Laser cutting is a popular manufacturing process utilized to cut various types of materials economically. The width of laser cut or kerf, quality of the cut edges and the operating cost are affected ...by laser power, cutting speed, assist gas pressure, nozzle diameter and focus point position as well as the work-piece material. In this paper CO
2 laser cutting of stainless steel of medical grade AISI316L has been investigated. Design of experiment (DOE) was implemented by applying Box–Behnken design to develop the experiment lay-out. The aim of this work is to relate the cutting edge quality parameters namely: upper kerf, lower kerf, the ratio between them, cut section roughness and operating cost to the process parameters mentioned above. Then, an overall optimization routine was applied to find out the optimal cutting setting that would enhance the quality or minimize the operating cost. Mathematical models were developed to determine the relationship between the process parameters and the edge quality features. Also, process parameters effects on the quality features have been defined. Finally, the optimal laser cutting conditions have been found at which the highest quality or minimum cost can be achieved.
► Five different parameters have been investigated simultaneously. ► Estimation of the processing cost. ► The investigation of the ratio between the upper and lower kerfs. ► The optimal operating conditions have been defined.
Poly-methyl-methacrylate (PMMA) microchannel based devices are gaining popularity, particularly in medical applications. Experiments were carried out on a PMMA based microchannel profile of thickness ...10 mm through a 100-Watt CO2 laser machine by varying laser power, scanning speed and number of passes of the laser machine. The full factorial design of the experiment was implemented to investigate the microchannel profile, depth and surface roughness of the microchannel. The analytical model was developed to predict the microchannel profile and depth for the prescribed number of laser passes. The developed analytical model has been compared with the experimental investigations and also with the previously developed models available in the literature. Results of the analytical model predicted the fabricated profile with appreciable accuracy. Moreover, the close agreement of the results with the available literature models validates the acceptability of the proposed analytical model. The surface roughness predictive modeling using linear regression, polynomial regression of order 2,3 and 4, exponential Box-Lucas method and sigmoid Boltzmann models have been compared. The statistical analysis of all the models was performed, with the analysis of variance, mean squared error, Root Mean Square Error, mean absolute percentage error and coefficient of determination. Based on the comparative assessment, the best fitted and accurate model obtained was polynomial regression of order 3. Thus, the improved surface roughness generated with the laser machining would be a time and cost technique for the fabrication of microfluidic devices.
•A range of 2D auxetic mechanical metamaterial sheets capable of exhibiting highly negative Poisson's ratio were produced using direct laser cutting.•Almost all perforated architectures show large ...stretchability and retain their large auxetic behaviour over significant strain ranges.•Influence of boundary effects and out-of-plane thickness on the in-plane mechanical properties were also investigated.•Re-entrant-like systems show anomalous boundary effects which result in non-uniform deformation profiles which could potentially make them ideal candidates for future implementation in sensory devices.
The design and production of multifunctional materials possessing tailored mechanical properties and specialized characteristics is a major theme in modern materials science, particularly for implementation in high-end applications in the biomedical and electronics industry. In this work, a number of metamaterials with perforated architectures possessing the ability to exhibit a plethora of 2D auxetic responses with negative Poisson's ratios ranging from quasi-zero to large negative values (lower than −3.5), stiffnesses, stretchability and surface coverage properties were manufactured. These systems were produced through the introduction of microstructural cuts in a rubber sheet using direct laser cutting, and analysed using a dual approach involving experimental tests and Finite Element Analysis. In addition to examining the mechanical properties of the perforated metamaterials, the influence of edge effects and material thickness on the deformation behaviour of these systems were investigated, with re-entrant systems shown to possess anomalous deformation profiles which are heavily dominated by the boundary regions. These findings highlight the effectiveness of this method for the fabrication of auxetic metamaterial sheets as well as the large variety of mechanical properties, deformation mechanisms and load responses which may be obtained through what may be effectively described as simply the introduction of patterned cuts in a thin sheet.
