Modal Modeling of Micro-Machining Center

2012 ◽  
Author(s):  
Marcin Chodźko ◽  
Krzysztof Marchelek
Keyword(s):  
Machine Tool ◽  
Model Updating ◽  
Dynamic Properties ◽  
Modal Testing ◽  
Mode Shapes ◽  
Experimental Investigations ◽  
Micro Machining ◽  
Machining Center ◽  
Modal Model ◽  
The Impact

Modeling of dynamic properties of machine tools has a significant influence on improvement of its construction. This process is extremely important when a new construction of machine tool is under development. Experimental modal analysis provides information about frequency bandwidths with significant amplitudes of resonances, damping values and mode shapes. This information can be used in FEM model updating, stability prediction or finding weak elements of the machine tool structure as well. In the paper the modal model of prototype of the micro machining center is presented. Polymax algorithm was used to estimate the poles (frequency, damping) of modal model and modal shapes. Modal model was built on the basis of the impact test results. Methodology of conducted experimental test is presented. Tested machine tool was made of different materials (steel, aluminum, stone and others) which causes difficulties during experimental investigations. In the construction different types of guideways were implemented — rolling, slide and pneumatic ones. Maximum rotational speed of the tool is about 100 000 rev/min, so the frequency range where poles of modal model are estimated is wide (high frequencies of excitation during machining). Weight of sensors used during testing is an important issue due to a low mass of the structure. Also the excitation of the structure is troublesome because of vulnerability of precise guideways and forces sensors used in machine tool construction. Validation of the modal model is also presented in the paper and practical problems of modal testing are discussed.

Experimental Modal Testing of the Elastic Tube Bundle

2013 ◽  
Vol 718-720 ◽  
pp. 1816-1819
Author(s):  
Ji Zhou Zheng ◽  
Jia Lin Hou ◽  
Yan Zhang
Keyword(s):  
Complex Shape ◽  
Tube Bundle ◽  
Dynamic Properties ◽  
Elastic Tube ◽  
Modal Testing ◽  
Mode Shapes ◽  
Constraint Condition ◽  
Heat Transfer Efficiency ◽  
Reduce Energy Consumption ◽  
Experimental Modal Testing

The elastic tube bundle is a new-style heat exchange element that can enhance heat transfer efficiency and reduce energy consumption. It is difficult to obtain exact analytical solutions because of the complex shape and constraint condition. An experimental modal testing technique is applied to get the dynamic properties. Some issues to which one should pay attention during the experiment are emphasized. Natural frequencies and mode shapes are identified from the test and compared to numerical results. Agreement is found for most frequencies of interest. But, some discrepancies exist for the vibration in-plane due to the inevitable operation error.

scholarly journals Parameter identification for a point-supported cross laminated timber slab based on experimental and numerical modal analysis

2020 ◽  
Author(s):  
Michael Kawrza ◽  
Thomas Furtmüller ◽  
Christoph Adam ◽  
Roland Maderebner
Keyword(s):  
Modal Analysis ◽  
Model Updating ◽  
Dynamic Properties ◽  
Element Model ◽  
Mode Shapes ◽  
Cross Laminated Timber ◽  
Numerical Studies ◽  
Robust Parameter ◽  
Updating Procedure ◽  
Sensor Positions

AbstractIn this paper, the dynamic properties of a point-supported cross-laminated timber slab are studied in order to determine the elastic material parameters on this basis. A detailed experimental modal analysis of the slab with dimensions 16.0 m x 11.0 m is performed, and seven modes including the natural frequencies, damping ratios and mode shape components at 651 sensor positions are identified. The found mode shapes are complex due to environmental influences that occurred during the two-day measurement campaign. This error is corrected by eliminating these influences. A finite element model of the slab is presented, whose parameters in terms of material properties and boundary conditions are determined by a model updating procedure. Based on the modal properties of the seven experimentally identified modes, an accurate and robust parameter set is obtained, which can be used in further numerical studies of the considered CLT to check serviceability limit criteria.

scholarly journals Rotor Model Updating and Validation for an Active Magnetic Bearing Based High-Speed Machining Spindle

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
Adam C. Wroblewski ◽  
Jerzy T. Sawicki ◽  
Alexander H. Pesch
Keyword(s):  
Transfer Functions ◽  
Model Updating ◽  
Dynamic Properties ◽  
Magnetic Bearing ◽  
Mode Shapes ◽  
Model Parameters ◽  
Successful Implementation ◽  
Fe Model ◽  
Rotor Model ◽  
Machining Spindle

