• Title, Summary, Keyword: charpy impact properties

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Charpy Impact Properties of Heat Affected Zones of API X80 Linepipe Steels Containing Complex Oxides (복합산화물이 형성된 API X80 라인파이프강의 용접열영향부 샤르피 흡수에너지)

  • Sung, Hyo Kyung;Shin, Sang Yong;Cha, Wooyeol;Oh, Kyungshik;Lee, Sunghak;Kim, Nack J.
    • Korean Journal of Metals and Materials
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    • v.48 no.10
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    • pp.875-883
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    • 2010
  • This study assessed the Charpy impact properties of the heat-affected zones (HAZs) of API X80 linepipe steels containing complex oxides. Three types of steel were fabricated by adding Mg and $O_2$ to form complex oxides and their microstructures and Charpy impact properties were investigated. The number of complex oxides increased with the amount of excess Mg and $O_2$ that was included in the steels. Simulated HAZs containing a number of oxides showed a high volume fraction of acicular ferrite (AF) because the oxides acted as nucleation sites for AF, thereby leading to an improvement in the Charpy impact properties. According to a correlation study between the heat input, the volume fraction of the AF, and the Charpy impact properties, ductile fractures occurred predominantly when the fraction of the AF was 20% or higher; moreover, the Charpy absorbed energy was excellent at more than 100 J. These findings suggest that the improvement of the Charpy impact properties of the HAZs was associated with the active nucleation of AF in the oxide-containing steel HAZs.

A study on the Dynamic Fracture Toughness for Polymeric Materials (폴리머재료의 파괴인성치에 관한 연구)

  • 최영식;박명균
    • Proceedings of the Safety Management and Science Conference
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    • pp.311-317
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    • 2001
  • The notched Charpy and Izod impact tests are the most prevalent techniques used to characterize the effects of high impulse loads on ploymeric materials. An analysis method for rubber toughened PVC is suggested to evaluate critical strain energy release rates(Gc) from the Charpy impact energy measurements. An Instrumented Charpy Impact tester was used to extract ancillary information concerning fracture properties in addition to total fracture properties and maximum critical loads. The stress intensity factor Kd was computed for varying amounts of rubber contents from the obtained maximum critical loads and also toughening effects were investigated as well.

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A study on the Determination of Fractuye Parameters for Rubber Toughened Polymeric Materials Using Instrumented Charpy Impact Test (샤피충격시험기를 이용한 고무보강 폴리머재료의 파괴인자 결정에 관한연구)

  • Choi, Young-Sic;Park, Myung-Kyun;Bahk, S.M.
    • Proceedings of the KSME Conference
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    • pp.389-394
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    • 2001
  • The notched Charpy and Izod impact tests arc the most prevalent techniques used to characterize the effects of high impulse loads on ploymeric materials. An analysis method for rubber toughened PVC is suggested to evaluate critical strain energy release rates(Gc) from the Charpy impact energy measurements. An Instrumented Charpy impact tester was used to extract ancillary information concerning fracture properties in addition to total fracture properties and maximum critical loads. The stress intensity factor Kd was computed for varying amounts of rubber contents from the obtained maximum critical loads and also toughening effects were investigated as well.

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Effects of Alloying Elements and the Cooling Condition on the Microstructure, Tensile Properties, and Charpy Impact Properties of High-Strength Bainitic Steels (베이나이트계 고강도강의 합금원소와 냉각조건이 미세조직, 인장성질, 충격성질에 미치는 영향)

  • Sung, Hyo Kyung;Shin, Sang Yong;Hwang, Byoungchul;Lee, Chang Gil;Kim, Nack J.;Lee, Sunghak
    • Korean Journal of Metals and Materials
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    • v.48 no.9
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    • pp.798-806
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    • 2010
  • The effects of alloying elements and the cooling condition on the microstructure, tensile properties, and Charpy impact properties of high-strength bainitic steel plates fabricated by a controlled rolling process were investigated in the present study. Eight kinds of steel plates were fabricated by varying C, Cr, and Nb additions under two different cooling rates, and their microstructures and tensile and Charpy impact properties were evaluated. The microstructures present in the steels increased in the order of granular bainite, acicular ferrite, bainitic ferrite, and martensite as the carbon equivalent or cooling rate increased, which resulted in a decrease in the ductility and Charpy absorbed energy. The steels containing a considerable amount of bainitic ferrite or martensite showed very high strengths, together with good ductility and Charpy absorbed energy. In order to achieve the best combination of strength, ductility, and Charpy absorbed energy, granular bainite and acicular ferrite were properly included in the high-strength bainitic steels by controlling the carbon equivalent and cooling rate, while about 50 vol.% of bainitic ferrite or martensite was maintained to maintain the high strength.

