Danial Ghodsiyeh

The application of surface response methodology to the pretreatment of WC substrates prior to diamond coating

High cobalt (Co) content greater than 10% in tungsten carbide is desirable because Co improves the toughness of the cutting tool. However, the additional Co poses a huge challenge in surface preparation given that the Co content must be reduced to less than 1% on the substrate surface prior to applying a diamond coating. The excessive presence of Co on the substrate surface during coating suppresses diamond nucleation and causes the deterioration of diamond film adhesion. Many attempts have been made to overcome this issue, including the use of chemical etching, mechanical blasting, and heat treatment, but the successful pretreatment of WC-12%Co is still very limited. In this paper, a single-step chemical pretreatment using a mixture of sulfuric acid and hydrogen peroxide solutions was carried out on WC-12%Co. Two independent variables, i.e., etching time and acid temperature, were varied in the experiments to reduce Co contents as well as to roughen the substrate surface. The experimental plan was based on a central composite design. Variance analysis was employed to verify the precision of the mathematical models and their relative parameters. The predicted models generated by the response surface methodology (RSM) were compared with the experimental results, and close agreement was observed. The models demonstrated the significance of both factors, namely, acid temperature and etching time, in reducing Co contents to less than 1% as well as a roughening of the substrate surface within the desirable range.

Effects of Adding Multiwalled Carbon Nanotube into Dielectric when EDMing Titanium Alloy

The low thermal conductivity and gummy-like characteristic of titanium based materials reduce the tool life of cutting tool significantly when machining using conventional processes. Non-contact machining like electrical discharge machining becomes one of the alternative methods to machine these titanium alloys especially when involving complex shapes and geometry. The use of powder-mixed dielectric (PMD) has been successfully applied in machining moulds and dies steel based materials but limited study has been reported on PMD-EDMing titanium alloys. In the present work, EDMing performance of Ti6Al4V using kerosene dielectric with and without adding multi-walled carbon nanotube is compared experimentally. The effects of three controlled parameters, i.e. Pulse ON Time, Interval Time and Peak Current were evaluated on the machined samples. It is found that addition of multi-walled carbon nanotubes in dielectric shows significant improvement in material removal rate (7%) and surface finish (9%) together with reduction in white layer thickness as compared to plain dielectric without powder.

Effect of Tool Wear on Tool Life and Surface Finish when Machining DF-3 Hardened Tool Steel

Hard turning is a dominant machining operation performed on hardened materials using single-point cutting tools. In recent years, hard turning operation has become more and more capable with respect to various machinability criteria. This work deals with machinability of hardened DF-3 tool steel with 55 ±1 HRC hardness at various cutting conditions in terms of tool life, tool wear mechanism and surface roughness. Continuous dry turning tests were carried out using coated, mixed ceramic insert with honed edge geometry. Two different cutting speeds, 100 and 210 m/min, and feed rate values of 0.05, 0.125 and 0.2 mm/rev were used with a 0.2 mm constant depth of cut for all tests. Additionally scanning electron microscope (SEM) was employed to clarify the different types of wear. As far as tool life was concerned, best result was achieved at lowest cutting condition whereas surface roughness values decreased when operating at higher cutting speed and lower feed rate. Additionally maximum volume of material removed is obtained at low cutting speed and high feed rate. Dominant wear mechanism observed during the experiments were flank and crater wear which is mainly caused by abrasive action of the hard workpiece material with the ceramic cutting tools.

Optimization Of Machining Parameters During Drilling Of 7075 Aluminium Alloy

Proper selection of drilling parameters is one of the significant challenges in drilling process. In this study, a new method for selection of optimal machining parameters during drilling operation is investigated. The present study deals with multiple-performance optimization of machining characteristics during drilling of 7075 aluminum alloy. The most commonly-used material in aerospace industry is aluminum alloy with zinc as the primary alloying element. The drilling parameters used for this experiment include cutting speed, feed rate and drill diameter while the two output parameters are surface roughness and dimension error. These outputs are specified to be optimized as a measure of process performance. The statistical model is generated from linear polynomial equations which are developed from different output responses when the machining parameters are changed. The Non-dominated Sorting Genetic Algorithm optimization results show high performance in solving the present problem.

Computational Inteligence in Optimization of Machining Operation Parameters of ST-37 Steel

Optimal selection of cutting parameters is one of the significant issues in achieving high quality machining. In this study, a method for the selection of optimal cutting parameters during lathe operation is presented. The present study focuses on multiple-performance optimization on machining characteristics of St-37 steel. The cutting parameters used in this experimental study include cutting speed, feed rate, depth of cut and rake angle. Two output parameters, namely, surface roughness and tool life are considered as process performance. A statistical model based on linear polynomial equations is developed to describe different responses. For optimal conditions, the Non-dominated Sorting Genetic Algorithm (NSGA) is employed in achieving appropriate models. The optimization procedure shows that the proposed method has a high performance in problem-solving.

Prediction of Rupture in Gas Forming Process Using Continuum Damage Mechanic

The Continuum Damage Mechanics is a branch of applied mechanics that used to predict the initiation of cracks in metal forming process. In this article, damage definition and ductile damage model are explained, and also ductile damage model is applied to predict initiation of fracture in gas metal forming process with ABAQUS/EXPLICIT simulation. In this method instead of punch, the force is applied by air pressure. In this study, first the ductile damage criterion and its relations are taken into account and, subsequently, the process of gas-aid formation process is put into consideration and ductile damage model for prediction of rupture area is simulated using ABAQUS simulation software. Eventually, the process of formation via gas on the aluminum with total thickness of 0.24 [mm] was experimentally investigated and the results acquired from experiment were compared with relating simulations. The effect of various parameters such as radius of edge matrix, gas pressure and blank temperature has been evaluated. Simulation was compared with experimental results and good agreement was observed.