Advanced Materials Research Vols. 264-265

Abstract: Machining of titanium and its alloys is still the subject of research and researchers’ interest despite some improvement in its machinability from several machining methods. This research presents performance of nitrogen gas in machining titanium. Machining of titanium is carried out on conventional turning center with triangular insert and holder according to ISO designation. Compressed nitrogen gas contained a cylindrical tank is supplied to the cutting zone via speciallydesigned valve that controls pressure and volume of nitrogen. The gas outlet pipe of diameter 2 mm is directed to just-above the tool rake face. During machining, the gas is supplied with high pressure so that the cutting zone receives an effective cooling as well as the chip will easily break. The effectiveness of this new cooling strategy is demonstrated by tool condition after machining, and also by comparing with performance of conventional coolant. The result is found to be excellent in terms of relative amount of tool wear. The cutting insert has surprisingly been almost intact when using nitrogen gas as coolant whereas tool wear at failure state has occurred with conventional coolant for the same machining parameters.

Abstract: The work presents a study of surface roughness of pieces of magnesium UNS M11311 obtained by dry turning. The study is focused in repair operations of this type of materials when they are used as inserts of metalic hybrid components. Therefore, the main limitations of this research are the values of the cutting conditions used; especially low in comparison with the usually values of these parameters used in the production of the magnesium. The followed methodology consists of a series of tests of dry horizontally turning carried out with tools of different coatings and under different cutting conditions. The design of experiments has been made by means of fractional factorial orthogonal designs and the analysis of the results by the ANOVA method. The principal result is one ranking for the combinations of cutting conditions and tool coatings based on the surface roughness expected given by the mathematical model. As first conclusion, it is possible to affirm that, the best surface finishes are obtained for low feeds. Cutting tools used in the machining of other types of materials (steel, stainless steel) can be used obtaining a quality of the surface finish similar to that obtained with tools for specific use of non-ferrous metals.

Abstract: Melt compounding technique was employed to prepare thermoplastic natural rubber (TPNR) nanocomposite. The ultrasonic bath was used to improve the filler-matrix interfacial adhesion. TPNR nanocomposites were prepared in the ratio of (70:20:10) from polypropylene (PP), natural rubber (NR) and liquid natural rubber (LNR) as a compatibilizer, with 4% NanolinDK4. The clay layers were found to be separated further with ultrasonic treatment as compared to the sample without ultrasonic treatment as exhibited from X-ray diffraction. Young's modulus, tensile strength and elongation at break of TPNR nanocomposites increased with ultrasonic treatment, the optimum results achieved at 3h. .The results obtained from dynamic mechanical analysis (DMA) curves indicate that the addition of MWNTs led to an increase in the storage modulus E' and loss modulus E'' with maximum value is obtained at 3 hours. The glass transition temperature (Tg) also increases with Ultrasonic treatment. Ultrasonic treatment can promote the dispersion of the clay in TPNR also improve the compatibility of organoclay filler and the TPNR matrix.

Abstract: Electrical Discharge Machining (EDM) is one of the most widely used non conventional machining processes for removing material from workpiece by means of a series of repeated electric discharges. This process is now one of the main techniques used in die production and has good accuracy and precision with no direct physical contact between the electrodes so that no mechanical stress is exerted on the workpiece. Electrical discharge milling (ED-milling) is an emerging technology where a cylindrical tool electrode follows a programmed path in order to obtain the desired shape of a part. The current investigation aims to optimize the process parameters during EDM milling of stainless steel by using copper electrode. The selected input parameters used for the study are voltage, rotational speed of the electrode and feed rate while the responses are material removal rate (MRR), electrode wear ratio (EWR) and surface roughness (Ra). Response surface methodology is used in the study. The experimental design is formed by using design expert software. Central Composite design (CCD) is used to identify the optimum operating condition in order to obtain maximum MRR, minimum EWR and minimum Ra as response. The result shows that the machining parameter setting of voltage 120 V, rotational speed of electrode 1200 rpm and feed rate 4μm/s, gives optimized responses MRR 5.0259 x 10-3 mm3/min, EWR 53% and Ra 0.79 μm.

