연구원 활동 : 연구실별 연구현황 ; < 기계공학분야 > 피로 및 파괴역학연구실

송삼홍 고려대학교 공학기술연구소 1994 공학기술연구소보 Vol.1 No.-

平面應力 破壞靭性値 擧動에 관한 硏究

송삼홍,고성위,정규동 대한기계학회 1987 대한기계학회논문집 Vol.11 No.3

본 연구에서는 평면응력 파괴인성치의 거동에 관한 일련의 연구로서 위와 같 은 점을 고려하여 얇은 두께의 시험편을 이용하여 z의 변화에 대한 평면응력 파괴인성 치와 J저항곡선을 실험적으로 고찰하였으며 크랙성장을 고려한 J적분식도 검토하였다. 크랙길이는 하중제거 컴플라이언스법에 의하여 구하였고, ASTM E813의 방법으로J= .sigma.$_{f}$ .DELTA.(2a)인 크랙둔화선과 J저항곡선의 교점에서 구한 J적분값을 J$_{c}$로 정 의하였다. 또한, 재료를 변형경화재료로 가정하여 HRR응력변형율장의 특성을 이용 하여 J적분값을 구한 후 실험치와 상호 비교 검토하였다.이때 입력자료는 실험치의 그것과 동일하게 하였다. 동시에 z의 변화에 대한 T의 변화도 함께 고찰하였다.다. In this study, the plane stress fracture toughness and Tearing modulus are investigated for various crack ratios using the J integral. To evaluate the J integral and Tearing modulus, both experiments and estimation are used. The thickness of the low carbon steel specimens that is used in the experiments is 3mm. The type of specimen that is considered in the study is center-cracked-tension one. The measurements of crack length are performed by unloading compliance method. In the estimation of crack parameters such as the J integral and load line displacement, the Ramberg and Osgood stress strain law is assumed. Then simple formulas are given for estimating the crack parameters from contained yielding to fully plastic solutions. Obtained results are as follows; (1) When the crack ratio is in the range of 0.500 - 0.701, the plane stress fracture toughness is almost constant regardless of crack ratios. (2) The fracture toughness (J$\_$c/) and Tearing modulus (T) obtained are J$\_$c/=28.51kgf/mm, T=677.7 for base metal, J$\_$c/=31.85kgf/mm, T=742.0 for annealed metal. (3) Simpson""""s and McCabe""""s formulas which consider crack growth in estimating J integral are shown more conservative J and lower T than Rice""""s and Sumpter""""s. (4) Comparison of the prediction with the actual experimental measurements by Simpson""""s formula shows good agreement.

복합조직의 파괴거동과 파괴혁성에 관한 연구 I

송삼홍,김규생 대한기계학회 1981 대한기계학회논문집 Vol.5 No.2

In order to study on the fracture behavior and the fracture thoughness of combined structure, the specimens, structural steel (SM28C) and 6:4 brass are annealed for ductility and investigated for the befavior of fracture and the absorbed energy at the variation of the impact velocity. The results obtained by this study are as follows: (1)The maximum load increases with the impact velocity, but in the condition of constant impact velocity it decreases as the ductility increases. (2)The absorbed energy increases with the impact velocity, but in the condition of constant impact velocity it is constant as the ductility increases. (3)In the case of the combined structure of peralite and ferrite, the microcracks initiates and propagates mainly in the ferrite structure intergranular in accompany with the slip, and the slip concentration phenomena occur in the boundary of pearlite structure However, in case of the combined structure of .alpha. and ..betha. phase, the microcracks initiates and propagares mainly in the .alpha. phase intergranularly, and slip concentration phenomena not ocur in the boundary of .betha. phase.

과대, 과소응력하에서의 피로크랙발생 전파거동(I)

송삼홍,원시태 대한기계학회 1985 대한기계학회논문집 Vol.9 No.3

본 논문에서는 불규칙 하중을 받는 부재에 대한 연구의 고초로서 간단한 응력 모델을 설정하고 이들 변동응력이 가해지는 시기를 명확히 구분하여 크랙전파곡선의 거동을 고찰하였다. 특히 부하되는 응력 진폭의 크기에 따라서 크랙선단부의 미시적 인 변화의 크기가 다르고 이로인하여 크랙전파에 대한 피해의 정도가 달라진다고 하면 크랙전파의 지연 및 가속현상이 나타날 것이 예측이 되고 따라서 이때 나타나는 피해 정도의 크기를 미소 경도치로 환산하여 그것과 피로크랙 전파 특성과를 비교 검토 하 였다.

