Department of Mechanical Engineering

&ldquo;IIT Jodhpur is committed to impart quality education to facilitate the creation of qualified, competent and responsible human resources to meet the emerging technological challenges of the world. It is working towards creating an equitable learning platform that is positive, accessible and effective in the face of the modern societal and scientific advancements.

Flexibility in curriculum, in all its academic programs, encompassing elements of teaching, research, creativity, innovation and entrepreneurship is the most unique feature of IIT Jodhpur. The Department of Science and Technology (DST), under the National Mission on Cyber Physical Systems, has identified IIT Jodhpur as a Technology &amp; Innovation Hub in the area of Augmented Reality and Virtual Reality. The institute has also been nominated as the coordinator for the Jodhpur City and Knowledge Cluster by the Office of Principal Scientific Adviser, Government of India.

The sprawling 852-acre IIT Jodhpur campus is a majestic tribute to the deep-rooted diverse cultural heritage of the region. The campus is an architectural masterpiece, which is slated to become an international exemplar of sustainability with net-zero energy, and advanced water and waste management strategies.&rdquo;

IIT Jodhpur

The assessment of nonlinear phenomena with a focus on investigating the bifurcations and chaotic behaviour of an elastically induced flexible rotor-bearing system subjected to a harmonic ground motion has been studied. The higher-order Euler–Bernoulli deformation theorem has been adopted that governs the nonlinear dynamic characteristics of the rotating system. Nonlinear vibration analysis has been carried out to determine the critical speeds, i.e., Campbell diagram followed by demonstrating the inherent nonlinear signatures through the illustration of time history, Fourier spectrum and Poincare’s map upon varying the system design variables. The perturbation technique has been used to obtain the approximate nonlinear solutions from a set of polynomial algebraic equations under steady-state condition in various resonance cases. Further, stability analysis along with successive bifurcations of the solutions has been investigated. The present nonlinear model formulated based on Euler theory has been found to be capable enough to predict the correct value of critical speeds and dynamic responses in comparison with that of model developed based on Timoshenko theory. The present outcomes can offer immense practical importance for any application of the flexible rotor-bearing system when it performs high-speed operation. © 2017, Springer Science+Business Media B.V.

World University root node

Nonlinear Dynamics

Evaluation of nonlinear responses and bifurcation of a rotor-bearing system mounted on moving platform

The present research work deals with the results of influence of different heat treatment conditions on the microstructure stability and mechanical properties of high-chromium X10CrMoVNNB9-1(P91) cast and forged (C&amp;F) P91 steel. The C&amp;F P91 steel was subjected to various tempering condition in the temperature range of 350–760 °C and tempering time of 2 h, after the normalizing at 1040 °C for 40 min. The steel was also subjected to furnace cooled and water quenched heat treatment. Tempering at 650 and 760 °C produced the fully tempered lath martensitic structure with M23C6, M7C3, M3C and MX precipitates along the prior austenite grain boundaries, lath boundaries and matrix region. Tempering at 350 and 1000 °C produced the partially tempered columnar laths and untempered columnar laths martensite, respectively. The tempering time was also varied from 2 to 8 h for fixed tempering temperature of 760 °C. The optimum microstructure evolution was obtained for 6 h of tempering at 760 °C that led to improved mechanical properties. © 2017 The Indian Institute of Metals - IIM

Transactions of the Indian Institute of Metals

Characterization of Cast and Forged (C&amp;F) Gr. 91 Steel in Different Heat Treatment Condition

In the present investigation, varying electrode conditions (dried and contaminated) have been employed during welding of P92 steel to study the effect of diffusible hydrogen level on hydrogen-assisted cracking (HAC). Shielded metal arc welding process was employed to deposit the metal on a P92 steel plate. To evaluate HAC, the Granjon implant test with varying diffusible hydrogen content in the deposited metal was utilized. The diffusible hydrogen level was measured in the deposited metal by using the mercury method. Lower critical stress (LCS), embrittlement index (EI) and normalized critical stress ratio were evaluated from the Granjon implant test. The fracture surface morphology of fractured implant specimens has been studied by using a field emission secondary electron microscope. The P92 steel plate welded by the contaminated electrode with a high level of diffusible hydrogen was found to be more susceptible to HAC. As diffusible hydrogen content increased in the deposited metal, the LCS value and EI were observed to be decreased. © 2017 Hydrogen Energy Publications LLC

