Pulsed Laser Heating and Melting

Sands, David

doi:10.5772/28736

Cited by 24 publications

(20 citation statements)

References 39 publications

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“…Different methods such as Laplace transform, separation of variables and Green's function to solve partial differential governing equation of laser surface melting were used in different conditions. The analytical and numerical modellings support each other in verifying the results obtained from the simulation [7][8][9][10][11][12].…”

Section: Introductionsupporting

confidence: 66%

3D thermal model of laser surface glazing for H13 tool steel

Kabir

Yin

Naher

2017

AIP Conference Proceedings

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This is the accepted version of the paper.This version of the publication may differ from the final published version. Abstract. In this work a three dimensional (3D) finite element model of laser surface glazing (LSG) process has been developed. The purpose of the 3D thermal model of LSG was to achieve maximum accuracy towards the predicted outcome for optimizing the process. A cylindrical geometry of 10mm diameter and 1mm length was used in ANSYS 15 software. Temperature distribution, depth of modified zone and cooling rates were analysed from the thermal model. Parametric study was carried out varying the laser power from 200W-300W with constant beam diameter and residence time which were 0.2mm and 0.15ms respectively. The maximum surface temperature 2554K was obtained for power 300W and minimum surface temperature 1668K for power 200W. Heating and cooling rates increased with increasing laser power. The depth of the laser modified zone attained for 300W power was 37.5μm and for 200W power was 30μm. No molten zone was observed at 200W power. Maximum surface temperatures obtained from 3D model increased 4% than 2D model presented in author's previous work. In order to verify simulation results an analytical solution of temperature distribution for laser surface modification was used. The surface temperature after heating was calculated for similar laser parameters which is 1689K. The difference in maximum surface temperature is around 20.7K between analytical and numerical analysis of LSG for power 200W. Permanent repository link

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Section: Introductionsupporting

confidence: 66%

3D thermal model of laser surface glazing for H13 tool steel

Kabir

Yin

Naher

2017

AIP Conference Proceedings

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“…The absorption of laser energy occurs mainly at the silicon substrate. Hence, the following well-known formula is suitable for estimation of surface temperature growth: ΔTE2q(1-R)(aτ) 1/2 /(kπ 1/2 ) [20]. Here q is laser light power density, R -reflection coefficient, a -thermal diffusivity, τ -pulse duration, k -thermal conductivity.…”

Section: Discussionmentioning

confidence: 99%

Laser-induced local profile transformation of multilayered graphene on a substrate

Фролов

Pivovarov

Zavedeev

et al. 2015

Optics & Laser Technology

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“…Temperature simulations were performed with the use of a simple 1D analytical model of tissue temperature during laser irradiation. The simulated temperature from the solution of 1D heat diffusion equation is formulated as

T (normalz, normalt) = \frac{2 μ_{a} I}{λ} \sqrt{Dt} italicierfc [\frac{z}{2 \sqrt{italicDt}}] + T_{0}

where

i e r f c false(normalz false) = \int_{z}^{\infty} (1 - (2 / \sqrt{π}) \int_{0}^{x} e^{- t^{2}} d t) d x

μ_{a}

is the absorption coefficient (cm −2 ), I is the power density of laser (W/cm 2 ), D is the thermal diffusivity (cm 2 /s), and

λ

is the thermal conductivity (W/cm/K). For the simulations conducted in this study, I was 50 W/cm 2 ,

μ_{a}

was 0.02 cm −1 for the porcine cardiac tissue, and the thermal parameters of the cardiac tissue in the model were calculated based on the assumption that the water content of the tissue was 70% .…”

Section: Methodsmentioning

confidence: 99%

Application of Ultrasound Thermal Imaging for Monitoring Laser Ablation in Ex Vivo Cardiac Tissue

et al. 2019

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Background and Objective Laser ablation can be used to treat atrial fibrillation by thermally isolating pulmonary veins. In this study, we evaluated the feasibility of high‐resolution (<1 mm) ultrasound thermal imaging to monitor spatial temperature distribution during laser ablation on ex vivo cardiac tissue. Study Design/Materials and Methods Laser ablation (808 nm) was performed on five porcine cardiac tissue samples. A thermocouple was used to measure the interstitial tissue temperature during the laser ablation process. Tissue‐strain‐based ultrasound thermal imaging was conducted to monitor the spatial distribution of the temperature in the cardiac tissue. The tissue temperature was estimated from the time shifts of ultrasound signals owing to the changes in the speed of sound and was compared with the measured temperature. The temperature estimation coefficient k of porcine cardiac tissue was calculated from the estimated thermal strain and the measured temperature. The degree of tissue coagulation (temperatures > 50°C) was derived from the estimated temperature and was compared with that of the tested cardiac tissue. Results The estimated tissue temperature using strain‐based ultrasound thermal imaging at a depth of 1 mm agreed with thermocouple measurements. During the 30‐second period of the laser ablation process, the estimated tissue temperature increased from 25 to 70°C at a depth of 0.1 mm, while the estimated temperature at a depth of 1 mm increased up to 46°C. Owing to the uncertainty of the coefficient k, the k value of the porcine cardiac tissue varied from 160 to 220°C with temperature changes of up to 20°C. The estimated coagulation region in the ultrasound thermal imaging was 20% wider (+0.6 mm) but 9% shallower (−0.1 mm) than the measured region of the ablated porcine cardiac tissue. Conclusions The current study demonstrated the feasibility of temperature monitoring with the use of ultrasound thermal imaging during the laser ablation on ex vivo porcine cardiac tissue. The high‐resolution ultrasound thermal imaging could map the spatial distribution of the tissue temperature. The proposed method can be used to monitor the temperature and thermal coagulation to achieve effective laser ablation for atrial fibrillation. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

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Pulsed Laser Heating and Melting

Cited by 24 publications

References 39 publications

3D thermal model of laser surface glazing for H13 tool steel

3D thermal model of laser surface glazing for H13 tool steel

Laser-induced local profile transformation of multilayered graphene on a substrate

Application of Ultrasound Thermal Imaging for Monitoring Laser Ablation in Ex Vivo Cardiac Tissue

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