scholarly journals Effects of Laser Peening with a Pulse Energy of 1.7 mJ on the Residual Stress and Fatigue Properties of A7075 Aluminum Alloy

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1716
Author(s):  
Yuji Sano ◽  
Kiyotaka Masaki ◽  
Yoshio Mizuta ◽  
Satoshi Tamaki ◽  
Tomonao Hosokai ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Pulse Energy ◽  
Laser Pulses ◽  
Microchip Laser ◽  
Fatigue Properties ◽  
Laser Peening ◽  
Robot Arm ◽  
X Ray Diffraction ◽  
Bending Fatigue ◽  
Laser Peening Without Coating

Laser peening without coating (LPwC) using a palmtop-sized microchip laser has improved the residual stresses (RSs) and fatigue properties of A7075 aluminum alloy. Laser pulses with a wavelength of 1.06 μm and duration of 1.3 ns from a Q-switched Nd:YAG microchip laser were focused onto A7075 aluminum alloy samples covered with water. X-ray diffraction revealed compressive RSs on the surface after irradiation using laser pulses with an energy of 1.7 mJ, spot diameter of 0.3 mm, and density of 100–1600 pulse/mm2. The effects were evident to depths of a few hundred micrometers and the maximum compressive RS was close to the yield strength. Rotation-bending fatigue experiments revealed that LPwC with a pulse energy of 1.7 mJ significantly prolonged the fatigue life and increased the fatigue strength by about 100 MPa with 107 fatigue cycles. The microchip laser used in this study is small enough to fit in the hand or be mounted on a robot arm. The results may lead to the development of tools that extend the service life of various metal parts and structures, especially outdoors where conventional lasers are difficult to apply.

scholarly journals Quarter Century Development of Laser Peening without Coating

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 152 ◽  
Author(s):  
Yuji Sano
Keyword(s):  
Pulse Energy ◽  
Nuclear Power ◽  
Surface Preparation ◽  
Laser Pulses ◽  
Intense Laser ◽  
Fatigue Properties ◽  
Laser Peening ◽  
Quarter Century ◽  
Pulse Density ◽  
Laser Peening Without Coating

This article summarizes the development of laser peening without coating (LPwC) during the recent quarter century. In the mid-1990s, the study of LPwC was initiated in Japan. The objective at that time was to mitigate stress corrosion cracking (SCC) of structural components in operating nuclear power reactors (NPRs) by inducing compressive residual stresses (RSs) on the surface of susceptible components. Since the components in NPRs are radioactive and cooled underwater, full-remote operation must be attained by using lasers of water-penetrable wavelength without any surface preparation. Compressive RS was obtained on the top-surface by reducing pulse energy less than 300 mJ and pulse duration less than 10 ns, and increasing pulse density (number of pulses irradiated on unit area). Since 1999, LPwC has been applied in NPRs as preventive maintenance against SCC using frequency-doubled Q-switched Nd:YAG lasers (λ = 532 nm). To extend the applicability, fiber-delivery of intense laser pulses was developed in parallel and has been used in NPRs since 2002. Early first decade of the 2000s, the effect extending fatigue life was demonstrated even if LPwC increased surface roughness of the components. Several years ago, it was confirmed that 10 to 20 mJ pulse energy is enough to enhance fatigue properties of weld joints of a structural steel. Considering such advances, the development of 20 mJ-class palmtop-sized handheld lasers was initiated in 2014 in a five-year national program, ImPACT under the cabinet office of the Japanese government. Such efforts would pave further applications of LPwC, for example maintenance of infrastructure in the field, beyond the horizons of the present laser systems.

scholarly journals A Mechanism for Inducing Compressive Residual Stresses on a Surface by Laser Peening without Coating

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 816 ◽  
Author(s):  
Yuji Sano ◽  
Koichi Akita ◽  
Tomokazu Sano
Keyword(s):  
Single Pulse ◽  
Laser Pulses ◽  
Mechanical Effect ◽  
Intense Laser ◽  
Laser Peening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Intense Laser Pulses ◽  
Laser Peening Without Coating ◽  
Compressive Residual Stresses

Laser peening without coating (LPwC) involves irradiating materials covered with water with intense laser pulses to induce compressive residual stress (RS) on a surface. This results in favorable effects, such as fatigue enhancement; however, the mechanism underlying formation of the compressive RS is not fully understood. In general, tensile RS is imparted on the surface of the material due to shrinkage after heating by laser irradiation. In this study, we assessed the thermo-mechanical effect of single laser pulse irradiation and introduce a phenomenological model to predict the outcome of LPwC. To validate this model, RS distribution across the laser-irradiated spot was analyzed using X-ray diffraction with synchrotron radiation. In addition, the RS was evaluated across a line and over an area, following irradiation by multiple laser pulses with partial overlapping. Large tensile RSs were found in the spot irradiated by the single pulse; however, compressive RSs appeared around the spot. In addition, the surface RS state shifted to the compressive side due to an increase in overlap between neighboring laser pulses on the line and over the area of irradiation. The compressive RSs around a subsequent laser spot effectively compensated the tensile component on the previous spot by controlling the overlap, which may result in compressive RSs on the surface after LPwC.

