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Reduction of Radius of Curvature in Thin-Sheet-Metal Bending by Ultrashort-Pulsed Laser Peen Forming
摘要： Ultrashort-pulsed laser peen forming is a method of thin-sheet-metal forming using laser-induced shock waves. The authors have applied the process to microsheet parts bending, which is accomplished by repeating line scanning. However, when a severe curvature is requested, nonnegligible reduction of sheet thickness is induced by laser ablation. In order to restrict the thickness reduction, the authors attempted to improve the bending efficiency, which would allow a reduction in the number of necessary pulses. Scanning velocity and scanning pitch were changed, while the total irradiated pulse number was constant. The obtained results showed that a scanning velocity higher than the conventional one is favorable for improving the bending efficiency. In addition, smaller scanning pitches were adopted to reduce the radius of curvature. The influence of the scanning pitch on the bending efficiency was much weaker than that of scanning velocity. From the results of the evaluation of efficiency and scanned surface asperity, a scanning velocity of 20 mm·s-1 was judged to be the best. The best scanning condition achieved a 40% smaller radius of curvature than the conventional one.
关键词： bending,bending efficiency,laser-induced shock wave,ultrashort-pulsed laser,incremental forming,scanning velocity,forming property,laser peen forming
更新于2025-09-23 15:21:01
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Expansion of laser-induced plume after the passage of a counter shock wave through a background gas
摘要： Double-pulsed laser ablation with two targets and lasers in a background gas is a method to form nanoparticle complex. Effects of pulse delay between two lasers on plume expansion dynamics are discussed. The germanium and silicon targets were set parallel to each other and irradiated by two YAG lasers. The germanium target was irradiated followed by irradiation of the silicon target with delay time, td. We found that the expansion distance of delayed silicon plume is enhanced for 2 μs ≤ td ≤ 50 μs, compared to that when only the silicon target is irradiated. For td = 200 μs, the expansion distance of delayed silicon plume is similar to that when only the silicon target is irradiated. We discuss the expansion dynamics of the delayed silicon plume based on the effect of the density distribution induced by the primary germanium plume. Our results indicate that the effect of primary germanium plume remains up to about td = 50 μs, and it disappears by td = 200 μs.
关键词： Shock wave,Pulsed laser ablation,Plume expansion,Pulsed laser deposition
更新于2025-09-23 15:21:01
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Numerical study of microscale laser bulging based on crystal plasticity
摘要： Microscale laser bulging is an innovative and promising micro metal forming technology and is widely used in the micro electronics industry. With the image-based Voronoi tessellations, the three-dimensional finite element models of disk-shaped polycrystalline aggregates with different initial grain sizes were established to simulate the processes of microscale laser bulging of pure copper foil. The temporal-spatial-distributed laser shock wave pressure was employed to deform the polycrystalline aggregates of pure copper foil. A size-dependent unified constitutive model of crystal plasticity, incorporating the thermally-activated and viscous drag-dominated stages of dislocation motion, was developed and implemented into the finite element codes to describe the plastic deformation behavior at a wide range of strain rates. In the cases of different laser shock wave pressures and initial grain sizes, the predicted maximum bulging heights of pure copper foil are in good agreement with the experimental data, and the resultant thickness and surface roughness also correlate well with the corresponding experiment observations. The simulated equivalent plastic strains and Mises stresses of residual stress components were analyzed by the cross comparisons, and the effect of grain boundary on laser shock wave was further discussed in detail.
关键词： laser shock wave,numerical simulation,polycrystalline aggregates,crystal plasticity,microscale laser bulging
更新于2025-09-23 15:19:57
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[IEEE 2018 International Symposium on Micro-NanoMechatronics and Human Science (MHS) - Nagoya, Japan (2018.12.9-2018.12.12)] 2018 International Symposium on Micro-NanoMechatronics and Human Science (MHS) - Uniform Transfection: Shock Wave Generation in Laser Ablation and Microcontact Printing
摘要： With the increasing need of regenerative medicines, cell therapy, and biopharmaceutical drug, it is necessary to develop a method for massively parallel delivery and uniform transfection. This research explores the possibility of using μCP (using cell adhesive and cell blocking agents) for printing massive number of cells on a substrate and using optoporation methods (nano-second pulsed radiation) to perforate cell membranes. With combining these two methods, a stand-alone micro-device capable of performing localized intracellular delivery will be developed. In this paper, we confirmed the generation of shock wave upon optoporation, tried intra-cellular delivery using Calcein, develop the stamp for micro-contact printing and performed the printing.
