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이억섭,김선용,홍성경,Lee, O.S.,Kim, S.Y.,Hong, S.K. 한국정밀공학회 1995 한국정밀공학회지 Vol.12 No.12
This investigation evaluates dynamic fracture characteristics of two alloy steels (STD-11 and STS-3) and a gray cast iron (GC-30). The dynamic fracture toughness of crack initiation and some of the dynamic fracturing characteristics were evaluated by using the instrumented Charpy impact testing procedures. It was found from experimental results for three kinds of materials that inertia force is directly proportional to impact velocity. The duration time of inertia force was found to be constant regardless of impact velocities in steel specimens.
이종재료의 접합면에 존재하는 균열선단의 응력장에 미치는 접합두께의 영향
이억섭(O.S.Lee),강희수(H.S.Kang) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.5_2
The effects of interface thickness on the stress field around the interface crack under dynamic loading are investigated using a finite element code(DYNA2D). It is found that the thinner thicknesses of an interface affect the stress field significantly. The maximum shear stress contour drawn in this study can be utilized in modeling analysis with aid of experimental counterpart.<br/>
[論文] Caustics방법에 의한 Polycarbonate의 J-적분값 결정에 관한 기초적 연구
이억섭(O. S. Lee),박기용(K. Y. Park) 한국자동차공학회 1990 오토저널 Vol.12 No.1
This study investigated a method for the determination of the J-integral for a tough glassy polymer such as polycarbonate plates by using the method of caustics. Comparing the values of J-integral determined by a numerical analysis and by the method of caustics, the method of caustics was found to be an effective experimental technique for the determination of the J-integral.<br/> The ratio between two J-integrals determined by the method of caustics and by finite element method converged into 1 within the limit oflow load. However, it was noticed that the greater the plastic zone at the crack tip was, the lower the J-integral obtained by the reflect method of caustics. This difference may be deduced from the damage at the crack tip such as craze appeared in the polycarbonate plate.<br/> It was confirmed that the ratio of Iongitudinal diameter(D_L) to transverse diameter (Dt) of caustics generally converged into 1 at the low load. The transition of the state of stress at the vicinity of a crack tip from plane strain to plane stress was deduced by noticing that the longitudinal diameter(D_I) grew faster than the transverse diameter(Dt) of caustics within the higher load range.