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In this study, a picosecond laser was employed for ablating the surface of graphene-reinforced ZK60 (GNPs/ZK60) matrix composites. Various ablation regions were categorized based on their morphological features and interaction mechanisms. The effects of pulse frequency (800–1200 kHz), scanning speed (0.25–4 mm/s), and the number of repetitive scans (1–8 times) on the surface morphology and feature size of ablation recesses were investigated. The results indicate that the formation of micro-peak structures at the bottom of the groove is favored under single-scan conditions. At a pulse frequency of 2000 kHz, the maximum groove depth can reach 42.56 µm. With increasing scanning times, the groove transits from a W-shaped to a V-shaped profile, the micro-peak structure at the bottom of the groove disappears, and the ablation rate decreases significantly. At a scan number of 2, the ablation rate was least affected by the pulse frequency and scanning speed, and the ablation rate increased from 331.34 to 366.23 µm3/min, with a growth rate of 10.5%. [ABSTRACT FROM AUTHOR]

This study investigates the ablation performance of Inconel 718, a nickel-based superalloy, and metal matrix polycrystalline diamond (MMPCD), a super composite, using a nano-second (ns) pulsed laser across a range of ablation conditions. Single trenches varying in energy fluence and scanning speeds were created, analyzing the experimental responses in terms of ablation rate and surface roughness. Using regression techniques, models were developed to understand these relationships. Four multi-objective optimization algorithms, weighted value grey wolf optimizer (WVGWO), multi-objective Pareto search (MOPS), multi-objective genetic algorithm (MOGA), and multi-objective sunflower optimization (MOSFO), were employed to optimize these models. Key findings include MMPCD achieving the highest ablation rates at maximum fluence and lower speeds with negligible recast, resulting in smoother surfaces, whereas Inconel 718 reached its peak rates at similar conditions but exhibited significant surface recast. This research provides valuable insights into ns-pulsed laser machining for advanced materials, emphasizing the impact of fluence and scanning speed on achieving high ablation rates and minimal surface roughness. [ABSTRACT FROM AUTHOR]

Femtosecond laser filament enables energy transfer over long distances, which is of great value for studying long-range ablation. However, the energy coupling of filament with the plasma generated by the ablation process leads to a very complex behavior which limits the ablation efficiency. This study systematically investigated the ablation mechanism of laser-induced filament in alumina ceramic. The plasma shock wave was initially investigated using spectral detection techniques combined with Sedov-Taylor theory. The results indicated that the maximum plasma shock wave reached 30 MPa under the irradiated by a 1 mJ fs laser. The theoretical analysis confirmed the effectiveness of the filament-induced plasma shock wave in enhancing the ablation rate of alumina ceramic. In this context, the experimental studies were conducted with varying filament positions and pulse energies, and the corresponding ablation rates for each parameter were investigated. The filament in the ablation process was found to has a secondary sputtering effect, which is an effective contributor to enhance the ablation rate. The corresponding ablation depth reach to 550 μm while achieving an ablation rate of 3.1 μm3/μJ. Finally, the coupling mechanism between the femtosecond laser filament and the plasma shock wave was systematically revealed. This research will facilitate future laser remote ablation applications with high efficiency. [ABSTRACT FROM AUTHOR]

A large variety of ultrafast laser‐matter interaction regimes and different processed surface finishing qualities of stainless steel can be achieved by varying the laser processing parameters. The optimization of the laser fluence to the most efficient ablation also leads to the lowest surface roughness of the ablated material. High laser fluence together with a high pulse repetition rate leads to heat accumulation, which results in the formation of microstructures with various morphology and scales. The use of GHz bursts allows a rough stainless‐steel surface to be smoothed and even polished. In this work, the fast and high‐quality milling of 2.5D cavities is demonstrated. Laser beam spot optimization is used to increase the throughput of the high‐power femtosecond laser (67.8 W), resulting in an ablation rate of 13 mm3 min−1. The complex cavities are produced by laser milling and cutting in layers. The formation of surface structures on stainless steel because of laser irradiation has been demonstrated. The possibilities of further GHz burst polishing are examined on previously laser‐milled stainless steel using with lowest possible surface roughness. The ability to polish the surface with microstructures below the original roughness is demonstrated by bursts of ultrashort pulses with a repetition rate in the GHz range. It has been demonstrated that mold milling in stainless steel designed for LED diffusers can be fabricated using a modern femtosecond laser source together with beam size optimization technique for efficient ablation with low surface roughness, layer‐by‐layer milling techniques, and GHz burst polishing techniques. [ABSTRACT FROM AUTHOR]

Objective: We aimed to analyze the effect of high‐intensity focused ultrasound (HIFU) on different types of adenomyosis (AM) based on magnetic resonance imaging (MRI) classification. Methods: A total of 206 AM patients who underwent HIFU between January 2017 and December 2021 were included in this retrospective study. The size and location of AM were evaluated based on T2‐weighted imaging (T2WI) of MRI. Patients were divided into internal (subtype I), external (subtype II), intramural (subtype III), and full‐thickness (subtype IV) AM groups. All patients underwent an MRI examination before and one day after HIFU. After ultrasound‐guided HIFU ablation, the parameters of ultrasonic energy input during HIFU treatment among different groups were recorded and compared. The adverse reactions and complications among different groups were compared. Results: The lesion volume in the subtype IV group was significantly larger than the subtype II and III groups (P <.05). The HIFU irradiation time, treatment time, and total energy input in the subtype IV group were significantly higher than the subtype I and III groups (P <.05). The number of cases of abdominal pain and vaginal fluid in the treatment area in the subtype IV group was significantly higher than in the subtype II group. Conclusion: Although HIFU has different treatment strategies and parameters for different subtypes of AM, it can achieve a satisfactory ablation rate, which is safe and effective. [ABSTRACT FROM AUTHOR]

