Thermoresponsive Toughening with Crack Bifurcation in Phase-Separated Hydrogels under Isochoric Conditions

The surface of an elastic half space is subjected to sudden antiplane mechanical disturbances. Crack initiation and subsequent crack instability are examined via two idealized problems; the first is concerned with instantaneous crack bifurcation and the second with instantaneous skew crack propagation. In either problem, crack propagation occurs at a constant subsonic velocity under an angle κπ with the normal to the surface. For the externally applied disturbances that are considered here, and for contstant crack-tip velocities, the particle velocity and τθz are functions of r/t and θ only, which allows Chaplygin’s transformation and conformal mapping to be used. The problems can then be solved using analytic function theory. For various values of the angle of crack propagation, the dependence of the elastodynamic stress intensity factors on the crack propagation velocity is investigated. For certain specific geometries, fully analytical solutions are derived to provide check cases.

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Influence of temperature rise at the crack tip on crack bifurcation

International Journal of Fracture ◽

10.1007/bf00020274 ◽

1984 ◽

Vol 24 (1) ◽

pp. R23-R32 ◽

Cited By ~ 3

Author(s):

V. G. Ukadgaonker ◽

S. K. Chadda ◽

S. K. Maiti

Keyword(s):

Temperature Rise ◽

Crack Tip ◽

Influence Of Temperature ◽

Crack Bifurcation

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Modelling of Crack Bifurcation in Laminar Ceramics with Large Compressive Stress

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.488-489.130 ◽

2011 ◽

Vol 488-489 ◽

pp. 130-133

Author(s):

Michal Kotoul ◽

Oldřich Ševeček ◽

Tomáš Profant

Keyword(s):

Crack Propagation ◽

Compressive Stress ◽

Expansion Method ◽

Bimaterial Interface ◽

Matched Asymptotic Expansion ◽

Straight Crack ◽

Crack Penetration ◽

Micro Cracks ◽

Finite Fracture Mechanics ◽

Crack Bifurcation

Ceramic laminates designed with strong interfaces have shown crack growth resistance (R-curve) behaviour through microstructural design (e.g. grain size, layer composition) and/or due to the presence of compressive residual stresses, acting as a barrier to crack propagation. The goal of the contribution is to model the mechanism of crack bifurcation in laminar ceramics with large compressive stress which still have not been satisfactory explained. Experimental observations of the crack path in the multilayered ceramics tested under several kinds of loading showed crack penetration (i.e. crack propagating normal to the layers followed by crack bifurcation when the crack propagated from the tensile to the compressive layer. Numerical results [1] show that the initiation of crack bifurcation can be explained by the near-tip J-integral, provided that micro-cracks exist near the crack tip. We revisit the problem using the concept of Finite fracture mechanics and the matched asymptotic expansion method in order to evaluate the energy release rate criteria describing the competition of the crack bifurcation and straight crack propagation near behind the bimaterial interface.

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Failure Behaviour of High Toughness Multi-Layer Si3N4 and Si3N4-TiN Based Laminates

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.290.175 ◽

2005 ◽

Vol 290 ◽

pp. 175-182 ◽

Cited By ~ 5

Author(s):

Gurdial Blugan ◽

Richard Dobedoe ◽

I. Gee ◽

Nina Orlovskaya ◽

Jakob Kübler

Keyword(s):

Fracture Toughness ◽

High Temperature ◽

Residual Stresses ◽

Crack Propagation ◽

Failure Mechanisms ◽

High Strength ◽

Crack Deflection ◽

High Toughness ◽

Energy Absorbing ◽

Crack Bifurcation

Multi-layer laminates were produced using alternating layers of Si3N4 and Si3N4+TiN. The differences in the coefficient of thermal expansions between the alternating layers lead to residual stresses after cooling. These are compressive in the Si3N4 layers and tensile in the Si3N4+TiN layers. The existence of these stresses in the laminates effect the crack propagation behaviour during failure. Different designs of laminates were produced with external layers under compression and tension exhibiting different failure mechanisms. Facture toughness was measured by SEVNB method. In systems with external layers under compression the measured fracture toughness was up to three times that of Si3N4, i.e. up to 17 MPa m1/2. In systems with external layers under tension during failure the energy absorbing effects of crack deflection and crack bifurcation were obtained. High temperature tests were performed to determine the onset temperature for residual stresses in these laminates. Micro-laminates with compressive layers of only 30 µm thickness with high strength and fracture toughness and were manufactured.

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Effects of HfC Particles on Crack Initiation and Propagation Behavior of WC/Co Composites

Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University ◽

10.1051/jnwpu/20193730628 ◽

2019 ◽

Vol 37 (3) ◽

pp. 628-635

Author(s):

Xinyu Yan ◽

Shouren Wang ◽

Daosheng Wen ◽

Gaoqi Wang ◽

Wentao Liu

Keyword(s):

Fracture Toughness ◽

Crack Propagation ◽

Bending Strength ◽

Crack Tip ◽

Crack Deflection ◽

Simulation Software ◽

Homogeneous Distribution ◽

The Matrix ◽

Crack Pinning ◽

Crack Bifurcation

Tungsten carbide composites were prepared by cold-pressing and hot-pressing sintering; fracture toughness and bending strength of the specimens were tested. The microstructures of HfC/WC/Co composites were observed with the SEM. The mathematical models were established to investigate the relationship between stress intensity factors of crack straight-through, crack deflection, and crack bifurcation with crack length, based on the crack propagation energy release rate. The simulation software ABAQUS was used to verify the four crack propagation methods of crack straight-through, crack deflection, crack bifurcation and crack pinning. The simulation results show that adding appropriate amount of HfC can effectively improve the fracture toughness and bending strength of the composites. The homogeneous distribution of HfC and Co in the matrix has a significant effect on the improvement of the strength and toughness of the composites, and the improvement mechanism is to disperse or transfer the stress at the crack tip to HfC by crack deflection, crack bifurcation, crack pinning, transcrystalline fracture, etc. As a result, the stress concentration at the crack tip in the matrix is reduced, and the toughness of the composites is improved.

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