• Macromolecular Research
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• 제10권1호
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• pp.24-33
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• 2002

Interfacial and microfailure properties of carbon fiber/epoxy composites were evaluated using both tensile fragmentation and compressive Broutman tests. A monomeric and two polymeric coupling agents were applied via the electrodeposition (ED) and the dipping applications. A monomeric and a polymeric coupling agent showed significant and comparable improvements in interfacial shear strength (IFSS) compared to the untreated case under both tensile and compressive tests. Typical microfailure modes including cone-shaped fiber break, matrix cracking, and partial interlayer failure were observed under tension, whereas the diagonal slipped failure at both ends of the fractured fiber appeared under compression. Adsorption and shear displacement mechanisms at the interface were described in terms of electrical attraction and primary and secondary bonding forces.

• 한국공작기계학회논문집
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• 제14권1호
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• pp.30-36
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• 2005

This study is to investigate a damage estimation of single edge notched tensile specimens as a function of acoustic emission(AE) according to the uni-directionally oriented carbon fiber/epoxy composites, CFRP In fiber reinforced composite materials, AE signals due to several types of failure mechanisms are typically observed. These are due to fiber breakage, fiber pull-out matrix cracking, delamination, and splitting or fiber bundle breaking. And these are usually discriminated on the basis of amplitude distribution, event counts, and energy related parameters. In this case, AE signals were analyzed and classified 3 regions by AE event counts, energy and amplitude for corresponding applied load. Bath-tub curve shows 3 distinct periods during the lifetime of a single-edge-notch(SEN) specimen. The characterization of AE generated from CFRP during SEN tensile test is becoming an useful tool f3r the prediction of damage failure or/and failure mode analysis.

• 대한금속재료학회지
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• 제48권8호
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• pp.717-723
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• 2010

The degradation behavior of fuel cladding is a very import concern in nuclear power generation, because the operation of nuclear plants can be limited by fuel cladding degradation. In order to evaluate the hydride effect on failure of zirconium fuel claddings, a ring tensile test for the circumferential direction was carried out at room temperature for claddings having different hydride characteristics such as density and orientation; microstructural evaluation was also performed for those claddings. The circumferential failure of the claddings was promoted by increasing the hydride concentration in the matrix; however, the failure of the claddings was affected by the hydride orientation rather than by the hydride concentration in the matrix. From fracture surface observation, the cladding failure during the ring tensile test was matched with the hydride orientation.

• Advances in concrete construction
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• 제7권4호
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• pp.241-247
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• 2019

In this paper the effect of bedding layer on the failure mechanism of rock in direct shear test has been investigated using particle flow code, PFC. For this purpose, firstly calibration of pfc2d was performed using Brazilian tensile strength. Secondly direct shear test consisting bedding layer was simulated numerically. Thickness of layers was 10 mm and rock bridge length was 10 mm, 40 mm and 60 mm. In each rock bridge length, bedding layer angles changes from $0^{\circ}$ to $90^{\circ}$ with increment of $15^{\circ}$. Totally 21 models were simulated and tested. The results show that two types of cracks develop within the model. Shear cracks and tensile cracks. Also failure pattern is affected by bridge length while shear strength is controlled by failure pattern. It's to be noted that bedding layer has not any effect on the failure pattern because the layer interface strength is too high.

• 한국공작기계학회논문집
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• 제12권1호
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• pp.58-64
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• 2003

A mechanical press joining was investigated in ender for joining A1-5052 sheets for automobile body weight reduction. Static tensile and fatigue tests were conducted using tensile-shear specimens for evaluation of fatigue strength of the joint. During Tox joining process for A1-5052 plates, using the current sheet thickness and punch diameter, the optimal applied punching force was found to be 32 kN under the current joining condition. For the static tensile-shear experiment results, the fracture mode is classified into interface fracture mode, in which the neck area fractured due to influence of neck thickness, and pull-out fracture mode due to influence of plastic deformation of the joining area. And, during fatigue tests for the A1-5052 tensile shear specimens, interface failure mode occurred in the region of low cycle. The fatigue endurance limit approached to 6 percents of the maximum applied load, considering fatigue lifetime of $2.5\times10^6$ cycles.