This work aims to study thermal stability and ablative behaviors of Carbon/Phenolic composites containing nano clay, nano graphene oxide and hybrid additives. To this end a detailed explained and illustrated process is involved to synthesize factionalized graphene oxide based on Hummers method. The XRD test result shows a major shift in basal plane reflection to below 2θ = 20° in the provided spectrum, which indicates achievement in the functionalization process. Prepared nanoparticles suspensions are then mixed by resol resin with desire wt% to outcome nanocomposites. An in-depth analysis of SEM images with focus on the dispersion, morphology, and interaction of the nanofillers with the resin matrix reveals that nanoparticles are dispersed properly with no agglomeration. 200 gr/m2 carbon woven fabric is then impregnated with prepared nanocomposites employing an own made prepreg machine to use to construct standard flexural as well as oxy acetylene test specimens. Using bending test, thermogravimetric analysis and oxyacetylene torch test, effects of different percentages of considered nanoparticles on the mechanical properties, thermal stability and ablative of carbon/phenolic composites are assessed and the results are reported. According to the results, adding only 0.1 wt% of nano graphene oxide increases char yield around 5% and remain back surface temperature under 100°C during flame test. Moreover samples with 0.2 wt% of nano clay and hybrid (0.05 wt% nano graphene oxide and 0.1 wt% nano clay) additives provides best reaming amount of solid. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to identify the sonographic indicators that predict the ablation rate and efficiency of uterine fibroids during high-intensity focused ultrasound (HIFU) treatment. Methods: In this retrospective study, we analyzed the clinical data of patients with uterine fibroids who underwent HIFU treatment at Fujian Provincial Hospital between April 2019 and April 2022. Routine abdominal ultrasound examinations were performed to observe potential indicators before the HIFU treatment. After the treatment, enhanced magnetic resonance imaging (MRI) examination was performed within 2 weeks. The fibroid and non-perfused volumes (NPV) were determined, and the ablation rate and energy efficiency factor (EEF) were calculated. Results: A total of 75 patients (124 uterine fibroids) were included in this study. Uterine fibroids with a larger volume, high echogenicity, elliptical/diffuse leaf shape, and a posterior attenuation band had a higher HIFU ablation rate (p<0.05). Uterine fibroids with a larger volume and high echogenicity and without necrotic areas had a lower EEF (p<0.05). Multiple comparisons between fibroid types revealed statistically significant differences in EEF between subserosal and submucosal fibroids (p < 0.05) and between subserosal and mixed-type fibroids (p < 0.05). However, no statistically significant difference was observed between mixed-type and submucosal fibroids. The HIFU ablation rate and EEF showed no significant differences based on location within the wall and blood flow within the fibroids. Conclusion: Sonographic features of uterine fibroids can predict the rate and efficiency of HIFU ablation, providing useful guidance in selecting appropriate treatment for patients. [ABSTRACT FROM AUTHOR]

The thermal protection system (TPS) plays a major role in shielding solid rocket motors (SRMs) against structural failure from excessive heating. This study was directed at the recent innovation in flame‐retardant materials used for thermal insulation, with a particular focus on integrating metal–organic frameworks (MOFs) to bolster thermal stability. Three targeted transition metal‐BDC MOFs (MIL‐88(Fe), MOF‐71(Co), and MOF‐5(Zn)) were hydrothermally synthesized and the effect of incorporating these MOFs into nitrile butadiene rubber (NBR) composites was tracked. In general, the addition of the MOFs improved the interfacial compatibility and the processing of the composites. Additionally, experimental investigations have shown that all MOFs improved the mechanical properties of the NBR composite materials. Specifically, the addition of MOF‐5 has been found to increase the maximum tensile strength to 13 MPa, while MIL‐88 increased the elongation at break to 67.1%. In order to evaluate the thermal stability and ablative resistance of the prepared composites, the oxy‐acetylene flame test was utilized. Results showed that the efficiency of the composite as thermal insulation is highly dependent on the MOF type and the metal included. The impact of MOF‐71(Co) on thermal insulation displayed the least linear and mass ablation rates (0.0168 mm/s and 0.057 g/s, respectively) along with the lowest recorded back‐face temperatures, owing to the formation of a thick and compact char layer upon exposure to flames. [ABSTRACT FROM AUTHOR]

Adhesive bonding is the joining technique that provides the maximum exploitation of Carbon Fiber Reinforced Polymers (CFRPs) for structural applications. However, it is necessary to attain a high-strength adhesive bond, achieved by removing surface contaminants, such as mold release agents, and simultaneously generating a surface structure suitable to increase the actual contact surface area. The purpose of the research work presented in this paper is to evaluate the effect of process parameters of a nanosecond pulsed laser pre-bonding surface treatment on the ablation of thermoset matrix CFRP substrates. In particular, the link between the volume of ablated material and the tensile shear strength (TSS) of adhesive bonded joints was evaluated by lap-shear tests, profilometer surveys, and Scanning Electron Microscope (SEM) analysis. ANOVA and regression models were used to highlight the influence of laser parameters, with power emerging as the most significant factor, and energy density proving pivotal for joint strength. Line spacing was also significant, while scanning direction had negligible impact. The key outcomes of the study demonstrated that controlled laser ablation plays a critical role in determining joint performance. A negative correlation was found between TSS and the thickness of ablated material, indicating that excessive ablation weakens the bond. Optimal joint strength was achieved with moderate fiber exposure while maintaining matrix integrity, emphasizing the need for precise control over laser parameters. Fracture surface analyses revealed distinct failure mechanisms, ranging from cohesive failure within the adhesive layer to interfacial failure at the fiber-matrix boundary, depending on the ablation conditions. The findings provide clear guidelines for optimizing laser surface treatments to enhance the structural performance of CFRP adhesive joints in practical applications.

