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1

The analysis of EDM electrodes wear in corners and edges

Mouralova K., Bednar J., Benes L., Hrabec P., Kalivoda M., Fries J.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

484--497

EN

Die-sinking electrical discharge machining is an unconventional technology that allows to machine all at least minimally electrically conductive materials regardless of their physical and mechanical properties. Despite the fact that it is not a conventional technology, the tool gets also worn out, which is a tool electrode. The wear of the electrode does not only mean its loss but also the degradation of the shapes that are transferred to the resulting workpiece. For this reason, a design of experiments was conducted with 6 input factors, 2 were categorical: the electrode material (copper, graphite) and workpiece material (steel 1.2363 and steel 1.2343ESR) and 4 were numerical: Open-voltage, Pulse current, Pulse on-time, and Pulse off-time. In the framework of this design of experiments, the wear of the used graphite and copper electrodes at their corners and edges was evaluated, which was made possible by the use of electron microscopy and the use of approximation circles. Furthermore, the eroding speed, the topography of the machined samples, and the morphology of the surfaces of the used electrodes were investigated. It has been recognized that the use of a graphite electrode will allow for more accurate workpiece shapes and less wear.

2

Interaction of steel cord – elastomer in radial tyres for passenger vehicles

Krmela J., Benes L., Krmelova V.

Production Engineering Archives

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2014

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Vol. 5, No. 4

10--13

EN

The article focuses on determination of selected material characteristics of samples from different areas of various old passenger tyre casings and on determination of mechanical properties of specific composites with elastomeric matrix and steel reinforcement which are used as steel belts of tyre casing as a sample. These characteristics are used as input data for computational modelling of tyres. It was necessary to carry out various types of experiments to obtain these characteristics. In this article we present the values of the modules of elasticity calculated from the results of DMA tests and static tension tests of samples from old tyre casings and a cohesion test between steel cords and elastomeric matrix. The Mooney-Rivlin parameters, which are necessary input data into computational models of tyres and their parts, were determined from the experimental results. The computational models will be designed to be able to include the effect of aging of the individual tire casing parts. Knowledge of the degradation processes can lead to design and material changes that can increase the resistance of casings against selected forms of degradation processes.

3

Summary of energy industry products selected properties of alkali-activated materials and alkali effects on these materials

Minar L., Benes L., Halas O.

International Journal of Applied Mechanics and Engineering

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2010

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Vol. 15, no 2

343-348

EN

This paper deals with the use waste raw materials produced by energy industry. The paper lists and describes types of these waste raw materials produced during coal burning and flue gases desulphurization (FGD) process, and shows ways for their use primarily in the field of alkali-activated fly ash-based materials. It also deals with producing alkali-activated materials from fly ash, and focuses on effects of input quantities on their final properties. It further assesses and describes selected physical properties of fly ash influencing mechanical characteristics of alkali-activated materials produced from fly ash. Moreover, it shows the significant effects of alkalis on the final strength, and summarizes the findings in this field.