Modal Analysis of Airplane Model Using EDM Modal

Analyzing the modal parameters of a structure is crucial in optimizing the mechanical properties of the test object. The natural frequencies, damping and mode shapes of the unit under test help in adjusting the design of the test structure which ultimately improves the structural behavior of the test unit.

Multi-Resolution Spectrum Analysis in Modal Testing

The latest 8.1 release of the Crystal Instrument’s EDM Modal software features multi-Resolution spectrum technology implemented into the MIMO FRF testing suite. Multiple passes of FFT yield a much finer resolution in the lower frequency region. This provides the advantage of a better estimation of the quality factor (or damping) and the amplitude of the frequency response functions at the resonant frequencies.

Simplify the User Interface and Manage Different Levels of Users

EDM’s Account Management program controls the accessibility of features from different users. This provides a structure for managing the privileges for different groups of users. The Account Manager can be used to prevent lower-level users from adjusting parameters or display settings. It also allows users to customize the toolbars for a simplified user interface. By hiding certain features, the UI can be made much easier to use.

Poly-X, the Poly-reference LSCF Implementation and Experiment

Abstract
A poly-reference least-square method for modal parameter identification of a system in frequency-domain is discussed and implemented. It can also be considered as a multi-reference frequency-domain implementation of the recognized time-domain based Least-Squares Complex Exponential (LSCE) estimator. The main advantages of the Poly-reference Least-Squares Complex Frequency-domain estimator (p-LSCF) are its capabilities of handling high system orders and high modal density. The stability diagram is much cleaner which makes the selection of system poles easier. Other advantages are lower computational times and the ability to handle multiple references. The Poly-X is Crystal Instruments’ version of p-LSCF, which is included in the EDM Modal software package. A MIMO FRF experimental test is carried out to demonstrate these advantages.

Vibration Visualization

The EDM Vibration Visualization feature is available in all modules of EDM software (VCS, DSA and Modal). This option provides fast and efficient structural model generation and full 3D visualization of the online vibration pattern on the structure under test

Modal Testing Using the CoCo-90X

Studying the modal properties of the structure under test is important to optimize the design of the test structure and to improve the NVH characteristics. Finite Element Analysis is widely used to obtain the mechanical properties of different objects. However, it is not only difficult to replicate the exact environmental constraints and boundary conditions but also challenging to obtain the damping ratios of the different modes. Experimental modal analysis not only helps in solving these issues but can also help in validating the results of the finite element model.

Hammer Impact Test Considerations

Roving excitation or response? Uni-ax or Tri-ax? SIMO or MIMO?

A modal impact hammer test is broadly classified between two types: roving hammer and roving response. Each method has its own pros and cons.