Formula For Stress Intensity Factor Research Articles

Study on LBB criterion of high pressure reactors for polyethylene production. 2nd report Stress intensity factor of internal pressure cylinder and LBB criterion.

to study on the leak before break, namely LBB criterion of high pressure reactors for polyethylene production, the validity of the stress intensity factor formulas proposed by Newman-Raju, Iwadate et al. and Nakazawa et al. were discussed. When Newman-Raju's stress intensity factor formula without considering the back surface magnification factor is used, the condition of K1≥ KIC(J) gives a good criterion for LBB condition.

Isotropic/orthotropic two-layered strips containing cracks terminating at and going through an interface

Crack problems for isotropic/orthotropic two-layered strips have been investigated. A system of two singular integral equations can be derived by using Fourier integral transformation and boundary conditions of crack problems. After stress singularities at crack tips or other special points are determined for internal and edge cracks, and for cracks terminating at and going through the interface, the system of singular integral equations is solved numerically by Gauss-Jacobi or Gauss-Chebyshev integration formulas for stress intensity factors at the tips and other singular points of cracks. Finally, possible crack growth behavior for cracks approaching and going through the interface is discussed.

On bars with cracks

Within the framework of elementary strength-of-materials theories, bars with cracks subjected to tension or torsion are considered. Simple formulas for stress intensity factors are derived leading to results which are close to values obtained on the basis of the theory of elasticity.

Formulae of Stress Intensity Factors of Branched Cracks in Plane Problems

Formulae of Stress Intensity Factors of Branched Cracks in Plane Problems

Formulae of Stress Intensity Factors of Kinked Cracks in Plane Problems

Formulae of Stress Intensity Factors of Kinked Cracks in Plane Problems

Analysis of cracked disk specimens

A Fredholm integral equation of the plane problem for an arbitrarily loaded disk with an arbitrarily located inner crack is obtained and its solution in the form of double series in power of two parameters is provided. A general formula to define stress intensity factors of central crack is given by which the stress intensity factors for some types of loading are derived and analysed. It is shown that disks loaded by centrifugal forces due to uniform rotation and compressed in the plane of the crack are particularly suitable in fracture toughness testing of brittle materials. It is found that for disks stretched by two forces applied at some distance from the crack the stress intensity factor remains constant in a large range of crack lengths. Therefore they are recommended to be used in subcritical crack growth rate testing. Suitable grips are developed and appropriate correction for their effect is made in the stress intensity factor formula. Recommendations for a choice of optimal dimension ratios for a disk specimen are given.

On the Brittle Fracture Initiation from a Surface Crack at Welded Joint

Generally, there may be possibility that brittle fracture would start from a welded joint of welded steel structures, because of some weld errors such as angular distortion and misalignment, some defects such as weld cracking or fatigue crack, and low toughness of welded fusion line. In order to prevent structures from brittle fracture, it is necessary to have enough knowledge about brittle fracture initiating property of welded fusion line which is superposed some weld errors and defects, and to know the toughness which is required for welded steel structures.In this study, brittle fracture test of so-called large scale tensile specimens with angular distortion, misalignment and surface notch was conducted with 8000 ton and 2000 ton test rigs using weld joints of 25, 50 and 75 mm thick mild steel, 50, 60 and 80 kg/mm2 tensile strength steels. The surface crack of this type specimen is exposed under the superimposed. condition of tensile stress and bending stress. A general approximate formula of stress intensity factor for such a semi-elliptical surface crack was derived from G. R. Irwin's solution and A. S. Kobayashi's numerical results. This formula was proven to explain the results of simple tensile and pure bending tests.Furthermore, the bending stress behavior of the tensile specimen with angular distortion and misalignment was analyzed, and a general solution of bending stress for elastic end condition was obtained. Using these formulae, critical stress intensity factor for brittle fracture of such a specimen that was tested in this study can be evaluated reasonably.In order to evaluate brittle fracture of steel structures with a quality control test, the relation between the critical stress intensity factor of the large scale test and the absorbed energy of Charpy test was investigated. Then, modifing Y. Hagiwara's correlation formula between critical COD and Charpy impact energy, a statistical correlation formula was obtained. As a result, it is possible to assess welded steel structures against brittle fracture initiation with fracture mechanics approach using the result of Charpy test which is one of quality control tests.