• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.35-38
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• 2005

The Objective of this work was to design Composite Antenna Structures (CAS) and investigate impact behavior of CAS which was various curvature. This term, CAS, indicates that structural surface becomes antenna. Constituent materials were selected considering electrical properties, dielectric constants and tangent loss as well as mechanical properties. For the antenna performance, microstrip antenna layers inserted into structural layers were designed for satellite communication at the resonant frequency of 12.5 GHz and final demonstration article was. After making five kinds of curved CAS, which radii of curvature are flat, 200, 150, 100, 50 mm. The antenna performance changed in accordance with variation of curvature. The Reflection coefficient was independent of curvature but the gain decreased with the radius of curvature. The impact test equipment was Dyna-8250 drop weight tester. The impact characteristic in accordance with curvature is maximum absorb energy is same each other. The impact energy was 8.5 J. For various Impact energy test, five energy levels 3 J, 5 J, 7 J, 10 J, 20 J were used. The performance of impact damaged antenna was estimated by measuring the return loss and the radiation pattern. It was revealed that the performance of antenna was not related to the impact damage. Because the impactor did not damage the patch directly. CAS have good impact stability for the antenna performance.

• 한국산학기술학회논문지
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• 제11권1호
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• pp.7-12
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• 2010

본 논문에서는 무 펀치 피어싱 공정 (기존 피어싱 공정에서 펀치 대신 유압을 사용)을 통해 형성된 구멍에서 내부에 수직 벽을 형성시키는 데 중요한 역할을 하는 공정 인자를 찾기 위한 최적화 해석을 수행하였다. 최적화 기법으로는 다꾸치법을 사용하였다. 또한 수직 벽 형성을 해석하는데 있어서는 연성파괴이론 중 하나인 Lemaitre 손상이론을 차용하였다. 최적화 해석 결과 수직벽 형성에 가장 큰 영향을 주는 인자로서 '다이의 모서리 반경'이 선정되었다.

• Nuclear Engineering and Technology
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• 제35권2호
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• pp.144-153
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• 2003

The object of this paper is the probabilistic failure analysis on the cladding performance of WPF(Whole Pin Furnace) test fuel pins under transient conditions, and analysis of the KALIMER fuel pin using the preceding analysis. The cumulative damage estimation and Weibull probability estimation of WPF test are performed. The probabilistic method was adapted for these analyses to determine the effective thickness thinning due to eutectic penetration depth. In the results, it is difficult to assume that a brittle layer depth made by eutectic reaction is all of the thickness reduction due to cladding thinning. About 93% cladding thinning of the eutectic penetration depth is favorable as an effective thickness of cladding. And the unreliability of the KALIMER driver fuel pin under the same WPF test condition is lower than that of the WPF pin because of the higher plenum-fuel volume ratio and lower cladding inner radius vs. thickness ratio. KALIMER fuel pin developed from conceptual design has a more stable transient performance for a failure mechanism due to fission gas buildup than the WPF pin.

• 소성∙가공
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• 제30권4호
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• pp.179-185
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• 2021

Lithium ion batteries are generally manufactured by laser and etching using aluminum thin sheet. These processes are relatively expensive and have low productivity. In this study, blanking process of aluminum thin sheet for lithium ion battery was employed to replace laser cutting and etching process, all to reduce the production cost and improve productivity. Mechanical properties for aluminum and coating were determined by experimental results and rule of mixture for FE analysis of blanking process. Normalized Cockcroft-Latham criteria was also applied to describe shear behavior and critical damage values were determined by comparison of analytical and experimental result. We performed FE analysis to investigate the effects of clearance and punch-die radius on sheared surface of aluminum thin sheet and to determine optimal process condition. We manufactured the die set using the determined optimal process and conducted an experiment to confirm the feasibility of blanking process. The sheared surface of manufactured product was observed by optical microscope. As a results, the proposed process conditions successfully achieved the dimensional requirement in production of lithium ion battery parts.

• Geomechanics and Engineering
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• 제35권4호
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• pp.411-424
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• 2023

Reasonable estimates of tunnel lining dislocations in the operation stage, especially under longitudinal differential settlement, are important for the design of waterproof gaskets. In this paper, a modified shell-joint model is proposed to calculate shield tunnel dislocations under longitudinal differential settlement, with the ability to consider the nonlinear shear stiffness of the joint. In the case of shell elements in the model, an elastoplastic damage constitutive model was adopted to describe the nonlinear stress-strain relationship of concrete. After verifying its applicability and correctness against a full-scale tunnel test and a joint shear test, the proposed model was used to analyze the dislocation behaviors of a shield tunnel in Shanghai Metro Line 2 under longitudinal differential settlement. Based on the results, when the tunnel structure is solely subjected to water-earth load, circumferential and longitudinal joint dislocations are all less than 0.1 mm. When the tunnel suffers longitudinal differential settlement and the curvature radius of the differential settlement is less than 300 m, although maximum longitudinal joint dislocation is still less than 0.1 mm, the maximum circumferential joint dislocation is approximately 10.3 mm, which leads to leakage and damage of the tunnel structure. However, with concavo-convex tenons applied to circumferential joints, the maximum dislocation value reduces to 4.5 mm.

