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Deep and high precision cutting of alumina ceramics by picosecond laser
摘要： Ceramics possess high thermal and chemical resistance, low density, and high compressive strength; however, the machining complications imposed by their inherent brittleness limit their range of applications. Laser cutting technology can offer an automated manufacturing technique for machining these brittle materials. In this paper, a laser cutting method, so-called wobbling, was developed for performing deep, high precision, and defect-free laser cutting of industrial grade alumina ceramics. This work explored picosecond laser process parameters such as focal position, linear speed, and wobble amplitude in order to control cut depth and optimize cut quality in terms of kerf width, kerf taper, surface cleanness, while avoiding crack formation. The morphology and cut quality were evaluated using 3D laser scanning microscopy and scanning electron microscopy (SEM). Picosecond laser cutting process parameters were optimized, achieving a maximum material removal rate of ~10 mm3/min. It was shown that the laser cutting process developed via these experiments represents an effective and efficient manufacturing tool that can be incorporated in engineered net shaping systems.
关键词： Laser cutting,Material removal rate,Ablation,Ultrafast laser micromachining,Alumina ceramics
更新于2025-09-23 15:21:01
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Experimental study on two-phase boiling in wavy copper microchannels fabricated with ultrafast laser micromachining
摘要： In this study, the sinusoidal wavy (SW) copper microchannels with triangular cross section were fabricated with the ultrafast laser micromachining approach. The flow boiling of de-ionized water in SW microchannel were experimentally studied under mass fluxes of 43.43-217.15 kg/(m2s) and heat fluxes of 0-590 kW/m2. The flow patterns in the SW microchannels were visually observed and the boiling heat transfer characteristics were analyzed based on the obtained data. It shows the SW microchannel has a maximum enhancement of 127.7% in local heat transfer coefficient with an acceptable increase of pressure loss compared to the straight one in present work. In SW microchannel, a low degree of superheat can trigger the onset of nucleate boiling. A slow decreasing tendency of local heat transfer coefficient under a high effective heat flux or a high vapor quality was observed. The heat transfer mechanism of flow boiling in SW microchannel was analyzed based on the experimental visualization. Nucleate boiling and thin film evaporation are the dominant modes under different thermal boundary conditions. The flow boiling instability phenomenon in microchannels can be diminished using the wavy structures.
关键词： Boiling heat transfer,Sinusoidal wavy microchannel,Flow instability,Ultrafast laser micromachining
更新于2025-09-19 17:13:59
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Femtosecond lasers for high-precision orthopedic surgery
摘要： Laser micromachining with ultrashort pulses has shown great promise for clean, safe surgical treatment of bone tissue. However, comparisons of performance and development of “best practice” have been hampered by the difficulty of comparing results across a wide variety of experimental approaches and under surgically irrelevant conditions (e.g., dried, dead bone). Using a femtosecond (fs) pulsed laser system (τ = 140 fs, repetition rate = 1 kHz, λ = 800 nm), a comprehensive study of femtosecond laser microsurgery using the standard metrics of laser micromachining (ablation threshold, incubation effects, ablation rates, effect of focal point depth within the material and heat affected zone (HAZ)) was conducted on live, freshly harvested bovine and ovine cortical bone. Three important points of optimism for future implementation in the surgical theatre were identified: (1) the removal of material is relatively insensitive to the focal point depth within the material, removing the need for extreme depth precision for excellent performance; (2) femtosecond laser ablation of fresh bone demonstrates very little incubation effect, such that multiple passes of the laser over the same region of bone removes the same amount of material; and (3) the complete absence of collateral damage, heat- or shock-induced, on both the macro- and microscopic scales can be achieved readily, within a broad parameter range. Taken together, these results indicate a handheld or robotic deployed fiber laser platform for femtosecond laser microsurgery is a very viable prospect.
关键词： Laser ablation,Ultrafast laser micromachining,Femtosecond microsurgery,Laser micromachining,Orthopedic surgery
更新于2025-09-16 10:30:52