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A comprehensive investigation on nonlinear vibration and bending characteristics of bio-inspired helicoidal laminated composite structures

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Applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 81-100页

作者： S.SAURABH R.KIRAN D.SINGH R.VAISH V.S.CHAUHAN School of Mechanical and Materials Engineering Indian Institute of Technology Mandi

Bio-inspired helicoidal composite laminates, inspired by the intricate helical structures found in nature, present a promising frontier for enhancing the mechanical properties of structural designs. Hence, this study provides a comprehensive investigation into the nonlinear free vibration and nonlinear bending behavior of bio-inspired composite plates. The inverse hyperbolic shear deformation theory(IHSDT) of plates is employed to characterize the displacement field, with the incorporation of Green-Lagrange nonlinearity. The problem is modeled using the C0finite element method(FEM), and an in-house code is developed in the MATLAB environment to solve it numerically. Various helicoidal layup configurations including helicoidal recursive(HR), helicoidal exponential(HE), helicoidal semi-circular(HS), linear helicoidal(LH), and Fibonacci helicoidal(FH)with different layup sequences and quasi-isotropic configurations are studied. The model is validated, and parametric studies are conducted. These studies investigate the effects of layup configurations, side-to-thickness ratio, modulus ratios, boundary conditions, and loading conditions at different load amplitudes on the nonlinear vibration and nonlinear bending behaviors of bio-inspired composite plates. The results show that the laminate sequence exerts a substantial impact on both nonlinear natural frequencies and nonlinear bending behaviors. Moreover, this influence varies across different side-to-thickness ratios and boundary conditions of the bio-inspired composite plate.

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Solution and Thermodynamic Studies on Binary and Ternary Complexes of Lanthanides

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Journal of Rare Earths 2005年第4期23卷 389-396页

作者： Rajeev Kumar Udai P Singh Department of Chemistry Indian Institute of Technology Roorkee Roorkee-247667 IndiaDepartment of Chemistry Indian Institute of Technology Roorkee Roorkee-247667 India

The interactions of La（ Ⅲ ）, Pr（ Ⅲ ）, Nd（ Ⅲ ）, Sm（ Ⅲ ）, Eu（Ⅲ）, Gd（ Ⅲ ）, Dy（ Ⅲ ）, and Yb（ Ⅲ ） with cytosine, 5-bromocytosine, 5-azacytosine and 5-flurocytosine as primary ligands （L） and guanine （A） as secondary ligand for both binary （ 1 ： 1 ） as well as ternary （ 1 ： 1 ： 1 ） systems were investigated by potentiometric equilibrium measurements at 25, 35 and 45 ℃ in aqueous solution （ionic strength, μ = 0.1 mol·dm^-3 NaNO3）. The stability constants of the binary （ 1 ： 1 ） and ternary （ 1 ： 1 ： 1 ） metal-ligand complexes follow the following order La 〈 Pr 〈 Nd 〈 Sm 〈 Eu 〉 Gd 〈 Dy 〉 Yb. Results also indicate that the ternary lanthanide complexes of La（Ⅲ）, Pr（Ⅲ）, Nd（Ⅲ）, Sm（Ⅲ）, Eu（Ⅲ）, Gd（Ⅲ）, Dy（Ⅲ）, and Yb（ Ⅲ ） are more stable than corresponding binary lanthanide complexes. The enthalpy （△Hf^o） and entropy （△Sf^o） changes for the formation of binary and ternary complexes were calculated from temperature coefficient data. The △△Sf^o values are positive for all the metal ligand systems. The negative △△Hf^o values indicate the extra stability of the ternary complexes by the exothermic enthalpy changes （△△Sf^o = △TSf^o - △BSf^o and △△Hf^o = △THf^o - △BHf^o where △TSf^o, △THf^o and △BSf^o, △BHf^o are the entropy and enthalpy values associated with the ternary and binary complexes, respectively）. It was also proposed that the guanine is bonded to metal ions through N1/C6 = O and N7 whereas cytosine and its derivatives are bonded through N3 atoms in ternary complexes.

关键词： lanthanide solution studies cytosine thermodynamic properties rare earths

Strip-coalesced interior zone model for two unequal collinear cracks weakening piezoelectric media

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Applied Mathematics and Mechanics(English Edition) 2014年第10期35卷 1249-1260页

作者： R.R.BHARGAVA K.JANGID Department of Mathematics indian institute of technology roorkee

In this paper, a mathematical strip-saturation model is proposed for a poled transversely isotropic piezoelectric plate weakened by two impermeable unequal-collinear hairline straight cracks. Remotely applied in-plane unidirectional electromechanical loads open the cracks in mode-I such that the saturation zone developed at the interior tips of cracks gets coalesced. The developed saturation zones are arrested by distributing over their rims in-plane normal cohesive electrical displacement. The problem is solved using the Stroh formalism and the complex variable technique. The expressions are derived for the stress intensity factors （SIFs）, the lengths of the saturation zones developed, the crack opening displacement （COD）, and the energy release rate. An illustrative numerical case study is presented for the poled PZT-5H ceramic to investigate the effect of prescribed electromechanical loads on parameters affecting crack arrest. Also, the effect of different lengths of cracks on the SIFs and the local energy release rate （LERR） has been studied. The results obtained are graphically presented and analyzed.

