PARAMETRIC OPTIMIZATION OF Al-SiC 12 % METAL MATRIX COMPOSITE MACHINING BY ELECTRICAL DISCHARGE MACHINE
In the present study, pure aluminium alloy is mixed with 12% SiC on weight basis to fabricate the metal matrix composite (MMC) material. The objective of this paper is to investigate the effect of process parameters such as pulse on time(Ton), peak current (Ip) and flushing pressure (Fp) on metal removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) during electrical discharge machining (EDM) of Al-SiC12% MMC .The experiment is followed by Central composite design (CCD) method under different combination of process parameters .In this paper Response surface methodology (RSM) is used to develop the mathematical model and to correlate the process parameters with the response. Also Analysis of Variance (ANOVA) technique is used to check the significance of the model and confirmation test is conducted to compare the experimental data with the predicted data to identify the effectiveness of the proposed method. From the main effective plot it is found that peak current is the most significant parameter among the other. Further the morphology study of the composite is carried out by the Field emission Scanning electron microscope (FESEM) of the surface after machining to make a relation with the model.
Influence of mechanical mold vibration on EDM parameters of aluminum-alumina composite
Application of mechanical vibration during solidification of melt is one of the techniques of enhancement the properties of composite. Mechanical mold vibration was applied in amplitude and frequency range of (0-1mm) and (8-25Hz) respectively to pure aluminum reinforced with 5wt% AhO3 particles. The composite was prepared by two-step stir casting method. Electro-discharge machining (EDM) was used in this study. Most of mechanical and physical properties were significantly enhanced with vibration. Brinell hardness was increased by (38%) while porosity and grain size were reduced by (83%) and (43%) respectively. Results indicate that by using vibration material removal rate and electrode wear rate were increased by 18% and 20% respectively, while surface roughness was decreased by 23%. Response surface methodology approach was used to determine an optimum combination of machining parameters to get maximum material removal rate with minimum electrode wear rate and minimum surface roughness.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.