International Journal of Fracture, Vol, 139 No. 1, pp. 91-117, 2006
D.J. Shim, G.H. Paulino, R.H. Dodds Jr.
Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Newmark Laboratory, 205 North Mathews Avenue, IL 61801, USA
This paper describes elastic-plastic crack growth resistance simulation in a ceramic/metal functionally graded material (FGM) under mode I loading conditions using cohesive zone and modified boundary layer (MBL) models. For this purpose, we first explore the applicability of two existing, phenomenological cohesive zone models for FGMs. Based on these investigations, we propose a new cohesive zone model. Then, we perform crack growth simulations for TiB/Ti FGM SE(B) and SE(T) specimens using the three cohesive zone models mentioned above. The crack growth resistance of the FGM is characterized by the J-integral. These results show that the two existing cohesive zone models overestimate the actual J value, whereas the model proposed in the present study closely captures the actual fracture and crack growth behaviors of the FGM. Finally, the cohesive zone models are employed in conjunction with the MBL model. The two existing cohesive zone models fail to produce the desired K-T stress field for the MBL model. On the other hand, the proposed cohesive zone model yields the desired K-T stress field for the MBL model, and thus yields J R curves that match the ones obtained from the SE(B) and SE(T) specimens. These results verify the application of the MBL model to simulate crack growth resistance in FGMs.
KEY WORDS: Elastic-plastic crack growth; Crack growth resistance curve; J-integral; Functionally graded material (FGM); Cohesive zone model; 3-D finite element analysis; Modified boundary layer model