• Title/Summary/Keyword: Brittle material

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Energy and strength in brittle materials

  • Speranzini, Emanuela
    • Smart Structures and Systems
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    • v.23 no.4
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    • pp.373-385
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    • 2019
  • A study concerning the strength of brittle materials is presented in this paper. The failure behavior was investigated examining the plane of the crack after the failure and comparing the results obtained with those deriving from the fracture mechanics theory. Although the proposed methods are valid in general for brittle materials, the experiment was performed on glass because the results are more significant for this. Glass elements of various sizes and different edge finishes were subjected to bending tests until collapsing. The bending results were studied in terms of failure load and energy dissipation, and the fracture surfaces were examined by means of microscopic analysis, in which the depth of the flaw and the mirror radius of the fracture were measured and the strength was calculated. These results agreed with those obtained from the fracture mechanics analysis.

A Study on Characteristic of Fracture in Lap Joint Welded STS429L (STS429L 겹침 용접부의 파단 특성에 관한 연구)

  • Choi, Dong-Soon;Kim, Jae-Seong;Kim, Hyun-Jae;Lee, Bo-Young
    • Journal of Welding and Joining
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    • v.27 no.5
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    • pp.49-54
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    • 2009
  • Recently, a demand of ferritic STS is increasing rapidly in automobile exhaust system. Exhaust manifolds are the part nearest to the engine so that the material is exposed to high temperature exhaust gas. Excellent heat resistant properties, especially high temperature strength, thermal fatigue resistance and high corrosion resistance are necessary for these parts. STS429L contains 15 weight percent of Cr and low Mo, so has good price competitive. And it has excellent high temperature strength and corrosion resistance, so receives attentions as material that applying to exhaust manifold. In tensile test of lap joint welded STS 429L, most of specimens are failed in base metal, but occurs brittle fracture in weld metals at some specimens in the face of good welding conditions. In the process of tensile test, lap joint welded STS429L specimens are transformed locally. The brittle fracture occurs that local transforming area exists in weld metals. But, butt welding specimens made by same materials showed ductile fracture in tensile test and bending test. In this study, suppose the reason of brittle fracture is in the combined local transform and tensile stress, through analysis of bead geometry, evaluate geometrical factor of brittle fracture in lap joint welded STS429L.

An Evaluation of the Effect of Micro-cracks on Macro Elastic Moduli (매크로 탄성 계수에 미치는 마이크로 크랙의 영향 평가)

  • Kang, Sung-Soo;Kim, Hong-Gun
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.15 no.5
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    • pp.97-103
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    • 2006
  • A meso-scale analysis method using the natural element method, which is a kind of meshless method, is proposed for the analysis of material damage of brittle microcracking solids such as ceramic materials, concrete and rocks. The microcracking is assumed to occur along Voronoi edges in the Voronoi diagram generated using the nodal points as the generators. The mechanical effect of microcracks is considered by controlling the material constants in the neighborhood of the microcracks. The macro elastic moduli of anisotropic as well as isotropic solids containing a number of randomly distributed microcracks are calculated in order to demonstrate the validity of the proposed method.

Material Degradation in KS D 3503 SS400 Rolled Steel at $179^{\circ}C$ (KS D 3503 SS400 압연강 $179^{\circ}C$에서의 재질열화 연구)

  • Baek, Un-Bong;Park, Jong-Seo;Nahm, Seung-Hoon
    • Journal of the Korean Society of Safety
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    • v.21 no.4 s.76
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    • pp.13-18
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    • 2006
  • In spite of frequent defect in industrial boilers, life assessment or diagnostic method for them has not been actively studied. In this research, SS400 carbon steel used in industrial boilers is simulated with artificial aging heat treatment. To do qualitative life assessment, differences in micro-structures and hardness of SS400 by the degradation time are studied. In addition, variation in material properties by aging was observed with the tensile test at room temperature and $179^{\circ}C$ and changes in ductile to brittle transition temperature was observed with the charpy impact test performed at several test temperature.

Evaluation of Grinding Characteristics on the Hardened-Brittle and Difficult-to-Grind Materials (경취성 난연삭 재료의 연삭특성 평가)

  • Kwak, T. K.;Kwak, J. S.;Ha, M. K.;Koo, Y.;Ryoo, I. I.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.1101-1104
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    • 2001
  • The special purposed materials, such as ceramics and stainless steel, are widely used in the various industrial area. They have properties of the higher strength of material, the wear-resistance, and the corrosion proof. But ceramics is a difficult-to-grind material which possesses the higher level of a strength and a brittleness. In this study, the theoretical investigation of a grinding force and of a surface roughness was conducted. The evaluations of grinding characteristics on the hardened-brittle and difficult-to-grind materials were experimentally carried out.