scholarly journals The Effect of Laser Peening without Coating on the Fatigue of a 6082-T6 Aluminum Alloy with a Curved Notch

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 728 ◽  
Author(s):  
Enrico Troiani ◽  
Nicola Zavatta
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Fatigue Behavior ◽  
Surface Hardness ◽  
Element Model ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Laser Peening ◽  
Laser Peening Without Coating

Laser shock peening has established itself as an effective surface treatment to enhance the fatigue properties of metallic materials. Although a number of works have dealt with the formation of residual stresses, and their consequent effects on the fatigue behavior, the influence of material geometry on the peening process has not been widely addressed. In this paper, Laser Peening without Coating (LPwC) is applied at the surface of a notch in specimens made of a 6082-T6 aluminum alloy. The treated specimens are tested by three-point bending fatigue tests, and their fatigue life is compared to that of untreated samples with an identical geometry. The fatigue life of the treated specimens is found to be 1.7 to 3.3 times longer. Brinell hardness measurements evidence an increase in the surface hardness of about 50%, following the treatment. The material response to peening is modelled by a finite element model, and the compressive residual stresses are computed accordingly. Stresses as high as −210 MPa are present at the notch. The ratio between the notch curvature and the laser spot radius is proposed as a parameter to evaluate the influence of the notch.

Enhancement of fatigue properties of 2024-T351 aluminum alloy processed by cryogenic laser peening

Vacuum ◽  
2019 ◽  
Vol 164 ◽  
pp. 41-45 ◽  
Author(s):  
Jing Li ◽  
Aixin Feng ◽  
Jianzhong Zhou ◽  
Huan Chen ◽  
Yunjie Sun ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Properties ◽  
Laser Peening

Improvement in fatigue properties of 2024-T351 aluminum alloy subjected to cryogenic treatment and laser peening

2018 ◽  
Vol 345 ◽  
pp. 31-39 ◽  
Author(s):  
Jianzhong Zhou ◽  
Jing Li ◽  
Suqiang Xu ◽  
Shu Huang ◽  
Xiankai Meng ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Cryogenic Treatment ◽  
Fatigue Properties ◽  
Laser Peening

Improvement of residual stress and fatigue properties of high-strength steel by low-pulse energy microchip laser

2021 ◽  
Author(s):  
Yoshio Mizuta ◽  
Yuji Sano ◽  
Satoshi Tamaki ◽  
Yoshihiro Sagisaka ◽  
Tomoharu Kato ◽  
...  
Keyword(s):  
Residual Stress ◽  
Pulse Energy ◽  
High Strength Steel ◽  
High Strength ◽  
Microchip Laser ◽  
Fatigue Properties

Effect of Laser Peening on Residual Stress and Micro-Hardness of TC4 Titanium Alloy

2013 ◽  
Vol 341-342 ◽  
pp. 246-250
Author(s):  
Hong Chao Qiao ◽  
Ji Bin Zhao ◽  
Yi Xiang Zhao ◽  
Lun Li
Keyword(s):  
Residual Stress ◽  
Titanium Alloy ◽  
Layer Thickness ◽  
Pulse Energy ◽  
Work Piece ◽  
Laser Peening ◽  
Micro Hardness ◽  
X Ray Diffraction ◽  
Hardness Tester ◽  
Tc4 Titanium Alloy

Laser peening offers potential advantages over conventional peen technologies in terms of the depth of the residual stresses that can be induced, and improvements in surface micro-hardness. The present study was undertaken to understand the effect of laser penning on the properties of titanium alloy, a TC4 titanium alloy work-piece was processed with ND: YAG laser with the wavelength of 1064 nm, pulse energy of 0-10J and pulse width of 12ns, and micro-hardness and residual stress for different laser peening parameters were examined and analyzed by micro-hardness tester and X-ray diffraction. Results are presented and discussed of the residual stress profiles and the micro-hardness profiles, The experimental results show that the satisfying laser peening appearance can be achieved when the pulse energy was 6J, water tamping layer thickness was 1.8mm and ablative layer thickness was 100μm, surface micro-hardness increased by up to 33% and the compressive residual stress on the surface of laser shocked area reached up to-327.8MPa, laser peening improved hardness and residual stress of titanium alloy significantly. The experiment results show that the effect of laser peening was evidently.

Sign in / Sign up

Export Citation Format

Share Document