Application of Tribometer Measurements for Evaluation of Machinability

Investigation of machinability of materials is continuously faced with new demands, new principles and new achievements. The outcome of evaluation of machinability presented in this paper resulted out from observation of two tribological parameters: friction factor and width of the wear area on contact between two sliding bodies, blocks and discs. Measurements are performed on tribometer in condition of wet sliding while one body is sliding over the other. A block is made of material which is usually used for cutting tool, and a disc is made of material which is used as a material of workpiece. Achieved contact condition (normal loading and sliding speed) meets real machining-cutting condition. The aim of the tests performed on tribometer “Block on Disc” is to evaluate the opportunity of investigation of materials machinability by tribological parameters (friction factor and width of wear area on the block). Comparison of experimental results obtained during real cutting condition setup and tribological setup show a good correlation between wear values and cutting forces. For certain conditions, it is possible to acquire machinability indexes obtained on a tribometer with respect to friction factor and wear on the block as relevant and representative for real cutting condition

Cutting temperature measurement and material machinability

Cutting temperature is very important parameter of cutting process. Around 90% of heat generated during cutting process is then away by sawdust, and the rest is transferred to the tool and workpiece. In this research cutting temperature was measured with artificial thermocouples and question of investigation of metal machinability from aspect of cutting temperature was analyzed. For investigation of material machinability during turning artificial thermocouple was placed just below the cutting top of insert, and for drilling thermocouples were placed through screw holes on the face surface. In this way was obtained simple, reliable, economic and accurate method for investigation of cutting machinability

Modelling of Dross Height in Plasma Jet Cutting Process of Aluminium Alloy 5083 Using Fuzzy Logic Technique

Dross height is an important cut quality characteristic in plasma jet cutting process. It can be defined as molten metal blown from the cutting zone and localized on the bottom of the metal sheet. In each plasma jet cutting process, it is important to obtain dross free cuts. Aluminium is as material very present in shipbuilding and metal industry and because of that very usually cut by plasma jet. Because of high heat and electrical conductivity of aluminium, plasma jet cutting is followed by insecurity about process parameters settings that lead to optimal cut quality characteristics. The aim of this paper is to develop a fuzzy logic model that predicts the influence of variable process parameters on dross height in plasma jet cutting of aluminium alloy 5083. Experiments were performed according to Taguchi L27 orthogonal array by varying cutting speed, arc current and cutting height as input process parameters. Fuzzy logic model was defined using Mamdani inference system. This model was used to investigate effects of variable process parameters on dross height response. In order to analyse interaction effects of plasma jet cutting process parameters on dross formation 3D surface and contour plots were generated. The analysis revealed that the cutting speed has the most significant effect followed by arc current and cutting height. Obtained results of this research indicate that artificial intelligence technique, fuzzy logic, can be effectively used for modelling and prediction of dross formation in plasma jet cutting process of aluminium alloy

Modelling of Kerf Width in Plasma Jet Metal Cutting Process using ANN Approach

In this paper Artificial Neural Network (ANN) model was developed for prediction of kerf width in plasma jet metal cutting process. Process parameters whose influence was analyzed are cutting height, cutting speed and arc current. An L18 (21x37) Taguchi orthogonal array experiment was conducted on aluminium sheet of 3 mm thickness. Using the experimental data a feed – forward backpropagation artificial neural network model was developed. After the prediction accuracy of the developed model was verified, the model was used to generate plots that show influence of process parameters and their interactions on analzyed kerf width and to get conlusions about process parameters values that lead to minimal kerf width

Investigation of the Impact of Hot Forming the Properties of Seamless Steel Bottles for Liquefied Gases

Mechanical tests were performed on samples prepared from the body and the neck of bottles made of seamless tube, steel 34CrMo4. Plastic material flow curves were taken from tensile tests on samples which were made from tubes and finished bottles. Deformation hardening intensity is calculated, and propensity towards brittle fracture is estimated on the basis of the ratio of total elongation and elongation at maximum load. Compared to the samples of quenched and tempered bottle body, quenched and tempered bottle neck samples indicate that characteristics of strength are almost unchanged with an increase in the minimum strain at the destruction from 12,8% to 15,1%. It was concluded that the results of the plastic material flow can serve as a preliminary indication of anomalies that could contribute to unsatisfactory results of the burst test

