Applied Mechanics and Materials Vols. 809-810

Abstract: When machining by electrochemical and electrical discharge machining methods, the working solution plays an important role and this paper presents the results obtained by applying of some mixtures between colloidal and inorganic solutions that will remove the drawbacks of both media and promotes the increasing of the process efficiency.

Abstract: The paper deals with Finite Element Method (FEM) of thermal and mechanical-hydraulic components of material removal mechanism at micro-electrical discharge machining aided by ultrasonics (μEDM+US), due to EDM and US contribution. The dimensions of craters produced by single discharges under μEDM+US conditions are determined with different pulse durations in order to establish a machining strategy with correlation of pulses and tool elongations.

Abstract: The paper deals with a strategy to obtain a complex conical ultrasonic horn, which integrates the tool for micro-drilling through ̵̵̼̳̹̳̱̼̈́͂˰̴̸̷̵̹̳̱̓͂˰̸̷̱̳̹̹̽̾̾˰˸ڌ̝̔̕˻̥̣˹˰̵̴̲̱̓˰̿̾˰̖̹̾ite Element Method (FEM) modeling. This approach comprises more than 20 stages, starting with preliminary determination of a basic profile stepped horn through mathematical relations. The next stages are based on Comsol Multiphysics FEM modeling, changing gradually different horn constructive elements and integrating the tool and their clamping parts. The entry data for horn geometry determination were the dimensions and own frequency of transducer subassembly, joining ultrasonic horn. Finally, the CAD file of horn was transferred to CAM file and CNC machined. Horn real own frequency obtained was very close to the result provided by FEM modeling.

Abstract: In the case of electrochemical discharge machining (ECDM), the number of influence factors is very high, and the complete determination of a mathematic pattern is very complicated, as proved by the time passed since the application of this processing technology and absence (for the time being) of such a system. The paper presents the method of random balance which allows influence factors hierarchization, depending on the amplitude of the effect they have on the response variable. The main influence factors will be considered: current intensity, voltage, electrode-tool – workpiece pressure, electrolyte supply intensity, relative velocity between the electrode-tool and the workpiece, electrode-tool thickness. The following response functions (performance criteria) were determined: processing productivity, processed surface roughness, flatness deviation. The experiment was made on an electrochemical discharge machining (ECDM) processing machine with a electrode-tool, stratified disk by introducing the electrolyte in it. The semi-finished material is alloy steel X40CrMoV5-1, and the material of the electrode-tool is generally use steel S235JR.

Abstract: This paper presents the influences of quenching technologies (classical, with cooling in magnetic field, cryogenic, with cooling in the ultrasonic field) on the dimensional stability in time and the contact fatigue behaviour of some elements of ball bearings made from 100Cr6 (RUL 1) steel. From the analysis of the experimental data obtained it has resulted that the use of ultrasound for martensitic quenching of these steels ensures changes to the properties favorable to elements of ball bearings and may represent an effective way of increasing the quality of bearings; the technology is relatively simple, it does not require substantial constructive changes in the quenching machines and no further investment of large values.

Abstract: The experimental researches presented in this paper are aimed to improve the manufacturing accuracy of a contouring machine together with an approach to eliminate the errors which lead to a less precise part after machining.In order to eliminate the errors, the machine's feed drives were tuned leading to a more precise part. In order to validate the proposed approach, the accuracy of the machine was tested before and after the tuning process.

Abstract: It is known that during the cutting process the tool wears out. This is due to the high temperatures, the relative velocities and shocks between the contact surfaces of the tool-part and the mechanical and thermal stresses which appear on the active surfaces of the tool. The result is loss of cutting and reduced processing quality. This involves taking measures to increase the values of the cutting tools and/or the durability of their cutting inserts. Tool durability can be increased by various coating methods by the depositing in a vacuum of some different materials which achieve the necessary effect. These methods are being researched globally. So far there are several methods of applying these layers. They are classified as: vacuum thermal evaporation, pulverization, ion plating and chemical vapor depositing. In order to increase the durability of the cutting tools, and to increase the wear resistance of the metal carbide insert, the authors propose in this paper the depositing of a titanium thin layer on these cutting inserts by the ionic plating method. This method has produced increased durability of the coated cutting insert and increased resistance to wear, higher than in the uncoated case. The values slightly vary depending on the complexity of the cutting insert profile and the dimensions of the work pieces dimensions being processed.

Abstract: This study presents new machining types of advanced materials. Super alloys, ceramics and fiber reinforced plastics started being used on a large scale in the last period, this making necessary the development of new machines and machining processes. This paper describes different methods of ultrasonic machining and makes a comparison between them. By ultrasonic machining can be understood a process that involves axial vibrations with a high frequency and low amplitude, for improving the machining conditions like chip flute removal, tool wear and temperature reducing. In this paper, are presented three different ultrasonic machining methods. In the first one, the cutting process is made by abrasive slurry inserted between the tool and the workpiece, in the second one is made by a rotating diamond-brazed tool and in the last one is made by a special drill. This paper aims to study the current status in this field in order to make a research program through collaboration between the Technical University of Cluj-Napoca and the tool company Gühring KG by which to develop ultrasonic drilling.

Abstract: Based on the wide range study of laser gas nitriding (LGN) of commercially pure titanium and the titanium alloy Ti6Al4V by means of high power direct diode laser (HPDDL), the kinetics of nitrogen absorption by the melt pool and related titanium nitrides growth was analyzed. Also a schematic model of nitrogen absorption by the melt pool was proposed. According to the hypothetical model three cases of nitrogen absorption by the melt pool were be distinguished and discussed. It was found that in a case of HPDDL nitriding of the Ti6Al4V alloy the presence of a thin homogenous layer of TiNx on the top surface of melt pool affects the nitrogen absorption kinetics. The process of nitrogen desorption at the cooling stage of melt pool is inhibited by the layer of TiNx as well as by the phase transformation and titanium nitrides formation.

Abstract: Three mechanisms of titanium matrix composite Ti/TiN formation during diode laser nitriding of Ti6Al4V alloy in liquid stage were identified and discussed. When the titanium alloy surface is melted by a laser beam the first mechanism of nucleation and growth of d-TiN was identified in the temperature range of melt pool from 1650 up to 2320 °C, when the nitrogen concentration in the Tia solution reaches at least to the concentration limit in a range 20,5 to 22 at. %. Next different mechanism of nucleation of d-TiN was identified in the temperature range of melt pool from 2320 up to 2950 °C. In turn, the third mechanism of d-TiN formation was identified above the melting point of titanium nitrides, i.e. 2950 °C.