Department of Mechanical Engineering

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IIT Jodhpur

This paper proposes a planar hybrid manipulator system integrated with a passive serial orthosis for a foot-plate based sitting-type lower limb rehabilitation robot. The proposed robotic system has a modularity which can be easily upgraded to a standing-type body weight support (BWS) mechanism. The detailed design and development of the robot are discussed in this paper along with its kinematic and dynamic analyses. The rehabilitation strategy is described for the field of application. The effectiveness and performance of the proposed mechanism are demonstrated with a clinical gait pattern using a proportional-integral-derivative (PID) control scheme on an in-house fabricated real-time prototype. The prototype experiments are conducted in view of validating the prototype for the therapeutic and gait training motions. © 2017 Elsevier Ltd

World University root node

Computers and Electrical Engineering

Development and control of a new sitting-type lower limb rehabilitation robot

Numerical modeling of fuel injection in internal combustion engines in a Lagrangian framework requires the use of a spray-wall interaction sub-model to correctly assess the effects associated with spray impingement. The spray impingement dynamics may influence the air-fuel mixing and result in increased hydrocarbon and particulate matter emissions. One component of a spray-wall interaction model is the splashed mass fraction, i.e. the amount of mass that is ejected upon impingement. Many existing models are based on relatively large droplets (mm size), while diesel and gasoline sprays are expected to be of micron size before splashing under high pressure conditions. It is challenging to experimentally distinguish pre- from post-impinged spray droplets, leading to difficulty in model validation. In this study one commonly used splashed mass model, proposed by O'Rourke and Amsden, was studied through Direct Numerical Simulations (DNS) using an in-house 3D multiphase flow solver, which has been validated in previous studies. To test the splashed mass model in scenarios relevant to fuel impingement, input was generated from Lagrangian-Eulerian (LE) diesel injection simulations. A representative combination of droplet diameter and velocity before impact was selected from the LE output. The representative droplet was then used to initialize the DNS calculations, allowing the splashed mass model to be tested for micron-sized droplets. The splashed mass ratio was calculated from the DNS output and was compared to the model of O'Rourke and Amsden. This new LE/DNS framework allows Lagrangian sub-models to be tested in a way that is difficult to examine experimentally and provides unique feedback that will be used to enhance the accuracy of LE spray simulations. © 2018 SAE International; Argonne National Laboratory.

SAE Technical Papers

Using a DNS Framework to Test a Splashed Mass Sub-Model for Lagrangian Spray Simulations

Prediction of adverse drug reactions is an important problem in drug discovery endeavors which can be addressed with data-driven strategies. SIDER is one of the most reliable and frequently used datasets for identification of key features as well as building machine learning models for side effects prediction. The inherently unbalanced nature of this data presents with a difficult multi-label multi-class problem towards prediction of drug side effects. We highlight the intrinsic issue with SIDER data and methodological flaws in relying on performance measures such as AUC while attempting to predict side effects. We argue for the use of metrics that are robust to class imbalance for evaluation of classifiers. Importantly, we present a `hierarchical anatomical classification schema' which aggregates side effects into organs, sub-systems, and systems. With the help of a weighted performance measure, using 5-fold cross-validation we show that this strategy facilitates biologically meaningful side effects prediction at different levels of anatomical hierarchy. By implementing various machine learning classifiers we show that Random Forest model yields best classification accuracy at each level of coarse-graining. The manually curated, hierarchical schema for side effects can also serve as the basis of future studies towards prediction of adverse reactions and identification of key features linked to specific organ systems. Our study provides a strategy for hierarchical classification of side effects rooted in the anatomy and can pave the way for calibrated expert systems for multi-level prediction of side effects.

