scholarly journals Analysis of Stationary Random Responses for Non-Parametric Probabilistic Systems

2010 ◽  
Vol 17 (3) ◽  
pp. 305-315 ◽  
Author(s):  
Y. Zhao ◽  
Y.H. Zhang ◽  
J.H. Lin ◽  
W.P. Howson ◽  
F.W. Williams
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Physical Structure ◽  
Dynamic Responses ◽  
Response Analysis ◽  
Random Matrix Model ◽  
Stiffness Matrices ◽  
Element Technique ◽  
Non Parametric

The move from conceptual design, through fabrication to observation and measurement on the resulting physical structure is fraught with uncertainty. This, together with the necessary simplifications inherent when using the finite element technique, makes the development of a predictive model for the physical structure sufficiently approximate that the use of random structural models is often to be preferred. In this paper, the random uncertainties of the mass, damping and stiffness matrices in a finite element model are replaced by random matrices, and a highly efficient pseudo excitation method for the dynamic response analysis of non-parametric probability systems subjected to stationary random loads is developed. A numerical example shows that the dynamic responses calculated using a conventional (mean) finite element model may be quite different from those based on a random matrix model. For precise fabrication, the uncertainties of models cannot be ignored and the proposed method should be useful in the analysis of such problems.

scholarly journals Design optimization of vehicle asynchronous motors based on fractional harmonic response analysis

2021 ◽  
Vol 12 (1) ◽  
pp. 689-700
Author(s):  
Ao Lei ◽  
Chuan-Xue Song ◽  
Yu-Long Lei ◽  
Yao Fu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Natural Frequency ◽  
Asynchronous Motor ◽  
Element Model ◽  
Design Parameters ◽  
Response Analysis ◽  
Harmonic Response ◽  
First Order ◽  
Harmonic Response Analysis

Abstract. To make vehicles more reliable and efficient, many researchers have tried to improve the rotor performance. Although certain achievements have been made, the previous finite element model did not reflect the historical process of the motor rotor well, and the rigidity and mass in rotor optimization are less discussed together. This paper firstly introduces fractional order into a finite element model to conduct the harmonic response analysis. Then, we propose an optimal design framework of a rotor. In the framework, objective functions of rigidity and mass are defined, and the relationship between high rigidity and the first-order frequency is discussed. In order to find the optimal values, an accelerated optimization method based on response surface (ARSO) is proposed to find the suitable design parameters of rigidity and mass. Because the higher rigidity can be transformed into the first-order natural frequency by objective function, this paper analyzes the first-order frequency and mass of a motor rotor in the experiment. The results proved that not only is the fractional model effective, but also the ARSO can optimize the rotor structure. The first-order natural frequency of asynchronous motor rotor is increased by 11.2 %, and the mass is reduced by 13.8 %, which can realize high stiffness and light mass of asynchronous motor rotors.

Random Vibration Analysis of a Printed Wiring Board with Electronic Components

1991 ◽  
Vol 34 (1) ◽  
pp. 25-31
Author(s):  
Jack Roberts ◽  
Debra Stillo
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Random Vibration ◽  
Element Model ◽  
Printed Wiring Board ◽  
Electronic Components ◽  
Bending Stresses ◽  
Wiring Board ◽  
Element Technique ◽  
The Finite Element Model

A printed wiring board (PWB) with electronic components has been modeled using the finite element technique and compared with the same PWB experimentally tested in a chassis during a 2 hr random vibration test. Accelerometers were attached to the PWB in locations where nodes existed in the finite element model (FEM). The FEM predicted the first natural frequency to within 10 percent of the test results. Due to wedge locks that loosened during the test, the PWB accelerations in the finite element model and the test differed by as much as 40 percent. The ceramic capacitor on the PWB was modeled in detail with leads attached to the PWB to examine bending stresses in the leads. During the 2 hr test there were no failures for those leads with adequate solder joints. A failure did occur, however, on a lead with insufficient solder. A fatigue analysis of the FEM lead bending stresses indicated lead failure if no solder was used, whereas no failures were predicted for properly soldered leads.

Frequency Window Implementation of Adaptive Multi-Level Substructuring

1998 ◽  
Vol 120 (2) ◽  
pp. 409-418 ◽  
Author(s):  
J. K. Bennighof ◽  
M. F. Kaplan
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Center Frequency ◽  
Response Analysis ◽  
Adaptive Procedure ◽  
Multi Level ◽  
Frequency Window ◽  
Efficient Representation ◽  
Multiple Levels

Adaptive multi-level substructuring (AMLS) is a method for reducing the order of a complex structure’s finite element model by orders of magnitude, while ensuring that the accuracy available from the original model is preserved. A structure’s finite element model is transformed to a much more efficient representation in terms of approximate vibration modes for substructures on multiple levels. An adaptive procedure constructs an optimal model for satisfying a user-specified error tolerance, by determining which modes should be included in the model. In this paper, a frequency window implementation of AMLS is developed, in which frequency response analysis can be done over a frequency window at little additional cost beyond that of the center frequency solution. A numerical example is presented.

