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).

응력비 변화에 따른 혼합모드 피로균열 전파거동

송삼홍,최지훈,이정무,Song, Sam-Hong,Choi, Ji-Hoon,Lee, Jeong-Moo 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.11

Most cracks in the structure occur under mixed mode loading and those fatigue crack propagation behavior heavily depends on the stress ratio. So, it is necessary to study the fatigue behavior under mixed mode loading as the stress ratio changes. In this paper, the fatigue crack propagation behavior was respectively investigated at stress ratio 0.1, 0.3, 0.5, 0.7 and we changed the loading application angle into 0$^{\circ}$, 30$^{\circ}$, 60$^{\circ}$ to apply various loading mode. The mode I and II stress intensity factor of CTS specimen used in this study was calculated by the displacement extrapolation method using FEM (ABAQUS). Using both the experiment and FEM analysis, we have concluded the relationship between crack propagation rate and stress intensity factor range at each loading mode due to the variation of stress ratio. Also, when the crack propagated under given stress ratio and loading mode condition, we have concluded the dominant factors of the crack propagation rate at each case.

소컷 및 원공 주위의 피로균열 형태변화와 층간분리거동 (I) - 아라미드섬유 강화 금속적층재의 경우 -

송삼홍,김철웅,Song, Sam-Hong,Kim, Cheol-Woong 대한기계학회 2003 大韓機械學會論文集A Vol.27 No.1

The aramid fiber reinforced metal laminates(AFRMLs) used for the wing part fair flight suffer the cyclic bending moment of variable amplitude during service. The fatigue crack propagation and delamination behavior in AFRMLs containing a saw-cut and circular hole was investigated using the average stress criterion(ASC) model. Mechanical tests were carried out using the cyclic bending moment of 4.9 N . m and delamination was observed by ultrasonic C-scan images. In case of AFRMLs containing a saw-cut fatigue crack propagated in aluminum matrix, inducing delamination. However, in case of AFRMLs containing a circular hole, delamination formed with two types under cyclic bending moment of 4.9 N . m. First, delamination formed along the fatigue crack in aluminum matrix. Second, delamination formed without any fatigue crack around the circular hole. Therefore, delamination was formed depending on the stress distribution near the circular hole.

층간분리성장률(dA_D/da)과 섬유가교효과인자(F_BE)를 이용한 Al/GFRP 적층재의 피로거동 해석

송삼홍,김철웅,Song, Sam-Hong,Kim, Cheol-Woong 대한기계학회 2003 大韓機械學會論文集A Vol.27 No.2

The influence of cyclic bending moment on the delamination and the fatigue crack propagation behavior in Al/GFRP laminate such as the wing section was investigated. The main objective of this study was to evaluate the relationship between crack profile and delamination behavior. And a propose parameter on the delamination growth rate(d $A_{D}$/da) of Al/GFRP laminates with a saw-cut using relationship between delamination area( $A_{D}$) and cycles(N), crack length(a), stress intensity factor range($\Delta$K). Also, the fiber bridging effect factor( $F_{BE}$ ) was propose that the fiber bridging modification factor($\beta$$_{fb}$ ) to evaluate using the delamination growth rate(d $A_{D}$/da). The shape and size of the delamination zone formed along the fatigue crack between aluminum alloy sheet. Class fiber-adhesive layer were measured by an ultrasonic C-scan image. The shape of delamination zone turns out to be semi-elliptic with the contour decreased non-linearly toward the crack tip. It represents that relationship between crack length and delamination growth rate(d $A_{D}$/da) were interdependent by reciprocal action, therefore it's applicable present a model for the delamination growth rate(dA/sib D//da) in Al/GFRP laminates.minates.s.

모드 II 하중을 받는 CTS 시험편의 피로균열 전파거동에 관한 실험적 연구

송삼홍,이정무,Song, Sam-Hong,Lee, Jeong-Moo 대한기계학회 2003 大韓機械學會論文集A Vol.27 No.7

The purpose of this paper is to investigate fatigue crack behavior under shear(Mode II) loading. Various specimens and devices have been used in order to produce Mode II loading in fatigue experiments for shear crack propagation. But, there is not sufficient comparisons of experimental results between Mode II and others loading modes, because of characteristics of applied loads and specimens. So, compact tension shear(CTS) specimens were used in this paper to investigate the propagation behavior of Mode II by comparing the experimental results between loading modes. We firstly observed the characteristics which was showed in Mode II experiment using CTS specimens. The experimental results under Mode II loading were compared with fatigue crack behavior under Mode I and Mixed-mode I+II loading. The characteristics for initiation and propagation behavior under Mode II loading was investigated by such comparisons.

레이저간섭변위 게이지로 관찰한 용접재에서의 피로균열 열림거동과 피로균열 전파속도

송삼홍,김현,최진호,Song, Sam-Hong,Kim, Hyun,Choi, Jin-Ho 대한기계학회 1995 대한기계학회논문집 Vol.19 No.4

The constant .DELTA.K fatigue tests are performed in SS41 and its weldments to investigate crack opening behavior and fatigue crack propagation behavior at each parts of weldment and its boundary layer. The weldments were annealed after welding for the purpose of relieving residual stress. Every weldments has notch at weld metal zone, and fatigue crack propagates from weld metal zone to vase metal zone perpendicular to weld line. The Laser ISDG method is used in order to determine the crack opening ratio, this method is more precise than indirect measurement method, and faster and easier than other direct measurement method.

불규칙하게 분포된 미소결함 사이의 응력간섭 및 피로균열 거동에 대한 실험적 연구 (1)

송삼홍,배준수,최병호,Song, Sam-Hong,Bae, Jun-Su,Choe, Byeong-Ho 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.5

In this study, fatigue crack behavior between arbitrarily located defects was investigated by experiment. Especially, stress interaction between micro hole defects and fatigue cracking, and fatigue crack initiation life following the variation of location of micro hole defects were considered. In addition, crack initiation position by micro hole stress interaction and the relationship between stress concentration factor and fatigue initiation life are studied in detail.

두 크랙의 간섭형태에 따른 피로크랙전파거동의 변화

송삼홍,최병호,배준수,Song, Sam-Hong,Choe, Byeong-Ho,Bae, Jun-Su 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.7

Because of the existence of stress interaction field made by other defects and propagating cracks, the structure may be weakened. Therefore in this study, the crack behavior in the interaction field made by two different cracks is studied experimentally. In the experiment, vertical distance between two cracks and applied stress are varied to make different stress interacted field. In addition, the effect of plastic zone is used to examine crack propagation path and rate. Three types of crack propagation in the interacted field were found, and crack propagating path and rate of two cracks were significantly changed according to different applied stress as each crack propagates. And the results are attributed to the effect of the size and shape of the plastic zone.

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.

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.