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Shunmugam M S
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Shunmugam M S
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Shunmugam M S
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Shunmugam, M. S.
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11 results
Now showing 1 - 10 of 11
- PublicationCharacterization of Geometrical Features of Ultra-Short Pulse Laser-drilled Microholes Using Computed Tomography(01-01-2019)
;Kiran Kumar, K.; High-aspect-ratio high-quality microholes are required in turbine blades to improve cooling performance. These cooling holes are drilled by pulsed laser and hence dimensional as well as geometrical tolerances like circularity and cylindricity are important. The measurement of geometrical features of the microholes is a very challenging task without destroying the components. In the present work, the microholes are produced on Ti6Al4V alloy by ultra-short pulse laser. The geometrical features of microholes are then captured using a non-destructive technique, namely computed tomography. CT-scanned 3D data is directly used for geometrical analysis using open-source software, GOM Inspect. Since algorithms used in the GOM Inspect are proprietary in nature, the extracted coordinate data are also analyzed using the computational methods developed by the authors based on least squares technique. The dimension, circularity, and cylindricity of microholes are compared with the results obtained from GOM Inspect software and a close match is found. - PublicationSampling strategies for verification of freeform profiles using coordinate measuring machines(01-12-2007)
;Rajamohan, G.; Verification of engineering components having freeform profiles on a coordinate measuring machine (CMM) requires accurate measurement of sufficient number of sample points. While the measurement accuracy increases with increased sample size, it is often limited by cost and time considerations. Thus, for a given sample size, the locations of the measurement points are to be determined such that the actual shape may be effectively characterized. Several attempts are reported in the literature. A simple algorithm based on dominant points is proposed in this paper. Simulation studies have been carried out on a freeform profile. Comparison of the results with those obtained from uniform spacing and equi-parameter sampling methods reveals that the proposed method performs effectively. - PublicationEvaluation of straightness and flatness error using computational geometric techniques(01-01-1999)
; The Coordinate Measuring Machines capable of automated measurement are being widely used in on-line and off-line inspection. The measurement data obtained from these inspection devices have to be further processed and analyzed, to assess the geometric form of the manufactured components. In the present work, algorithms based on Computational Geometric techniques have been developed for minimum zone and function-oriented evaluation of straightness and flatness. The algorithms are validated using the simulated data and the data available in the literature. - PublicationEvaluation of circularity and sphericity from coordinate measurement data(20-08-2003)
; The coordinate measuring machines (CMMs) have proven to be reliable, flexible and very much suitable for determining the acceptability of manufactured parts. In this paper, techniques for evaluating circularity and sphericity error from CMM data are presented. The form error can be evaluated directly from CMM data by employing circle/sphere as assessment features and using normal deviations. The CMM data can also be transformed by applying appropriate methods that not only suppress the size but also introduce distortion. The form error is evaluated from the transformed data by employing limacon/limacoid as assessment features and using linear deviations. The methods for handling CMM and transformed data are given in this paper. The proposed methods are validated using the data available in literature. © 2003 Elsevier Science B.V. All rights reserved. - PublicationEvaluation of circularity from coordinate and form data using computational geometric techniques(01-01-2000)
; Data for evaluating circularity error can be obtained from coordinate measuring machines or form measuring instruments. In this article, appropriate methods based on computational geometric techniques have been developed to deal with coordinate measurement data and form data. The computational geometric concepts of convex hulls are used, and a new heuristic algorithm is suggested to arrive at the inner hull. Equi-Distant (Voronoi) and newly proposed Equi-Angular diagrams are employed for establishing the assessment features under different conditions. The algorithms developed in this article are implemented and validated with the simulated data and the data available in the literature. - PublicationEffect of probe size and measurement strategies on assessment of freeform profile deviations using coordinate measuring machine(01-06-2011)
;Rajamohan, G.; Freeform profiles and surfaces have wider engineering applications. Designers use B-splines, Non-Uniform Rational B-splines, etc. to represent the freeform profiles in CAD, while the manufacturers employ machines with controllers based on approximating functions or splines that can cause deviations in manufactured parts. Deviations also creep in during the manufacturing operations. Therefore the manufactured freeform profiles have to be verified for conformance to design specification. Different points on the profile are probed using a coordinate measuring machine (CMM) and a substitute profile is established from the CMM data for comparison with design profile. The sample points are distributed according to different strategies. In the present work, two new strategies of distributing the points on the basis of curve length and dominant points are proposed considering the geometrical nature of the profiles. Metrological aspects such as probe contact and margins to be provided at the ends have also been included. The results are discussed in terms of form deviation with reference to substitute profile and positional deviation between design and substitute profiles, and compared with results of the strategies suggested in the literature. © 2011 Elsevier Ltd. All rights reserved. - PublicationTheoretical and experimental investigations of ultra-short pulse laser interaction on Ti6Al4V alloy(01-01-2019)
