• 대한기계학회논문집
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• 제18권11호
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• pp.2894-2901
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• 1994

Many researchers presented a probabilistic and statistical property of the material strength. However, the study on probabilistic and statistical property of fatigue fracture toughness has not been nearly presented. Major objectives in this paper are to compare the statistical test results of fatigue fracture toughness with those obtained in the tensile experiments, and to recognize the size effect for the probabilistic and statistical property by using specimens with various thickness.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 The 8th Asian Symposium on Precision Forging ASPF
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• pp.51-54
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• 2003

Internal defects such as chevron crack occasionally occur in the process of cold extrusion or cold drawing. It is known that the existence and property of inclusion greatly influences the generation of the internal crack. However, in the plastic working field, research about the effect of the inclusion on the fracture is not theoretically analyzed. This paper describes effects of the physical property of inclusion on the internal fracture generation in the process. Prediction of fracture was evaluated by critical damage value calculated by the equation of Cockcroft & Latham and its change by the inclusion physical property such as size and stiffness was investigated.

• 한국산업융합학회 논문집
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• 제24권4_2호
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• pp.435-441
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• 2021

This research was performed to study the effect of the Ni + Mo addition on the fatigue properties in 12Cr steel. After heat treatment of 12Cr steel and 12Cr-Ni-Mo steel, tensile tests, impact tests, hardness tests, and rotary bending fatigue tests were performed, respectively. The fatigue fracture surface was observed and analyzed using SEM and EDS. The fatigue limit of 12Cr steel was 554 MPa, which was 49 MPa higher than 505 MPa of 12Cr-Ni-Mo steel. Striations, which are the shape of the typical fatigue fracture surface, were observed at the fracture surface near the starting point of fatigue fracture in the 12Cr steel and 12Cr-Ni-Mo steel. However, unlike the case of 12Cr steel, 12Cr-Ni-Mo steel also had a mixed fracture surface with the fatigue and the ductile fracture surface. When brittle non-metallic inclusions exist near the starting point of fatigue failure, the crack propagation was further promoted and the fatigue life was drastically reduced.

• Computers and Concrete
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• 제13권1호
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• pp.31-47
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• 2014

This research is focused on obtaining the fracture property of steel fiber reinforced concrete(SFRC) specimens at early ages of 1, 2, 3 and 7-day, respectively. For this purpose, three point bending tests of nine groups of SFRC beams with notch of 40mm depth and different steel fiber ratios were conducted. The experimental results of early age specimens were compared with the 28-day hardened SFRC specimens. The test results indicated that the steel fiber ratios and curing age significantly influenced the fracture properties of SFRC. A reasonable addition of steel fiber improved the fracture toughness of SFRC, while the fracture energy of SFRC developed with curing age. Moreover, a quadratic relationship between splitting strength and fracture toughness was established based on the experiment results. Additionally, afinite element (FE) method was used to investigate the fracture properties of SFRC.A comparison between the FE analysis and experiment results was also made. The numerical analysis fitted well with the test results, and further details on the failure behaviors of SFRC could be revealed by the suggested numerical simulation method.

• 한국정밀공학회지
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• 제20권12호
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• pp.198-204
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• 2003

The bone fracture healing is simulated by using one of the complex system rules, named cellular automata method. It is assumed that each cell has property of Bone, Cartilage or Fibrous connective tissue. Nine local rules are adopted to change the property of each cell against the mechanical stimulus, which consists of the strain energy density, and the existence of bone in the surroundings. Two dimensional sheep metatarsal model is considered and the bone fracture healing is simulated. The simulation results agree well with those obtained by using fuzzy logic model and experimental data. The cellular automata method found to be one of the simulation methods to express the bone fracture healing. The cellular automata method is expected to be effective in representing biological phenomenon.

