Applied Mechanics and Materials Vols. 592-594

Abstract: Wire Electrical Discharge Machining (WEDM) is a specialized thermal machining process capable of accurately machining parts with varying hardness or complex shapes, which have sharp edges that are very difficult to be machined by the main stream machining processes. This study outlines the development of model and its application to estimation and comparison of machining responses using Multiple Regression Analysis (MRA) and Group Method Data Handling Technique (GMDH). Experimentation was performed as per Taguchi’s L’₁₆ orthogonal array for EN-19 material. Each experiment has been performed under different cutting conditions of pulse-on, pulse-off, current and bed speed. Among different process parameters voltage and flush rate were kept constant. Molybdenum wire having diameter of 0.18 mm was used as an electrode. Four responses namely accuracy, surface roughness, volumetric material removal rate and electrode wear have been considered for each experiment. Estimation and comparison of responses was carried out using MRA and GMDH.

Abstract: The hardness, bending strength, and double shear strength of A356 aluminium alloy was studied under as cast and T6 heat treatment conditions obtained with gravity casting, vacuum casting and squeeze casting methods. The results of these three casting methods have been compared. The hardness, bending strength of A356 alloy after T6 obviously increased; the hardness value of both vacuum casting and squeeze casting has been found to be 62 HRB which is relatively high compared to gravity casting. The bending strength of gravity casting is 299 MPa (22% increase) compared to vacuum casting. However, after T6 heat treatment, the double shear strength values of all these three castings decreases.

Abstract: In general Unconventional Machining Processes (UCMs) or Non Traditional Machining Processes (NTMs) are used only when no other Traditional Machining Processes can meet the necessary requirements, both efficiently and economically. This is because using of most of NTMs incurs relatively higher installation, maintenance, operating and tooling costs. Now-a-days, complicated and intricate shaped structures and drilling of square and micro holes are done using the NTMs. Among the several NTMs available, Abrasive Jet Machining (AJM) is one widely used technique. There are several Process Parameters involved in this process and also have a greater impact on the overall machining performances (i.e.) Material removal Rate (MRR). In this paper a novel approach is made to control the Stand-off-Distance (SOD) at an optimal level to achieve higher MRR using Fuzzy Logic. The Fuzzy controller technique such as Type 1 Fuzzy Logic Controller and Interval Type 2 Fuzzy Logic Controller are compared which tends to control the servo mechanism that actuates the nozzle to maintain the altitude between nozzle tip and workpiece. This experimentation will serve the purpose of handling materials with non-uniform surfaces in them.

Abstract: In this present work the elemental powders pertaining to composition of Al5083 alloy was milled using planetary ball mill (Insmart systems) for 20 h. The elemental powders are loaded in HSS vial with 10:1 ball to powder ratio at 250 RPM. Various parameters such as crystalline size, particle size and morphology have studied using X-ray diffraction analysis and scanning electron microscopy. The crystallite size of the powders determined using Williamson Hall analysis of XRD is 23 nm after 20 h of milling. These nanocrystalline Al-5083 alloy powders were consolidated using ECAP with and without application of back pressure. Physical and mechanical properties such as density and hardness values were measured for sintered and unsintered samples.

Abstract: The forming behavior of AA6061 boron carbide composites produced by stir casting process was investigated with the cold upsetting test. The composites containing 0%, 5%, 10% and 15% of B₄C_p reinforcements were investigated with the cold upsetting test in Universal Testing Machine under tri-axial stress state condition. SEM images were taken to identify the presence of B₄C_p particle in aluminium matrix. From the analysis, it was found that the hardness of composite was increased due to increasing amount of boron carbide particle in the composite and the density was decreased due to the lower value of density of boron carbide. The maximum true axial stress, true hoop stress and hydrostatic stress were gradually increased in the event of increasing order of B₄C_p in the composites. Finally, it was found that in the stress – strain curve, the boron carbide was the main factor in improving the compressive strength of composites because of its high hardness.

Abstract: The fatigue behavior of reinforced composites is complex and the present knowledge of fatigue study still needs extensive investigation of the micromechanical composite behavior. In fiber reinforced composites mechanical properties are highly dependent on their compositions, the matrix type as well as the volume fraction of the reinforcement and their arrangements such as random orientation and distribution, which increase the complexity in the study of fatigue damage behavior. There exist several classes of models to predict the fatigue life or the fatigue degradation of fiber reinforced composites but there exists so far no fatigue model that can be applied to a wide range of fiber reinforced composites. Thus, modifications of fatigue models are always needed in accordance with the micromechanical behavior of different fiber/matrix composites. In this paper the fatigue failure is rectified by using polymer based Kevlar composite material. The design and fabrication involves the design of polymer matrix like as fiber and resin, hardener etc. Kevlar-49 is chosen for as fabricating material to carry out this work. The fabrication set up is made by Vacuum Bag and it is demonstrated satisfactorily.

Abstract: In this work, a new approach for optimizing multiple performance characteristics in turning Al-SiCp metal matrix composite (MMC) is attempted. Desirability fuzzy approach is used to optimize process parameters viz., spindle speed (N), feed (f) and dept of cut (d) that minimizes surface roughness (R_a) and maximizes metal removal rate (MRR). The approach obtains desirability fuzzy grade value for the multiple responses using individual desirability value. The optimum parameters were obtained based on desirability fuzzy grade value and the response table/response graph for each level of the machining parameters was obtained. It is observed that the combination of turning parameters as N=1200 rpm, f=0.22 mm/rev and d=1.0 mm (i.e., N₃–f₂–d₃) were obtained as optimal parameters producing minimum R_a and maximum MRR as 2.64 μm and 33.19 cm³/min respectively. Confirmation test of the predicted result shows that the error is within the range of 1.0 %. This clearly shows the proposed approach is found simple and effective tool for optimizing the complicated multiple performance characteristics.

Abstract: A study has been carried out to investigate the delamination and tensile properties of drilled composites made by reinforcing the natural fibers like hemp, jute, banana and vakka into a polyester resin matrix. The fibers extracted by retting and manual processes have been used to fabricate the composites. These composites are tested for delamination and tensile strength after drilling and compared with those of established composite like glass made under the same laboratory conditions. The Taguchi method with orthogonal array of L9 (34) was selected to realize the influence of the drilling parameters (cutting speed and feed rate) on delamination and tensile strength for various fiber reinforced composites. The results indicate that the delamination of the drilled natural fiber composites were in some cases better than those of glass fiber composites.

Abstract: In this study, a model for the melting efficiency of Gas tungsten arc welding (GTAW) was developed and validated using experiments. It was found that the melting efficiency increases with current, speed, arc length and electrode tip angle. The melting efficiency is found to be stable with increase in electrode diameter. The results were compared with existing studies.

Abstract: In this work, friction welding of AISI 52100 grade steel rods of 12 mm diameter was investigated to predict the value of tensile strength. The Joints made with various process parameter combinations were subjected to tensile tests. The primary process parameters are considered in ratios (friction pressure/friction time, forging pressure/forging time, rotational speed/sec). This is done to make as three factors. Here, the three factors, five levels, central composite, rotatable design matrix are worn to optimize the required number of experiments. The Empirical relationships were developed by Response Surface Method (RSM). The adequacy of the models was checked through ANOVA technique. Through using the developed Empirical relationship, Ultimate Tensile Strength (UTS) of the joints can be predicted by means of 95% confidence level.