•An underwater laser cutting study was performed for dismantling application in nuclear power plants.•Stainless steel specimens were cut up to 100 mm in thickness using a fiber laser with a power of ...9 kW.•Excellent performance was obtained in terms of cutting speed and thickness even in an underwater environment.•The results obtained in this study are expected effectively used in actual nuclear power plant decommissioning sites.
For dismantling nuclear power plants, an underwater cutting study was conducted using a high power fiber laser. With a laser power of 9 kW, cutting tests were performed on stainless steel with a thickness of 50–100 mm. For this study, a waterproof cutting head consisting of a focusing element with a long focal length of 600 mm and a supersonic nozzle was used for high cutting efficiency. For thicknesses of 70 mm or less, it was possible to cut only with a single supersonic nozzle, while for a thickness of 80 mm or more, an initially pierced specimen or a double nozzle was required for successful cutting. Through these techniques, we were able to perform the cutting underwater up to a thickness of 100 mm. Furthermore, the kerf widths were as small as 1–2 mm, the amount of secondary waste will likely be small, which will reduce waste disposal costs.
This paper investigates the cyclic behaviour of a novel typology of steel beam‐to‐column connection made by welding circular hollow section (CHS) columns and through I‐beams. In fact, due to the ...novelty of this configuration and the lack of design equations in the current codes, the application of this innovative solution is limited in common practice.
The LASTEICON research project has recently investigated the main technological issues related to the manufacturing process and the joint's flexural resistance. Additionally, at the University of Salerno, studies on this joint began a few years ago, focusing on the characterisation of its bending response within the framework of the component method approach. Therefore, experimental, numerical and analytical activities have led to defining the joint's main components and proposing formulations able to predict the initial stiffness and the chord failure resistance. However, the proposed approach concerns the investigation of the monotonic behaviour of the joint, leaving the investigation of its cyclic response still unexplored.
To fill this gap, the cyclic flexural response of connections with CHS columns and through I‐beams is assessed in this paper, starting from the knowledge of the monotonic and cyclic behaviour of the main components of the connection.
•The feasibility of high-power fiber laser cutting of thick SiCp/Al composite using single-pass strategy was investigated.•Surface morphology and cross-section characteristics were analyzed to ...understand material removal mechanisms.•Various thermal defects were qualified to study the influence of processing parameters on machining quality.•The formation mechanisms of different thermal damage during fiber laser cutting SiCp/Al composite were explained in details.
Due to the introduction of ceramic reinforcement, the physical properties and machinability of SiCp/Al composites are greatly different from the metallic ones. High-power continuous wave fiber laser makes it possible to process SiCp/Al composites with high efficiency. In this work, the feasibility of high-power fiber laser cutting of 5.0 mm thick SiCp/Al composites was studied using design of experiments (DOE). The effects of laser power (1000–4000 W), cutting speed (500–2000 mm/min) and assist gas (N2 and O2) on kerf geometry and defect characterization were investigated. Results showed that high laser power and low cutting speed generated relatively higher kerf width on the entry surface, and the kerf width exhibited a slightly higher level around ∼ 2.0% when O2 was applied in comparison to the results from N2 group. Different morphology was observed on machined surfaces including multi-directional striation, vertical striation and slant striation. The width of HAZ increased along the direction of laser beam, and reached the maximum value at egress with the value up to 1115 μm. The SEM and EDX spectra study showed that the effect of oxygen on the subsurface was limited, and there was no metallurgical reaction between the matrix and SiC particles during laser cutting process.
The operating pressure of gas-assisted laser cutting and the resulting exit jet pattern is one of the most important process parameters in high-pressure laser cutting. Many studies have been done to ...illustrate the effect of this parameter on both laser cutting quality and laser cutting capability. However, most of these studies have been done using conical nozzles. In this paper, the exit jet from supersonic nozzle has been studied, analyzed, and simulated under three different operating conditions, namely desired design, under-expansion, and over-expansion to illustrate the effect of these operating conditions on the dynamic characteristics of the exit jet. Quasi 1-D gas dynamics theory has been used to calculate the desired design operating condition, and then an axisymmetric 2-D model has been created using the OpenFOAM
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Computational Fluid Dynamics (CFD) toolbox to simulate the gas-assisted laser cutting flow through the modeled supersonic nozzle. Finally, the proposed simulations have been validated by comparing the results with experimental observations reported in previous literature. The effect of the turbulent viscosity has been considered through the proposed model to better simulate real conditions. Moreover, the model has been optimized to be effectively used for engineering purposes. The simulation results are qualitatively consistent with the reported experimental measurements and they demonstrate that in the case of supersonic nozzles, the exit jet pattern is characterized by high uniformity, absence of Mach disks, and bounded shape for a long distance especially under the desired design operating conditions.
Heat affected zone (HAZ) of the laser cutting process may be developed based on combination of different factors. In this investigation the HAZ forecasting, based on the different laser cutting ...parameters, was analyzed. The main goal was to predict the HAZ according to three inputs. The purpose of this research was to develop and apply the Extreme Learning Machine (ELM) to predict the HAZ. The ELM results were compared with genetic programming (GP) and artificial neural network (ANN). The reliability of the computational models were accessed based on simulation results and by using several statistical indicators. Based upon simulation results, it was demonstrated that ELM can be utilized effectively in applications of HAZ forecasting.
•Heat affected zone (HAZ) of the laser cutting process.•HAZ forecasting based on the different laser cutting parameters.•To analyze the influence of three inputs on the HAZ.•To predict the HAZ.•Extreme Learning Machine (ELM) to predict HAZ.