• Computers and Concrete
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• 제33권4호
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• pp.373-384
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• 2024

In this study, a novel mountain train system was developed that can run along a steep gradient of 180 ‰ and sharp curve with a minimum radius of 10 m. For this novel mountain train, an embedded precast concrete rack rail track was implemented to share the track with an automobile road and increase constructability in mountainous regions. The embedded rack rail track is connected to a hydraulically stabilized base (HSB) layer with shear anchors, which must have sufficient longitudinal resistance because they bear most of the traction forces originated from the rack rail and longitudinal loads owing to the steep gradient. In addition, the damage to the shear anchor parts, including the surrounding concrete, must be strictly limited under the service load because the maintenance of shear anchors inside the track is extremely difficult after installation. In this study, the focus was made on the shear anchor behavior and design an embedded rack rail track, considering the serviceability and ultimate limit states. Accordingly, the design loads for mountain trains were established, and the serviceability criteria of the anchor were proposed. Subsequently, the resistance and damage of the shear anchors were evaluated and analyzed based on the results of several finite element analyses. Finally, the design method of the shear anchors for the embedded rack rail track was established and verified.

• 한국항해항만학회지
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• 제45권3호
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• pp.109-116
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• 2021

울산항 부두에 이중 접안하여 환적작업 중이던 케미컬 탱커선 폭발로 주변 선박화재 등 울산항 내에서 큰 피해가 발생하였다. 유사 사고의 재발을 방지하기 위한 후속 조치로 '항만 내 위험물 안전관리 종합대책'이 수립되었으며 사고 발생 시에 폭발 위험성과 항내 주요 시설에 대한 영향 등을 고려한 위험물 환적부두의 지정이 요구된다. 본 연구는 폭발 위험성 기반의 환적부두 제시를 위하여 울산항 주요 환적화물 대상의 Fire & Explosion Index 평가를 실시하였다. 스티렌모노머와 벤젠의 Fire & Explosion Index 평가결과 심각한 폭발 위험성을 확인하였고, 평가결과를 기준으로 노출반경을 산출 하였다. 노출반경 결과를 기반으로 주요 부두별 위험범위를 산정하였으며, 항만시설, 주변 위험시설 및 거주시설을 고려한 환적가능 부두 후보지로 12개 부두를 제시하였다. 본 연구는 위험반경만을 고려하였기 때문에 향후 실질적인 위험물 환적 부두의 지정 시에는 해상교통안전성, 부두 및 계류시설, 안전설비 및 비상대응을 위한 접근성 등을 종합적으로 고려하여 결정하여야 할 것이다.

• Smart Structures and Systems
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• 제33권2호
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• pp.165-175
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• 2024

Rotating beams play a crucial role in representing complex mechanical components that are prevalent in vital sectors like energy and transportation industries. These components are susceptible to the initiation and propagation of cracks, posing a substantial risk to their structural integrity. This study presents a two-stage methodology for detecting the location and estimating the size of an open-edge transverse crack in a rotating Euler-Bernoulli beam with a uniform cross-section. Understanding the dynamic behavior of beams is vital for the effective design and evaluation of their operational performance. In this regard, modal parameters such as natural frequencies and eigenmodes are frequently employed to detect and identify damages in mechanical components. In this instance, the Frobenius method has been employed to determine the first two natural frequencies and corresponding eigenmodes associated with flapwise bending vibration. These calculations have been performed by solving the governing differential equation that describes the motion of the beam. Various parameters have been considered, such as rotational speed, beam slenderness, hub radius, and crack size and location. The effect of the crack has been replaced by a rotational spring whose stiffness represents the increase in local flexibility as a result of the damage presence. In the initial phase of the proposed methodology, a damage index utilizing the slope of the beam's eigenmode has been employed to estimate the location of the crack. After detecting the presence of damage, the size of the crack is determined using a Genetic Algorithm optimization technique. The ultimate goal of the proposed methodology is to enable the development of more suitable and reliable maintenance plans.

• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1410-1417
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• 2006

The metal processing system usually consists of various components such like motors, work rolls, backup rolls, idle rolls, sensors, etc. Even a simple fault in a single component in the system may cause a serious damage on the final product. It is therefore necessary to diagnose the faults of the components to detect and prevent system failure. Especially, the defects in a work roll are critical to the quality of strip. It is especially difficult to detect faults of a roll by using the existing frequency analysis method if the speed of the roll is changing. In this study, a new diagnosis method for roll eccentricity under the roll speed changes was developed. The new method was induced from analyzing the rolling mechanism by using rolling force models, radius-speed relationship, and measured rolling force, etc. Simulation results by using the field data show that the proposed method is very useful.

• 대한정형외과스포츠의학회지
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• 제7권1호
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• pp.8-14
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• 2008

Elbow joint injuries during exercise mostly occur by repeated stress to the joint than direct trauma. A pitcher who uses his arm above his head is most likely to be injured. So learning the right way to exercise and gaining the strength by maturating the body are essential for diminishing the chance of injury. On lateral ulnar tendon injury, which is most commonly injured area on elbow joint, pitchers generally complain of pain in arm movement above head and reduction of velocity, accuracy, and number of pitching. When there is pain on upper arm in harsh using, the stress fracture must be thought and epicondylar physis fracture of medial arm can occur by repeated abduction stress and contraction of flexors on forearm on children with immature skeleton. Osteochondritis dissecans of capitullum occur in young athletes who use there upper limb continuously lifting weights and gym work. And stress of abduction-extension includes damage of soft tissue and bone components, post medial crush syndrome, lateral ulnar ligament injury, extensor-abductor injury, stress of radius- capitullum are in this category.