Advanced Materials Research Vol. 1036

Abstract: Deposited on hot work tool steel substrate coating system composed of AlTiCrN film covered by diamond-like carbon (DLC)-based lubricant, was the subject of the studies. The AlTiCrN and DLC layers were deposited by PVD lateral rotating ARC-cathodes (LARC) and PACVD technology on the X40CrMoV5-1 respectively. This paper provides an analysis of the microstructure, mechanical and tribological properties. Several surface sensitive techniques and methods, i.e. High Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscopy (SEM), Raman spectroscopy and ball-on-disk were used to performed study of the coating. TEM investigation shows an amorphous character of DLC layer. It was found that tested AlTiCrN layer has nanostructural character with fine crystallites. In sliding dry friction conditions the friction coefficient for the investigated elements is set in the range between 0.02-0.04. The investigated coating reveals high wear resistance. The coating demonstrated good adhesion to the substrate.

Abstract: The researches in the cutting domain have as purpose the cutting process economic optimization. This paper studies the cutting tool wear at drilling of the stainless steel X20Cr13. The experimental data and their subsequent processing represent the original contribution of the authors to the estimation of polytropic exponents and to the assessment in terms of structure of the calculus relation of the cutting tool wear. The obtained relationship of the cutting tool wear on the tool putting surface at drilling of the steel X20Cr13 permits the determination of the wear on the putting surface, in the case of a couple: stainless steel X20Cr13 - Rp5 high-speed spiral drill, depending on the work parameters and the cutting conditions. Putting the condition of wear limitation, from the obtained relation, the cutting speeds are exactly given. The paper also contains graphs for the variation of the tool wear with parameters of the cutting technology. The results can be taken into consideration in the educational studies and in the theoretical technical research. They can be implemented in the manufacturing activity.

Abstract: This paper studies the cutting moment at widening of the stainless steel X20Cr13. The structure of the cutting moment relation was modified with respect to the relation available in the technical literature for common steels. The tool speed was included in the calculus relation. The experimental data and their subsequent processing represent the original contributions of the authors to the estimation of polytropic exponents and to the assessment in terms of structure of the calculus relation of the cutting moment. The paper also contains graphs for the variation of the cutting moment with parameters of the cutting technology. The graphs are drawn based on the analytic relationship of the cutting moment, obtained in the paper, using the mathematical software Maple. The results presented in this study can be taken into consideration in the educational studies and in the theoretical technical research. Also, they can be readily implemented in the manufacturing activity. Our further studies aim these problems for another steels classes.

Abstract: Microwave technology is more often used in large number of application. Heating polymers by microwave technology is met from domestic o industrial applications and the influences brought by the heating source, the impact between the microwaves and the polymer, to the base material is necessary to be well known to avoid different types of failure of the pieces. HDPE is polymer often used in application with interaction between material and microwaves. Because of that the analysis of the influence of such interaction on the flowing characteristics of the HDPE is proposed in this paper. Experimental programme was applied to HDPE 100 and HDPE 80, both heated by using mono-directional microwave beam with different sets of parameters (factorial experiment principles were used to establish the heating parameters). Plasticity characteristics of the heated material, as elongation and relaxation modulus, were determined by using thermal analysis. It has been recorded important influences of the heating process on the surface in contact with the ceramic powder that was used as microwave absorber. The DSC analysis revealed a decreasing of the elongation with about 16% and decreasing of the relaxation modulus with amount up to 18%, for the material located at the interface between the polymer and the ceramic powder. Each 2 mm from the interface to the interior of the polymer brought an intensity of the modification up to 15% of the values recorded for the interface. After 6 mm from the interface the intensity of the modification decreases very fast. By using DSC thermal analysis it has been analysed the crystallization rate of the polymer modified by the microwave heating and high rates were recorded. About 12% difference between the relaxation modulus of the heated and non-heated HDPE and that means local ageing transformation of the HDPE.

Abstract: This study is part of the concerns that the authors have had in recent years, representing an extension of a research project funded consisting in modelling representative cold rolling processes of profiles. This paper presents a comparative analysis of quality of the superficial layer of a circular profile (grooves) obtained by two different processes: radial rolling with two roller tools and turning with radial feed. Also, the two processes are compared from the viewpoint of economic efficiency. The materials used for the experiments are frequently used to obtain pieces with circular grooves: two types of cementation steel and two types of heat treatable steel. The characteristics of the superficial layer which describe its quality and which are comparatively analyzed in connection to the two processes are: roughness, microstructure and micro-hardness. The economic efficiency of the two processes was assessed by means of the costs implied and the productivity of processing. The interpretation of the results obtained enabled stressing the advantages to generate circular grooves by cold radial rolling from the point of view of the quality of the superficial layer of pieces, as well as the limits of the use of this process from the viewpoint of economic efficiency.

