Syed Jawid Askari

Experimental and FEM Study of Serrated Chip Formation in High Speed Turning Processes

The finite element method (FEM) has been used to model high speed turning processes with orthogonal cutting conditions. In most of the situations, continuous chip formation is used to analyze the turning process due to its stability and allowing many conditions to simplify the process. However with the increasing applications of high speed turning, serrated chip formation is becoming a more common phenomenon in metal cutting. Serrated chips usually occur in machining of difficult to cut materials at or above a threshold speed. An updated Lagrangian formulation has been used in this study which works with element deletion technique based on a failure criterion. The Johnson Cook strain-hardening thermal-softening material model is used to model serrated chip formation. In addition high speed turning experiments were conducted on AISI H13 tubes using PCBN to analyze serrated chip phenomenon. The chips were analyzed after surface treatment using scanning electron microscope. It has been found that the length of cuts in the chip increases with the cutting speed and the chip changes from serrated to discontinuous. Different process variables like cutting forces, chip morphology, stress, strain and temperature distributions are predicted at different process parameters using FEM. The results show cyclic variation in the cutting forces at high cutting speeds due to varying chip load.

Practical Evaluation of Sulphur Contents in Diesel Fuel Used by Pakistani Industry for Steam and Power Generation and Establish Relationship between Theoretical and Observed SOx Contents in Exhaust Emission

Rising fuel prices coupled with environmental concerns to arrest SOx emissions is forcing organizations all over the world to adapt new protocols and fuel standards with the aim to lower the sulphur contents in the fuel to keep SOx emissions in check and in tandem equally optimize the capital spending on fuel. The need to adapt to this new reality is even more obligatory for industries in PAKISTAN where power available through national grid is in dire state and industry has to resort to their own resources sources to meet local demand for Steam and Power Generation. This paper presents the fuel analysis of the Unilver factory at Rahim Yar Khan Pakistan. The increase reliance on diesel fuel, for power and steam generation, is a concern at company as it will directly impact their environmental balance sheet due SOx production. Fuel was analyzed as per ASTM D 975 and results were compared with that of supplier certificate and it was observed there was erroneous reporting in sulphur contents. The impact of this deviation was discussed in length along with its bearing on SOX calculations and environmental balance sheet of the company. The results are expected to be first of its kind and may be helpful to Pakistani industries that endeavor to improve their SOx foot prints in factory premises.

Tribological Characteristics of CVD Nanocrystalline Diamond Film Grown by Bias Enhanced Nucleation Process

Nanocrystalline diamond (NCD) films on titanium alloys are of importance for tribology and biomedical implants. However, due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving high nucleation density, it is difficult to deposit adherent NCD films on titanium and its alloys. The aim of this research work is to successfully produce smooth, low roughness and well adherent NCD film on a pure Ti substrate by bias enhanced nucleation (BEN) process using microwave plasma chemical vapor deposition (MWPCVD) method. The friction coefficient was estimated to be around 0.06 in dry air using ball on disk tribometer with reciprocating sliding against a cemented carbide ball of 10 mm diameter at a high contact load of 20 N in dry air. The friction coefficient of bare Ti was between 0.55-06.

Comparison between Water Contents Reported and Actual Water Contents in High Speed Diesel Used for Industrial Power Generation in Pakistan to Establish Relationship between NOx Reported and NOx Observed in Industrial Emissions

Environmental pollution due to industrial emission is becoming a growing problem day by day and Oxides of Nitrogen (NOx) are one of the contributing factors in it. Researchers are in continuous efforts for finding out ways to control these NOx. Out of many, one of the ways to control these NOx is by controlling the volume of water in High Speed Diesel (HSD) used for power generation in Diesel generators (DGs). Water content in HSD provides oxygen for the formation of NOx. Research presented in this paper also revolves around the relation ship between the water contents of HSD and NOx emitted by the DGs. Relevant industrial data of water contents in HSD and NOx percentage in emissions has been collected from selected Industry in Pakistan the largest consumer good manufacturer in Pakistan and one of the largest Multi-national consumer goods manufacturer.

Development of CVD Diamond Thin Films on Titanium Substrate and Study their Tribological Behavior

Abstract: In contrast to their exceptional mechanical properties, titanium and its alloys possess poor friction and wear characteristics. Nanocrystalline diamond (NCD) films appear to be a promising solution for their tribological problem due to their smooth surfaces and small grain size. However, the synthesis of a well adherent NCD film on titanium and its alloys is always complicated due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density. In this work NCD thin films have been deposited on pure Ti substrates in a microwave plasma chemical vapor deposition (MWPCVD) reactor under fixed pressure and methane concentration in hydrogen but over a wide temperature range. The effects of depositing temperatures on the adhesion of films are evaluated using Rockwell indentation tests. It is found that by increasing the deposition temperature the films bonding deteriorates. The films synthesized are characterized by field emission scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and X-ray diffraction.

Deposition of a Well-Adherent Nano-Crystalline Diamond Coating on Titanium Using CH4-H2 Gas Mixture

The deposition of a well adherent diamond film on titanium and its alloys is always complicated due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density. In this work well-adherent and smooth nano-crystalline diamond film was successfully deposited on pure titanium substrate by microwave plasma assisted chemical vapor deposition (MWPCVD) method in CH4/H2 environment. It is found that the average grain size was less than 20 nm with a surface roughness value as low as 28nm. Of particular interest in this study was the exceptional adhesion of approximately 2μm-thick diamond film to the metal substrate as observed by indentation testing up to 150 kg load. Experimental results on growth mechanism and obtaining good adhesion are discussed.

Nanocrystalline Diamond Film Produced by Argon Addition in the CH4-H2 Microwave CVD Plasmas

Diamond coatings on pure titanium substrates are of interest for tribological and biomedical implants. However, due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density, it is hard to deposit adherent thin diamond layers on titanium. The aim of the present research was to successfully produce smooth and well adherent nanocrystalline diamond (NCD) film on a pure Ti substrate using the microwave plasma chemical vapor deposition (MWPCVD) method. The influence of Argon addition to CH4/H2 plasma on the crystallinity, morphology and growth of the diamond film deposited by MWPCVD was investigated using field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), Xray diffraction (XRD) and Raman spectroscopy.