• 대한기계학회논문집
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• 제14권1호
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• pp.112-118
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• 1990

본 연구에서는 ASTM-E24.01.06에서 제안하고 있는 실험방법을 응용하여 균열 정지 파괴인성값을 측정하였다.즉 쐐기와 분리형 부싱(wedge and split bushing)으 로 압축하중을 가함으로 균열선 웨지하중 시편[crack line wedge loaded specimen(CL- WL시편)]에 인장력을 발생시켜서 균열정지 응력확대계수( $K_{1a}$)를 결정하였다. 그리고 균열개시 응력확대계수가 균열정지 응력확대계수에 미치는 영향들을 여러가지 재료들에 대하여 체계적으로 검토하였다.다.

• 한국재료학회지
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• 제24권10호
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• pp.526-531
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• 2014

Thermal shock resistance property has recently been considered to be one of the most important basic properties, in the same way that the transverse-rupture property is important for sintered hard materials such as ceramics, cemented carbides, and cermets. Attempts were made to evaluate the thermal shock resistance property of 10 vol% TaC added Ti(C,N)-Ni cermets using the infrared radiation heating method. The method uses a thin circular disk that is heated by infrared rays in the central area with a constant heat flux. The technique makes it possible to evaluate the thermal shock strength (Tss) and thermal shock fracture toughness (Tsf) directly from the electric powder charge and the time of fracture, despite the fact that Tss and Tsf consist of the thermal properties of the material tested. Tsf can be measured for a specimen with an edge notch, while Tss cannot be measured for specimens without such a notch. It was thought, however, that Tsf might depend on the radius of curvature of the edge notch. Using the Tsf data, Tss was calculated using a consideration of the stress concentration. The thermal shock resistance property of 10 vol% TaC added Ti(C,N)-Ni cermet increased with increases in the content of nitrogen and Ni. As a result, it was considered that Tss could be applied to an evaluation of the thermal shock resistance of cermets.

• 대한치과보철학회지
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• 제40권1호
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• pp.68-78
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• 2002

The post core system has been used for reconstructon of severely damaged crown by caries or trauma. But problems such as crown exfoliation, post core fracture and root fracture have been reported. Ideal mechanical properies of the post require high fracture strength, high elastic limit and high resistance against fatigue and corrosion Modulus of elasticity of the post should be similar with that of dentine. Low hardness is also required for the convenience of post removal in failure. Furthermore, the post itself must be translucent for the esthetical purpose. Several types of the post have been developed to satisfy the criteria above mentioned. The purpose of this study was to find out the mechanical properties of quartz fiber post by comparing with those of gold post and zirconia post. The results of this study were as follows : 1. Maximal fracture strength and stiffness of quartz fiber post were similar with those of gold post and zirconia post. 2. Young's modulus and hardness of quartz fiber post were lower than those of gold post and zirconia post. Mechanical property of quartz fiber post against post fracture was similar with that of gold post and zirconia post. Mechanical property of quartz fiber post against root fracture was higher than that of gold post and zirconia post. Quartz fiber post could be removed easily due to low hardness.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1324-1327
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• 2003

The compressed fracture of spine caused by osteoporosis is one of the most frequent diseases in bone fracture. Recently the vertebroplasty has drawn much attention as a medical treatment for the compressed fracture of spine, which strengthens the vertebral body and corrects deformity, and relieves pain in patients by injecting bone cement. The finite element analysis is used to investigate the vertebroplasty quantitatively. Previous works with finite element analysis have drawbacks in their simplified models geometry of vertebral body and with material properties of bone. In this paper the exact geometry of vertebral body has been constructed from medical image data and the biomechanical property changes of vertebral body in vertebroplasty have been investigate by using three dimensional finite element analysis.

• 대한금속재료학회지
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• 제48권8호
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• pp.775-779
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• 2010

Functionally graded materials (FGM) of PSZ/NiCrAlY on Inconel substrate were fabricated by detonation gun spraying method. A thick ceramic layer generally has a high thermal barrier effect however, because failure often occurs, the use of an FGM layer gives an advantage in thermal property. During the thermal shock test, micro fracture processes were detected by the AE method. Also, the thermal shock test was performed for NFGM, FGM and the changed FGM in the layered composition profile. It was found through AE testing and the observation of fracture surface that FGM was superior to NFGM in thermal shock properties. The linear or metal-rich type FGM in composition profile had the best resisting property among the FGM. It was found that the controlled composition profile of the graded layers had better thermal properties.