Relationship Between Improved Inverse Eigensensitivity and FRF Sensitivity Methods for Analytical Model Updating

1997 ◽  
Vol 119 (3) ◽  
pp. 354-362 ◽  
Author(s):  
R. M. Lin ◽  
M. K. Lim
Keyword(s):  
Analytical Model ◽  
Model Updating ◽  
Analytical Models ◽  
Practical Application ◽  
Solution Uniqueness ◽  
Mathematical Relationship ◽  
Practical Applications ◽  
Advantages And Disadvantages ◽  
Model Improvement ◽  
Sensitivity Method

Improved inverse eigensensitivity method and improved frequency response function (FRF) sensitivity method developed for analytical model updating have become increasingly popular among other methods and have been successfully applied to the practice of analytical model improvement. This paper examines the mathematical relationship between these two powerful methods for updating analytical models of undamped systems with objectives of demonstrating the advantages and disadvantages of each method as well as their specific practical application conditions. The problem of solution uniqueness associated with these methods is addressed. Computational considerations regarding the practical application of the methods are discussed. Numerical simulations are given to demonstrate the practical applications of these methods.

Updating of Non-Conservative Systems Using Inverse Methods

1997 ◽  
Author(s):  
Ladislav Starek ◽  
Milos Musil ◽  
Daniel J. Inman
Keyword(s):  
Analytical Model ◽  
Degrees Of Freedom ◽  
Ad Hoc ◽  
Natural Frequencies ◽  
Eigenvalue Problems ◽  
Model Updating ◽  
Analytical Models ◽  
Mode Shapes ◽  
Element Analysis ◽  
Modal Data

Abstract Several incompatibilities exist between analytical models and experimentally obtained data for many systems. In particular finite element analysis (FEA) modeling often produces analytical modal data that does not agree with measured modal data from experimental modal analysis (EMA). These two methods account for the majority of activity in vibration modeling used in industry. The existence of these discrepancies has spanned the discipline of model updating as summarized in the review articles by Inman (1990), Imregun (1991), and Friswell (1995). In this situation the analytical model is characterized by a large number of degrees of freedom (and hence modes), ad hoc damping mechanisms and real eigenvectors (mode shapes). The FEM model produces a mass, damping and stiffness matrix which is numerically solved for modal data consisting of natural frequencies, mode shapes and damping ratios. Common practice is to compare this analytically generated modal data with natural frequencies, mode shapes and damping ratios obtained from EMA. The EMA data is characterized by a small number of modes, incomplete and complex mode shapes and non proportional damping. It is very common in practice for this experimentally obtained modal data to be in minor disagreement with the analytically derived modal data. The point of view taken is that the analytical model is in error and must be refined or corrected based on experimented data. The approach proposed here is to use the results of inverse eigenvalue problems to develop methods for model updating for damped systems. The inverse problem has been addressed by Lancaster and Maroulas (1987), Starek and Inman (1992,1993,1994,1997) and is summarized for undamped systems in the text by Gladwell (1986). There are many sophisticated model updating methods available. The purpose of this paper is to introduce using inverse eigenvalues calculated as a possible approach to solving the model updating problem. The approach is new and as such many of the practical and important issues of noise, incomplete data, etc. are not yet resolved. Hence, the method introduced here is only useful for low order lumped parameter models of the type used for machines rather than structures. In particular, it will be assumed that the entries and geometry of the lumped components is also known.

Testing Analytical Models Using Archival or Experimental Methods

2012 ◽  
Vol 27 (1) ◽  
pp. 129-139 ◽  
Author(s):  
Shane S. Dikolli ◽  
John H. Evans ◽  
Jeffrey Hales ◽  
Michal Matejka ◽  
Donald V. Moser ◽  
...  
Keyword(s):  
Experimental Data ◽  
Empirical Research ◽  
Analytical Model ◽  
Empirical Data ◽  
Review Process ◽  
Experimental Methods ◽  
Analytical Models ◽  
Journal Review ◽  
Advantages And Disadvantages ◽  
Jel Classifications

SYNOPSIS Analytical models can quite naturally complement empirical data, whether archival or experimental. This article begins by discussing the advantages and disadvantages of combining an analytical model with archival or experimental data in a single study. We next describe how models are typically used in empirical research and discuss when including an analytical model is more versus less useful. Finally, we offer examples of more and less successful combinations of analytical models and empirical data, along with a brief discussion of how such studies are likely to fare in the journal review process. JEL Classifications: C02; C51; C99.

Improved Inverse Eigensensitivity Method for Structural Analytical Model Updating

1995 ◽  
Vol 117 (2) ◽  
pp. 192-198 ◽  
Author(s):  
R. M. Lin ◽  
M. K. Lim ◽  
H. Du
Keyword(s):  
Analytical Model ◽  
Model Updating ◽  
Element Model ◽  
Small Error ◽  
Analytical Models ◽  
Engineering Structures ◽  
Modal Data ◽  
Existing Problems ◽  
Practical Engineering ◽  
True Values

In order to update analytical models of practical engineering structures, inverse eigensensitivity method (IEM) has been developed. Though it has nowadays been widely accepted, the classical inverse eigensensitivity method does have some drawbacks such as the assumption of small error magnitudes and slow speed of convergence due to the fact that the sensitivity coefficients are calculated purely based on modal data of analytical model. In the present paper, an improved inverse eigensensitivity method, which avoids the existing problems of classical inverse eigensensitivity method, has been developed. The improved method employs both analytical and experimental modal data to calculate the required eigensensitivity coefficients which are very close to their true values. The method has been further extended to the case where measured coordinates are incomplete. Practical applicability of the method has been assessed by its application to the updating of the finite element model of a plane truss structure.