关键词： optoporation,laser ablation,uniform transfection,shock wave generation,microcontact printing
更新于2025-09-19 17:13:59
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Thermal Relaxation Features of Residual Stresses Arising upon Laser Shock Processing of Heat-Resistant Materials
摘要： In this paper, we study the thermal relaxation features of compressive residual stresses generated during laser-shock wave processing in high-alloyed heat-resistant Iron GH2036 alloy. A finite element modeling of thermal relaxation of the generated compressive residual stresses was performed. The features of the thermal effects on the redistribution of the compressive residual stresses in the temperature range from 200 to 650°C are studied. Based on comparative analysis, the results of the finite element modeling correlated well with the experimental data known in the literature.
关键词： residual stresses,thermal relaxation,finite element modeling,laser-shock wave treatment
更新于2025-09-19 17:13:59
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Increased Tattoo Fading in a Single Laser Tattoo Removal Session Enabled by a Rapid Acoustic Pulse Device: A Prospective Clinical Trial
摘要： Background and Objectives: The ability to provide improved tattoo fading using multiple laser passes in a single office laser tattoo removal session is limited. In part, this is due to the loss of laser effectiveness caused by epidermal and dermal vacuole “whitening” generated during the initial laser pass at the tattoo site. The Rapid Acoustic Pulse (RAP) device generates acoustic shock wave pulses epidermal and dermal vacuoles to enable multiple laser passes in a single office laser tattoo removal session. The objectives of this study were to determine if the RAP device, when used as an accessory to the 1064 nm Nd:YAG Q‐switched (QS) laser can enable delivery of multiple laser passes in a single office laser tattoo removal session, and therefore result in increased tattoo fading compared to the clinical standard single‐pass QS laser tattoo removal session. Study Design/Materials and Methods: The RAP device was evaluated in a single‐center (SkinCare Physicians), prospective, IRB approved study. A total of 32 black ink tattoos, from 21 participants, were divided into three zones and treated with either multiple QS laser passes, each followed by 1 minute of RAP device application (Laser + RAP) in zone one and single‐pass QS laser treatment (Laser‐Only) in zone two, separated by an untreated control zone. The treatment sites were assessed for the number of laser passes and adverse events immediately, 6 weeks, and 12 weeks following the treatment session. Photographs of the treatment sites were assessed for percent fading at 12 weeks post‐treatment by three blinded reviewers. Results: When the RAP device was applied as an accessory to the QS laser in a multi‐pass laser tattoo removal treatment, an average of 4.2 laser passes were delivered in a single session, with no unexpected or serious RAP device‐related adverse events. At the 12‐week follow‐up, tattoos treated with Laser + RAP showed a statistically significant increase in average fading (44.2%) compared with tattoos treated with Laser‐Only (P < 0.01). Additionally, a significantly higher (24.8%) overall proportion of tattoos treated with Laser + RAP (37.5%) had a response of >50% fading compared with tattoos treated with QS Laser‐Only (9.4%) (P < 0.01) as well as a response of >75% fading from Laser + RAP treatment (21.9%) compared with Laser‐Only treatment (3.1%) (P < 0.05). Conclusions: The RAP device, applied as an accessory to the 1064 nm Nd:YAG QS laser, safely enables multiple QS laser treatments in a single office laser tattoo removal session by clearing the whitening caused by the previous QS laser pass. Enabling multiple QS laser passes results in a statistically significant increase in tattoo fading in a single office laser tattoo removal session compared to the clinical standard single‐pass QS laser tattoo removal session.
关键词： tattoo removal,Q‐switched laser,acoustic shock wave,acoustic pulse
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Anisotropic Dispersive Shock Waves in Highly Nonlinear M-Cresol/Nylon
摘要： M-Cresol/Nylon is a chemical solution, which is made up of an organic solvent (m-cresol) and a synthetic polymeric solute (nylon). Recent experiments showed that this solution exhibits an isotropic giant self-defocusing nonlinearity, tunable by varying the nylon concentration [1]. When it is enlightened by a continuous-wave laser beam, light absorption induces heat gain, which reduces the refractive index: the material experiences a nonlinear thermo-optical effect, made nonlocal by the heat diffusion. Since the temperature changes with the beam intensity, this nonlinearity follows a nonlocal Kerr model, expressed by the nonlinear Schroedinger equation (NLSE) [2]. In particular, V. Smith et al. measured the m-cresol/nylon nonlinear Kerr coef?cient n2 and found that, if for pure m-cresol it is ?9 × 10?8cm2/W , for a nylon mass concentration of 3.5% it is ?1.6 × 10?5cm2/W , a magnitude higher than most of the other thermal nonlinear materials reported in literature. In optics, many phenomena are ruled by NLSE, such as soliton propagation and dispersive shock wave (DSW) generation [1,2]. We report experimental evidence of two-dimensional optical DSWs with an anisotropic zero-singularity (Fig. 1). Fixing z as the longitudinal and x, y as the transverse directions, we start with a beam that has a Gaussian pro?le along y but a Gaussian ?rst derivative along x, thus the intensity is null for x = 0. This speci?c initial condition causes a new phenomenon, reported here for the ?rst time: the shock develops undular bores on the beam external borders (as already known in literature [2]), but around the singularity it presents an abrupt intensity discontinuity. We theoretically analyze the wave breaking along all the propagation. By a hydrodynamic model, we study the beam before the shock point: the WKB approach and the characteristic method let us predict the wave breaking both in phase and in intensity [2]. In order to model the beam propagation beyond the shock point, we use mathematical tools of time asymmetric quantum mechanics and uncover the mechanism how such an abrupt intensity discontinuity is generated [3]. We numerically simulate these results and ?nd remarkable agreement both with experiments and with theoretical predictions. Our outcome not only con?rms previous studies on the giant nonlinear response of m-cresol/nylon, but also discloses fundamental insights on propagation of DSWs with a singular initial intensity pro?le.
