scholarly journals Modelling of Ring-Shaped Compound Ultrasonic Waveguides by Means of Finite Elements Method

2021 ◽  
Vol 20 (6) ◽  
pp. 476-481
Author(s):  
D. A. Stepanenko ◽  
K. A. Bunchuk
Keyword(s):  
Finite Elements ◽  
Amplification Factor ◽  
Practical Interest ◽  
Numerical Data ◽  
Finite Elements Method ◽  
Constant Sign ◽  
Local Maxima ◽  
Engineering Software ◽  
Timoshenko Type ◽  
Selection Of

The paper describes a technique for modelling and optimization of ring-shaped compound ultrasonic waveguides consisting of two sequentially joined segments of different materials by means of finite elements method. The possibility of using such waveguides for amplifying vibrations in amplitude has been justified in the paper. The advantage of the developed technique consists in possibility of its realization by means of standard engineering software, particularly COMSOL Multiphysics. The correctness and efficiency of the technique is proved by comparing the numerical data with the simulation results by means of transfer matrix method using equations of vibration of Euler – Bernoulli and Timoshenko type. It is shown that in compound ring-shaped waveguides two kinds of vibration modes are possible – variable-sign and constant-sign, moreover only constant-sign modes are of practical interest for amplification of vibration amplitude. Recommendations for selection of optimal geometric parameters of the waveguides are given, particularly it is shown that for ensuring maximum vibration amplification factor it is necessary to choose central angles of the waveguide segments with account for calculated dependence between amplification factor and angle, characterized by presence of several local maxima of the amplification factor. It is noted that the high accuracy of the existing semi-analytical methods for calculating and designing ring-shaped waveguides is achieved using methods based on the application of Timoshenko-type equations of vibration.

Behavior Diagnostics of Bucket Wheel Support Structure Using Finite Elements Method: Optimization of Structures

2015 ◽  
Vol 806 ◽  
pp. 187-196
Author(s):  
Predrag Jovančić ◽  
Dragan Medenica ◽  
Vladimir Milisavljević ◽  
Ivica Ristović
Keyword(s):  
Stress Concentration ◽  
Finite Elements ◽  
Working Conditions ◽  
Deformation Energy ◽  
Finite Elements Method ◽  
Method Optimization ◽  
Open Cast Mine ◽  
Open Cast ◽  
Selection Of ◽  
Specific Working

Most common types of bucket wheels were analyzed by finite elements method in this paper. Also, relevant diagnostics parameters are defined for various constructions (stress concentration, deformation energy, distribution of potential and kinetic energy for main oscillation shapes). This approach enabled identification of weak spots and selection of such types of bucket wheel which are most suitable for specific working conditions on open cast mine.

scholarly journals Finite element modeling of multiple density materials of bone specimens for biomechanical behavior evaluation

2021 ◽  
Vol 3 (9) ◽  
Author(s):  
Sebastián Irarrázaval ◽  
Jorge Andrés Ramos-Grez ◽  
Luis Ignacio Pérez ◽  
Pablo Besa ◽  
Angélica Ibáñez
Keyword(s):  
Finite Elements ◽  
Computational Models ◽  
Reaction Force ◽  
Elastic Stiffness ◽  
Finite Elements Method ◽  
Mechanical Resistance ◽  
Assessment Procedure ◽  
Axial Tomography ◽  
Biomechanical Behavior ◽  
Ct Data

AbstractThe finite elements method allied with the computerized axial tomography (CT) is a mathematical modeling technique that allows constructing computational models for bone specimens from CT data. The objective of this work was to compare the experimental biomechanical behavior by three-point bending tests of porcine femur specimens with different types of computational models generated through the finite elements’ method and a multiple density materials assignation scheme. Using five femur specimens, 25 scenarios were created with differing quantities of materials. This latter was applied to computational models and in bone specimens subjected to failure. Among the three main highlights found, first, the results evidenced high precision in predicting experimental reaction force versus displacement in the models with larger number of assigned materials, with maximal results being an R2 of 0.99 and a minimum root-mean-square error of 3.29%. Secondly, measured and computed elastic stiffness values follow same trend with regard to specimen mass, and the latter underestimates stiffness values a 6% in average. Third and final highlight, this model can precisely and non-invasively assess bone tissue mechanical resistance based on subject-specific CT data, particularly if specimen deformation values at fracture are considered as part of the assessment procedure.

Determination of residual stresses in disk keyways by the finite-elements method

1982 ◽  
Vol 14 (7) ◽  
pp. 865-867
Author(s):  
B. A. Kravchenko ◽  
V. G. Fokin ◽  
G. N. Gutman
Keyword(s):  
Finite Elements ◽  
Residual Stresses ◽  
Finite Elements Method

A Design Guide for Estimating Speed Made Good for a Sailing Yacht

1981 ◽  
Author(s):  
Deborah W. Berman
Keyword(s):  
Numerical Data ◽  
Quantitative Information ◽  
Test Results ◽  
Standard Series ◽  
Hull Form ◽  
Design Guide ◽  
Current Design ◽  
Sailing Yacht ◽  
Pencil And Paper ◽  
Selection Of

This study develops a simplified comparative procedure for use in preliminary yacht design to predict Equilibrium sideforce, resistance, leeway angle and speed made good to windward for a canoe hull sailing yacht within specific form parameters on any of five standard series keels. These forces, angles and speeds are predicted for any yacht hull resembling one of nine models - ranging from light to medium-heavy length to displacement ratio - (190 to 351) - of the Delft Systematic Series for which there is numerical data. The forces are calculated at speed to length ratio of 1. 3 and heel angle of 30° to enable the designer to make use of existing comparative sail plan and rigging data. The five keels of varying aspect and area ratio, spanning current design practice, are part of a matrix developed at the Davidson Laboratory. In this paper, a canoe yacht hull form similar to Model 7 of the Delft Series is tank tested on 3 Standard Series keels and compared to results obtained from testing a 5.5 m hull, which is similar to Model 8, on the same keels. A prediction procedure is developed and checked against test results. A few Equations, selected values from included tabulations, a calculator, pencil and paper will yield quantitative information for the yacht designer in the selection of a keel for the hull of a sailing yacht.

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