Cutting characteristics such as heat affected zone (HAZ), top and bottom kerf widths, ratio of top kerf width to bottom kerf width, and dross height are so reliant on process condition in the laser ...cutting of polymer materials. In the present research, a 60 (W) continuous wave CO2 laser cutting machine was used for cutting the extruded samples of Polystyrene sheet with the thickness of 3 mm. The experiments were designed based on the statistical method, design of experiments. Three variables considered as process parameters including laser power (in three level of 60, 70 and 80 W), cutting velocity (in three level of 6, 10, 14 mm/s) and cutting with covering gas or without gas. The results indicated that the maximum feasible laser power and increasing cutting velocity using compressed air resulted in decreasing HAZ width. By gradual increase of the laser power the cutting mechanism converts from melting to evaporation. Increasing laser power and cutting velocity individually made the dross height smaller. The process parameters were optimized to achieve minimum top kerf width, minimum HAZ width, and ratio equal to 1.
A significant improvement in laser cutting productivity and quality can be achieved using dynamic beam shaping (DBS). However, the broad potential of improving the cutting performance of thick plates ...by employing DBS has not been fully explored. This paper uses an extensive experimental campaign to evaluate laser cutting results using DBS for different industrially relevant materials and thicknesses. Moreover, optimum amplitude and frequency for different material-thickness combinations regarding maximum achievable cutting speed are investigated. In addition, the effects of changing DBS parameters on dross, roughness, heat-affected zone, and kerf area are explored and correlated to the material removal mechanism. Finally, the laser cutting performance using DBS is compared with static beam cutting applied on higher laser powers. The results demonstrate that the performance of a 4 kW laser cutting machine reinforced by DBS is higher than a 6 kW laser cutting machine with a static beam strategy (SBS) when cutting thick plates.
•The effects of dynamic beam shaping (DBS) on laser cutting of different materials and thicknesses are investigated.•The requirements of dynamic beam parameters for each material-thickness combination are explored.•The influence of dynamic beam parameters on dross, kerf area, and HAZ is studied and correlated to the dynamic flow of the molten material and melt removal mechanism.•The performance of laser cutting of thick plates using DBS is compared with static beam strategy within different laser powers.
Carbon fiber reinforced polymer (CFRP) is prone to produce significant thermal damage such as heat-affected zone (HAZ) during laser cutting, which seriously affects the processing quality. In this ...paper, a new method of dimethicone-assisted interlaced scanning mode (DISM) compound cutting is proposed to regulate the surface damage of CFRP nanosecond UV laser hole cutting. Based on the simulation and experimental testing analysis, the coupling effect of heat conduction and heat accumulation during the laser cutting process, as well as the suppression mechanism of heat effects by compound cutting methods have been described. Compared to the default cutting method, DISM can effectively reduce the damage of CFRP laser hole cutting. The average matrix recession (MR) width of the hole entrance edge is reduced by 47.54% for DISM, while eliminating the heat-damaged matrix (HDM) zone, resulting in a comprehensive reduction of HAZ by 85.2%. The most obvious parameter combination for the reduction of MR width is 50 kHz, 1000 mm/s, and 0.06 mm, where the MR is reduced by 61.31% (37.61 μm→14.55 μm). Interlaced scanning mainly reduces MR width, while dimethicone-assisted processing exhibits suppression of HDM. The compound cutting method significantly reduces thermal damage and improves CFRP mechanical properties.
•Acoustic emission (AE) technique was firstly proposed to analyze ablation mechanism of CFRP laser cutting, and it was used as a guide to improve the material removal rate.•Two processing mechanism ...of thermal ablation (TA) and mechanical denudation (MD) were found through the analysis of the time-domain characteristics of AE signal.•The scanning speed and interval were optimized under the guidance of the RMS value of AE signal, resulting in a maximum material removal rate of 12.2 × 107 μm3/s.
The ablation mechanism of CFRP laser cutting refers to complex thermal and mechanical behaviour, and should be investigated. Two processing mechanisms of thermal ablation (TA) and mechanical denudation (MD) were found. TA resulted from the vaporization of the material formed by the accumulation of laser energy, which is reflected by RMS of AE signal < 0.14 V. MD resulted from the material that was stripped from the substrate under the impact of the plasma plume, which is reflected by 0.14 V < RMS < 0.175 V; The processing mechanism of MD exists simultaneously in the same trajectory and adjacent trajectory scanning. When the mechanism of MD in the same trajectory scanning is most severe, RMS also reaches the maximum value of 0.23 V; The RMS has the same variation law as the material removal rate. When the removal rate reaches the maximum value of 12.2 × 107 μm3/s, the RMS curve also reaches its highest point, and the model prediction accuracy is greater than 89%.
Today, almost any material can be cut with a laser. CO2 laser cutting is a promising technology for textiles, offering precision and flexibility. Unlike synthetic textiles, natural fibers such as ...cotton and wool do not melt when exposed to the heat of the laser beam, which can cause undesirable discoloration during laser treatment. Therefore, the power of the laser source and the speed of the process, as well as accurate matching to the material being processed, are critical to achieving optimal results in laser cutting of such blended fabrics. In this work, a theoretical model based on the energy balance equation is developed to estimate the cutting depth and speed by calculating the effective thermal properties of a fabric composed of two different fibers. By altering the laser parameters, a sequence of trials was performed on Fustian fabric comprising 45 % wool and 55 % polyester. The results indicate that a continuous CO2 laser with an output power of 45 watts at a speed of 30 mm/s can cut 10 layers of fabric while maintaining superior quality. The suggested model is in line with the experimental findings. Moreover, the theoretical framework correctly predicts how varying blend ratios in the material affect the cutting process based on further tests carried out. These results are significant for the future development of laser technology in the apparel industry.
