• 한국안전학회지
• /
• 제16권4호
• /
• pp.52-57
• /
• 2001

Fatigue crack growth behaviour of Ti-6A-4V alloy is investigated in air and salt solution environment at room temperature and $200^{\circ}C$. Fatigue crack growth rate is blown to be fast for the formation of corrosive product in hot salt environment. For the effect on corrosion fatigue crack growth behaviour of region II. fatigue crack growth rate in atmosphere had a little gap to both case, $200^{\circ}C$ and room temperature. However, it showed very fast tendency in salt corrosive atmosphere, and it was remarkably accelerated in $200^{\circ}C$ temperature salt environment. When $\Delta$K was approximately 30MPa(equation omitted), fatigue crack growth rate had a little difference between at room temperature and at $200^{\circ}C$ high temperature, however in case of salt corrosive environment the room temperature was 3.5 times Inter and $200^{\circ}C$ high temperature for 16 times than air environment respectively.

• 한국마린엔지니어링학회:학술대회논문집
• /
• 한국마린엔지니어링학회 2001년도 춘계학술대회 논문집
• /
• pp.146-151
• /
• 2001

Low temperature fatigue crack propagation ratio and characteristics of the pressure structural steel which is used for the low temperature pressure vessels. Fatigue crack properties was studied at room temperature of $25^{\circ}C$ and low temperature ranges $-60^{\circ}C,\; -80^{\circ}C \;and\; -100^{\circ}C$ with stress ratio of R=0.05, 0.1, 0.3 in the logarithmic relationship between the fatigue crack propagation rate (da/dN) and stress intensity factor $\DeltaK$, in low temperature case the relationship was extend to the range of low crack propagation rate. The fractured specimens were examined by SEM tested. That results showed specimen failed at low temperature exhibit the quasi-cleavage fracture formation, however, considerable ductility proceed final fracture.

• Computers and Concrete
• /
• 제16권4호
• /
• pp.587-604
• /
• 2015

The hybrid-type penalty method (HPM) is suitable for representing failure phenomena occurring during the transition from continua to discontinua in materials such as concrete. Initiation and propagation of dominant cracks and branching of cracks can easily be modeled as a discrete crack. The HPM represents a discrete crack by eliminating the penalty that represents the separation of the elements at the intersection boundary. This treatment is easy because no change in the degrees of freedom for the discrete crack is necessary. In addition, it is important to evaluate the correct deformation of the continua before the crack formation is initiated. To achieve this, we implemented a constitutive model of concrete for the HPM. In this paper, we explain the implemented constitutive model and describe the simulation of an anchor bolt pullout test using the HPM demonstrating its capability for evaluating progressive failure.

• 한국표면공학회지
• /
• 제14권3호
• /
• pp.142-150
• /
• 1981

The present paper clarified mechanism of quench crack formation in high carbon steel dur-ing quenching, and, in order to prevent the quench crack, proposed two basic guides in alloy design of high carbon tool steel. They are to raise Ms temperature of high carbon tool steel by addition of alloying elemen-ts such as Al and Co, and to decrease grain size of the carbon tool steel by addition of alloying elements of Al, B, Ti, Zr, and V, and by grain-refining heat treatment.

• Structural Engineering and Mechanics
• /
• 제15권2호
• /
• pp.159-180
• /
• 2003

In this paper spacing and width of flexural cracks in reinforced concrete beams are determined using two-dimensional finite element analysis. At early loading stages on the beam the primary crack spacing is based on the slip length, which is the development length required to resist the steel stress increment that occurs at a cracked section on the formation of the first flexural crack. A semi-empirical formula is presented in this paper for the determination of the slip length for a given beam. At higher load levels, the crack spacing is based on critical crack spacing, which is defined as the particular crack spacing that would produce a concrete tensile stress equal to the flexural strength of concrete. The resulting crack width is calculated as the relative difference in extensions of steel reinforcement and adjacent concrete evaluated at the cracked section. Finally a comparative study is undertaken, which indicates that the spacing and width of cracks calculated by this method agree well with values measured by other investigators.

