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Abstract

The chipping process in a brittle material subjected to a uniformly applied edge load has been investigated. The present analysis extends earlier work by recognizing that as the chip is formed it may bend and change the loading at the crack tip. This geometry change introduces a nonlinear effect and has significant influence on the phenomenon. The nonlinear effect was demonstrated by incorporating it into an analytical model for a crack propagating along an interface parallel to the free surface. A finite-element analysis was then conducted to examine the crack trajectory formed in a homogeneous material. This numerical analysis showed that the crack reaches a maximum depth, and then deviates back to the free surface to form a spall. The form of this trajectory results from the additional bending moment acting at the crack tip induced by the bending of the chip and the consequent displacement of the applied load. The length of the spall was found to be approximately proportional to the square root ofÊd 5/2 /K IC , where K IC is the fracture toughness of the material,Ê is the appropriate modulus of the material, and d is the depth over which the edge load is applied.

Mechanism of burr accumulation and fracture pit formation in ultraprecision microgroove fly cutting of crystalline nickel phosphorus

“…As shown in figure 7(a), a crack initiates and propagates to a maximum depth, then deviates back to the free surface to form a spall. The predicted trends have been confirmed through finite-element calculations by Chui et al [29]. Discontinued fracture pits are generated with the cutting tool, as shown in (figure 7(b)).…”

“…The brittleness of the Ni-P plating is enhanced through crystallization and defects of the fracture pits are supposed to be generated with a relatively high feed rate for the increasing cutting thickness in microgroove fly cutting. The nonlinear effect of the crack growth and the penetration law affects the spall formation in brittle material removal [29,30]. As shown in figure 7(a), a crack initiates and propagates to a maximum depth, then deviates back to the free surface to form a spall.…”

Machinability of the Thermoplastic Polymers: PEEK, PI, and PMMA

“…Due to the large elastoplastic deformation and thermomechanical coupling phenomenon, cutting polymers with high dimensional accuracy and surface quality is challenging. Chiu et al [25] studied the crack trajectory during the cutting of PMMA based on linear elastic fracture mechanics. According to their results, the polymer exhibits complex viscoplastic behavior rather than pure linear elastic behavior.…”

Evaluations on Ceramic Fracture Toughness Measurement by Edge Chipping

“…The shaded volume in Figure 1a shows a conchoidal-shaped chip, formed after fail-ure. The chipping method used to fabricate stone tools originated from the Stone Age [39][40][41], and later on, Almond [42] first discovered the constitutive linear relationships between L-h and W-h, paving the way for successive applications of chip geometrical similarity in glass and ceramics investigations [30,[43][44][45][46]. The chip geometrical similarity may build up a connection between the indentation force and material's crack morphology, which facilitates the measurement of material fracture toughness.…”

“…Therefore, the indenting force can be utilized to investigate the internal crack mechanism in terms of the crack features. The straightforward relationship between peak chipping force and indenting distance has been set up by applying the cantilever beam model with a pre-crack at the end point of the indenting distance [39,44,45]. Cotterell [39] built up a force-distance relation using a transited point load and bending moment, considering modes I and II stress intensity factors.…”