• Journal of Welding and Joining
• /
• v.18 no.5
• /
• pp.33-40
• /
• 2000

Fatigue crack propagation life of weld toe crack through residual stress field was estimated with Elber's crack concept. Propagation of weld toe crack is heavily influenced by residual stress caused by welding process, so it is essential to take into account the effect of residual stress on the propagation life of weld toe crack. Fatigue crack at transverse and longitudinal weld toe was studied respectively, which represent typical weld joint in ship structure. Numerical and experimental studies are performed for both cases. Residual stress near weldment was estimated through nonlinear thermo-elasto-plastic finite element method, and residual stress intensity factor with Glinka's weight function method. Effective stress intensity factor was calculated with Newman-Forman-de Koning-Henriksen equation which is based on Dugdale strip yield model in estimating crack closure level U at different stress ratio. Calculated crack propagation life coincided well with experimental results.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.4
• /
• pp.197-202
• /
• 2000

A simple numerical procedure is presented to determine the stress intensity factors for crack in a stiffened panel subjected to a uniaxial uniform stress normal to the crack. Two types of stiffened panels are analyzed by the finite element method for various values of crack lengths, stiffness ratios, and stiffener spacings. From the finite element solution, the stress intensity factors were determined by using hybrid extrapolation method. Results are presented in graphical forms for upper mentioned parameters.

• Journal of the Korean Society of Safety
• /
• v.11 no.4
• /
• pp.115-121
• /
• 1996

This paper describes an analysis of the stress intensity factor (SIF) of the presented cracks in LNG piping. The stress analysis used the Finite Element Method. The stress Intensity factor calculated Raju & Newmann equation and ASME Section XI method. The cracks in the flanges are found to be influenced by temperature, but the cracks of the piping are found not to be influenced by temperature. If the cracks shape in the flanges and the cracks shape of the piping are same each other, the cracks in the flange will be dangerous more than the cracks of the piping.

• Speech Sciences
• /
• v.13 no.4
• /
• pp.89-105
• /
• 2006

This study examines the phonetic realizations of English word stress to identify the influence of experiment method on experiment results. Stimuli uttered by native and Korean ESL beginners in authentic conversations are extracted to be shuffled according to their positions in utterances and information structure. Results indicate that the acoustic characteristics of English word stress are realized depending on its position in utterances. The native speakers correlate the stressed syllables in shorter duration with higher pitch and stronger intensity at sentence-final positions unlike the previous experiments and the traditional definition that stressed syllables are uttered in longer duration with higher pitch and stronger intensity; at sentence-medial positions, the native speakers correlate the stressed syllables in longer duration with higher pitch and no regularity in intensity or in shorter duration with lower pitch and intensity depending on their conversational intention. Korean ESL beginners correlate the stressed syllables in shorter duration regardless of positions in sentences with no regularity in pitch and intensity. This study, thus, shows that a different experiment method may result in different results on the phonetic realizations of English word stress.

• Structural Engineering and Mechanics
• /
• v.20 no.3
• /
• pp.335-346
• /
• 2005

The T-stress of cracks in elastic sheets is solved by using the fractal finite element method (FFEM). The FFEM, which had been developed to determine the stress intensity factors of cracks, is re-applied to evaluate the T-stress which is one of the important fracture parameters. The FFEM combines an exterior finite element model with a localized inner model near the crack tip. The mesh geometry of the latter is self-similar in radial layers around the tip. The higher order Williams series is used to condense the large numbers of nodal displacements at the inner model near the crack tip to a small set of unknown coefficients. Numerical examples revealed that the present approach is simple and accurate for calculating the T-stresses and the stress intensity factors. Some errors of the T-stress solutions shown in the previous literature are identified and the new solutions for the T-stress calculations are presented.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1998.03a
• /
• pp.123-128
• /
• 1998