A Combined Analytical and Numerical Approach to Analyze Mud Motor Excited Vibrations in Drilling Systems

2015 ◽  
Author(s):  
Andreas Hohl ◽  
Carsten Hohl ◽  
Christian Herbig
Keyword(s):  
Finite Element ◽  
Analytical Model ◽  
Field Measurements ◽  
Element Model ◽  
Numerical Approach ◽  
Analytical Models ◽  
Finite Element Models ◽  
Beam Model ◽  
Direct Influence ◽  
Practical Applications

Severe vibrations in drillstrings and bottomhole assemblies can be caused by cutting forces at the bit or mass imbalances in downhole tools. One of the largest imbalances is related to the working principle of the so-called mud motor, which is an assembly of a rotor that is maintained by the stator. One of the design-related problems is how to minimize vibrations excited by the mud motor. Simulation tools using specialized finite element methods (FEM) are established to model the mechanical behavior of the structure. Although finite element models are useful for estimating rotor dynamic behavior and dynamic stresses of entire drilling systems they do not give direct insight how parameters affect amplitudes and stresses. Analytical models show the direct influence of parameters and give qualitative solutions of design related decisions. However these models do not provide quantitative numbers for complicated geometries. An analytical beam model of the mud motor is derived to calculate the vibrational amplitudes and capture basic dynamic effects. The model shows the direct influence of parameters of the mud motor related to the geometry, material properties and fluid properties. The analytical model is compared to the corresponding finite element model. Vibrational amplitudes are discussed for different modes and parameter changes. Finite element models of the entire drilling system are used to verify the findings from the analytical model using practical applications. The results are compared to time domain and statistical data from laboratory and field measurements.

An Energy Error Estimation Method for Improving Analytical Models Using Vibration Modal Test Data

1995 ◽  
Vol 209 (2) ◽  
pp. 97-105 ◽  
Author(s):  
S Guo ◽  
N G Hemingway
Keyword(s):  
Analytical Model ◽  
Error Estimation ◽  
Test Data ◽  
Dynamic Models ◽  
Estimation Method ◽  
Analytical Models ◽  
Original Matrix ◽  
Energy Error ◽  
Modal Test ◽  
Model Improvement

When improving analytical dynamic models using modal test data, correct localization of the poorly modelled areas in the analytical model is essential for ensuring the accuracy of the model improvement obtained. In this paper, a method referred to as the energy error estimation (EEE) method is proposed. Firstly, this method is capable of effectively distinguishing the correctly modelled mass and stiffness elements from those poorly modelled regions by using a limited number of test modes. This results in an accurate localization of the analytical modelling errors. Secondly, a set of correction factors can be obtained for improving those elements that are identified as having been poorly modelled. The improved analytical model will also retain its original matrix configuration, size and physical explanation, which is desirable. In order to verify the efficiency and accuracy of this proposed method, beam examples using both simulated and experimental modal test data are demonstrated. Excellent model improvement is shown in these examples.

Recent Patents on the Angular Contact Ball Bearing of High-Speed Motorized Spindle

2020 ◽  
Vol 13 ◽  
Author(s):  
Yudong Bao ◽  
Linkai Wu ◽  
Yanling Zhao ◽  
Chengyi Pan
Keyword(s):  
High Speed ◽  
Ball Bearing ◽  
Rapid Development ◽  
Ceramic Materials ◽  
Development Trend ◽  
Numerical Control ◽  
Angular Contact Ball Bearing ◽  
Practical Applications ◽  
High Speed Cutting ◽  
Advantages And Disadvantages

Background:: Angular contact ball bearings are the most popular bearing type used in the high speed spindle for machining centers, The performance of the bearing directly affects the machining efficiency of the machine tool, Obtaining a higher value is the direction of its research and development. Objective:: By analyzing the research achievements and patents of electric spindle angular contact bearings, summarizing the development trend provides a reference for the development of electric spindle bearings. Methods:: Through the analysis of the relevant technology of the electric spindle angular contact ball bearing, the advantages and disadvantages of the angular contact ball bearing are introduced, and the research results are combined with the patent analysis. Results:: With the rapid development of high-speed cutting and numerical control technology and the needs of practical applications, the spindle requires higher and higher speeds for bearings. In order to meet the requirements of use, it is necessary to improve the bearing performance by optimizing the structure size and improving the lubrication conditions. Meanwhile, reasonable processing and assembly methods will also have a beneficial effect on bearing performance. Conclusion:: With the continuous deepening of bearing technology research and the use of new structures and ceramic materials has made the bearing's limit speed repeatedly reach new highs. The future development trend of high-speed bearings for electric spindles is environmental protection, intelligence, high speed, high precision and long life.

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