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

In rolling contact bearings, contact occurs between the rolling surfaces over a small region. Hence, high contact stresses are induced in the region even under a small load. These stresses are cyclic in nature. Over a long period of time, the surface gets fatigued and surface fatigue wear ensues. The experimental investigation carried out in the laboratory earlier consumed a long time. Therefore, a numerical approach is resorted to in this paper. To study this aspect, the stress field in the contact surface region is analyzed under elastohydrodynamic lubrication with line contact considering the friction effect. The bearing steel microstructure is considered as a mixture of martensite and retained austenite having entirely different mechanical properties and yield behavior. Using finite element analysis, the stress field has been evaluated taking into account two volumetric fractions (8% and 20%) of retained austenite in heat treated AISI 52100 bearing steel. A simplified approach neglecting the effect of strain induced transformation of austenite is attempted in the first phase. The depth at which the failure is expected to occur is compared with the experimental values of earlier investigation. The predicted values are marginally higher than the experimental values. © 2015 Elsevier B.V.

World University root node

Wear

Numerical evaluation of subsurface stress field under elastohydrodynamic line contact for AISI 52100 bearing steel with retained austenite

A computational framework based on a combined 3D-CFD/FE along with a second order rotor dynamics model is employed to assess a six-tooth straight through rotating labyrinth seal for a varying flow and operating conditions. Three-dimensional Reynolds Averaged Navier-Stokes compressible equations are solved to obtain the circumferential pressure distributions and are integrated further to calculate the seal fluid forces. Subsequently, the extracted rotor dynamic coefficients are compared to the one without considering centrifugal growth. All the six rotor dynamic coefficients shows distinct characteristics when the centrifugal growth is accounted for. The centrifugal growth has a substantial reduction on cross-coupled stiffness and direct damping and the influence increases with speed. The stability aspects of the seal are examined in terms of whirl frequency ratio and effective damping coefficient, presuming synchronous whirl. The results emphasis the consideration of the seal centrifugal growth effects, while conducting rotor dynamic stability analysis for a typical rotor system.

22nd International Congress on Sound and Vibration, ICSV 2015

Influence of centrifugal growth on the rotor dynamic stability of a rotating labyrinth seal

This paper addresses the working principal of a sitting/lying type passive lower limb rehabilitation robot (LLRR) where patients legs are connected with a passive serial manipulator(orthoses) which consists of three rotary joints serially connected in a plane (RRR), with an active feedback, driven by a three degrees of freedom (DOF) parallel manipulator looks like a symbol The Lambda. The kinematics of the proposed rehabilitation robot has been presented and discussed. Performance analysis of the proposed robot for basic therapeutic exercises has been analyzed on a virtual prototype with the help of multibody dynamic package (namely MSC ADAMS™) and discussed. © 2015, Indian Institute of Technology, IIT. All rights reserved.

2nd International and 17th National Conference on Machines and Mechanisms, iNaCoMM 2015

Kinematic analysis of a passive sitting/lying type lower limb rehabilitation robot

We study the stability of thin walled circular cylindrical shells subject to radial pressure loading. Towards this end, we first develop the equations of motion of these shells with predominant radial deflections. We identify additional terms in the shell equations of motion which have mostly been neglected in existing studies and ascertain their importance in predicting the correct static buckling pressure. For finite cylinders, incorporation of these terms results in the best prediction of the static buckling pressure. Furthermore, we also find that the assumed relationships between the in-plane displacements of a generic point and the in-plane displacements of the mid-surface, which change from one shell theory to the other, play a critical role in determining the correct onset of the buckling instability under radial loading. In particular, the Donnell shell theory which is very popular for the study of dynamic problems related to cylindrical shells does not predict the correct buckling pressure. We find that the Fl{\"{u}}gge-Lur{\'{e}}-Byrne theory is best suited for this purpose. Accordingly, the shell equations with the additional terms and the in-plane displacements related as per the Fl{\"{u}}gge-Lur{\'{e}}-Byrne shell theory have been used for the study of parametric instability of a cylinder subject to a uniform radially fluctuating pressure. Stability charts with respect to different combinations of the forcing parameters viz. the static component of the pressure, the amplitude and frequency of the fluctuating component of the pressure have been presented which can serve as design guideline for shells subject to fluctuating radial loads.

International Journal of Mechanical Sciences

Instabilities of thin circular cylindrical shells under radial loading

The combustion characteristics and emissions in IC engines are influenced by the fuel injection rate. The study of fuel injection rate profile thus becomes essential to improve engine performance. In the present study, the injection rate of GDI injectors was measured in terms of the instantaneous mass flow rate of fuel. A setup was fabricated to obtain the injection rate based on Bosch tube method. Multi-hole GDI injectors of two different manufacturers were used in this study and their performances were measured up to 175 bar of injection pressure. The injector energizing current, wave pressure and rail pressure data were acquired at the rate of 500 kHz on a common time scale. The injected mass value per pulse, obtained by integrating the discharge rate profile was compared with the average values of mass injected measured using a mass balance for both the injectors and their performance were compared. The hydraulic delay measured during injector closing was found to be more than that during injector opening for both the injectors. Injection rate values for any given energizing time was found to be higher for one of the injectors by both the rate profile method and the mass balance averaging method. © 2015 International Conference on Liquid Atomization and Spray Systems. All rights reserved.

