Department of Mechanical Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

We analyze the utility of edge cracked semicircular disk (ECSD) for rapid assessment of fracture toughness using compressive loading. Continuing our earlier work on ECSD, a theoretical examination here leads to a novel way for synthesizing weight functions using two distinct form factors. The efficacy of ECSD mode-I weight function synthesized using displacement and form factor methods is demonstrated by comparing with finite element results. Theory of elasticity in conjunction with finite element method is utilized to analyze crack opening potency of ECSD under eccentric compression to explore newer configurations of ECSD for fracture testing. © 2013 Elsevier Ltd.

World University root node

Engineering Fracture Mechanics

Synthesis and application of weight function for edge cracked semicircular disk (ECSD)

In general damping is estimated from impulse response obtained by giving small impact when the system is stationary (like a civil structure or a beam), this approach is well documented in many research works. In case of rotor-bearing systems such as a steam turbine, the damping estimated by impact is not identical to the damping observed during operation because of the angular acceleration effects. Since, it is not possible to obtain impact responses from a rotor bearing system operating at high speeds, one has to relay on signals obtained during operation which contain damping information. The present study compares conventional and time-frequency methods for estimating damping in rotor bearing systems from transient characteristics. Advantages of using time-frequency techniques over conventional techniques are focused.

20th International Congress on Sound and Vibration 2013, ICSV 2013

Damping estimation in rotor bearing systems: Comparison of conventional and time-frequency techniques

Proceedings of 40th National Conference on Fluid Mechanics and Fluid Power {\ldots}

Studies on air entrainment in a circular turbulent jet using a pipe

This paper reports the results of an experimental study to determine the principal thermal conductivities (k x, k y, and k z) of an anisotropic composite medium using an inverse heat transfer analysis. The direct problem consists of solving the three dimensional heat conduction equation in an orthotropic composite medium with the finite difference method to generate the required temperature distribution for known thermal conductivities. The measurement technique involves dissipating a known heat flux at the central region of a square sample and allowing it to conductively transfer the heat to an aluminium cold plate sink via a square copper ring. At steady state, temperatures at 28 (19 are used for retrievals due to symmetry) discrete locations are logged and used for parameter estimation. The entire measurement process is conducted in a vacuum environment. The inverse heat conduction problem (IHCP) for retrieving the orthotropic thermal conductivity tensor(parameter estimation) is then solved using a two layer feed forward back propagation artificial neural network (ANN) trained using the Levenberg-Marquardt algorithm (LMA), with temperatures as input and thermal conductivity values k x, k y, and k z as the output. The method is first validated against a stainless steel(SS-304) sample of known thermal properties followed by the determination of the orthotropic conductivities of the honeycomb composite material. © 2013 American Society of Mechanical Engineers.

Journal of Heat Transfer

Simultaneous estimation of principal thermal conductivities of an anisotropic composite medium: An inverse analysis

Edge cracked semicircular disk under compression exhibited form factor constancy over wide range of relative crack lengths. Inspired from this property, edge cracked semicircular ring (ECSR) is analyzed with the aim of enhancing validity range of constant form factor property. Understanding the effects of inner radius and load angle on form factor of ECSR, different combinations of the two are examined towards reaching the aim. Photoelasticity in conjunction with FEM is used to analyze the specimen. A particular combination of inner radius and load angle is found to give constant form factor over an enhanced range.

Indian Conference on Applied Mechanics, Indian Institute of Technology {\ldots}

A novel semicircular compression fracture specimen

This paper proposes an observer-assisted (indirect) adaptive trajectory tracking control scheme for an under-actuated autonomous underwater robotic vehicle. The proposed control algorithm was based on feedback linearization control, using the estimated vehicle (hydrodynamic) parameters and external disturbance parameters (e.g., underwater current, buoyancy variations, etc.). These parameters were estimated online by employing a well-known non-linear observer extended Kalman filter. Using these estimated parameters and estimated disturbance vector, a feedback linearization control system was constructed for an under-actuated underwater vehicle. The effectiveness of the proposed system demonstrated and discusses the robustness using simulation results. The simulation results were compared with those of a control scheme that employed true parameters and without compensation, as well and results show the proposed scheme works well. © 2013 ACM.

