• Title/Summary/Keyword: Fracture toughness

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Numerical analysis on the welding residual stress and fracture toughness of the heavy thick steel welded joints by welding processes

  • Bang, HanSur;Bang, HeeSeon
    • Journal of Welding and Joining
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    • v.33 no.2
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    • pp.32-39
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    • 2015
  • This study examined the welding residual stress and fracture toughness of 78mm thick steel electro gas welding (EGW) and flux cored arc welding (FCAW) welded joints by numerical analyses of the thermal elasto-plastic behavior and fracture toughness(KIC). The residual stress, fracture toughness characteristics and production mechanism on the welded joints were clarified. Moreover, the effects of the welding process (EGW and FCAW) on the welding residual stresses and fracture toughness of welded joints were evaluated. The results showed that the new welding process (EGW) appears to be an effective substitute for the existing welding process (FCAW) in a thick steel plate with high strength.

Effect of Plasma Treatment of Aluminum on the Fracture Toughness of Aluminum/CFRP Composites (알루미늄의 플라즈마 표면처리가 알루미늄/CFRP 복합재의 파괴인성에 미치는 영향)

  • 신명근;이경엽
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.8
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    • pp.153-157
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    • 2003
  • In the present work, the effect of plasma treatment of aluminum on the fracture toughness of CFRP/aluminum composites was investigated. The surface of the aluminum was treated by a DC plasma. The plasma treatment was carried out at volume ratio of acetylene gas to nitrogen gas of 5:5 and the treatment time used was 30 sec. Cracked lap shear specimens of aluminum/CFRP composites were made using secondary bonding procedure. Fracture toughness of aluminum/CFRP composites was determined using the work factor approach. Then, the fracture toughness of plasma-treated aluminum/CFRP composites was compared with that of untreated aluminum/CFRP composites. The results showed that the fracture toughness of plasma-treated aluminum/CFRP composites was about 50 % higher than that of untreated aluminum/CFRP composites.

Evaluation for Fracture Toughness with Considering the Thermal Energy (열에너지를 고려한 파괴인성치 고찰)

  • 김정표;임창현;석창성
    • Journal of the Korean Society of Safety
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    • v.16 no.2
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    • pp.1-6
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    • 2001
  • In the case of a crack propagation a portion of the work of inelastic deformation near the crack tip is dissipated as heat. In order to understand the thermal effect on fracture toughness, tensile tests were carried out using thermocouples to monitor the variation of temperature. The experimental results show that the temperature of specimen was increased $5.4^{\circ}C$ at static load condition. And the thermal effect is investigated connected with the steady-state stress in the vicinity of a crack propagation in the elastic-plastic C-T specimen theoretically. And fracture toughness, the energy to make crack surfaces, presented correctively. The fracture toughness with considering heat at the blunting of the crack tip is lower about 16.9% than that of ignoring heat. So, it is resonable to apply the fracture toughness with considering thermal energy and it would be good explanation for constraint effect depending on the configuration in the presence of excessive plasticity.

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An Evaluation Method of fracture Toughness on Interface Cracks in Bonded Dissimilar Materials (이종 접합체의 계면균열에 대한 파괴인성의 평가방법)

  • 정남용
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.4
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    • pp.110-116
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    • 2003
  • In this paper, an evaluation method of fracture toughness on interface cracks has been investigated under various mixed-mode conditions of the bonded scarf joints. Two types of the bonded scarf joints with an interface crack were prepared to analyze the stress intensity factors using boundary element method(BEM) and to perform the fracture toughness test. From the results of fracture toughness experiments and BEM analysis, an evaluation method of fracture toughness on interface cracks in the bonded dissimilar materials has been proposed and discussed.

Analysis of Economical Validity for Implementation of Telematics in Construction Fields (Telematics 기술의 건설현장 적용을 위한 경제적 타당성 분석)

  • Lee Sung Hyun;Lee Dong Wook;Koo Ja Kyung;Lee Tai Sik
    • Journal of the Korean Society for Railway
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    • v.8 no.5
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    • pp.444-453
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    • 2005
  • The safety evaluations of railway wheelsets make use of the static fracture toughness obtained in ingot materials. The static fracture toughness of wheelset materials has been extensively studied by experiments, but the dynamic fracture toughness with respect to wheelset materials has not been studied enough yet. It is necessary to evaluate the characteristics of the fracture mechanics depending on each location for a full-scale wheelset for high-speed trains, because the load state for each location of the wheelset while running is different the contact load between the wheel and rail, cyclic stress in the wheel plate, etc. This paper deals with the fracture toughness depend on load rates. The fracture toughness depending on load rate data shows that once the downward curve from quasi-static values was reached, subsequent values showed a slow increase with respect to the impact velocity. This means that dynamic fracture toughness should be considered in the design code of the wheelset material.

