Sadegh Elhami

Glass and ceramics have broad applications in modern industries; however, unique properties such as brittleness, and low machinability limit their fabrication processes. This way, electro-chemical discharge machining (ECDM) is a new method that can shape hard, brittle, and non-conductive materials. ECDM improvement is the subject of recent investigations through the application of chemical and physical phenomena. Current research studies the accuracy and surface integrity (cracks and HAZ) aspects of the double-pass ECDM process (DP) which is a new and straightforward method. During the double-pass process, two sequential passes are employed to shape the final geometry. In addition, the variable voltage technique is studied to achieve higher machining efficiency in DP. Results showed that in the diameter difference of 100 µm, the double-pass process reduced overcut by up to 21% compared to the typical ECDM process. Also, the size and number of cracks and the extent of HAZ were significantly decreased. Finally, in the diameter difference larger than 300 μm (the constant voltage of 32 V), the enhancement modification (variable voltage) reduced the overcut by more than 80%. At the same time, depth results remained close (less than 5% difference) to the simple ECDM process.

Electrochemical discharge machining (ECDM) is a nontraditional machining process applied to nonconductive and brittle materials such as glass and ceramic. In recent years, investigations have focused on improving machining efficiency, especially the material removal rate (MRR). In this regard, different techniques, including chemical and physical phenomena, have been employed on different components of the ECDM system. Current research applies a new and straightforward method to improve the MRR without the consequent complexity of other techniques (improved machining efficiency). In this way, the machining process applies in two sequential passes (double-pass machining) to shape the final geometry. In the typical ECDM process, the whole geometry is machined by one pass process. Results showed that by employing the double-pass technique, the maximum depth reached 660 µm, which was 35% higher than the single-pass (SP) process (the total machining time of SP was the same as double-pass). In addition, a significant average improvement percentage of 45% was achieved. The optimum diameter difference of the tools in the double-pass process was 300 µm, which led to the highest depth values. Depending on the tool changing time, the double-pass process is economically efficient in machining depths of more than 250 µm.

Functionally graded material (FGM) are a composite material which consists of filler material and matrix. FGM properties vary along the composition gradient. Common FGMs employs one type of filler material with specific properties. The application of two types of filler materials makes an opportunity to achieve the advantages of two types of filler materials, simultaneously. This study focuses on the FGMs with two types of filler materials and polyester resin (polymer) as a matrix. In this regard, the centrifugal technique is employed to fabricate dual filler functionally graded polymer materials (DF-FGPM). Copper-Silicon Carbide and Iron-Fused Alumina are used as two cases of dual filler materials. The microstructure and flexural strength of samples are evaluated using the image processing method and three-point bending test (according to ASTM D790), respectively. The results of particle distribution showed the different behavior of particles which can enhance surface and volumetric properties, simultaneously. Also and because of the importance of the interfacial layer in the composite structure, developed FGM presented achievements in the B type of loading during the three-point bending test.

Electrochemical discharge machining (ECDM) is one of the non-traditional processes which employs physical and chemical phenomena to remove the material from the non-conductive workpiece. Moreover, some technical augmentations have been added to the mentioned process to achieve a more efficient machining method. Typically, ECDM includes numerous electric discharges, but study on a single discharge, with/without application of external augmentation, leads to understanding the complicated nature of the ECDM process and the effect of technical augmentation. In this research, the ECDM process is studied in the mode of single discharge. Also, ultrasonic vibration, as a technical augmentation, is added to the process (UAECDM) and related effects are studied. For this purpose, special configuration and equipment are used to apply ultrasonic vibration and generate only single discharge. Material removal and tool wear are two important characteristics of drilling process which can be considered to determine the machining efficiency. The current signal is used to determine the current variation and discharge(s) condition. Results showed that the application of ultrasonic vibration changed the current signal pattern to increase discharge numbers in constant condition. Also, ultrasonic vibration increased the material removal up to 35%, while tool wear reduced between 3% and 14%.