This paper presents an experimentally driven model updating approach to address the dynamic inaccuracy of the nominal finite element (FE) rotor model of a machining spindle supported on active magnetic bearings. Modeling error is minimized through the application of a numerical optimization algorithm to adjust appropriately selected FE model parameters. Minimizing the error of both resonance and antiresonance frequencies simultaneously accounts for rotor natural frequencies as well as for their mode shapes. Antiresonance frequencies, which are shown to heavily influence the model’s dynamic properties, are commonly disregarded in structural modeling. Evaluation of the updated rotor model is performed through comparison of transfer functions measured at the cutting tool plane, which are independent of the experimental transfer function data used in model updating procedures. Final model validation is carried out with successful implementation of robust controller, which substantiates the effectiveness of the model updating methodology for model correction.

scholarly journals Damage Detection in Structures – Examples

2019 ◽  
Author(s):  
Ivan Duvnjak ◽  
Domagoj Damjanović ◽  
Natalia Sabourova ◽  
Niklas Grip ◽  
Ulf Ohlsson ◽  
...  
Keyword(s):  
Damage Detection ◽  
Damage Assessment ◽  
Model Updating ◽  
Dynamic Properties ◽  
Element Model ◽  
Mode Shapes ◽  
Modal Shape ◽  
New Methods ◽  
Before And After ◽  
Pros And Cons

<p>Damage assessment of structures includes estimation of location and severity of damage. Quite often it is done by using changes of dynamic properties, such as natural frequencies, mode shapes and damping ratios, determined on undamaged and damaged structures. The basic principle is to use dynamic properties of a structure as indicators of any change of its stiffness and/or mass. In this paper, two new methods for damage detection are presented and compared. The first method is based on comparison of normalised modal shape vectors determined before and after damage. The second method uses so-called &#119897;l-norm regularized finite element model updating. Some important properties of these methods are demonstrated using simulations on a Kirchhoff plate. The pros and cons of the two methods are discussed. Unique aspects of the methods are highlighted.</p>

scholarly journals Rigid Finite Element Method in Modeling Composite Steel-Polymer Concrete Machine Tool Frames

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3151 ◽  
Author(s):  
Paweł Dunaj ◽  
Krzysztof Marchelek ◽  
Stefan Berczyński ◽  
Berkay Mizrak
Keyword(s):  
Finite Element ◽  
Machine Tool ◽  
Experimental Verification ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
High Accuracy ◽  
Mode Shapes ◽  
Polymer Concrete ◽  
Beam Model ◽  
Low Dimensional

At the stage of designing a special machine tool, it is necessary to analyze many variants of structural solutions of frames and load-bearing systems and to choose the best solution in terms of dynamic properties, in particular considering its resistance to chatter. For this reason, it is preferred to adopt a low-dimensional calculation model, which allows the user to reduce the necessary calculation time while maintaining a high accuracy. The paper presents the methodology of modeling the natural frequencies, mode shapes, and receptance functions of machine tool steel welded frames filled with strongly heterogenous polymer concrete, using low-dimensional models developed by the rigid finite elements method (RigFEM). In the presented study, a RigFEM model of a simple steel beam filled with polymer concrete and a frame composed of such beams were built. Then, the dynamic properties obtained on the basis of the developed RigFEM models were compared with the experimental results and the 1D and 3D finite element models (FEM) in terms of accuracy and dimensionality. As a result of the experimental verification, the full structural compliance of the RigFEM models (for beam and frame) was obtained, which was manifested by the agreement of the mode shapes. Additionally, experimental verification showed a high accuracy of the RigFEM models, obtaining for the beam model a relative error for natural frequencies of less than 4% and on average 2.2%, and for the frame model at a level not exceeding 11% and on average 5.5%. Comparing the RigFEM and FEM models, it was found that the RigFEM models have a slightly worse accuracy, with a dimensionality significantly reduced by 95% for the beam and 99.8% for the frame.

scholarly journals Identification of Historical Veziragasi Aqueduct Using the Operational Modal Analysis

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
E. Ercan ◽  
A. Nuhoglu
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Model Updating ◽  
Dynamic Properties ◽  
Dynamic Test ◽  
Element Model ◽  
Operational Modal Analysis ◽  
Modal Identification ◽  
Ambient Vibration ◽  
Mode Shapes

This paper describes the results of a model updating study conducted on a historical aqueduct, called Veziragasi, in Turkey. The output-only modal identification results obtained from ambient vibration measurements of the structure were used to update a finite element model of the structure. For the purposes of developing a solid model of the structure, the dimensions of the structure, defects, and material degradations in the structure were determined in detail by making a measurement survey. For evaluation of the material properties of the structure, nondestructive and destructive testing methods were applied. The modal analysis of the structure was calculated by FEM. Then, a nondestructive dynamic test as well as operational modal analysis was carried out and dynamic properties were extracted. The natural frequencies and corresponding mode shapes were determined from both theoretical and experimental modal analyses and compared with each other. A good harmony was attained between mode shapes, but there were some differences between natural frequencies. The sources of the differences were introduced and the FEM model was updated by changing material parameters and boundary conditions. Finally, the real analytical model of the aqueduct was put forward and the results were discussed.