Dynamic Fracture Properties of Nylon Thermoplastic Material Depending on Notch Angle with Charpy Impact Machine and Finite Element Method (유한요소법과 샤피충격시험기에 의한 노치각도에 따른 나일론 열가소성 플라스틱 재료의 파괴특성)

  • Park, Myung-Kyun;Lee, Jung-Won;Kim, Tae-Ok
    • Journal of the Korean Institute of Gas
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    • v.12 no.1
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    • pp.1-6
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    • 2008
  • The notched Charpy impact test is one of the most prevalent techniques used to characterize the effect of high impulse loads on polymeric materials. In this study, a method of analysis in nylon plastic materials is suggested to evaluate the critical strain energy release rate for variation of notch angles from the Charpy impact energy measurement. Instrumented Charpy impact tester was used to extract ancillary information concerning fracture parameters in addition to total fracture properties and maximum critical load. The dynamic stress intensity factor of nylon plastic material was calculated for the ASTM Charpy specimen from the obtained maximum critical load. Also, the finite element model was developed to figure out the stress distributions for Charpy specimen with different notch angles subject to 3 point bending load which is equivalent to the load applied in the experiment.

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Effect of Rolling Conditions on Microstructure and Mechanical Properties of Thick Steel Plates for Offshore Platforms (해양플랜트용 후판강의 미세조직과 기계적 특성에 미치는 압연 조건의 영향)

  • Kim, Jongchul;Suh, Yonhchan;Hwang, Sungdoo;Shin, Sang Yong
    • Korean Journal of Materials Research
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    • v.28 no.8
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    • pp.478-488
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    • 2018
  • In this study, three kinds of steels are manufactured by varying the rolling conditions, and their microstructures are analyzed. Tensile and Charpy impact tests are performed at room temperature to investigate the correlation between microstructure and mechanical properties. In addition, heat affected zone(HAZ) specimens are fabricated through the simulation of the welding process, and the HAZ microstructure is analyzed. The Charpy impact test of the HAZ specimens is performed at $-40^{\circ}C$ to investigate the low temperature HAZ toughness. The main microstructures of steels are quasi-polygonal ferrite and pearlite with fine grains. Because coarse granular bainite forms with an increasing finish rolling temperature, the strength decreases and elongation increases. In the steel with the lowest reduction ratio, coarse granular bainite forms. In the HAZ specimens, fine acicular ferrites are the main features of the microstructure. The volume fraction of coarse bainitic ferrite and granular bainite increases with an increasing finish rolling temperature. The Charpy impact energy at $-40^{\circ}C$ decreases with an increasing volume fraction of bainitic ferrite and granular bainite. In the HAZ specimen with the lowest reduction ratio, coarse bainitic ferrite and granular bainite forms and the Charpy impact energy at $-40^{\circ}C$ is the lowest.

Correlation Study of Microstructure and Mechanical Properties in Heat Affected Zones of API X80 Pipeline Steels containing Complex Oxides (복합산화물이 형성된 API X80 라인파이프강의 용접열영향부 미세조직과 기계적 특성의 상관관계 연구)

  • Shin, Sang Yong;Oh, Kyoungsik;Lee, Sunghak
    • Korean Journal of Metals and Materials
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    • v.47 no.2
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    • pp.59-70
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    • 2009
  • This study is concerned with the correlation between microstructure and mechanical properties in heat affected zones (HAZs) of API X80 pipeline steels containing complex oxides. Three kinds of specimens were fabricated by varying alloying elements of Ti, Al, and Mg to form complex oxides, and their microstructures, Vickers hardness, Charpy impact properties were investigated. The number of complex oxides increased as the excess amount of Ti, Al, and Mg was included in the steels. The simulated HAZs containing a number of oxides showed a high volume fraction of acicular ferrite region because oxides acted as nucleation sites for acicular ferrite. According to the correlation study between thermal input, volume fraction of acicular ferrite region, and Charpy impact properties, the ductile fracture occurred predominantly when the volume fraction of acicular ferrite region was 65% or higher, and the Charpy absorbed energy was excellent over 200 J. When the volume fraction of acicular ferrite region was 35% or lower, the Charpy absorbed energy was poor below 50 J as the brittle cleavage fracture occurred. These findings suggested that the active nucleation of acicular ferrite in the oxide-containing steel HAZs was associated with the great improvement of Charpy impact properties of the HAZs.

