• 한국해양공학회지
• /
• 제34권2호
• /
• pp.89-96
• /
• 2020

In this study, the Norbury-Fraenkel family of vortex rings is analyzed using a contour dynamics method for the stream function, which significantly reduces the numerical burden in the calculation. The stream function is formulated as the integral along the contour of the vorticity core. The integration over the logarithmic-singular segment is evaluated analytically, and the positions of the nodal points of the contour are calculated directly. The shapes of the cores and the dividing stream surfaces are found based on the mean core radius. Compared with other studies, the proposed method is verified and found to be more efficient.

• 대한조선학회논문집
• /
• 제54권4호
• /
• pp.335-343
• /
• 2017

The Newman-Raju formula and contour integral-based finite element analyses(FEAs) have been widely used to assess crack growth rates and residual lives at crack locations in ships or offshore structures, but the Newman-Raju formula is known to be less accurate for the complicated weld details and the conventional FEA-based contour integral approach needs concentrated efforts to construct FEA models. Recently, an extended finite element method(XFEM) has been proposed to reduce those modeling efforts with reliable accuracy. Stress intensity factors(SIFs) from the approaches such as the Newman-Raju formula, conventional FEA-based J-integral, and XFEM-based J-integral were compared for an infinitely long plate with a propagating elliptic crack. It was concluded that the XFEM approach was far reliable in terms of prediction ability of SIFs. Assuming a 25 year-aged coast guard patrol ship had the prescribed cracks at the bracket toes attached to longitudinal stiffeners in way of deck and bottom, SIFs were derived based on the three approaches. To obtain axial tension loads acting on the longitudinal stiffeners, long term hull girder bending moments were assumed to obey Weibull distribution of which two parameters were decided from a reference (DNV, 2014). For the complicated weld details, it was concluded that the XFEM approach could cost-effectively and accurately estimate the crack growth rates and residual lives of ship structures.

• 한국수학교육학회지시리즈B:순수및응용수학
• /
• 제20권4호
• /
• pp.233-242
• /
• 2013

Certain interesting single (or double) infinite series associated with hypergeometric functions have been expressed in terms of Psi (or Digamma) function ${\psi}(z)$, for example, see Nishimoto and Srivastava [8], Srivastava and Nishimoto [13], Saxena [10], and Chen and Srivastava [5], and so on. In this sequel, with a view to unifying and extending those earlier results, we first establish two relations which some double infinite series involving hypergeometric functions are expressed in a single infinite series involving ${\psi}(z)$. With the help of those series relations we derived, we next present two functional relations which some double infinite series involving $\bar{H}$-functions, which are defined by a generalized Mellin-Barnes type of contour integral, are expressed in a single infinite series involving ${\psi}(z)$. The results obtained here are of general character and only two of their special cases, among numerous ones, are pointed out to reduce to some known results.

• International Journal of Precision Engineering and Manufacturing
• /
• 제3권2호
• /
• pp.33-44
• /
• 2002

The problem of eigenvalues and eigenvectors is obtained from a v-notched crack in pseudo-isotropic dissimilar materials by the traction free boundary and the perfect bonded conditions at interface. The complex stress function of the two-term William's type is used. The eigenvalues are solved by a commercial numerical program, MATHEMATICA. Stress singularities for v-notched cracks in pseudo-isotropic dissimilar materials are discussed. The RWCIM(Reciprocal Work Contour Integral Method) is applied to the determination of eigenvector coefficients associated with eigenvalues with egenvalues. The RWCIM algorithm is also coded by the MATHEMATICA.

• Structural Engineering and Mechanics
• /
• 제26권5호
• /
• pp.557-568
• /
• 2007

The elastic T-stress is increasingly being recognized as an important second parameter to the stress intensity factor for fracture and fatigue assessments. In this paper, the mutual or M-contour integral approach is employed in conjunction with the Boundary Element Method (BEM) to determine the numerical T-stress solutions for cracks in plates with multiple holes. The problems investigated include plates of infinite width with multiple holes at which single or double, symmetric cracks have grown from. Comparisons of these results are also made with the corresponding solutions of finite plates with a single hole. For completeness, stress intensity factor solutions for the cracked geometries analyzed are presented as well. These results will be useful for failure assessments using the two-parameter linear elastic fracture mechanics approach.

• 대한기계학회논문집A
• /
• 제25권11호
• /
• pp.1835-1843
• /
• 2001

The energy release rate for an interface crack in anisotropic dissimilar materials was obtained by the eigenfunction expansion method and also was analyzed numerically by the reciprocal work contour integral method. It was shown that the results for orthotropic dissimilar materials are consistent with the other worker's results.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 추계학술대회 논문집
• /
• pp.752-754
• /
• 1997

The stress intensity factor for an interface crack in dissimilar materials has been obtained by many researchers. But research of the energy release rate for an interface crack in pseudo-isotropic dissimilar materials is insufficient yet. In this paper, the energy release rate for cracks in pseudo-isotropic dissimilar materials was obtained using eigenfunction expansion method and also analyzed numerically using the reciprocal work contour integral method. The results were verified by comparing with other worker's results.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
• /
• pp.629-632
• /
• 2003

This paper has been studied analysis and design of microstrip Rotman lens operating over wide band and wide steering angle by the contour integral method along with the segmentation method. All mutual coupling, internal reflections between ports with exponential taper are taken into account. Equally spaced ports are designed and realized which gives less amplitude ripple at array ports. The measured results of 12 input and 12 output lens show $\pm$1.8 dB insertion loss deviation over 6~18GHz wide frequency range and beam steering accuracy less than 1$^{\circ}$ over $\pm$53$^{\circ}$ angle and agrees well with the analysis results.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집A
• /
• pp.115-120
• /
• 2000

This paper examines that it is possible to apply RWCIM for determining eigenvector coefficients associated with eigenvalues for V-notched cracks in anisotropic dissimilar materials using the complex stress function. To verify the RWCIM algorithm, two tests will be shown. First it is performed to ascertain whether predicted coefficients associated with eigenvectors is obtained exactly. Second, it makes an examination of the state of stress for FEM and RWCIM according to a number of eigenvectors at a location far away from the V-notched crack tip.

• 한국군사과학기술학회지
• /
• 제8권4호
• /
• pp.136-145
• /
• 2005

특이응력해석을 위한 일반화된 가역상반일 경계적분식이 섬유강화복합재를 모형화한 직교 이방성 크랙평판의 수치해를 위하여 발전시켰다. 이 적분방정식은 평판경계에서의 탄성변위와 트랙션의 변수로 구성된 경계적분식의 형태로 하중이 없다는 두 크랙면의 경계조건과 유한의 탄성변형에너지의 개념에서 경계적분식에 필요한 특성해를 규정하고 대응되는 보조해를 계산하였다. 대칭모우드 I형의 중앙원공크랙평판 및 복합모우드형의 반원편측크랙 일단고정평판의 응력확대계수가 임의의 섬유방향각에 따라서 계산되었다.