Abstract: It is known that in the cutting processes, due to the parameters variation of the working regimes, to the unevenness of the cutting depth, to the physico-mechanical characteristics of the processed material, to the existence or nonexistence of the coolant oiling, can appear more or less an accentuated wear of the cutting tools. All this factors have a dominant and negative influence on the durability, fact that impose being necessary taking into account some measures to increase the values of the cutting tools and/or of theirs cutting plates durability. In this sense are known various coating by deposition in vacuum researches (vacuum thermal evaporation and condensation from the vapor phase, ionic plating, vapour chemical deposition at low pressure, and so on) of some different filler materials, in thin layers, having protection role for the cutting plates, to increase the edge hardness to the superficial layer and of the tool locating and clearance surfaces and respectively, of their wear resistance. For this purpose, the authors propose to improve cutting tools durability using the deposition method by ionic plating in vacuum (PVD) of the thin titanium layers, following the cutting tools behavior in operation treated in this way. It was so studied the metal carbide cutting plates wear variation, coated with a titanium thin layer and it was determinated the cutting plates durability increasing, in comparison with those untreated. This research is usefull for predicting the lifetime of the cutting tools and/or of theirs cutting plates durability, after the titanium thin layer application, with a significant cost reduction.

Abstract: The curved cutting edge determines a variable chip thickness that leads to various may energetically load along the cutting edge. For twist drill with curved cutting edges, the machining speed variation along the major cutting edge is significant. The points belong to the drills periphery work with an increased machining speed. The thick of the detached chip by these cutting zones downwards to the periphery, versus the thick corresponding to the zones at the drills axis, may leads, in some conditions, to the evenness of the energetically load along the cutting edge, with direct influence regarding the cutting tools wearing mechanism. In this paper are presented modeling with finite elements developed in the Ansys Workbench environment, regarding the energetically load and the temperature state along the cutting edge with variable working angle, characteristic for twist drills with curved cutting edges. The modeling was made comparative with the drill with straight lined cutting edges, for the same working conditions. In the same time, presents an experimental record of an actual process. It was recorded the temperature along the cutting edge with a variable working angle in a turning process with transversal feed. There are presented results of the finite element modeling and of the experiment that simulated the cutting process at drilling. The experimental results of the finite element modeling confirm the trend for temperature evenness along the cutting edge with variable working angle regarding the drills with straight-line cutting edge.

Abstract: Due to the trend of miniaturization on electrical devices, medical devices, and energy, etc., the need for micro and mini metal parts is increasing at a tremendous rate. In order to realize the potential of the mini-parts and take advantages from the mini-forming process, innovative modifications of the forming process must be developed. These modifications are particularly important with respect to the mini-parts forming, which offers an excellent opportunity to produce high accurate mini parts and to reduce manufacturing costs and time. However, severe modifications of the material thickness occur during forming of mini-parts. This paper presents a study concerning the material thickness variation during forming process of mini-parts. The main objective is to understand the material behaviour during forming of mini-parts. The material used in this analysis is copper - zinc alloy with anisotropic properties. During forming process of conical mini-parts, the material become very thin around the punch radius and become thicker at the upper end of the part. This phenomenon cause forming problems such: material fracture, wrinkling, part diameter variation, springback etc. There are multiple factors that affect the material thickness variation during forming process as: side wall angle, friction coefficient, punch radius, and punch speed. The Dynaform 5.9.1 software was used to simulate the forming process. The part obtained after each simulation was analyzed and measured to quantify material thickness variation on the final conical mini-part. To analyze the behaviour of the material during deep drawing process the obtained results for different conical mini-parts were compared. In the final part of this paper some conclusions regarding the material thickness variation during forming of conical mini-parts are presented.

Abstract: The research presented in this paper refers to numerical simulation related to deep drawing of conical mini-parts having different geometries as a function of side wall angle. The mini-parts are made from copper zinc alloy, having the thickness of 0.2 mm. Very important concerns in cold forming of conical mini-parts are the residual stresses due to their influence on the final shape of the part. During the forming process, due to different angles of the side wall, the residual stresses vary. After the mini-part is removed from the forming tools, the residual stresses modify the geometry of the part, causing dimensional errors. The residual stresses decrease the ability of the designer to draw some specific shapes because it may create forming problems such as wrinkling, tearing, and uncontrollable springback. The Dynaform 5.9.1 software was used to simulate the forming process. The part obtained after each simulation was analyzed and measured to quantify the effect of the residual stresses on the final geometry of part. All the parameters were maintained constant excepting the side wall angle. The obtained results for different side wall angles were compared to realize the behaviour of the conical mini-parts during and after deep drawing process.

Abstract: The intensive developments of intelligent manufacturing systems in the last decades open the large possibilities of more accurate monitoring of the metal cutting process. One of the most important factors of the process is the tool state given by the rate of the tool wear, which is the result of a lot of influences of almost all cutting parameters. The modern tool monitoring systems relieved that the accuracy of the results increases when using a combination of surveyed signals such as: vibrations, power consumption, acoustic emission, forces or tool temperature. Combining the output signals in a monitoring function using the neural network method gives the best results when using on-line monitoring. Considering the tool temperature as an important factor in the tool wear process and adding it to the acoustic emission and force measuring the accuracy of the results seems to improve significantly. The present paper describes an integrated monitoring system with integration of the cutting temperature, the calibration device for work piece-tool thermocouple, and the block diagram for on-line survey measuring using LabView platform.