• 항공우주시스템공학회지
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• 제4권1호
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• pp.23-26
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• 2010

In this study, it was performed damage assesment of small scale composite aircraft developing. This aircraft adopted the sandwich structure to skin of wing. This study aims to investigate the residual strength of sandwich composites with Nomex honeycomb core and carbon fiber face sheets after the open hole damage by the experimental investigation. The 4-point bending tests were used to find the bending strength, and the open hole was applied to introduce the simulated damage on the specimen. The bending strength test results after open hole was compared with the results of no damaged specimen test. The FEM analysis is assessed via an experimental 4-point bending test.

• Journal of Welding and Joining
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• 제24권3호
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• pp.55-59
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• 2006

This paper is concerned with a study on cyclic bending load of bus folding door pillar including adhesive bonding and spot welding. Three specimen types were used such as spot welding, I-type adhesive bonding and M-type adhesive bonding in this study. The tensile-shear tests were carried out to evaluate the tensile-shear strength of these three specimen types. Also four-point bending tests were carried out to evaluate the static and dynamic bending load. From the results, using adhesive bonding has a better effect on the static and dynamic bending load than using spot welding. Therefore, manufacturing better structural products can be expected by applying hybrid welding using adhesive and spot welding to those.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.199-204
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• 2001

Big accidents of flyings, vessel, subways, gas equipments, buildings and bridge happens frenquently. Therefore many people are suffering harm of property. The destruction cause of macaine components is almost accused by fatigue. This study is test for STS304 specimen using pure and cantilever bending state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed.

• 대한기계학회논문집A
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• 제20권6호
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• pp.1836-1842
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• 1996

In this paper, static and fatigue bending strengths of CFRP(carbon fiber reinforced plastic laminates having impact damage(FOD) are evaluated. Composite laminates used for this experiment are CF/EPOXY and CF/PEEK orthotropy laminated plates, which have two-interfaces[${0^0}_4{90^0}_4}$]$_sym$. A steel ball launched by the air gun colides against CFRP laminates to generate impact damages. The damage growth during bending fatigue test is observed by the scanning acoustic microscope(SAM). When the impacted side is compressed, the residual fatigue bending strength of CF/PEEK specimen P is greater that that of CF/EPOXY SPECIMEN B. On the other hand, when the impacted side is in tension, the residual fatigue bending strength of CF/PEEK speicemen P is smaller than that of CF/EPOXY specimen B. In the case of impacted-side compression, fracture is proposed from the transverse crack generated near impact point. On the other hand, fracture is developed toward the impact point from the edge of interface-b delamination in the case of impacted-side tension.

• 한국구조물진단유지관리공학회 논문집
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• 제5권4호
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• pp.131-138
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• 2001

In inverted T-shape composite beam examine the structural behavior by experiment According to arrangement, type of stud connector, type of shear connector, reinforcement by welding of stirrup and a close analysis we came to these conclusion. 1) The compare result of bending strength according to arrange type of stud connector : A1-W(stud connector located web)specimen is exceed than A1-F(stud connector located flange). 2) B1-N(using prominence and depression of the web by shear connector) specimen is decrease than A1-W(using stud bolt by shear connector)specimen in bending strength and B2-N(reinforced by welding the stirrup to lower flange)specimen is similar with A2-W specimen. 3) According to reinforced by welding the stirrup to flange, the stiffness and bending strength of the beams are increase. A-scries stirrup comparatively low effective in the increase of strength by welding the stirrup to flange because enough composite effect show by stud connector, but B-series stirrup is comparatively high effective in shear connector effect because shortage of prominence and depression of the web.

• 대한기계학회논문집A
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• 제31권11호
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• pp.1108-1114
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• 2007

The low kinds of $Al_2O_3$ composite ceramics were prepared using a mixture of 85 wt.% $Al_2O_3$ (mean size $0.5\;{\mu}m$), 15 wt.% SiC Powder with $Y_2O_3$, as an additive powder (0, 1, 3 and 5 wt.%). The crack-healing strengths were studied as functions of crack-healing temperature and amount of $Y_2O_3$. The in-situ crack-healing behavior was observed at 1,573 K for 1 h in the air. The heat treated specimen with 3 wt.% of $Y_2O_3$ showed better crack-healing ability than specimen with 1 or 5 wt.% of $Y_2O_3$. In case of specimen with 3 wt.% of $Y_2O_3$, the bending strength of the crack-healed specimen at 1,473 K was recovered to the bending strength of smooth specimen treated at 1573 K. The heat-resistance limit temperature of $Al_2O_3$ composite ceramics was 1,073 K, 1,373 K, 873 K for the specimen with 1, 3, 5 wt.% of $Y_2O_3$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.49-55
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• 2008

Strip bending test has been frequently utilized to measure the mechanical properties of freestanding thin films in substitute for the micro-tensile test. However, in spite of its simplicity and reliability, strip bending test has a few problems, for example, the measurement of strain and the calculation of stress at zero strain. In this study, these problems are precisely reviewed and proved. Upon this review, strip bending tester has been developed, which uses the confocal laser displacement meter to measure the deformed configuration of the specimen and the possibility and limitation of this testing system is carefully investigated including the estimation of uncertainty of the measurement of strain. Finally, to prevent errors and to improve the accuracy of this testing system, the shape of the specimen has been carefully studied and is proposed.

• 한국해양공학회지
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• 제15권2호
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• pp.124-129
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• 2001

The research on anticorrosive of valve for ship, waterworks, and drainage system is very important. The purpose of this paper is to develop the metal/polyurethan adhesive technique at insider of the value to prevent corrosion in the value. It is performed to the bending strength test by using metal /polyurethan in the metals (SB41, Al6061). It is investigated to the effects of bending strength on curing temperature, preheating time and curing time, and to the fracture mechanism of metal/polyurethan adhensived specimen. As a results, we find that the bending strength is the highest at curing temperature of 11$0^{\circ}C$ and the curing time is 60 minutes in metal/polyurethan adhesive specimen.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 춘계학술대회 논문집
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• pp.399-403
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• 2002

The transmission system of high speed train serve in the severe condition compared with those of other trains, namely, they have to transmit high power to run with high speed and they have to make maximum use of the limited space. To clarify the strength of gear for Korea High-Speed Train, a bending fatigue test of gear specimen is performed and compare with actual gear's. From this result, specimen test is useful to infer S-N curve and endurance limit of actual gear that much time and expense are consumed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.345-350
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• 2001

In order to perform elastic-plastic fracture mechanical analyses, fracture resistance curves for concerned materials are required. 1T-CT specimen was used to obtain fracture resistance curves. But the fracture resistance curve by the 1T-CT specimen was very conservative to evaluate the integrity of the structure. And fracture resistance curve was affected by the specimen geometry and crack plane orientation. The objective of this paper is to be certain the conservativeness of the fracture resistance curve by the 1T-CT specimen and to provide the additional safety margin. For these, the fracture tests using the real pipe specimen and standard 1T-CT specimen test were performed. 4-point bending jig was manufactured for pipe test and direct current potential drop method was used to measure the crack extension and length for pipe test. From the pipe and the 1T-CT specimen test results, it was observed that the J-integral of the 1T-CT specimen test at the crack initiation point was very small compare to that of the pipe specimen test.