Fracture Mechanics Analysis of 2-D FGMs by a Meshless BEM

2006 ◽  
Vol 324-325 ◽  
pp. 1165-1172 ◽  
Author(s):  
Chuan Zeng Zhang ◽  
Xiao Wei Gao ◽  
Jan Sladek ◽  
Vladimir Sladek

This paper presents a fracture mechanics analysis in continuously non-homogeneous, isotropic, linear elastic and functionally graded materials (FGMs). A meshless boundary element method (BEM) is developed for this purpose. Young’s modulus of the FGMs is assumed to have an exponential variation, while Poisson’s ratio is taken as constant. Since no simple fundamental solutions are available for general FGMs, fundamental solutions for homogeneous, isotropic and linear elastic solids are used in the present BEM, which contains a domain-integral due to the material non-homogeneity. Normalized displacements are introduced to avoid displacement gradients in the domain-integral. The domain-integral is transformed into a boundary integral along the global boundary by using the radial integration method (RIM). To approximate the normalized displacements arising in the domain-integral, basis functions consisting of radial basis functions and polynomials in terms of global coordinates are applied. Numerical results are presented and discussed to show the accuracy and the efficiency of the present meshless BEM.

2006 ◽  
Vol 324-325 ◽  
pp. 1261-1264 ◽  
Author(s):  
Xiao Wei Gao ◽  
Chuan Zeng Zhang

In this paper, an isotropic elastic damage analysis is presented by using a meshless boundary element method (BEM) without internal cells. First, nonlinear boundary-domain integral equations are derived by using the fundamental solutions for undamaged, homogeneous, isotropic and linear elastic solids and the concept of normalized displacements, which results in boundary-domain integral equations without an involvement of the displacement gradients in the domain-integral. Then, the arising domain-integral due to the damage effects is converted into a boundary integral by approximating the normalized displacements in the domain-integral by a series of prescribed radial basis functions (RBF) and using the radial integration method (RIM). The damage variable used in the paper is the ratio of the damaged area to the total area of the material, and an exponential evolution equation for the damage variable is adopted. A numerical example is given to demonstrate the efficiency of the present meshless BEM.


Author(s):  
Licheng Guo ◽  
Zhihai Wang ◽  
Naotake Noda

This study aimed to develop a method to build a ‘bridge’ between the macro fracture mechanics model and stochastic micromechanics-based properties so that the macro fracture mechanics model can be expanded to the fracture mechanics problem of functionally graded materials (FGMs) with stochastic mechanical properties. An analytical fracture mechanics model is developed to predict the stress intensity factors (SIFs) in FGMs with stochastic uncertainties in phase volume fractions. Considering the stochastic description of the phase volume fractions, a micromechanics-based method is developed to derive the explicit probabilistic characteristics of the effective properties of the FGMs so that the stochastic mechanical properties can be combined with the macro fracture mechanics model. A thought for choosing the samples efficiently is proposed so that the stable probabilistic characteristic of SIFs can be obtained with a very small sample size. The probability density function of SIFs can be determined by developing a histogram from the generated samples. The present method may provide a thought to establish an analytical model for the crack problems of FGMs with stochastic properties.


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