International Journal of Hydrogen Energy

Effect of diffusible hydrogen content on embrittlement of P92 steel

Cr-Mo creep strength enhanced ferritic (CSEF) steels are mainly used in nuclear reactors and ultra-supercritical (USC) power plants for superheater tubes and header. The present research deals with the analysis of fracture surface of the tensile and impact tested specimen of cast and forged (C&F) modified 9Cr-1Mo (P91) steels, which are subjected to different heat treatment regimes. The heat treatment temperatures were 350 °C, 650 °C, 760 °C and 1000 °C, respectively. The heat treatment was carried out a particular temperature for 2 h duration. The fracture surface of tensile and impact tested specimen were also studied for a varying time duration from 2 h to 8 h for a fixed tempering temperature of 760 °C. The heat treatment effect on tensile properties, toughness, Vickers hardness and particle size was also studied. Heat treatment has a noticeable effect on mechanical properties of C&F Grade 91 (X10CrMoVNNB9-1) steel. Fracture morphology is strongly affected by the microstructure and presence of secondary phase particles. The fracture surface was analyzed by using the field-emission scanning electron microscope (FE-SEM). The fractured tensile sample mainly indicates the presence of transgranular ductile dimples and transgranular cleavage facets for heat treatment temperatures of 350 °C, 1000 °C and 1040 °C. The percentage of cleavage facets on the tensile fracture surface was found to decrease for sample heat treated at 760 °C. Less amount of ductile dimples was noticed on the fracture surface for the samples heat treated at 650 °C and 760 °C (furnace-cooled). The so-called ‘splitting’ fracture was noticed for the sample heated at 760 °C. The ‘splitting’ fracture becomes more pronounced with the increase in tempering duration from 2 h to 8 h. The sample heat treated for 1000 °C, mainly indicates the cleavage facets on the fracture surface. The fracture mode of impact tested specimen is more complex and shows both ductile dimple tearing and quasi-cleavage facets for heat treatment temperature of 650 °C, 760 °C and as-received condition. The impact failure zone of sample heat treated at 350 °C and 1000 °C indicates the presence of so-called ‘river pattern’ on the fracture surface. © 2016 Elsevier Inc.

Engineering Failure Analysis

Study of the fracture surface morphology of impact and tensile tested cast and forged (C&amp;F) Grade 91 steel at room temperature for different heat treatment regimes

The effect of heat treatment condition and diffusible hydrogen level on microstructure and mechanical properties of multi-pass shielded metal arc welded (SMAW) P91 steel butt joints of 18 mm thickness has been studied. Field-emission scanning electron microscope (FESEM), Mercury diffusible hydrogen measurement, Charpy test, room-temperature tensile testing, hardness measurement and energy dispersive X-ray spectroscopy (EDS) were performed to characterize the multi-pass SMAW joints in as-welded, post-weld heat treatment (PWHT) and normalizing/tempering (N&T) state. The P91 steel butt joints with low level of diffusible hydrogen exhibited higher tensile strength and toughness. Both PWHT and N&T treatment provided similar mechanical properties but a significant microstructure variation was noticed for different zones of P91 welds. N&T treatment produced the homogenize microstructure along the P91 weldments both in terms of microstructure and micro-hardness. © 2017 The Society of Manufacturing Engineers

Journal of Manufacturing Processes

Microstructure and mechanical property relationship for different heat treatment and hydrogen level in multi-pass welded P91 steel joint

This paper addresses a 2PRP-2PPR planar parallel manipulator and, its implementation in the design and development of a new lower limb rehabilitation robot (LLRR). The difficulty and limitation of the existing mechanisms has been analysed and a new mechanism is proposed. Some limitation of the proposed manipulator, namely limited effective workspace, has also been overcome by gear arrangement to make it suitable for the application. The proposed mechanism is able to perform like a serial LLRR with the same clinical space with advantages of parallel manipulators like better accuracy, speed and stiffness. The proposed manipulator consist of a vertical planar parallel manipulator (2PRP-2PPR)which is driver mechanism and a lower limb orthosis which is driven and actuator-free mechanism has a RRR serial planar configuration, is designed to treat the patient in sitting/lying postures. Validation of the functional design and working of the proposed system has been done analytically by using the clinical gait pattern data. © Springer International Publishing Switzerland 2017.

