scholarly journals Bistable polar-orthotropic shallow shells

2019 ◽  
Vol 6 (8) ◽  
pp. 190888 ◽  
Author(s):  
P. M. Sobota ◽  
K. A. Seffen
Keyword(s):  
Beam Model ◽  
Stress Singularities ◽  
Shallow Shells ◽  
Radial Stiffness ◽  
Curvature Term ◽  
Nonlinear Analytical Model ◽  
Support Conditions ◽  
New Perspective ◽  
Orthotropic Shells ◽  
Polar Orthotropic

We investigate stabilizing and eschewing factors on bistability in polar-orthotropic shells in order to enhance morphing structures. The material law causes stress singularities when the circumferential stiffness is smaller than the radial stiffness ( β < 1), requiring a careful choice of the trial functions in our Ritz approach, which employs a higher-order geometrically nonlinear analytical model. Bistability is found to strongly depend on the orthotropic ratio, β , and the in-plane support conditions. An investigation of their interaction offers a new perspective on the effect of the hoop stiffness on bistability: while usually perceived as promoting, it is shown to be only stabilizing insofar as it prevents radial expansions; however, if in-plane supports are present, it becomes a redundant feature. Closed-form approximations of the bistable threshold are then provided by single-curvature-term approaches. For significantly stiffer values of the radial stiffness, a strong coupling of the orthotropic ratio and the support conditions is revealed: while roller-supported shells are monostable, fixed-pinned ones are most disposed to stable inversions; insight is given by comparing to a simplified beam model. Eventually, we show that cutting a central hole is a suitable method to deal with stress singularities: while fixed-pinned shells are barely affected by a hole, the presence of a hole strongly favours bistable inversions in roller-supported shells.

scholarly journals Free Vibration of Partially Supported Cylindrical Shells

1995 ◽  
Vol 2 (4) ◽  
pp. 297-306 ◽  
Author(s):  
S. Mirza ◽  
Y. Alizadeh
Keyword(s):  
Natural Frequencies ◽  
Numerical Solutions ◽  
Element Model ◽  
Rotor Blades ◽  
Shell Structures ◽  
Shallow Shells ◽  
Aspect Ratios ◽  
Small Deflection ◽  
Wide Range ◽  
Support Conditions

The effects of detached base length on the natural frequencies and modal shapes of cylindrical shell structures were investigated in this work. Some of the important applications for this type of problem can be found in the cracked fan and rotor blades that can be idealized as partially supported shells with varying unsupported lengths. A finite element model based on small deflection linear theory was developed to obtain numerical solutions for this class of problems. The numerical results were generated for shallow shells and some of the degenerate cases are compared with other results available in the literature. The computations presented here involve a wide range of variables: material properties, aspect ratios, support conditions, and radius to base ratio.

On the Perturbation Methods for Vibration Analysis of Linear Time-Varying Systems

2016 ◽  
Vol 08 (03) ◽  
pp. 1650035 ◽  
Author(s):  
Xiao-Dong Yang ◽  
Ming Liu ◽  
Wei Zhang ◽  
Ying-Jing Qian ◽  
Roderick V. N. Melnik
Keyword(s):  
Perturbation Methods ◽  
Multiple Scales ◽  
Linear Time ◽  
Harmonic Balance Method ◽  
Approximate Solutions ◽  
Beam Model ◽  
Time Varying ◽  
Analytical Approximations ◽  
Time Varying Systems ◽  
New Perspective

Some perturbation methods in the studying vibrations of the linear time-varying (LTV) system are discussed. Three classical perturbation methods, namely, averaging method, harmonic balance method, and multiple scales method with linear scales, have been used from a new perspective based on analytical approximations to the corresponding LTV ordinary differential equations. The deploying beam model has been taken as an example to validate the explicit approximate solutions obtained by these perturbation methods. It is demonstrated that such approximate solutions have good agreement with numerical and exact solutions, excluding the vicinity of the turning point.

scholarly journals The Influence of Symmetrical Boundary Conditions on the Structural Behaviour of Sandwich Panels Subjected to Torsion

Symmetry ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2093 ◽  
Author(s):  
Zbigniew Pozorski ◽  
Szymon Wojciechowski
Keyword(s):  
Boundary Conditions ◽  
Numerical Models ◽  
Sandwich Panels ◽  
Structural Response ◽  
Numerical Results ◽  
Beam Model ◽  
Structural Behaviour ◽  
High Agreement ◽  
Various Boundary Conditions ◽  
Support Conditions

The paper discusses the influence of load and support conditions on the behaviour of sandwich panels subjected to torsion. 3-D numerical models are presented, in which various boundary conditions have been defined. The case of the load causing the concentrated torque in the span is analyzed, and the load definition affects the structural response. The numerical results were compared with the results obtained for the analytical beam model, which included both free torsion and secondary warping torsion. The conditions under which the models achieve a high agreement between the results were determined, but the significant sensitivity of the solution was also indicated. In each case of the considered load and boundary conditions, the structural response shows appropriate symmetry.

SREM observation of the interaction between the in-situ deposited Pd small particles and MgO cleavage surface

1986 ◽  
Vol 44 ◽  
pp. 382-383
Author(s):  
H.-J. Ou
Keyword(s):  
Electron Microscopy ◽  
Small Particle ◽  
Small Particles ◽  
Cleavage Surface ◽  
Metallic Particles ◽  
Microscopy Technique ◽  
Ceramic Surfaces ◽  
Reflection Electron Microscopy ◽  
New Perspective

The understanding of the interactions between the small metallic particles and ceramic surfaces has been studied by many catalyst scientists. We had developed Scanning Reflection Electron Microscopy technique to study surface structure of MgO hulk cleaved surface and the interaction with the small particle of metals. Resolutions of 10Å has shown the periodic array of surface atomic steps on MgO. The SREM observation of the interaction between the metallic particles and the surface may provide a new perspective on such processes.

Articulation Training: A New Perspective

1979 ◽  
Vol 10 (3) ◽  
pp. 145-151 ◽  
Author(s):  
Sallie W. Hillard ◽  
Laura P. Goepfert
Keyword(s):  
Life Experience ◽  
Remediation Measures ◽  
New Perspective

This paper describes the concept of teaching articulation through words which have inherent meaning to a child’s life experience, such as a semantically potent word approach. The approach was used with six children. Comparison of pre/post remediation measures indicated that it has promise as a technique for facilitating increased correct phoneme production.

Centralization and Effectiveness of Reward Management in Multinational Enterprises

2018 ◽  
Vol 17 (2) ◽  
pp. 55-65 ◽  
Author(s):  
Michael Tekieli ◽  
Marion Festing ◽  
Xavier Baeten
Keyword(s):  
Decision Making ◽  
Social Identity Theory ◽  
Multinational Enterprises ◽  
Role Identity ◽  
Management Decision ◽  
Role Identities ◽  
Management Decision Making ◽  
New Perspective ◽  
Subsidiary Managers ◽  
The Relationship

Abstract. Based on responses from 158 reward managers located at the headquarters or subsidiaries of multinational enterprises, the present study examines the relationship between the centralization of reward management decision making and its perceived effectiveness in multinational enterprises. Our results show that headquarters managers perceive a centralized approach as being more effective, while for subsidiary managers this relationship is moderated by the manager’s role identity. Referring to social identity theory, the present study enriches the standardization versus localization debate through a new perspective focusing on psychological processes, thereby indicating the importance of in-group favoritism in headquarters and the influence of subsidiary managers’ role identities on reward management decision making.

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