반복-굽힘 모멘트의 진폭에 따른 A15052/AFRP 적층재의 층간분리 영역과 피로균열진전 거동

송삼홍,김철웅,Song, Sam-Hong,Kim, Cheol-Ung 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.8

Aluminum 5052/Aramid Fiber Reinforced Plastic(Al5052/AFRP) laminates are applied to the fuselage-wing intersection. The Al5052/AFRP laminates suffer from the cyclic bending moment of variable amplitude during the service. Therefore, the influence of cyclic bending moment on the delamination and the fatigue crack propagation behavior in Al5052/AFRP laminate was investigated in this study. Al5052/AFRP laminate composite consists of three thin sheets of Al5052 and two layers of unidirectional aramid fibers. The cyclic bending moment fatigue tests were performed with five different levels of bending moment. The shape and size of the delamination zone formed along the fatigue crack between Al5052 sheet and aramid fiber-adhesive layer were measured by an ultrasonic C-scan. The relationships between da/dN and ΔK, between the cyclic bending moment and the delamination zone size, and between the fiber bridging mechanism and the delamination zone were studied. Fiber failures were not observed in the delamination zone in this study. It represents that the fiber bridging modification factor should turn out to increase and that the fatigue crack growth rate should decrease. The shape of delamination zone turns out to be semi-elliptic with the contour decreased non-linearly toward the crack tip.

두개의 미소원공결함에서의 피로크랙발생과 전파에 관한 연구

송삼홍,배준수,Song, Sam-Hong,Bae, Joon-Soo 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.5

The aim of this study is an investigation of the interaction of two micro hole defects affecting fatigue crack initation life and propagation behavior. The locatio of two micro hole defects was considered as an angle of alignment and the distance between the centers of two micro hole defects. The fatigue cracking behavior is experimented under bending. When micro defects are located close to each other, the fatigue crack initiation lives are varied with their relative locations. In the experiments, the area of local plastic strain strongly played a role in the fatigue crack initiation lives. Therefore we introduce a parameter which contains the plastic deformation area at stress concentrations and propose a fatigue crack initiation life prediction curve. In addition, the directions and propagation rates of fatigue cracks initiated at two micro hole defects are studied experimentally.

터빈용 Cr-Mo-V강의 고온 환경변화에 따른 피로거동에 관한 연구

송삼홍,강명수,Song, Sam-Hong,Kang, Myung-Soo 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.1

The high temperature fatigue tests were performed using the specimens taken from Cr-Mo-V steel, widely used as thermal power plant turbine materials for examination fatigue behavior of materials in power plants which have been operated for long periods. The fatigue tests at high temperature were performed at the various temperature and applied stress. The results obtained are summarized as follows : The fatigue crack length increases and the fatigue life decreases with temperature and applied stress according to the same number of stress cycle. The fatigue crack propagation and the fatigue life were much influenced by temperature and applied stress.

Al/APRP 적층재의 수지혼합비가 인장 및 티-필(T-peel) 강도 특성에 미치는 영향

송삼홍,김철웅,Song, Sam-Hong,Kim, Cheol-Woong 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.11

Aluminum alloy/aramid fiber reinforced plastic(Al/AFRP) laminates consists of high strength metal(A15052) and laminated aramid fiber with structural adhesive bond. The mixture ratio effect of epoxy resin curing agent accelerator on the tensile strength and T-peel strength characteristic in Al AFRP laminates were investigated in this study. The epoxy. diglycidylether of bisphenol A(DCEBA), It'as cured by methylene dianiline(MDA) with or without an accelerator(K-54). Eight different kinds of resin mixture ratios were selected for the test , five kinds of Al/AFRP laminates were named as Al/AFRP(1) and three others of Al/AFRP laminates were named as Al/AFRP(2). The comparison of tensile strength and T-peel strength with variation of resin mixture ratio were studied. Respectively. Al/AFRP(1) and Al/AFRP(2) indicated approximately 6.0 times and 7.0 times more improved maximum tensile strength in comparison with those of monolithic A15052. Al/AFRP(2) indicated approximately 1.5 times more impoved maximum T-peel strengths in comparison with those of Al/AFRP(1). As results. Al/AFRP(2) turned out to have more effective characteristics on the tensile strength and T-peel strength than those of Al/AFRP(1).

構造材料의 破壞 및 機能과 設計 VI 구조설계의 개요

송삼홍 대한기계학회 1980 大韓機械學會誌 Vol.20 No.1

구조물 재료의 파양의 거동과 강도 (VI) (부식파열에 대하여)

송삼홍 대한기계학회 1977 大韓機械學會誌 Vol.17 No.3

과학기술의 비약적인 발전에 따라서, 우주개발, 해양개발등을 실현시키는 단계에 이르렀고, 또한 이에 발맞추어 기계 및 구조물에 사용되는 각종부재의 경량화를 꾀하는 한편 사용장소가 매우 험악해지고 있다. 이와같은 사회적인 추세에 따라 재료가 보다 협악한 조건화에서 사용된다는 사 실은 최근에는 일만상식처럼되고 있다 따라서 험악한 장소에서 파괴가 발생한다면 최악이 경우는 인명을 위협하기도 한다. 이와같은 일반사항을 고려하여 본강좌(4) 에서는 특히 부식되기쉬운 장 소에서 부재가 사용되었을 때의 부식피로에 대하여, 극히 일반적인 사항을 간추려보기로 하겠다.