•High power fiber laser was feasible to cut CFRP laminate with high efficiency.•The effect of cutting parameters on thermal defects were analyzed.•Two methods were proposed to characterize/quantify ...HAZ.•Full-field strain distribution was analyzed with DIC technique.•Numerical simulation of strain distribution was in line with DIC analysis.
High power fiber laser cutting of CFRP composites has been proven to be feasible with high efficiency, while there are still several challenges due to different carbon fiber-epoxy resin properties and sensitivity to thermal heat. This paper studied the influence of processing parameters on machined hole quality and quasi-static tensile behavior of unidirectional CFRP laminate with open hole (6.0 mm in diameter) following fiber laser cutting process. Hole surface morphology was analyzed using optical microscope and scanning electron microscopy. The area of heat affected zone and defect factor were quantified to understand the effect of machining parameters on thermal defect. It was found that both cutting speed and laser power were statistically significant with respect to HAZ recorded at hole entry, while cutting speed was the only significant factor for HAZ observed at hole exit. The full-field strain distribution during tensile loading was characterized using 3D digital image correlation (DIC) technique. Surprisingly, laser processing parameters showed limited effect on surface strain distribution (εxx, εxy, εyy) during tensile loading. Some highly localized strain zones were observed on the tangent of transverse edge of the hole, corresponding to final failure mode of splitting due to inevitably slight shear force during tensile loading and weak interface strength between carbon fiber and epoxy resin. Numerical simulation results of strain distribution were in good agreement with the DIC analysis.
How to safely separate explosives, propellants, detonators and other energetic materials from the large number of decommissioned munitions scheduled to be retired has always been challenging. In this ...work, we proposed a femtosecond laser to cut metal shells of discarded ammunition and verify the safety of laser irradiation of energetic materials. First, triaminotrinitrobenzene (TATB), octogen (HMX) and the metal shell of 95 tungsten were irradiated by the single-point laser to explore the ablation properties of the materials. Then, the effect of femtosecond laser cutting speed on the surface groove morphology of energetic materials and 95 tungsten was discussed. The laser-induced damage threshold and peak power density of the TATB, HMX and 95 W were determined. Besides, we adopted the pump-probe ultrafast imaging technique to reveal the ultrafast dynamic responses of metal shells and explosives irradiated by femtosecond lasers. Further, based on the high-speed imaging system, ultrafast dynamic images of the interface between the metal shell and the explosive ablated by femtosecond lasers were obtained, which provided an intuitive insight into the phase characteristics of the ablation region and the scale and intensity of the shock wave caused by the ejection.
•The feasibility and safety of femtosecond laser cutting of decommissioned explosives has been verified.•HMX is more stable than TATB without significant thermal effect.•Femtosecond laser fluence between 0–12.74 J/cm2 is a safe working range for cutting 95 tungsten-bonded TATB and HMX.•The speed of laser cutting is lower than 0.5 mm/s to achieve complete removal of laser ablation products from processed trenches.•Pump-probe techniques and high-speed photography were adopted to reveal the interfacial interaction mechanism.
Laser cutting of AL6061T6 alloy was conducted to investigate the effects of process parameters on cutting region temperature and cutting edge quality. The process variables are including cutting ...speed, laser power, sheet thickness and nozzle standoff distance. It is found that measuring the cutting region temperature could effectively represent the variation of cutting conditions. The results show that the laser power is the most influential factor on the cutting region temperature and cutting edge quality when the sheet thickness increases. Furthermore, simultaneous selection of both laser power and cutting speed could be effective by considering creation of appropriate temperature of cutting region. The nozzle standoff distance plays a crucial role on changing gas flow dynamic and laser power density, which results in an evident temperature variation of cutting region.
For the microfluidic chip, the surface roughness of the chamber sidewall is an important parameter in estimating its quality. In this work, the chambers of the polymethyl methacrylate (PMMA)-based ...microfluidic chip were fabricated by CO
2 laser cutting, and then the surface roughness of the sections cut using different laser parameters and ambient temperature was studied by a non-contact 3D surface profiler. Our observation shows that the surface roughness results primarily from the residues on the laser-cut edge, which are produced by the bubbles bursting. To reduce the surface roughness of the cut section, a new approach is proposed, that is preheating the PMMA sheet to a suitable ambient temperature during laser processing. The results indicate that at a preheat temperature of 70–90
°C, the surface roughness resulting from the cut would be reduced. In our experiment, the best result was that the arithmetical mean roughness is
R
a
=
100.86
nm when the PMMA sheet was heated to 85
°C.
•The spot and plume are used as evaluation indicator to estimate the ablation conditions.•Effects of process parameters on ablation and HAZ are analyzed.•The relationship between ablation and HAZ is ...revealed.•The defects in the HAZ can be judged by the ablation phenomenon.
Laser technology is widely used in the processing of various composite materials. Ablation and heat affected zone (HAZ) are important phenomena in laser processing, but the relationship between ablation and HAZ defects has not been deeply researched. In this paper, laser cutting of glass fiber reinforced polymer (GFRP) was investigated by means of fiber laser. To assess the influence of the process parameters on ablation and HAZ, four main parameters were selected as the experimental factor in single factor experimental study. The degree of material ablation was judged according to the phenomenon of light spot and plume in processing, and the width of HAZ was measured by optical microscope. The experimental analysis shows that the HAZ defects by the ablation phenomenon can be evaluated to reveal the relationship between ablation and HAZ. On this basis, improving the ablation condition is helpful to reduce the formation of HAZ.