Effects of NPK rates and ratio on sugar beet yield and quality

Small plot trials were conducted at the experimental fields of the Institute Tamiš, Pančevo, on the lime chernozem soil type over the period 1998- 2003. There were 19 variants in the trial in addition to the control. The NPK amounts ranged from 50 to 130 kg/ha and were used in various ratios. The highest average sugar beet yield was obtained using 100 kg/ha of NPK (59,97 t/ha). The increase amounted to 47,9% compared with the control variant. The average sugar content in the root ranged from 13,67 (N130P50K50) to 14,45% (N0P0K100) and sugar use from 11,05 (N130P50K50) to 12,09% (N50P100K100). The highest average consumable sugar yield was registered using the following fertilizer variant N100 P100K100 (6.98 t/ha) and N100P100K50 (6.81 t/ha). Root yield and consumable sugar yield were greatly affected by the humidity during the sugar beet vegetation period

Numerical Analysis of the Temperature Field in the Cutting Zone in Continuous and Discontinuous Metal Cutting by Turning

Temperature of cutting is a very important indicator of the cutting process. High specific pressures and high temperatures in the narrow cutting zone result in a drop of hardness of the tool material, the intensification of the abrasion and deformation of the cutting elements, losing the cutting abilities, and finally the failure of the cutting tool. The aim of this paper is to calculate the temperature fields using the existing numerical models for the simulation of thermodynamic processes on the wedge of the cutting tool (based on the finite element method). A special accent is given to the numerical calculation of temperatures in the conditions of continuous and discontinuous turning for specific cutting conditions (processing regime, tool geometry and thermo-mechanical characteristics of the tool materials and workpiece materials) using different simulation models. The Third Wave AdvantEdge software package was used for the simulation of orthogonal turning, and some of the results of the calculations of the temperature fields were compared with the results of experimental measurements

VERSCHLIESSFESTIGKEIT DER MARTENSITISCHEN NICHTROSTENDEN STÄHLE MIT OBERFLÄCHENMODIFIKATION FÜR BESSERE KORROSIONS- UND VERSCHLEISSEIGENSCHAFTEN

Na uzorcima korozijski postojanih čelika provedena su laboratorijska ispitivanja te ispitivanja u stvarnim uvjetima trošenja. Elektrokemijska ispitivanja provedena su radi provjere korozijske otpornosti modifi ciranih površina čelika. Na uzorcima korozijski postojanih čelika X20Cr13 i X17CrNi16-2 provedena je metalografska analiza i ispitivanje tvrdoće. Mogućnost primjene modifi ciranih površina na odabranim čelicima provjerena je ispitivanjem uzoraka svornjaka u stvarnim uvjetima trošenja. Uzorci svornjaka zavareni su REL postupkom, a korištena je elektroda Cr-Ni-Mn (18/8/6/). Dobiveni rezultati pokazuju da su indukcijski zakaljeni i naknadno nitrirani martenzitni čelici prosječno postigli otpornost trošenju do tri reda veličine veću u odnosu na dostavno stanje.On test samples of stainless steels, there were conducted laboratory tests and also sample tests in real wear conditions. Electrochemical testings were made towards control of corrosion resistance of modifi ed steel surfaces. On test samples of stainless steels X20Cr13 i X17CrNi16-2, there were conducted metallographic analysis and hardness testing. The possibility of applying modifi ed surfaces of selected steels was cntroled by sample testings in real wear conditions. Test bolts are welded with MMA procedure and it was used electrode Cr-Ni- Mn (18/8/6). Obtained results showed that induction hardened and post-nitrided martensitic stainless steels achieveed for three orders of magnitude bigger wear resistance in relation to asreceived condition.An den Proben der nichtrostenden Stähle wurden laboratorische Prüfungen durchgeführt in den realen Verschleiß Gegebenheiten. Elektrochemische Prüfungen wurden durchgeführt mit dem Ziel der Kontrolle der Korrosionsbeständigkeit bei Stählen mit modifi zierter Oberfl ächenstruktur. An Proben der nichtrostenden Stähle X20Cr13 und X17CrNi16-2, wurden metalographische Analysen und Härtemessungen durchgeführt. Eine Möglichkeit der Anwendung dieser Oberfl ächenmodifi zierten Stähle wurde an Bolzen in realen Verschleiß Gegebenheiten geprüft. Diese Bolzen wurden mit E-Hand und der Cr-Ni-Mn (18/8/6) Elektrode geschweißt. Die Resultate haben darauf eingewiesen dass die induktionsgehärteten und nachträglich nitrierende martensitischen Stähle im durchschnitt eine dreifach bessere Verschleißfestigkeit im Gegensatz zu den Stählen im gelieferten Zustand hatten

