• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.158-163
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• 2009

Titanium alloy sheets have excellent specific strength and corrosion resistance as well as good performance at high temperature. Recently, titanium alloys are widely employed not only aerospace parts but also bio prothesis and motorcycle. However, due to the low formability and large spring back at room temperature, titanium alloy sheets were usually formed by slow forming or hot forming with heating die and specimen. In the sheet metal forming area, FE simulation technique to optimize forming process is widely used. To achieve high accuracy FE simulation results, Identification of material properties and deformation characteristic such as yield function are very important. In this study, uniaxial tensile and biaxial tensile test of Ti-6Al-4V alloy sheet with thickness of 1.0mm were performed at elevated temperature of 873k. Biaxial tensile tests with cruciform specimen were performed until the specimen was breakdown to characterize the yield locus of Ti-6Al-4V alloy sheet. The experimental results for yield locus are compared with the theoretical predictions based on Von Mises, Hill, Logan-Hosford, and Balat's model. Among these Logan-Hosford's yield criterion well predicts the experimental results.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.153-160
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• 2003

Nonlinear finite element analysis of reinforced concrete panels subjected to biaxial tensile loads are carried out by using a 9-node assumed strain shell element. The present study mainly focuses on the performance evaluation of material models such as cracking criteria, tension stiffening model and steel model in the membrane energy dominant situation. From numerical results, the exponential form of tension stiffening model together with the use of average yield stress model for the steel embedded in the concrete performs well in the panel analysis under biaxial tensile loading condition and it produces a good agreement with experiment results. Finally, the present results are provided as a benchmark test for reinforced concrete panel structures.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.399-402
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• 2007

The classical two dimensional modulus of rupture test was generalized to three dimensions. Using this new method, the biaxial tensile strength can be measured with only one actuator. A circular plate is used in this method unlike a prismatic beam in the classical modulus of rupture test. The stress field in this specimen is isotropic and uniform in a plane paralle1 to the bottom surface of the specimen. The relation between the applied load and the maximum stress is derived analytical1y using Timoshenko's solution. A set of experimental data is presented.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.206-211
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• 2000

Fatigue test was conducted on a S45C steel using hour-glass shaped smooth tubular specimen under biaxial loading in order to investigate the crack formation and growth at room temperature. Three types of loading system, i.e fully reserved cyclic torsion without a superimposed static tension or compression, fully reserved cyclic torsion with a superimposed static tension and fully reserved cyclic torsion with a superimposed static compression were employed. The test results show that a superimposed static tensile mean stress reduced fatigue lifetime. however a superimposed static compressive mean stress increased fatigue lifetime. Experimental results indicated that cracks were initiated on planes of maximum shear strain with either a superimposed mean stresses or not. A biaxial mean stress had an effect on the direction which cracks nucleated and propagated at stage I (mode II).

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.213-214
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• 2009

Recently the use of ferritic stainless steels for automotive exhaust system has been increased dramatically. A detailed knowledge of material behavior of ferritic stainless steel is important for successful manufacturing of exhaust systems. To achieve this goal, numerical study of square cup deep drawing for ferritic stainless steel sheet, type 409L was conducted with Yld2000-24. Uniaxial tensile test and hydraulic bulge test were performed to characterize plastic material behavior. Finite element simulation of square cup deep drawing was performed successfully.

• 한국공간구조학회논문집
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• 제16권1호
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• pp.35-42
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• 2016

Until recently, almost all ETFE film structures that have been erected is the cushion type because there are problems at lower allowable strength under elastic range and viscosity behaviour such as creep and relaxation of ETFE films under long-term stresses. But the number of tension type structures is currently increasing. This paper proposes the stretch fabrication of ETFE film to verify the applicability of ETFE films to tensile membrane structures. First of all, to investigate the possibility of application on tensile membrane structures, the stretch fabrication test is carried out, and it is verified that it is possible to increase the yield strength of the film membrane structures. After simulating the experiment also carries out an analytical investigation, and the effectiveness of the elasto-plastic analysis considering the viscous behavior of the film is investigated. Finally, post-aging tension measurement is conducted at the experimental facilities, and the viscosity behavior resulting from relaxation is investigated with respect to tensile membrane structures.