NUMERICAL ANALYSIS OF TYMPANOSCLEROSIS AND TREATMENT EFFECT

2014 ◽  
Vol 14 (04) ◽  
pp. 1450051 ◽  
Author(s):  
WENJUAN YAO ◽  
JIANWEI MA ◽  
XUEMEI LUO ◽  
BOTE LUO
Keyword(s):  
Finite Element ◽  
Middle Ear ◽  
Element Model ◽  
Response Analysis ◽  
Research Perspective ◽  
Stapes Footplate ◽  
Ct Data ◽  
Element Technique ◽  
New Research ◽  
The Right

Tympanosclerosis is a typical middle ear disease, which is one of the main causes of conduction deafness. We investigate the effects of tympanosclerosis and lesion excision on sound transmission of the human ear by using finite element technique. Based on CT scan images from Zhongshan Hospital of Fudan University on the normal human middle ear, numerical values of the CT scans were obtained by further processing of the images using a self-compiled program. The CT data of the right ear from a healthy volunteer were digitalized and imported into PATRAN software to reconstruct the finite element model of the ear by a self-compiling program. A frequency response analysis was made for the model, and comparative analysis was made between the calculated results and experimental data, which validated the model in this paper. The results show that the sclerosis of the ligaments and tensor muscle in the middle ear caused by force on the ossicles is larger than the normal ear and the amplitude of the stapes footplate is larger than the normal ear. This leads to a decrease of the final conductive hearing function. Furthermore, the excision of the stapes ligament and tensor tympani is good for the restoration of normal hearing. This paper provides new research perspective for clinical treatment.

Material Characterization for Dynamic Simulation of Non-Homogeneous Structural Members

2010 ◽  
Vol 449 ◽  
pp. 46-53
Author(s):  
J.A. Quintana-Rodríguez ◽  
J.F. Doyle ◽  
F.J. Carrión-Viramontes ◽  
Didier Samayoa-Ochoa ◽  
J. Alfredo López-López
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Dynamic Simulation ◽  
Structural Parameters ◽  
A Priori ◽  
Element Model ◽  
Dynamic Responses ◽  
Inertia Moment ◽  
Physical Density ◽  
Equivalent Properties

Generally, simulation of non-homogeneous materials requires a homogeneous representation with equivalent properties different from the constitutive elements. Determination of the equivalent properties for dynamic simulation is not always a direct and straightforward calculation, as they have to represent, not only the static reactions, but also the dynamic behavior, which depends on a more complex relation of the geometrical (area, inertia moment), mechanical (elastic modulus) and physical (density) properties. In this context, the Direct Sensitivity Method (DSM) is developed to calibrate structural parameters of a finite element model using a priori information with an inverse parameter identification scheme, where parameters are optimized through an error sensitivity function using experimental data with the dynamic responses of the model. Results demonstrate that parameters of materials can be calibrated efficiently from the DSM and that key aspects for this calibration are noise, sensitivity (structural and sensor), and the finite element model representation.

Frequency Window Implementation of Adaptive Multi-Level Substructuring

1995 ◽  
Author(s):  
Jeffrey K. Bennighof ◽  
Matthew F. Kaplan
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Center Frequency ◽  
Response Analysis ◽  
Adaptive Procedure ◽  
Multi Level ◽  
Frequency Window ◽  
Efficient Representation ◽  
Multiple Levels

Abstract Adaptive multi-level substructuring (AMLS) is a method for reducing the order of models of complex structures by orders of magnitude, while ensuring that the accuracy available from the original finite element model is preserved. A structure’s finite element model is transformed to a much more efficient representation in terms of approximate vibration modes for substructures on multiple levels. An adaptive procedure constructs an optimal model for satisfying a user-specified error tolerance, by determining which modes should be included in the model. In this paper, a frequency window implementation of AMLS is developed, in which frequency response analysis can be done over a frequency window at little additional cost beyond that of the solution at the center frequency. A numerical example is presented.

Dynamic Responses of Arch Dams Considering Different Reservoir Models

2011 ◽  
Vol 250-253 ◽  
pp. 3923-3926
Author(s):  
Shao Qing Hu ◽  
Bai Tao Sun
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Water Level ◽  
Element Model ◽  
Arch Dam ◽  
Dynamic Responses ◽  
Additional Mass ◽  
Mass Model ◽  
Arch Dams ◽  
Reservoir Models

In this paper, the dynamic responses of an arch dam in the case of normal water level and operating low water level were simulated by using additional mass model and incompressible finite element model for reservoir respectively. The results showed that the reservoir models have a great impact on dynamic response of arch dams. The maximum principle tensile stress using incompressible finite element model of fluid is less than that using additional mass model. With the depth of the reservoir water increasing, the hydrodynamic pressure acting ton the dam surface caused by earthquake force increased and the dynamic responses of dam also increased.

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