Fulltext

PLOS ONE

A hierarchical anatomical classification schema for prediction of phenotypic side effects

This paper presents a new perspective into the decomposition of the Generalized Inertia Matrix (GIM) of multibody systems with open kinematic architecture, serial or tree-type. Links and kinematic pairs are the two constituting elements of multibody systems. In this work, we propose to decompose a multi-branch multibody system into several kinematic modules. Each module is a set of serially connected links like a serial-chain system. Such a description allows one to obtain a block decomposition U¯ D¯ U¯ T of the GIM where U¯ and D¯ are the block upper-triangular and diagonal matrices, respectively. The results provide a recursive inverse of the GIM on module-level. Many new perspectives leading to macroscopic purview of the complex multibody systems are provided. Empowered with the proposed decomposition, an inter- and intra-modular efficient and numerically stable recursive dynamics algorithm for forward dynamics and simulation was possible. While recursive expressions are derived for a four degree-of-freedom gripper, numerical results are shown for a spatial biped. © 2017, Springer Science+Business Media B.V.

Multibody System Dynamics

A new perspective towards decomposition of the generalized inertia matrix of multibody systems

In this article, we report some experimental results on the behaviour of the flame of a candle kept at the bottom of a glass tube, which is open at the top and closed at the bottom. Thus, the supply of oxygen for the continuous burning of the flame is possible only from the top open end of the tube. We find that the candle burns steadily below a critical tube height. Above this height, the flame oscillates in size, and a further increase in tube height leads to the flame extinguishing quickly. © 2018, Indian Academy of Sciences.

Resonance

Burning, Fluttering, and Extinguishing of a Candle Flame in a Tube

The concentrated solar power plant technology has been proven to be a latest source for generation of renewable energy. Its performance depends on efficiency of the parabolic trough receiver tube or heat collecting element (HTC). In this paper, experimental study on fabrication of glass metal joint has been elaborated for parabolic trough receiver tube. Borosilicate glass tube was joined with austenitic stainless steel (SS304) metal ring using compression glass-metal type assembly with the help of induction heating and using 40SiO 2 -54B 2 O 3 -4Na 2 O-2Al 2 O 3 material as the glass sealant. The process parameters for joining were selected on the basis of wettablity, pre-oxidation and microstructure studies. The generated residual stresses in glass tube after fabrication process was measured experimentally with the help of photo elastic technique using polariscope 'PS-100-BS'. From the experimental results, it was observed that, the intensity of residual tensile stress in glass tube increases as thickness of metal ring increases. The cracking of glass just 1mm above the interface was also observed corresponding to maximum metal thickness ring. © 2018 Elsevier Ltd. All rights reserved.

Materials Today: Proceedings

Failure Study of Compression Glass-Metal Joint for Parabolic Trough Receiver Tube application

Pipeline welding is an integral part of oil and gas exploration industries. Often the weld failures are observed due to lack of weld quality, improper heat treatment and poor workmanship. Further, the use of new materials in pipeline industry puts focus on a better understanding of requirements for welding and reducing the failures in future. This necessitates the need for development and design of suitable welding fluxes for joining of these materials. In this paper an attempt is made to analyse the effect of commercial submerged arc welding flux and laboratory prepared agglomerated submerged arc welding fluxes (of basic, rutile basic and rutile acidic type) on the weldability, microstructural evolution as well as the structural integrity issues in API X70 line pipe steel welds. The mechanical and microstructural behaviour of weld joints was observed for submerged arc welding fluxes. The maximum tensile strength of 613 N/mm2 was observed for weld joint prepared using commercial flux (C.F). While in case of agglomerated fluxes the maximum value of tensile strength observed was 561 N/mm2 for F15B basic flux. Impact toughness for all the weld joints was evaluated both at room temperature and at −65 °C. For the weld as well as the heat-affected zone, the maximum impact toughness (160 J and 436 J) was observed for basic flux F5B at room temperature while at −65 °C (16 J and 30 J) impact toughness was obtained which was similar to that obtained with commercial flux. Microhardness of commercial weld joint (232 HV) is maximum as compared to the other weld joints. Maximum microhardness of 222 HV was observed for weld joint fabricated with flux F15B. Flux F15B shows a maximum value of microhardness (218 HV) for the heat-affected zone. Weld joints fabricated by using F3RA and F19RA fluxes exhibit high susceptibility to hydrogen induced cracking as compared to the remaining weld joints. The crack sensitivity ratio (CSR %) is high for weld specimen F3RA (54.64%) and F19RA (50.26%) while weld specimen fabricated using (F5B and C.F) fluxes show minimum crack sensitivity ratio (27.54% &amp; 30.97%) respectively. The high susceptibility towards hydrogen induced cracking may be attributed to the very low value of carbon equivalent as compared to the remaining weld joints. © 2018 Elsevier Ltd

