The Experts below are selected from a list of 156 Experts worldwide ranked by ideXlab platform
Reaz A Chaudhuri - One of the best experts on this subject based on the ideXlab platform.
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effect of inplane boundary Constraints on the response of thick general unsymmetric cross ply plates
Composite Structures, 2008Co-Authors: Ahmet Sinan Oktem, Reaz A ChaudhuriAbstract:A hitherto unavailable HSDT (higher-order shear deformation theory)-based boundary-discontinuous Fourier solution to the class of problems of general cross-ply plates that cannot be solved using the classical Navier or Levy type approach is presented. A self-adjoint differential system of five highly coupled fourth-order linear partial differential equations, subjected to SS1 and SS4-type simply supported boundary conditions prescribed at all four edges, is solved analytically using the boundary-discontinuous double Fourier series technique. The numerical accuracy of the solution is ascertained by studying the convergence characteristics of deflections and moments of an antisymmetric cross-ply plate. The primary focus of the present study is to investigate the effect of inplane boundary Constraints on the response of a thick asymmetrically laminated cross-ply plate, while keeping the remaining End Constraints unaltered. Important numerical results presented include sensitivity of the predicted response quantities of interest to lamination, material property, thickness effects and inplane End Constraint as well as their interactions.
Ahmet Sinan Oktem - One of the best experts on this subject based on the ideXlab platform.
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effect of inplane boundary Constraints on the response of thick general unsymmetric cross ply plates
Composite Structures, 2008Co-Authors: Ahmet Sinan Oktem, Reaz A ChaudhuriAbstract:A hitherto unavailable HSDT (higher-order shear deformation theory)-based boundary-discontinuous Fourier solution to the class of problems of general cross-ply plates that cannot be solved using the classical Navier or Levy type approach is presented. A self-adjoint differential system of five highly coupled fourth-order linear partial differential equations, subjected to SS1 and SS4-type simply supported boundary conditions prescribed at all four edges, is solved analytically using the boundary-discontinuous double Fourier series technique. The numerical accuracy of the solution is ascertained by studying the convergence characteristics of deflections and moments of an antisymmetric cross-ply plate. The primary focus of the present study is to investigate the effect of inplane boundary Constraints on the response of a thick asymmetrically laminated cross-ply plate, while keeping the remaining End Constraints unaltered. Important numerical results presented include sensitivity of the predicted response quantities of interest to lamination, material property, thickness effects and inplane End Constraint as well as their interactions.
J.z. Zhang - One of the best experts on this subject based on the ideXlab platform.
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Stick-slip failure in sheared fault with a variety of End Constraint degrees: An experimental study
Physics of the Earth and Planetary Interiors, 2020Co-Authors: Xiaoping Zhou, J.z. ZhangAbstract:Abstract For the commonly-used laboratory frictional earthquake model, unstable slip usually occurs without any End Constraint. This experimental design is contradictory to a simple fact: real faults are confined by their surroundings, and the relative sliding is not End-free. To investigate the effects of End Constraint conditions on the stick-slip behaviors, direct shear tests are conducted on PMMA sheets with three kinds of pre-crack length, and high sampling rate strain gage array and digital image correlation method are used to monitor the detailed processes of dislocation(stick-slip). We find that pre-crack length has great influence on the intervals of dislocation (stick-slip), the total number of dislocations (stick-slip) that occurs before crack extension, the magnitude of stress-drop and rupture velocity. A transition of the dislocation propagation velocity from sub-Rayleigh to super-shear is observed for PMMA sheets with a long pre-crack, while super-shear velocity rupture cannot be obtained in PMMA sheets with a short pre-crack.
Bradley A Lerch - One of the best experts on this subject based on the ideXlab platform.