;Kiran Kumar, K.; Cooling holes in turbine blades made of high-temperature materials such Titanium alloys are produced by laser processing. A priori knowledge on laser interaction with material will be useful in the selection of laser parameters in practice. In the present work, two-temperature model consisting of a set of coupled Partial Differential Equations in spatial and time domain is used to study ultra-short pulse laser-matter interaction. The model is solved using finite element simulation available in COMSOL Multi-physics software. The present approach is validated taking gold as bench mark material as results for 1D and 2D cases are already reported in literature. The simulation approach is then extended to titanium alloy (Ti6Al4V), the material under investigation in our present work. The simulation results are obtained for 2.00 mm thick Ti6Al4V using 2D axi-symmetric two-temperature model. In order to compare the results, single-shot laser ablation experiments are carried out at laser fluency ranging from 0.84 to 8.4 Jcm−2. A method has been proposed in this work for assessing the crater depth and diameter uniquely from the images of the ablated specimens obtained using laser scanning confocal microscope. The simulation and experimental results are presented and discussed. - PublicationPractical measurement strategies for verification of freeform surfaces using coordinate measuring machines(01-01-2011)
;Rajamohan, G.; Freeform surfaces have wider engineering applications. Designers use B-splines, Non-Uniform Rational Bsplines, etc. to represent the freeform surfaces in CAD, while the manufacturers employ machines with controllers based on approximating functions or splines. Different errors also creep in during machining operations. Therefore the manufactured freeform surfaces have to be verified for conformance to design specification. Different points on the surface are probed using a coordinate measuring machine and substitute geometry of surface established from the measured points is compared with the design surface. The sampling points are distributed according to different strategies. In the present work, two new strategies of distributing the points on the basis of uniform surface area and dominant points are proposed, considering the geometrical nature of the surfaces. Metrological aspects such as probe contact and margins to be provided along the sides have also been included. The results are discussed in terms of deviation between measured points and substitute surface as well as between design and substitute surfaces, and compared with those obtained with the methods reported in the literature. © 2011 Polish Academy of Sciences. All rights reserved. - PublicationAn in-depth investigation into high fluence femtosecond laser percussion drilling of titanium alloy(01-03-2023)
;Kiran Kumar, K.; High fluence femtosecond laser percussion drilling has a potential to produce micro holes for cooling purpose in turbine blades made of titanium alloys due to its short interaction time with the material. For an in-depth investigation, numerical simulation is carried out using 2D axi-symmetric two-temperature and heat conduction models in tandem, mimicking the laser percussion drilling. Moving mesh approach in finite element based COMSOL Multiphysics software is used to arrive at the crater geometry during the ablation process. The heat conduction model provides the value of surface temperature after each pulse. Taking temperature-dependent thermo-physical and optical properties with intraband absorption effect, the simulations are carried out on a 2 mm thick Ti6Al4V plate for 1–15 pulses with fluence in the range of 0.84 to 8.4 J cm−2. For comparison, the simulation results based on room temperature properties are also included. Validation experiments are carried out and the crater morphology is measured using laser scanning confocal microscope. The overall average absolute deviations of the results for crater diameter and depth are within 20% and 40% respectively. The proposed simulation approach is robust and can be used to investigate multi pulses laser ablation process in any other applications. - PublicationEvaluation of sphericity error from form data using computational geometric techniques(01-02-2002)
; The measurement data for evaluation of sphericity error can be obtained from inspection devices such as form measuring instruments/set-ups. Due to misalignment and size-suppression inherent in these measurements, sphericity data obtained will be distorted. Hence, the sphericity error is evaluated with reference to an assessment feature, referred to as a limacoid. Appropriate methods based on the computational geometry have been developed to establish Minimum Circumscribed, Maximum Inscribed and Minimum Zone Limacoids. The present methods start with the construction of 3-D hulls. A 3-D convex outer hull is established using computational geometric concepts presently available. A heuristic method is followed in this paper to establish a 3-D inner hull. Based on a new concept of 3-D equi-angular line, 3-D farthest or nearest equi-angular diagrams are constructed for establishing the assessment limacoids. Algorithms proposed in the present work are implemented and validated with the simulated data and the data available in the literature. © 2002 Elsevier Science Ltd. All rights reserved.