FEM Research Papers - Academia.edu (original) (raw)

The present work is concerned with studying the effect of electrical
discharge machining (EDM) and powder mixing electrical discharge
machining (PMEDM) parameters (pulse current, pulse on time,) using
copper and graphite electrodes on the output response performance
characteristics.
These responses were the induced surface residual stresses, the
material removal rate (MMR), the tool wear ratio (TWR), the workpiece
surface roughness (SR), the white layer thickness (WLT), the total heat flux generated, the workpiece fatigue life and safety factors.
Response surface methodology (RSM) and the design of experiment
(DOE) were used to plan and design the experimental work matrices for
four groups of experiments, two EDM groups using kerosene dielectric
alone, where the second was treated by the shot blast peening processes after EDM machining. The third and fourth groups were done by adding the SiC or graphite micro powders mixing to dielectric fluid (PMEDM). To verify the experimental results, the analyses of variance (ANOVA) were used to predict the EDM and PMEDM performance models for high carbon high chromium AISI D2 die steel in terms of empirical equations. The total heat flux generated, the workpiece fatigue life in terms of safety factors after EDM and PMEDM models were developed by FEM using ANSYS 15.0 software.
The results showed that the copper electrodes induce lower tensile
surface residual stresses by (15.38%) than when using the graphite
electrodes with the kerosene dielectric alone, by (7.51%) and (40.0%) with SiC and graphite powders, respectively and by (33%) with shot blast
peening processes. Using the copper electrodes and graphite powder reduced the induced tensile residual stresses by (79.3%) and (82.6 %) when compared with using kerosene dielectric alone or with SiC powder,
respectively. When the graphite electrodes were used with graphite powder, the MRR was improved by (174%) with respect to the value obtained when using copper electrodes with kerosene dielectric alone.
The best results of (TWR) were obtained when using the graphite
electrodes and kerosene dielectric alone reached (0.1023 %). This result
improved the TWR by (320%) with respect to the corresponding value
obtained when using copper electrodes with kerosene dielectric alone.
The best result obtained when using the graphite electrodes and
graphite mixing powder, which improved the SR by (41%) and (92%)
compared with using copper electrodes with kerosene dielectric alone and SiC powder, respectively. Using the copper electrodes and shot blast peening after EDM improved the SR when using longer shot peening time (60 min.) by (60.24%) compared with using copper electrodes without shot peening treatments.
The copper and graphite electrodes and the SiC powder improved the
SR by (134%) and (110%), respectively compared with the using of the
same electrodes and kerosene dielectric alone.
The WLT reaches its minimum values as (8.34 􀂗m) when using
graphite electrodes, where this means an improvement by (40.0 %) when
comparing with the using of copper electrodes. The lowest WLT values of (5.0 micro-m.) and (5.57 micro-m.) using the copper and graphite electrodes and the SiC powder, respectivelly. This means an improvement by (134%) and (67%) when compared with the using of the copper and graphite electrodes and kerosene dielectric alone, respectively
The graphite electrodes gave a higher total heat flux than copper
electrodes by (82.4 %) when using kerosene dielectric alone. While, using
the SiC powder and graphite electrodes gave a higher total heat flux than
copper electrodes by (91.5 %) and by (285.3 %) and (602.7 %) than using
the copper and graphite electrodes and the kerosene dielectric alone,
respectively.
The fatigue life in terms of experimental safety factor with respect to
as received material using graphite electrodes after EDM and shot blast
peening increased with increasing the shot peening time by (19.10%) and (23.26%) compared with results without using the shot blast peening when using the copper and graphite electrodes, respectively.
The graphite electrodes with shot peening processes improved
fatigue stresses at (10^6 cycles) by (19.58 %) and (23.71 %) compared with the copper and graphite electrodes without shot peening processes,
respectively.
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.
The copper electrodes with graphite powder improved the
experimental fatigue safety factor by (30.38 %) compared with the using of graphite electrodes and by (15.73 %) and (19.77 %) compared with results of group (2) using the copper and graphite electrodes, respectively. The copper electrodes with graphite powder improved the fatigue stresses at (10^6 cycles) by (26.36 %) compared with the using of graphite electrodes and gave a higher fatigue life than the situation when working without mixing powder by (15.83 %) and (19.83 %) using the copper and graphite electrodes, respectively.
Finally, there is a good agreement between the experimental results
and the corresponding values verified by using the optimization process for all cases regarding the input parameters of the EDM and PMEDM
processes, and this proves the accuracy of the models developed by the
RSM and FEM using ANSYS software.