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Tribovoltaic nanogenerators (TVNGs) usually consist of two heterogeneous materials with disparate Fermi levels. However, TVNGs based on two same semiconductors with uniformed Fermi levels have been ...rarely reported, as they are believed to lack the sufficient potential difference necessary to drive tribo-induced carriers’ separation and collection, resulting in minimal or negligible electricity production. Here, tribovoltaic nanogenerators based on two homojunction semiconductors (H-TVNGs) with the same doping concentration are proposed and designed. The H-TVNGs were demonstrated to be driven by abundant surface states introduced through laser cutting at the slider boundaries and surfaces, which further lead to the bending of interface energy bands. Upon two sliders of different sizes (with different degrees of band bending) come into contact, the built-in electric field at the interface will be established and drive tribo-induced carriers, leading to the production of a direct-current (DC) electrical signal. The performance of H-TVNGs could be effectively amplified or regulated by many factors, including laser cutting power, semiconductor surface roughness, slider shape, and the interface media, etc. These compelling findings reveal innovative physics in tribovoltaic effect, offer special insights for designing high-performance TVNGs, and provide effective strategies for device output optimization.
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•The tribovoltaic effect is observed in N-N and P-P homojunctions.•The performance of TVNGs can be significantly enhanced or controlled by various interface factors.•Several mechanistic models explaining the factors influencing the tribovoltaic effect have been proposed.
Silicon is the most widely used material in numerous fields. Traditional mechanical machining methods have been unable to meet the higher requirements of processing quality. Laser machining is ...especially suitable for processing hard and brittle materials due to the non-contact processing characteristics. This article summarizes the nanosecond, picosecond, femtosecond laser drilling and cutting technologies of silicon according to the classification of laser pulse widths. For the most typical field assisted machining technology, liquid-assisted laser drilling and cutting are also discussed. In consideration of the heat generated during laser processing is likely to cause stress in the material, resulting in micro-cracks and other processing defects. Laser induced thermal crack propagation cutting technology (LITP) successfully uses the cracks produced in laser machining to achieve the high cutting quality of silicon. As a new way of material internal processing, laser stealth dicing is the most promising method in the field of wafer cutting. The mechanism and processing characteristics of laser stealth dicing are described. At the end of paper, a summary and outlook are provided.
Herein, we proposed a novel laser assisted additive manufacturing (AM) methodology that utilizes prepreg composites (glass fiber-polypropylene) with continuous fiber reinforcement to fabricate 3D ...objects by implementing laser assisted bonding and laser cutting. The microstructure analysis demonstrated no visible void content and excellent interfacial bonding. The bonding strength of the proposed method was evaluated through lap shear strength and peel strength testing; resulting in 50% higher peel strength than hot compaction method, with lap shear strength up to 96% of compression molding benchmark data. Tensile properties of components printed by our method were superior to those of fused deposition modeling (FDM) printed short fiber composites with 300% and 150% of increase in tensile strength and modulus, respectively. Tensile strength of our printed components was comparable to compression molding and stamping, however, tensile modulus was 50% lower in average. Flexural strength of the laser assisted AM parts was also in the range of stamping and compression molding methods, with flexural modulus up to 100% higher than these methods. Overall, our proposed new technique offers an alternative direction in AM of continuous fiber reinforced thermoplastic polymer composites to solve the issues associated with current techniques.
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•A new laser assisted additive manufacturing (AM) technique was proposed for Continuous fiber reinforced thermoplastic polymer composites (CFRTPCs).•The interfacial bonding was excellent with no visible void content.•Mechanical properties of the 3D objects were comparable with traditional composite manufacturing methods.
