Publications

Coordinate Measuring Machine (CMM) is widely used for the accurate profile deviation evaluation of free-form components. Sampling, measurement and evaluation of the measured data are the most important steps of the CMM measurement process. Though various sampling strategies were proposed to reduce CMM measurement time, few error evaluation techniques have been reported to date. Generally, the CMM measured points are either fitted or registered with the continuous reference profile. The profile deviation is estimated using the point-inversion technique with relatively high time complexity. Hence, an alternate method is needed for quick and accurate profile deviation estimation.

Laser direct metal deposition (LDMD) is a rapidly emerging additive manufacturing technique offering attractive characteristics like high deposition rates, component repair, and deposition of functionally graded materials. Experimental investigations have been carried out to deposit SS 316L structures at higher deposition rates using LDMD. A continuous fiber laser operating at a wavelength of 1070 nm is used to deposit the structures under different processing parameters like power, scanning speed, and powder feed rate. A power range of 600 W to 1200 W is found to be optimal with speed varying in the range between 10 mm/sec and 25 mm/sec. At low power with higher velocities, a low layer thickness is obtained and vice-versa. With an increase in the power and the decrease in the speed, deposition rates are increased. The findings will help to develop pre-processing, online-processing, and post-processing strategies for LDMD.

Nickel-based alloys (Nimonic 90) are one of the most used materials for aircraft parts, gas turbine components and fasteners due to their inherent properties such as high strength at elevated temperature, good corrosion resistance, high stability, high wear resistance and low thermal conductivity. Because of the above-mentioned properties, Nimonic 90 alloy is difficult to machine, and the roughness obtained by machining of nimonic alloy is comparatively rough. The existing theoretically developed mathematical equations for roughness measurement do not consist of all the machining parameters. It lacks some of the effective roughness parameters such as depth of cut, spindle speed and cutting-edge angle. This article proposes a novel mathematical/geometrical model for the prediction of surface roughness using fundamental geometrical properties of tool and workpiece. For developing the mathematical model

Coordinate Measuring Machines (CMM) are widely used in form inspection of free-form surfaces. Generally, the form error at each measured point is estimated using the widely known and accurate point-inversion method. This method has relatively high time complexity and cannot be preferred for fast inspection. Hence in this work, an alternative two-stage methodology based on the concept of the Voronoi diagram is proposed. In the first stage, the poles data is extracted from the Voronoi diagram of the discretized surface. In the second stage, the form-error-estimate algorithm executing in O(m log n) time estimates the errors using the poles data and the discretized surface. Numerical and experimental implementations are executed using NURBS surfaces. The proposed method’s accuracy is on par with the point-inversion method and is 94.97% faster than the latter. Hence this method can be used for fast and accurate CMM and CNC based (in-situ) free-form surface inspection.

Surface engineered components with micro/nano scale periodic surface structures are having a wide range of industrial applications, owing to their unique tribology enhancing characteristics. Generally, design and development of highly controlled sub micro-scale structures with intricate feature characteristics are highly challenging for the manufacturing industries, especially super alloys like titanium due to its inherent low thermal conductivity and higher chemical reactive property. This forms the major objective of the present research work emphasizing the methodology-hatching technique (dot and line) to create highly controlled micro/nano scale periodic surface structures. The recently widespread femtosecond pulsed laser processing can be an efficient alternative method for the usual industrial practice of generating periodic surface structures. Femtosecond pules hatch pitch was varied from 10 to 50 μm