S.Kavitha
@annamalaiuniversity.ac.in
Assistant Professor, Department of Electronics and Instrumentation Engineering, Faculty of Engineering and Technology
Annamalai University
RESEARCH INTERESTS
Microelectronics and MEMS
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
P. Rajalingam, S. Rajakumar, V. Balasubramanian, Tushar Sonar, and S. Kavitha
Springer Science and Business Media LLC
P. G. Sam Infant Jones, S. Rajakumar, S. Kavitha, and V. Balasubramanian
Springer Science and Business Media LLC
P. G. Sam Infant Jones, S. Rajakumar, S. Kavitha, and V. Balasubramanian
Springer Science and Business Media LLC
R. Jayaraman, R. Girimurugan, T. Sankaramoorthy, Ram Subbiah, and S. Kavitha
AIP Publishing
P. G. Sam Infant Jones, S. Rajakumar, S. Kavitha, and V. Balasubramanian
Springer Science and Business Media LLC
Sashank Sravan, S. Rajakumar, Karthikeyan Rajagopalan, and Kavitha Subramanian
Emerald
PurposeDissimilar joining of austenitic stainless steels and ferritic steels is a challenging task and has a wide range of applications due to its excellent mechanical and thermal characteristics. They are joined mostly by using conventional modes. In the current investigation, the study and optimization of hot wire TIG welding parameters was carried out.Design/methodology/approachThese parameters will govern the desired characteristics of the joint. Solutions were found out through multi-response optimization by using response surface methodology and single response optimization using particle swarm optimization.FindingsOptimized input welding parameters that were achieved are electrode current 180 amps, wire feed rate 1870 mm/min and hot wire current 98 amps and the optimized UTS is 665.45 MPa. The results from PSO were compared with RSM and the optimized input welding parameters for the electrode current, hot wire current and wire feed rate exhibited maximum ultimate tensile strength which were also confirmed from response and contour plots.Originality/valueSensitivity analysis was also performed to understand the effect of each individual parameters on the response. Microstructure features were evaluated for the joints and was found that the characteristics are within the desired criteria.
S. Rajakumar, S. Kavitha, and Tushar Sonar
Springer Science and Business Media LLC
Paluchamy Rajalingam, Selvarajan Rajakumar, Visvalingam Balasubramanian, Tushar Sonar, and Subramanian Kavitha
Walter de Gruyter GmbH
Abstract The main objective of this investigation is to enhance the tensile shear fracture load (TSFL) bearing capability and minimize softening in heat affected zone (HAZ) of resistance spot welded DP-1000 steel spot joints for automotive applications. The lap tensile and cross tensile shear fracture load tests (LTSFL and CTSFL) were conducted. The process parameters were optimized using numerical and graphical optimization techniques to maximize the TSFL capability of spot joints. The microstructure of spot joints was studied using optical microscopy and correlated to TSFL and hardness of spot joints. Results showed that DP-1000 steel spot joints made using the welding power of 70 W, welding time of 1.0 s, electrode pressure of 4.25 MPa showed maximum LTSFL of 22 kN and CTSFL of 9.1 kN. The parametric optimization showed 46.66, 45.77, 22.33 and 9.87% increase in LTSFL, CTSFL, nugget zone hardness and HAZ hardness of DP-1000 steel spot joints. The higher TSFL and nugget hardness of spot joints is mainly attributed to the evolution of finer martensitic sandwiching ferrite phases in nugget zone and lower softening of HAZ than other joints. Welding power showed significant influence on TSFL of spot joints followed by welding time and electrode pressure.
S. Kavitha, V. Sugapriya, and Nirmala P. Ratchagar
AIP Publishing
Nimmala Harathi, Kavitha Subramanian, Argha Sarkar, and Rajakumar Selvarajan
World Scientific Pub Co Pte Ltd
This paper presents the performance of three different micro-electro mechanical systems (MEMS)-based surface acoustic wave (SAW) devices for sensing hydrogen gas. All three devices, namely, Device 1, Device 2 and Device 3, were constructed with the same dimensions but with varying geometries. The devices were simulated using COMSOL Multiphysics and various analyses such as deflection, electric potential, frequency shift with respect to the concentration of hydrogen gas, total capacitance of interdigital transducers (IDTs) and sensitivity were performed using finite element modeling. The devices were constructed with a lithium-niobate piezoelectric substrate and a ZnO sensing layer. The performance of MEMS-based SAW devices can be improved by doping with nanomaterials. The devices were tested with hydrogen gas at concentration from 10[Formula: see text]ppm to 100[Formula: see text]ppm. Owing to the mass loading effect, Device 3 exhibited maximum sensitivity and a close approximation of the simulated results with the theoretical results.
P.G. Sam Infant Jones, S. Rajakumar, S. Kavitha, and V. Balasubramanian
Informa UK Limited
N. Muthukumar, K. Srinivasan, S. Rajakumar, S. Kavitha, and V. Balasubramanian
Informa UK Limited
Alex Anandaraj J, S Rajakumar, V Balasubramanian, and S Kavitha
Elsevier BV
Prabhuraj Parasuraman, Rajakumar Selvarajan, Balasubramanian Visvalingam, Rajkumar Ilamurugan, and Kavitha Subramanian
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 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
Springer Singapore
P. Rajalingam, S. Rajakumar, V. Balasubramanian, S. Kavitha and M. M. Selvan
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
Springer Science and Business Media LLC
Nimmala Harathi, S. Kavitha, and Argha Sarkar
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
S. Kavitha, R. Joseph Daniel, and K. Sumangala
Elsevier BV
S. Kavitha, R. Joseph Daniel, and K. Sumangala
Elsevier BV
V.E. Annamalai, S. Kavitha, and Sarah Ann Ramji
Bentham Science Publishers Ltd.
The alloy Ti6Al4V has evolved as a good biomedical material, by virtue of its bio-compatibility. In order to make implants out of this material, it has to be shaped and processed. Shaping this material by conventional manufacturing methods like machining, welding and brazing presents a huge challenge. This challenge has been met by various approaches like additive manufacturing, surface alloying and heat treatment. Additive manufacturing processes are used for shaping; coatings and surface alloying are used for property improvement; heat treatment is used for improving the machinability. The processing method has an impact on the final properties of the product. This review attempts to trace the development of methods and practices for converting Ti6Al4V into a useful material for biomedical applications.
S. Kavitha, R.Joseph Daniel, and K. Sumangala
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.