scholarly journals Stability of a Micro-Heterogeneous Plate Band

2015 ◽  
Vol 61 (4) ◽  
pp. 91-106
Author(s):  
M. Chalecki ◽  
G. Jemielita
Keyword(s):  
Stiffness Matrix ◽  
Computational Algorithm ◽  
Individual Cell ◽  
Variable Stiffness ◽  
Critical Force ◽  
The Finite Element Method ◽  
Critical Buckling Force ◽  
Support Conditions ◽  
Heterogeneous Plate ◽  
Number Of Cells

The paper presents a certain way which determines the critical buckling force for a micro-heterogeneous FGM plate band. A stiffness matrix of an individual cell of such band, different for various cells, has been determined. The obtained matrix can also be treated as a variable stiffness matrix of a “superelement” in the Finite Element Method. A computational algorithm for the critical force as well as the way of testing of its correctness has also been presented. The results obtained for various support conditions have been compared to the values known from the literature. The influence of the number of cells on the critical buckling force has been investigated.

Load-induced stiffness matrix of plates

2002 ◽  
Vol 29 (1) ◽  
pp. 181-184 ◽  
Author(s):  
Shi-Jun Zhou
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stiffness Matrix ◽  
Element Formulation ◽  
The Finite Element Method ◽  
Closed Form Solutions ◽  
Stiffness Matrices ◽  
Support Conditions ◽  
Stiffening Effect ◽  
Element Method

In this paper, a rectangular plate element for the finite-element method, which takes into consideration the stiffening effect of dead loads, is proposed. The element stiffness matrices that include the effect of dead loads are derived. The effect of dead loads on dynamic behaviors of plates is analyzed using the finite-element method. It is shown that the stiffness of plates increases when the effect of dead loads is included in the calculation and that the effect is more significant for plates with a smaller stiffness. The validity of the proposed procedure is confirmed by numerical examples. Although the finite-element results obtained are in agreement with the approximate closed-form solutions, the proposed method based on a finite-element formulation is more easily applied to practical structures under various support conditions and various types of dead loads.Key words: load-induced stiffness matrix of plate, stiffening effect of dead loads.

scholarly journals Distributed variable stiffness joint assist mechanism based on laminated structure

2021 ◽  
Vol 18 (6) ◽  
pp. 172988142110606
Author(s):  
Zhenquan Fan ◽  
Xiaoyu Wang ◽  
Zijin Wang ◽  
Sijia Gao ◽  
Sheng Lin
Keyword(s):  
Magnetic Field ◽  
Stiffness Matrix ◽  
Variable Stiffness ◽  
Drive Unit ◽  
Joint Power ◽  
Laminated Structure ◽  
Giant Magnetostrictive Material ◽  
In Series ◽  
Field Excitation ◽  
The Magnetic Field

Exoskeleton technology is more and more widely used in military, human rehabilitation, and other fields, but exoskeleton assisting mechanisms have problems such as high quality, concentrated driving sources, and poor flexibility. This article proposes a distributed variable stiffness joint power-assisted mechanism based on a laminated structure, which uses a giant magnetostrictive material as the driving source and the variable stiffness source of the structure. The distributed driving is realized by multiple driving units connected in series and parallel. Firstly, the drive unit stiffness matrix is deduced, and the expression equations of the cascaded total stiffness matrix of the drive module are obtained. After the simulation study, the curve of the stiffness of a single drive unit with a magnetic field and the stiffness of multiple drive units connected in series and parallel are in the absence of the magnetic field. The change curve of the stiffness of the booster module with the number of drive units under the excitation and saturation magnetic field excitation conditions is to achieve the effect of dynamically controlling the structural stiffness of the drive unit by controlling the size of the magnetic field and to obtain a general formula through data fitting. The number of drive units required under a fixed magnetic field excitation can ensure that the error is within 5%. The research results lay the foundation for further analysis of the distributed variable stiffness joint assist technology.

Tracheal Smooth Muscle Response to Vibrations

2004 ◽  
Author(s):  
Y. Du ◽  
A. M. Al-Jumaily
Keyword(s):  
Finite Element ◽  
Smooth Muscle ◽  
Smooth Muscles ◽  
Variable Stiffness ◽  
Tracheal Smooth Muscle ◽  
Element Formulation ◽  
The Finite Element Method ◽  
External Excitation ◽  
Stiffness Variation ◽  
Smooth Muscle Contractions

An experimental and theoretical investigation is conducted to study the dynamic response of a tracheal smooth muscle under isometric conditions. The stiffness variation due to external vibration is investigated experimentally using trachea smooth muscles from excised pigs. The finite element method is used to model the muscle as a 2-D strip with variable stiffness and subjected to an external excitation. The Cauchy’s first law is invoked to describe the motion and Galerkin’s method is used to develop the finite element formulation. Different boundary conditions are considered to simulate the vibration characteristics and to get realistic compatibility with actual muscle conditions. The model predicts the stiffness variation due to vibration that is observed experimentally. The main outcome from this investigation is the fact that smooth muscle contractions could be relaxed by tuning the excitation within predetermined frequencies.