International Journal of Pressure Vessels and Piping

Mechanical properties and hydrogen induced cracking behaviour of API X70 SAW weldments

The decrease of SiO2/B2O3 ratio in the glass sealant composition from 6.23 to 0.74, leads to reduction in its glass transition temperature Tg (590 °C–507 °C) and its crystallization temperature Tc (820 °C to 710 °C). The percentage change in weight loss during heating of glass sealant powder decreased from 78% to 63% with decrease in SiO2/B2O3 ratio. The density of glass sealant increased from 1.47 to 2.11 g/cm3 with decrease of SiO2/B2O3 ratio in the glass sealant composition. The glass sealant composition with lowest SiO2/B2O3 ratio of 0.74 and having a chemical composition (40SiO2-54B2O3-2Al2O3-4Na2O) was considered to be the optimum sealant where the maximum adhesion strength of 2.5 N/mm2 was obtained along with lowest value of contact angle 17° and highest wettability (spreading area value of 585 mm2) of the glass sealant. The optimum value of glass transition temperature (Tg) 507 °C and crystallization temperature (Tc) 710 °C was obtained corresponding to glass sealant composition with the lowest SiO2/B2O3 ratio. © 2018 Elsevier B.V.

Journal of Materials Processing Technology

Effect of SiO2/B2O3 ratio on the thermophysical and wetting properties of borosilicate glass sealant for glass-metal joint

Zirconium carbonitride (ZrC-ZrN) absorber layer has been optimized for the maximum absorptivity alpha similar to 0.9 in ZrOx/ZrC-ZrN/Zr reflector-absorber tandem structures on stainless steel (SS) and aluminum (Al) substrates, using reactive DC/RF magnetron sputtering process and varying reactive nitrogen during the deposition. The mechanical properties such as hardness and Young's modulus values increase from similar to 19.63 to similar to 38.53 GPa and similar to 36.39 to similar to 58.67 GPa, respectively, with increasing nitrogen flow rate during ZrC-ZrN absorber layer deposition on SS substrate. These values also increase with increasing load up to a critical limit and saturates thereafter with further increase in load values. The films with moderate hardness and Young's modulus exhibit enhanced solar thermal performance (alpha similar to 0.9) against films with lower and higher values of these mechanical properties, suggesting optimal nitrogen concentration for desired solar thermal performance.

Department of Mathematics

Department of Physics

Effect of Growth Condition on Mechanical Properties of Zirconium Carbonitride Absorber-Based Spectrally Selective Coatings

Pull-in analysis of an electrostatically actuated nonuniform micro-resonator under large elastic deflection has been investigated with a focus on qualitative analysis to understand the essence of nonuniform cross-section on the determination of pull-in voltage. Here, a microcantilever beam with nonuniform cross-section has been adopted to develop a mathematical model considering the important features such as structural nonlinearities, nonlinear electrostatic distribution, and linear viscous effect. The individual effect of each design variables on the diagnosis of the critical voltage and corresponding critical deflection due to pull-in has been graphically depicted. The results in the static condition have been verified with the findings obtained via COMSOL multi-physics software. Present result indicates that a nonuniform microbeam configuration strengthens the structural stability by switching the pull-in voltage up to a higher value. Similarly, stable pull-in deflection within the restriction of pull-in instability has been also augmented. In addition, it has been shown that the nonuniformity within the beam structure is highly sensitive to the nonlinear effects. Hence, outputs provide a useful insight of pull-in behavior and enable an understanding of safe and smooth operating range of microelectromechanical system devices. © IMechE 2017.