• 한국정밀공학회지
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• 제20권3호
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• pp.178-186
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• 2003

In order to investigate the fracture behaviors (penetration modes) and the resistance to penetration during ballistic impact of Al 5052-H34 alloy laminates, cold-rolled Al 5052-H34 alloy laminates, anodized Al 5052-H34 alloy laminates, and anodized Al 5052-H34 alloy after cold-rolling, a ballistic testing was conducted. In general, superior armor materials are brittle materials which have a high hardness. Ballistic resistance of these materials was measured by a protection ballistic limit (V$_{50}$), a statistical velocity with 50% probability fur incompletete penetration. Fracture begaviors and ballistic tolerance, described by penetration modes, ate observed from the results from the results of V$_{50}$ test and Projectile Through Plates (PTP) test at velocities greater than V$_{50}$, respectively. PTP tests were conducted with 0$_{\circ}$obliquity at room temperature using 5.56mm ball projectile. V$_{50}$ tests with 0$_{\circ}$obliquity at room temperature were concucted with projectiles that could achieve neat or complete penetration during PTP tests. Surface hardness, resistance to penetration, and penetration modes of Al 5052-H34 alloy laminates are compared to those of cold-rolled Al 5052-H34 alloy laminates and anodized Al 5052-H34 alloy laminates and anodized Al 5052-H34 cold-rolled alloy.

• 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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1629-1633
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• 2004

Liquid is commonly introduced as transversal jets in venturi scrubber which is one of the gas cleaning equipments. The jet dynamics such as penetration and breakup is of fundamental importance to the dust-collection efficiency. We have developed a model that can numerically simulate the breakup of the liquid jet in crossflow. This simulation consists of models on liquid column, jet surface breakup, column fracture and secondary droplet breakup. These models have been embedded in the KIVA3-V code. We have calculated such parameters as the jet penetration, jet trajectory, droplet size, velocity field and the volume flux distribution. The results are compared with the experimental data in this paper.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.174-181
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• 1999

In this paper the technique to predict tool wear theoretically in shearing process is suggested. The tool wear in the process affects the tolerances of final pans, metal flows and costs of processes. In order to predict the tool wear the deformation of workpiece during the process is analyzed by using non-isothermal finite element program. The ductile fracture criterion and the element kill method are also used to estimate if and where a fracture will occur and to investigate the features of the sheared surface in shearing process. Results obtained from finite element simulation, such as nodal velocities and nodal forces, are transformed into sliding velocity and normal pressure on tool monitoring points respectively. The monitoring points are automatically generated and the wear rates on these points are accumulated during the process. It is assumed that the wear depth on the tool surface is linear function of the lot sizes based upon the known experimental results. The influence of clearance between die and punch upon tool wear is also discussed.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.1053-1062
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• 1993

The effect of loading speed on soil failure was studied by using a high speed triaxial compression test. Tests were conducted at 0.35-6.2m/s loading speed to compress soil specimens of sandy loam at different moisture contents. The axial stress at fracture increased with increase in loading speed up to certain critical speeds, however they decreased as the speed up to certain critical speeds, however they decreased as the speed increased further. Experiments were also conducted in the field of sandy loam soil with the vibrating tillage tool. Tests were done at 0.33-0.85m/s tractor speed oscillating frequency 13.7hz and oscillating amplitude 59mm. The maximum oscillating velocity of tillage tool was 2.5m/s. It was observed that for the oscillating operation, initially draft slightly increased with increase in forward speed and then it decreased .For the non-oscillating operation, draft increased continuously with increase in forward speed. Approach of studying soil failure in the laboratory test can be related to the field experiments.

• 한국재료학회지
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• 제9권4호
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• pp.392-397
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• 1999

The tensile strength and water resistance of ADC12 alloy matrix composites reinforced with saffil/ceraklwool and saffil/Si particle prepared by squeeze casting have been investigated in room temperature and $250^{\circ}C$. Adhesive and scuffing wear phenomena was studied when load was changed to 10~40N and wear velocity was 2.0m/s at room temperature and $250^{\circ}C$. Generally, the morphology of tensile fractured surface revealed dimple pattern which implies ductile fracture of the composites. However, cleavage fracture was also observed in case of ADC12 alloy based saffil/Si particle composite. The maximum tensile strength of 320MPa was obtained in ADC12 alloy based composites reinforced by saffil/cerakwool(5:5) preformed fibers. In the results of dry wear test, it was observed that scuffing was occurred at 40N in room temperature and 30N for $250^{\circ}C$.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.534-541
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• 2004

The modeling of crack initiation and propagation is very important for the failure analysis of concrete. The cracking process in concrete is quite different from that of other materials, such as metal and glass, in that it is not a sudden onset of new free surface but a continuous forming and connecting of microcracks. The failure process of concrete by cracking causes irreversible deformations and stiffness degradation. Those phenomenon can be modeled using plasticity and damage theory in macroscopic aspect. In this study, a plastic-damage model based on homogenized crack model considering velocity discontinuity and damage variable which is a function of plastic strain is proposed for fracture analysis of concrete. Finally, the plastic-damage model is verified with experimental data.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.332-335
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• 1997

With the advance of precision technique, the optical system is more precise and complex and the machining method of optical element which is composed of micro-grooves is developed. Especially, the method of micro-grooving using diamond tool is used widely owing to many merit, but has problems of damage of surface roughness due to tool wear and tool fracture. This paper deals with state monitoring using AE RMS in the micro-grooving. The change of AE RMS is very small with increment of cutting velocity and depth of cut. In spite of constance magnitude of principal force in machining using diamond tool of tool wear and tool fracture, AE RMS is highly fluctuated. Because changing of cutting state has relevance to surface roughness profile, surface toughness profile is expected using AE RMS.

• 대한기계학회논문집A
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• 제32권5호
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• pp.444-450
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• 2008

The conventional studies of the aging effect on cardio-vascular system are mostly obtained from human experiences and can only provide local information. In this study, the effect of fatigue fracture of arterial wall on the blood pressure was investigated by hemodynamic analysis. The aging process was simulated with three stages. The pulse wave velocity increased with age. The systolic blood pressure increases consistently but diastolic blood pressure decreases with age. The simulated results show in good accordance with the clinical ones.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
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• pp.158-159
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• 2017

In this study, it evaluate the strain properties of fiber reinforced concrete and fiber reinforced cement composite. The types of fiber are Hooked steel fiber and it was mixed 0.5, 1.0 vol.% in concrete and 1.0, 2.0 vol.% in cement composites. The impact test was conducted by using a projectile (diameter: 25mm, velocity: 170m/s) and strain properties on the rear side of each specimen was evaluated by strain gage. After the impact test, fracture grade, fracture depth was evaluated.