scholarly journals Buckling of a Pressurized Hemispherical Shell Subjected to a Probing Force

2017 ◽  
Vol 84 (12) ◽  
Author(s):  
Joel Marthelot ◽  
Francisco López Jiménez ◽  
Anna Lee ◽  
John W. Hutchinson ◽  
Pedro M. Reis
Keyword(s):  
Mechanical Response ◽  
Nondestructive Method ◽  
Pressure Loading ◽  
Spherical Shells ◽  
Nondestructive Technique ◽  
Nonlinear Load ◽  
Elastic Shells ◽  
Geometric Imperfection ◽  
Hemispherical Shell ◽  
The Stability

We study the buckling of hemispherical elastic shells subjected to the combined effect of pressure loading and a probing force. We perform an experimental investigation using thin shells of nearly uniform thickness that are fabricated with a well-controlled geometric imperfection. By systematically varying the indentation displacement and the geometry of the probe, we study the effect that the probe-induced deflections have on the buckling strength of our spherical shells. The experimental results are then compared to finite element simulations, as well as to recent theoretical predictions from the literature. Inspired by a nondestructive technique that was recently proposed to evaluate the stability of elastic shells, we characterize the nonlinear load-deflection mechanical response of the probe for different values of the pressure loading. We demonstrate that this nondestructive method is a successful local way to assess the stability of spherical shells.

A NONDESTRUCTIVE TECHNIQUE FOR MEASURING SEEDLING VIGOR IN WHEAT

1977 ◽  
Vol 57 (3) ◽  
pp. 983-985 ◽  
Author(s):  
L. E. EVANS ◽  
G. M. BHATT
Keyword(s):  
Nondestructive Method ◽  
Seedling Vigor ◽  
Nondestructive Technique ◽  
Breeding Programs ◽  
Shoot Weight ◽  
Subsequent Regeneration ◽  
Green Shoot

A nondestructive method of screening for seedling vigor is described. The technique involves the measurement of green shoot weight and the subsequent regeneration of the plants from transplanted shoots or from the seedling base. The method is quick and can be adapted to breeding programs.

Elastic Averaging in Flexure Mechanisms: A Muliti-Beam Parallelogram Flexure Case-Study

2006 ◽  
Author(s):  
Shorya Awtar ◽  
Edip Sevincer
Keyword(s):  
Mechanism Design ◽  
Parametric Model ◽  
Nonlinear Load ◽  
Geometric Imperfections ◽  
Geometric Imperfection ◽  
Flexure Mechanism ◽  
Important Concern ◽  
Proposed Model ◽  
Geometric Arrangements

Over-constraint is an important concern in mechanism design because it can lead to a loss in desired mobility. In distributed-compliance flexure mechanisms, this problem is alleviated due to the phenomenon of elastic averaging, thus enabling performance-enhancing geometric arrangements that are otherwise unrealizable. The principle of elastic averaging is illustrated in this paper by means of a multi-beam parallelogram flexure mechanism. In a lumped-compliance configuration, this mechanism is prone to over-constraint in the presence of nominal manufacturing and assembly errors. However, with an increasing degree of distributed-compliance, the mechanism is shown to become more tolerant to such geometric imperfections. The nonlinear load-stiffening and elasto-kinematic effects in the constituent beams have an important role to play in the over-constraint and elastic averaging characteristics of this mechanism. Therefore, a parametric model that incorporates these nonlinearities is utilized in predicting the influence of a representative geometric imperfection on the primary motion stiffness of the mechanism. The proposed model utilizes a beam generalization so that varying degrees of distributed compliance are captured using a single geometric parameter.

Non-Linear Dynamic Stability of Shallow Reticulated Spherical Shells

2011 ◽  
Vol 142 ◽  
pp. 107-110
Author(s):  
Ming Jun Han ◽  
You Tang Li ◽  
Ping Qiu ◽  
Xin Zhi Wang
Keyword(s):  
Three Dimensional ◽  
Dynamical Equations ◽  
Third Order ◽  
Spherical Shells ◽  
Nonlinear Dynamical ◽  
Linear Dynamic ◽  
The Third ◽  
Displacement Mode ◽  
Nonlinear Forced Vibration ◽  
The Stability

The nonlinear dynamical equations are established by using the method of quasi-shells for three-dimensional shallow spherical shells with circular bottom. Displacement mode that meets the boundary conditions of fixed edges is given by using the method of the separate variable, A nonlinear forced vibration equation containing the second and the third order is derived by using the method of Galerkin. The stability of the equilibrium point is studied by using the Floquet exponent.

