some results in analyzing cracked plates via FEM based on the procedures in CASTEM 2000 [1]. The basic methods for computing the crack parameters by the finite element analysis are presented. Some programs written by GIBIAN languages to solve problems for cracked plates are given. | Vietnam Journal of Mechanics, VAST, Vol. 28, No. 2 (2006), pp. 83 - 93 CALCULATION OF FRACTURE MECHANIC PARAMETERS VIA FEM FOR SOME CRACKED PLATES UNDER DIFFERENT LOADS NGO HUONG NHU AND NGUYEN TRUONG GIANG Institute of Mechanics , VAST, 264 Doi Can, Hanoi, Vietnam Abstract. This paper describes some results in analyzing cracked plates via FEM based on the procedures in CASTEM 2000 [1]. The basic methods for computing the crack parameters by the finite element analysis are presented. Some programs written by GIBIAN languages to solve problems for cracked plates are given. In possible cases, the numerical results are composed with analytical solution or testing result that gives a good agreement. The influence of plate configurations, the crack length, the external load type on the crack characteristic values are considered. The numerical analysis for inclined crack at angle and in arbitrary position of plate, the crack at hole in the plate, the crack of gravity dams are realized. The given results and programs can be applied to practical problems for controling the brittle failure state of a structure. 1. THE MAIN METHODS FOR CALCULATION OF FRACTURE MECHANIC PARAMETERS VIA FEM The determination of fracture mechanics parameters as Stress Intensity Factors (SIF), energy release rate G, J - integral Rice and Crack Opening Displacement (COD) plays an important role in fracture analysis. By comparing these parameters with critical values one can estimate the brittle failure state of structures. Nowaday, the crack analysis is founded on three different following methods. Estimation of stress intensity factors by extrapolation of displacements or stresses The stress intensity factors (SIF) Kr can be defined as a function of r [2]: Kr= ( 2µ ) x+1 ff:7r - v(B = 7r), r where v(B) is Westergard displacement solution: v(B) = : : ff- ((2x + 1) sin~ - 3 sin ; ) + ~~r ff- ((2x - 3) cos~+ cos 3; ) ; 3- lJ x = l+v ' () In FEM the function Kr(r), Kn(r) are .