Prediction Capabilities of Damped Updated Finite Element Models

2011 ◽  
Author(s):  
Vikas Arora
Keyword(s):  
Finite Element ◽  
Model Updating ◽  
Dynamic Properties ◽  
Detailed Comparison ◽  
Element Model ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Complex Frequency ◽  
Structural Modifications ◽  
The Finite Element Model

Model updating techniques are used to correct the finite element model of a structure using experimental data such that the updated model more correctly describes the dynamic properties of the structure. One of the applications of such an updated model is to predict the effects of making modifications to the structure. These modifications may be imposed by design alterations for operating reasons. Most of the model updating techniques neglect damping and so these updated models can’t be used for accurate prediction of complex frequency response functions (FRFs) and complex mode shapes. In this paper, a detailed comparison of prediction capabilities of parameter-based and non parameter-based damped updated methods for structural modifications is done. The suitability of paramter-based and non parameter-based damped updated models for predicting the effects of structural modifications is evaluated by laboratory experiment for the case of an F-shape test structure. It is concluded that parameter-based damped updated models are likely to perform better in predicting the effects of structural modifications.

scholarly journals Experimental Modal Analysis of Business Jet Fuselage Tail Section Sub-Assemblies

2020 ◽  
Author(s):  
Ian A. Donaldson ◽  
Chris K. Mechefske
Keyword(s):  
Modal Analysis ◽  
Computational Models ◽  
Natural Frequencies ◽  
Model Updating ◽  
Experimental Modal Analysis ◽  
Experimental Results ◽  
Modal Testing ◽  
Experimental Methodology ◽  
Mode Shapes ◽  
Business Jet

Abstract Experimental modal testing is a technique through which the dynamic response of a system can be found. Parameters such as the natural frequencies and mode shapes of a system can be extracted through experimentation, and these results can be used to confirm computational models and guide structural improvements. This paper provides an overview of experimental modal analysis performed on two aircraft fuselage half scale subassemblies, with the use of shaker excitation. The experimental methodology including the construction of each structure, data acquisition parameters, and validity checks, is presented in detail. Linearity and repeatability checks were used to validate the testing methodology and increase the level of confidence in the experimental results. The experimental natural frequencies were correlated with the computational results, and recommendations were made. The experimental results presented in this work provide a basis for computational model updating work to be considered in future work.

scholarly journals Model Updating and Global Eigenvalue Analysis of a Tie-Bolt Rotor Using Zero-Length Contact Elements under Different Preloads

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Pu Li ◽  
Qi Yuan
Keyword(s):  
Model Updating ◽  
Contact Stiffness ◽  
Great Influence ◽  
Modal Testing ◽  
Linear Spring ◽  
Modal Behavior ◽  
Stiffness And Damping ◽  
The Impact ◽  
Contact Parameters ◽  
Rotor Model

Tie-bolt rotors are composed of several disks fastened by tie bolts where contact properties have a great influence on the modal behavior. In this work, a linear spring-damper element is used to consider the contact stiffness and damping in a tie-bolt rotor. A tie-bolt rotor model is developed using the beam element and the zero-length contact element. Experimental modal testing is performed under different preloads of tie bolts. Model updating is carried out to tune the contact parameters using the Particle Swarm Optimization algorithm. Furthermore, a global eigenvalue evaluation is carried out to demonstrate the impact of the lumped spring-damper element on the modal results. Results show that a larger pretension reduces the influence of contact damping on modal parameters. Compared to antisymmetric modes, symmetric modes are more sensitive to the change of contact damping.

Dynamic Characteristics of a Machine Tool at Working Positions in Operating Test

2011 ◽  
Author(s):  
Huimin Dong ◽  
Yang Tan ◽  
Delun Wang ◽  
Yali Ma
Keyword(s):  
Machine Tool ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Dynamic Properties ◽  
Vibration Energy ◽  
Testing Method ◽  
Spring Element ◽  
Machining Center ◽  
Brick Element ◽  
Stiffness And Damping

A machine tool is an assembly structure fitted by some moveable substructures, which the relative motion between the substructures creates normal and limit operating positions. Along with the substructures moving, the distributions of masses, stiffness and damping of the machine in space vary, leading to variety of structure distributions and dynamic properties. For exploring the dynamic properties distributions of machine tools, this paper presents a testing method under practical operational excitations, which is under operating excitations from remaining unbalanced value in the spindle, and collecting vibration signals of time and frequency at the spindle foreside at working positions. To identify resonance characteristics, a judging matrix is established by comparing vibration energy and vibration amplitude at 1st octave. By this method, MDH50 active pole horizontal machining center is tested, and the dynamic characteristics is determined. It reveals that dynamic characteristics of resonance come from the substructure independent resonance and their superposition in operating excitation. For verifying this result, FEA is conducted, in which 20 nodes brick element and spring element are applied to build the model entities and interfaces. The analysis result by FEM is consistent to the testing results. The research provides foundation for how setting up machining programs to avoid the resonance vibration of the machine in the operating.

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