Analysis of Nonlinear Buckling of a Long-Span Elliptic Paraboloid Suspended Dome Structure

2013 ◽  
Vol 639-640 ◽  
pp. 191-197 ◽  
Author(s):  
Zheng Rong Jiang ◽  
Kai Rong Shi ◽  
Xiao Nan Gao ◽  
Qing Jun Chen
Keyword(s):  
Single Layer ◽  
Buckling Mode ◽  
Nonlinear Buckling ◽  
Elliptic Paraboloid ◽  
Geometric Imperfection ◽  
Long Span ◽  
Initial Geometric Imperfection ◽  
Dome Structure ◽  
Unsymmetrical Loading ◽  
The Stability

The suspended dome structure, which is a new kind of hybrid spatial one composed of the upper single layer latticed shell and the lower cable-strut system, generally has smaller rise-to-span ratio, thus the overall stability is one of the key factors to the design of the structure. The nonlinear buckling behavior of an elliptic paraboloid suspended dome structure of span 110m80m is investigated by introducing geometric nonlinearity, initial geometric imperfection, material elastic-plasticity and half-span distribution of live loads. The study shows that the coefficient of stable bearing capacity usually is not minimal when the initial geometric imperfection configuration is taken as the first order buckling mode. The unsymmetrical loading distribution and the material nonlinearity might have significant effects on the coefficient. The structure is sensitive to the changes of initial geometric imperfection, and the consistent mode imperfection method is not fully applicable to the stability analysis of suspended dome structure.

scholarly journals Nonlinear thermo-mechanical stability of shear deformable FGM sandwich shallow spherical shells with tangential edge constraints

2017 ◽  
Vol 39 (4) ◽  
pp. 351-364
Author(s):  
Nguyen Minh Khoa ◽  
Hoang Van Tung
Keyword(s):  
Mechanical Stability ◽  
Effective Properties ◽  
Geometrical Nonlinearity ◽  
Geometrical Parameters ◽  
Boundary Edge ◽  
Power Law Distribution ◽  
Spherical Shells ◽  
Nonlinear Load ◽  
Elastic Foundations ◽  
Thermal Environments

This paper presents an analytical approach to investigate the nonlinear axisymmetric response of moderately thick FGM sandwich shallow spherical shells resting on elastic foundations, exposed to thermal environments and subjected to uniform external pressure. Material properties are assumed to be temperature independent, and effective properties of FGM layer are graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents. Formulations are based on first-order shear deformation shell theory taking geometrical nonlinearity, initial geometrical imperfection, Pasternak type elastic foundations and various degree of tangential constraint of boundary edge into consideration. Approximate solutions are assumed to satisfy clamped boundary condition and Galerkin method is applied to derive closed-form expressions of critical buckling loads and nonlinear load-deflection relation. Effects of geometrical parameters, thickness of face sheets, foundation stiffness, imperfection, thermal environments and degree of tangential edge constraints on the nonlinear stability of FGM sandwich shallow spherical shells are analyzed and discussed. 

Thermal Stability of Magnetic Properties in Dehydrogenated Triarylmethane Resins

1989 ◽  
Vol 173 ◽  
Author(s):  
Michiya Otani ◽  
Sugio Otani
Keyword(s):  
Thermal Stability ◽  
Magnetic Properties ◽  
Magnetic Property ◽  
Room Temperature ◽  
Permanent Magnets ◽  
Elevated Temperatures ◽  
Mechanical Response ◽  
The Stability ◽  
Thermal Stability Of

ABSTRACTThe stability of the magnetic properties of dehydrogenated triaryl-methane resins was investigated both at room temperature and at elevated temperatures. A magnetic property different from that reported in a previous paper was found in the course of studying the reproducibility of synthesis. This new property was examined through a mechanical response of the resins to a set of permanent magnets.

Asymptotic shapes of inflated spheroidal nonlinearly elastic shells

1985 ◽  
Vol 97 (3) ◽  
pp. 541-549 ◽  
Author(s):  
Stuart S. Antman ◽  
M. Carme Calderer
Keyword(s):  
Hydrostatic Pressure ◽  
Asymptotic Behaviour ◽  
Large Volume ◽  
Large Parameter ◽  
Spherical Shells ◽  
Elastic Shells ◽  
Nonlinearly Elastic

In this paper we study the asymptotic behaviour of large axisymmetric deformations of closed axisymmetric nonlinearly elastic shells under internal hydrostatic pressure. These shells can suffer flexure, extension, and shear. Since there are spherical shells that can enclose an arbitrarily large volume at a finite pressure (cf. [1]), we take the volume rather than the pressure as the large parameter.

scholarly journals Subloading Surface Model and Experimental Study of Coal Failure under Cyclic Loading