ACM International Conference Proceeding Series

Observer - Assisted adaptive tracking control of an underactuated autonomous underwater vehicle

In many underwater missions, it is necessary for the autonomous underwater vehicle (AUV) to be stationed at a particular position and orientation to carry out tasks like inspection, opening/closing of valves, or repair of underwater installations. The ability of an AUV to maintain its position and orientation dynamically is termed as dynamic station keeping. Being a free-floating device, dynamic station keeping is not natural to most of the AUVs. This becomes more complex when the vehicle is underactuated and is not neutrally buoyant. In this paper, the problem of dynamic station keeping of an underactuated flat-fish type AUV is analysed and a new method of station keeping is proposed with an addition of dedicated thrusters. Effect of introduction of additional thrusters on tracking performance has been analysed and a modular configuration (using retractable thrusters) is proposed to reduce its influence on tracking control. The effects of underwater current magnitudes and angle of incidences on the station keeping performance are also analyzed. A comparative analysis on power consumption during station keeping is presented to prove the effectiveness of the proposed modular configuration. © 2012 Elsevier Ltd. All rights reserved.

Ocean Engineering

Power efficient dynamic station keeping control of a flat-fish type autonomous underwater vehicle through design modifications of thruster configuration

Composite materials are broadly recognized and accepted in a variety of engineering applications due to their inherent properties such as higher stiffhess, good corrosion resistance and more importantly assisting weight reduction. Shafts made of composite materials are widely the subject of study as it incurs the advantage of the above said properties. The composite drive shafts which can give an increased natural frequency for the same length as that of the steel shaft is a potential candidate in eliminating two piece steel drive shaft. It is used as transmission shaft in marine pro-pulsion and many other applications where weight reduction is very much appreciable. The vital rotor dynamic characteristics require for any shaft system are the natural frequencies in essentially in bending and torsion modes, the response studies and the torque transmission characteristics. In this work, glass/epoxy and carbon/epoxy shafts are studied for their response behaviour using harmonic analysis. Unbalance response studies is carried out in composite shafts by developing an un-balance in the disc mass which is equal to the eccentric mass times the radius. The shafts are modeled using glass and carbon fibers with epoxy resin as the matrix material. The modeled shafts are studied with discs mounted on them. Glass, carbon and steel discs are used for the response study. The shaft and disc combinations are varied and the results are compared. The work is carried out using ANSYS. Apart from glass and carbon shafts, hybrid shafts which include both the glass and carbon fibers in a single shaft model are also used for the study. As the hybrid shafts include the advantage of both fiber materials, it is a more viable model in order to achieve characteristics to suit respective applications. The response behavior of hybrid shafts with different discs is analyzed and compared with the glass/epoxy and carbon/epoxy shafts.

Unbalance response behavior of glass/epoxy, carbon/epoxy and hybrid composite shafts

This work reports the results of a study envisaged to benchmark a novel technique for simultaneously estimating the principal thermal conductivities (kx, ky and kz) of an anisotropic composite medium. The technique essentially involves solving a formulated Inverse Heat Conduction Problem (IHCP) using measured temperature data as input to simultaneously estimate the constant thermal conductivities along the three directions of an anisotropic composite. The IHCP is solved using a hybrid optimization algorithm where the forward simulations are driven by a carefully chosen ANN and the optimization part is accomplished by employing GA. Before accomplishing estimation with actual \measurements"synthetically generated \surrogate temperatures are used to ascertain the adequacy and robustness of the methodology. An indigenously designed anisotropic material whose effective thermal conductivities in the principal directions are determined using a full scale computational heat transfer analysis is used as a benchmark for validating the technique.

44th AIAA Thermophysics Conference

Benchmarking a novel technique for estimating principal thermal conductivities of an anisotropic composite medium

This paper presents an indirect adaptive control method for an autonomous underwater vehicle-manipulator system (UVMS) based on an <a href="https://www.sciencedirect.com/topics/engineering/extended-kalman-filter">extended Kalman filter</a> (EKF). This method overcomes the disadvantages of existing disturbance observers and direct adaptive control schemes, which are based on <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/linear-systems">linear system</a> techniques and regressor-based techniques. The proposed control scheme can be applied to UVMSs for various purposes such as payload compensation, interaction effects compensation, underwater current or <a href="https://www.sciencedirect.com/topics/engineering/external-disturbance">external disturbance</a> compensation, reaction compensation, and independent system control. The performance of the proposed controller was demonstrated numerically by payload compensation, where it compensated for the reaction effects experienced during a manipulation task, and disturbance (underwater current) compensation in a UVMS with a six degrees of freedom (DOF) underwater vehicle and a 3-DOF underwater manipulator.