ObjectiveThis study aimed to identify the sonographic indicators that predict the ablation rate and efficiency of uterine fibroids during high-intensity focused ultrasound (HIFU) treatment.MethodsIn this retrospective study, we analyzed the clinical data of patients with uterine fibroids who underwent HIFU treatment at Fujian Provincial Hospital between April 2019 and April 2022. Routine abdominal ultrasound examinations were performed to observe potential indicators before the HIFU treatment. After the treatment, enhanced magnetic resonance imaging (MRI) examination was performed within 2 weeks. The fibroid and non-perfused volumes (NPV) were determined, and the ablation rate and energy efficiency factor (EEF) were calculated.ResultsA total of 75 patients (124 uterine fibroids) were included in this study. Uterine fibroids with a larger volume, high echogenicity, elliptical/diffuse leaf shape, and a posterior attenuation band had a higher HIFU ablation rate (p

Introduction. The main disadvantage of using the rate of ablation of urinary stones as a parameter of thulium lithotripsy is the dependence of this parameter on the energy and frequency of laser pulses. Therefore, the results of measurements of this parameter by researchers differ significantly, since they were carried out at different values of the energy and pulse frequency, as well as at different values of the radiographic density of stones.Objective. To develop a universal indicator to assess the specific value of reducing the mass of urinary stones when performing laser lithotripsy.Materials & methods. We have analyzed scientific publications in domestic and foreign specialized publications (2005 to 2023) related to the measurement of urinary stone ablation rate during thulium laser lithotripsy. We used physical methods of estimation of specific values when we developed a universal indicator of specific value of stone mass reduction.Results. Having processed the data, we obtained the average value of the specific indicator of urinary stone mass reduction per unit of pulse energy during thulium lithotripsy in the ‘dusting mode’, equal to 0.059 ± 0.003 mg/J. The article provides a formula for calculating the "pure" time of lithotripsy, as well as examples of calculating the specific indicator of the stone mass reduction and the time of lithotripsy.Conclusion. This value can be used both to evaluate the efficiency of thulium laser lithotripsy and to predict the time of lithotripsy.

Introduction: The high-power holmium: yttrium–aluminum–garnet lasers provide a wide variety of settings for stone disintegration. The aim of this in vitro study is to evaluate the effect of short and long pulse duration on ablation rates on urinary stones. Materials and Methods: Two types of artificial stones were created by BegoStone™ with different compositions (15:3 and 15:6, stone/water ratio). Stones with a 15:3 and 15:6 powder-to-water ratio were defined as hard and soft stones, respectively. Lithotripsy was performed with different laser settings using a custom-made in vitro model consisting of a 60 cm long and 19 mm diameter tube. The ablation rate is defined as the final total mass subtracted from the initial total mass and divided to the time of treatment. Stone ablation rates were measured according to different laser settings with total power of 10W (0,5J-20 Hz, 1J-10 Hz, 2J-5 Hz) and 60W (1J-60 Hz, 1,5J-40 Hz, 2J-30 Hz). Results: Higher pulse rates and higher total power settings were related to higher ablation rates. Short pulse duration was more effective on soft stones, whereas long pulse duration was more effective on hard stones. For the same power settings, the highest energy–lowest frequency combination resulted in higher ablation rate in comparison to the lowest energy–higher frequency combination. Finally, short and long pulse average ablation rates do not differ so much. Conclusion: Regardless of the stone type and pulse duration, utilization of higher power settings with higher energies increased the ablation rates. Higher ablation rates were demonstrated for hard stones using long pulse duration, and for soft stones with short pulse duration.

Introduction: The high-power holmium: yttrium-aluminum-garnet lasers provide a wide variety of settings for stone disintegration. The aim of this in vitro study is to evaluate the effect of short and long pulse duration on ablation rates on urinary stones. Materials and Methods: Two types of artificial stones were created by BegoStone™ with different compositions (15:3 and 15:6, stone/water ratio). Stones with a 15:3 and 15:6 powder-to-water ratio were defined as hard and soft stones, respectively. Lithotripsy was performed with different laser settings using a custom-made in vitro model consisting of a 60 cm long and 19 mm diameter tube. The ablation rate is defined as the final total mass subtracted from the initial total mass and divided to the time of treatment. Stone ablation rates were measured according to different laser settings with total power of 10W (0,5J-20 Hz, 1J-10 Hz, 2J-5 Hz) and 60W (1J-60 Hz, 1,5J-40 Hz, 2J-30 Hz). Results: Higher pulse rates and higher total power settings were related to higher ablation rates. Short pulse duration was more effective on soft stones, whereas long pulse duration was more effective on hard stones. For the same power settings, the highest energy-lowest frequency combination resulted in higher ablation rate in comparison to the lowest energy-higher frequency combination. Finally, short and long pulse average ablation rates do not differ so much. Conclusion: Regardless of the stone type and pulse duration, utilization of higher power settings with higher energies increased the ablation rates. Higher ablation rates were demonstrated for hard stones using long pulse duration, and for soft stones with short pulse duration. [ABSTRACT FROM AUTHOR]

The experimental reproduction of the conditions of pellet injection expected in future large devices being not possible in present day machines, it is mandatory to validate as thoroughly as possible the available ablation models. Among the different points still under discussion, there is the relation between the spectroscopic measurement of the ablation clouds and the local ablation rate. This relation is investigated by coupling an emission model to the time-dependent simulation of ablation clouds with the HPI2 pellet ablation/deposition code. The simulated quantities are the time-evolution of the cloud visible spectrum ( λ = 400–700 nm) and images in different wavelength domains (e.g. $H_{\alpha}, H_{\beta}$ or the continuum centered at $\lambda = 576\,\mathrm{nm}$ ). It is found that the cloud emission is anisotropic, this is particularly the case for H _α and H _β lines, and that the relation between the cloud emission and the ablation rate depends not only on the conditions of pellet injection, but also on the direction of observation. It follows that, in general, it is not possible to estimate the ablation profile from that of an emission line $\left(H_{\alpha}\right.$ or $\left.H_{\beta}\right)$ . The code predictions are compared with corresponding measurements for a welldocumented pellet injected in LHD, showing a good agreement for global values and main trends. The reasons for observed discrepancies are discussed.

