• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.704-708
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• 1996

The elastic dynamic crack curving could be obtained by controlling the loading rate, the initial crack-tip blunting to store much energy before crack initiation and the magnitude of reflected wave from finite boundaries. However there is no theoretical and experimental elastic-plastic dynamic curving study. This paper proposes a specimen geometryfor a study of dynamic elastic-plastic crack curving and presents a preliminary result. The specimen has a blunt physical crack tip on a side, and a round notch tip on the other side. From the experiment using this specimen, it is found that the narrow plastic zone ahead of the round notch tip produces the change of load direction and anti-symmetricity of the dynamic isochromatics, and each result causes the crack curving phenomenon. After a certain time, as the elastic-plastic crack gets close to the round notch tip near, the degree of the crack curving get larger. The elastic reack curving propagates more sensitively to the surround of crack tip than the plastic crack curving does. The cynamic elastic-plastic crack curving is found to be proportional to the CTOA(the crack tip opening angle). The dynamic elastic-plastic crack may propagate in the direction perpendicular to the loading. An apparant strip yield zone which is similar to the Dugdale strip yield zone is noted ahead of the physical crack tip.

• 대한기계학회논문집A
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• 제24권11호
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• pp.2823-2827
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• 2000

The dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system is utilized to record the dynamically propagating behavior of an interface crack. This paper investigates determined the effects of the hole (exited on the path of the crack propagation) on the crack propagation behavior by comparing the experiment isochromatic fringes to the theoretical stress fields.

• 대한조선학회논문집
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• 제35권4호
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• pp.46-54
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• 1998

노치의 기하학적 형상이 동적응력집중계수에 미치는 영향을 동적 광탄성 시험법을 이용하여 규명하였다. 동적 하중 장치로부터 발생하는 탄성파에 의하여 여러 종류의 노치의 기하학적 형상 주위에서 발생하는 동적응력장을 $10^6/sec$의 촬영 속도를 갖는 Cranz-Shardin형 카메라를 사용하여 12장면을 기록하였다. 다양한 노치 선단의 형상에 대한 동적응력특이지수를 간단한 모델링식으로 결정하는 방안을 제시하고, 여러 가지 노치의 기하학적 형상에 대응하여 발생하는 동적응력집중현상을 비교하는데 이용하였다. 동적 광탄성 시험법으로 얻어진 동적응력장을 면밀히 해석하여, 동적응력집중계수가 노치의 형상에 크게 의존함을 규명하였다.

• 대한기계학회논문집A
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• 제20권7호
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• pp.2097-2107
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• 1996

The dynamic photoelastic technique had been utilized to investigate the possibillity of relieving the large local singular stresses induced at the corner of a right- angle- indenter. The indenter compressed a semi-infinite body dynamically with an impact load applied on the top of the indenter. The effects of the geometric changes of the indenter in terms of the diameter (d) and the location (1) of the stress relieving notch on the behavior of the dynamic contact stresses were investigated. The influence of stress relieving notches positioned along the edge of the semi-infinite body on the dynamic contact stresses were also studied by changing the diameter (D) and the location (L) of the notch. A multi-speak-high speed camera with twelve sparks were used to take photographs of full field dynamic isochromatic fringe patterns. The contact singular stresses were found to be released significantly by the stress relief notches both along the indenter and the edge of the semi-infinite body. The optimal position and geometry of the stress relieving notches were obtained with the aid of limited experimental results.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.238-246
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• 1996

When the important structures or components of agricultural machinery are designed, the full-filed methods of stress analysis can provide enough information in order to obtain lighter weight and prevent failure. The photoelasticity has been applicated to solve many practical engineering problems. The coating method provides full-field information, enabling the engineers to determine the complete distribution of surface strains and directly highlighting severely strained areas, especially for the welded frames of agricultural machinery. A combined method of model and prototype for strain analysis of excavator has been successfully applied to improve design. A measuring and recording system controlled by micro-computer and application software for dynamic event was studied. It can be widely used in structural failure analysis under cyclical loading . Typical application concerned stress field of crack tip and failure analysis of some mechanical structures are introduced are in roduced briefly in this paper.