Design and Dynamic Analysis of a Space Frame for Acoustic Measurements

Static and dynamic characteristics of a Space Frame were determined by using the Finite Element Method. Also experimental measurements were done on the manufactured frame resulting in the dynamic characteristics of the structure. Results from this Experimental Modal Analysis were compared with the results from FEM-calculations. Correlation between the models was obtained showing very good agreement between the FE-model and the manufactured Space Frame. Further, the FE-model was used to modify the manufactured frame so that the predetermined target values were fulfilled.


1. Notation
2. Introduction
2.1 Background
2.2 Project Description
2.2.1 Method and Restrictions
3 Frame Design
3.1 Frame Dimensions
4. Theories
4.1 Static Characteristics
4.1.1 Bending Stiffness
4.1.2 Torsional Stiffness
4.1.3 Stress Distribution
4.2 Dynamics
4.2.1 Multiple-Degree-of-Freedom (MDOF) system
4.2.2 Natural Frequencies and Mode Shapes
4.2.3 Strain Energy Distribution
4.3 Experimental Modal Analysis (EMA)
4.3.1 Multi-Input Multi-Output (MIMO) Analysis
4.4 Correlation
4.4.1 Modal Assurance Criterion (MAC)
5. Finite Element Model
5.1 Elements
5.1.1 Beam Elements
5.1.2 Shell Elements
5.1.3 Choice of Elements
5.2 Space Frame FE-model
5.2.1 Elements
5.2.2 Boundary Conditions
5.2.3 Type of Analysis
5.3 Results
5.3.1 Torsional Stiffness
5.3.2 Bending Stiffness
5.3.3 Normal Modes
5.3.4 Discussion of Results
6. Measurements
6.1 Measurement Set-up
6.2 Measurement Set-up Verification
6.3 Measurement Results
7. FE- and Test-model Correlation
7.1 Mode Pairing
7.2 Natural Frequencies
7.3 Conclusions
8. Redesign
8.1 Modifications
8.2 Results
9. Conclusions

Author: Tommi Paananen

Source: Blekinge Institute of Technology

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