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Investigation of cut quality in fiber laser cutting of CFRP
摘要： Fiber laser cutting of CFRP sheets was investigated using a 2 kW multi-mode fiber laser, focusing on how the cut quality factors, such as kerf width, kerf depth, matrix evaporation width, matrix recession width, kerf taper angle, matrix damage zone, and cut surface morphology, change as laser power, laser scanning speed, and the number of laser passes are varied. By designing a systematic experiment on a large process window, several important parameters for kerf width, kerf depth, matrix evaporation width, and matrix recession width were identified, and using them, it was verified that the beam scanning speed is a dominant factor for minimizing thermal damages. Also, circular rings were observed in each carbon fiber at the cut surfaces, and it looked as if they were generated when each fiber was thermally fused in the radial direction. A larger number of laser passes was found to contribute to a smooth surface morphology, because of the formation of highly-fused surfaces, which prevents fiber delamination and pull-outs. Optimum process conditions were also identified by comparing various cut quality factors.
关键词： Fiber laser cutting,Optimal process conditions,Cut quality factors,Thermal damage,Carbon fiber reinforced plastic (CFRP)
更新于2025-11-28 14:24:20
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HIFU-induced changes in optical scattering and absorption of tissue over nine orders of thermal dose
摘要： The optical properties of tissue change during thermal ablation. Multi-modal methods such as acousto-optic (AO) and photo-acoustic (PA) imaging may provide a real-time, direct measure of lesion formation. Baseline changes in optical properties have been previously measured over limited ranges of thermal dose for tissues exposed to a temperature-controlled water bath, however, there is scant data for optical properties of lesions created by HIFU. In this work, the optical scattering and absorption coefficients from 400–1300 nm of excised chicken breast exposed to HIFU were measured using an integrating sphere spectrophotometric technique. HIFU-induced spatiotemporal temperature elevations were measured using an infrared camera and used to calculate the thermal dose delivered to a localized region of tissue. Results obtained over a range of thermal dose spanning 9 orders of magnitude show that the reduced scattering coefficient increases for HIFU exposures exceeding a thermal dose of CEM43 = 600 ± 81 cumulative equivalent minutes. HIFU-induced thermal damage results in changes in scattering over all optical wavelengths, with a 2.5-fold increase for thermal lesions exceeding 70 °C. The tissue absorption coefficient was also found to increase for thermally lesioned tissue, however, the magnitude was strongly dependent on the optical wavelength and there was substantial sample-to-sample variability, such that the existence of a threshold thermal dose could not be determined. Therapeutic windows, where the optical penetration depth is expected to be greatest, were identified in the near infrared regime centered near 900 nm and 1100 nm. These data motivate further research to improve the real-time AO and PA sensing of lesion formation during HIFU therapy as an alternative to thermometry.
关键词： thermal damage,optical properties,thermal dose,lesion,high-intensity focused ultrasound
更新于2025-09-23 15:21:01
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Characterization of Thermal Damage Due to Two-Temperature High-Order Thermal Lagging in a Three-Dimensional Biological Tissue Subjected to a Rectangular Laser Pulse
摘要： The use of lasers and thermal transfers on the skin is fundamental in medical and clinical treatments. In this paper, we constructed and applied bioheat transfer equations in the context of a two-temperature heat conduction model in order to discuss the three-dimensional variation in the temperature of laser-irradiated biological tissue. The amount of thermal damage in the tissue was calculated using the Arrhenius integral. Mathematical difficulties were encountered in applying the equations. As a result, the Laplace and Fourier transform technique was employed, and solutions for the conductive temperature and dynamical temperature were obtained in the Fourier transform domain.
关键词： laser pulse,biological tissue,two-temperature thermal lagging,three dimensions,thermal damage
更新于2025-09-23 15:19:57
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Analytical solutions of thermal damage in living tissues due to laser irradiation
摘要： In this article, the analytical solutions of dual-phase-lag (DPL) bio-heat equation with various boundary conditions have been constructed for curative therapy of cancerous cells. The volumetric thermal source components in the model of DPL bioheat transfer, such as the metabolic heat generation and the rate of blood perfusion, are considered. The analytical solutions in the Laplace domain are obtained. The thermal injuries to the tissue are assessed by the denatured protein range, using the formulation of Arrhenius. Numerical outcomes for temperatures are graphically introduced. A parametric analysis is devoted to the identification of an appropriate procedure for selecting important design variables in order to predict more accurate to reach effective heating in hyperthermia treatment.
