Optimization of Electro Discharge Machining Parameters on Mg / SiC P-Metal Matrix Composites by Response Surface Methodology
Metal Matrix Composites (MMCs) are present engineer ing materials which have more advantages when compare to conventional materials. Magnesium based MMCs among the MMCs have become an important resear ch subject because of their low density and high stren gth/weight ratio in recent years. The aim of this s tudy is to find out the most influence factors of the electro-disch arge machining (EDM) process parameters. The specim ens were used as Mg/SiCp metal matrix composites. The specim ens were prepared by the powder metallurgy techniqu es. Brass tool with diameter of 10mm was used to machin e the specimens. Experiments were conducted under d iff rent conditions of pulse on time (Ton), pulse off time ( Toff), current (I). The output responses measured w re material removal rate (MRR) and Tool wear rate (TWR). Mathem atical models are proposed for the above responses using response surface methodology (RSM). The analysis of variance (ANOVA) was carried out to study the effe ct of process parameters on process performance.
The drilling of an Al/SiC metal-matrix composite
Abstract Because of the hard ceramic reinforcing component in a metal-matrix composite, these materials are difficult to machine and attempts to do so result frequently in accelerated tool wear and premature failure. This paper reports on the results from a series for drilling tests undertaken on a 25% volume fraction Al/SiC metal-matrix composite. A range of tool materials was tested, these including: coated and uncoated high-speed steel, carbide and PCD-tipped drills and solid-carbide drills. The results indicate that the hardness of the tool material has a significant influence on cutting-edge wear and on the drilling-torque and thrust-forces experienced. It was found also that the presence of a ceramic coating on a high-speed steel drill does not improve its performance appreaciably, compared to standard un-coated tools.
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.