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셀프 피어싱 리베팅한 Al-5052 접합부의 피로강도 평가
강세형 ( Se Hyung Kang ),황재현 ( Jae Hyun Hwang ),김호경 ( Ho Kyung Kim ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.3
Self-piercing riveting (SPR) is receiving more recognition as a possible and effective solution for joining automotive body panels and structures, particularly for aluminum parts and dissimilar parts. In this study, static strength and fatigue tests were conducted using coach-peel and cross-tension specimens with Al-5052 plates for evaluation of fatigue strength of the SPR joints. For the static experiment results, the fracture modes are classified into pull-out fracture due to influence of plastic deformation of joining area. During the fatigue tests for the coach-peel and cross-tension specimens with Al-5052, interface failure mode occurred on the top substrate close to the rivet head in the most cycle region. There were relationship between applied load amplitude pamp and life time of cycle N, P(amp)=715xN(-0.166) and P(amp)=1967.3xN(-0.162) were for the coach-peel and cross- tension specimens, respectively. The finite element analysis results for specimens were adopted for the parameters of fatigue lifetime prediction. The relation between SWT fatigue parameter and number of cycles was found to be SWT=192.8N(f)(-0.44).
이종재료 Self-Piercing Rivets 접합부의 인장-전단 피로강도
강세형 ( Se Hyung Kang ),김택영 ( Taek Young Kim ),오만진 ( Man Jin Oh ),김호경 ( Ho Kyung Kim ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.4
Self-piercing riveting (SPR) process is gaining popularity due to its many advantages. The SPR does not require a pre-drilled hole and has capability to join a wide range of similar or dissimilar materials and combinations of materials. This study investigated the fatigue strength of self-piercing rivet joint with aluminum alloy (Al-5052) and steel (SPCC) sheets. Static and fatigue tests on tensile-shear specimens were conducted. From the static strength aspect, the optimal punching force for the specimen with upper SPCC (U.S) sheet and lower aluminum alloy(L.A) sheets was 34 kN. During static test the specimens fractured in pull-out fracture mode due to influence of plastic deformation of joining area. There was a relationship between applied load amplitude P_{ amp} and number of cycles N; P _{amp} =19588N pile{-0.211#f} and P _{amp} =4885N pile{-0.083#f} for U.S-L.A and U.A-L.S specimens, respectively. U.A-L.S fatigue specimens failed due to fretting crack initiation around the rivet neck between upper and lower sheets.
온도변화에 따른 주석 도금한 전기 커넥터의 미동마멸 부식 거동
오만진(Man-Jin Oh),강세형(Se-Hyung Kang),이만석(Man-Suk Lee),김호경(Ho-Kyung Kim) 한국트라이볼로지학회 2014 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.30 No.3
In this study, we conduct fretting corrosion tests on tin-plated brass coupons to investigate the effect of temperature on fretting corrosion for various span amplitudes. We prepare a coupled fretting corrosion specimens using a tin-plated brass coupon with a thickness of 10 μm. One specimen is a flat coupon and the other specimen is a coupon with a protuberance in 1 mm radius, which is produced using 2 mm diameter steel ball. We conduct fretting corrosion tests at 25℃, 50℃, 75℃, 100℃ by rubbing the coupled coupons together at the contact between the flat and protuberance coupons. We measure electric resistance of the contact during the fretting corrosion test period. There is increase in resistance with fretting cycles. It is found that rate of increase in electric resistance becomes faster with increase in testing temperature. Magnitude of friction coefficient increases with fretting span amplitudes. And, change in friction coefficient becomes desensitized to the increment in span amplitude. Assuming that failure cycle is the cycle with an electric resistance of 0.01 Ω, we find that failure lifetime (Nf) decreases with increase in testing temperature. Furthermore, based on the assumption that the damage rate of the connector is inversely related to the failure cycle, we calculate the activation energy for fretting damage to be 13.6 kJ/mole by using the Arrhenius equation. We propose a method to predict failure cycle at different temperatures for span amplitudes below 30 μm. Friction coefficients generally increase with increase in span amplitude and decrease in testing temperature.
혼합모드상태에서의 Al 5052-H32 셀프 피어싱 리벳 접합부의 피로강도 평가
곽진구 ( Jin Gu Kwak ),강세형 ( Se Hyung Kang ),김호경 ( Ho Kyung Kim ) 한국안전학회(구 한국산업안전학회) 2016 한국안전학회지 Vol.31 No.3
In this study, static and fatigue tests on the self-piercing riveted (SPR) joint were conducted using cross-shaped specimens with aluminum alloy (Al-5052) sheets. Mixed mode loading was achieved by changing the loading angles of 0, 45, and 90 degrees using a special fixture to evaluate the static and fatigue strengths of the SPR joints under mixed mode loading conditions. Simulations of the specimens at three loading angles were carried out using the finite element code ABAQUS. The fatigue specimens failed in an interfacial mode where a crack initiated at the upper sheet and propagated along the longitudinal direction and finally fractured Maximum principal stress, von-Mises effective stress failed to correlate the fatigue lifetimes at three loading angles. However, the equivalent stress intensity factor was found to be appropriate to correlate the fatigue lifetimes at three loading angles.