Subsonic and Intersonic Crack Growth Along a Bimaterial Interface

1996 ◽  
Vol 63 (4) ◽  
pp. 919-924 ◽  
Author(s):  
R. P. Singh ◽  
A. Shukla
Keyword(s):  
Crack Growth ◽  
Wave Velocity ◽  
Interfacial Crack ◽  
Crack Tip ◽  
Complex Stress ◽  
Bimaterial Interface ◽  
Bimaterial Interfaces ◽  
Line Of Discontinuity ◽  
Compliant Material ◽  
Tip Velocity

An experimental investigation has been conducted to study the dynamic failure of bimaterial interfaces. Interfacial crack growth is observed using dynamic photoelasticity and characterized in terms of crack-tip velocity, complex stress intensity factor, and energy release rate. On the basis of crack-tip velocity two growth regimes are established, viz. the subsonic and transonic regimes. In the latter regime crack-tip velocities up to 1.3 times the shear wave velocity of the more compliant material are observed. This results in the formation of a line of discontinuity in the stress field surrounding the crack tip and also the presence of a pseudo crack tip that travels with the Rayleigh wave velocity (of the more compliant material).

Dynamic Fracture Criteria for Crack Growth Along Bimaterial Interfaces

1998 ◽  
Vol 65 (2) ◽  
pp. 293-299 ◽  
Author(s):  
M. Kavaturu ◽  
A. Shukla
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Shear Wave ◽  
Wave Speed ◽  
Crack Tip ◽  
Fracture Criteria ◽  
Shear Wave Speed ◽  
Bimaterial Interfaces ◽  
Opening Mode ◽  
Tip Velocity

Dynamic fracture criteria based on experimental observations are proposed for subsonic crack growth along bimaterial interfaces. These criteria are based on the premise that the crack-face displacements at a point behind the crack tip increase exponentially with the instantaneous crack-tip velocity. This assumption establishes a generalized relationship between the dynamic energy release rate and the instanta-neous crack-tip velocity. Experiments are performed on PSM-1/aluminum bimaterial systems for both shear dominated and opening-mode dominated crack growth to verify the proposed criteria. Two different bimaterial specimen geometries are employed to obtain the complete range of crack-tip speeds in the subsonic regime. The dynamic loading is achieved either by detonating two explosive charges on the specimen or by impacting the specimen in one-point bend configuration. Dynamic photoelasticity in conjunction with high-speed photography is used to analyze the fracture event. Explosive loading of the interface crack results in crack propagation speeds on the order of 65 percent of the shear wave speed of PSM-1 and the crack growth is observed to be stable and opening-mode dominated. In contrast, the impact loading results in very high crack propagation speeds on the order of shear wave speed of PSM-1 and the crack growth is observed to be shear dominated.

Diffusive Crack Growth at a Bimaterial Interface

1996 ◽  
Vol 63 (3) ◽  
pp. 796-803 ◽  
Author(s):  
Tze-jer Chuang ◽  
June-Liang Chu ◽  
Sanboh Lee
Keyword(s):  
Tensile Stress ◽  
Crack Growth ◽  
Crack Tip ◽  
Ceramic Composites ◽  
Bimaterial Interface ◽  
Self Diffusion ◽  
Interfacial Sliding ◽  
Stress Solution ◽  
Microcrack Growth ◽  
Loading Parameter

The high temperature microcrack growth behavior along a planar interface between two elastic dissimilar media is investigated with an aim at estimating service life of advanced ceramic composites under creep-rupture conditions. The crack is assumed to grow along the interface normal to a remote applied tensile stress via a coupled surface and grain-boundary diffusion under steady-state creep conditions. The crack-tip conditions were first derived from the asymmetric tip morphology developed by surface self-diffusion. The governing integro-differential equation containing the unknown tensile stress distribution along the interface ahead of the moving crack tip was derived and it was found that a new length parameter exists as a scaling factor for the interface for which the solution becomes identical to that of the single-phase media when plotted on the nondimensional physical plane. In contrast to the elastic stress solution which shows singularity at the tip and oscillatory character away from the tip, the creep stresses have a peak value away from the tip due to a wedging effect and interfacial sliding eliminates stress oscillation resulting in a decoupling between mode I and mode II stress fields. This stress solution ties the far-field loading parameter to the crack-tip conditions in terms of the unknown crack velocity to give a specific V-K functional relationship. It was shown that a stress exponent of 12 in the conventional power-law crack growth emerges at higher applied stress levels. An analysis on energy balance shows that the energy release during crack growth amounts to the J-integral which derives mostly from work done by “wedging,” not from strain energy loss. A constraint on interfacial diffusivities of the two species was found and its implications on possible microstructural developments were discussed.

