• 제목/요약/키워드: Peening

검색결과 261건 처리시간 0.027초

쇼트피닝이 회주철의 캐비테이션 침식 저항성에 미치는 영향 (Influence of Shot Peening on Cavitation Erosion Resistance of Gray Cast Iron)

  • 박일초
    • Corrosion Science and Technology
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    • 제20권3호
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    • pp.143-151
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    • 2021
  • In this study, optimal shot peening process conditions were investigated for improving the cavitation erosion resistance of gray cast iron under a marine environment. Shot peening was performed with variables of injection pressure and injection time. The durability was then evaluated through cavitation erosion test which was conducted according to the modified ASTM G-32 standard. The tendency of cavitation erosion damage according to shot peening process condition was investigated through weight loss rate, surface and cross-sectional analysis of the specimen before and after the test. As a result, the shot peening process condition that could minimize cavitation erosion was when the injection pressure was the lowest and when the injection time was the shortest. This was because the flake graphite exposed on the gray cast iron surface could be easily removed under such condition. Therefore, the notch effect can be prevented by surface modification. In addition, the cavitation erosion damage mechanism of gray cast iron was discussed in detail.

SUP7-50CrV4강의 피로강도에 미치는 압축잔류응력의 영향 (The effect of compress residual stresses for fatigue strength of SUP7-50CrV4 Steel)

  • 박경동;정찬기
    • 한국해양공학회:학술대회논문집
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    • 한국해양공학회 2001년도 추계학술대회 논문집
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    • pp.247-252
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    • 2001
  • Recently the steel parts used at automobiles are required to be used under high stress more than ever before in need of the weight down. To achieve this requirement of a high strength steel, it must be necessary to decrease inclusion content and surface defect as like decarburization, surface roughness etc.. In this study, the surface conditions are measured to know the influence on fatigue properties by two cases of shot peening of two-stage shot peening and single-stage shot peening. And for this study, two kinds of spring steel (SUP7, 50CrV4) are used. This study shows the outstanding improvement of fatigue properties at the case of two-stage shot peening in the rotary bending fatigue test and this is assumed to be from on low stress condition, the 1st stage shot peening is not affected by nonmetallic inclusion under metal. it is possible that the 2nd stage shot peening increases the fatigue life and the high stress but that is affected by nonmetallic inclusion under metal. so far beeasily 50CrV4 have made high stress. But, results also show fatigue failures originated at inclusion near surface, and this inclusion type is turned out to be a alumina of high hardness.

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DIN50CrV4-SAE9254강의 피로강도에 미치는 압축잔류응력의 영향 (The Effect of Compressive Residual Stresses on Fatigue Strength in DIN50CrV4-SAE9254 Steel)

  • 박경동;정찬기
    • 한국해양공학회지
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    • 제15권3호
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    • pp.93-99
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    • 2001
  • Recently the steel parts used at automobils are required to be used under high stress more than ever before in need of the weight down. To achieve this requirement of a high strength steel, it must be necessary to decrease inclusion content and surface defect as like decarburization, surface roughness etc.. In this study, the surface conditions are measured to know the influence on fatigue properties by two cases of shot peening of two-stage shot peening and single-stage shot peening. And for this study, two kinds of spring steel (SAE 9254, DIN50CrV4) are used. This study shows the outstanding improvement of fatigue properties at the case of two-stage shot peening in the rotary bending fatigue test and this is assumed to be from (1) on low stress condition, th 1st stage shot peening is not affected by nonmetallic inclusion under metal.(2) it is possible that the 2nd stage shot peening increases the fatigue life and the high stress but that is affected by nonmetallic inclusion under metal. (3) so far beeasily DIN50CrV4 have made high stress. But, results also show fatigue failures originated at inclusion near surface, and this inclusion type is turned out to be a alumina of high hardness.

