The high strength properties of these composites which make them desirable for several applications also make them difficult to be machinedbythe conventional machining processes. These high strength composites can be machinedby using higher strength tools such as carbide tools and poly crystalline diamond (PCD) cutting tools. In view of high tooling costs and high tool wear rates, machining ofthe MMCs by conventional means becomes uneconomical. Hence, non-conventional machining processes have to be adopted to economically machine these materials. Among the many non-conventional techniques available, Powdermixed Electric Discharge machining (PMEDM) has been found to be effective for processing of metal matrix composites [2,3].
reported that the increasing energy discharge increase instability and therefore, the quality ofthe workpiece surface becomes rougher. Patel et. al (2010) conducted experiments to determine parameters effecting surface roughness. Mild steel as work piece & copper, brass and graphite as tool electrodes with kerosene oil as dielectric fluid where selected for study. The data compiled during experimentation has been used to yield responses in respect ofmaterialremovalrate (MRR) and SR which affects machined work piece and hence tool life. While investigating electric discharge machining (EDM) surface by micrographs, it was observed that molten mass has been removed from surface as ligaments and sheets. In some cases, it is removed as chunks, which being in molten state stuck to surface. All three specimens machinedby different electrodes showed different pattern of HAZs. Singh (2010) presented that the manufacturing industries are facing challenges from different hard materials, as they are hard and difficult to machine, requiring high precision, surface quality which increases machining cost. These challenges are conquered by using non-conventional machining processes to achieve higher metal removalrate, better surface finish and greater dimensional accuracy, with less tool wear. Electric Discharge Machining (EDM), a non-conventional process, has a wide applications in automotive, defense, aerospace and micro systems industries plays an excellent role in the development of least cost products with more reliable quality assurance. The authers presented different reviews ofthe state ofthe art technology of high-performance machining of advanced materials using different EDM technologies. Jahan et. al (2011) reported that the electro discharge machining (EDM) process had the capability of machining intricate features with high dimensional accuracy in hard and difficult‐ to ‐cut materialThe authors reported that the , both EDM and micro ‐EDM processes are being used extensively in the field of mould making, production of dies, cavities and complex 3D structures The research studies related to the developments in electro discharge machining of tungsten carbide using conventional EDM and micro‐EDM are reported in the study. Study presented the problems and challenges in the area of
for performance, quality and cost. The plan of experiments consists of acquiring data in a controlled way, executing these experiments and analyzing the data, in order to obtain information about the behavior of a given process. Two major tools used in Taguchi’s design are signal to noise ratio, which measures quality with emphasis on variation and orthogonal arrays (OA), which accommodates many design factors simultaneously. Orthogonality means that the factors can be evaluated independently of one another; the effect of one factor does not bother the estimation of another factor. The real power in using an OA is the ability to evaluate several factors in a minimum number of tests when compared to full factorial experiments. By applying this technique one can significantly reduce the time required for experimental investigation and can determine which factor has more influence and which has less. In order to improve the performance measures namely surface roughness, cutting speed, dimensional accuracy and materialremovalrateofthe WEDM process several researches were attempted previously. [Aminollah Mohammadi et al. (2008)] optimized machining parameters for improvement of surface roughness in wire electrical discharge turning. [Ramakrishnan and Karunamoorthy (2008)] developed an artificial neural network model for optimization of inconel 718 on machining of CNC WEDM process. [Rao and Sarcar (2009)] evaluated the optimal parameters for machining brass with wire and studied the influence of these parameters on MRR and surface roughness. [Mahapatra and Patnaik (2007)] optimized the wire electrical discharge machining parameters. [Spedding and Wang (1997)] developed responsive surface methodology (RSM) and artificial neural network (ANN) models for the WEDM process. The ANN model is found to fit the data better and have a higher predictive capability of surface roughness value Ra and cutting speed. [Karthikkeyan, et al. (1999)] modeled EDM using a full factorial design while machining silicon carbide particulate composites. [Rozenek et al. (2001)] used a metal matrix composite as work piece material and investigated the variation of machining feed rate and surface roughness with machining parameters. [Tsai and Wang (2001)] adopted neural network models to predict the surface finish. [Qu et al. (2002)] derived a mathematical model for thematerialremovalrateof cylindrical wire-cut EDM process. [Manna and Bhattacharya (2005)] developed a dual response approach for the hard SiC particles ofAl/SiC-MMC which intermittently comes into contact to the hard surface during conventional machining act as small cutting edges like those of a grinding wheel onthe cutting tool edge that, in due course, are worn out by abrasion.
