Numerical simulation of the fracture process in cutting heterogeneous brittle material

Abstract

SUMMARYThe process of cutting homogeneous soft material has been investigated extensively. However, there are not so many studies on cutting heterogeneous brittle material. In this paper, R-T 2D (Rock and Tool interaction), based on the rock failure process analysis model, is developed to simulate the fracture process in cutting heterogeneous brittle material. The simulated results reproduce the process involved in the fragmentation of rock or rock-like material under mechanical tools: the build-up of the stress field, the formation of the crushed zone, surface chipping, and the formation of the crater and subsurface cracks. Due to the inclusion of heterogeneity in the model, some new features in cutting brittle material are revealed. Firstly, macroscopic cracks sprout at the two edges of the cutter in a tensile mode. Then with the tensile cracks releasing the confining pressure, the rock in the initially high confining pressure zone is compressed into failure and the crushed zone gradually comes into being. The cracked zone near the crushed zone is always available, which makes the boundary of the crushed zone vague. Some cracks propagate to form chipping cracks and some dip into the rock to form subsurface cracks. The chipping cracks are mainly driven to propagate in a tensile mode or a mixed tensile and shear mode, following curvilinear paths, and finally intersect with the free surface to form chips. According to the simulated results, some qualitative and quantitative analyses are performed. It is found that the back rake angle of the cutter has an important effect on the cutting efficiency. Although the quantitative analysis needs more research work, it is not difficult to see the promise that the numerical method holds. It can be utilized to improve our understanding of tool-rock interaction and rock failure mechanisms under the action of mechanical tools, which, in turn, will be useful in assisting the design of fragmentation equipment and fragmentation operations.

Numerical Studies on Chip Formation in Drag-Pick Cutting of Rocks

“…Stavropoulou (2006) simulated the cutting process as plane strain condition, both in PFC2D as destructive process and FLAC2D as steady state process. Other attempts to simulate the rock cutting using discrete element modeling include the development of R-T 2D by Liu et al (2002). During rock cutting simulation using R-T 2D process of stress field build-up, formation of a crushed zone, chip formation, crater formation and formation of sub-surface cracks were observed.…”

Numerical simulation and fractal analysis of mesoscopic scale failure in shale using digital images

“…Specifically, the I value was used for threshold segmentation. According to the strain equivalence principle, the constitutive relation for damaged material can be obtained from the nominal stress in the material (Liu et al, 2002;Zhu et al, 2005;Wang et al, 2012a,b;Zuo et al, 2015) :…”

A numerical cutting model for brittle materials using smooth particle hydrodynamics

“…However, in the case of brittle materials, it is hard to simulate cutting with the Lagrange method that was used in those numerical cutting models, due to the large deformations and tangled mesh seen in brittle workpieces. There is a need to develop numerical cutting models that are able to simulate the discontinuous chips and crack propagation that are characteristics of the brittle material cutting process [8,9].…”