Time series dual boundary element model for P and SV waves propagation in half-space

2021 ◽  
Vol 126 ◽  
pp. 93-107
Author(s):  
Bahman Ansari ◽  
Alireza Firoozfar
2017 ◽  
Vol 24 (s2) ◽  
pp. 103-110
Author(s):  
Zhengyao He ◽  
Qiang Shi ◽  
Shaoxuan Wu

Abstract In underwater unmanned vehicles, complex acoustic transducer arrays are always used to transmitting sound waves to detect and position underwater targets. Two methods of obtaining low-sidelobe transmitting beampatterns for acoustic transmitting arrays of underwater vehicles are investigated. The first method is the boundary element model optimization method which used the boundary element theory together with the optimization method to calculate the driving voltage weighting vector of the array. The second method is the measured receiving array manifold vector optimization method which used the measured receiving array manifold vectors and optimization method to calculate the weighting vector. Both methods can take into account the baffle effect and mutual interactions among elements of complex acoustic arrays. Computer simulation together with experiments are carried out for typical complex arrays. The results agree well and show that the two methods are both able to obtain a lower sidelobe transmitting beampattern than the conventional beamforming method, and the source level for each transmitting beam is maximized in constraint of the maximum driving voltage of array elements being constant. The effect of the second method performs even better than that of the first method, which is more suitable for practical application. The methods are very useful for the improvement of detecting and positioning capability of underwater unmanned vehicles.


1991 ◽  
Vol 113 (1) ◽  
pp. 93-101 ◽  
Author(s):  
S. M. Kulkarni ◽  
C. A. Rubin ◽  
G. T. Hahn

The present paper, describes a transient translating elasto-plastic thermo-mechanical finite element model to study 2-D frictional rolling contact. Frictional two-dimensional contact is simulated by repeatedly translating a non-uniform thermo-mechanical distribution across the surface of an elasto-plastic half space. The half space is represented by a two dimensional finite element mesh with appropriate boundaries. Calculations are for an elastic-perfectly plastic material and the selected thermo-physical properties are assumed to be temperature independent. The paper presents temperature variations, stress and plastic strain distributions and deformations. Residual tensile stresses are observed. The magnitude and depth of these stresses depends on 1) the temperature gradients and 2) the magnitudes of the normal and tangential tractions.


2010 ◽  
Vol 112 ◽  
pp. 83-92
Author(s):  
Alexandre Micol ◽  
Adrien Zéanh ◽  
Olivier Dalverny ◽  
Moussa Karama

This work studies the reliability of power electronic component in aeronautical environment to the ageing eect of the thermal cycling. The structure fatigue is sensitive to the process assembly conditions especially of the soldering process. To correclty evaluate the reliability of the power module, the identication of the solder behavior is one of the rst steps. Anand Model is here identied. Experimental test have to be established to evaluate the parameters of the law. A srt study is made to evaluate the indetiability of the law according to the dierent experimantal test. Then, the scatter of the parameters is evaluated in a context of time series. In the end, the scatter of the parameters is included in a nite element model to understand the inuence of this scatter on the evaluation of the number of cycle before failure.


1999 ◽  
Author(s):  
Michael Allen ◽  
Nickolas Vlahopoulos

Abstract In this paper an algorithm is developed for combining finite element analysis and boundary element techniques in order to compute the noise radiated from a panel subjected to boundary layer excitation. The excitation is presented in terms of the auto and cross power spectral densities of the fluctuating wall pressure. The structural finite element model for the panel is divided into a number of sub-panels. A uniform fluctuating pressure is applied as excitation on each sub-panel separately. The corresponding vibration is computed, and is utilized as excitation for an acoustic boundary element analysis. The acoustic response is computed at any data recovery point of interest. The relationships between the acoustic response and the pressure excitation applied at each particular sub-panel constitute a set of transfer functions. They are combined with the spectral densities of the excitation for computing the noise generated from the vibration of the panel subjected to the boundary layer excitation. The development presented in this paper has the potential of computing wind noise in automotive applications, or boundary layer noise in aircraft applications.


2014 ◽  
Vol 1040 ◽  
pp. 881-885 ◽  
Author(s):  
Leonid A. Igumnov ◽  
Svetlana Litvinchuk ◽  
Andrey Petrov ◽  
Alexander A. Belov

A direct approach of the boundary element method for treating 3-D boundary-value problems of poroelastodynamics is considered. Biot’s material model with four unknown base functions is used. Computational results for the surface responses of displacements and pore pressures as functions of a force acting on a half-space weakened by a cavity are presented.


Sign in / Sign up

Export Citation Format

Share Document