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Assistant Professor, Department of Electronics and Instrumentation Engineering, Faculty of Engineering and Technology
Microelectronics and MEMS
Alex Anandaraj J, S Rajakumar, V Balasubramanian, and S Kavitha
CIRP Journal of Manufacturing Science and Technology, ISSN: 17555817, Pages: 830-838, Published: November 2021 Elsevier BV
Prabhuraj Parasuraman, Rajakumar Selvarajan, Balasubramanian Visvalingam, Rajkumar Ilamurugan, and Kavitha Subramanian
Corrosion Reviews, ISSN: 03346005, Pages: 55-62, Published: 1 February 2021 Walter de Gruyter GmbH
Abstract AA7075 high-strength aluminum alloy, which has many applications in the aircraft, marine and automobile industries, happens to be susceptible to stress corrosion cracking (SCC) when exposed to corrosive environments, resulting in reduced service life of the components. Inappropriate fabrication processes may augment this behavior. The fabrication of AA7075 components using conventional fusion welding processes may produce defects that include hot cracking and porosity. Friction stir welding (FSW) is a solid-state joining process that can avoid these problems and being widely used for components made of aluminum alloys. Because the joining occurs at a temperature that is lower than the melting point of the material, solidification cracking defects can be eliminated. This study investigates the SCC behavior of FSW AA7075-T651 joints. Horizontal-type SCC test was conducted on circumferential-notched tensile (CNT) specimens exposed to 3.5 wt. % NaCl solutions under various axial stress conditions. The different regions of the fractured specimens, such as the machined notch, SCC region and region of ultimate mechanical failure were analyzed by scanning electron microscopy (SEM) to establish the mechanism of SCC. The threshold stress of parent metal (PM) and stir zone (SZ) of the FSW joint were found to be 242 and 175 MPa, respectively.
M. Rajamuthamilselvan, S. Rajakumar, and S. Kavitha
Springer Proceedings in Materials, ISSN: 26623161, eISSN: 2662317X, Pages: 1233-1244, Published: 2021 Springer Singapore
The mechanical reaction of 7075 Al alloy and Al 7075/15% SiCp with 5 μm, 20 μm, and 63 μm metal-matrix composites is investigated using a hot compression sample. In order to achieve the processing map of the studied material following the dynamic material model, the flow stress curves obtained in temperature ranges of 300–500 °C and strain rate ranges of 0.001–1.0 s-1, respectively. All flow instability zones are analyzed by an optical microscope. Microstructural characterization carried out using an optical microscope image analyzer on compressed composite specimens showed safe domains and non-safe domains. The composites of AA7075/20 μm SiCp showed higher efficiency, flow stress, and lower regimes of instability than alloy.
S. Kavitha, K. Sumangala, R. Joseph Daniel, and S. Rajakumar
Lecture Notes in Civil Engineering, ISSN: 23662557, eISSN: 23662565, Volume: 111, Pages: 87-100, Published: 2021 Springer Singapore
P. Rajalingam, S. Rajakumar, V. Balasubramanian, S. Kavitha and M. M. Selvan
Materials Today: Proceedings, eISSN: 22147853, Pages: 799-803, Published: 2021
Abstract The recent developments in aerospace materials to enhance the properties of strength to weight ratio led to the joining of dissimilar metals like aluminum to titanium alloys particularly applied in parts like fuselage of aeroplanes prefer better processes to join dissimilar metals with higher joint efficiency. The major issue in joining of dissimilar materials by fusion welding techniques is the rate at which the metals reaches its melting point and flow of material on melting. This can be overthrown by choosing solid state techniques over the conventional ones. The process of Ultrasonic spot-welding leads to be a better option as the joint produced utilizes lower energy than other solid-state techniques with higher productivity and better joint strength. The experiment was carried out with AA6061-T6 (75 × 25 × 1.5 mm) and Ti-6Al-4V (75 × 25 × 0.75 mm) in lap welded position. The experiment aimed at evaluating the effect of amplitude of welding with other parameters set constant. The samples joined with amplitude 90% of the power of machine exposed maximum load carrying capacity of 2.9 kN. The samples that failed exhibited ductile mode of fracture with the parent materials pull apart from each other. From the experimental results, the joints fabricated with lower welding amplitude resulted in joints with lower strength and with amplitude to the maximum capacity of machine resulted in joint with strength lower than the joint that were fabricated at optimum level.