• 대한관절경학회지
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• 제2권1호
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• pp.85-92
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• 1998

Various methods for fixation of graft have been widely used for reconstruction of anterior cruciate ligament. However, the biomechanical strength of each fixation techniques are not fully understood. The purpose of this study is to compare the pull out strength of different fixation techniques which is probably the most important factor for the success at the initial stage of healing. Biomechanical test was carried out to measure and compare the pull out tensile strength of five different fixation techniques in 35 pig(Yorkshire) knees. ANOVA and Duncan multiple comparison test was applied for statistical analysis. In the two fixation techniques with bone patellar tendon bone graft, the mean maximum tensile strength was $1333.4{\pm}148.5N$ with titanium interference screw, while it was $1310.1{\pm}168.9N$ with biodegradable interference screw. The failure mode were pulled out of bone plugs from the femoral tunnel in majority cases. In the fixations with hamstring tendon, the mean maximum tensile strength were $1405.9{\pm}135.1N$ with SemiFix screw, $820.3{\pm}104.5N$ with biodegradable interference screw, and $682.1{\pm}54.2N$ with Endobutton. The mode of failure was variable in each technique. The tendon was pulled out from the tunnel in biodegradable interference screw fixation, the screw was bent in the SemiFix system, and the polyester tape were ruptured or the buttons were pulled into tunnel in Endobutton fixation. The mean maximum tensile strength of two interference screws with bone patellar tendon bone was statistically comparable to that of SemiFix with hamstring tendon. However biodegradable interference screw and Endobutton with hamstring tendon showed weaker maximum tensile strength than above three fixation techniques (P<0.05).

• 대한치과교정학회지
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• 제12권1호
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• pp.15-20
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• 1982

저자는 비교적 최근내 개발되어 시판되고있는 3가지 교정용 접착제를 교정을 위해 발치한 25개씩의 소구치에 접착하여 24시간후에 인장강도를 측정한 결과, 다음과 같은 결론을 얻었다. 각 제품의 평균인장강도는 교정력과 구강내에서 발생할 수 있는 외력의 합인 $29kg/cm^2$ 보다 높았으며, 제품C는 제품B, A보다 통계학적으로 높은 인장강도를 보이나, 제품B와 제품A는 통계학적으로 유의한 차가 없었다. 접착제가 떨어진 양상은 접착제가 치아와 bracket에 부분적으로 붙어서 떨어진 것이 가장 많았고 $(68\%)$, 접착제가 bracket에만 붙어서 떨어진 것 $(22.7\%)$, 접착제가 치아에만 붙어서 떨어진 것$(9.3\%)$순으로 나타났다.

• 한국가스학회지
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• 제7권2호
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• pp.48-53
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• 2003

에너지 관련 플랜트에 사용되는 배관은 플랜트의 성능이나 안전성유지에 있어서 중요한 설비의 일부이다. 본 연구에서는 고압탄소강 배관의 변형 및 파괴에 대한 음향방출 기초 자료를 얻기 위하여 압력용기용 배관재를 기계가공하여 인장시험편을 만든 후, 인장시험을 실시하여 항복, 소성변형 및 파괴에 이르기까지의 음향방출 신호를 분석하였다. 탄성영역, 최대인장강도 이전의 소성영역 및 최대인장강도 이후의 소성영역에서 검출된 음향방출의 시간-주파수 분석 결과는 탄성영역에서 항복영역까지는 비교적 낮은 저주파수 대역(250${\~}$350kHz)이 나타났으며, 소성영역에서는 저주파수뿐만 아니라 고주파수 대역(500kHz)도 나타났다. 인장시험 후, 이러한 각 영역의 구별이 가능하였던 원인은 항복영역에서의 전위의 이동, 집적에 따른 신호와 최대인장강도 이전의 소성영역에서의 전위들이 개재물이나 결정입계를 통과했을 때 나타나는 신호, 최대인장강도 이후에는 미소공동의 발생, 성장 및 합체에 의하여 나타나는 신호로 분류가 가능하였기 때문인 것으로 판단된다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.265-272
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• 1997

In this paper the bending collapse characteristics of 60 series Al rectangular tubes were studied with a pure bending collapse test rig which could apply the pure bending moment, there occured three kinds of bending collapse modes - local buckling, delayed buckling, tensile failure - depending on the b/t(width/thickness) ratio and material properties. Experiment results are compared with the results of finite element method.

• Fibers and Polymers
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• 제7권3호
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• pp.310-316
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• 2006

In this article, an attempt has been made to explain the failure mechanism of spun yams. The mechanism includes the aspects of generation and distribution of forces on a fibre under the tensile loading of a yam, the free body diagram of forces, the conditions for gripping and slipping of a fibre, and the initiation, propagation, and ultimate yam rupture in its weakest link. A simple mathematical model for the tenacity of spun yams has been proposed. The model is based on the translation of fibre bundle tenacity into the yam tenacity.