The rotary-percussion drilling method is a prospective way to decrease drilling costs. It is obvious, based on literature analyses and finished geothermal drilling, that the Lublin Basin can be ...perceived as the one where rotary-percussion drilling can be used to drill an overburden of shale rocks. The paper explained the geology of the Lublin Basin, its’ geological structures, and the possibility of the use of drilling with a down-the-hole hammer, which could significantly decrease the cost of the whole shale gas drilling investment. Data collected from the wells drilled in the Lublin Basin were compared and analyzed to determine the viability of rotary-percussion drilling. Provided analyses showed that using the rotary-percussion drilling method in the Lublin Basin had a greater possibility of application than in other Polish shale basins (Baltic and Podlasie).
In laser microstructure machining, results are derived through the action of multiple laser processing parameters (LPPs); therefore, multiple studies on the effect of LPPs on machining results are ...available. Further, few studies observed how competitive mechanism of each LPP affects machining results. As the most important LPPs, single-pulse energy and the number of pulses were varied to assess their effect on hole dimension and morphology. Additionally, competitive mechanism of LPPs on hole ablation was further explored. The study was based on femtosecond laser percussion drilling on aluminum nitride (AlN) ceramics surface. It was found that laser energy has a dominant role in initial ablation, determining both ablation and ablation mechanism. Additionally, it also determined hole inlet surface morphology and ablation mechanism remained the same regardless of increase in the number of pulses. Laser pulses assumed a dominant role after intersection point of LPPs acceleration rate and hole dimension acceleration rate. Hence, final hole dimensions and its sidewall morphology were defined. It was found that deep holes can be processed both in gentle ablation and strong ablation with lots of pulses. However, there are opposite mechanisms for inducing hole sidewall morphology; for example, in strong ablation, solidification effect is enhanced with increase of hole depth, while it is decreased in gentle ablation.
Delamination and microcracks as well as spatters are known to be inherently associated with laser drilling thermal barrier coated materials. In this study, response surface method (RSM) and ...single-variable method were employed to correlate the laser parameters including pulse length, peak power, pulse rate, and pulse numbers as well as the interactions among them with such defects in laser percussion drilling. Detailed observation and analysis reveals that narrow pulse length, lower peak power, and low pulse rate can produce smaller cracks area on the side wall, among which the effect of pulse length is more outstanding. As for spatters around hole entrance, the interactions among these factors were identified and a combination of higher peak power, proper pulse length (in this model not exceed 1 ms), higher pulse rate, and small number of pulses are conducive to minimize the spatter volume. Furthermore, the thermal effect near the thermal barrier coating/bond coat (TBC/BC) is especially prominent in laser drilling with wide pulse length and low peak power. The removal mechanism occurred near TBC/BC also determines the delamination crack size. And higher peak power with narrow pulse length should be a good strategy in order to break through the TBC as soon as possible and shelter the TBC or TBC/BC from thermal damage.
A major challenge in laser percussion drilling of thick-section ceramics is to obtain a low taper and low spatter deposition hole leading to high quality post-processing. In order to achieve the fine ...hole drilling, it is important to understand the mechanism of laser percussion drilling. In this paper, an experimental and numerical study on laser percussion drilling was carried out. A two-dimension (2D) axisymmetric finite element (FE) model for simulation of temperature field and proceeding of hole formation during percussion drilling was developed. The FE model was validated by the corresponding experiment. Furthermore, a theoretical model for evaluation of temperature at melt front and velocity of melt ejection was presented in order to further validate the FE model and study the spatter deposition. The effects of laser peak power, pulse duty cycle and pulse repetition rate on hole diameter and spatter deposition were investigated by the developed models and experiments, in which the simulated results were in good agreement with the experiments. The study indicated that the size and temperature of the melt front significantly affected the hole diameter formation and spatter deposition during laser percussion drilling. The characteristic of melt front was mainly determined by the employed laser peak power, pulse repetition rate and pulse duty cycle. Based on the experimental and numerical study, the process parameters were optimised and a drilled-hole with low taper and low spatter deposition was obtained using a 3.5kW CO2 laser. A microstructural and element compositional study was also performed in this work, by which the characteristics of microstructure and element composition in HAZ around laser drilled hole were revealed.
This research aims to develop a feedback control laser processing system using artificial intelligence. Real-time online measurement of hole depth for blind hole processing is challenging. In this ...study, electric fields were used to detect laser-induced plasma signals and a neural network was used to predict the hole depth to overcome this difficulty. This electric field was generated by a pair of electrode plates placed above the drilled surface to provide hundreds of volts of DC voltage. During laser processing, laser-induced plasma interferes with the electric field and generates a detection signal. This signal is sent back to the neural network to estimate the hole depth. This study also trained a neural network to predict the machining parameters required for a given hole depth and diameter. If the error in the hole size after processing exceeds the threshold value, the feedback control system will perform immediate compensation processing to reduce the error. This avoids the difficulty of relocating the material. Therefore, this study integrated laser processing, online laser-induced plasma detection, and neural network-based parameter estimation to form an advanced feedback control laser machining system that can solve the problems of processing parameter prediction, real-time hole depth measurement, and compensation processing relocation encountered during the processing process. The experimental results demonstrate that the proposed method can effectively compensate for processing and reduce errors.
