The exponent λ is a function of mode of cracking (i.e. mode I, II or III), the inclination angle β of the crack front at the free surface, the inclination angle γ of the crack plane with the solid surface and the Poisson's ratio of the solid.

The size and shape of the crack front were updated using the result of finite element program, and then the crack propagation was simulated by moving the node.

(2) The stress intensity factors(SIFs) in the crack front decreases with the increase of the distance from the upper free surface regardless of the cracked body type(infinite or finite).

3. Using the above method, mode-I and mixed-mode crack problems of typical cracks are numerically calculated and the electroelastic intensity factors near the crack front are given, accuracy of results are found to be very high;

Stress intensity factors(SIFs) of cracks having different length which angle β is equal to 45°, 60° and 75° respectively, are calculated by using finite element method(FEM).

The reasons for improving the fatigue properties of 1Cr18Ni9Ti steel caused by vacuum and low temperature were attributed to the cleaning-up effect of vacuum on crack surfaces and the formation of lath martensite induced by low temperature.

The complex stress intensity factor and the strain energy density in the tip of interface cracks are calculated for these two kinds of specimens respectively.

Using frozen stress photo-elastic method, experimental studies were made of the Stress Intensity Magnification Factor(M_s)for internal surface crack in pressurised thin spherical shells with ratios of wall thickness to inner diameter W/R_i=0. 10, 0. 078, 0. 067. The variation of M_s with shape a/c anddepth a/W along the crack periphery was obtained.

We propose an analytic expression for the exponent and confirm this for different models (crack front propagation, Edwards-Wilkinson model in a quenched noise etc.).

The results of the displacement discontinuities of the crack surface and the stress intensity factors at the crack front are in good agrement with the theoretical solutions.

Moreover, the singular nature of temperature gradient field near the crack front is proved by the main-part analysis method of the singular integral equation, and the singular temperature gradients are exactly obtained.

Variation of the stress intensity factor along the crack front of interacting semi-elliptical surface cracks

The results show that the present method yields smooth variations of stress intensity factors along the crack front very accurately, for various geometrical conditions.

The paper analyses the macrofractography morphology of metal fatigue and bri-ttleness. It Shows that the space of the beach marks on fatigue sarface, the change of bended direction and the slant of the beach marks , the shape of the beach marks at the circumambdient stress concentration and fatigue steps at the different conditions can be described by using a simple equation. The shapes of the brittle rapid radiactive curves are calculated,analysed, compared and discussed with two different models (the vertical...

The paper analyses the macrofractography morphology of metal fatigue and bri-ttleness. It Shows that the space of the beach marks on fatigue sarface, the change of bended direction and the slant of the beach marks , the shape of the beach marks at the circumambdient stress concentration and fatigue steps at the different conditions can be described by using a simple equation. The shapes of the brittle rapid radiactive curves are calculated,analysed, compared and discussed with two different models (the vertical lines of the including curves of the twinkling leading edges of cracks and the traces cruves of the intersection of the growth of nuclei) and with two different growing methods of the nuclei (equal speed and equal power).

The paper contains experimental results of propagation rate distribution of a toecrack along its front under fatigue load.Experiments were performed on aluminumalloy(LY-12R)specimens simulating geometrical shape of a T-joint with toe crack.To obtain the crack propagation rate,markings were induced on fracture surface withchanges in amplitude at specified numbers of fatigue load cycles.After completefracture of the specimen,propagation rates were calculated by measuring the distancebetween markings on the fracture...

The paper contains experimental results of propagation rate distribution of a toecrack along its front under fatigue load.Experiments were performed on aluminumalloy(LY-12R)specimens simulating geometrical shape of a T-joint with toe crack.To obtain the crack propagation rate,markings were induced on fracture surface withchanges in amplitude at specified numbers of fatigue load cycles.After completefracture of the specimen,propagation rates were calculated by measuring the distancebetween markings on the fracture surface.It is shown that(1)owing to the stress concentration at the toe,the propaga-tion rate of a toe crack in the direction of plate width is always higher than thatof a crack of the same size in a flat plate,irrespective of the crack depth;(2)additional moment,caused by angular welding distortion,increases the propagationrate of toe crack in the direction of plate width;(3)the stress intensity factorof a toe crack at the front near the surface is always higher than that of a crackof the same size in a flat plate under the same loading conditions;(4)compressiveresidual stress at the toe is effective in reducing the propagation rate of toe crack;(5)the length of a crack originated from a toe crack when its vertex reaches theback surface of the plate is much greater than the final length of a part-through crackof the seme size,originated from a flate plate,when the plate is penetrated throughunder the same loading conditions.This should be taken into full acconnt in designingpressure vessels on the p(?)inciple of“leak before break”.

In this paper, the stress distribution at the flaw front of a body containing a crack of Mode I is investigated. A "near field" solution has been obtained for stress intensity factor K_1 in the full field. The results thus obtained can be taken as the analytical foundation for the experimental determination of K_1 and provide an appropriate mechanical model for the approximate mumerieal analysis. Thus, by use of the method presented in this paper, the difficulties involved in solving K_1 on account of "tip blunt"...

In this paper, the stress distribution at the flaw front of a body containing a crack of Mode I is investigated. A "near field" solution has been obtained for stress intensity factor K_1 in the full field. The results thus obtained can be taken as the analytical foundation for the experimental determination of K_1 and provide an appropriate mechanical model for the approximate mumerieal analysis. Thus, by use of the method presented in this paper, the difficulties involved in solving K_1 on account of "tip blunt" and the singularity in the stress field at the crack tip can be overcome and besides, the resulting errors in the determination of stress intensity factors K_1 can also be analysed. As a result, precision and accuracy are ensured.