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레이저 피닝 처리 및 적용 기술 (Laser Peening Process and Its Application Technique)

  • 김종도;무네하루 쿠쯔나;유지 사노
    • Journal of Welding and Joining
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    • 제33권4호
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    • pp.1-6
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    • 2015
  • Advances in laser technology have yielded a multitude of innovative processes and applications in various industries. Laser peening is a typical example invented in the mid-1990s as a surface technology, which converted residual stress from tension to compression by just irradiating successive laser pulses to metallic materials under aqueous environment without any surface preparation. The effects of laser peening have been experimentally studied on residual stress, stress corrosion cracking(SCC) susceptibility and fatigue properties with water-penetrable frequency-doubled Nd:YAG laser. In addition, laser peening has been widely used in aviation and aerospace industries, automobile manufacturing and nuclear plant. One of the most important causes to improve the above-mentioned properties is the deeper compressive residual stress induced by laser peening. Taking advantage of the process without reacting force against laser irradiation, a remote operating system was developed to apply laser peening to nuclear power reactors as a preventive maintenance measure against SCC.

동합금의 워터캐비테이션피닝에 의한 내구성과 부식특성 평가 (Evaluation of Corrosion and the Anti-Cavitation Characteristics of Cu Alloy by Water Cavitation Peening)

  • 김성종;한민수;김민성
    • Corrosion Science and Technology
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    • 제11권5호
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    • pp.184-190
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    • 2012
  • Cu alloy is widely used for marine applications due to its excellent ductility and high resistance for corrosion as wells as cavitation. However, long term exposure of the material to marine environments may result in damages caused by cavitation and corrosion. Water cavitation peening has been introduced in order to improve resistance of Cu alloy to corrosion and cavitation. The technology induces compressive residual stress onto the surface, and thus enhances the fatigue strength and life. In this study, the characteristics of the material were investigated by using water cavitaiton peening technique, and results showed that 2 minutes of water cavitation peening indicated the considerable improvement in hardness. On the other hand, over 10 minutes of water cavitation peening accelerated damages to the surface. In the case of ALBC3, water cavitation peening in the range of 2 to 10 minutes has shown the excellent durability and corrosion resistance while minimizing surface damages.

SUP7 및 SAE9254강의 피로강도에 미치는 압축잔류응력의 영향 (The effect of compress residual stresses of shot peening for fatigue strength of SUP7 and SAE9254 steel)

  • 박경동;정찬기
    • 동력기계공학회지
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    • 제5권4호
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    • pp.67-73
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    • 2001
  • Recently the steel parts used at automobiles are required to be used under high stress more than ever before in need of the weight down. To achieve this requirement of a high strength steel, it must be necessary to decrease inclusion content and surface defect as like decarburization, surface roughness etc.. In this study, the surface conditions are measured to know the influence on fatigue properties by two cases of two-stage shot peening iud single-stage shot peening for two kinds of spring steel(SUP7, SAE9254). This study shows the outstanding improvement of fatigue properties at the case of two-stage shot peening in the rotary bending fatigue test and this is assumed to be from decreasing the surface roughness unchanging the surface hardness increasing the compressive residual stress. Results also show fatigue failures originated at inclusion near surface, and this inclusion type is turned out to be a alumina of high hardness.

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현가장치용 SUP-9강의 피로파괴에 미치는 압축잔류응력의 영향 (The Effect of Compressive Residual Stress on Fatigue Fracture of the Spring steel)

  • 박경동;진영범
    • 한국기계가공학회지
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    • 제3권3호
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    • pp.79-85
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    • 2004
  • The lightness of components required in automobile and machinery industry is requiring high strength of components. In particular, fatigue failure phenomena, which happen in metal, bring on danger in human life and property. Therefore, antifatigue failure technology takes an important part of current industries. Currently, the shot peening is used for removing the defects from the surface of steel and improving the fatigue strength on surface. Therefore, in this paper the effect of compressive residual stress of spring steel(JISG SUP-9)by shot peening on fatigue crack growth characteristics in stress ratio(R=0 1, R=0 3, R=0 6)was investigated considering fracture mechanics. By using the methods mentioned above, I arrived at the following conclusions: (1) The fatigue crack growth rate(da/dN) of the shot peening material was lower than the unpeening material And in stage I, ${\Delta}K_{th}$, the threshold stress intensity factor, of the shot peening material is high in critical parts unlike the unpeening material. (2) Fatigue life shows more Improvement in the shot peening material than in the unpeening material. And compressive residual stress of surface on the shot peening processed operate the resistance of fatigue crack propagation.