•An efficient and low-cost optimization framework for femtosecond laser processing is proposed.•A new four-stage drilling process is proposed and optimized using the process optimization ...framework.•The optimized solutions to improve both drilling efficiency, recast layer and taper are obtained.
Although femtosecond laser percussion drilling is widely used in many key industrial manufacturing fields, the quality of micro-holes limits its service performance. The traditional trial and error method and physical model are always time and cost consuming for process optimization. To address this problem, a process optimization framework coupled with molecular dynamics simulation, machine learning and a high-throughput optimization algorithm is proposed. The physical information obtained by molecular dynamics enriches the data set used to train machine learning model, and thus reducing the amount of data required. Machine learning can quickly and accurately establish the regression model between laser parameters and target machining performance, and high-throughput optimization algorithm is responsible for determining the optimal process in the process space. For femtosecond laser percussion drilling, a new four-stage drilling process is proposed and optimized using the coupling process optimization framework to solve efficiency and quality problems. Finally, the experimental validation for Ni-based single crystal superalloy verifies the reliability of the optimized process. The framework can be extended to other complex systems to realize process optimization with high efficiency and low cost in laser material processing technology.
Laser percussion drilling is increasing its relevance in many industrial applications, being used particularly in the aircraft industry in performing the micro-holes in nickel based alloys turbine ...blades for cooling, or stainless steel medical components drilling, which require small holes size and quality. Laser percussion drilling process presents extremely high speed for high aspect ratio holes. Moreover, the quality and accuracy of the holes can be excellent if the optimal parameters are set.
The laser percussion drilling process is usually performed with specific equipment, including lasers that achieve high peak powers of picoseconds duration. These systems are usually dedicated exclusively to laser drilling operation. It is also very common to perform this process using the parameters suggested by the manufacturer of the equipment and without any consideration about the mechanism of formation of the hole. On the other hand, laser percussion drilling is performed by a sequence of pulses on the part surface. Each pulse removes a certain amount of material. The energy and duration of pulses set the amount of removed material by each one.
This work discusses the mechanisms of formation of the holes in the laser percussion drilling process of an AISI 304 plate, evaluating the removed material volume in each laser pulse and obtaining the evolution of the hole geometry for the complete pulse sequence. In addition, this experimental analysis has been apply also for the development of a numerical model that can simulate the resulting hole geometry for different pulse sequences.
•Laser percussion drilling tests were carried out on a 1mm thick AISI 304 stainless steel sheet.•Process show high repeatability and inlet diameter ranges 140–150µ for a 100µ spot size.•Internal shapes of the holes have been measured, reconstructing the internal volume.•A thermal model has been developed to predict the resulting shape of the holes.•The validation of the model shows that the agreement between the model and measured values is below 10% of error.
To mine in the underground, the method of blasting and blast hole drilling methods are mainly, and widely accepted. The hole drilling methods are done with rotary percussion drill. However, there are ...problems in terms of difficulty of operating and mining cost resulting from its failure occurs, and thus it is hard for mining companies to find a way of mining underground efficiently, profitability, and safely. From this background, it is necessary to build the early detection system for drill bit failure. This system needs the technology of CNN (Convolutional Neural Network Smart Mining, which is the process of using information, autonomy, and technology to improve safety, reduce operating costs, and improve mine site productivity. In this research, drilling vibration from rotary percussion drill is transmitted as acceleration waveform and used as input data for building the system. The data is collected replacing the kinds of diameter of bit or drilling condition. This data is for developing the model introduced CNN to detect the difference between Normal drilling and the other kinds of drilling with something error. For Firstly, batch of waveform data is input model as training data to make the model recognize the data pattern. Secondly, validation process confirms the correct answer rate against the training data, and then, the test for the model is practiced. Finally, by comparing each accuracy in phase of test from 4 types of models built with different kinds of data and the ideal way of the input waveform data is found.
A simplified analytical model is presented that predicts the depth progress during and the final hole depth obtained by laser percussion drilling in metals with ultrashort laser pulses. The model is ...based on the assumption that drilled microholes exhibit a conical shape and that the absorbed fluence linearly increases with the depth of the hole. The depth progress is calculated recursively based on the depth changes induced by the successive pulses. The experimental validation confirms the model and its assumptions for percussion drilling in stainless steel with picosecond pulses and different pulse energies.
Femtosecond laser with wave length of 800 nm was used to perform percussion drilling experiment on nickel-based alloy with thermal barrier coatings (TBCs) in order to eliminate the damages caused by ...conventional drilling. Analysis of the experimental results indicated that short pulse duration and high peak power characteristics of femtosecond laser led to good processing effect on nickel-based alloy with TBCs. High quality array of holes with the taper of almost zero was generated, for which the inner diameter was 162 μm and the aspect ratio was 15:1. Femtosecond laser processing had little influence on elementary components and phase structure of coating. This study provides feasible technique involving the use of femtosecond laser for machining film cooling hole on nickel-based alloy with TBCs.
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