We present preliminary stone ablation rate results from an automated bench model using two pulse-modulated Ho:YAG lasers and a thulium fibre laser (TFL) in contact and non-contact modes. Ablation rate was assessed using automated apparatus that moved the laser fibre across flat BegoStone phantoms at a constant stone-to-fibre working distance (WD). Pre-soaked and unsoaked stones were used. A range of powers (20–60 W) was tested at WD of up to 3 mm. In pseudocontact, the prototype Ho:YAG laser produced higher ablation than the reference Ho:YAG laser at all powers tested (p < 0.002), and higher ablation than TFL at 20 W and 40 W (p < 0.001). At distance, ablation rates for the prototype were higher than the reference Ho:YAG laser using pre-soaked stones at WD up to 3 mm (p < 0.001). TFL required the laser fibre to be moved faster (5–12 mm/s) for optimal ablation, compared to 1–3 mm/s for the Ho:YAG lasers. TFL was unable to demonstrate ablation with unsoaked BegoStone. At any given power, similar ablation rates were achievable with all three lasers under optimised conditions. Novel pulse-modulation modes demonstrated higher ablation rates than the reference Ho:YAG laser’s pulse-modulation at a range of powers and WDs. Ablation rate of Ho:YAG lasers decreased linearly with WD whereas the ablation rate of TFL decreased rapidly beyond 2 mm WD. TFL was more affected by scan speed and pre-soaking of stone than Ho:YAG lasers. Ho:YAG lasers may be more practical in clinical settings because they are less dependent on ablation technique. [ABSTRACT FROM AUTHOR]

The nozzle of solid rocket motor (SRM) is easily ablated by high temperature, high pressure, high speed, and corrosive particles, which affects the stability of rocket flight. Therefore, the measurement and characterization of the nozzle ablation rate are helpful in providing some guidance for the design of nozzle material and structure. However, due to the high surface roughness of the composite nozzle after ablation, it is difficult to obtain an accurate ablation rate by contact measurement methods. The 3D laser scanning system is a 3D non-contact measurement technology using structured light technology, phase measurement technology, and computer vision technology. It has the advantages of non-contact, large scanning size, flexibility, and portability. In this paper, a 3D reconstruction of the ablation nozzle is carried out based on the 3D laser scanning system. Additionally, the ablation rate of the nozzle is measured without cutting the actual specimen. Furthermore, the pressure, temperature, and surface convective heat transfer coefficient trends are numerically calculated and compared with the ablation rate. Additionally, the empirical formula between ablation rate and pressure, temperature, convective heat transfer coefficient is obtained empirically by the inversion analysis method. The empirical formula can provide theoretical guidance for nozzle size design and optimization. The results show that the non-contact 3D laser scanning system is a valuable method for reconstructing the model of the ablated nozzle, and the empirical formula of ablation rate can accurately predict the ablation rate of the nozzle. [ABSTRACT FROM AUTHOR]

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The mechanical, thermal and ablation properties of carbon phenolic (C-Ph) composites (Type-I) reinforced with different weight percentages of organo-modified montmorillonite (o-MMT) nanoclay have been studied experimentally. Ball milling was used to disperse different weight (wt) percentages (0, 1,2,4,6 wt.%) of nanoclay into phenolic resin. Viscosity changes to resin due to nanoclay was studied. On the other hand, nanoclay added phenolic matrix composites (Type-II) were prepared to study the dispersion of nanoclay in phenolic matrix by small angle X-ray scattering and thermal stability changes to the matrix by thermogravimetric analyser (TGA). This data was used to understand the mechanical, thermal and ablation properties of Type-I composites. Inter laminar shear strength (ILSS), flexural strength and flexural modulus of Type I composites increased by about 29%, 12% and 7% respectively at 2 wt.% addition of nanoclay beyond which these properties decreased. This was attributed to reduced fiber volume fraction (%Vf) of Type-I composites due to nanoclay addition at such high loadings. Mass ablation rate of Type-I composites was evaluated using oxy acetylene torch test at low heat flux (125 W/cm2) and high heat flux levels (500 W/cm2). Mass ablation rates have increased at both flux levels marginally up to 2 wt.% addition of nanoclay beyond which it has increased significantly. This is in contrast to increased thermal stability observed for Type-I and Type-II composites up to 2 wt.% addition of nanoclay. Increased ablation rates due to nanoclay addition was attributed to higher insulation efficiency of nanolcay, which accumulates more heat energy in limited area behind the ablation front and self-propagating ablation mechanisms triggered by thermal decomposition of organic part of nanoclay.

