• Title/Summary/Keyword: Laser shock peening

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Modeling of a Confinement Effect in Laser Shock Peening on Titanium Alloy (티타늄 합금에 대한 레이저 쇼크 피닝에서 컨파인먼트에 따른 피닝 효과 모델링)

  • Lee, Wooram;Kim, Joohan
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.22 no.4
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    • pp.680-685
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    • 2013
  • In this study, the effect of laser shock peening on a titanium alloy was modeled using different confinements. Both liquid and solid confinement could be applied to laser shock peening, and solid confinement provided a dry laser shock peening process, which has the advantage of a corrosion-free effect. When a different confinement was applied to laser shock peening, a different peening effect would be expected. In our study, the peening effect was numerically modeled and simulated. The main effect of different confinements was a change in the impedances required to confine a shock wave from a plasma. The impedances were assumed with respect to different materials. Johnson-Cook's plastic deformation modeling was applied to the simulation. The strains and residual stresses were calculated to evaluate the confinement effects. When solid confinement was used, the residual stress increased by 60-85%, compared to the case of liquid confinement. However, the depth of the residual stress was slightly deeper. The simulated results could be applied to estimate the peening effect when a different confinement was used in the laser shock peening process.

Improving the Residual Stress Characteristics of the Metal Surface by Nd:YAG Laser Shock Peening (Nd:YAG 레이저 충격 피닝에 의한 금속표면의 잔류응력 특성 개선)

  • Yang, Se-Young;Choi, Seong-Dae;Jun, Jea-Mok;Gong, Byeong-Chae
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.19 no.4
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    • pp.539-547
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    • 2010
  • Laser shock peening is useful to improve fatigue characteristic of multiple number of metals and alloys. This process induces a compressive residual stress on the metal surface, and when tensile load is applied, growth of crack is delayed and which changes the characteristic of the metal surface. It is an innovative surface treatment technique for strengthening metals. Specimens of SM45C are used in this study. The effect of an inertial tamping layer on the residual stress field using laser shock peening setup and Nd:YAG laser power is evaluated. Residual stress distribution measured by X-ray diffraction. As a result of this study it can be presented that following condition of Nd:YAG laser power and inertial tamping layer parameters, compressive residual stress is generated on the surface of the SM45C. Results to experimental data indicate that laser shock peening has great potential as a means of improving the mechanical performance of the metal surface.

Analysis of the Square Beam Energy Efficiency of a Homogenizer Near the Target for Laser Shock Peening

  • Kim, Taeshin;Hwang, Seungjin;Hong, Kyung Hee;Yu, Tae Jun
    • Journal of the Optical Society of Korea
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    • v.20 no.3
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    • pp.407-412
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    • 2016
  • We analyzed through numerical simulations the properties of a square beam homogenizer near the target for laser shock peening. The efficiency was calculated near the target by considering the plasma threshold of the metals. We defined the depth of focus of the square beam homogenizer with a given efficiency near the target. Then, we found the relationship between the depth of focus for the laser shock peening and four main parameters of the square beam homogenizer: the plasma threshold of the metal, the number of lenslets in the array-lens, the focal length of the condenser lens and the input beam size.

Numerical Analysis of Working Distance of Square-shaped Beam Homogenizer for Laser Shock Peening

  • Kim, Taeshin;Hwang, Seungjin;Hong, Kyung Hee;Yu, Tae Jun
    • Current Optics and Photonics
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    • v.1 no.3
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    • pp.221-227
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    • 2017
  • To apply a square-shaped beam homogenizer to laser shock peening, it should be designed with a long working distance and by considering metal targets with various shapes and textures. For long working distances, a square-shaped beam homogenizer with a long depth of focus is required. In the range of working distance, the laser beam is required to have not only high efficiency but high uniformity, in other words, a good peening quality is guaranteed. In this study, we defined this range as the working distance for laser shock peening. We have simulated the effect of some parameters on the working distance. The parameters include the focal length of the condenser lens, pitch size of the array lens, and plasma threshold of the metal. The simulation was performed through numerical analysis by considering the diffraction effect.

Micro-Shockwave Measurement and Evaluation of Laser Shock Peening (레이저 쇼크 피닝의 마이크로 충격파 측정 및 평가)

  • Kim, Joo-Han;Lee, Woo-Ram;Kim, Teak-Gu;Cheong, Seong-Kyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.10
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    • pp.1041-1046
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    • 2011
  • Micro shockwaves are induced in laser shock peening and their effect on metal samples is presented. Laser shock peening produces maximized internal compressive stress on metal surfaces. This research evaluated the effects of micro shockwaves from laser shock peening with a pulsed Nd:YAG laser on steel samples, through the analysis of the mechanical properties of the samples. In the experiments, a piezo material was applied to measure the micro shockwaves and the hardnesses and micro tensile strengths of the samples were evaluated.