关键词： crack opening displacement (COD) energy release rate piezoelectric ce-ramic Stroh formalism saturation zone unequal-collinear crack

Controlling Tendons to Modulate Stiffness of a Planar-to-Spatial Tendon-Driven Continuum Manipulator Under External Uncertain Forces

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Journal of Bionic Engineering 2024年第2期21卷 821-841页

作者： Vipin Pachouri Pushparaj Mani Pathak indian institute of technology roorkee Roorkee247667India

Continuum manipulators(CM)are soft and flexible manipulators with large numbers of degrees of freedom and can perform complex tasks in an unstructured ***,their deformability and compliance can deviate distal tip under uncertain external *** address this challenge,a novel tension-based control scheme has been proposed to modulate the stiffness of a tendon-driven CM,reducing the tip position errors caused by uncertain external *** minimize the tip position error,a virtual spring is positioned between the deviated and the desired tip *** proposed algorithm corrects the manipulator deviated tip position,improving tension distribution and stiffness profile,resulting in higher stiffness and better *** corresponding task space stiffness and condition numbers are also computed under different cases,indicating the effectiveness of the tension control scheme in modulating the manipulator's *** validation conducted on an in-house developed prototype confirms the practical feasibility of the proposed approach.

关键词： Continuum arm Hyper-redundant robots Variable stiffness manipulator Tension-based control Mechatronic systems

Influence of Sputtering Gas on Morphological and Optical Properties of Magnesium Films

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Journal of Materials Science & technology 2011年第1期27卷 51-58页

作者： Yogendra K.Gautam Amit K.Chawla Vipin Chawla R.D.Agrawal Ramesh Chandra Department of Metallurgical and Materials Engineering Indian Institute of Technology Roorkee Nano Science Laboratory Institute Instrumentation CentreIndian Institute of Technology Roorkee

The influence of sputtering gas（He Ar） on the structural properties of Mg thin films has been *** optical property（reflectance） that results from the growth of films at varying substrate temperatures（Tsub） was also *** deposited films were characterized by using X-ray diffraction（XRD）,field emission scaning electron microscopy（FE-SEM）,atomic force microscopy（AFM） and UV-Vis-NIR *** smaller crystallite size and lower deposition rate were observed in the presence of Helium atmosphere compared to *** of the films shows 2D hexagonal geometry of grains in the deposition temperature range（Tsub≈50-150℃） in both the sputtering *** surface roughness of the polycrystalline films were found to increase with increase in the deposition temperature of both ambient *** reflectance of Mg films was measured in near infrared region and larger reflectance was observed from Mg films sputtered in He atmosphere compared to that in argon.

关键词： X-ray diffraction(XRD) Atomic force microscopy(AFM) Reflectance Mg films Microstructure

Ballistic response of skin simulant against fragment simulating projectiles

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Defence technology（防务技术） 2023年第12期30卷 70-82页

作者： Punit Kumar Pandey Atul Harmukh M.K.Khan M.A.Iqbal S.G.Ganpule Department of Mechanical and Industrial Engineering Indian Institute of Technology Roorkee247667India Department of Civil Engineering Indian Institute of Technology Roorkee247667India Department of Design Indian Institute of Technology Roorkee247667India

The response of biological phantoms against high velocity impact is actively sought for applications in defense,space,soft robotics and *** this end,we study the ballistic response of silicone based skin simulant against fragment *** a pneumatic gas gun setup,six chisel-nosed and three regular shaped(sphere,cylinder,and cube)fragments were impacted on the skin *** resulting skin simulant response was studied in terms of ballistic limit velocities,energy densities,failure pattern,and the mechanics of *** results indicate that the shape of the fragment affects the ballistic limit *** ballistic limit velocities,energy densities of the chisel-nosed fragment simulating projectiles were relatively insensitive to the size(mass),except for the smallest(0.16 g)and largest(2.79 g)chisel-nosed *** the same size(1 g),ballistic limit velocities and failure are dependent on the shape of the *** skin simulant failed by combined plugging and elastic hole *** in the spherical fragment was dominated by the elastic hole enlargement,whereas plugging failure was dominant in all other *** spherical,cylindrical,and chisel-nosed fragments created circular cavities,and the cubical fragment created a square *** the case of the spherical fragment,slipping of the fragment within the skin simulant was *** fragments created lateral cracks emanating from the corners of the square ***,for all the fragments,the maximum deformation corresponding to the perforation was lower than the non-perforation indicating rate dependent,stress driven *** maximum deformation was also dependent on the shape of the ***,these results provide unique insights into the mechanical response of a soft simulant against ballistic *** have utility in the calibration and validation of computational models,design of personal protective equipment,and antipersonnel syste

