• Nuclear Engineering and Technology
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• 제53권9호
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• pp.2977-2981
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• 2021

Corrosion fatigue crack growth (FCG) behavior of 316LN stainless steel was investigated in high-temperature pressurized water at different temperatures, load ratios (R = K_max/K_min) and rise times (t_R). The environmental assisted effect on FCG rate was observed when both the R and t_R exceeded their critical values. The FCG rate showed a linear relation with stress intensity factor range (ΔK) in double logarithmic coordinate. The environmental assisted effect on FCG rate depended on the ΔK and quantitative relations were proposed. Possible mechanisms of environmental assisted FCG rate under different testing conditions are also discussed.

• 한국생산제조학회지
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• 제7권1호
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• pp.58-68
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• 1998

Advantages of adhesively bonded joints and techniques of weight reduction have led to increasing use of structural adhesives such as LSI(large scale integration) package, automobile, aircraft in the various industries. In spite of such wide applications of adhesively bonded joints, the evaluation method of bonding strength has not been established. Stress singularity occurs at the interface edges of adhesively bonded joints and it is required to analyze it. In this paper, the stress singularity using 2-dimensional elastic boundary element method (BEM) with the changes of the lap length and adhesive for single lap joint was analyzed, and experiments of strength evaluation were carried out. As the results, the evaluating method of bonding strength considering stress singularity at interface edges of adhesively bonded joints and stress intensity factor of interface crack have been proposed in static and fatigue test.

• Structural Engineering and Mechanics
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• 제18권3호
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• pp.277-286
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• 2004

Defective metallic components and structures are being repaired with bonded composite patches to improve overall mechanical and fatigue properties. In this study, fatigue crack growth tests were conducted on pre-cracked 7075/T6 Aluminum substrates with and without bonded Boron/epoxy patches. A considerable increase in the fatigue life and a decrease in the stress intensity factor (SIF) were observed as the number of patch plies increased. The experimental results demonstrate that the patch configurations and patch thickness can enhance fatigue life by order of magnitude. Quantitative comparisons between analytical and experimental data were made, and the analytical model based on a modified Rose's analytical solution appears to best estimate the fatigue life.

• 대한기계학회논문집
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• 제17권9호
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• pp.2138-2144
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• 1993

An integral equation representation of cracks was presented which differs from well-known "dislocation layer" representation. In this new representation, the equations are written in terms of the displacement discontinuity across the crack surfaces rather than derivatives of the displacement-discontinuity. It was shown in that the new technique is well-suited to the treatment of kinked cracks. In the present paper, this integral equation representation is coupled to the direct boundary-element method for the treatment of finite bodies containing kinked cracks. The method is demonstrated for two-dimensional finite domains but extension to three-dimensional problems would appear to be possible. The resulting approach is shown to be simple, yet very accurate. accurate.

• 오토저널
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• 제13권2호
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• pp.103-111
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• 1991

To determine the effects of microstructure on the fatigue crack propagation behavior in SM45C steel, experimental investigations have been carried out with the specimens of different grain sizes and different spacings between the Fe$_{3}$C particles. Fatigue and tensile tests were conducted and the quantitative analysis of the relations between the threshold stress intensity range and grain size, interparticle spacing and yield stress were carried out. Some of the conclusions obtained are as follows; (1) .DELTA.K$_{th}$ was observed to increase with grain size and the spacing between the Fe3C particles. (2) In both pearlite and spheroidite microstructures, .DELTA.K$_{th}$ was increased when yield stress was decreased.sed.

• 한국안전학회지
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• 제17권1호
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• pp.1-5
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• 2002

An approach for the damage of delamination which is the major concern during mechanical working for composite laminate material is proposed based on linear elastic fracture mechanics. This paper presents method evaluating of damage crack length using by average thrust force with AE characteristics. Also, the relations of AE characteristics are obtained from delamination damages. We found the onset ply of the delamination and a critical energy release rate and expressed a stress intensity factor by AEcount equation.

• 대한기계학회논문집
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• 제7권2호
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• pp.145-152
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• 1983

An adhesively bonded anisotropic structure containing a part-through crack subjected to in-plane mixed mode deformations is investigated. The problem is reduced to a pair of Fredholm integral equations of the second kind by mathematical analysis. By solving these equations numerically stress intensity factors k$_{1}$ and k$_{2}$ are presented. Two cases are considered with respect to fiber orientations. Case one is to fix the fiber orientations of sound plate bonded to cracked plate with various fiber orientations. The other is to vary fiber orientations for both plates. As boundary conditions, tension and shear loading respectively, are applied to bonded anisotropic plates to observe mixed mode deformations.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.298-303
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• 2001

Most of mechanical failures are caused by repeated loadings and therefore they are strongly related to fatigue. To avoid the failures caused by fatigue, determination of an optimal shape of a structure is one of the very important factors in the initial design stage. Shape optimization for a compact tension specimen in opening mode in fracture mechanics, was accomplished by the linear elastic fracture mechanics and the growth-strain method in this study. Also shape optimization for a cantilever beam in mixed mode was carried out by the same techniques. The linear elastic fracture mechanics was used to estimate stress intensity factors and fatigue lives. And the growth-strain method was used to optimize the shape of the initial shape of the specimens. From the results of the shape optimization, it was found that shapes of two types of specimens and a cantilever beam optimized by the growth-strain method prolong their fatigue lives very much. Therefore, it was verified that the growth-strain method is an appropriate technique for shape optimization of a structure having a crack.

• 한국정밀공학회지
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• 제20권7호
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• pp.193-200
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• 2003

The energy release rate for an interface crack in pseudo-isotropic dissimilar materials was obtained by the eigenfunction expansion method using the two-term William's type complex stress function. The complex stress function for pseudo-isotropic materials must be different from that for anisotropic materials. The energy release rate for an interface crack in pseudo-isotropic dissimilar materials was analyzed numerically by RWCIM. The results obtained were verified by comparing the other worker's results and discussed.

• 오토저널
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• 제5권2호
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• pp.31-40
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• 1983

A study was made of the effect of cold working and stabilizing temperature on the fatigue properties of Aluminum alloy 5083. The amount of cold working ranged from 14% to 35% and stabilizing temperature was 120.deg. C-160.deg. C. Rotary bending fatigue test was carried out, and it was found that 1) E specimen that had been cold worked by the cold reduction of 35% and stabilized at 160.deg. C for 2 hours was showed the most excellent fatigue limit and endurance ratio and, 2) By the results of the between crack propagation behavior and stress intensity factor, E specimen was showed the better resistance to fatigue crack growth than others.