• 한국지반공학회논문집
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• 제25권10호
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• pp.17-30
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• 2009

지하에 공동을 건설하는 터널 공사의 경우 초기 응력의 집중 및 발파와 같은 시공단계에서의 과도한 에너지의 적용으로 인하여 주변 암반에 손상을 발생시킨다. 이러한 손상의 발생은 터널에 작용하는 하중 및 터널 주변 암반의 흐름조건에 상당한 영향을 끼친다. 이러한 이유로 터널 주변에 발생하는 손상구간에 대하여 다양한 연구가 수행되었다. 본 연구에서는 유사암석으로 제작된 공동이 존재하는 절리모델의 이축압축실험을 통하여 공동주변의 손상발생을 연구하였다. 절리면은 수평면과 $30^{\circ}$, $45^{\circ}$, $60^{\circ}$의 조건으로 형성되었으며, 초조강시멘트 재료를 이용하여 유사절리모델을 제작하였다. 이축압축 실험결과 공동주변에서는 절리면에 수직한 방향으로 인장균열의 발생이 관측되었으며, 균열의 진행으로 인하여 암반블록이 형성되었으며, 진행하는 인장균열이 다른 절리면에 도달하여 암반블록이 완전히 형성된 경우 탈락하는 과정을 보였다. 이러한 인장균열의 진전은 절리면의 각도에 따라 상이한데 절리면의 각도가 클수록 안정적이며 진행성의 균열 진전 양상이 관측되었다. 이러한 인장균열의 발달은 절리면으로 구성된 암편을 보로 가정 할 경우 공동의 곡률로 인한 기하학적 형상의 불규칙성으로 인하여 모멘트가 작용하는 것으로 판단된다. 이상의 실험결과를 입자요소해석 방법을 기반으로 하는 PFC 2D를 이용하여 모사하였다. 해석결과 실험에서 관측한 바와 같이 절리면 각도가 작을수록 손상대의 폭은 넓어지며 인장균열의 진행에 의한 암반블록의 형성이 관측되었다. 또한 상호작용이 발생하는 균열을 조사한 결과 수치해석에서도 절리면의 각도가 작은 조건에서 진행성의 파괴가 나타났다.

• Advanced Composite Materials
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• 제18권4호
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• pp.395-413
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• 2009

Impact tests on high-strength membrane materials under biaxial loads were experimentally conducted in order to evaluate influence of biaxial loads on impact fracture of the membrane materials for the inflated applications. Cruciform specimens of the membrane materials were fabricated for applying biaxial loadings during the impact test. A steel ball was shot using a compressed nitrogen gas gun, and struck the membrane specimen. Impact tests on uniaxial strip specimens were also conducted to obtain the effect of specimen configuration and boundary condition on the impact fracture. The results of the measured crack length and the ultra-high speed photographs indicate the impact fracture properties of the membrane fabrics under biaxial loadings. Crack length due to the impact increased with applied tensile load, and the impact damages of the cruciform membrane materials under biaxial loadings were smaller than those of under uniaxial loadings. Impact fracture of the strip specimen was more severe than that of the cruciform specimen due to the difference of boundary conditions.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.599-606
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• 2003

An analytical model which can simulate the post-cracking nonlinear behavior of reinforced concrete (RC) members such as bars and panels subjected to uniaxial and biaxial tensile stresses is presented. The proposed model includes the description of biaxial failure criteria and the average stress-strain relation of reinforcing steel. Based on strain distribution functions of steel and concrete after cracking, average response of an embedded reinforcement, a criterion to consider the tension-stiffening effect is proposed using the concept of average stresses and strains. The validity of the introduced model is established by comparing the analytical predictions for reinforced concrete tension members with results from experimental studies. Finally, correlation studies between analytical results and experimental data from biaxial tension test are conducted with the objective to establish the validity of the proposed models and identify the significance of various effects on the response of biaxially loaded reinforced concrete panels.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.189-192
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• 2007

고무제품의 경우 구조성능평가를 위해 단축인장, 순수전단, 이축인장 및 압축시험을 수행한다. 일반적으로 단축인장시험값을 기초물성으로 사용하며 용도에 따라 다른 시험을 수행한다. 검증을 위해 단축인장시험/해석 결과를 비교하여 타당성을 확인했다. 본 연구에서는 전단강성이 주요인자인 제품의 성능평가를 위해 단축인장시험에서 획득한 물성을 적용한 QLS 해석모델의 결과를 비교, 검증하였다.