• 대한토목학회논문집
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• 제26권4D호
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• pp.609-615
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• 2006

균열 및 안치공법은 노후화된 콘크리트 슬래브의 줄눈 및 균열부의 과도한 움직임으로 인하여 아스팔트 덧씌우기층에 발생되는 반사균열을 억제하기 위해 기존의 노후화된 콘크리트 포장에 적정 간격의 불연속면을 형성시켜서 각각의 불연속면에서의 움직임을 작게 유지하는 공법으로 미국 등에서는 널리 사용되고 있다. 본 연구에서는 LTPP Data를 이용하여 균열 및 안치 공법 적용 후 IRI과 포장 파손 추이를 분석하여 공법 사용에 의한 공용성 변화에 미치는 영향을 고찰하였다.

• 한국도로학회:학술대회논문집
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• 한국도로학회 2006년도 춘계학술대회 논문집
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• pp.97-104
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• 2006

• 대한기계학회논문집A
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• 제25권4호
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• pp.662-670
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• 2001

We evaluate the effectiveness and validity of J(sub)e, which comprehensively describes the effects of specimen geometry and loading type, in predicting the fatigue life of auto seat belt anchor panel. We first simplify the heat affected zone model to reduce the number of finite elements. We then establish finite element models reflecting the actual overload behavior of 3 types of seat belt anchor specimens. Using finite element models elaborately established, we obtain the effective crack driving parameter J(sub)e composed of its ductility-dependent modal components. It is confirmed that the J(sub)e concept successfully predicts the fatigue life of multi-spot welded panel structures represented by auto seat belt anchors here.

• 대한기계학회논문집A
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• 제24권3호
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• pp.701-709
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• 2000

As the welding spot forms a singular geometry of an external crack type, fatigue failure of spot-welded specimens can be evaluated by means of a fracture parameter. Recasting the load vs. fatigue life relationships experimentally obtained, we predicted the fatigue life of spot-weld specimens with a single parameter denoted the equivalent stress intensity factor. This crack driving parameter is demonstrated to successfully describe the effects of specimen geometry and loading type in a comprehensive manner. The suggested fatigue life formula for a single spot weld can play a key role in the design and assessment of spot-welded panel structures, in that the fatigue strength of multi-spots is eventually determined by the fatigue strength of each single spot. We therefore attempt to evaluate the effectiveness and validity of $K_e$ in predicting the fatigue life of auto seat belt anchor panel. We first establish finite element models reflecting the actual mechanical behavior of 3 types of seat belt anchor specimens. Using finite element models elaborately established, we then obtain the effective crack driving parameter $K_e$ composed of its ductility -dependent modal components. It is confirmed that the $K_e$ concept successfully predicts the fatigue life of multi-spot welded panel structures represented by auto seat belt anchors here.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.287-288
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• 2006

Cracks on the cylinder block of diesel engines will often happen due to cyclic load and thermal stress. According to the Classification Societies' rules, welding repairs of cylinder block made of cast irons are generally not permitted. However, such welding repairs became inevitable taking enormous cost and time for their renewal into consideration. In this study repair welding methods for the cylinder blocks, made of gray cast irons were reviewed and the tests of their welds were carried out in order to purpose the repair welding methods of packing seat and o-ring seat of cylinder block and apply them to the practice. It is concluding remarks that the suspected crack by a magnetic particle test due to different magnetic permeability can be identified, which are not associated with a mechanical discontinuity.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.346-349
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• 2001

Nowadays the amount of plastic products is increasing in modern industry. Plastic materials are continuously developed to satisfy the mechanical, physical, and chemical properties. The increasing application of plastic parts in automobile and aerospace industries is due to the fact that it can reduce the structural weight and can lessen the environmental contamination. Among many manufacturing technologies for plastic parts, the injection molding process is very attractive because of its low cost and short production time. Through various analyses of resin flow and molding process for the conventional gate and cooling mechanism, a new type of mold was designed which had different gate location and cooling systems. Newly designed ball seat has an excellent performances, i.e. diminished weld-line, residual stress density, higher magnitude less crack propagation and smaller dimensional contractions effect.

• Journal of Welding and Joining
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• 제31권6호
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• pp.17-26
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• 2013

Recent developing tendency of overlay welding on welding materials are studied by searching of NDSL, Science Direct, KIPRIS and so on. Fe, Co, Ni and WC are selected as welding materials. Development and improvement of various new overlay welding technology, especially improvement of quality and formation of crack are introduced. Also the prospective technologies of overlay welding are anticipated.

• 한국산업융합학회 논문집
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• 제12권2호
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• pp.107-112
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• 2009

The effective reinforcement methods of structure is required to improve the durability of existing structures. Recently, the continuous fiber sheets to the concrete structures are widely used in the earthquake-proof reinforcement method. This study examines suitability and effect to concrete structure of fiber by FEM analysis. The result of analysis is as follows; All specimens occurred bending tensile failure at the middle span. Ultimate strength of specimen in the RC and reinforced RC specimen were 53.9 kN, 56.3 kN respectively and it was some low by degree 0.89, 0.82 to compare with calculated result. The deflection of specimen at the middle span occurred in approximately 0.2 mm, and did linear behavior in load 20 kN by seat reinforcement. Stiffness did not decrease by occurrence in the finer crack and reinforcement beam's flexure stiffness was increased until reach in failure. To compare calculated value and analysis value, it almost equal behavior in the elastic reign and can confirm effectiveness of analysis. Crack was distributed uniformly by reinforcement of fiber seat at failure and it do not occurred stiffness decreases.

• Journal of Advanced Marine Engineering and Technology
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• 제23권3호
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• pp.331-337
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• 1999

Cracks on the cylinder block of diesel engines will often happen due to cyclic load and thermal stress. According to the Classification Societies' rules welding reparis of cylinder block made of cast irons are generally not permitted. However such welding repairs became inevitable taking enormous cost and time for their renewal into consideration. In this study repair welding methods for the clinder blocks made of gray cast irons were reviewed and the tests of their welds were carried out in order to purpose the repair welding meth-ods of packing seat and o-ring seat of cylinder block and apply them to the practice. The following conclusions are botained :1 The tensile strength of weld of cast iron more than that of base metal can be obtained by means of preheating keeping temperature above $100^{\circ}C$ between welding pass-es preventing slag inclusion peening and cramping weld metal by studs. 2. The suspected crack by a magnetic particle test due to different magnetic permeability can be identified which are not associated with a mechanical discotinuity.

• Structural Engineering and Mechanics
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• 제44권1호
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• pp.51-60
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• 2012

Concrete sleepers are essential components of the conventional railway. As support elements, sleepers are always subjective to a variety of time-dependent loads attributable to the train operations, either wheel or rail abnormalities. It has been observed that the sleepers may deteriorate due to these loads, inducing the formation of hairline cracks. There are two areas along the sleepers that are more prone to crack: the central and the rail seat sections. Several non-destructive methods have been developed to identify failures in structures. Health monitoring techniques are based on vibration responses measurements, which help engineers to identify the vibration-based damage or remotely monitor the sleeper health. In the present paper, the dynamic effects of the cracks in the vibration signatures of the railway pre-stressed concrete sleepers are investigated. The experimental modal analysis has been used to evaluate the modal bending changes in the vibration characteristics of the sleepers, differentiating between the central and the rail seat locations of the cracks. Modal parameters changes of the 'healthy' and cracked sleepers have been highlighted in terms of natural frequencies and modal damping. The paper concludes with a discussion of the most suitable failure indicator and it defines the vibration signatures of intact, central cracked and rail seat cracked sleepers.