scholarly journals Transient Analysis for Antiplane Crack Subjected to Dynamic Loadings

1991 ◽  
Vol 58 (3) ◽  
pp. 703-709 ◽  
Author(s):  
Chien-Ching Ma ◽  
Ying-Chung Hou
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Shear Wave ◽  
Dynamic Stress Intensity Factor ◽  
Crack Tip ◽  
Point Load ◽  
Crack Face ◽  
Kinked Crack ◽  
Kink Angle

The problem considered here is the antiplane response of an elastic solid containing a half-plane crack subjected to suddenly applied concentrated point forces acting at a finite distance from the crack tip. A fundamental solution for the dynamic dislocation is obtained to construct the dynamic fracture problem containing a characteristic length. Attention is focused on the time-dependent full-field solutions of stresses and stress intensity factor. It is found that at the instant that the first shear wave reaches the crack tip, the stress intensity factor jumps from zero to the appropriate static value. The stresses will take on the appropriate static value instantaneously upon arrival of the shear wave diffracted from the crack tip, and this static value is thereafter maintained. The dynamic stress intensity factor of a kinked crack from this stationary semi-infinite crack after the arrival of shear wave is obtained in an explicit form as a function of the kinked crack velocity, the kink angle, and time. A perturbation method, using the kink angle as the perturbation parameter, is used. If the maximum energy release rate is accepted as the crack propagation criterion, then the crack will propagate straight ahead of the original crack when applying point load at the crack face.

Suddenly Arrested Intersonic Shear Crack

2001 ◽  
Author(s):  
Y. Huang ◽  
H. Gao
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fundamental Solution ◽  
Shear Crack ◽  
Auxiliary Problem ◽  
Dynamic Stress Intensity Factor ◽  
Crack Tip ◽  
Crack Face ◽  
Static Crack

Abstract We study a mode II crack suddenly stopping after propagating intersonically for a short time. The solution is obtained by superposing the fundamental solution and the auxiliary problem of a static crack emitting dynamic dislocations such that the relative crack face displacement in the fundamental solution is negated ahead of where the crack tip has stopped. We find that, after the crack stops moving, the stress intensity factor rapidly rises to a finite value and then starts to change gradually toward the equilibrium value for a static crack. A most interesting feature is that the static value of stress intensity is reached neither instantaneously like a suddenly stopping subsonic crack nor asymptotically like a suddenly stopping edge dislocation. Rather, the dynamic stress intensity factor changes continuously as the shear and Rayleigh waves catch up with the stopped crack tip from behind, approaches negative infinity when the Rayleigh wave arrives, and then suddenly assumes the equilibrium static value when all the waves have passed by. This study is an important step toward the study of intersonic crack propagation with arbitrary, non-uniform velocities.

Influences of Crack Face Bridging Stress and Microstructure on Fracture Toughness of Toughened Alumina Ceramics

2011 ◽  
Vol 462-463 ◽  
pp. 972-978
Author(s):  
Yoshihisa Sakaida ◽  
Hajime Yoshida ◽  
Shotaro Mori
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Opening ◽  
Stress Shielding ◽  
Crack Tip ◽  
Shielding Effect ◽  
Hot Press ◽  
Crack Face

Three types of polycrystalline alumina, one pressureless and two hot press sintered Al2O3, were used to examine the effects of the characteristics of microstructure and crack face bridging on fracture toughness. The crack opening displacements and microstructures along the pop-in crack of single edge precracked beam (SEPB) specimens were observed in situ at a constant applied stress intensity factor by scanning electron microscopy (SEM). The bridging stress distribution could be determined from the measured crack opening displacement by three-dimensional finite element analysis, and then the stress intensity factor and stress shielding effect at the crack tip could also be determined. Intergranular microcracks of toughened Al2O3 were deflected by a complicated microstructure, and crack closure due to bridging grains was observed near the crack tip. Bridging stress of Al2O3 was compressive perpendicular to the crack face and was distributed behind the crack tip. The maximum bridging stress of two hot press sintered Al2O3 was about twice as large as that of pressureless sintered Al2O3. The fracture toughness of hot press sintered Al2O3 was, therefore, higher than that of pressureless sintered Al2O3, because the total amount of bridging stress and stress shielding effect increased with increasing magnitude of microcrack deflection and the number of interlocking grains.

