• Title/Summary/Keyword: Residual Stress Characteristics

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A Study on the Influence of the Inclined Angle and Depth of the Substrate on Thermal and Residual Stress Characteristics in the Vicinity of the Repaired Region by a Directed Energy Deposition Process (기저부 경사각과 깊이가 에너지 제어형 용착 공정으로 보수된 영역의 열 및 잔류응력 특성에 미치는 영향 고찰)

  • Kim, Dan-A;Lee, Kwang-Kyu;Ahn, Dong-Gyu
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.21 no.6
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    • pp.50-59
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    • 2022
  • The design of the substrate significantly affects the thermal history and the residual stress formation in the vicinity of a repaired region by a directed energy deposition (DED) process. The occurrence of defects in the repaired region depends on the thermal history and residual stress formation. The objective of this study was to investigate the influence of the inclined angle and depth of the substrate on the thermal and residual stress characteristics in the vicinity of a repaired region by a DED process through two-dimensional finite element analyses (FEAs). The temperature and residual stress distributions in the vicinity of the repaired region were predicted according to the combination of the inclined angle and depth of the substrate. The effects of the inclined angle and depth on the depth of the heat affected zone and the maximum value of the residual stress were examined. A proper combination of the inclined angle and depth of the substrate was estimated to decrease the residual stress in the vicinity of the repaired region.

A Study on Residual Stress Characteristics for Joint of Rock in Ring Shear Tests (링 전단시험기를 이용한 암석절리의 잔류강도 특성에 관한 연구)

  • 권준욱;김선명;윤지선
    • Journal of the Korean Geotechnical Society
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    • v.16 no.6
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    • pp.35-41
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    • 2000
  • Residual stress is defined as a minimum stress with a large displacement of specimens and the residual stress after peak shear stress appears with displacement volume but there is no provision to select the residual stress. In the previous study, residual stress was recorded when the change of shear load is small in the condition of the strain more than 15%. But, in this study, hyperbolic function((No Abstract.see full/text), b=experimental constant) of soil test is adapted to joint of rock and the propriety is investigated. In a landslide and landsliding of artificial slope, wedge failure of tunnel with a large displacement, tests are simulated from peak stress to residual stress for safety analysis. But now. direct shear stress and triaxial compressive tests are usually performed to find out characteristics of shear stress about joint. Although these tests get a small displacement, that data of peak stress and residual stress are used for safety analysis. In this study, we tried to determine failure criteria for joints of rock using ring shear test machine. The residual stress following shear behavior was determined by the result of ring shear test and direct shear test. In conclusion, after comparing the results of the two test, we found that cohesion(c) and internal friction angle(ø) of ring shear test are 30% and 22% respectively of those of the direct shear test.

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A Study on Residual Stress Characteristics for Joint of Soft Rock in Ring Shear Tests (링 전단시험기를 이용한 연암의 절리에 대한 잔류강도 특성에 관한 연구)

  • 권준욱;김선명;윤지선
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.03b
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    • pp.281-288
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    • 2000
  • In this study, we tried to determine failure criteria for joints of soft rock using ring shear test machine. The residual stress fellowing shear behavior was determined by the result of ring shear test and direct shear test. Ring shear test with the specimens which cover a large deformation range was adapted to measure a residual stress, and was possible to present the peak stress to present the peak stress to the residual stress at the same time. Residual stress is defined a minimal stress of specimens with a large displacement and the result of the peak residual stress is shown by a size of displacement volume. Therefore, the residual stress in soil was decided by shear stress of maximum shear stress - shear displacement(angle) based on the test result of a hyperbolic function ((equation omitted), a, b = experimental constant). In this study, it was proved that the residual stress of rock joint can be determined by using of this method.

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3-D Characteristics of the Residual Stress in the Plate Butt Weld Between SA508 and F316L SS (SA508/ F316L SS 맞대기 용접 판재의 3차원 잔류응력특성)

  • Lee, Kyoung-Soo;Kim, Tae-Ryong;Park, Jai-Hak;Kim, Man-Won;Cho, Seon-Yeong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.4
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    • pp.401-408
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    • 2009
  • This study is performed to check the three dimensional characteristics of residual stress in the dissimilar metal weld. Although two dimensional analysis has been widely used for the assessment of weld residual stress, it has limitations to understand the stress distribution of the third direction. 3-D analysis was done to understand residual stress distribution of the welded plate. A simple butt-welded plate was considered to show the stress variation on all direction. A mock-up plate weldment was fabricated with SA-508 and F316L, which are widely used in nuclear power plants. The analysis results were validated with the measured values in the mock-up.

A study on the fatigue crack growth behavior of aluminum alloy weldments in welding residual stress fields (용접잔류응력장 중에서의 Aluminum-Alloy용접재료의 피로균열성장거동 연구)

  • 최용식;정영석
    • Journal of Welding and Joining
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    • v.7 no.1
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    • pp.28-35
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    • 1989
  • The fatigue crack growth behavior in GTA butt welded joints of Al-Alloy 5052-H38 was examined using Single Edge Notched(SEN) specimens. It is well known that welding residual stress has marked influence on fatigue crack growth rate in welded structure. In the general area of fatigue crack growth in the presence of residual stress, it is noted that the correction of stress intensity factor (K) to account for residual stress is important for the determination of both stress intensity factor range(.DELTA.K) and stress ratio(R) during a loading cycle. The crack growth rate(da/dN) in welded joints were correlated with the effective stress intensity factor range(.DELTA.Keff) which was estimated by superposition of the respective stress intensity factors for the residual stress field and for the applied stress. However, redistribution of residual stress occurs during crack growth and its effect is not negligible. In this study, fatigue crack growth characteristics of the welded joints were examined by using superposition of redistributed residual stress and discussed in comparison with the results of the initial welding residual stress superposition.

