• Journal of the KSME
• /
• v.27 no.2
• /
• pp.132-136
• /
• 1987

최근 저자는 혼합모우드에 대한 Budiansky와 Rice의 $J_k$ 적분에 모순이 있음을 지적한 바 있다. 그러나, Kishimoto등은 파괴진행영역을 고려한 경로 독립적분J/^/을 제시하여 주목을 끌고 있다. Landes등은 Rice의 J적분을 정상상태 크리이프에까지 연장 적용하기 위한 $C^*$적분을 소개하였다. 그후 크리이프파괴에 대한 매개변수로서 Liu등에 의한 $C_{gk}{\;}^*$, Brust등에 의한 $T_k{\}^*$등이 소개되어 계속 연구중이다. 여기에서는 이러한 매개변수들에 대해 개괄적으로 서술하고자 한다.

• Journal of Korean Society of Steel Construction
• /
• v.17 no.2 s.75
• /
• pp.243-251
• /
• 2005

The fracture mechanics analysis of a crack in a weld must consider residual stress generated during welding. The standard definition of the J-integral requires a path dependent value in the presence of a residual stress field. Therefore, it is necessary to develop a path independent J-integral definition for a crack in a residual stress field. This paper addresses the modification of the Rice-J-integral to produce a path- independent J-integral when residual stresses and external forces are present. The residual stress problem is treated as an initial strain problem and the J-integral proposed for this type of problems is used. A program which can evaluate the J-integral for a crack in a weld is developed using the proposed J-integral definition. The situation when only residual stress is present is examined as is the case when mechanical stresses are applied in conjunction with a residual stress.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.7
• /
• pp.134-142
• /
• 2001

The integrals $J_k$(k=1,2) in the rectilinear anisotropis body in 2-D were determined using Lekhnitskii formalism. The relationship between $J_k$ and stress intensity factors are implified by the important equation between elastic compliance. The numerical evaluation of stress intensity factor for the single edge crack in mixed mode is determined by superposing known exact solutions.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.17 no.4
• /
• pp.423-431
• /
• 2004

For the fracture mechanics analysis of cracks in welds of dissimilar steels, residual stress analysis and fracture analysis must be performed simultaneously. The standard definition of the J -integral leads to a path dependent value in the presence of a residual stress field. And unlike cracks in homogeneous materials, a bimaterial interface crack always induces both opening and shearing modes of stress in the vicinity of the crack tip. Therefore, it is necessary to develope a path independent J-integral definition for a crack in a residual stress field generated by welding of dissimilar steels. This paper addresses the modification of the Rice-J-integral to produce a path independent J -integral when residual stresses due to welding of dissimilar steels and external forces are present. The residual stress problem is treated as an initial strain problem and the J-integral proposed for this class of problems is used. And a program which can evaluate the J -integral for a crack in a weld of dissimialr steels is developed using proposed J integral definition.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.3
• /
• pp.232-240
• /
• 1984

The plane elastostatic boundary value problem with the sharp V-notched singularity is formulated by a contour integral method for determining numerically the stress intensity factors. The integral formula is based on Somigliana type of reciprocal work in terms of displacement and traction vectors on the plate boundary. The characteristic singular solutions can be identified on the basis of traction free boundary conditions of two radial notch edges. Two numerical example examples are treated in detail; a symmetric mode-I type of notched plate with various interior angles and a mixed mode type of cantilever subjected to end shear.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.6
• /
• pp.1792-1798
• /
• 1991

In this paper the path independent $J_{k}$(k=1, 2) integrals are evaluated in a rectilinear anisotropic body for two dimensional case. The relationship among elastic constants are examined. Using those relationship the expression of $J_{2}$ Integral in terms of $K_{I}$ is found to be very simple.e.e.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.3
• /
• pp.479-489
• /
• 1989

The $J_{k}$ integral method for determining mixed mode stress intensity factors separately in the cracked anisotropic plate is developed. Stress intensity factors are indirectly determined from the values of $J_{1}$ and $J_{2}$. The $J_{2}$ integral can be evaluated efficiently from a finite element solution, neglecting the contribution from the portion of the integration contour along the crack faces, by selecting the integration contour in the vicinity of the crack tip. Using functions of a complex variable, the complete relations between $J_{1}$, $J_{2}$ and $K_{I}$ , $K_{II}$ for anisotropic materials are derived conveniently by selecting narrow rectangular contours shrinking to the crack tip. Compared to the existing path independent integral methods, the present method does not involve calculating the auxiliary solution and hence numerical procedures become quite simple. Numerical results to various problems are given and demonstrate the accuracy, stability and versatility of the method.

• Journal of the Korean Society of Safety
• /
• v.11 no.2
• /
• pp.16-24
• /
• 1996

In this study we simulate the fatigue test of a compact tension specimen and obtain the displacements, stresses and strains by using the finite element method. And we examine the path independency of $\Delta$J integral values and compare it with $\Delta$J integral values calculated from load-load line displacement curve. From the results of this study, we can find that $\Delta$J integral show the path Independency for saturated materials. We can also find that the path independency of $\Delta$J Is not satisfied when different material Is assumed near the crack tip, but the difference in $\Delta$J is small. And $\Delta$J integral values calculated from load-load line displacement is very analogous with those from integration path but always have lower values than those from integration paths. In the case of crack closing, we found that $\Delta$J integral values from load-load line displacement should be calculated with the load Increment values based on the crack opening point. The unsaturated material is also simulated and its $\Delta$J shows different values according to the path, but the difference is small.