Dynamic Stress Intensity Factor for a Radial Crack on a Circular Cavity in a Piezoelectric Medium

2010 ◽  
Vol 452-453 ◽  
pp. 273-276
Author(s):  
Tian Shu Song ◽  
Dong Li ◽  
Ming Yue Lv ◽  
Ming Ju Zhang
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Dynamic Stress ◽  
Radial Crack ◽  
Dynamic Stress Intensity Factor ◽  
Crack Tip ◽  
Piezoelectric Medium ◽  
Circular Cavity ◽  
Dynamic Stress Intensity Factors

The problem of dynamic stress intensity factor is investigated theoretically in present paper for a radial crack on a circular cavity in an infinite piezoelectric medium, which is subjected to time-harmonic incident anti-plane shearing. First, a pair of electromechanically coupled Green’s functions are constructed which indicate the basic solutions for a semi-infinite piezoelectric medium with a semi-circular cavity. Second, based on the crack-division technique and conjunction technique, integral equations for the unknown stresses’ solution on the conjunction surface is established, which are related to the dynamic stress intensity factor at the crack tip. Third, the analytical expression on dynamic stress intensity factor at the crack tip is obtained. At last, some calculating cases are plotted to show how the frequencies of incident wave, the piezoelectric characteristic parameters of the material and the geometry of the crack and the circular cavity influence upon the dynamic stress intensity factors. While some of the calculating results are compared with the same situation about a straight crack and with static solutions.

Dynamic Fracture Under Normal Impact Loading of the Crack Faces

1985 ◽  
Vol 52 (3) ◽  
pp. 585-592 ◽  
Author(s):  
K.-S. Kim
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Impact Loading ◽  
Crack Tip ◽  
Time Behavior ◽  
Crack Face ◽  
Copper Strip ◽  
Transient Stress ◽  
Crack Faces

Results of experiments on crack-face impact are presented. The transient stress-intensity factor variation of a crack has been traced by the Stress-Intensity Factor Tracer (SIFT) [1] under time-stepwise uniform pressure loading of the crack faces. To see the effects of various waves generated by the loading, part of the crack faces was left free of traction within the distance l0 from the crack tip. The crack-face impact loading was produced by an electromagnetic force induced by a square pulse of an electric current flowing through a copper strip inserted in the saw-cut crack of a Homalite 100 plate specimen. The current flowed in opposite directions in the two portions of the copper strip, between the crack faces, causing them to repel each other. The short-time and the long-time behavior of the transient stress-intensity factor variation under the impact loading have been carefully investigated. Brittle dynamic initiation of crack extension and the stress-intensity variation of a running crack have been also examined. The experimental results have been compared with theoretical predictions based on Freund’s crack-face concentrated load solution [2]. The agreement between the theory and the experiment is excellent. In this study, the various waves generated by the loading are shown to play different roles in transmitting the load to the crack tip. In addition, confirmation is given that the SIFT is excellent in tracing the stress-intensity factor regardless of the crack-tip motion.

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.

Dynamic Stress Intensity Factor Due to Concentrated Loads on Semi-Infinite Cracks in Orthotropic Materials

2000 ◽  
Author(s):  
C. Rubio-Gonzalez ◽  
C.-Y. Wang ◽  
J. J. Mason
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Dynamic Stress ◽  
Fourier Transforms ◽  
Asymptotic Expression ◽  
Dynamic Stress Intensity Factor ◽  
Crack Tip ◽  
Orthotropic Materials ◽  
Isotropic Case

Abstract The transient elastodynamic response due to concentrated normal or shear impact loads on the faces of a semi-infinite crack in orthotropic materials is examined. Solution for the stress intensity factor history around the crack tip is found. Laplace and Fourier transforms together with the Wiener-Hopf technique are employed to solve the equations of motion in terms of displacements. An asymptotic expression for the stress near the crack tip is analyzed which leads to the dynamic stress intensity factor in modes I and II. Similar to the isotropic case, it is found that the stress intensity factor has a singularity and discontinuity when the Rayleigh wave emitted from the load arrives at the crack tip. Results are presented for a typical orthotropic material.

On the Characterization of the Transient Stress Field Near the Tip of a Crack

1987 ◽  
Vol 54 (1) ◽  
pp. 72-78 ◽  
Author(s):  
K. Ravi-Chandar ◽  
W. G. Knauss
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Field ◽  
Dynamic Stress ◽  
Dynamic Stress Intensity Factor ◽  
Crack Tip ◽  
Transient Conditions ◽  
Dynamic Stress Field

The dynamic stress field near a propagating crack tip is usually characterized in terms of one parameter, namely, the dynamic stress intensity factor. While analytically this is an exact representation at the crack tip itself, under transient conditions, the domain of dominance of the stress intensity factor varies as discussed by Ma and Freund (1986). In this paper, we present experimental results which show that while the stress intensity factor may dominate the near tip stress field under transient conditions as long as the crack velocity is small, it may not be dominant over an appreciable region under other transient conditions of crack tip motion, thus making it difficult to determine this quantity experimentally.

A new type of cracks adding to Griffith–Irwin cracks

2019 ◽  
Vol 485 (2) ◽  
pp. 162-165
Author(s):  
V. A. Babeshko ◽  
O. M. Babeshko ◽  
O. V. Evdokimova
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Tip ◽  
Stress Concentrations ◽  
New Type

The distinctions in the description of the conditions of cracking of materials are revealed. For Griffith–Irwin cracks, fracture is determined by the magnitude of the stress-intensity factor at the crack tip; in the case of the new type of cracks, fracture occurs due to an increase in the stress concentrations up to singular concentrations.

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