Available online Keywords: EDM PMEDM Silicone carbide powder RSM FEM WLT Total heat flux Fatigue life A B S T R A C TThis paper deals with studying the effect of powder mixing electrical discharge machining (PMEDM) parameters using copper and graphite electrodes on the white layer thickness (WLT), the total heat flux generated and the fatigue life. Response surface methodology (RSM) was used to plan and design the experimental work matrices for two groups of experiments: for the first EDM group, kerosene dielectric was used alone, whereas the second was treated by adding the SiC micro powders mixing to dielectric fluid (PMEDM). The total heat flux generated and fatigue lives after EDM and PMEDM models were developed by FEM using ANSYS 15.0 software. The graphite electrodes gave a total heat flux higher than copper electrodes by 82.4%, while using the SiC powder and graphite electrodes gave a higher total heat flux than copper electrodes by 91.5%. The lowest WLT values of 5.0 μm and 5.57 μm are reached at a high current and low current with low pulse on time using the copper and graphite electrodes and the SiC powder, respectively. This means that there is an improvement in WLT by 134% and 110%, respectively, when compared with the use of same electrodes and kerosene dielectric alone. The graphite electrodes with PMEDM and SiC powder improved the experimental fatigue safety factor by 7.30% compared with the use of copper electrodes and by 14.61% and 18.61% compared with results using the kerosene dielectric alone with copper and graphite electrodes, respectively.
In the present research, layered-functionally graded polymer nanocomposites were made via the silica (SiO2) nanoparticles (14-36 nm in diameter) distributed in the epoxy matrix throughout the ultra-sonication by hand lay–up technique. The change in volume fraction (Vf.) of the nanoparticles was given in the direction of thickness to reach the gradation. Layers having a thickness of (1.2 mm) with different nanoparticles concentrations were consecutively casted in acrylic molds to fabricate the graded composite sheet having a thickness of (6 mm). To fabricate the functionally graded layers, different concentrations of nanoparticles were taken (0, 0.5, 1, 1.5, 2 and 2.5 %Vf) and tested by tensile test. The improvement in the properties of composite samples included the all ratios up to 2% Vf. of the adding filler, and the properties were then decreased. The mechanical property that was studied was the flexural resistance. Flexural properties of three types of FGMs (FGM1, FGM2 and FGM3), isotropic nanocomposite (1% SiO2) and pristine epoxy in order to evaluate their mechanical property, such as Stress–Strain criteria and flexural Young’s modulus, were obtained by 3-point bending test, with loading from pure and composite side for FGM1 and at one side of FGM2 and FGM3 isotropic nanocomposite (1% SiO2) and pristine epoxy. The results manifested that the flexural strength and Young’s modulus loaded from the pure epoxy side was higher than when samples loaded from the composites side for FGM1. The mechanical properties of the epoxy resin and nanocomposites (tensile and compression) and the density for each layer were determined and could be useful for the finite element analysis of the 3-point bending test for FGMs specimens by using Design Modeler (ANSYS Workbench). Experimental results were validated by developing a detailed three-dimensional finite element model. Results of the progressive deformation from the finite element model agreed well with the experimental results.
In this paper, a functionally graded polymer nanocomposite (FGPNC) was arranged via mixing the Alumina (Al2O3) nanoparticles (50 – 100 nm) with an epoxy matrix through five layers of 1.2 mm thickness for each layer using hand lay–up technique. Different volume fractions were taken (0, 1, 2, 3 and 4) % of the used nanoparticles and were cast in molds made from acrylic for creating the graded composite sheet in the thickness direction. The prepared isotropic specimen was tested by tensile and compressive test. The results showed that the (4% Vf of Al2O3) has the best enhancement of the ultimate tensile strength (85.25% from neat epoxy) and decreased thereafter. Flexural properties of three different types of functionally graded materials (FGMs), including FGM1, FGM2 and FGM3, isotropic nanocomposite (2% Al2O3) and pristine epoxy were obtained. Flexural strength and flexural modulus of the functionally graded polymer nanocomposite for each type of FGMs enhanced by (51.7%) and (67%), respectively for the FGM1 loaded from the neat epoxy side, whereas for the FGM1 loaded from the (4%) side, the improvement in these properties was (17.8%) and (29.4%), correspondingly over those for the neat epoxy. For FGM2, the improvement in the flexural strength was (27%) and (71.8%) for the flexural modulus as compared with pristine epoxy. The enhancement in the flexural strength of FGM3 was (27%) and flexural modulus (57.7%). Design Modeler (ANSYS Workbench) was used to verify the experimental flexural test results. A very good agreement was found between the experimental and numerical results with a maximum error of (3.92%) in the flexural modulus for FGM1 loaded from the composite side.
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