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Natural Element Analysis on Macro Elastic Moduli for Materials with Micro-cracks (마이크로 크랙을 포함한 재료의 매크로 탄성 정수에 관한 자연요소해석)

  • Kang, Sung-Soo
    • Journal of Advanced Marine Engineering and Technology
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    • v.30 no.6
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    • pp.716-723
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    • 2006
  • A meso-scale analysis method using the natural element method is proposed for the analysis of material damage of brittle microcracking solids. The microcracking is assumed to occur along Voronoi edges in the Voronoi diagram generated using the nodal points as the generators. The mechanical effect of microcracks is considered by controlling the material constants in the neighborhood of the micorcracks. The macro elastic moduli of isotropic solids containing a number of randomly distributed microcracks are calculated considering the effect of microcrack closure to demonstrate the validity of the proposed method.

Degradation Damage Evaluation of High Temperature Structural Components by Electrochemical Anodic Polarization Test (전기화학적 양극분극시험에 의한 고온 설비부재의 열화손상 평가)

  • Yu, Ho-Seon;Song, Mun-Sang;Song, Gi-Uk;Ryu, Dae-Yeong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.6 s.177
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    • pp.1398-1407
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    • 2000
  • The structural steels of power plant show the decrease of mechanical properties due to degradation such as temper embrittlement, creep damage and softening during long-term operation at high temper ature. The typical causes of material degradation damage are the creation and coarsening of carbides(M23C6, M6C) and the segregation of impurities(P, Sb and Sn) to grain boundary. It is also well known that material degradation induces the cleavage fracture and increases the ductile-brittle transition temperature of steels. So, it is very important to evaluate degradation damage to secure the reliable and efficient service condition and to prevent brittle failure in service. However, it would not be appropriate to sample a large test piece from in-service components. Therefore, it is necessary to develop a couple of new approaches to the non-destructive estimation technique which may be applicable to assessing the material degradation of the components with not to influence their essential strength. The purpose of this study is to propose and establish a new electrochemical technique for non-destructive evaluation of material degradation damage for Cr-Mo steels which is widely used in the high temperature structural components. And the electrochemical anodic polarization test results are compared with those of semi-nondestructive SP test.

Influence of pH in 3.5% NaCl aqueous solution on corrosion fatigue-fracture of dual phase steel (3.5% NaCl 수용액의 pH변화가 복합조직강의 부식피로파괴에 미치는 영향)

  • 오세욱;안호민;도영문
    • Journal of Ocean Engineering and Technology
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    • v.1 no.2
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    • pp.123-129
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    • 1987
  • Corrosion fatigue fracture of dual phase steel(SS41) and raw material steel(SS41) were investigated in 3.5% NaCl aqueous solution at PH 4,6,9 and 11. The fatigue limit of dual phase steel is increased approximately 1.8 times larger than that of raw material in air. The corrosion fatigue life of dual phase steel is about 5-10 times larger than that of raw material in 3.5% NaCl aqueous solution. The reduction of fatigue life is larger for the acidsalt solution than for the alkali salt solution. The reduction of stress level on the reduction ratio of corrosion fatigue life is large as pH 6-11. The reduction ratio of corrosion fatigue life of dual phase steel and raw material is nearly coincided at pH 2. While at pH4-2 the reduction ratio of corrosion fatigue life only depends on the corrosion effect. It has been found that the corrosion resistance effect of dual phase steel is smaller than that of raw material in corrosion fatigue crack propagation rate. As pH below 6 is changed, it can be clearly observed from raw material that the brittle intergranular fracture is characterized, and from the above result, the influence of corrosion of dual phase steel is small.

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Effect of Interfacial Debonding on the Material Properties of Brittle Matrix Composites (취성기지 복합재료의 물성치에 미치는 계면분리의 영향)

  • 염영진;진민철
    • Composites Research
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    • v.16 no.1
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    • pp.42-49
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    • 2003
  • Brittle matrix composites often have interfacial debonding between the fiber and matrix which may lead to strength and stiffness degradation. The effect of interfacial debonding and fiber volume fraction on the mechanical properties of composite material were studied by using finite element method. Firstly, the modelling of fiber and matrix constituting the composite material was simplified under some assumptions. Traction and displacement continuity conditions were imposed along the boundary of adjacent representative volume elements. In order to obtain the effective material properties of composite material, stiffness constants were inverted. Numerical values of longitudinal moduli in case of perfect bonding were compared with theoretical values obtained by rule of mixtures and yielded consistency. Material properties of composite with large debonding an81e were found to decrease even though the fiber volume fraction increased.

Cause of and Solution for Damage to STS310S Tube in Heat Exchange Devices (열교환기 STS310S 튜브의 손상 원인 및 대책)

  • Kim, Jin Wook;Kim, Seon Hwa;Jeong, Jin Hyuk;Kim, Young Soo;Nam, Ki Woo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.2
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    • pp.187-193
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    • 2015
  • The STS310S tube has excellent heat transfer ability and is widely used as the material for heat transfer tubes in heat exchange devices. Mixtures of gas and water flow inside the tube whereas hot flame flows outside it. In this environment, the material of the tube may undergo embrittlement, which can cause leakage. Cracks can propagate from the inside of the tube to its outside and result in brittle fracture. This study identified the cause of brittle fracture in the STS310S tube through experiments and discussion, and proposed solutions to prevent fracture.