P. H. Melville

Bio: P. H. Melville is an academic researcher. The author has contributed to research in topics: Brittleness & Compression (physics). The author has an hindex of 1, co-authored 1 publications receiving 13 citations.

Modeling of crack initiation, propagation and coalescence in rocks

Abstract: One of the most successful criteria proposed so far to describe the initiation and propagation of cracks under quasi-static loading in rock-like materials is a stress-based criterion developed by Bobet (Fracture coalescence in rock materials: experimental observations and numerical predictions. Sc. D, Thesis, Massachusetts Institute of Technology, 1997) which is embedded in FROCK, a Displacement Discontinuity code that was developed by the rock mechanics group at MIT. Even though the predictions obtained with this criterion generally correspond to the experimental results, there are cases in which the quasi-static crack propagation results obtained with FROCK are not satisfactory. For this reason, a qualitative study using the Finite Element code, ABAQUS, was conducted to analyze stress-, strain- and energy-based criteria used for modeling crack development. Based on the ABAQUS relative quantitative analysis, it was found that the strain- and stress-based criteria may be more appropriate than the energy-based criterion to model quasi-static crack development. Thus, a strain-based and a normal stress-dependent criterion were implemented in FROCK. The cracking patterns obtained with these proposed criteria were compared with those obtained using Bobet’s original stress-based criterion and with experimental observations made in molded gypsum specimens. The proposed strain-based criterion implemented in FROCK appeared to yield better results than Bobet’s stress-based criterion. The influence of the friction angle ( $$\upvarphi $$ ) on the cracking patterns was studied with the proposed normal stress-dependent criterion and showed that friction angles closer to $$0^{\circ }$$ yielded the best results, which may indicate that, at least for the microscale, the critical shear stress at which rock fails does not depend upon the normal stresses applied.

Crack propagation in concrete under compression

Abstract: Mixedmode crack initiation and propagation starting from the aggregatematrix interface in concrete under uniaxial compression was investigated using fracture mechanics approach, finite element mode...

Parametric quadratic programming method for elastic contact fracture analysis

Abstract: A solution procedure for elastic contact fracture mechanics has been proposed in this paper. The procedure is based on the quadratic programming and finite element method (FEM). In this paper, parametric quadratic programming method for two-dimensional contact mechanics analysis is applied to the crack problems involving the crack surfaces in frictional contact. Based on a linear complementary contact condition, the parametric variational principle and FEM, a linear complementary method is extended to analyze contact fracture mechanics. The near-tip fields are properly modeled in the analysis using special crack tip elements with quarter-point nodes. Stress intensity factor solutions are presented for some frictional contact fracture problems and are compared with known results where available.

Stress intensity factor analysis of friction sliding at discontinuity interfaces and junctions

Abstract: A stress intensity factor (SIF) analysis for two-dimensional fractures with frictional contact (crack friction) is presented. This analysis is carried out using the symmetric-Galerkin boundary element method, and a modified quarter-point crack tip element. As in case of non-contact fracture, it is shown that highly accurate SIFs can be obtained, even with the simple Displacement Correlation SIF technique. Moreover, with the modified crack tip element, the mesh on the crack does not need to be excessively refined in order to achieve high accuracy. This meshing advantage is especially important in the context of the nonlinear frictional contact problem, as the computing time for the iterative process strongly depends on the number of elements used. Several numerical examples are presented and the SIF results are compared with available analytical or reference solutions.