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Si-fei Liu ◽  
Zhi-jun Wan ◽  
Jing-chao Wang ◽  
Shuai-feng Lu ◽  
Tong-huan Li
Keyword(s):  
Cyclic Loading ◽  
Mechanical Response ◽  
Surface Model ◽  
Deformation Characteristics ◽  
Response Characteristics ◽  
Rock Structure ◽  
Specific Strain ◽  
Damage Process ◽  
The Stability ◽  
Number Of Cycles

The fatigue damage of rock is an important factor affecting the stability of rock structure. In this paper, the mechanical response of coal under cyclic loading was studied. In order to accurately describe the deformation characteristics of coal under cyclic loading, an elastic-plastic model of coal based on the theory of subloading surface was established and verified by experiments. The model can well reflect the Mancin effect and ratcheting effect of coal samples, which is basically consistent with the actual deformation characteristics of coal, and the theoretical value and experimental value are in good agreement. At the same time, the cyclic response characteristics of specimens under strain load disturbance were analyzed. The results show that the specific strain disturbance can only cause a certain damage to coal and the area of hysteresis loop decreases first, then stabilizes, and then increases as the number of cycles increases. In addition, the damage factor Dn in the model was analyzed in this paper. Dn, which can accurately describe the damage process of coal, accurately locate the time point of disturbance load change, and has greater sensitivity to coal failure, is helpful to improve the accuracy of the stability judgment of coal structure and ensure the safety of engineering. The above results are of great significance for strengthening the understanding of coal mass instability process and mode under cyclic loading.

scholarly journals First-Principles Study of the Stabilization and Mechanical Properties of Rare-Earth Ferritic Perovskites (RFeO3, R = La, Eu, Gd)

2020 ◽  
Vol 10 (11) ◽  
pp. 4008
Author(s):  
Mahdi Faghihnasiri ◽  
Vahid Najafi ◽  
Farzaneh Shayeganfar ◽  
Ali Ramazani
Keyword(s):  
Mechanical Properties ◽  
Rare Earth ◽  
First Principles ◽  
Density Functional ◽  
Mechanical Response ◽  
External Loading ◽  
Chemical Bonds ◽  
Functional Theory ◽  
Density Values ◽  
The Stability

Current research aims to investigate the mechanical properties of rare earth perovskite ferrites (RFeO3, R = La, Eu, Gd) utilizing density functional theory (DFT) calculations. Using the revised Perdew–Burke–Ernzerhof approximation for solids (PBEsol) approximation, the elastic constants, bulk, Young’s, and shear modulus, Poisson’s ratio, and anisotropic properties are calculated. The quantum theory of atoms in molecules (QTAIM) is employed to analyze the stability of chemical bonds in the structures subjected to an external loading. Based on these calculations, Fe-O and R-O bonds can be considered as nearly ionic, which is due to the large difference in electronegativity of R and Fe with O. Additionally, our results reveal that the charge density values of the Fe-O bonds in both structures remain largely outside of the ionic range. Finally, the mechanical response of LaFeO3, EuFeO3, and GdFeO3 compounds to various cubic strains is investigated. The results show that in RFeO3 by increasing the radius of the lanthanide atom, the mechanical properties of the material including Young’s and bulk modulus increase.

scholarly journals Shock-Sensitivity in Shell-Like Structures: With Simulations of Spherical Shell Buckling

2016 ◽  
Vol 26 (02) ◽  
pp. 1630003 ◽  
Author(s):  
J. Michael T. Thompson ◽  
Jan Sieber
Keyword(s):  
Spherical Shell ◽  
Severe Form ◽  
Nondestructive Technique ◽  
Nonlinear Load ◽  
Shock Sensitivity ◽  
Shell Buckling ◽  
General Terms ◽  
Lateral Disturbance ◽  
Laboratory Specimen ◽  
Asymmetric Solution

Under increasing compression, an unbuckled shell is in a metastable state which becomes increasingly precarious as the buckling load is approached. So to induce premature buckling, a lateral disturbance will have to overcome a decreasing energy barrier which reaches zero at buckling. Two archetypal problems that exhibit a severe form of this behavior are the axially-compressed cylindrical shell and the externally pressurized spherical shell. Focusing on the cylinder, a nondestructive technique was recently proposed to estimate the “shock-sensitivity” of a laboratory specimen using a lateral probe to measure the nonlinear load-deflection characteristic. If a symmetry-breaking bifurcation is encountered on the path, computer simulations showed how this can be suppressed by a controlled secondary probe. Here, we extend our understanding by assessing in general terms how a single control can capture remote saddle solutions: in particular, how a symmetric probe could locate an asymmetric solution. Then, more specifically, we analyze the spherical shell with point and ring probes, to test the procedure under challenging conditions to assess its range of applicability. Rather than a bifurcation, the spherical shell offers the challenge of a destabilizing fold (limit point) under the rigid control of the probe.

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