关键词： Skin simulant Fragment Impact Ballistic limit velocity Energy density Failure

Landslide Hazard Zonation Mapping and Comparative Analysis of Hazard Zonation Maps

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Journal of Mountain Science 2008年第3期5卷 232-240页

作者： S.Sarkar R.Anbalagan Central Building Research institute Roorkee indian institute of technology Roorkee

Landslide hazard zonation mapping at regional level of a large area provides a broad trend of landslide potential zones. A macro level landslide hazard zonation for a small area may provide a better insight into the landslide hazards. The main objective of the present work was to carry out macro landslide hazard zonation mapping on 1:50,000 scale in an area where regional level zonation mapping was conducted earlier. In the previous work the regional landslide hazard zonation maps of Srinagar-Rudraprayag area of Garhwal Himalaya in the state of Uttarakhand were prepared using subjective and objective approaches. In the present work the landslide hazard zonation mapping at macro level was carried out in a small area using a Landslide Hazard Evaluation Factor rating scheme. The hazard zonation map produced by using this technique classifies the area into relative hazard classes in which the high hazard zones well correspond with high frequency of landslides. The results of this map when compared with the regional zonation maps prepared earlier show that application of the present technique identified more details of the hazard zones, which are broadly shown in the earlier zonation maps.

关键词： Landslides Hazard zonation Garhwal Himalaya Mapping

Strength behaviour of sandstone subjected to polyaxial state of stress

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International Journal of Mining Science and technology 2017年第6期27卷 889-897页

作者： Rukhaiyar Saurav Samadhiya Narendra Kumar Department of Civil Engineering Indian Institute of Technology Roorkee Roorkee 247667 India

The paper presents an experimental investigation on the strength behaviour of natural rock subjected to polyaxial state of stress. The polyaxial tests were conducted on cubical specimens of sandstone obtained from the Shivpuri district in Madhya Pradesh state of India, The specimens having nominal dimensions of100 mm x 100 mm x 100 mm were tested using a polyaxial testing machine. Twenty-five combinations of intermediate and minor principal stresses were applied and the specimens were loaded till failure occurs. It was observed that the intermediate principal stress has a substantial effect on the strength of the Shivpuri sandstone. A database of rock strength under various combinations of σ_2 and σ_3 was obtained for the Shivpuri sandstone. The database was used to study the predictability of five most commonly used strength criterion. Root mean square error(RMSE), average absolute relative error percentage(AAREP) and coefficient of accordance(COA) were used as indices for the measure of goodness of fit. It was observed that the least error in the prediction was shown by modified Mohr Coulomb criterion followed by modified Weibols and Cook criterion. A probability analysis of the error in prediction was also done.

关键词： Polyaxial testing Sandstone Strength criterion Modified Mohr-Coulomb criterion Modified Weibols and Cook criterion

Accounting for the uncertainties in the estimation of average shear wave velocity using VS-N correlations

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Frontiers of Structural and Civil Engineering 2021年第5期15卷 1199-1208页

作者： Jithin P ZACHARIAH Ravi S JAKKA Department of Earthquake Engineering Indian Institute of Technology RoorkeeRoorkee 247667India

Site-specific seismic hazard analysis is crucial for designing earthquake resistance structures,particularly in seismically active *** wave velocity(V_(S))is a key parameter in such analysis,although the economy and other factors restrict its direct field measurement in many *** V_(S)-SPT-N correlations are routinely incorporated in seismic hazard analysis to estimate the value of V_(S).However,many uncertainties question the reliability of these estimated V_(S)*** paper comes up with a statistical approach to take care of such uncertainties involved in V_(S)*** measured SPT-N values from all the critical boreholes were converted into statistical parameters and passed through various correlations to estimate V_(S)at different *** effect of different soil layers in the boreholes on the V_(S)estimation was also taken into ***,the average shear wave velocity of the top 30 m soil coverV_(S30))is estimated after accounting for various epistemic and aleatoric *** scattering nature of the V_(S)values estimated using different V_(S)-N correlations was reduced significantly with the application of the *** results further clearly demonstrated the potential of the approach to eliminate various uncertainties involved in the estimation of V_(S)30 using general and soil-specific correlations.

关键词： uncertainties V_(S)-N correlations V_(S30) SPT data statistical methodology