Investigations for Lowering Pulse Energy of Laser-peening for Improving Fatigue Strength

Sakino, Yoshihiro; Sano, Yuji

doi:10.2207/qjjws.36.153

Cited by 8 publications

(7 citation statements)

References 6 publications

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“…Low-energy LPwC was applied to welded joints of HT780 (780 MPa grade high-strength steel) structural steel with pulse energies down to 10 mJ. Fatigue testing revealed that the fatigue lives were sufficiently prolonged by LPwC even if 10 mJ pulse energy was used [16].…”

Section: Discussionmentioning

confidence: 99%

“…Fatigue strengths of FH and SR materials with LPwC were 300 MPa and 340 MPa at 10 8 cycles, respectively, i.e., LPwC enhanced the fatigue strengths by 1.7 and 1.4 times as great as those of the reference materials. Fatigue properties enhancement was also confirmed in uniaxial fatigue of steel [16,29,30], aluminum alloy [31] and titanium alloy [15].…”

Section: Effects On Fatigue Propertiesmentioning

confidence: 91%

Section: Palmtop-sized Handheld Laser Developmentmentioning

confidence: 94%

“…In the course of the investigation, the pulse energy was reduced from 200 mJ to 100 mJ and then 50 mJ, the fatigue lives were significantly prolonged nevertheless [33]. Further experiments showed LPwC with the pulse energy even down to 20 mJ or 10 mJ has sufficient effects to enhance fatigue properties as shown in Figure 11 [16]. Considering such progress on the low-energy LPwC, the development of 20 mJ-class palmtopsized handheld lasers was initiated in 2014 in a five-year Japanese national program, ImPACT [17].…”

Section: Palmtop-sized Handheld Laser Developmentmentioning

confidence: 95%

“…LPwC significantly enhanced the fatigue strength and prolonged the fatigue life of steels [10][11][12], aluminum alloys [13] titanium alloys [14,15], etc. Recently, Sakino et al confirmed the effect enhancing fatigue properties of HT780 (780 MPa grade high-strength steel) by low-energy LPwC with pulse energies down to 20 and 10 mJ [16]. Considering these advances, the Japanese government launched a five-year national program, ImPACT (Impulsing PAradigm Change through Disruptive Technologies) in 2014 to develop compact high-power pulsed lasers including 20 mJ-class palmtop-sized handheld lasers [17], which brings about further applications beyond the horizons of the present LPwC by realizing a portable system with the handheld lasers, for example applications to infrastructure in the field such as bridges, windmills, etc.…”

Section: Introductionmentioning

confidence: 99%

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Quarter Century Development of Laser Peening without Coating

Sano

2020

Metals

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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.

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Section: Discussionmentioning

confidence: 99%

Section: Effects On Fatigue Propertiesmentioning

confidence: 91%