Mechanisms and Machine Science

A 2PRP-2PPR planar parallel manipulator for the purpose of lower limb rehabilitation

The purpose of this paper is to present the model of a Humanoid robot inspired by Poppy, modified for heavier load capacity and the balancing of humanoid in multiple work environments. The design has been modified in order to use MX-64 servos with more torque capacity than MX-28 servos which were used in original design. We have also redesigned the ankle joint and feet to make it a more accurate human like model. We are using an integrated approach using zero moment point (ZMP) with force sensing resistor (FSR) and center of mass (CoM) to find balance margins of the robot. Balancing and forward bending experiments on robot are conducted by providing some basic motion to the robot and ensuring that the robot is balanced and moving within safe margins using this approach. © 2016 IEEE.

International Conference on Robotics and Automation for Humanitarian Applications, RAHA 2016 - Conference Proceedings

Design and development of a humanoid with articulated torso

At the cross section of the fields of Uneven Terrain Navigation and Multi Agent Systems (MAS), in this work, a Detachable Compliant Modular Robot (DCMR) which can perform concurrent scene exploration by detaching into numerous parts, while preserving its ability to climb stairs is proposed and built. A spring is designed and used in the modular robot taking the worst-case-scenario of stairs encountered in an urban setting. In addition to the actuators at the wheels, an additional set of actuators per module are introduced to enable the detachment and re-attachment. The design additions and their trade-offs are discussed. Potential applications are presented with special focus on improving coverage of a map with obstacles/slabs large enough to merit exploration by climbing them. The problem of turning in crammed spaces is solved using the ability to detach of DCMR. The detaching & re-attaching capability, and stair climbing of the composite modular robot are demonstrated through experimentation using the prototype. © 2017 IEEE.

Proceedings - IEEE International Conference on Robotics and Automation

Detachable modular robot capable of cooperative climbing and multi agent exploration

Micro-end milling is used for manufacturing of complex miniaturized components precisely in wide range of materials. It is important to predict cutting forces accurately as it plays vital role in controlling tool and workpiece deflections as well as tool wear and breakage. The present study attempts to incorporate process characteristics such as edge radius of cutting tool, effective rake and clearance angles, minimum chip thickness, and elastic recovery of work material collectively while predicting cutting forces using mechanistic model. To incorporate these process characteristics effectively, it is proposed to divide cutting zone into two regions: shearing- and ploughing-dominant regions. The methodology estimates cutting forces in each partitioned zone separately and then combines the same to obtain total cutting force at a given cutter rotation angle. The results of proposed model are validated by performing machining experiments over a wide range of cutting conditions. The paper also highlights the importance of incorporating elastic recovery of work material and effective rake and clearance angle while predicting cutting forces. It has been observed that the proposed methodology predicts the magnitude and profile of cutting forces accurately for micro-end milling operation. © 2017 Taylor & Francis Group, LLC.

Machining Science and Technology

On modeling of cutting forces in micro-end milling operation

Variation in dynamic contact resistance with the change in welding process parameters such as weld current, weld time and electrode force were taken into account for establishing the range of adequate nugget formation parameters. Influence of the welding process parameters on the shear – tensile strength, nugget diameter and the observed failure mode was analysed. The adequate resistance spot welding process parameters for galvannealed high strength interstitial free steel sheets of 1.6 mm thickness were estimated as 8 kA weld current, 250 ms weld time and 3.5 kN electrode force. Increase in the mean dynamic contact resistance led to a significant reduction in nugget diameter. A critical nugget diameter distinguishing between the IF and PF mode was experimentally determined by failure mode analysis. Different numerical models for estimation of critical nugget diameter were evaluated. © 2017 Elsevier B.V.