• Composites Research
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• v.26 no.2
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• pp.79-84
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• 2013

The prediction and analysis procedure of fatigue damage crack growth life for a stiffener bonded composite laminate panel including center hole and edge notch damage, was studied. It was performed on the basis of fatigue damage growth test results on a laminated skin panel specimens and the analysis results of stress intensity factor for the stiffener bonded composite panel. According to the comparison between experimental test and prediction results of fatigue damage growth life, it was concluded that the residual strength and damage tolerance assessment can be carried out along to the edge notch crack growth.

• Bulletin of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.50-54
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• 1995

선박의 구조설계단계에서 최종붕괴강도를 설계기준으로 삼는 경우는 거의 없으나 최근에 각국 선급에서 최종붕괴강도를 의무적인 설계기준으로 삼기 위해 자체적인 해석법과 설계식을 제시 하고 규정화하는 작업을 진행시키고 있다. [12, 17, 31, 32]. 1994년 ISSC [1]에서도 토론된바와 같이 특히 새로운 구조방식을 가진 선박의 합리적인 구조설계를 위하여는 해상플렛폼의 구조설 계시와 마찬가지로 삼아야 할 것이다. 본고에서는 선각거더의 최종붕괴강도에 대한 해석법과 간이계산식에 관한 연구동향을 문헌조사를 통하여 분석하였다. 그 결과 순수굽힘모멘트가 작용 하는 문제의 경우 최종붕괴강도 해석법은 어느정도 확립되었다고 판단되지만 최종붕괴강도의 간이계산식은 아직도 정도 등의 면에서 개선의 여지가 남아 있다고 생각된다. 앞으로 순수 굽 힘모멘트뿐만아니라 조합하중을 받는 경우와 피로균열을 비롯한 초기구조손상을 가진 노후화된 선박에 대한 최종붕괴강도를 보다 정밀하게 해석하기 위한 해석법의 개발과 간이계산식의 도 출이 필요하다고 사료된다. 또한, 충돌, 좌초, 폭발 등에 기인된 선각거더의 붕괴강도 평가를 위한 해석법의 개발도 앞으로 남은 과제중의 하나이다.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.211-221
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• 2007

A structural reliability analysis of fatigue truck model for fatigue failure of highway steel bridges was performed by applying the Miner's fatigue damage rule expressed as a function of various random variables affecting fatigue damage. Among the variables, the statistical parameters for equivalent moment, impact factor, and loadometer were obtained by analyzing recently measured domestic traffic data, whereas the parameters on fatigue strength, girder distribution factor, and headway factor of the measured data available in the literature were used. The effects of various fatigue truck models, fatigue life, ADTT, fatigue detail category, loadometer, and gross vehicle weight of fatigue truck on the reliability index of fatigue damage were analyzed. It is expected that the analytical results presented herein can be used as a basic background material in the calibration of both fatigue design truck and fatigue load factor of LRFD specification.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1315-1321
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• 2011

Prior to the experimental and production stages of goods, the strengths should be evaluated in the design stage. The introduction of commercial codes at the design stage gives benefits such as cost and time economies in the production and strength evaluation. In this study, structural analysis and fatigue analysis are carried out using ANSYS modeling of the 3D geometry of the wheel. In a comparison of dish-type and spoke-type wheels, it is shown that the deformation and maximum equivalent stress for the dish-type wheels are lower than those for spoke-type wheels. Nevertheless, spoke-type wheels are often used because they are light and have exhibit excellent cooling performance. Furthermore, according to the results of life analysis, aluminum wheels show improved resistance to fatigue compared to steel wheels.

• Computational Structural Engineering
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• v.6 no.3
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• pp.113-123
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• 1993

Most of the ship structures and offshore structures are constructed through the welding and they are always subjected to variable loads. In this study, fatigue and stress concentration of the various types of welding connections due to the variable loads are investigated by using numerical approach, and comparisons between numerical analysis and experiments are performed. Fillet weld, full penetration weld and partial penetration weld characteristics are studied by using parameters such as penetration length, welding leg length, size and penetration angle. Based on this study, it is suggested that the fillet welding can be replaced with the penetration welding in some cases. The results of this study can be used as guidelines for actual welding problems in the shipyards.

