• Title/Summary/Keyword: charpy impact test

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A Study on the Fracture Toughness Characteristics of FCAW Weldment of Steel for Offshore Structures (해양 구조물용 강재 FCAW 용접부의 파괴인성 특성에 관한 연구)

  • Kang Sung-Won;Kim Myung-Hyun;Kim Yong-Bin;Shin Yong-Taek;Lee Hae-Woo
    • Journal of Welding and Joining
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    • v.22 no.6
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    • pp.57-63
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    • 2004
  • Fracture toughness is an important parameter in designing offshore structures to ensure resistance to fracture at various temperatures. In this study, a series of experiments is carried out to obtain fracture toughness values (CTOD) of API 2W Gr.50B, welded using FCAW(Flux Cored Arc Weld). In particular, a comparison of absorbed impact energy and CTOD values are made with respect to two different welding groove shapes; double-V-groove and double-bevel-groove. Charpy impact tests are performed for specimens sampled near the root gap, and CTOD tests are carried out for three point bending specimens having the notch at weld zone. While Charpy impact test result is determined to be a good qualitative measure of fracture toughness, no quantitative correspondence between impact absorbed energy and CTOD values was found. Based on the experiment, it is observed that double-V-groove welds give lower transition temperature than those of double-bevel-groove.

Impact fracture behavior on particle volume fraction of nano silica composite materials (입자 함유율의 변화에 따른 나노 실리카 복합재료의 충격파괴거동)

  • LEE, Jung-Kyu;KOH, Sung Wi
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.51 no.3
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    • pp.454-460
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    • 2015
  • The present study is undertaken to evaluate the effect of volume fraction on the results of Charpy impact test for the rubber matrix filled with nano sized silica particles composites. The Charpy impact tests are conducted in the temperature range $0^{\circ}C$ and $-10^{\circ}C$. The range of volume fraction of silica particles tested are between 11% to 25%. The critical energy release rate $G_{IC}$ of the rubber matrix composites filled with nano sized silica particles is affected by silica volume fraction and it is shown that the value of $G_{IC}$ decreases as volume fraction increases. In regions close to the initial crack tip, fracture processes such as matrix deformation, silica particle debonding and delamination, and/or pull out between particles and matrix which is ascertained by SEM photographs of Charpy impact fracture surfaces.

Study of Crack Propagation and Absorbed Energy in Heat Affected Zone Using a Finite Element Method (유한요소법을 이용한 용접열영향부의 균열진전 및 샤르피 흡수에너지 연구)

  • Jang, Yun-Chan;Lee, Young-Seog
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.6
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    • pp.541-548
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    • 2009
  • In this study, Charpy impact test and numerical studies were performed to examine the effects of failure behavior and energy absorption on the notch position. For this purpose, carbon steel plate(SA-516 Gr. 70) with thickness of 25mm usually used for pressure vessel was welded by SMAW(Shielded Metal-Arc Welding)method and specimens were fabricated from the welded plate. The Charpy impact tests were then performed with specimens having different notch positions varying within HAZ. A series of three-dimensional FE analysis which simulates the Charpy test and crack propagation are carried out as well. We divided HAZ into two, three and four regions to apply mechanical properties of HAZ to FE-analys. Results reveal that the absorbed energies during impact test depend significantly on the notch position. To obtain the results of reliability, HAZ should be divided into at least three regions.

Effects of Mo and Nb on Tensile and Charpy Impact Properties of API X80 Linepipe Steels (API X80 라인파이프 강의 인장 및 샤르피 충격 특성에 미치는 Mo 및 Nb의 영향)

  • Min, Kyung-Zoon;Bae, Jin-Ho;Kim, Ki-Soo;Lee, Doh-Jae
    • Korean Journal of Metals and Materials
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    • v.49 no.10
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    • pp.766-773
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    • 2011
  • In this study, three kinds of linepipe steels were processed by changing the amount of Mo and Nb to investigate the effects on microstructures, tensile and Charpy impact properties. All the specimens consisted of acicular ferrite, granular bainite and secondary phases such as martensite and austenite constituents (MA). The increase in Mo raised the volume fractions of the granular bainite and MA, and raised the number of fine precipitates, which increased the yield and tensile strengths and decreased the upper self energy and energy transition temperatures. In the steel having less Mo and more Nb, the volume fractions of the granular bainite and MA decreased, and a finer microstructure was observed. This microstructure suppressed the formation of separation during Charpy impact testing and led to a higher upper shelf energy and lower energy transition temperature, while the yield and tensile strengths were lower than those of the steels with more Mo and less Nb.

Behavior of Fracture Deviation in the Impact Test of Narrow Laser Welds (충격 시험시 발생하는 레이저 용접부의 파괴 이탈 현상)

  • Na, Il;Kim, Jae-Do
    • Proceedings of the KWS Conference
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    • 1993.05a
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    • pp.120-124
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    • 1993
  • The Charpy V impact test on subsize was performed on narrow laser welds of low carbon steel sheets, joined by using a continuous wave 3kW CO$_2$ laser. Under certain conditions, a bimodal fracture behaviour has been experienced in Charpy V impact test of narrow laser beam welds. Deviation of the fracture path from the fusion zone into the base metal was dominated at high test temperature. It can be seen that the deviation always occurred after ductile initiation. If the deviation occurs on a small testing specimen, the same trend would happen on the actual laser welded structure. Fracture will then propagate through the base material even if the weld metal has low toughness.