关键词： Dispersive shock wave generation,Anisotropic Dispersive Shock Waves,Highly Nonlinear M-Cresol/Nylon,Nonlinear Schroedinger equation,Thermo-optical effect
更新于2025-09-16 10:30:52
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Surface dynamic deformation of LY2 aluminum alloy subjected to a laser shock wave planishing technique with different kinds of contacting foils
摘要： In this paper, a laser shock wave planishing technique (LSWP) was used to treat the LY2 aluminum alloy surface with corrugated structures, and the influence of contacting film material on the planishing effect was studied. The dynamic response characteristics of surface micro-features under different physical parameters of contacting foils were simulated by finite element simulation (FEM), and experimental verification was carried out. A close match between the experimental results with these simulation results in FEM was found. The planishing of surface micro-protrusions can reduce the surface roughness of treated sample, and the lifting of bottom materials can ensure the surface profile accuracy. The results demonstrate that the planishing effect on micro-protrusions improves with the density of the contacting foil decreasing; The lifting effect on the bottom material enhances with the strength of the contacting foil increasing. A high modulus of elasticity contacting foil also facilitates the bottom material bulging.
关键词： Micro-features,Aluminum alloy,Finite element modeling,Surface topography,Laser shock wave,Dynamic response
更新于2025-09-16 10:30:52
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Efficiency improvement of thin-sheet-metal bending by femtosecond laser peen forming
摘要： Femtosecond laser peen forming is die-less incremental sheet forming using laser induced shock waves. It was applied to bending of thin sheet micro parts. When severe curvatures are requested, the process needs dense laser pulse irradiation, which reduces sheet thickness remarkably owing to excessive laser ablation. High bending efficiency per pulse is necessary to realize a small radius of curvature without sheet thickness reduction. The authors attempted to improve the bending efficiency by changing scanning velocity and scanning pitch. Optimized scanning achieved 40% smaller radius of curvature than conventional one, in spite of same irradiated pulse density. Obtained knowledge is effective in miniaturization and productivity increase.
关键词： Femtosecond laser,Bending,Thin-sheet-metal,Laser peen forming,Bending efficiency,Laser induced shock wave,Micro parts
更新于2025-09-12 10:27:22
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Spatial confinement of laser-induced plasma by laser-induced and obstacle-reflected shock wave and its effect on optical emission of laser-induced plasma
摘要： The laser-induced plasma (LIP) and the shock wave generated by pulsed laser ablation of a graphite target in air and reflected by a flat obstacle were examined by optical emission spectroscopy and probe beam deflection measurements. The interaction between the LIP and the shock wave and its effects on the expansion of the LIP as well as on the optical emission of carbon atoms were studied. The carbon atomic emission can be enhanced or reduced in the situation with a flat obstacle standing in the propagation path of the shock wave. The enhancement or reduction of the carbon atomic emission has a close connection with the shock wave generated by graphite ablation and reflected by the obstacle. The reflected shock wave confines the expansion of the LIP and impedes the travelling of the plasma species. The enhancement was observed at the detection position close to the target and with a short block-target distance. The shock wave thus reflected encounters the luminous LIP at its early expanding stage and confines the expansion of the LIP, resulting in the enhancement in the optical emission of carbon atoms. But at the detection position far from the target and with a longer block-target distance, a reduction in the optical emission due to spatial confinement was observed. The possible mechanisms responsible for the effects of spatial confinement on the optical emission were discussed.
关键词： laser-induced plasma,spatial confinement,optical emission spectroscopy,shock wave,probe beam deflection
更新于2025-09-12 10:27:22