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Characteristics in W-EDM of Tungsten Carbide (초경합금의 와이어 방전가공에 의한 특성)

  • 맹민재
    • Journal of the Korean Society of Safety
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    • v.16 no.4
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    • pp.7-13
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    • 2001
  • Wire electrical discharge machining experiments in conducted to investigate characteristics of acoustic emission (AE) and electrical discharge energy due to current peak (I$_{p}$), pulse on time($\tau$/on/). The AE signals are obtained with a sensor attached to workpiece side. Machining states are identified with scanning electron microscopy and residual stress analyzer. It is demonstrated that the residual stress provide reliable informations about the machining states. Moreover, machining states can be detected successfully using both the residual stress and AE count rate.e.

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Effect of Residual Stress on Fatigue Characteristics at the Welds of Stainless Steel (스테인리스강 용접부의 잔류응력이 피로특성에 미치는 영향)

  • 권종완;양현태
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.10 no.5
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    • pp.110-117
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    • 2001
  • In the weldments, the crack propagation rate is changed due to the residual stress. The crack propagation rate is high in the region with the residual stress. However it shows the same behavior with the base metal in the region that does not include the residual stress. The fatigue crack growth rate for the material with residual stresses can be predicted more precisely by using the effective stress ratio. The difference between experimental results and prediction results seems to be due to the redistribution of the residual stresses and microstructural change.

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Corrosion Fatigue Characteristics of SUS316L Steel with Ti Undercoat using Plasma Spray Method (플라즈마 스프레이방법을 이용하여 Ti 언더코트를 제작한 SUS316L강의 부식피로 특성)

  • Han, Chang-Suk;Kim, Woo-Suk
    • Korean Journal of Materials Research
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    • v.31 no.3
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    • pp.172-180
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    • 2021
  • In this study, using the plasma spray method, tensile and compression fatigue tests are performed in saline solution to examine the effect of Ti undercoat on corrosion fatigue behavior of alumina-coated specimens. The alumina-coated material using Ti in the undercoat shows better corrosion fatigue strength than the base material in the entire stress amplitude range. Fatigue cracking of UT specimens occurs in the recess formed by grit-blasting treatment and progresses toward the base metal. Subsequently, the undercoat is destroyed at a stage where the deformation of the undercoat cannot follow the crack opening displacement. The residual stress of the UT specimen has a tensile residual stress up to about 100 ㎛ below the surface of the base material; however, when the depth exceeds 100 ㎛, the residual stress becomes a compressive residual stress. In addition, the inside of the spray coating film is compressive residual stress, which contributes to improving the fatigue strength characteristics. A hardened layer due to grit-blasting treatment is formed near the surface of the UT specimen, contributing to the improvement of the fatigue strength characteristics. Since the natural potential of Ti spray coating film is slightly higher than that of the base material, it exhibits excellent corrosion resistance; however, when physiological saline intrudes, a galvanic battery is formed and the base material corrodes preferentially.

Evaluation of Welding Residual Stress Characteristics of a Surge Line Elbow (밀림곡관 맞대기 용접부의 잔류응력 특성 평가)

  • Han, Chang-Gi;Chang, Yoon-Suk;Kim, Maan-Won;Lee, Kyoung-Soo
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.11 no.1
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    • pp.45-52
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    • 2015
  • Even though a lot of efforts have been devoted to evaluate welding residual stress characteristics of nuclear components, from the view point of accuracy, there are still some arguments in application of engineering estimation schemes. In this paper, three-dimensional finite element analyses (FEA) were carried out to predict residual stress distributions in butt welds of a typical surge line piping. Mesh optimization was conducted and subsequent analysis results such as the axial and hoop stress components along the weld center line and inner wall. Moreover, alternative evaluation was conducted by using three representative equations and their results were compared to those of FEA. Thereby, key parameters affecting to temperature profiles and residual stress distributions were derived as well as an optimum engineering estimation scheme was recommended.

A Study on the Analysis for Welding Residual Stress of Preflex Beam (PREFLEX BEAM 제작시의 용접부 역학적 특성에 관한 연구)

  • 방한서;주성민;안해영
    • Journal of Ocean Engineering and Technology
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    • v.17 no.6
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    • pp.65-71
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    • 2003
  • Since the preflex beam is fabricated through welding, the pre-compressive stresses that should occur over the concrete pier are diminished by the welding residual stresses. Therefore welding residual stresses must be relieved during the fabrication. Therefore, the analysis and examination of the accurate welding residual stress distribution characteristics are necessary. In this study, accurate distribution of welding residual stress of the preflex beam is analyzed by the finite element method, using 2 dimensional and 3 dimensional elements. Further, the thermo-mechanical behavior of the preflex beam is also studied. After the finite element analysis, real distribution of welding residual stress is measured using the sectioning method, and then is compared with the simulation results. The distribution of welding residual stress by finite analysis agreed well with the experimental results.