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Evaluation on dynamic stress intensity factor using strain gage method (스트레인게이지법을 이용한 동적응력확대계수 평가)

  • Lee, H.C.;Kim, D.H.;Kim, J.H.;Moon, S.I.
    • Proceedings of the KSME Conference
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    • 2000.11a
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    • pp.304-309
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    • 2000
  • Strain gage method is used to evaluate the mode I dynamic stress intensity factor of marging steel(18Ni) and titanium alloy(Ti-6A1-4V). To decide the best strain gage position on specimen, static fracture toughness test was performed. Then instrumented charpy impact test and dynamic tensile test was performed by using strain gage method for evlauating dynamic stress intensity factor. Strain gage signals on the crack tip region are used to calculate the stress intensity factors. It is found that strain gage method is more useful than method by using load which is obtained from impact tup to assess dynamic characteristics such as dynamic stress intensity factor.

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Separation Phenomenon Occurring during Charpy Impact test of API X80 Linepipe Steels (API X80 라인파이프강의 샤르피 충격 시험 시 발생하는 파열 현상 연구)

  • Shin, Sang Yong;Hong, Suckmin;Bae, Jin-ho;Kim, Kisoo;Lee, Sunghak
    • Korean Journal of Metals and Materials
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    • v.47 no.3
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    • pp.155-168
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    • 2009
  • In this study, microstructural investigation was conducted on the separation phenomenon occurring during Charpy impact tests of API X80 linepipe steels. Particular emphasis was placed on the role of microstructural phases present in the API X80 steels such as acicular ferrite, bainite, and hard secondary phases. Detailed microstructural analysis of fractured impact specimens showed that highly elongated bainite worked as prior initiation sites for separations, and that the number and length of separations increased with increasing volume fraction of bainite. In the steels having high work hardenability, tearing-shaped separations were found because the hammer-impacted region was seriously hardened during the impact test, which led to the reduction in the impact toughness. As the test temperature decreased, the tendency of separations increased, but separations were not observed when the cleavage fracture prevailed at very low temperatures. Thus, the minimization of the formation of bainite and secondary phases in the steels would be beneficial for preventing or minimizing separations because separations deteriorated low-temperature impact toughness.

Evaluation of Low Temperature Properties in 18Cr Ferritic Stainless Steel Welds (18Cr 페라이트계 스테인리스강의 용접부 저온 특성 평가)

  • Lee, Won-Bae;U, In-Su;Eom, Sang-Ho;Lee, Jong-Bong
    • Proceedings of the KWS Conference
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    • 2007.11a
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    • pp.138-140
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    • 2007
  • This study aimed to evaluate the low temperature properties of the 18Cr ferritic stainless steel weld. Applied welding methods were LB(Laser Beam) and GTA(Gas Tungsten Arc) welding to compare the different low temperature properties of the welds. Low temperature properties were evaluated by the Charpy impact, Erichsen and Expansion test at low temperature. LB weld showed superior low temperature properties in the cases of the Charpy impact test and expansion test at low temperature, while GTA weld showed a superior low temperature property in the case of Erichsen test at low temperature. The different low temperature properties with test methods are still under analysis and may be due to different crack path depending on the microstructure, test speed and stress concentration during test.

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Fracture Characteristics of D 3507 and D 3631 City Gas Steel Pipes (도시가스용 D3507 및 D3631 강관의 파괴특성)

  • 박재학;김한국;신규인;김만원
    • Journal of the Korean Society of Safety
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    • v.16 no.4
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    • pp.39-46
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    • 2001
  • It is noted that KS D 3507 pipe steel has several problems when it is used as a city gas pipe at medium pressure. So new pipe steel, KS D 3631, was developed in order to be used as a pipe for medium and low pressure and now it is being substituted for D 3507. In this study, several mechanical tests, such as tensile test, microhardness test, and Charpy impact test were conducted to get material properties of D 3507 and D 3631 pipe steels. And also microstructures at the weld and heat affected zones were observed for the two materials. From the Charpy test results $K_{IC}/$ was estimated for the upper and lower shelf and the critical crack length is calculated for supposed axial semi-elliptical surface cracks. And the burst pressure is estimated as a function of wear depth for a defective D 3631 pipe by using the finite element method. The burst pressure is also calculated for pipes with an axial crack by using the published equations.

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Mechanical testing of the behavior of steel 1.7147 at different temperatures

  • Brnic, Josip;Turkalj, Goran;Canadija, Marko
    • Steel and Composite Structures
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    • v.17 no.5
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    • pp.549-560
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    • 2014
  • The paper provides the test results and analysis on the behavior of steel 1.7147 at different temperatures. Mechanical uniaxial tests were used to determine mechanical properties, resistance to creep and Charpy impact tests to determine impact energy. Test results are presented in the form of engineering stress-strain diagrams, creep curves as well as numerical data related to impact energy. The results show that the tensile strength has the highest value at room temperature, and the same goes for the yield strength as well as for modulus of elasticity. After room temperature both of mentioned properties decrease with temperature increasing. Some of creep curves were modeled using rheological models and analytical equation. Based on Charpy impact energy an assessment of fracture toughness was made.