ICLASS 2015 - 13th International Conference on Liquid Atomization and Spray Systems

Fuel injection rate measurement of gasoline direct injection (GDI) injectors

The paper investigates the control of a three prismatic-prismatic-revolute (3PPR) U-base planar parallel manipulator in the presence of parameter uncertainties and unknown disturbances. The 3PPR U-base planar parallel manipulator is a motion platform with singularity free workspace (bounded orientation angle θz ≤ ±90°) and has manipulator legs located on the plane in association with a moving platform. Each leg has a prismatic-prismatic-revolute joint configuration in which one prismatic joint is active in each leg. To control the end-effector's mobility of the 3PPR U-base motion platform a proportional-integral-derivative (PID)-like fuzzy logic control scheme is introduced. To demonstrate the effectiveness of the proposed controller, experiments (on a in-house fabricated prototype of the proposed manipulator) with a desired characteristic trajectory are performed and its control performance is compared with an existing conventional PID controller. The results confirmed that the proposed controller has the capability to track the desired task space trajectory and gives a better robust control performance. © 2015, Indian Institute of Technology, IIT. All rights reserved.

PID-like fuzzy logic control scheme for control of a planar parallel (3PPR U-base) manipulator

Gasketed flange joint is a vital component in pressure vessels and piping systems. Flange joint is usually subjected to bending load due to expansion, wind load, self-weight, etc. Most of the flange design methods use equivalent pressure to include the effect of external bending loads. It becomes complex when the joint is subjected to bending load at elevated temperatures, due to the nonlinear behavior of gasket material. In the present work, performance of the flange joint has been studied under external bending load at elevated temperatures. A 3D finite element model is developed, considering the nonlinearities in the joint due to gasket material and contact between its members along with their temperature dependent material properties. The performance of the joint under different bolt preloads, internal fluid pressures and temperatures is studied. Flange joint with two gaskets (twin gasketed joint) placed beside each other radially, is also analyzed under external bending moment. The maximum allowable bending moments at different internal temperatures, for single and twin gasketed joints with spiral wound gasket are arrived. Copyright © 2015 by ASME.

American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP

Finite element analysis of flange joint with single and twin gaskets under external bending load

Rotor faults such as misalignment, shaft crack, rotor rub, bearing fault etc. lead to high vibration and are major cause of machinery shut down. Misalignment in rotating machinery shafts develops reaction forces and moments at the coupling. Conventionally, misalignment diagnosis is carried through vibration measurements. Especially, the existence of strong 2x component is widely accepted. However, there are other rotor-bearing faults which lead to significant 2x vibrations. Hence distinguishing misalignment is a challenging task using vibration signals alone. In view of these limitations by employing vibrations signals, present study focuses on torque measurements for misalignment diagnosis. Experimental results using torque sensor for different cases of misalignment at different frequency of operation are reported. Fourier and wavelet transforms are used to detect the misalignment fault. The variation of the fault characteristics with respect to time are reported for sampled signals using wavelet transforms. The study shows the possibilities of using torque measurements as useful and additional technique for the detection and monitoring of coupling misalignment. © 2014 Elsevier Ltd. All rights reserved.

Measurement: Journal of the International Measurement Confederation

Detection and monitoring of coupling misalignment in rotors using torque measurements

Mechanical Engineering Graduate Research Symposium (MEGRES 2015)

Steady state wall heat flux distribution for impinging laminar methane-air flame jet

This paper addresses the inverse dynamics of three degrees of freedom (DOF) U-shaped planar parallel manipulator having three legs consisting of prismatic-prismatic-revolute (PPR) joint arrangement in which each leg has one active prismatic joint. This paper also proposes a proportional-derivative (PD) like adaptive sliding mode control combined with a disturbance observer for the motion control of the proposed manipulator. Using this control scheme, the controlled robotic manipulator is transformed into decoupled dynamics, and thus the motion performance is very convenient to quantify. Based on Lyapunov like argument the global asymptotic stability of the proposed closed loop system is proved. Real time experiments performed on the in-house fabricated prototype of the proposed manipulator are provided to substantiate the effectiveness and the improved performance of the proposed controller. The proposed controller performances are also compared with traditional controllers such as proportional integral derivative (PID) controller, sliding mode controller (SMC) and computed torque controller (CTC) © 2015 Elsevier Ltd.