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high strain rate behavior of ice under uniaxial compression
International Journal of Solids and Structures, 2009Co-Authors: Mostafa Shazly, Vikas Prakash, Bradley A LerchAbstract:Abstract In the present study, a modified split Hopkinson pressure bar (SHPB) is employed to investigate the dynamic response of ice under uniaxial compression in the range of strain rates from 60 to 1400 s−1 and at initial test temperatures of −10 and −30 °C. The compressive strength of ice shows positive strain-rate sensitivity over the range of strain rates employed; a slight influence of ice microstructure is observed, but it is much less than that reported previously for ice deformation under quasi-static loading conditions [Schulson, E.M., IIiescu, D., Frott, A., 2005. Characterization of ice for return-to-flight of the space shuttle. Part 1 – Hard ice. NASA CR-2005-213643-Part 1]. Specimen thickness, within the range studied, was found to have little or no effect on the peak (failure) strength of ice, while lowering the test temperature from −10 to −30 °C had a considerable effect, with ice behaving stronger at the lower test temperature. Moreover, unlike in the case of uniaxial quasi-static compression of ice, the effect of specimen End-Constraint during the high rate compression was found to be negligible. One important result of these experiments, which may have important implications in modeling ice impacts, involves the post “peak-stress” behavior of the ice in that the ice samples do not catastrophically lose their load carrying capacity even after the attainment of peak stress during dynamic compression. This residual (tail) strength of the damaged/fragmented ice is sizable, and in some cases is larger than the quasi-static compression strength reported for ice. Moreover, this residual strength is observed to be depEndent on sample thickness and the strain rate, being higher for thinner samples and at higher strain-rates during dynamic compression.
S. P. Harsha - One of the best experts on this subject based on the ideXlab platform.
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AN EFFICIENT FINITE ELEMENT MODEL FOR ANALYSIS OF SINGLE WALLED BORON NITRIDE NANOTUBE-BASED RESONANT NANOMECHANICAL SENSORS
NANO, 2013Co-Authors: Mitesh B. Panchal, S. H. Upadhyay, S. P. HarshaAbstract:In this paper, the dynamics analysis of single walled boron nitride nanotubes (SWBNNT) as a resonant nanomechanical sensor by using the finite element method has been reported. Molecular structural mechanics-based finite element model (FEM) has been developed by using three-dimensional elastic beams and point masses, such that the proximity of the model to the actual atomic structure of nanotube is significantly retained. Different types of armchair layups of SWBNNTs are considered with cantilevered and bridged End Constraints. By implementing the finite element simulation approach, the resonant frequency shift-based mass sensitivity analysis is performed for both types of End Constraints for considered armchair form of the SWBNNTs with different aspect ratios. For both types of End Constraint, continuum mechanics-based analytical formulations, considering effective wall thickness of nanotubes are used to validate the present FEM-based simulation approach. The intermediate landing position of the added ma...
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AN EFFICIENT FINITE ELEMENT MODEL FOR ANALYSIS OF SINGLE WALLED BORON NITRIDE NANOTUBE-BASED RESONANT NANOMECHANICAL SENSORS
Nano, 2013Co-Authors: Mitesh B. Panchal, S. H. Upadhyay, S. P. HarshaAbstract:In this paper, the dynamics analysis of single walled boron nitride nanotubes (SWBNNT) as a resonant nanomechanical sensor by using the finite element method has been reported. Molecular structural mechanics-based finite element model (FEM) has been developed by using three-dimensional elastic beams and point masses, such that the proximity of the model to the actual atomic structure of nanotube is significantly retained. Different types of armchair layups of SWBNNTs are considered with cantilevered and bridged End Constraints. By implementing the finite element simulation approach, the resonant frequency shift-based mass sensitivity analysis is performed for both types of End Constraints for considered armchair form of the SWBNNTs with different aspect ratios. For both types of End Constraint, continuum mechanics-based analytical formulations, considering effective wall thickness of nanotubes are used to validate the present FEM-based simulation approach. The intermediate landing position of the added mass is analyzed, considering variations in resonant frequency shifts of the different fundamental modes of vibrations for both types of End Constraints. The FEM-based simulation results for both types of End Constraints found in good agreement with the continuum mechanics-based analytical results for the aspect ratio of range of 9–15. The mass sensitivity limit of 10-1 zg is achieved for SWBNNT-based resonant nanomechanical sensors. The resonant frequency shift for higher-order fundamental vibrational modes become stable as the attached mass moves away from the fixed Ends for particular magnitude of attached mass. The present finite element-based approach is found to be effectual in terms of dealing different atomic structures, boundary conditions and consideration of added mass to analyze the dynamic behavior of the SWBNNT-based resonant nanomechanical sensors.