Effect of Carbon and Nickel on Microstructure and Low Temperature Charpy Impact Properties of HSLA Steels (HSLA 강의 미세조직과 저온 샤르피 충격 특성에 미치는 탄소와 니켈의 영향)

  • Eom, Haewon;Cho, Sung Kyu;Cho, Young Wook;Shin, Gunchul;Kwon, Yongjai;Lee, Jung Gu;Shin, Sang Yong
    • Korean Journal of Materials Research
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    • v.30 no.4
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    • pp.184-196
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    • 2020
  • In this study, effects of carbon and nickel on microstructure and low temperature Charpy impact properties of HSLA (high strength low alloy) steels are investigated. To understand the complex phase transformation behavior of HSLA steels with high strength and toughness before and after welding processes, three kinds of HSLA steels are fabricated by varying the carbon and nickel content. Microstructure analysis, low temperature Charpy impact test, and Vickers hardness test are performed for the base metals and CGHAZ (coarse-grain heat affected zone) specimens. The specimens with the lowest carbon and nickel content have the highest volume fraction of AF, the lowest volume fraction of GB, and the smallest GB packet size. So, the low temperature Charpy absorbed energy of the CGHAZ specimen is the highest. The specimens with increased carbon and nickel content have the lowest volume fraction of AF, the highest volume fraction of GB, and the largest GB packet size. So, the low temperature Charpy absorbed energy of the CGHAZ specimen is the lowest.

Correlation between Microstructure and Charpy Impact Properties of FCAW HAZ of Thick Steel Plates for Offshore Platforms (해양플랜트용 후판강의 FCAW HAZ 미세조직과 샤르피 충격 특성의 상관관계)

  • Lee, Hun;Lee, Hyunwook;Cho, Sung Kyu;Choi, Dongki;Kim, Hyoung Chan;Kwon, Yongjai;Lee, Jung Gu;Shin, Sang Yong
    • Korean Journal of Materials Research
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    • v.29 no.8
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    • pp.497-504
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    • 2019
  • In this study, the correlation between microstructure and Charpy impact properties of FCAW(Flux cored arc welding) HAZ(Heat affected zone) of thick steel plates for offshore platforms was investigated. The 1/4 thickness(1/4t) location HAZ specimen had a higher volume fraction of bainite and finer grain size of acicular ferrite than those of the 1/2 thickness (1/2t) location HAZ specimen because of the post heat effect during the continuous FCAW process. The Charpy impact energy at $-20^{\circ}C$ of the 1/4t location HAZ specimen was lower than that of the 1/2t location HAZ specimen because of the high volume fraction of coarse bainite. The Charpy impact energy at -40 and $-60^{\circ}C$ of the 1/2t location HAZ specimen were higher than those of the 1/2t location HAZ specimen because the ductile fracture occurred in the fine acicular ferrite and martensite regions. In the ductile fracture mode, the deformed regions were observed in fine acicular ferrite and martensite regions. In the brittle fracture mode, long crack propagation path was observed in bainite regions.

Instrumented Impact Test using Subsize Charpy Specimen for Evaluating Impact Fracture Behavior in Bulk Amorphous Metals (벌크 아몰퍼스 금속의 충격파괴 거동 평가를 위한 미소 샬피 시험편을 사용한 계장화 충격 시험법)

  • Shin, Hyung-Seop;Ko, Dong-Kyun;Jung, Young-Jin;Oh, Sang-Yeob;Kim, Moon-Saeng
    • Proceedings of the KSME Conference
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    • pp.101-106
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    • 2003
  • In order to investigate the mechanical behavior of newly developed materials, the evaluation of mechanical properties using small-size specimen is essential. For those purposes, an instrumented impact testing apparatus, which provides the load-displacement curve under impact loading without oscillations, was devised. To develop the test procedure with the setup, the impact behaviors of various kinds of structural materials such as S45C, SCM4, Ti alloys (Ti-6V-4Al) and Zr-based bulk amorphous metal, were investigated through the instrumented Charpy V-notch impact tests. The calibrations of the dynamic load and displacement that was calculated based on the Newton' second law were carried out through the quasi-static load test and the comparison of a directly measured value using a laser displacement meter. Satisfactory results could be obtained. The crack initiation and propagation processes during impact fracture could be well divided on the curve, depending on the intrinsic characteristic of specimen tested; ductile or brittle. The absorbed impact energy in Zr-basd BAM was largely used for crack initiation not for crack propagation process. The fracture surfaces under impact loading showed different feature when compared with the static cases.

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