Since, the research work concentrates onthe experimental work, the number of experiments is to be conducted, the effect ofthe individual parameters onthe Wire-EDM, either independently or combinedly have to be studied. Therefore, the well known Taguchi technique is chosen and adopted in the present research work. In order to reduce the total number of experiments “Sir Ronald Fisher” has developed the solution: “Orthogonal Arrays”. The orthogonal array is a distillation mechanism by which the engineers can select the experimental process. The array allows the researcher / engineer to vary multiple variables at one time and obtain the effects such that set of variables has an average and the dispersion. Taguchi employs the design of experiments using specially constructed table, known as "Orthogonal Arrays” (OA) to treat the design process, such that the quality is build into the product during the product design stage.
In the present study, an evaluation has been done onMaterialRemovalRate (MRR), Surface Roughness (SR) and Electrode Wear Rate (EWR) during Electrical Discharge Machining (EDM) of titanium alloy using copper, brass and aluminum electrodes. Analyzing previous work in this field, it is found that electrode wear and materialremovalrate increases with an increase current. It is also found that the electrode wear ratio increases with an increase in current. The higher wear ratio is found during machining of titanium alloy using a brass electrode. An attempt has been made to correlate the thermal conductivity and melting point of electrode with the MRR and electrode wear. The MRR is found to be high while machining titanium alloy using brass electrode. During machining of titanium alloy using copper electrodes, a comparatively smaller quantity of heat is absorbed bythe work material due to low thermal conductivity. Due to the above reason, the MRR becomes very low. During machining of titanium alloy using aluminium electrodes, thematerialremovalrate and electrode wear rate are only average value while machining of titanium alloy using brass and copper electrodes.
Studies were conducted using a T-01M Tester with a ball-on- disc system, designed to evaluate the tribological properties of materials used for parts of machinery and equipment constituting the friction pairs. With this device it is possible to determine the wear resistance and friction coefficient ofthematerial in sliding pairs, depending onthe sliding velocity, surface pressure, presence and type of lubricant, contamination and other factors. The study was conducted in accordance with the methods set out in the ASTM G99 and DIN 50324 standards.
temperature during the modification process, so that the metal in the furnace had to be overheated at higher temperatures; this was joined with the need to use more inoculants. Therefore, the main targets ofthe FLOTRET method were - to stabilize the modification process, to reduce a modifier consumption, to decrease overheating ofthe melt in the furnace, to cut the total time required for modification and to improve hygienic conditions in the workplace. Operational trials of ductile iron production were made onthe melting electric induction furnace of 1000 kg. Required quality of ductile iron corresponds to the standard ČSN 42 23 04.
In the quality assurance system for components cast using the lost wax method, the object of evaluation is the grain size onthe surface ofthe casting. This paper describes a new method for evaluating the primary grain parameters onthe surface of aircraft engine turbine blades. Effectiveness ofthe method has been tested on two macrostructures distinguished by a high degree of diversity in the grain size. The grounds for evaluating the grain parameters consist of geometric measurement ofthe turbine blade using a laser profilometer and of approximation ofthe measurement results using a polynomial of a proper degree. The so obtained analytical non-planar surface serves as a reference point for an assessment ofthe parameters of grains observed onthe real blade surface of a variable curvature. The aspects subjected to evaluation included: the grain areas, shape and elongation coefficients of grains on a non-planar surface ofthe blade airfoil, using measurements taken on a perpendicular projection by means of a stereoscopic microscope and image analysis methods, and by making calculations using the Mathematica ® package.
In the present studies physiological aspect ofthe blood flow has been modeled with a view to estimate the physiological flow parameters such as pressure, against adverse conditions. The study is basically aims at as an advisory and precautionary mode. Efforts have been made to compare the results with practical situations available in the literature with respect to myocardial infarction [heart attack]. Blood flow modeling has paved the way for understanding the intricacy ofthe fluid flow pattern in the human body[1,2].The importance of blood flow in Cardiovascular system has been highlighted by Young. Later the models have been refined by accounting it for pulsatile aspect  and the effects of blood cells [5-6] by using micro-continuum theories [7-9].Effects of body acceleration and magnetism have also been studied onthe blood flows [10-12]. In the present model, blood is assumed to be represented by a couple stress fluids  and the model has been developed for the straight tube [Figure1].
