• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.69-79
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• 1996

Dynamic stress intensity factors are derives when the crack is propagating with constant velocity under longitudinal shear stress in orthotropic disk plate. General stress fields of crack tip propagating with constant velocity and least square method are used to obtain the dynamic stress intensity factor. The dynamic stress intensity factors of GLV/GTV=1(=isotropic material or transversely isotropic material) which is obtained in out study nearly coincides with Chiang's results when mode Ⅲ stress is applied to boundary of isotropic disk. The D.S.I.F. of mode Ⅲ stress is greater when α(=angle of crack propagation direction with fiber direction) is 90° than that when α is 0°. In case of a/D(a:crack length, D:disk diameter)<0. 58, the faster crack propagation velocity, the less D.S.I.F. but when crack propagation velocity arrive on ghear stress wave velocity, the D.S.I.F. but when crack propagation velocity arrive on shear stress wave velocity, the D.S.I.F. unexpectedly increases and decreases to zero.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.4
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• pp.121-128
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• 1998

In this study, when tension and bending stress act on plate simultaneously, stress intensity factor is analyzed at crack tip with using BEM(Boundary Element Method). In this analysis, stress intensity factors(S.I.F) are defined for variable ligament, aspect and stress ratio($\sigma$T/$\sigma$B). Consequently, predicted that crack grow to depth direction at low aspect and ligament ratio in tension stress and to surface direction in bending stress. Tension and bending stress act on plate same time, effect of tension stress in the first stage and effect of bending stress in the after stage was to observed. The outbreak of secondary crack in backside is under the control of stress amplitude and predict that the point of outbreak is mear backside.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.269-274
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• 2001

Applications of Brazing in the studying fields such as High-Speed Machining are very increasing in various industry fields. Therefore, Applying to the fracture mechanics by numerical analysis method is very important to analyse the crack problem Dissimilar Materials in Brazed Interface. In this study, Stress intensity Factor (S.I.F) is analysed to investigate crack behavior on the crack tip of dissimilar materials in brazed interface such as a Hardmetal and a HSS by two dimensional(2-D) Boundary Element Method (BEM). Kelvin's solution was used as a fundamental solution in BEM analysis and stress extrapolation method was used to determine Stress Intensity Factor.

• Journal of the Korean Society of Industry Convergence
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• v.7 no.4
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• pp.355-361
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• 2004

The finite element method were used to determine the stress intensity factor of cracked plate. The stress method, displacement method and J Integral are most popular finte element method. ANSYS proposed another a kind of displacement method. In this paper, it was examined that the accuracy and utility of the ANSYS method could believable to determine the stress intensity factors of centered inclined crack. Generally, inclined crack has two portion of stress intensity factors, tensile mode F1 and shear mode F2. For the purpose of increasing the accuracy of stress intensity factors, examined the effect of the numbers of nodes and elements, crack tip element size and number of partition of the crack tip vicinity. It was found that the method proposed by ANSYS is useful and has high accuracy. Accuracy of calculated stress intensity factors was increased by increase of the number of nodes and elements, and at the small size of crack tip elements can get more highly accuracy.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.5
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• pp.42-50
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• 1991

According as the members and inner and outer plates of the automobile body structure have been thinned their thickness and have become high strength, each part of the body structure has been put more severe stress condition. Therefore, it has been increasingly required to improve the fatigue strength of the spot welded structures. As one of the improving methods for such problem, the author had previously proposed the method of alleviating stress concentration at nugget edge of the spot weld part and improving its fatigue strength [1]. But, because fatigue strength of the spot welded lap joint is influenced by its geometrical and mechanical factors, welding condition and etc., there needs a quantitative and systematic estimation method of them. In this report, by considering nugget edge of the spot weld part of the spot welded lap joint subjected to tensile load to the ligament crack, fatigue strength of various spot welded lap joints was estimated with the stress intensity factor (S.I.F.) K which is fracture mechanical parameter. It is known that evaluation of fatigue strength of the spot welded lap joint by the stress intensity factor (S.I.F.) K is more effective than the maximum stress $(\sigma_{ymax}$) at edge of the spot weld part on the center line of width of the plate.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.380-385
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• 2000

In this study, geometric shape and crack in welded interface of the air cooled heat exchanger Fin-Tube of Dissimilar Meterials was analysed. The object of study is to understand the behavior of Stress Intensity Factor for fin length, flash thickness, flash length, symmetric and asymmetric cracks of comming from the manufacturing process. Stress Intensity Factor was analysed by BEM. Kelvin's solution was used as a fundamental solution in BEM analysis and stress extrapolation method was used to determine Stress Intensity Factor.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.434-439
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• 2000

In this paper, in order to study the geometric factor effect of a circular hole near a crack tip in a semi-infinite plate, the Dimensionless Stress Intensity Factor, $F(=\frac K {\sigma {\sqrt{\pi a}}})$ is analyzed at the crack tip using a two Dimensional Boundary Element Method (BEM) program which is known as superior in Fracture Mechanics. Kelvin's solution was used as a fundamental solution in BEM analysis and displacement extrapolation method was used to determine Stress Intensity Factor.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3105-3114
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• 1993

previously, several basic studies in the experimental analysis of stress intensity factors of cracks by slab analogy have been presented by authors. But, for the application of above mentioned method to the analysis of the arbitrarily distributed cracks, there still is several bottlenecks to be overcome in terms of its experimental process and data treatment. Moreover, authors recently proposed an improved experimental method to use the fixed slab analogy device which has promised more accurate measurement of S.I.F. of small cracks. In this paper, for the completion of slab analogy analysis of distributed cracks, a grating imaginary rotation method is introduced. And, to prove its validity, this combined method is applied to the determination of stress intensity factors of theoretically known distributed cracks. The results show good agreement with the existing theoretical solutions and physical crack propagation tendencies.

• Journal of Mechanical Science and Technology
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• v.15 no.1
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• pp.44-51
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• 2001

One of the recent issues in design of the spot-welded structure such as the automobile body is to develop an economical prediction method of the fatigue design criterion without additional fatigue test. In this paper, as one of basic investigation for developing such methods, fracture mechanical approach was investigated. First, the Model I, Mode II and Mode III, stress intensity factors were analyzed. Second, strain energy density factor (S) synthetically including them was calculated. And finally, in order to decide the systematic fatigue design criterion by using this strain energy density factor, fatigue data of the ΔP-N(sub)f obtained on the various in-plane bending type spot-welded lap joints were systematically re-arranged in the ΔS-N(sub)f relation. And its utility and reliability were verified by the theory of Weibull probability distribution function. The reliability of the proposed fatigue life prediction value at 10(sup)7 cycles by the strain energy density factor was estimated by 85%. Therefore, it is possible to decide the fatigue design criterion of spot-welded lap joint instead of the ΔP-N(sub)f relation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.1
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• pp.18-23
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• 1985

In the fracture mechanics, the determination of the stress intensity factor value is vital for the prediction of a material fracture behavior. So many data concerning to the S.I.F. have been presented by many investigations to meet endless requrement. In this paper, the stress intensity factors of a sheet with an eccentrically inclined crack subjected to the pure bending moment were investigated theoretically by using of the complex mapping function to determine the Muskelishvili's comlex stress functions. Moreover, the theoretical value was compared with the result obtained from photoelastic esperiment. As a result, it was confirmed that both values coincided with satisfactorily within the margin of 2-3% devition; The results theoretically derived are right.