• Journal of Welding and Joining
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• v.12 no.4
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• pp.141-150
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• 1994

The residual stress is inevitably introduced into composites because of the mismatch of the coefficient of thermal expansion, and it is different in each phase. The X-ray technique can detect separately the stress in each phase, so will wield useful information for analyzing the toughening mechanisms of composites. In order to apply the law of mixture to alloy steels with composite microstructures, two phase stainless steel, consisted of ferrite (.alpha.-Fe) and austenite (.gamma.-Fe) structures, was selected. The tensile elastic deformation was loaded, and then the X-ray diffraction technique was used to measure the X-ray elastic constants, the X-ray stress constants and the phase stresses. The law of mixture was investigated and the separation of macrostress and microstress was carried out. The phase stresses (the residual stresses of phase) in each phase, which were measured by X-ray technique, was directly proportional to the applied stress. The macrostress calculated from the phase stresses by using the law of mixture was nearly equal to the applied stress.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.2
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• pp.23-29
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• 2007

Fracture behavior of brittle solids such as rocks, ceramics and concrete is closely related to microcracking. A meso-scale analysis method using the natural element method is proposed for the analysis of material damage of brittle microcracking solids. The microcracking is assumed to occur along Voronoi edges in the Voronoi diagram generated using the nodal points as the generators. The mechanical effect of microcracks is considered by controlling the material constants in the neighborhood of the microcracks. The proposed meso analysis method is applied to the simulation of the microcracking behaviors of brittle solids subjected to uniaxial and biaxial macrostress. The obtained results are in good agreement with the results by computational damage mechanics model. The validity of the proposed method has been demonstrated by these numerical examples.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.724-730
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• 2006

Fracture behavior of brittle solids is closely related to microcracking. A meso-scale analysis method using the natural element method is proposed for the analysis of brittle microcracking solids. The microcracking is assumed to occur along Voronoi edges in the Voronoi diagram generated using the nodal points as the generators. The mechanical effect of microcracks is considered by controlling the material constants in the neighborhood of the microcracks. The meso-analysis method is applied to the simulation of the microcracking behaviors of brittle solids subjected to tensile macrostress. The method is also applied to the analysis of the propagation of a macrocrack accompanied by the coalescence with microcracks formed near the macrocrack-tip.

• Journal of Ocean Engineering and Technology
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• v.8 no.2
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• pp.105-114
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• 1994

초경합금은 기계적 성질이 다른 WC의 분상상과 Co의 결합상으로 구성되어 있다. 만일 이합금이 거시적으로 균일하게 변형을 하면, 각 상들은 이들의 응력상태에 따라 다르게 변형될 것이다. 따라서 WC-Co 합금의 변형특성과 강화기구를 명확히 알기 위해서는 각상의 미시적 변형과 파괴기구를 검토할 필요가 있다. 본 연구에서는 시편에 굽힘하중을 가하여, X선 회절로 분산상인 WC상 및 결합상인 Co상의 X선적 탄성정수와 응력정수를 측정하였다. WC-Co합금중의 WC상과 Co상의 상응력은 WC(112)면과 CO(311)면의 회절로서 결정하였다. 그리고 이 상응력들을 복합법칙의 적용가능성에 대하여 검토하였다.