α -SiC particles with average diameter of ∼10 µm were commercially available from Henan Haixu Abra- sives Co. Ltd. α-Al 2 O 3 particles (∼1 µm, with the purity of 99.7%) were prepared by conventional pyrolysis of aluminium hydroxide precursor at 1300 °C for 30 min. A sol-gel method was carried out to coat SiO 2 onSiC particles through the hydrolysis of tetraethyl orthosil- icate, the SiO 2 /SiC volume ratio was 1:5. During the coating process, SiC particles were suspended in dis- tilled water and ultrasonicated for 30 min to break down agglomerates. The pH value ofthe suspension was ad- justed at about 2 by HCl. Tetraethyl orthosilicate in al- cohol solution was then added to the suspension with stirring for 3 h. Then NH 3 ·H 2 O was mixed into the sus- pension and the pH value was controlled at 10–11. The
A amostra metalogr´afica de um material comp´osito (Al/SiC), carboneto de sil´ıcio na liga de alum´ınio, foi produzida pelo Departamento de Engenharia de Materiais, Universidade de Shef- field, Inglaterra. As part´ıculas de segunda fase de carboneto de sil´ıcio tinham uma frac¸˜ao de volume igual a 11%. A ´area da amostra metalogr´afica foi aproximadamente 192 × 288µm. A amostra metal´ografa foi colocada em um analisador de fase ´optico do microsc´opio controlado por computador, o que permitiu o ajuste totalmente autom´atico, a focagem, o posicionamento e a digitalizac¸˜ao da amostra. A ampliac¸˜ao do microsc´opio total utilizada foi de 600 vezes, obtendo- se um tamanho de pixel de 0,375µm. Assim, uma imagem digital foi gerada com ´area igual a 512 × 767 pixels quadrados. A imagem digital bidimensional foi analisada usando t´ecnicas de processamento de imagem para extrair as coordenadas (centros) de cada part´ıcula dentro da ima- gem. A imagem real foi de 512 × 767 pixels, dos quais usamos apenas as part´ıculas localizadas em 512 × 512 pixels, produzindo 419 part´ıculas em amostra S 1 . Os 512 × 512 imagens foram
Presented paper contains evaluation of influence of selected parameters on sensitivity of a numerical model of solidification. The investigated model is based onthe heat conduction equation with a heat source and solved using the finite element method (FEM). The model is built with the use of enthalpy formulation for solidification and using an intermediate solid fraction growth model. The model sensitivity is studied with the use of Morris method, which is one of global sensitivity methods. Characteristic feature ofthe global methods is necessity to conduct a series of simulations applying the investigated model with appropriately chosen model parameters. The advantage of Morris method is possibility to reduce the number of necessary simulations. Results ofthe presented work allow to answer the question how generic sensitivity analysis results are, particularly if sensitivity analysis results depend only on model characteristics and not on things such as density ofthe finite element mesh or shape ofthe region. Results of this research allow to conclude that sensitivity analysis with use of Morris method depends only on characteristic ofthe investigated model.
Good physical and technological properties are the reason why silumins have found wide application in various branches ofthe engineering industry, among others, in aviation, building industry, electronic and electro-engineering industry and, last but not least, in automotive industry. And yet, though offering numerous advantages, silumins are also characterised by a very important drawback. From the technical viewpoint this is their tendency to the formation of a coarse-grained structure, adversely affecting the mechanical properties of castings. For this reason, silumins after the refining treatment should be subjected to modification.
Many types of tool materials, ranging from high carbon steel to diamonds, are used as cutting tools in today‟s metal working industry. It is important to be aware that differences do exist among tool materials, what these differences are, and the correct application for each type ofmaterial. In some particular applications, a premium or higher priced material will be justified. This does not mean that the most expensive tool is always the best tool . The imports of tool damage leads to economic losses like work piece spoiling or poor surface quality. Selection of best process parameters using various optimization techniques will help to solve the problem of improper selection of process parameters. In order to select optimal cutting
The second is the initial nurse/nurse tech resistance that has already been trained in hemodialysis to learn a new and more effortful technique. Sometimes, in addition to the resistance, there is also difficulty to learn the procedure. In addi- tion to the three nurses that implemented the method, we are progressively extend- ing the training to the rest ofthe team. Ofthe eighteen nurse techs, nine have been trained, but two have not adapted to thetechnique. The remaining will start the training. It is possible that a small number of nurses or nurse techs will never adapt to the method.
Although Brazil is one ofthe most important suppliers of raw materials to produce functional and structural components for high performance systems, fundamental and applied research connected with the machining of brittle and hard materials are still incipient. Onthe other hand, the Brazilian commercial balance is usually troubled by mass importation of optical and electronic devices build with advanced ceramics and single crystals. In addition, it is expected that industries installed in Brazil dealing with automotive, aircraft and agricultural machinery will increase their activities in the coming years. If so, an increasing amount of functional and structural components made by advanced materials will be also expected. Under these circumstances, efforts to investigate the machinability of brittle and hard solids by precision manufacturing processes would contribute to the development of a network of domestic suppliers for advanced materials and devices.
