Determination of the effective stiffness of a unidirectional layer by the finite element method and approximate formulas

2021 ◽  
Vol 87 (3) ◽  
pp. 40-50
Author(s):  
I. P. Olegin ◽  
T. V. Burnysheva ◽  
N. A. Laperdina
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Elastic Properties ◽  
Volume Content ◽  
Theory Of Elasticity ◽  
Effective Stiffness ◽  
The Finite Element Method ◽  
Approximate Formulas ◽  
Elastic Characteristics

Layered composites formed by unidirectional layers are widely used in aviation in the most loaded areas of the aircraft. Data on the elastic properties of the layers are required for the strength and stiffness calculation of structural elements made of such materials. There are two possible approaches to address the problem. The first approach is based on solving the problem of micromechanics using methods of the theory of elasticity. The second approach consists in developing a simplified model of a unidirectional layer. Analysis of the model can provide for fairly simple formulas for determination of the effective stiffness of a unidirectional layer. A comparative analysis of the results obtained in both approaches revealed the limits of applicability of approximate formulas derived for evaluating the effective characteristics of the different types of composites depending on the volume content of fibers. The effective elastic characteristics of unidirectional composites are determined by the finite element method in the framework of the linear theory of elasticity. The boundary value problem is solved for a characteristic representative element selected in accordance with the physical and geometric parameters of the medium of an ordered structure. A set of algorithm-programs has been developed under ANSYS environment which automates calculations of the elastic characteristics of materials depending on the volume content of fibers at different ratios of the elastic properties of fibers and binder, and on the parameters of the curvature of the fiber cross-sectional profile. The results obtained by the numerical method are compared with the data obtained experimentally and by approximate formulas.

Modification of the Local Variation Method to Minimize the Functionals of the Elasticity Theory

2018 ◽  
Vol 931 ◽  
pp. 174-177
Author(s):  
Muaed M. Oshkhunov ◽  
Madina A. Dzhankulaeva ◽  
Fatima M. Nakhusheva ◽  
Maria M. Tkabisimova
Keyword(s):  
Finite Element Method ◽  
Inverse Problem ◽  
Finite Element ◽  
Elasticity Theory ◽  
Local Variation ◽  
Theory Of Elasticity ◽  
Variation Method ◽  
The Finite Element Method ◽  
Counting Time ◽  
Elastic Characteristics

In this paper a modification of the local variation method for minimizing the elasticity functionals, which reduces the counting time when varying them with small steps is proposed. Example of the solution of the inverse problem of the theory of elasticity by the finite element method is given. The problem of finding the elastic characteristics of a three-layer cable insulation, in which the annular stresses and deformations practically do not vary radially, is solved.

An Analysis of Conventional and Self-Aligned four Terminal Resistor Structures for The Determination of The Contact Resistivity from End Resistance Measurements

1986 ◽  
Vol 71 ◽  
Author(s):  
I. Suni ◽  
M. Finetti ◽  
K. Grahn
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Computer Model ◽  
Contact Resistivity ◽  
Experimental Results ◽  
The Finite Element Method ◽  
Model Based ◽  
A Value ◽  
And Diffusion

AbstractA computer model based on the finite element method has been applied to evaluate the effect of the parasitic area between contact and diffusion edges on end resistance measurements in four terminal Kelvin resistor structures. The model is then applied to Al/Ti/n+ Si contacts and a value of contact resistivity of Qc = 1.8×10−7.Ωcm2 is derived. For comparison, the use of a self-aligned structure to avoid parasitic effects is presented and the first experimental results obtained on Al/Ti/n+Si and Al/CoSi2/n+Si contacts are shown and discussed.

Fatigue damage in bending of reinforced concrete frames using non-destructive tests for dynamic strength of the cylinder

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Dragan D. Milašinović ◽  
Aleksandar Landović ◽  
Danica Goleš
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Damage ◽  
Cross Section ◽  
Modal Parameters ◽  
The Finite Element Method ◽  
Concrete Frames ◽  
Content Type ◽  
Non Destructive

PurposeThe purpose of this paper is to contribute to the solution of the fatigue damage problem of reinforced concrete frames in bending.Design/methodology/approachThe problem of fatigue damage is formulated based on the rheological–dynamical analogy, including a scalar damage variable to address the reduction of stiffness in strain softening. The modal analysis is used by the finite element method for the determination of modal parameters and resonance stability of the selected frame cross-section. The objectivity of the presented method is verified by numerical examples, predicting the ductility in bending of the frame whose basic mechanical properties were obtained by non-destructive testing systems.FindingsThe modal analysis in the frame of the finite element method is suitable for the determination of modal parameters and resonance stability of the selected frame cross-section. It is recommended that the modulus of elasticity be determined by non-destructive methods, e.g. from the acoustic response.Originality/valueThe paper presents a novel method of solving the ductility in bending taking into account both the creep coefficient and the aging coefficient. The rheological-dynamical analogy (RDA) method uses the resonant method to find material properties. The characterization of the structural damping via the damping ratio is original and effective.

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