• 한국세라믹학회지
• /
• 제29권1호
• /
• pp.23-28
• /
• 1992

Alumina ceramics was reinforced by in-situ formation of La-${\beta}$-aluminate in ${\alpha}$-alumina matrix. The powder mixture of which composition is (100-12x)Al2O3+x(La2O3+11Al2O3) was prepared for the formation of La-${\beta}$-aluminate in ${\alpha}$-alumina matrix. The amount of La-${\beta}$-aluminate in the matrix was controlled by varing x which is number of moles. The dense composite was produced by sintering at 1600$^{\circ}C$ in air or hot-pressing at 1550$^{\circ}C$ under 30 MPa. Bending strength and fracture toughness were increased, resulting from the grain growth inhibition and the crack deflection and crack bridging mechanism when La-${\beta}$-aluminate was produced in ${\alpha}$-alumina matrix.

• Steel and Composite Structures
• /
• 제50권2호
• /
• pp.237-247
• /
• 2024

Research on interfacial crack formation in orthotropic bi-materials has experienced a notable increase in recent years, driven by growing concerns about structural integrity and reliability. The existence of a crack at the interface of bi-materials has a substantial impact on mechanical strength and can ultimately lead to fracture. The primary objective of this article is to introduce a comprehensive analytical model and establish stress relationships for investigating interfacial crack between two non-identical orthotropic materials with desired crack-fiber angles. In this paper, we present the application of the Interfacial Maximum Tangential Stress (IMTS) criterion, in combination with the Reinforcement Isotropic Solid (RIS) model, to investigate the behavior of interfacial cracks in orthotropic bi-materials under mixed-mode I/II loading conditions. We analytically characterize the stress state at the interfacial crack tip using both Stress Intensity Factors (SIFs) and the T-stress term. Orthotropic materials, due to their anisotropic nature, can exhibit complex crack tip stress fields, making it challenging to predict crack initiation behavior. The secondary objective of this study is to employ the IMTS criterion to predict the crack initiation angle and explore the notable impact of the T-stress term on fracture behavior. Furthermore, we validate the effectiveness of our approach in evaluating Fracture Limit Curves (FLCs) for interfacial cracks in orthotropic bi-materials by comparing our FLCs with relevant experimental data from existing literature.

• 한국건축시공학회지
• /
• 제23권6호
• /
• pp.773-784
• /
• 2023

정부는 2007년부터 「국가건축기본계획」, 2014년부터 「건축서비스산업진흥법」 등을 통해 공공건축물의 품질향상을 도모하고 있으나, 이러한 추세에도 불구하고 대규모 아파트 공사에 비해 교육시설의 하자 발생 빈도가 높은 실정이다. 본 연구에서는 IPA분석기법을 응용한 사분면 분석 기법을 이용하여 교육시설에서 발생하는 균열의 주요 원인을 분석하여 이를 바탕으로 효율적인 균열 예측을 제시하고자 한다. 문헌연구를 통해 연구동향을 살펴보고 2019년부터 2021년까지 교육청으로 부터 받은 자료를 분석하여 주요 결함을 파악한다. 이후 설문조사와 전문가 자문을 바탕으로 균열 결함 15개 원인을 선정한다. 선정된 15개 원인에 대한 분석 결과를 바탕으로 2×2 Matrix를 활용해 균열 원인에 대한 작업애로 및 예방효과를 파악하고 중점적으로 검토해야 할 원인을 찾아 개선방향을 제시했다. 이러한 결과를 바탕으로 효과적인 교육시설의 균열 예방 및 관리에 기여할 수 있을 것으로 기대된다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
• /
• pp.418-423
• /
• 1998

This paper is intended to investigate the behavior of flexural-shear cracking in reinforced concrete beams without web reinforcement with FEM incorporated into a linear elastic fracture mechanics approach(LEFM). Each crack was propagated progressively by a finite length, then the quantitative reponses were examined. The results show that the horizontal crack was initiated by the bond-jnduced shear stress due to horizontal shearing action of the T-C force couple after the formation of the critical flexural crack. Also, the horizontal crack is considered to be a major factor of shear failure in slender reinforced concrete beams without web reinforcement.

• 한국세라믹학회지
• /
• 제28권10호
• /
• pp.785-792
• /
• 1991

An investigation of the crack propagation behavior of Al2O3-33Vol.% SiCw at 140$0^{\circ}C$ was conducted with various loading frequencies. Higher crack propagation was observed in lower frequency and higher load ratios. Interface sliding fracture due to glassy phase from the oxidation of SiCw and cavitation along grain boundary of diffusional creep appeared to be the main mechanism of fatigue fracture in slower crack propagation while interface sliding and whisker pull out aided by glassy phase formation played main role of fatigue fracture for higher crack growth condition. The frequency effect on deformation behavior was discussed with a Maxwell model.