Laser ablation of galvanized steel at a wavelength of 343, 515 and 1030 nm was compared for single as well as multiple picosecond laser pulses. The characteristics of ablated craters, such as ablation rate, crater shape and chemical composition, in relation to the processing parameters were studied. Surface morphology of the laser ablated craters were characterized with the help of confocal laser scanning microscopy and scanning electron microscopy. Chemical compositional and crystallographic changes were analyzed by energy-dispersive X-ray spectroscopy and electron backscatter diffraction respectively. Three ablation regimes were identified in the ablation process of galvanized steel. For equal amount of fluence, ablation rates are found to increase with decreasing laser wavelength. Analyzing the crater shape and the cross-sectional chemical composition, three possible applications are identified for three different wavelengths when processing galvanized steel with picosecond pulsed lasers, namely coating removal, surface texturing and micro-drilling. [ABSTRACT FROM AUTHOR]

Rationale and Objectives: This study aimed to address the challenge of predicting treatment outcomes for patients with uterine fibroids undergoing high-intensity focused ultrasound (HIFU) ablation. We developed medical-assisted diagnostic models to accurately predict the ablation rates and volume reduction rates, thus assessing both short-term and long-term treatment effects of fibroids., Materials and Methods: For the ablation rate prediction, our study included 348 fibroids, categorized into 181 fully ablated and 167 inadequately ablated fibroids. Using multimodal MRI sequences and clinical characteristics, coupled with data preprocessing steps such as feature extraction, testing, and screening, we constructed an ensemble model for predicting preoperative ablation rates. In the volume reduction rate study, we analyzed 253 fibroids, divided into 142 high-volume responders and 111 low-volume responders. Based on clinical characteristics and T2-weighted image (T2WI) sequences, along with lesion delineation, feature normalization, and other preprocessing steps, we developed an inter-slice information fusion model for predicting preoperative volume reduction rates., Results: The ensemble model demonstrated an accuracy of 0.800 and an area under the curve (AUC) of 0.830 on the test set, while the inter-slice information fusion model achieved an accuracy of 0.808 and an AUC of 0.891. Both models showed superior predictive performance compared to existing models., Conclusion: The ensemble and inter-slice information fusion models developed in this study exhibit robust predictive capabilities, offering valuable support for clinicians in selecting patients for HIFU treatment. These models hold potential for enhancing patient outcomes through tailored treatment planning., Competing Interests: Declaration of Competing Interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.)

The nozzle of solid rocket motor (SRM) is easily ablated by high temperature, high pressure, high speed, and corrosive particles, which affects the stability of rocket flight. Therefore, the measurement and characterization of the nozzle ablation rate are helpful in providing some guidance for the design of nozzle material and structure. However, due to the high surface roughness of the composite nozzle after ablation, it is difficult to obtain an accurate ablation rate by contact measurement methods. The 3D laser scanning system is a 3D non-contact measurement technology using structured light technology, phase measurement technology, and computer vision technology. It has the advantages of non-contact, large scanning size, flexibility, and portability. In this paper, a 3D reconstruction of the ablation nozzle is carried out based on the 3D laser scanning system. Additionally, the ablation rate of the nozzle is measured without cutting the actual specimen. Furthermore, the pressure, temperature, and surface convective heat transfer coefficient trends are numerically calculated and compared with the ablation rate. Additionally, the empirical formula between ablation rate and pressure, temperature, convective heat transfer coefficient is obtained empirically by the inversion analysis method. The empirical formula can provide theoretical guidance for nozzle size design and optimization. The results show that the non-contact 3D laser scanning system is a valuable method for reconstructing the model of the ablated nozzle, and the empirical formula of ablation rate can accurately predict the ablation rate of the nozzle.

Organo-Montmorillonite (o-MMT) nanoclay added polybenzoxazine resin (type I composites) were prepared with varying amounts of clay (0, 1, 2, 4 and 6 wt %). Clay dispersion, changes in curing behaviour and thermal stability were assessed in type I composites. Findings from these studies of type I composites were used to understand thermal stability, mechanical, and mass ablation rate behaviour of nanoclay added carbon fiber reinforced polybenzoxazine composites (type II). Interlaminar shear strength and flexural strength of type II composites increase by 25% and 27%, respectively at 2 wt% addition of clay. An oxy-acetylene torch test with a constant heat flux of 125 w/cm2 was used to investigate mass ablation rate of type II composites. The ablation rate has increased as the weight percentage of clay has increased. This is contradicting to type I composites with up to 6 wt% clay and type II composites with up to 4 wt% clay, which have improved thermal stability. The microstructure of the ablated composites was examined using scanning electron microscopy. Increased ablation rates are due to the reaction of charred matrix with nanoclay, which exposes bare fibers to the ablation front, resulting in higher mechanical erosion losses. [ABSTRACT FROM AUTHOR]

This study presents a detailed picosecond LIBS analysis of WTa coatings on Molybdenum substrate with varying layer thicknesses for fusion relevant applications. Ps-LIBS is performed on three WTa layers; two without deuterium (∼ 7 μm thickness) and one with deuterium (∼ 1 μm thickness). The LIBS measurements are conducted under argon gas flow at 5 ± 0.2 mbar pressure with different laser pulse energies (1 mJ, 3 mJ) and 100 spectra are recorded consecutively at one spot on the sample for different set of gate delay/gate width (200/200 ns, 300/300 ns, 450/450 ns). The obtained LIBS and Glow-Discharge Optical Emission Spectroscopy (GDOES) depth profiles are compared with the confocal microscopic measurements showing good agreement. Additionally, the ablation rate and layer thickness are calculated for different experimental conditions. The Calibration-Free LIBS approach is used for elemental analysis and the results are compared with GDOES results. The capability of ps-LIBS to quantify Ta in WTa alloy is explored for 2 at.% of Ta. However, due to higher ablation rate of laser and thin coating in WTaD sample, the layer is irradiated in few laser pulse and therefore, CF-LIBS analysis is not performed for it. [Display omitted] • ps LIBS, depth profile analysis of fusion related samples WTa(D)/Mo. • LIBS at 5 mbar Ar pressure, equal D and GT (200–450 ns), pulse energy (1, 3 mJ). • GDEOS depth profile analysis - WTa (∼ 7 μm thickness) and WTaD (1 ∼ μm thickness). • Depth analysis comparison and ablation rate (LIBS, GDOES, Confocal Microscopy) • Successful CF analysis for 10 at.% and 2 at.% of Ta. [ABSTRACT FROM AUTHOR]

