Applied Mechanics and Materials Vols. 110-116

Abstract: Abrasive waterjet machining has been recently considered as a promising, emerging non-conventional technology with an extensive growth in its market share and research activities. In this paper, a Europe’s first 5-axis AWJ system established at the University of Nottingham will be introduced followed by some of the research works explored on the capability of AWJ machining (e.g. AWJ cutting, AWJ drilling, AWJ milling, AWJ turning) on exotic materials such as Ti-based alloys at different niche applications. Thanks to advances in the complementary AWJ technology (e.g. ultra-high pressurized pump) and advanced machine designs (e.g. multi-axis machine movement), it was found that the machining capability of abrasive waterjet (even plain waterjet) can be extended if innovative strategies are applied.

Abstract: In this paper, statistical and regression analysis of material removal rate using design of experiments is proposed for WEDM operations. Experimentation was planned as per Taguchi’s mixed orthogonal array. Each experiment has been performed under different cutting conditions of gap voltage, pulse ON time, pulse OFF time, wire feed and dielectric flushing pressure. Stainless Steel grade 304L was selected as a work material to conduct the experiments. From experimental results, the material removal rate was determined for each machining performance criteria. Analysis of variance (ANOVA) technique was used to find out the variables affecting the material removal rate. Assumptions of ANOVA were discussed and carefully examined using analysis of residuals. Variation of the material removal rate with machining parameters was mathematically modeled by using the regression analysis method. The developed model was validated with a set of experimental data and appeared to be satisfactory. Signal to noise ratio was applied to measure the performance characteristics deviating from the actual value. Finally, experimental confirmation was carried out to identify the effectiveness of this proposed method.

Abstract: This paper presents an attempt to develop an approach to predict the optimal process parameters for the Hole punching process on sheet metal. The Taguchi method is used to define the experimental procedure by its orthogonal array. The multiple responses of the Hole punching process, hole diameter and hole offset are optimised by the Grey Relational Analysis procedure. The statistical analysis of variance reveals the significant parameters which affect the process by analyzing the input parameters with the grey relational grade. The Non linear model obtained by this analysis is further processed by a Meta heuristic algorithm to obtain the optimality.

Abstract: Stress distribution in Carbon Nanotube (CNT) reinforced composites is studied using nonlocal theory of elasticity. Two nearby CNTs are modeled as two circular inclusions embedded in an infinite elastic medium, and classical stresses are obtained using the complex stress potential method. Nonlocal stresses are calculated using nonlocal integral elasticity equation. Effects of the distance between CNTs as well as effects of the nonlocal parameters on the stress distribution and stress concentration are studied. For unit normal stress at infinity, stress at the interface of the CNT and matrix increases from 0.1 for classical analysis to 0.85 for nonlocal analysis. Furthermore, when two CNTs approach to each other radial and hoop stresses across the interface increases. It is interesting that, results of the nonlocal and classical elasticity for the hoop stress are different completely.

Abstract: Carpal Tunnel Syndrome (CTS), a type of Repetitive Strain Injury (RSI) is the most commonly work related musculoskeletal disorder (WMSD) that can lead to temporary as well as permanent disabilities. The CTS is marked by pain and paresthesia. Present study has been conducted on the 60 workers comprising of 46 men (mean age of 34.43 ± 8.40 years, range 18-52 years) and 14 women (mean age of 34.78 ± 9.14 years, range 22-50 years) engaged in Ethylene Propylene Diene Monomer (E.P.D.M.) assembly unit. Symptoms present are nocturnal pain, numbness, tingling and low hand grip strength. The study has been done in actual industrial environment through health surveillance, Phalen’s and Tinel’s Tests, hand grip strength tester, and weighing machine. The aim of this study is to do analysis to check the susceptibility of CTS symptoms amongst men and women on the basis of repetitive and non repetitive work. The F-Test and ANOVA using orthogonal array have been applied for statistical data analysis in order to quantify and evaluate the importance of possible symptoms on CTS risk factor. Analysis shows that the women workers are more susceptible to CTS symptoms than their male counterparts. It also reveals that grip strength below 35 Kg and high tingling prevalence ratio are the most alarming symptoms for CTS occurrence among workers in E.P.D.M assembly unit.

