• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.7 no.1
• /
• pp.75-82
• /
• 1987

It is the objective of this study to estimate J-integral by numerical analysis, in which J-integral as aparameters in fracture mechanics can be used to evaluate unstable ductile fracture which is a important problem with respect to structural stability when the scope is beyond small scale yielding criteria. For this, 8-node isoparametric singular element as crack tip element of a cracked material was used to solve plastic blunting phenomenon at crack tip, and crack opening was forced to start when J-value was exceeding fracture toughness $J_{IC}$ of the material. And crack propagation behaviour was treated by using crack opening angle. From this study, it was shown that crack opening, stable propagation and unstable opening point of the cracked material found by using J-value obtained from this study were accord with the other study, so think, J-value obtained from this study can be directly used as a parameter in fracture mechanics to deal with the problem of stable propagation of crack and unstable ductile fracture.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.3
• /
• pp.427-431
• /
• 1986

3점 굽힘 시험편, 중앙균열 인장 시험편, 콤팩트 인장 시험편에 대한 J적분식을 하나의 일반화된 형태로 유도한다. 이 일반식은 Eftis와 Liebowitz에 의해 제안된 하중과 하중점 변위 사이의 관계와 Sumpter에 의한 탄성과 소성성분 J적분의 중첩개념을 이용함으로써 유도된다. 일반식에 포함된 .eta.계수를 위 3가지 시험편에 대해서 결정한다. 위 3가지 시험편에 대한 J적분의 최종식은 하중과 하중점 변위곡선 아래의 면적을 측정하지 않아도 되는 형태로 나타난다. 본 연구의 결과식은 Landes등에 의한 실험치와 비교하여 매우 잘 일치함을 보인다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.3
• /
• pp.259-266
• /
• 2004

Detailed two-dimensional and three-dimensional finite element (FE) analyses of double-edge cracked tension (DE(T)) specimens are carried out to investigate the effect of the relative crack length and the thickness on experimental J testing schemes. Finite element analyses involve systematic variations of relevant parameters, such as the relative crack depth and plate width-to-thickness ratio. Furthermore, the strain hardening index of material is systematically varied, including perfectly plastic (non-hardening) cases. Based on FE results, a robust experimental J estimation scheme is proposed.

• Journal of the Korean Mathematical Society
• /
• v.53 no.6
• /
• pp.1261-1273
• /
• 2016

In this paper, we analyze the necessary and sufficient condition introduced in [5]: that a functional F in $L^2(C_{a,b}[0,T])$ has an integral transform ${\mathcal{F}}_{{\gamma},{\beta}}F$, also belonging to $L^2(C_{a,b}[0,T])$. We then establish the inverse integral transforms of the functionals in $L^2(C_{a,b}[0,T])$ and then examine various properties with respect to the inverse integral transforms via the translation theorem. Several possible outcomes are presented as remarks. Our approach is a new method to solve some difficulties with respect to the inverse integral transform.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.6
• /
• pp.67-73
• /
• 2001

Three dimensional, elastic-plastic finite element(FE) analyses for circumferential through-wall cracked pipes under combined tension and bending are performed using actual tensile data of stainless steel, for two purposes. The first one is to validate the recently-proposed enhanced reference stress (ERS) method to estimate the J-integral and COD for circumferential through-wall cracked pipes under combined tension and bending. The second one is to compare those results with the GE/EPRI estimations. The FE results of the J-integral and the COD, resulting from six cases of proportional and non-proportional combined tension and bending, compare very well with those estimated from the proposed method. Excellent agreements of the proposed method with the detailed FE results provide sufficient confidence in the use of the proposed method to the Leak-Before-Break(LBB) analysis of through-wall cracked pipes under combined tension and bending.

• Elastomers and Composites
• /
• v.31 no.5
• /
• pp.341-346
• /
• 1996

The fracture mechanics investigation of the thermoplastic vulcanizates(TPV) from EPDM and PP/Ionomer ternary blends was performed in terms of the J-integral by measuring fracture energy via the locus method. The TPV from ternary blends consisting of EPDM, PP and ionomer were prepared in a laboratory integral mixer by blending and vulcanizing simultaneously. Vulcanization was performed with dicumyl peroxide (DCP) and the composition of EPDM and PP was fixed at 50/50 by weight. Two kinds of poly(ethylene-co-methacrylic acid) (EMA) lonomers were used. The J-integral values at crack initiation, Jc, of the dynamically vulcanized EPDM and PP/EMA Ionomer ternary blends were affected by the cation types $(Na^+\;or\;Zn^{2+})$ and contents(5-20wt%) of the added EMA Ionomers. The ternary blend containing 20wt% zinc-neutralized EMA Ionomer and 1.0phr DCP showed the highest Jc values of the blends.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.6 s.261
• /
• pp.710-717
• /
• 2007

This paper presents plastic limit loads and approximate J-integral estimates for circumferential part-through surface crack at the interface between elbows and pipes. Based on finite element limit analyses using elastic-perfectly plastic materials, plastic limit moments under in-plane bending are obtained and it is found that they are similar those for circumferential part-through surface cracks in the center of elbow. Based on present FE results, closed-form limit load solutions are proposed. Welds are not explicitly considered and all materials are assumed to be homogeneous. And the method to estimate the elastic-plastic J-integral for circumferential part-through surface cracks at the interface between elbows and straight pipes is proposed based on the reference stress approach, which was compared with corresponding solutions fur straight pipes.

• International Journal of Control, Automation, and Systems
• /
• v.1 no.2
• /
• pp.206-209
• /
• 2003

An $H_2$/$H_{\infty}$ -controller realization is carried out by considering an entropy integral. Using J-spectral factorization, the parametrizations of all $H_{\infty}$ stabilizing controllers are derived. By the relation of a mixed $H_2$/$H_{\infty}$ control problem and a minimum entropy/$H_{\infty}$ control problem, the mixed $H_2$/$H_{\infty}$-controller state-space realization is presented.

• Journal of applied mathematics & informatics
• /
• v.20 no.1_2
• /
• pp.279-292
• /
• 2006

A reverse of Bessel's inequality in 2-inner product spaces and companions of $Gr\ddot{u}ss$ inequality with applications for determinantal integral inequalities are given.

• Korean Journal of Computational Design and Engineering
• /
• v.14 no.2
• /
• pp.122-128
• /
• 2009

The failure responses of adhesively bonded, hat stiffened structures are studied through numerical analysis using the finite element method. The responses are evaluated numerically for the bonded hat section/substrate structures containing different combinations of materials. It is studied what kind of material combinations causes the easier crack initiation in the structure. This study is conducted under plane strain conditions and J-integral via a commercial code ABAQUS as a total critical energy release criterion was used for observation on crack initiation. Also, the influence of adhesive on the structure is studied.