In this study, for the first time, ZrC coating was deposited on SiC coated graphite by optimized atmospheric plasma spray (i.e. solid shielding shrouded plasma spray (SSPS)) method. Then SSPS-ZrC coatings were compared with the atmospheric plasma spray APS-ZrC coatings. The results indicated that the the SSPS-ZrC coated sample had lower porosity compared with APS-ZrC coating (3% and 7.5% respectively) and the ablation test revealed that the linear and mass ablation rates of the ZrC coating applied by APS method were 3.7×10−3 mm.s−1 and 22×10−3 g.s−1, while those for SSPS coating were 2.2×10−3 mm.s−1 and 14×10−3 g.s−1, respectively. The results showed that applying the ZrC coating with the SSPS method can improve the ablation resistance of the equipment used in harsh conditions, significantly. It is attributed to the formation of a continuous zirconia (ZrO2) layer on the surface during the ablation test of the ZrC coating. [ABSTRACT FROM AUTHOR]

The mechanical, thermal and ablation properties of carbon phenolic (C-Ph) composites (Type-I) reinforced with different weight percentages of organo-modified montmorillonite (o-MMT) nanoclay have been studied experimentally. Ball milling was used to disperse different weight (wt) percentages (0, 1,2,4,6 wt.%) of nanoclay into phenolic resin. Viscosity changes to resin due to nanoclay was studied. On the other hand, nanoclay added phenolic matrix composites (Type-II) were prepared to study the dispersion of nanoclay in phenolic matrix by small angle X-ray scattering and thermal stability changes to the matrix by thermogravimetric analyser (TGA). This data was used to understand the mechanical, thermal and ablation properties of Type-I composites. Inter laminar shear strength (ILSS), flexural strength and flexural modulus of Type I composites increased by about 29%, 12% and 7% respectively at 2 wt.% addition of nanoclay beyond which these properties decreased. This was attributed to reduced fiber volume fraction (%Vf) of Type-I composites due to nanoclay addition at such high loadings. Mass ablation rate of Type-I composites was evaluated using oxy acetylene torch test at low heat flux (125 W/cm2) and high heat flux levels (500 W/cm2). Mass ablation rates have increased at both flux levels marginally up to 2 wt.% addition of nanoclay beyond which it has increased significantly. This is in contrast to increased thermal stability observed for Type-I and Type-II composites up to 2 wt.% addition of nanoclay. Increased ablation rates due to nanoclay addition was attributed to higher insulation efficiency of nanolcay, which accumulates more heat energy in limited area behind the ablation front and self-propagating ablation mechanisms triggered by thermal decomposition of organic part of nanoclay. [ABSTRACT FROM AUTHOR]

Laser turning with ultra-short laser pulses provides the possibility of manufacturing rotationally symmetric geometries, even of hard to machine materials as fused silica, down to a micrometer scale. In this laser micro machining approach, the laser beam is oriented perpendicularly to the rotational axis and tangentially to the material, whereas the target geometry is realized by moving the constantly rotating specimen according to the specified geometry under the focused laser spot. Due to the friction-less laser ablation it is possible to realize a turning process in fused silica without the use of a contacting tool and therefore without causing mechanical tensions in the work piece. The processing head focuses the laser to a calculated spot size of 18 µm in diameter and the applied processing gas pressure assists in removing the ablated material. In this study, femto-second laser turning of fused silica with a diameter of 3.7 mm is investigated. The influence of the applied pulse energy is stated and the use of a trepanning optic during the turning process is characterized. Furthermore, comprehensive parameter studies in order to optimize roughness and to find the maximum achievable ablation rate are shown. Limited by the mechanical speed of the rotational axis, the highest feasible ablation rate is 19.5 mm³/min. A roughness of Ra 0.65 µm are demonstrated. [ABSTRACT FROM AUTHOR]

We report on the effect of different transversal beam shapes on the efficiency of ablation processes and the resulting surface characteristics. A possibility to efficiently apply ultrashort pulsed lasers with high average power is beam shaping. By using a cooled reflective based liquid crystal spatial light modulator to generate different spot distributions, it is possible to spatially allocate the available power to avoid excessive high fluences. In our experiments, we determine the optimal fluence to ablate the maximum volume per watt to be in the range of 0.2-0.4 J/cm². Based on this fluence, we increase the number of spots from one to a maximum of twenty to ablate steel in a multilayer scanning-based process. In this context, we examine the influence of different separation distances between the spots on the ablation efficiency and roughness. Subsequently to these investigations, we develop an efficient roughing process with higher ablation rates and a nearly constant roughness. [ABSTRACT FROM AUTHOR]

To avoid excessive tissue removal and collateral damage, the high‐power density laser is apt for dental surgery also need to have high precision. For high‐precision dental surgery with minimal tissue damage, the present work frames a method to predict laser ablation profile based on surface morphology and chemical composition of dentin. The surface morphology and chemical composition were studied on different dentin samples using scanning electron microscope (SEM) and Energy Dispersive X‐ray Analysis (EDAX), respectively. The key laser ablation parameters (ω0, Deff, and Fth) were determined by laser irradiation study using 800 nm, Ti:Sapphire femtosecond laser at processing condition of 100 fs, 10 kHz and 10 mm/s. The dentin samples show a strong linear correlation between physiochemical characteristics and laser ablation parameters. The surface morphology exhibits a negative linear correlation with threshold fluence, whereas the converse is true for chemical composition. The laser ablation parameters of a random dentin sample are derived from the knowledge of linearity data. From the obtained laser ablation parameters, the complete theoretical ablation profile is constructed and validated with experimental ablation profile. Even though the surface morphology of dentin shows high linearity, the concentration of Ca and P can be used as the most feasible probe in clinical settings. Furthermore, the laser ablation rate and ablation efficiency are predicted by the method to optimize the laser processing condition for any specific teeth. The versatility of the method overcomes the problem of heterogeneity on various teeth and simplifies the method of finding optimal laser processing condition for immaculate laser surgery. [ABSTRACT FROM AUTHOR]

