1,393 research outputs found
On the equivalence between the cell-based smoothed finite element method and the virtual element method
We revisit the cell-based smoothed finite element method (SFEM) for
quadrilateral elements and extend it to arbitrary polygons and polyhedrons in
2D and 3D, respectively. We highlight the similarity between the SFEM and the
virtual element method (VEM). Based on the VEM, we propose a new stabilization
approach to the SFEM when applied to arbitrary polygons and polyhedrons. The
accuracy and the convergence properties of the SFEM are studied with a few
benchmark problems in 2D and 3D linear elasticity. Later, the SFEM is combined
with the scaled boundary finite element method to problems involving
singularity within the framework of the linear elastic fracture mechanics in
2D
Adaptive identification and control of structural dynamics systems using recursive lattice filters
A new approach for adaptive identification and control of structural dynamic systems by using least squares lattice filters thar are widely used in the signal processing area is presented. Testing procedures for interfacing the lattice filter identification methods and modal control method for stable closed loop adaptive control are presented. The methods are illustrated for a free-free beam and for a complex flexible grid, with the basic control objective being vibration suppression. The approach is validated by using both simulations and experimental facilities available at the Langley Research Center
AN ALGORITHM FOR RESPONSE AND STABILITY OF LARGE ORDER NON-LINEAR SYSTEMS — APPLICATION TO ROTOR SYSTEMS
International audienceA numerical algorithm to calculate the periodic response, stability and bifurcations of a periodically excited non-conservative, Multi-Degree of Freedom (MDOF) system with strong local non-linearities is presented. First, the given large order system is reduced using a fixed-interface component mode synthesis procedure (CMS) in which the degrees of freedom associated with non-linear elements are retained in the physical co-ordinates while all others, whose number far exceeds the number of non-linear DOF, are transformed tomodal coordinates and reduced using real mode CMS. A shooting and continuation method is then applied to the reduced system to solve for the periodic response. Floquet stability theory is used to calculate stability and bifurcations of the periodic response. The algorithm is applied to study the response to imbalance, stability, and bifurcations of a 24 DOF flexible rotor supported on journal bearings. The results indicate that the proposed algorithm, though approximate, can yield very accurate information about dynamic behavior of large order non-linear systems, even with few numbers of retained component modes. The algorithm, which imposes less demand on computer time and memory, is believed to be of considerable potential in analyzing a variety of practical problems
Intuitionistic Robust Fuzzy Matrix for the Diagnosis of Stress, Anxiety and Hypertension
The mathematical model given here attempts to improve precisionin the diagnosis of stress, anxiety, and hypertension using Intuitionisticrobust fuzzy matrix (IRFM). In practice, the imprecise natureof medical documentation and the uncertainty of patient informationfrequently do not provide the appropriate level of confidence in thediagnosis. To that purpose, a novel method based on distinct fuzzymatrices and fuzzy relations is devised, which makes use of the capabilitiesof fuzzy logic in describing, understanding, and exploitingfacts and information that are unclear and lack clarity. With the assistanceof 30 doctors, a medical knowledge base is created during theprocedure. The model obtained 95.55%t accuracy in the diagnosis,demonstrating its utility
A volume-averaged nodal projection method for the Reissner-Mindlin plate model
We introduce a novel meshfree Galerkin method for the solution of
Reissner-Mindlin plate problems that is written in terms of the primitive
variables only (i.e., rotations and transverse displacement) and is devoid of
shear-locking. The proposed approach uses linear maximum-entropy approximations
and is built variationally on a two-field potential energy functional wherein
the shear strain, written in terms of the primitive variables, is computed via
a volume-averaged nodal projection operator that is constructed from the
Kirchhoff constraint of the three-field mixed weak form. The stability of the
method is rendered by adding bubble-like enrichment to the rotation degrees of
freedom. Some benchmark problems are presented to demonstrate the accuracy and
performance of the proposed method for a wide range of plate thicknesses
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