In this study, an optimized artificial intelligence model is developed to predict the kerf quality characteristics in laser cutting of basalt fibers reinforced polymer composites. The model is ...composed of Long Short-Term Memory (LSTM) and Chimp Optimization Algorithm (CHOA). The latter is used as an internal optimizer to obtain the optimal parameters of the network model. The developed model was compared with three other models, namely standalone LSTM, LSTM optimized using Heap-Based Optimizer (HBO), and LSTM optimized using Manta Ray Foraging Optimization (MRFO). All models were trained and tested using experimental data considering five process control factors (cutting speed, air pressure, pulse frequency, pulse width and lamp current) and three process response (kerf width, kerf taper and kerf deviation). Response surface methodology was used to design the experimental plan. The accuracy of the models was evaluated and compared to each other using different statistical measures. LSTM-CHOA succeeded to predict kerf quality characteristics of the cut composites despite of their heterogeneous and anisotropic structure and it outperformed the three other models. The root mean squared error of the predicted kerf width, kerf deviation and kerf taper using LSTM-CHOA decreased by about 27.43%, 60% and 56.6%, respectively, compared with that of standalone LSTM.
The object of research in the paper is the technology of manufacturing segments of the rotor rim of large hydrogenerators-motors. The subject of study is the design and geometrical state of the rotor ...rim during the operation of hydraulic units. The goal is to make a three-dimensional mechanical calculation of the rotor segment for the further determination of the most optimal technology for the rotor rim manufacturing. The following tasks are set: to study the peculiarities of the manufacturing technology of the rotor rim segments; to perform an analytical calculation and a three-dimensional calculation with the determination of the average values of stresses and deformations in the rotor segment. The used methods are: finite element method of mathematical modeling of the thermal stress state of nodes. The following results were obtained: a description of the two main manufacturing technologies of the rotor rim segments, namely the stamping method and the laser cutting method, was provided. The advantages and disadvantages of each technological process were analyzed, and it was determined that the laser cutting method should be used in the production of powerful small-scale hydrogenerators. Three-dimensional models of the rotor segment were developed and a three-dimensional mechanical calculation of this model was performed, as a result of which the value of the displacement of the rotor of the hydrogenerator at the nominal frequency of rotation, as well as the average values of the stresses in the spoke and the rim of the rotor, were obtained. Based on the results of calculations, it was established that significant tolerances in the manufacture of rotor segments can lead to changes in the shape of the rotor during its further operation, the appearance of additional vibrations and further affect the performance of the hydraulic unit. The scientific novelty consists in a combined approach to the estimation of the average values of stresses and deformation of the rotor rim, taking into account the technology of its manufacture, which includes elements of analytical mechanical calculation and calculation in a three-dimensional setting.
•The mechanical properties of CFRP short pulse laser cutting and the effect of damage on it were studied.•Combined with mechanical drilling, the crack propagation and fracture mode of CFRP laser ...cutting scale are analyzed.•Large damage further reduces the tensile and bending strength of CFRP and intensifies the fatigue crack propagation.•The findings are helpful to lay a foundation for damage suppression and improvement of CFRP mechanical properties.
Carbon fiber reinforced polymer (CFRP) composites are widely used in the aerospace field because of their outstanding performance. Short pulse laser is an effective means for efficient and high-quality cutting of CFRP. However, the inevitable thermal effect of laser processing results in damage such as heat-affected zone, and the exposed area of fiber loses the ability to transmit force, which weakens the mechanical properties of CFRP. However, the effect of thermal damage on mechanical properties is complex. In this paper, the dynamic and static mechanical behavior of short pulse laser cutting CFRP is studied, and the effect of cutting damage on the mechanical properties is explored. The mechanical properties of CFRP plate hole laser cutting is similar to those of mechanical drilling but are lower than those of material without hole due to the existence of holes. Matrix cracking exists in the tensile fatigue of laser cutting holes, while surface cracks occur in the stress-concentrated area due to the not smooth cutting edge of mechanical drilling. Compared with small laser cutting damage, the tensile and bending strength of the CFRP plate were weakened by 11.5% and 6.2%, respectively. The tensile fatigue crack propagation and fiber protrusion are aggravated by large damage. The damage always starts at both sides of the vertical direction of the hole under 0° laying, resulting in cracks along the fiber axis until fracture. The failure mode and fracture cross-section morphology are mainly fiber tears and delamination, and the section of the 90° laying specimen surface is tidier than that of the 0° laying specimen. The mechanical properties under thermal damage studied in this paper will help to lay a foundation for damage suppression and improvement of material mechanical properties.
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