A two-dimensional numerical model considering recoil pressure and Hertz-Knudsen ablation rate was established on the foundation of the laser remelting model to investigate the influence of laser processing parameters on crater feature and melted zone, and it was verified through experiments. The temperature and flow velocity distribution of the molten pool during the formation of the crater were analyzed. The results showed that the ablation velocity could be considered under a higher laser peak power density or higher pulse width due to the metal evaporation caused by heat accumulation. The depth and diameter of the crater were significantly affected by laser peak power density and laser pulse duration. Simultaneously, the height of the edge bulge decreased with the increase in pulse duration after 1.5 ms, and the growth rate of central depth was more rapid than that of edge bulge height with the increase of laser peak power density. In the texture with the same depth, a larger melted zone could be obtained with a longer laser duration than the higher peak power density. [ABSTRACT FROM AUTHOR]

We report on the fabrication of rotationally symmetrical geometries with ultrashort laser pulses impinging the constant rotating workpiece tangentially. This particular micro machining of geometry is referred to as laser turning, upon which the laser beam is, in general, oriented perpendicularly to the rotational axis and tangentially to the work piece. The target geometry is realized by moving the constantly rotating specimen according to the specified geometry along the focused laser spot. In contrast to mechanical turning, laser turning induces a minimized amount of lateral forces through friction that might deteriorate the geometry. In this study, laser turning is examined for stellite as a function of pulse energy and pulse length in the range between 240 fs and 10 ps. Shorter pulse lengths and higher pulse energies increase the achievable ablation rate, while in the pulse length regime of below 1 ps lower roughness is achieved. With a maximum ablation rate of 1.27 mm?/min and a minimum roughness of 0.17 µm, laser turning combines both, fast processing and high surface quality. [ABSTRACT FROM AUTHOR]

Ultrashort-pulsed lasers allow a precise, low thermal damage and material independent micro processing. However the full potential of ultrashort pulsed lasers with their currently available laser power cannot be used due to limitations in ablation rate per pulse keeping the high quality in ablation. Beside scaling up by multi spot technology, the application of ultrashort pulse bursts is another possibility to increase the ablation rate. In this paper a newly developed ultrashort pulsed laser with a seeder frequency of 500 MHz has been investigated in cylinder micro engraving application. The laser offers the possibility to control the shape of a burst sequence in amplitude and timing. The influence of the pulse sequence on the ablation rate and quality in combination with the different metals has been investigated. The pulse burst frequency has been changed between 1 - 5 MHz with a scanning speed of 16 m/s. The pulse to pulse overlap at the work piece was adjusted from 0% to 90%. Comparing to single pulse ablation the ablation rate with GHz pulse burst is increased by factor 2.2. The surface roughness is Ra = 0.38µm with GHz pulse burst, whereas the roughness is R a = 1.423 µm with single pulse. In this paper experimental ablation results and quality aspects will be presented and discussed. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate the efficacy of polymerization of composite resin photocured with different wavelengths and irradiation times by means of ablation techniques with Er:YAG laser. Materials and Methods: A microhybrid composite resin was photocured with argon laser (Coherent, Innova 200-20) at 400 mW/cm2 for 15, 40, 60, 300, and 900 s. The wavelengths used were 476.5, 488.0, 502.7, and 514.5 nm. The samples were ablated with Er:YAG laser at three energy levels (100, 200, and 300 mJ), a fixed frequency of 2 Hz, and water flow of 0.12 ml/s for 10 s. The ablated volume was measured to quantify polymerization. Two-way ANOVA and Tukey's test were used to analyze the data. Results: The results showed a more effective polymerization for the wavelength of 476.5 nm with low irradiation times (15, 40 and 60 s). Longer photoactivation (300 and 900 s) and a wavelength of 488.0 nm resulted in less ablation. Conclusion: The ablation techniques with Er:YAG laser can be used for evaluation of efficacy of polymerization of the composite resin and showed that the wavelengths of 476.5 and 488.0 nm provided the best polymerization rate. [ABSTRACT FROM AUTHOR]

Purpose: To compare the depth and volume of cavities produced by ablation on bovine bone tissue using different Er:YAG laser parameters. Materials and Methods: A bovine femur was cut in blocks and wet polished with 600-grit sandpaper. Different energies per pulse (100 mJ, 300 mJ, and 500 mJ) and different frequencies (5 Hz, 10 Hz, and 15 Hz) were used to create microcavities within a 10-s irradiation time. The samples were analyzed under an optical microscope (40X) and SEM for a better definition of the cavities and their features. The ablated volume was calculated and statistically analyzed with Kruskal-Wallis and Dunn tests. Results: The ablation rate in many groups showed significant differences up to 5%, where the energy per pulse was the only significant variable. As energy per pulse increased, so did the ablation rate. Morphological analysis showed differences in the homogeneity of the microcavities. Conclusions: Er:YAG laser is able to promote cold interaction, suggesting a precise tool for bone ablation. [ABSTRACT FROM AUTHOR]