• Journal of Welding and Joining
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• v.23 no.6
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• pp.18-28
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• 2005

본 일반 지침은 용접 이음부나 구조물의 피로강도 평가에 사용되는 기준응력 계산에 관한 내용으로 핫스팟 응력(Hot Spot Stress, 이하 HSS)이라고 칭하는 응력 평가용 해석 기술 및 관련 내용을 다룬다. 국제용접협회 (IIW: International Institute of Welding)발간 지침서의 주요내용에 대한 간략한 소개와 함께 대한용접학회 용접강도연구위원회의 Round-Robin 시험결과를 바탕으로 유한요소 응력해석 기반 용접 이음부의 HSS 평가 방법에 관한 내용을 정리하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1179-1185
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• 2011

Cold and hot-rolled carbon steel sheets are commonly used in railroad cars or commercial vehicles such as the automobile. The sheets used in these applications are mainly fabricated by spot welding, which is a type of electric resistance welding. However, the fatigue strength of a spot-welded joint is lower than that of the base metal because of high stress concentration at the nugget edge of the spot-welded part. In particular, the fatigue strength of the joint is influenced by not only geometrical and mechanical factors but also the welding conditions for the spot-welded joint. Therefore, there is a need for establishing a reasonable criterion for a long-life design for spot-welded structures. In this thesis, ${\Delta}P-N_f$ relation curves have been used to determine a long-life fatigue-design criterion for thin-sheet structures. However, as these curves vary under the influence of welding conditions, mechanical conditions, geometrical factors, etc. It is very difficult to systematically determine a fatigue-design criterion on the basis of these curves. Therefore, in order to eliminate such problems, the welding residual stresses generated during welding and the stress distributions around the weld generated by external forces were numerically and experimentally analyzed on the basis of the results, reassessed fatigue strength of gas welded joints.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.339-344
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• 2013

Hot forming using boron steel is currently used for manufacturing low-weight automobile body parts, and a high tensile strength of about 1,500 MPa is obtained after hot forming. However, a high fatigue life is a more important factor than high strength when it is used for automobile suspension parts. A tubular torsion beam axle (TTBA) is one of these suspension parts, and this research deals with the fatigue characteristic of TTBA using hot forming. The low cyclic fatigue life of boron steel is investigated according to the cooling method. In addition, a structural and fatigue analysis of TTBA is performed to predict the fatigue life. The stress concentration that occurs in the tubular torsion beam is found, and the longest fatigue life occurs when rapid cooling is utilized in the TTBA fabrication.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.2
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• pp.148-154
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• 2009

Type A LPG Carrier is the ship using the low temperature independent cargo tank separate from the hull, which has various support structures for laying independent tanks on the hull. In this paper, the direct strength analysis for the support structures has been performed through the direct load analysis, load transfer, stress analysis and strength assessment. Also, a rational modeling method of support structures has been proposed to obtain the dynamic load between the hull and the separate tank.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.3
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• pp.337-342
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• 2011

Medical lift column controlling the vertical position while supporting heavy eccentric load should have the high fatigue strength as well as the extremely low structural deflection and vibration in order to maintain the positioning accuracy. The lift column driven by a induction motor is generally in a three-step sliding boom structure and exhibits the time-varying stress distribution according to the up-and-down motion. This study is concerned with the numerical prediction of the fatigue strength of the lift column subject to the time-varying stress caused by the up-and-down motion. The stress variation during a motion cycle is obtained by finite element analysis and the fatigue life is predicted making use of Palmgren-miner's rule and S-N curves. In order to secure the numerical analysis reliability, a 3-D FEM, model in which the detailed lift column structure and the fitting parts are fully considered, is generated and the interfaces between lift column and pads are treated by the contact condition.