RESUMEN
Electrical Discharge Machining (EDM) is one of the most efficient processes to produce high-ratio micro holes in difficult-to-cut materials in the Inconel 718 superalloy. It is important to apply a statistical technique that guarantees a high fit between the predicted values and those measured during analysis of test results. It was especially important to check which method gives a better fit of the calculated result values in case they were relatively small and/or close to each other. This study developed models with the use of the response surface methodology (RSM) and artificial neural networks (ANNs). The aim of the study was comparison between two models (RSM and ANNs) and to check which model gives a better data fit for relatively similar values in individual tests. In all cases, the neural network models provided a better value fit. This is due to the fact that neural networks use better fitted functions than in the case of the RSM method using quadratic fitting. This comparison included the aspect ratio hole and the thickness side gap data, the values of which for individual tests were very similar. The paper reports an analysis of the impact of parameter variables on the analyzed factors. Higher values of current amplitude, pulse time length, and rotational speed of the working electrode resulted in higher drilling speed (above 15 µm/s, lower linear tool wear (below 15%), higher aspect ratio hole (above 26), lower hole conicity (below 0.005), and lower side gap thickness at the hole inlet (below 100 µm).
RESUMEN
Nickel-based superalloys are being increasingly applied to manufacture components in the aviation industry. The materials are classified as difficult-to-machine using conventional methods. Nowadays, manufacturing techniques are needed to drill high aspect ratio holes of above 20:1 (depth-to-diameter ratio) in these materials. One of the most effective methods of making high-aspect-ratio holes is electrical discharge drilling (EDD). While drilling high aspect ratio holes, a crucial issue is the flushing of the gap area and the evacuation of the erosion products. The use of deionized water as the dielectric fluid in the EDD offers a considerable potential. This paper includes an analysis of the influence of the machining parameters (pulse time, current amplitude and discharge voltage) on the process performance (drilling speed, linear tool wear, taper angle, hole's aspect ratio, side gap thickness), during the EDD with the use of deionized water in the Inconel 718 alloy. The obtained through holes were subjected to the extended analysis. The impact of the initial working fluid temperature and pressure on the conditions of the flow through the electrode channel was also subjected to the analysis. The deionized water properties were changed by applying an initial temperature. Based on the results of an analysis of the previous research, the EDD of the through holes was performed for a pre-set initial temperature (~313.15 °K) and initial pressure of the working fluid (8 MPa) and selected process parameters. An analysis of the results indicates increasing of hole's aspect ratio by about 15% (above 30), decreasing the side gap thickness by about 40% and enhanced surface integrity.
RESUMEN
Alternative fuels (refuse-derived fuels-RDF) have been a substitute for fossil fuels in cement production for many years. RDF are produced from various materials characterized by high calorific value. Due to the possibility of self-ignition in the pile of stored alternative fuel, treatments are carried out to help protect entrepreneurs against material losses and employees against loss of health or life. The objective of the research was to assess the impact of alternative fuel biodrying on the ability to self-heat this material. Three variants of materials (alternative fuel produced on the basis of mixed municipal solid waste (MSW) and on the basis of bulky waste (mainly varnished wood and textiles) and residues from selective collection waste (mainly plastics and tires) were adopted for the analysis. The novelty of the proposed solution consists in processing the analyzed materials inside the innovative ecological waste apparatus bioreactor (EWA), which results in increased process efficiency and shortening its duration. The passive thermography technique was used to assess the impact of alternative fuel biodrying on the decrease in the self-heating ability of RDF. As a result of the conducted analyses, it was clear that the biodrying process inhibited the self-heating of alternative fuel. The temperature of the stored fuel reached over 60 °C before the biodrying process. However, after the biodrying process, the maximum temperatures in each of the variants were about 30 °C, which indicates a decrease in the activity of microorganisms and the lack of self-ignition risk. The maximum temperatures obtained (>71 °C), the time to reach them (≈4 h), and the duration of the thermophilic phase (≈65 h) are much shorter than in the studies of other authors, where the duration of the thermophilic phase was over 80 h.