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5052-O 알루미늄 합금의 워터 캐비테이션 피닝 시간에 따른 표면 경화와 부식 특성에 관한 연구 (Investigation on surface hardening and corrosion characteristic by water cavitation peening with time for Al 5052-O alloy)

  • 김성종;현광룡
    • Corrosion Science and Technology
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    • 제11권4호
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    • pp.151-156
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    • 2012
  • The cavity formed by the ultrasonic generation in the fluid with the application of water cavitation peening collides into the metal surface. At this time, the surface modification effect such as the work hardening presents by the compressive residual stress formed due to the localized plastic deformation. In this investigation, the water cavitation peening technology in the distilled water with the lapse of time was applied to 5052-O aluminum alloy for aluminum ship of a high value. So, the optimum water cavitation peening time on the effect for surface hardening and anti-corrosion property was investigated. Consequently, the water cavitatin peening time on excellent hardness and corrosion resistance characteristic presented 3.5 min. and 5.0 min, respectively. The surface hardness in the optimum water cavitation peening time was improved approximately 45% compared to the non-WCPed condition. In addition, corrosion current density was decreased.

쇼트피닝 시간에 따른 동합금의 조직특성 및 전기화학적 특성의 변화 (Effects of Shot Peening Time on Microstructure and Electrochemical Characteristics for Cu Alloy)

  • 한민수;현광용;김성종
    • 해양환경안전학회지
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    • 제19권5호
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    • pp.545-551
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    • 2013
  • 본 연구에서는 내식성이 우수한 동합금에 대하여 내구성 향상을 위해 쇼트피닝 시간을 변수로 표면 개질하여 전기화학적 특성과 조직 변화를 관찰하였다. 그 결과 쇼트피닝 후 표면에 전체적으로 요철이 발생하였으며, 시간이 증가할수록 커버리지 향상에 따른 균질화 현상이 관찰되었다. 또한 쇼트피닝된 모든 시험편에서 경도가 향상되었으며, 쇼트피닝 시간이 3.5분일 때 52 %의 경도향상을 나타냈다. 그리고 이때 전기화학적 특성은 쇼트피닝을 실시하지 않은 경우와 유사하였다.

스프링강의 피로크랙진전 특성에 미치는 쇼트피닝 투사속도의 영향 (An Effect of Shot Velocity of Shot-peening on A Property of Growth Behavior of Fatigue Crack for Spring Steel)

  • 박경동;노영석
    • 한국해양공학회:학술대회논문집
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    • 한국해양공학회 2002년도 추계학술대회 논문집
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    • pp.341-346
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    • 2002
  • In this study, an effect that compressive residual stress formed by shot-peening the surface of spring steel(JISG SUP-9) at each shot velocity(1800, 2200, 2600, 3000rpm) on the fatigue crack growth property and threshold stress intensity factor, ${\Delta}K_{th}$, was examined. Followings are the result (1) Compressive residual stress on surface of specimen was determined at each -601 MPa(1800rpm), -638 MPa(2200rpm), -587 MPa (2600rpm), -550 MPa(3000rpm) by shot velocity of shot peening and threshold stress intensity factor, ${\Delta}K_{th}$, fatigue crack growth rate, da/dN, on fatigue crack growth is obstructed by the compressive residual stress was determined at each $5.619\;MPa\sqrt{m}$(Un-peening), $8.319\;MPa\sqrt{m}$(1800rpm), $8.797\;MPa\sqrt{m}$(2200rpm), $7.835\;MPa\sqrt{m}$(2600rpm), $7.352\;MPa\sqrt{m}$(3000rpm) (2) Existing compressive residual stress by effect of shot velocity of shot-peening on relation of crack length. a, and number of cycle, N, was 2 times progressed in case of 2200rpm than specimen of Un-peening on fatigue life. And fatigue life was 1.6 times progressed incase of 3000rpm by Over peening. (3) Fatigue life of Material on Paris' law, $da/dN=C({\Delta}K)^m$, that effect of material constant, C, and fatigue crack growth exponent, m, was influenced by effect of. C and m.

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