Abstract: Titanium nitride-aluminium oxide (TiN-Al2O3) is a new generation ceramic composite material having potential for many industrial applications as it possess high resistance to thermal degradation, anti-wear and anti-abrasion properties. In the present research the characteristic features of EDM process are explored through Taguchi methodology based experimental studies with various process parametric combinations. Finally the process has been optimized using Genetic algorithm based Pareto optimization search. From Pareto optimal search the technology guideline for optimal parameter settings have been selected. The present research approach is extremely useful for maximizing the productivity while maintaining the geometrical accuracy within desired limit.

Abstract: This paper introduces a new tool breakage diagnosis technique by using a support vector machine (SVM) in face milling. From the viewpoint of frequency domain, the paper is focused mainly on the diagnosis with spectrum of cutting force signals. With the spectrum, the SVM is learned to adapt the diagnosis. As the substantial benefits in classification, the system, joined the spectrum input and the SVM learning, is capable of responding in real-time to diagnose automatically when a tool fracture occurs even under the varying cutting conditions, and is really admissible to monitor the machining tool with or without breakage. As for the experimental results, they show that this new approach could sense tool breakage in a wide range of face milling operations.

Abstract: Silicon being a typical hard-brittle material is difficult to machine to a good surface finish. Although ductile-mode machining (DMM) is often employed to machine this advanced material but this technique requires the use of expensive ultra-precision machine tools therefore limiting its applicability. However, by proper selection of grinding parameters, precision grinding which can be performed on conventional machine tools can be used to generate massive ductile surfaces thereby reducing the polishing time and improving the surface quality. Precision grinding should be planned with reliability in advance and the process has to be performed with high rates of reproducibility. Therefore, this study investigated the effect and optimization of grinding parameters using Taguchi optimization technique during precision grinding of silicon. Experimental studies were conducted under varying depths of cut, feed rates and spindle speeds. An orthogonal array (OA), signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) were employed to find the minimum surface roughness value and to analyze the effect of the grinding parameters on the surface roughness. Confirmation tests were carried out in order to illustrate the effectiveness of the Taguchi method. The results show that feed rate mostly affected the surface roughness. The predicted roughness (Ra) of 34 nm was in agreement with the confirmation tests. Massive ductilestreaked surface was also found corresponding to the minimal surface finish determined from the optimal levels.

Abstract: Cost structuring of new technology is a critical mission which needs to be developed systematically to get accurate cost estimation. In this research a new approach was proposed and developed for cost structuring a new process. Cost modeling roadmap was proposed to guide the development of genetic cost model by integrating different cost estimating methods and supporting the optimum solution by using statistical techniques in modeling the cost in high speed hard turning, then by building logical relationships between the different effective variables through three levels of cost drivers; main drivers, process and technical drivers and final drivers. Finally a matlab model was developed for simulating the final cost drivers to study the effect of different parameters on the cost drivers.

Abstract: The present work studies some aspects of turning process applied on mild steel using cermets tools at high speed cutting (1000mm/min) by using negative rake angle (0 to-12). The influence of increasing the cutting speed and negative rake angle on flank tool wear, cutting forces, feeding forces and tool temperature were analyzed. The research studies and concentrates on the tool life estimation and the effect of the negative rake angle and higher cutting speed on tool life. It was found that the maximum tool life is obtained in (-6) rake angle for the cutting parameters.

Abstract: In the area of grit blasting, it is well known that microscopically small abrasive debris gets trapped on the surface, and due to impact the grits might cause the surface to fracture and a fraction of it to be embedded. The same problem appears in abrasive water jet (AWJ) machining especially in the so-called deformation wear zone or striation zone. The major aim in this study is to investigate the abrasive contamination on mild steel cutting surface. In the present study mild steel was used as the work material, since it is widely used in many industries. In order to analyze the pattern of the contaminations on the cut surface, the selected process parameters were abrasive flow rate, pressure and work feed rate. Abrasive contamination was measured at different depths along the path of the abrasives. The three selected zones for measuring abrasive contamination at different depths were the primary impact zone, the smoother zone and the deformation wear zone. It was found that contamination at the middle zone, i.e., the smoother zone had the least abrasive contamination while the initial impact zone and the deformation wear zone showed high abrasive contamination. It was also found that a higher pressure reduces abrasive contamination while a higher abrasive flow rate and work feed rate increase abrasive contamination.