scholarly journals Dynamic Analysis of Cracked Octagonal Quasicrystals

2011 ◽  
Vol 2011 ◽  
pp. 1-18 ◽  
Author(s):  
Wu Li ◽  
Tian You Fan
Keyword(s):  
Stress Intensity Factor ◽  
Wave Propagation ◽  
Stress Intensity ◽  
Dynamic Fracture ◽  
Additional Condition ◽  
Moving Boundary ◽  
Stress Singularity ◽  
Elastic Media ◽  
Griffith Crack ◽  
And Diffusion

We focus on the dynamic fracture problem of octagonal quasicrystals by applying a rectangular sample with a Griffith crack which is often used in classical elastic media based on the method of finite difference. This paper mainly is to investigate the variation of phonon, phason fields, and stress singularity around the crack tip including the stress intensity factor. In addition, the moving boundary due to the crack propagation has also been treated by introducing an additional condition for determining solution. The influence of wave propagation and diffusion in the dynamic process is also discussed in detail. Through comparing the results of octagonal quasicrystals with the results of crystal, this paper proclaims the influence of phonon-phason coupling in dynamic fracture problem of octagonal quasicrystals which should not be neglected.

scholarly journals Hole Defects Affect the Dynamic Fracture Behavior of Nearby Running Cracks

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
R. S. Yang ◽  
C. X. Ding ◽  
L. Y. Yang ◽  
P. Xu ◽  
C. Chen
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Dynamic Fracture ◽  
Fracture Behavior ◽  
Dynamic Stress ◽  
Crack Path ◽  
Dynamic Stress Intensity Factor ◽  
Experimental System ◽  
Intersection Area

Effects of defects on the dynamic fracture behavior of engineering materials cannot be neglected. Using the experimental system of digital laser dynamic caustics, the effects of defects on the dynamic fracture behavior of nearby running cracks are studied. When running cracks propagate near to defects, the crack path deflects toward the defect; the degree of deflection is greater for larger defect diameters. When the running crack propagates away from the defect, the degree of deflection gradually reduces and the original crack path is restored. The intersection between the caustic spot and the defect is the direct cause of the running crack deflection; the intersection area determines the degree of deflection. In addition, the defect locally inhibits the dynamic stress intensity factor of running cracks when they propagate toward the defect and locally promotes the dynamic stress intensity factor of running cracks when they propagate away from the defect.

Relation between Stress Intensity Factor of a Small Edge Interface Crack and Intensity of Free-Edge Stress Singularity of Bonded Dissimilar Materials

2004 ◽  
Vol 261-263 ◽  
pp. 351-356
Author(s):  
Seiji Ioka ◽  
Shiro Kubo
Keyword(s):  
Stress Intensity Factor ◽  
Free Surface ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Edge Crack ◽  
Stress Singularity ◽  
Dissimilar Materials ◽  
Free Edge ◽  
Edge Stress ◽  
The Relationship

When two materials are bonded, the free-edge stress singularity usually develops near the intersection of the interface and the free-surface. Fracture in bonded dissimilar materials may therefore occur from an interface crack which develops at the intersection of interface and free-surface. Free-edge stress singularity is very important in the evaluation of strength of bonded dissimilar materials. In this study, the relationship between the stress intensity factor of a small edge crack on interface of bonded dissimilar materials and the intensity of free-edge stress singularity of bonded dissimilar materials with no crack under external mechanical loading was investigated numerically by using the boundary element method. The relationship was also investigated theoretically by using the principle of superposition. The results of numerical analyses were compared with those of theoretical analyses. It was found that stress intensity factors of small edge crack on interface K1 and K2 were proportional to the intensity of free-edge stress singularity of bonded dissimilar materials Kσ without crack irrespective of the combination of materials. The numerically determined proportional coefficient between K1 and Kσ agreed well with the theoretical one, and was not affected by crack length when proper normalizations were applied. From these results, it is suggested that stress intensity factor of small edge crack on interface can be used as a strength criterion of interface of bonded dissimilar materials.

An Exact Analytical Solution for Star-Shaped Cracks

2015 ◽  
Vol 1094 ◽  
pp. 458-463 ◽  
Author(s):  
Zhu Chen
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Analytical Solution ◽  
Complex Analysis ◽  
Exact Analytical Solution ◽  
Plane Elasticity ◽  
Type I ◽  
Griffith Crack ◽  
Shaped Crack ◽  
Plane Elasticity Problem

Using the method of complex analysis and by constructing conformal mapping, the study investigates the plane elasticity problem of star-shaped cracks and provides an analytical solution for the stress intensity factor (SIF) of crack-tip type I and II. Problems of the classic Griffith crack, the cross-shaped crack, concurrent uniformly distributed three-cracks and symmetrical eight-cracks are also simulated.

scholarly journals Applicability of Continuum Fracture Mechanics in Atomistic Systems

2011 ◽  
Author(s):  
Shao-Huan Cheng ◽  
C. T. Sun
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Stress Singularity ◽  
Critical Stress Intensity Factor ◽  
Singular Stress ◽  
Virial Stress ◽  
Atomistic Systems ◽  
Definition Of

Stress intensity factor is one of the most significant fracture parameters in linear elastic fracture mechanics (LEFM). Due to its simplicity, many researchers directly employed this concept to explain their results from molecular simulation. However, stress intensity factor defines the amplitude of the singular stress, which is the product of continuum elasticity. Under atomistic systems without the stress singularity, the concept of stress intensity factor must be examined. In addition, the difficulty of studying the stress intensity factor in atomistic systems may be traced back to the ambiguous definition of the local atomistic stress. In this study, the definition of the local virial stress is adopted. Subsequently, through the consideration of K-dominance, the approximated stress intensity factor based on the atomistic stress can be projected within a reasonable region. Moreover, the influence of cutting interatomic bonds to create traction free crack surfaces and the critical stress intensity factor is also discussed.

Effect on Dynamic Biaxial Fracture Behaviors by Different Heat Treatments on Magnesium Alloy

2008 ◽  
Vol 33-37 ◽  
pp. 357-362
Author(s):  
Akira Shimamoto ◽  
Ryo Kubota
Keyword(s):  
Heat Treatment ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Dynamic Fracture ◽  
Dynamic Stress Intensity Factor ◽  
Treatment Temperature ◽  
Biaxial Stress ◽  
Heat Treated ◽  
Caustics Method

The dynamic fracture experiments were conducted on the heat treated magnesium alloys; AZ31B-O, AZ31B-200 °C, and AZ31B-430 °C. Cross shaped specimens with the crack on their center were used for the experiments. Dynamic fracture behavior near a crack tip under equal and unequal biaxial stress was observed by the caustics method. From the observation, the stress intensity factor and the fracture toughness value were calculated. As a result, the effect of heat treatment was found. However, no clear relation such as correlation between dynamic stress intensity factor and heat treatment temperature was deduced.

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