In fracture problems, stress intensity factors obtained theoretically and experimentally have been effectively utilized in the analytical evaluation of the cracks effect. The effect of surface crack of a cylindrical and a hollow cylindrical bar is investigated, as well as the effect of the thickness of a hollow cylindrical bar and inclined crack of a hollow cylinder subjected to torsion moment. In this study, stress intensity factor Km of mode III which expresses the stress state in the neighborhood of a crack tip is used. Stress analysis was conducted of the inside of a hollow cylinder in the axial direction of three dimensional crack tip subjected to torsion moment by combining the caustics method and the stress freezing method.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.7 no.5
• /
• pp.46-52
• /
• 1998

In fracture problems, stress intensity factors obtained theoretically and experimentally have been effectively utilized in the analytical evolution of the cracks effect. The effect of surface crack of a cylindrical and a hollow cylindrical bar is investigated, as well as the effect of the thickness of a hollow cylindrical bar and inclined crack of a hollow cylinder subjected to torsion moment. In this study, stress intensity factor Km of mode III which expresses the stress state in the neighborhood of a crack tip is used. stress analysis was conducted on the inside of hollow cylinder inthe axial direction of three dimensional crack tip subjected to torsion moment by combining the caustics method and the stress freezing method.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.11
• /
• pp.2390-2398
• /
• 2002

For integrity analysis of nuclear reactor pressure vessel, including the Pressurized thermal shock analysis, the fast and accurate calculation of the stress intensity factor at the crack tip is needed. For this, a simple approximation scheme is developed and the resulting stress intensity factors for axial semi-elliptical cracks in cylindrical vessel under various loading conditions are compared with those of the finite element method and other approximation methods, such as Raju-Newman's equation and ASME Sec. Xl approach. For these, three-dimensional finite-element analyses are performed to obtain the stress intensity factors for various surface cracks with t/R = 0.1. The approximation methods, incorporated in VINTIN (Vessel INTegrity analysis-INner flaws), utilizes the influence coefficients to calculate the stress intensity factor at the crack tip. This method has been compared with other solution methods including 3-D finite clement analysis for internal pressure, cooldown, and pressurized thermal shock loading conditions. The approximation solutions are within $\pm$2.5% of the those of FEA using symmetric model of one-forth of a vessel under pressure loading, and 1-3% higher under pressurized thermal shock condition. The analysis results confirm that the VINTIN method provides sufficiently accurate stress intensity factor values for axial semi-elliptical flaws on the surface of the reactor pressure vessel.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.9
• /
• pp.1700-1710
• /
• 1992

The boundary element method is applied to determine thermal stress intensity factors for a cusp crack in transient state. In the steady temperature field, numerical values of thermal stress intensity factors for a Grifith crack and a symmetric lip cusp crack in a finite body are in good agreement within .+-. 5% with the previous solutions. In transient state, the numerical values of thermal stress intensity factors for the Griffith crack are also in good agreement with the pervious solutions. In both steady and transient states, those for the symmetric lip cusp crack with the crack surface insulated or fixed to the constant temperature are calculates for various effective crack lengths, configuration parameters and uniform heat flow angles. The variations of the thermal boundary conditions of the crack surface have a effect on stress intensity factors. The signs on the values of thermal stress intensity factors can be changed in time variation.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.2
• /
• pp.331-341
• /
• 1993

The propagating crack problems under dynamic antiplane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems by theoretical method or experimental method in orthotropic material, it is important to know the dynamic stress intensity factor in the vicinity of crack tip. Therefore the dynamic stress field and dynamic displacement field with dynamic stress intensity factor of orthotropic material in mode III were derived. When the crack propagation speed approachs to zero, the dynamic stress components and dynamic displacement components derived in this paper are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determined by using the concept of crack closure energy with the dynamic stresses and dynamic displacements derived in this paper. Finally, the characteristics of crack propagation are studied with the properties of orthotropic material and crack speed. The variation of angle .alpha. between fiber direction and crack propagating direction and crack propagation speed fairly effect on stress component and displacement component in crack tip. The influence of crack propagation speed on the speed on the stress and displacement is greater in the case of .alpha.=90.deg. than in the case of .alpha.=0.deg. and the faster the crack propagation speed, the greater the stress value and displacement value.