• J RAMKUMAR

      Articles written in Sadhana

    • Excimer laser micromachining of oblique microchannels on thin metal films using square laser spot

      SYED NADEEM AKHTAR SHASHANK SHARMA S ANANTHA RAMAKRISHNA J RAMKUMAR

      More Details Abstract Fulltext PDF

      Excimer laser micromachining of thin metal films with a sacrificial polymer coating is a novel technique that produces features with smooth edges. Using this technique, oblique microchannels are fabricated by workpiece dragging and using a square laser spot, where the axis of traverse of the workpiece is not parallel to the edges of the square laser spot. The microchannels have serrated edges that are particular to the shape of the mask producing the spot. The edge roughness of the channels, machined with a square laser spot of side 100lm, is found to be most affected by the fluence–spot overlap interaction, and the channel width by spot-overlap and the angle of tilt of the traversed path. Polymer coated metal films underwent close to ideal machining, aided by the clamping action of the polymer layer. Through this technique of machining post polymer coating, the edge roughnesses of the microchannels have been curtailed to less than 10 lm, and channel widths to 150 lm. This technique may be used in fabrication of oblique and circular patterns using excimer laser micromachiningwith rectangular and square laser spots

    • Excimer laser micromachining of oblique microchannels on thin metal films using square laser spot

      SYED NADEEM AKHTAR SHASHANK SHARMA S ANANTHA RAMAKRISHNA J RAMKUMAR

      More Details Abstract Fulltext PDF

      Excimer laser micromachining of thin metal films with a sacrificial polymer coating is a novel technique that produces features with smooth edges. Using this technique, oblique microchannels are fabricated by workpiece dragging and using a square laser spot, where the axis of traverse of the workpiece is not parallel to the edges of the square laser spot. The microchannels have serrated edges that are particular to the shape of the mask producing the spot. The edge roughness of the channels, machined with a square laser spot of side 100lm, is found to be most affected by the fluence–spot overlap interaction, and the channel width by spot-overlap and the angle of tilt of the traversed path. Polymer coated metal films underwent close to ideal machining, aided by the clamping action of the polymer layer. Through this technique of machining post polymer coating, the edge roughnesses of the microchannels have been curtailed to less than 10 lm, and channel widths to 150 lm. This technique may be used in fabrication of oblique and circular patterns using excimer laser micromachiningwith rectangular and square laser spots

    • Condition assessment of in-service SAE 10W-30 lubricating oil using spectroscopic and rheological analyses

      SANGHARATNA M RAMTEKE H CHELLADURAI M AMARNATH B S AJAY VARDHAMAN J RAMKUMAR JUNED A SIDDIQUI

      More Details Abstract Fulltext PDF

      Lubricating oil is the combination of base oil and additives which undergo several chemical changes due to oxidation reactions occurring at higher temperatures and pressure. The oxidation reaction produces several oxygenated compounds which lead to degrade the performance of the lubricating oil and adversely affect the engine components, thereby causing frictional and blow-by losses Therefore, the periodic assessment of in-service lubricating oil is necessary to obtain valuable diagnostic information on internal combustion engines (ICE). This paper highlights the results of lubricant degradation analysis carried out on a 4-stroke petrol engine of a newly procured two-wheeler scooter. The experimental studies consider the spectroscopic and rheological analysis of fresh and thermally aged lubricants. Additionally, the effect of thermal degradation on the friction coefficient and wear particle morphology of engine components are also considered in the experimental investigations. The results obtained from oil/wear analysis provide reliable insight to understand the root causes of oil degradation and their effects on friction and wear parameters of engine components operating under normal conditions.

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