Improvement of Surface Hardness of 2205 Duplex Stainless Steel by Laser Shock Peening and Observations of Surface Changes (레이저 쇼크 피닝에 의한 2205 듀플렉스 스테인리스강의 표면 경도 향상과 표면 변화 관찰)

  • Lim, H.T.;Jeong, H.M.;Kim, P.K.;Jeong, Sung-Ho
    • Laser Solutions
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    • v.14 no.1
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    • pp.19-24
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    • 2011
  • This work reports the results for laser shock peening of duplex stainless steel (22% Chromium - 5% Nickel) using a pulsed Nd:YAG laser (wavelength = 532nm, pulse width = 8ns). for the application to high-capacity pumps for seawater desalination plants. By properly selecting the process parameters such as laser intensity of 10GW/$cm^2$, laser pulse density of 75pulse/$mm^2$, and $100{\mu}m$ thick aluminum foil as an absorbent coating layer, the surface hardness of duplex stainless steel could be enhanced by 26%, from 256HV to 323HV with little changes in surface morphology and roughness. The depth of laser shock peened layer was measured to be around 2mm. The large enhancement of surface hardness is considered to have high practical importance in minimizing abrasive and corrosive deterioration of pump parts.

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Study on a Residual Stress Reduce in Laser Welding Process using Ti6Al4V (티타늄 합금의 레이저 용접 공정 시 잔류 응력 저감 방안에 대한 연구)

  • Lee, Wooram;Park, Taesung;Park, Ikkeun
    • Journal of Welding and Joining
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    • v.34 no.6
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    • pp.35-41
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    • 2016
  • The experimental study has been performed through residual stress using the Ti6Al4V, investigate the effect of laser shock peening on laser welding process residual stress of Ti6Al4V welds in a reduce safety weld zone. This research evaluated the effects of shock waves from laser shock peening with a pulsed Nd:YAG laser on Ti6Al4V welding specimens, through the analysis of the residual stress of the specimens. The residual stress could be formed by the depth of 1 mm if the proposed method of reducing the residual stress is performed in the optimal condition. The welded structures and products during the production process increase the mechanical property of repeated stress, which could be expected to extend the fatigue life of the structure.

Effects of Laser Source Geometry on Laser Shock Peening Residual Stress (레이저 광원 형상이 레이저 충격 피닝 잔류응력에 미치는 영향)

  • Kim, Ju-Hee;Kim, Yun-Jae;Kim, Joung-Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.6
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    • pp.609-615
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    • 2012
  • In LSP (laser shock peening) treatment, the laser source geometries when the laser beam strikes the metal target area are diverse. The laser spot geometry affects the residual stress field beneath the treated surface of the metallic materials, which determines the characteristics of the pressure pulse. In this paper, detailed finite-element (FE) simulations on laser shock peening have been conducted in order to predict the magnitude and of the residual stresses and the depth affected in Inconel alloy 600 steel. The residual stress results are compared for circular, rectangular, and elliptical laser spot geometries. It is found that a circular spot can produce the maximum compressive residual stresses near the surface but generates tensile residual stresses at the center of the laser spot. In the depth direction, an elliptical laser spot produces the maximum compressive residual stresses. Circular and elliptical spots plastically affect the alloy to higher depths than a rectangular spot.

Residual Stress Prediction in LSP Surface Treatment by Using FEM (유한요소법을 이용한 LSP 표면처리 공정의 잔류응력 예측)

  • Bang, Boo-Woon;Son, Seung-Kil;Kim, Jae-Min;Cho, Chong-Du
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.8
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    • pp.767-772
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    • 2009
  • Laser shock peening(LSP) is proving to be better surface treatment than conventional one such as shot peening. The LSP process has a compressive residual stress into a metal alloy and a significant improvement in fatigue life. Our research is focused on applying finite element method to the prediction of residual stress through the LSP processing in some LSP conditions such as pressure and spot size induced by laser. Two analysis methods are considered to calculating the compressive residual stress. But the explicit solution and the static one after partially explicit solving are almost same. In LSP, because of very high strain rate($10^6s^{-1}$), HEL(Hugoniot Elastic Limit) is the most important parameter in material behavior modeling. As the circular laser spot is considered, 2-D axisymmetric elements are used and the infinite elements are applied to boundaries for no reflection. The relations of material properties and the LSP are also important parts in this study.

Effect of Laser Shock Peening Simulation Parameters on Residual Stress of Inconel Alloy 600 Steel (LSP 시뮬레이션 변수가 Inconel 600 합금의 잔류응력에 미치는 영향)

  • Kim, Ju-Hee;Kim, Yun-Jae;Kim, Joung-Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.1
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    • pp.43-50
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    • 2012
  • The effects of parameters related to the finite element simulation of the laser shock peening(LSP) process on the residual stresses of Inconel alloy 600 steel are discussed. In particular, we focus on the maximum pressure, pressure pulse duration, laser spot size, and number of shots. It is found that certain ranges of the maximum pressure and pulse duration can produce the maximum compressive residual stresses near the surface, and thus proper choices of these parameters are important. The residual stresses are not affected by the laser spot size, provided it is larger than a certain size. The magnitudes of the compressive residual stresses and the plastically affected depths are found to increase with an increasing number of shots, but this effect is less pronounced for more shots.