Properties of aluminum-steel plates explosively welded using Amonex explosive

Besides their application in munitions and armaments, explosives have a significant role in industrial applications, such as cladding or welding of metal plates. In the process of explosion welding, the energy of explosive detonation is used to achieve a metallurgical bond between two metal components, which are metallurgically compatible, but also those that are non-weldable by conventional methods. For this purpose, most often explosives of low values of detonation velocity are used, in order to avoid severe damage to the processed metal plates. The aim of this study was to investigate the possibility to use the industrial explosive Amonex, which belongs to a group of low-to-middle detonation velocity explosives, for welding of metallic materials. It consists of ammonium nitrate and TNT as energetic components and other inert ingredients and has a powdery consistency, easily applicable in a desirable layer over the metal plates to be welded. Within this research, Amonex was applied to weld plates of aluminium Al 2024 and steel Č0345. Besides the initial data on the used metal plates, the main properties of the used explosives are also given, since based on these properties the needed quantity of explosive was estimated. The procedure of welding was carried out in the configuration of parallel plates, and afterward the welded joint was examined. Ultrasonic method and chemical penetrants were used as non-destructive techniques, and then the samples were cut from the welded plate using water-jet, in order to perform microscopic analyses on the cross-section and to determine the indentation hardness in the area of the joint. It was observed that a good-quality welded joint was obtained, and that the selected explosive may find further application in this area

Multi-objective optimization of cut quality characteristic in CO2 laser cutting stainless steel

U ovom je radu predstavljena metodologija višekriterijske optimizacije karakteristika kvalitete reza kod CO2 laserskog rezanja AISI 304 nehrđajućeg čelika (korozijski postojanog čelika). Za predviđanje karakteristika kvalitete reza kao što su hrapavost površine reza, širina reza i zona utjecaja topline, kreirani su matematički modeli pomoću umjetnih neuronskih mreža. Eksperiment laserskog rezanja je planiran i izveden prema Taguchijevom L27 ortogonalnom nizu, a eksperimentalni podaci su korišteni za treniranje umjetnih neuronskih mreža pomoću Levenberg-Marquardtovog algoritma. Matematički modeli umjetnih neuronskih mreža su kreirani uzimajući u obzir snagu lasera, brzinu rezanja, tlak pomoćnog plina i položaj fokusa kao ulazne parametre. Problem višekriterijske optimizacije je formuliran koristeći metodu težinskih koeficijenata, pri čemu su težinski koeficijenti, na osnovu kojih je izvršena kombinacija karakteristika kvaliteta reza u jednu ciljnu funkciju, određeni metodom analitičkog hijerarhijskog procesa.In this paper, multi-objective optimization of the cut quality characteristics in CO2 laser cutting of AISI 304 stainless steel was discussed. Three mathematical models for the prediction of cut quality characteristics such as surface roughness, kerf width and heat affected zone were developed using the artificial neural networks (ANNs). The laser cutting experiment was planned and conducted according to the Taguchi’s L27 orthogonal array and the experimental data were used to train single hidden layer ANNs using the Levenberg-Marquardt algorithm. The ANN mathematical models were developed considering laser power, cutting speed, assist gas pressure, and focus position as the input parameters. Multi-objective optimization problem was formulated using the weighting sum method in which the weighting factors that are used to combine cut quality characteristics into the single objective function were determined using the analytic hierarchy process method