In this article, the use of acoustic emission signal analysis for in-process assessment of the surface quality in abrasive waterjet machining is presented. The authors carried out an analysis of the influence of the cutting head traverse speed (considered in this case as the performance measurement) on the flatness, waviness and roughness of surfaces made of aluminium alloy 5251 after cutting process, as well as the influence of changing the quality factor on values of selected descriptors of the emitted high-frequency acoustic emission signal processed in the frequency domain. This was a new approach, different from the norm, in which an acoustic emission signal is usually studied for low frequencies. The obtained results confirmed the clear influence of machining conditions on the geometric structure of the obtained cuts and the registered values of the emitted stress waves. This influence can be accurately determined by the use of the high-frequency acoustic emission signal analysis being proposed. Additionally, statistical dependence models developed between the given process quality indicator and the registered selected acoustic emission signal parameters in the frequency domain allowed for the prediction of the surface texture of the obtained cuts on the basis of the acoustic emission signal emitted during the machining process.

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The centrifugal disc finishing process is an abrasive technique of mass machining, and it is very effective but very frequently time consuming. In this paper, a simulation of the centrifugal disc finishing process was presented in order to estimate the kinetic energy distribution of the working medium and to find its regions that make the process more efficient. Numerical results were obtained using an explicit method in the Ansys/Ls-Dyna program. Due to the fact that the physical properties of numerous objects in free motion need to be calculated in a simulation process, the discrete element method (DEM) was used. Results from the numerical simulations indicate that the velocity and energy of particles is variable in an axial cross-section of working medium. The article presents particle velocity distributions in the working chamber for various rotational speeds of the rotor. The typical changes in velocity in the function of time are also discussed. Statistical important functions of the average kinetic energy of the working medium and accumulated energy by machining surface have been estimated in respect to the rotational speed and machining time with a high value of adjustment coefficients. This article constitutes the first stage of research, which is continued in order to experimentally verify the results in the real process, as presented in the companion paper (Part 2: Experimental analysis with the use of acoustic emission signal).

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This paper addresses the problem of estimating the kinetic energy distribution of the working medium in a centrifugal disc finishing process. Centrifugal disc finishing is a highly effective way of finishing surfaces, especially in the case of complex shapes, made from a variety of materials. The process is, however, frequently very time-consuming. The identification method of a region with a high kinetic energy potential by measurement of acoustic emission signal is described and verified by surface roughness tests. Signal analysis was carried out in both time and frequency domain. The results presented in experimental tests and analyses indicate that various parameters of the AE signal, including its energy, are variable and determined by abrasive particles' velocity and location in an axial cross section of the working medium. On the basis of the root mean square value of the signal, the maps of the distribution of the energy potential of the working medium are presented. Experimental results demonstrate process improvement and a significant reduction (approx 60%) of the arithmetic mean deviation of surface roughness, obtained at the same time of machining. The article also presents the functional relations between the selected AE signal descriptors and the rotational speed of the working chamber rotor. Since the article is a continuation of the previous studies, the results obtained were briefly referred to the simulation results.

The condition of the cutting tool is one of the most important factors as it directly affects the technological and economic efficiencies of the woodworking process. The large variety of raw materials of wood combined with possible impurities and inclusion of solids puts high demands on planing machines. One of the methods to modify their operational properties is to apply antiwear coating on their working surfaces using vacuum deposition methods, such as physical vapor deposition (PVD). The use of such coatings reduces the adhesion of planing products to the surface of industrial planer knives, reduces the friction between the cutting tool and the workpiece, and limits the penetration of heat into the tool, thereby contributing to extending its effective working life. This study examines the impact of PVD-based CrCN/CrN coating on the operational durability and intensity of wear of planer knives operating in production conditions compared to unmodified knives (typically used in the wood processing industry for pine wood planing). For the unmodified and CrCN/CrN-coated planing blades (before and after processing), detailed analyses were carried out. These analyses included determining the rounding radius and profile along the blade (worn edge displacement), calculating surface texture parameters of the rake face of planer knives, and carrying out visual microscopic analysis of its condition. The results of the experiments indicated an increase in durability of up to 142% for the CrCN/CrN-coated tools. It was also found that the use of PVD-based modified industrial planer knives turned out to be more beneficial in each analyzed area of analysis.

This article presents the properties of a new generation of abrasive grains made from aluminum oxynitride AlON (Abral®), as well as the methodology and application of acoustic emissions as a measurement analysis method for those stress waves generated during the brittle fracture process. The methodology of evaluation of grain properties presented in the article mostly consists of examining the resistance to fracture as a result of the force applied and analyzing the registered acoustic emission signals. The applied solution involves using a tension machine and conducting compression tests upon AlON grains and, as a point of comparison, white fused alumina 99A grains, microcrystalline sintered corundum SG™, and green silicon carbide 99C. What was analyzed were the registered compression force values and acoustic emission signals within the time and frequency domains. The characteristics within the time function involve determination of the event and ring-down parameters for single acoustic emission impulses. In the case of the frequency analysis, the signal amplitude and phase characteristics were determined. The research results indicate that stress fractures appear during grain compression tests, which generate elastic waves of various characteristics. The recording and analysis of these waves, in the form of an acoustic emission signal, turned out to be an efficient tool for analyzing the process of abrasive grain cracking and made it possible to differentiate their structure. The research results obtained point to the necessity for further analyses into stress-wave emission, especially with reference to the selection of the most effective methods for analyzing the signal frequency spectrum.