S. Rajakumar, P. Vimal Kumar, S. Kavitha, and V. Balasubramanian
Metallography, Microstructure, and Analysis, ISSN: 21929262, eISSN: 21929270, Pages: 337-344, Published: 1 June 2020 Springer Science and Business Media LLC
Nimmala Harathi, S. Kavitha, and Argha Sarkar
Materials Today: Proceedings, eISSN: 22147853, Pages: 2621-2625, Published: 2020 Elsevier BV
Abstract Surface acoustic wave sensors have wide variety of applications. The application of SAW sensors includes measurement of different physical parameters like temperature, torque, acceleration, pressure, humidity etc. SAW sensor can also be used as gas sensor with certain construction constrains. The performance of gas sensor can be increased by adding nanomaterial to the MEMS (Micro-Electro Mechanical Systems) based gas sensor. In this study a 2D Surface Acoustic Wave sensor is designed to sense hydrogen gas. The sensor is designed with zinc oxide (ZnO) as sensing layer to increase the sensitivity. The performance of sensor is evaluated with gas and without gas with respect to the displacement and operating frequency. The maximum displacement obtained by the sensor is 0.00857 µm at the operating frequency of 30 MHz in absences of gas and 0.00502 µm displacements in presences of gas at the same operating frequency. Analysis of sensor is done with Finite Element Modeling (FEM). The sensor is simulated with COMSOL Multi Physics.
T. Pragatheswaran, S. Rajakumar, V. Balasubramanian, S. Kavitha, Vijay Petley, and Shweta Verma
SAE International Journal of Aerospace, ISSN: 19463855, eISSN: 19463901, Published: 13 December 2019 SAE International
S. Kavitha, R. Joseph Daniel, and K. Sumangala
Measurement: Journal of the International Measurement Confederation, ISSN: 02632241, Pages: 327-339, Published: 1 November 2016 Elsevier BV
S. Kavitha, R. Joseph Daniel, and K. Sumangala
Mechanical Systems and Signal Processing, ISSN: 08883270, eISSN: 10961216, Volume: 66-67, Pages: 410-424, Published: 2016 Elsevier BV
S. Kavitha, R.Joseph Daniel, and K. Sumangala
Measurement: Journal of the International Measurement Confederation, ISSN: 02632241, Pages: 3372-3388, Published: 2013 Elsevier BV
Abstract Structural Health Monitoring (SHM) using non destructive testing generally involves measurement of shift in natural frequency of the monitored structure. This paper presents the simulation using CoventorWare MEMS design tool and analysis of three bulk micromachined piezoresistive MEMS accelerometers namely device A, B and C that are specifically intended for SHM applications. The devices A and B have been designed for the same natural frequency (100 Hz) but with different geometries. The device C has the maximum deflection sensitivity. The modal, piezoresistive and stress analyses show that beam length ( L ) must be less than the half side length (a) of the proof mass for achieving maximum voltage sensitivity. Thus Device-A has been selected for further analysis and the various performance factors for the Device-A have been obtained using simulation experiments and the results show that this device has excellent voltage sensitivity (3.56 mV/g/V), appreciably smaller cross axes sensitivities (32.8 μV/g/V), very low noise floor ( 4.53 μ g / Hz ) and high resolution (12.72 μg) compared with the already reported piezoresistive accelerometer designed for SHM applications and certain general purpose accelerometers available in the global market. The frequency analysis on two devices (Devices A and D) show that the resonant frequency of the sensor should be low for achieving maximum sensitivity and the damping factor ( ξ ) must be 0.7 for getting the maximum bandwidth over which the sensitivity remains constant (60 Hz). Finally, a standard analytical design procedure for the design of piezoresistive MEMS accelerometers has been developed and presented based on the various observations and results of this study. Further, the design approach for high packing density has also evolved.
Sensors and Transducers, eISSN: 17265479, Volume: 144, Pages: 62-75, Published: 2012
Journal of Structural Engineering (India), ISSN: 09700137, Pages: 29-34, Published: April 2012
S.Kavitha, R.Joseph Daniel, and K. Sumangala
Procedia Engineering, ISSN: 18777058, Pages: 2033-2047, Published: 2012 Elsevier BV