•A cutting study with a high power ytterbium-doped fiber laser was conducted for application to dismantling of nuclear facilities.•Stainless steel and carbon steel plates of various thicknesses were ...cut at a laser power of 6-kW.•Despite the use of a low output of 6-kW, the cutting was successful for both stainless steel and carbon steel plates up to 100 mm in thickness.•The cutting capability was ∼16.7 mm by kW which is much higher than commonly known value, and the maximum cutting speeds were faster for the same thicknesses than those from other groups.
A cutting study with a high-power ytterbium-doped fiber laser was conducted for the dismantling of nuclear facilities. Stainless steel and carbon steel plates of various thicknesses were cut at a laser power of 6-kW. Despite the use of a low output of 6-kW, the cutting was successful for both stainless steel and carbon steel plates of up to 100 mm in thickness. In addition, the maximum cutting speeds against the thicknesses were obtained to evaluate the cutting performance. As representative results, the maximum cutting speeds for a 60-mm thickness were 72 mm/min for the stainless steel plates and 35 mm/min for the carbon steel plates, and those for a 100-mm thickness were 7 mm/min for stainless steel and 5 mm/min for carbon steel plates. These results show an efficient cutting capability of about 16.7 mm by kW, whereas other groups have shown cutting capabilities of ∼10 mm by kW. Moreover, the maximum cutting speeds were faster for the same thicknesses than those from other groups. In addition, the kerf widths of 60-mm and 100-mm thick steels were also obtained as another important parameter determining the amount of secondary waste. The front kerf widths were ∼1.0 mm and the rear kerf widths were larger than the front kerf widths but as small as a few millimeters.
•For the first time, a keyhole mode cutting is achieved for CFRP materials using a long-pulse nanosecond laser.•A high-quality machined surface can be produced with a limited heat-affected zone and ...little fiber pull-out.•Short-duration Q-Switch mode results in ineffective material removal for CFRP.•Effects of laser parameters on cutting surface integrity are determined.
The machining performance of a high-energy nanosecond pulse laser with a near-infrared wavelength is investigated for carbon fiber-reinforced polymer (CFRP) with two different fiber arrangements. This research work demonstrates for the first time that a keyhole mode cutting can be achieved for CFRP materials using a high-energy nanosecond pulse laser of a Long Pulse mode (120 ns). Specifically, it is shown that the short-duration Q-Switch mode (8 ns) results in ineffective material removal for CFRP, despite much higher peak laser power intensity than the Long Pulse mode. In Long Pulse mode, multi-pass straight line and contour cutting experiments are further performed to investigate the effect of laser processing parameters and resultant machined surface integrity. Plasma absorption effects using both pulse modes are discussed. The results show that a 2.2 mm thick cross-ply CFRP panel can be cut through using as few as 6 laser passes, and a high-quality machined surface can be produced with a limited heat-affected zone and minimal fiber pull-out using Argon assist gas. The successful outcomes from this work provide the key to enable efficient CFRP laser machining using high-energy nanosecond pulse lasers, and offer insight into the unique energy absorption mechanisms for CFRP laser machining.
Motivated by the need to enhance the kerf quality during cutting of Poly(methyl methacrylate) (PMMA) sheets using pulsed CO2 laser beam, this study presents an experimental investigation and ...optimization of laser cutting parameters including cutting speed, assisted gas pressure, laser beam power, and sheet thickness. The kerf quality characteristics including the top kerf width, bottom kerf width, and kerf taper have been considered as the process responses and have been measured using polarized light microscope. The experiments were designed and planned using Taguchi L18 orthogonal array with a mixed design. The effects of different cutting parameters on the kerf characteristics have been statistically analyzed using analysis of variance technique (ANOVA). The obtained results revealed that any increase in cutting parameters will result in increasing the top and the bottom kerf widths, while increasing cutting speed or laser power results in increasing the kerf taper. Second order regression models have been developed to model different kerf characteristics as functions of the process parameters. Genetic algorithm (GA) has been used to select the optimal cutting parameters using the developed regression model as an objective function to minimize the kerf taper. A considerable improvement in kerf quality has been achieved and the obtained results have been verified using confirmation experiments. The application of the proposed approach is capable to reduce the kerf taper from 1.92° to 0.02° while maintaining the minimum kerf width at a reasonable value (less than 0.5 mm).
Display omitted
•High-power fiber laser was feasible to cut 25 mm thick mild steel plate with high efficiency.•The effect of process parameters on the kerf taper were analyzed.•The effect of line ...energy on the kerf taper was analyzed.•The kerf taper’s model was established with regression analysis.•The formation mechanism of the kerf taper was studied.
The laser cutting capacity has increased significantly in recent years, owing to the rising power of fiber lasers. Meanwhile, considerable emphasis is being paid to the quality of high-power laser cutting, particularly the issue of thick plate kerf taper. However, the mechanism by which the kerf taper is formed and the effect of process parameters on the kerf taper are rarely examined in detail when cutting a thick plate with a high-power fiber laser. The purpose of this study is to conduct a series of cutting tests using a 12-kW continuous-wave multimode ytterbium-doped fiber laser. The single factor experiment approach is utilized to determine the effect of each process parameter (stand-off distance, cutting speed, defocus amount, and auxiliary gas pressure) on the kerf taper of 25 mm thick mild steel. The Taguchi method of L25 orthogonal array is used to design the laser cutting experiment, and analysis of variance was used to determine the significant factor impacting the kerf taper. The regression model for the kerf taper was created using the experimental data. Further, the experimental study was used to analyze the mechanism by which the kerf taper of the thick plate was formed.
PDF