Abstract: Electromagnetic forming (EMF) is a high energy rate forming (HERF) process. It is a high speed forming process using a pulsed magnetic field to form work pieces made of metals such as copper or aluminum alloys with high electrical conductivity. The work piece to be deformed will be located within the effective area of the tool coil so that the resulting type of stress during the forming process is determined by the type of coil used and its arrangement as related to the component. Tubular or structural components can be narrowed by means of compression coils or widened by means of expansion coils, where as sheet metal can be deformed by flat coils. In this work, the experimental investigation and simulation of electromagnetic compression forming of aluminum alloy tubes is studied. The aim of the paper was to verify the results from Finite element methods with experimental data. Experiments were conducted on Tubes of outer diameter 40 mm and wall thickness of 2 mm with a nominal tensile strength of 214 MPa. The tube was compressed using a 4 turn helical actuator discharge that can be energied up to 20 kJ. A field shaper made of aluminum was used. A Maximum reduction of 15.85% in diameters were measured. The same problem was simulated in ANSYS using static coupled electromagnetic analysis. The results of the Simulation showed good correlation with experimental results.

Abstract: This paper describes a research work to explore the utilization of macros in an effort to improve an overall machining efficiency. Latest models of CNC machine are equipped with many functions and resulting difficulty in creating NC program. Feature based machining is optimizing the capabilities of CNC machine. A novel framework of a feature based machining system using macros is discussed in this paper by applying some normally used features and work material in manufacturing industry. Experiments has been conducted in proving its functionality. This system found enable to reduce pre-machining setup time and easy to used. Lastly, a graphical user interface is proposed.

Abstract: In this work, systematic substitution of ZnO with SnO₂ in ZnO-based varistor composition was investigated through analysis of densification, phase formation, microstructure and non-linear properties. The general formula was Zn_0.96-xSn_xBi_0.02Co_0.02O_β with x = 0, 0.01, 0.02 and 0.04. The high rate of densification starting at 800°C is believed to be related to Bi₂O₃ via liquid-phase sintering. The complex nature of this multi-phasic varistor system was demonstrated through occurrence of different phases at different sintering temperatures. The low-temperature pyrochlore (Bi₂Sn₂O₇) started to dissociate at approximately 1100°C with the spinel (Zn₂SnO₄) forming afterwards. The grain size variation with composition might be induced by the changes in the availability of Bi₂O₃ which has been reported to help facilitate abnormal grain growth. All samples sintered at 1200°C, with data extrapolation, possessed breakdown voltages of higher than 1400 V/cm.

Abstract: After this tragic accident of Colombia's shuttle the continuance of these spatial functions were encountered with ambiguity and lots of suspicion was formed in the NASA officer's brain. The burst was formed because of the defect which was made in the outer insulator fuel tank, a insignificant piece of insulator that was separated while throwing the Colombia's shuttle from the fuel tank under the aerodynamical force of throw (while separating the tank from the shuttle) and it hurts the ledge of the left wing of the shuttle in the place of ceramics insulator defect and shuttle's thermal safety system. It was happened in throwing the shuttle discovery too, however they relief the damaged parts through a spatial marcher in the space and they turn it to the earth with so much presentiment. In this essay we present a new design for the fuel tank and shuttle. In this model, shuttle is set on the top of the fuel tank and while separating the tank from the shuttle, the probable separating pieces, wouldn't be defect to the shuttle. In this procedure because the tank has a motor, a cart landing and a control system, it is again useful and would make the economy in the charges. In this Method by putting shuttle on top of the tank, it may not make any hurt to the thermal shield and there weren't any accident accession like the Colombia's shuttle accident and There wouldn't be any requirement to design a new space crafts with the passenger to go and return, and according the heavy costs of the researches, temptation and long time providence it would be much and According to probability of returning the fuel tank to the earth, in other throwing there would be multiple providence that can be a justification for this project And also Changing the tank place improves the aerodynamical coefficient in comparison present shuttle's picture that will cause to reduce using the fuel.

Abstract: When pressure head of one point of pipeline drops to saturated vapor pressure head in water hammer, column separation occurs. Occurrence of column separation might result in some damages in pipeline or other equipment in the system. In discrete vapor cavity model as the solving model, cavities could form in any computational grid specifically in high elevated regions of pipeline. In this study the numerical results are compared with the experimental data and shown having a good agreement together. Moreover, the effects of pipe diameter, flywheel effect, and pump specific speed on transient flow behavior are investigated. It is shown that pressure head for pumps with higher specific speed and inertia have a lower peak amount.