SURFACE QUALITY OF THE EDM PROCESSED MATERIALS
The article presents the importance of the EDM technology in the industry of machine building. It is mostly used in the machining of stamps and special processes in which the conventional technologies are inefficiently. It's known that only condition of machining with this method is that the material should be electro conductive. The main parameters that are followed during the process are the precision and the roughness of the surface. The collective tried to emphasise the importance variation of the roughness concerning some machining parameters. Some of the measurements were conducted at ETH Zurich using an electronic microscope.
Critical assessment and numerical comparison of electro-thermal models in EDM
Abstract Several modeling approaches have been attempted to characterize the electrical discharge machining (EDM) process based on electro-thermal concepts. However, each model has varied characteristics and approximation results. It is important to elucidate the differences of each model and their proximity to the real material removal process. In this paper, five EDM models from Snoeys, Van Dijck, Beck, Jilani, and DiBitonto are analyzed in terms of the temperature distribution, crater geometry, and material removal at the cathode. Comparative analyses on the material removal rate (MRR) ratio of the predicted result to experimental data for discharge energy range from 0.33 to 952 mJ showed that DiBitonto's model yielded the closest proximity of 1.2–46.1 MRR ratio. This is followed by Jilani (2–45.9 MRR ratio), Snoey (3.9–203.2 MRR ratio), Beck (4.9–197.7 MRR ratio), and Van Dijck (26.8–1399 MRR ratio). This paper also shows that the disk heat source models can be enhanced by improving the approximation of the heat flux and energy fraction.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.