关键词： thermal damage,dual-phase-lag model,Bioheat transfer,living tissue
更新于2025-09-19 17:13:59
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[Laser Institute of America ICALEO? 2014: 33rd International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - San Diego, California, USA (October 19–23, 2014)] International Congress on Applications of Lasers & Electro-Optics - Laser microjet? cutting of up to 3 mm thick sapphire
摘要： The Laser Microjet? is a world-wide patented technology which uses ns-laser pulses which is guided to the work piece in a water jet. The sample is therefore cooled by the water and thermal damage during cutting is reduced which is relevant for metals and semiconductor materials. For the case of sapphire cutting this leads to lower thermal load of the samples and therefore no cracking during cutting. Sapphire cutting was until now not possible with the Laser Microjet? although it is used for micro machining of a lot of other materials like semiconductors, metals, diamond and ceramics. Cutting up to 3 mm thick sapphire with parallel walls with a roughness of < 0.5 μm and a kerf width of < 100 μm is achieved. The cutting speed of up to 0.1 mm/s for 1 mm samples has been achieved. The cut samples exhibit parallel walls which is a big advantage of the Laser Microjet? technology compared to other laser cutting technologies, not only for sapphire. The edges at the front side exhibit high quality with a radius of curvature of less than 20 μm and without any chipping. The back side quality still needs to be improved although chips with less than < 20 μm are already achievable. For laser cutting of sapphire high peak intensities are required in order to reach sufficient high absorption of the laser radiation and achieve material ablation. The process is not yet fully understood. It is expected that the water jet interaction with the material plays an important role together with laser light-material interaction. The geometry of the kerf of the work piece has a strong influence on the cutting process. Water jet interruptions due to e.g. non planar surfaces lead to loss of energy on the way to the work piece and therefore interruption of the absorption and ablation process. That is why certain processing strategies are necessary to achieve cutting for samples with the thickness of 3 mm. We expect to be able to cut even thicker samples of > 5 mm as well as further improve the backside edge quality in the future.
关键词： high peak intensities,thermal damage reduction,water jet coupled laser,Laser Microjet?,sapphire cutting
更新于2025-09-19 17:13:59
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Comparison of A 1940 nm Thulium-Doped Fiber Laser and A 1470 nm Diode Laser for Cutting Efficacy and Hemostasis in A Pig Model of Spleen Surgery
摘要： Partial and total splenectomies are associated with a high risk of substantial blood loss. Lasers operating at wavelengths strongly absorbed by water have the potential to improve hemostasis and cut while providing a narrow zone of thermal damage. The aim of this study is to compare a thulium-doped fiber laser (TDFL) emitting a wavelength of 1940 nm and a diode laser (DL) operating at 1470 nm for spleen surgery in a pig model. A partial splenectomy and spleen incisions were made in 12 animals using the two laser devices. The hemostasis was evaluated visually during surgeries. Post-mortem and histopathological evaluations were done on days 0, 7, and 14 following surgery. Neither TDFL nor DL caused bleeding on day 0 or delayed bleeding. On day 14, pale streaks at the site of incision were slightly wider after cutting with DL than with TDFL. Histological analysis revealed a carbonized zone with exudation and a deeper zone of thermal tissue damage on day 0. The width of the thermal changes was 655.26 ± 107.70 μm for TDFL and 1413.37 ± 111.85 μm for DL. On day 7, a proliferation of fibroblasts and splenocytes was visible, as well as a formation of multinucleated giant cells adjacent to the residues of carbonization. The zone of thermal damage was broader for DL (1157.5 ± 262.77 μm) than for TDFL (682.22 ± 116.58 μm). On day 14, cutting sites were filled with connective and granulation tissues with the residues of carbonization. The zone of thermal damage was narrower for TDFL (761.65 ± 34.3 μm) than for DL (1609.82 ± 202.22 μm). Thus, both lasers are efficient in spleen surgery, providing good hemostasis. However, TDFL produces a narrower zone of thermal damage, which suggests its better efficiency for spleen surgery, especially when performing more precise procedures.
关键词： thulium-doped fiber laser (1940 nm),pig model of spleen surgery,diode laser (1470 nm),thermal damage zone,partial splenectomy,hemostasis
更新于2025-09-19 17:13:59
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Analytical estimations of temperature in a living tissue generated by laser irradiation using experimental data
摘要： This paper presents an analytical approach associated with Laplace transformation, experimental temperature data, and a sequential concept over time to obtain the thermal damage and the temperature in a living tissue due to laser irradiation. The analytical solutions in the Laplace domain are appreciably obtainable. The thermal damage to the tissue is completely assessed by the denatured protein range using the formulation of Arrhenius. Numerical outcomes for temperatures and the thermal damages are graphically introduced. Besides, the comparison between the numerical computations and the existing experimental study shows that a current mathematical model is an e?ective tool for evaluating the biological heat transfer in biological tissues.
关键词： Living tissue,Thermal damage,Bioheat transfer,Laplace transform
更新于2025-09-11 14:15:04
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Reflections on the Er:YAG Laser Used in “Nonthermal Mode” to Rejuvenate Skin
摘要： CO2 and Er:YAG lasers are both actively used for laser skin rejuvenation, both ablative and microablative. Despite seeming similarities in efficiency of their radiation’s absorption by soft tissues, these lasers may have completely different effects on skin: tissue vaporization with CO2 laser radiation always assumes existence of areas with irreversible thermal effects such as coagulation, dehydration, carbonization, and vaporization. If Er:YAG and vaporization is used for the same purpose, same thermal damage areas may be obtained but smaller in size. However, in case of sufficiently high energy density and short duration of pulses, an ablation mode may be implemented, in the case in which areas of irreversible thermal changes are contained within vaporization zone. Thus, underlying layers of irradiated tissue are not thermally damaged.
关键词： ablation mode,cavitation,Er:YAG laser,microablation,CO2 laser,skin rejuvenation,thermal damage
更新于2025-09-11 14:15:04