Characteristic Parameters of Dynamic Crack Growth along the Interface between the Two Orthotropic Materials

2012 ◽  
Vol 452-453 ◽  
pp. 1184-1189
Author(s):  
Jelena M. Djokovic ◽  
Ružica R. Nikolić
Keyword(s):  
Crack Growth ◽  
Interfacial Crack ◽  
Crack Tip ◽  
Micromechanical Modeling ◽  
Orthotropic Materials ◽  
Dynamic Crack ◽  
Crack Speed ◽  
Energy Factor ◽  
Dynamic Crack Growth ◽  
Resolution Factor

In this paper is analyzed the behavior of parameters that characterize the process of a dynamic crack growth along the interface between the two orthotropic materials. The emphasis is placed on the application of the fracture mechanics concept for the interfacial crack that propagates dynamically, at high speed. In this work is considered the behavior of the oscillation index, the traction resolution factor and the energy factor depending on the crack tip speed and the stifnesses ratio. The oscillatory index increases with the crack tip speed and tends to infinity when the crack speed approaches the Rayleigh wave speed of the less stiff of the two materials. The traction resolution factor depends strongly on the crack speed but weakly on the stiffness ratio. The behavior of the energy factor is completely different from the behavior of the traction resolution factor. Results provided in this paper can be used as a guide for micromechanical modeling of materials.

Influence of Rotatory Inertia on Steady-State Crack Propagation in a Finite Plate Subjected to Out-of-Plane Bending

1978 ◽  
Vol 45 (1) ◽  
pp. 130-134 ◽  
Author(s):  
A. F. Fossum
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Wave Velocity ◽  
Release Rate ◽  
Dynamic Stress ◽  
Dynamic Stress Intensity Factor ◽  
Crack Tip ◽  
Out Of Plane ◽  
Tip Velocity

A dynamic stress-intensity factor and energy release rate are obtained for a running semi-infinite crack traversing a strip of elastic material subjected to out-of-plane bending. It is shown that the maximum ratio of crack tip velocity to shear wave velocity is identical to the maximum ratio of flexural wave velocity to shear wave velocity in the limit of vanishingly small wavelength. The dynamic stress-intensity factor is written as the product of a static stress-intensity factor multiplied by a function of Poisson’s ratio and crack tip velocity the function decreasing monotonically with increasing crock tip velocity. The energy release rate is shown to be independent of crack tip velocity for this type of problem.

Development of a dynamic decohesion criterion for subsonic fracture of the interface between two dissimilar materials

1995 ◽  
Vol 451 (1943) ◽  
pp. 711-736 ◽  
Keyword(s):  
Crack Growth ◽  
High Speed ◽  
Crack Tip ◽  
Dissimilar Materials ◽  
Complex Stress ◽  
High Speed Photography ◽  
Dynamic Crack ◽  
Shear Wave Speed ◽  
Loading Rates ◽  
Lateral Shearing Interferometer

We present findings of an experimental study of dynamic decohesion of bimaterial systems composed of constituents with a large material property mismatch. Poly-methylmethacrylate (PMMA)-steel and PMMA-aluminium bimaterial fracture specimens were used. Dynamic one-point bend loading was accomplished with a drop-weight tower device (for low and intermediate loading rates) or a high-speed gas gun (for high loading rates). High-speed interferometric measurements were made using the lateral shearing interferometer of coherent gradient sensing in conjunction with high-speed photography. Very high crack propagation speeds (terminal crack-tip speeds up to 1.5 c s PMMA , where c s PMMA is the shear wave speed of PMMA) and high accelerations (of about 10 7 g , where g is the acceleration of gravity) were observed and are reported. Issues regarding data analysis of the high-speed interferograms are discussed. The effects of near-tip three-dimensionality are also analysed. Dynamic complex stress factor histories are obtained by fitting the experimental data to available asymptotic crack-tip fields. A dynamic crack growth criterion for crack growth along bimaterial interfaces is proposed. In the subsonic regime of crack growth it is seen that the opening and shearing displacements behind the propagating crack tip remain constant and equal to their value at initiation, i.e. the crack retains a self-similar profile during crack growth at any speed. This forms the basis of the proposed dynamic interfacial fracture criterion.

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