Development of Bifurcation Analysis Method for Rate Dependent Materials

2019 ◽  
Vol 794 ◽  
pp. 220-225
Author(s):  
Daiki Towata ◽  
Yuichi Tadano
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Bifurcation Analysis ◽  
Stiffness Matrix ◽  
Computational Method ◽  
Analysis Method ◽  
The Finite Element Method ◽  
Tangent Stiffness Matrix ◽  
Rate Dependent ◽  
Element Method

In this study, a novel numerical method to analyze the bifurcation problemof a rate dependent material using the finite element method is proposed. The consistent stiffness matrix, which is required for a bifurcation analysis using the finite element method, for a rate dependent material is generally hard to compute, therefore, a computational method to calculate the tangent stiffness matrix based on a numerical differential is introduced so that exact bifurcation analyses for the rate dependent material can be conducted. A numerical example of the proposed method is demonstrated, and the adequacy of the proposed method is discussed.

On the Unsymmetric Eigenproblem for the Buckling of Shells Under Pressure Loading

1983 ◽  
Vol 50 (1) ◽  
pp. 95-100 ◽  
Author(s):  
H. A. Mang ◽  
R. H. Gallagher
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Hydrostatic Pressure ◽  
Stiffness Matrix ◽  
Circular Cylindrical Shell ◽  
The Finite Element Method ◽  
Equilibrium Equations ◽  
Buckling Loads ◽  
Large Rotations ◽  
Element Method

Consideration of the dependence of hydrostatic pressure on the displacements may result in significant changes of calculated buckling loads of thin arches and shells in comparison with loads calculated without consideration of this effect. The finite element method has made it possible to quantify these changes. On the basis of a shell theory of small displacements but moderately large rotations, this paper derives consistent incremental equilibrium equations for tracing, via the finite element method, the load-displacement path for thin shells subjected to nonuniform hydrostatic pressure and establishes the buckling condition from the incremental equilibrium equations. Within the framework of the finite element method, the character of hydrostatic pressure as one of a follower load is represented in the so-called pressure-stiffness matrix. For shells with loaded free edges, this matrix is unsymmetric. The principal objective of the present paper is to demonstrate that symmetrization of the pressure stiffness matrix resulting from linearization of the buckling condition yields buckling loads that are identical to the eigenvalues resulting from first-order perturbation analysis of the unsymmetric eigenproblem. A circular cylindrical shell with a free and a hinged end, subjected to hydrostatic pressure, is used as an example of the admissibility of symmetrizing the pressure stiffness matrix and for assessing its effect.

scholarly journals cAMP and Ca(2+)-mediated secretion in parotid acinar cells is associated with reversible changes in the organization of the cytoskeleton.

1992 ◽  
Vol 116 (1) ◽  
pp. 127-134 ◽  
Author(s):  
D Perrin ◽  
K Möller ◽  
K Hanke ◽  
H D Söling
Keyword(s):  
Plasma Membrane ◽  
Individual Cell ◽  
Acinar Cells ◽  
Alpha Amylase ◽  
Dibutyryl Cyclic Amp ◽  
Cell Level ◽  
Regulated Secretion ◽  
Parotid Acinar Cells ◽  
The Individual ◽  
Number Of Cells

The potential involvement of actin and fodrin (brain spectrin) in secretory events has been assessed in primary cultured guinea pig parotid acinar cells, using as a tool affinity purified anti-alpha-fodrin antibody, phalloidin, and immunofluorescence techniques. In resting parotid acinar cells fodrin and actin appeared as a continuous ring under the plasma membrane of most of the cells. Upon stimulation with secretagogues fodrin and actin labeling at the level of the plasma membrane disappeared almost completely. To establish a correlation between secretion and cytoskeletal changes at the individual cell level, anti-alpha-amylase-antibodies were used to label secreted amylase exposed at the surface of secreting cells. The number of cells expressing alpha-amylase on their surface followed bulk secretion of alpha-amylase. A strict correlation between secretion and alteration of the actin-fodrin labeling was observed at the individual cell level. The cytoskeletal changes occurred in parallel with secretion independently of the secretagogue used (carbamoylcholine in the presence of Ca2+, isoproterenol in presence or absence of Ca2+, forskolin, or dibutyryl-cyclic-AMP). The changes were reversible upon removal of the secretagogue. Since Ca2+, as well as cAMP-mediated secretion, was associated with the same kind of cytoskeletal changes, a reorganization of the cytoskeleton may play an essential part in regulated secretion.

Study of Elastic–Plastic Fracture Problem Using Finite Element Technique

1984 ◽  
Vol 106 (4) ◽  
pp. 476-482
Author(s):  
F. T. C. Loo
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stiffness Matrix ◽  
Graphical Form ◽  
The Finite Element Method ◽  
Finite Element Technique ◽  
Elastic Plastic ◽  
Center Crack ◽  
Initial Stress Method ◽  
Element Technique

Numerical methods for the analysis of the elastic-plastic fracture problem using a special finite element technique are presented. A brief description of some concepts in elastic-plastic fracture mechanics and of the finite element method is followed by the formulation procedure of the stiffness matrix using eight-noded quadrilateral isoparametric elements. After a terse discussion of the initial stress method, the procedure of computation is extended in the analysis by using an incremental load process. The size and the shape of the plastic zone of a center crack specimen is investigated. Results are presented in graphical form.

Sign in / Sign up

Export Citation Format

Share Document