Purpose: To compare two blue LED (light emitting diode) sources in terms of curing efficacy as determined by the ablation resistance of light-cured composite resins when irradiated with an Er:YAG laser. Materials and Methods: A hybrid composite resin was photocured with two blue LED light sources at 105 mW/cm² and 1000 mW/cm². Composite tablets were photocured for two different irradiation times: 5 s and 40 s. A focused Er:YAG laser at five energy levels per pulse (100 to 500 ml), a fixed frequency of 10 Hz, and water flow of 0.46 ml/s, was used for 10 s to ablate the cured composite resin. Results: The obtained values were plotted to allow a comparative observation of the removed material volume as a function of fluence. The higher the energy per pulse, the higher the ablation rate; however, above 300 ml, the photocuring time and LED intensity were important factors influencing curing efficacy. Conclusions: The lowest intensity parameter allowed the largest ablation rate on material photocured for 5 s, while the highest intensity produced the same result on material photocured for 40 s. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this work was to investigate the ablation rate and the morphological aspects of three composite resins using Er:YAG laser irradiation, Materials and Methods: Three different types of composite resins were chosen (microfilled, hybrid, condensable) regarding their chemical and structural composition. Composite tablets were irradiated with an Er:YAG laser at different energy levels per pulse (100, 200, 300, and 400 mJ). The diameter and depth of each composite resin tablet were measured, as was the microcavity produced by laser ablation, and from this the overall volume removed was calculated. Observations of morphological aspects were performed using electron microscopy. The ANOVA and Tukey tests were used to statistically analyze the volume results. Results: The only variable that influenced the ablation rate of the composite resins tested was the energy level per pulse. Conclusion: Examining the basic features of laser ablation of composite resin represents the first step to understanding the mechanism of composite resin ablation by Er:YAG laser and the numerous differences due to resin composition and structure. [ABSTRACT FROM AUTHOR]

Understanding laser ablation behaviors of different target materials is essential for optimum laser parameters, external reference materials selection, as well as for data quality assurance. In this study, ablation behaviors of a 193nm ArF excimer laser for silicate glasses, common minerals, and powder pellets were investigated. Ablation rates influenced by laser parameters (including spot size, energy density, and laser frequency) were evaluated. Topographic images of craters generated during ablation illustrate that glasses and most minerals have controllable ablation behaviors, except for quartz. The worse ablation behavior of quartz may be ascribed to the micro-fluid inclusions, which could result in the overheating effect in laser pits. In general, powder pellets have worse ablation behaviors, but the increase of tableting pressure or reducing the particle grain size could improve the ablation behaviors. Ablation rates gradually decrease if the ablation depth is larger than 1.5 times of the spot size. The maximum ablation depth can reach twice the spot size when the energy density is 3.0 J/cm2 for the RESOlution M-50 laser system). Ablation rates increase with the increase of laser energy density, but ablation rates are not affected by the laser frequency (2-20 Hz). Ablation rates are specific to the individual substrates. In conclusion, the ablation rate data of 43 substrates, in which ablation rates of powder pellets are larger than glasses and minerals, whereas those of carbonates and sulfides are larger than silicate minerals, and those of NIST glasses are larger than geological glasses.

The results of the experimental study of the structural carbon fiber reinforced plastic (CFRP) erosion resistance applied to gas turbine engine structural elements are presented. A methodology for characterizing the process of gas abrasive wear of thin-walled structures made of polymer composite materials has been developed. The factors are found that determine the level of the abrasive effect of dust and gas mixture formed at the take-off and landing. A criterion for material erosion resistance assessment is presented. [ABSTRACT FROM AUTHOR]

Machining using ultrashort laser pulses is vastly used in science, technology and medicine. However, how to use the expensive laser irradiation efficiently is an important and still open question. To find the highest ablation efficiency, laser processing parameters, such as: pulse repetition rate and fluence have to be optimised. Moreover, forming two-and-a-half-dimensional (2.5D) structures on curved surfaces is in high interest because of the applicability of bio-inspired functional surface mimicking. In this work, experiments were carried out to find the highest ablation efficiency by machining cylindrical copper samples at different pulse energies and repetition rates. Optimal parameters were used for blade-riblet structuring on a cylindrical copper sample. The calculated ablation efficiency corresponds well with the commonly known theoretical model and deviations were explained. • Laser machining process of cylindrical samples was optimised. • The highest ablation efficiency was with fluence of 7 J/cm2 at 602 kHz. • Highest ablation efficiency interval yielded highest processing quality. • Surface structuring, mimicking shark-skin-like riblets, was demonstrated. • Ablation rate of 3.5 mm3/min and ablation efficiency of 2.3 μm3/μJ were reached. [ABSTRACT FROM AUTHOR]

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To predict the laser ablation profile on dental hard tissue which will enable the user to optimize laser parameters so as to carry out the laser treatment with minimal tissue damage. The present study constructs a mathematical model to predict the ablation profile based on Gaussian beam distribution of laser intensity and correlates the model with experimentally obtained ablation parameters (effective Gaussian beam radius, ablation threshold fluence, and effective energy penetration depth). To obtain the ablation parameters, laser ablation experiments were carried out on dental hard tissues using Ti:Sapphire femtosecond laser (800 nm, 100 fs, 10 kHz). The method is further extended to predict the ablation rate and efficiency as well. The profile predicted from the mathematical model is compared with that of experimental results. It is found that the predicted ablation profile agrees well with the experimental profile for both enamel and dentin except a slight deviation at higher fluence for dentin. The calculated ablation rate is comparable to that of experimental results whereas for ablation efficiency appreciable deviation is observed in the case of dentin. The model succinctly predicts the ablation profile, ablation rate, and ablation efficiency which will enable to perform dental surgery at optimized laser processing conditions with high precision thus reducing the tissue damage appreciably. Once the details of lesion are known through proper diagnostic tools, the method enables the user to readily obtain optimum laser parameters. It can be used as a handy reference for dentists to perform damage-free surgery, ensuring quicker healing. [ABSTRACT FROM AUTHOR]