Titanium boride (TiB) is characterized by good conductivity, high strength and high melting point. In this work, TiB was used to make Cu-TiB metal matrix composites (MMCs). Amounts of TiB added into Cu matrix were 2wt.%, 5wt.%, 10 wt.% and 15 wt.%. The samples were pressed at pressures of 500MPa, 600MPa, 700MPa and 800MPa and sintered at 820 o and 920 o , respectively. The properties ofthe sintered composites such as hardness and impact toughness were studied. Hardness and impact toughness of samples increased with increasing pressures and decreased with increasing contents of TiB. Composite with good mechanical properties and high conductivity was obtained from the sample containing 2wt.%TiB compacted at 800MPa and sintered at 920 o . It was shown that 2wt.% TiB is a suitable content to make Cu-TiB MMCs with good mechanical properties and excellent conductivity.
Purpose: To evaluate the distance, intermediate and near visual acuity of patients with bilateral cataract operated on both eyes corrected for distance in one eye and for near in the fellow eye, as well as, their stereo acuity and their general satisfaction. Settings: Hospital de Olhos de São Paulo and Complexo Hospitalar Padre Bento - Guarulhos - São Paulo - Brazil. Methods: This is a prospective study of 76 eyes of 38 patients with bilateral cataract aiming to become spectacle free after surgery. The patients were operated on both eyes; the first eye was corrected for distance and the fellow eye for near vision. The refractive error was programmed between -0.5 D and +0.5 D in the first eye and -2.00 D in the second eye. Patients with preoperative corneal astigma- tism equal or higher than 1.0 D were excluded from the study. The uncorrected and best-corrected distant visual acuity (UCDVA, BCDVA) were tested, as well as the uncorrected near visual acuity (UCNVA) and collected at the 3 postoperative months. The Titmus test was performed at the last follow-up. Finally, the modified questionnaire VF-7 was applied and the patient was required to choose, regarding their general satisfaction, between very satisfied, satisfied, or unsatisfied. Results: All patients achieved uncorrected distant visual acuity 20/40 or better (mean SE 0.625 D) and uncorrected near visual acuity J3 or better (mean SE -2.0 D), and intermediate visual acuity J3 in 90%. The Titmus test revealed an average of 197" of arc with reduction of stereo acuity in most of patients as expected and 97.3% of patients demonstrated to be satisfied or very satisfied with this technique. Conclusion: It consists in a viable technique for correction of near, intermediate and distant vision on cataract surgery as demonstrated bythe high rateof satisfaction (97.3%) bythe modified VF-7 questionnaire, especially when the patient has no access to a multifocal intraocular lens.
Short ibers are used in thermoplastic composites to increase their tensile and lexural resistance; however, it often decreases impact resistance. Composites with short vegetal ibers are not an exception to this behavior. The purpose of this work is to produce a vegetal iber reinforced composite with improved tensile and impact resistance in relation to the polymer matrix. We used poly(ethylene-co-vinyl acetate), EVA, to recover the impact resistance of high density polyethylene, HDPE, reinforced with Curauá ibers, CF. Blends and composites were processed in a corotating twin screw extruder. The pure polymers, blends and composites were characterized by differential scanning calorimetry, thermogravimetry, infrared spectroscopy, scanning electron microscopy, tensile mechanical properties and Izod impact resistance. EVA used as impact modiier in the HDPE matrix exhibited a co-continuous phase and in thecompositesthe ibers were homogeneously dispersed. The best combination of mechanical properties, tensile, lexural and impact, were obtained for the formulations ofcomposites with 20 wt. % of CF and 20 to 40 wt. % of EVA. The composite prepared with 20 wt. % EVA and containing 30 wt. % of CF showed impact resistance comparable to pure HDPE and improved tensile and lexural mechanical properties.
After arc plasma electric treatment onthe cross section ofthe surface layer was distinguished two areas with the different microstructure were observed in respect to the parent material. The first area – remelted zone (RZ) and second area – heat affected zone (HAZ). Optical microscopic images of a single track are presented on Fig. 2. The influence of current intensity ofthe electric arc plasma onthe dimensions of RZ and HAZ are shown in Table 2. With increased current intensity (for fixed speed rateof source = 0,2 m/min) the depth ofthe RZ increased too.