Dynamic Fracture Toughness of Chevron-notch Ceramic Specimens measured in Split Hopkinson Pressure Bar

  • Lee, Yeon-Soo;Yoon, Young-Ki;Yoon, Hi-Seak
    • International Journal of Precision Engineering and Manufacturing
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    • v.3 no.3
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    • pp.69-75
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    • 2002
  • Measuring dynamic fracture toughness of brittle and small ceramic specimen is very difficult in a SHPB (Split Hopkinson Pressure Bar). As a countermeasure to this difficulty, a dynamic fracture toughness measuring method by the Chevron-notch ceramic specimen was proposed. Tested chevron specimens were of Chevron notch angles of 90$^{\circ}$, 100$^{\circ}$ and 110$^{\circ}$. Through finite element analysis, shape parameters of the Chevron-notch specimens according to notch angles were calculated. And the static fracture tough1ess of the Chevron-notch alumina specimen was measured as 3.8MPa√m similar to that of CT specimen with a precrack. Dynamic fracture toughness was 4.5MPa√m slightly higher than the static one. It was shown in this study that the proposed Chevron-notch specimens are valid to measure dynamic fracture toughness of extremely brittle materials such as ceramic.

Effect of Loading Speed on the Fracture Toughness and Damage Zone around a Crack Tip of Rubber-Modified Epoxy Resin (부하속도 변화에 의한 고무변성 에폭시 수지의 균열선단 손상역과 파괴인성)

  • 이덕보
    • Textile Science and Engineering
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    • v.39 no.4
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    • pp.430-435
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    • 2002
  • A rubber-modified epoxy resin is widely used as the adhesive and as the matrix material for fiber composite materials. The structural integrity of composite materials depends on fracture toughness of the matrix resin. In this study, we investigated the fracture toughness and the damage zone around a crack tip of the rubber-modified epoxy resin whose volume fractions of rubber(CTBN 1300$\times$8) were O%, 5% and 15% under several loading speeds. The fracture toughness(K$_{IC}$) and the fracture energy(G$_{IC}$) were measured using 3-point bending specimens. The 4-point bending specimens were also used to observe damage zones in the vicinity of crack tips for the modified resins. The results show that the fracture toughness and the size of damage zones at 5% and 15% rubber contents decreased with increase in loading speed.eed.

Evaluation for Fracture Toughness with Considering the Thermal Energy (열에너지를 고려한 파괴인성치 고찰)

  • Park, Jae-Sil;Kim, Jeong-Pyo;Seok, Chang-Sung
    • Proceedings of the KSME Conference
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    • pp.9-15
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    • 2001
  • In the case of a crack propagation, a portion of the work of inelastic deformation near the crack tip is dissipated as heat. In order to understand the thermal effect on fracture toughness, tensile test was carried out using thermocouples to monitor the variation of temperature with SA516 Gr70. The experimental results show that the temperature of specimen was increased $3.6^{\circ}C$ at static load condition. And the thermal effect was investigated connected with the steady-state stress in the vicinity of a crack propagation in the elastic-plastic C-T specimen theoretically. And fracture toughness, the energy to make crack surfaces, presented correctively. The fracture toughness with considering heat at the blunting of the crack tip ws lower about 19.3% than that of ignoring heat. So, it is resonable to apply the fracture toughness with considering thermal energy and it would be good explanation for constraint effect depending on the configuration in the presence of excessive plasticity.

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Evaluation of Fracture Toughness on Interface Cracks in Bonded Components of Dissimilar Materials (이종 접합부재의 계면균열 파괴인성의 평가)

  • Chung, Nam-Yong;Lee, Myung-Dae;Park, Chul-Hee
    • Proceedings of the KSME Conference
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    • pp.346-351
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    • 2003
  • In this paper, an evaluation method of fracture toughness on interface cracks has been investigated under various mixed-mode conditions of the bonded scarf joints. Two types of the bonded scarf joints with an interface crack were prepared to analyze the stress intensity factors using boundary element method(BEM) and to perform the fracture toughness test. From the results of fracture toughness experiments and BEM analysis, an evaluation method of fracture toughness on interface cracks in the bonded components of dissimilar materials has been proposed and discussed.

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Mehods of Fracture Toughness and Evaluation for Interface Crack in Adhesively Bonded Joints (접착이음의 계면균열에 대한 파괴인성 및 평가방법)

  • 정남용
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • pp.220-226
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    • 1998
  • In this pater, a method of strength evaluation applying fracture mechanics in adhesively bonded joints of A1/A1 materials was investigated. Various adhesively bonded joints of double-cantilever beam with a interfacial crack in its adhesive layer were prepared for the fracture toughness test of comprehensive mixed mode conditions from nearly pure mode I to mode II. The experiment of fracture toughness was carried out under various mixed mode conditions with an interfacial crack and critical energy release rate, Gc by the experimental measurements of compliances was determined. From the results, fracture toughness on mixed mode with an interfacial crack is well characterized by strain energy release rate and a method of strength evaluation by the fracture toughness in adhesively bonded joints of A1/A1 materials was discussed.

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