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Modal Testing of Circulation Pipe

The modal testing experiment presented here is performed by one university laboratory using ModalVIEW software and National Instruments DSA hardware as the modal testing and analysis tool. The analysis result provides instructive guidance of their research on FEM model.

Experiment scenario

The testing object is a circulation piple structure:

To identify this complex structure, accurate modal analysis method of poly-reference, multiple DOF, global fitting is required. ModalVIEW modal analysis software provides advanced modal analysis method based on mode stabilization diagram to extract modes from poly-reference FRF measurements, which meet testing requirements. National Instruments PXI 1042Q chasis and 24-bit PXI module NI -4472 is used to guarantee the accurate measurement of weak vibration signal of measured points far away from excitation point. The scalability of NI DSA hardware also guarantees the investment of whole modal testing system.  

System configuration

In this modal testing experiment, the following software and hardware are used

1.ModalVIEW1.0 Software.

2.NI DSA System (Low noise chassis PXI-1042, 8 channel DSA module NI -4472)

3.Hammer (Lance LC1302) and Charge amplifier (Lance LC0106).

4.Accelerometer (Lance 501).

 Analysis results

Modal analysis for the structure is finished with ModalVIEW’s advanced mode estimation method based on mode stabilization diagramThe following figure shows the clear mode stabilization diagram from 72 measured FRF data.

The closely spaced modes can be selected from stabilization diagram. The real modes are kept with mathematical or faked modes being discarded. Part of the picked meaningful modes are listed in following table :


Frequency (Hz) Damping (%)
1 9.43881 0.098717
2 13.403 0.106244
3 26.9246 0.281118
4 30.6038 4.53613
5 35.9271 2.52589
6 50.8051 1.41646
7 55.4367 0.068801
8 75.2458 0.053388
9 116.026 0.10867
10 137.14 0.485719

Some mode shapes are displayed as following :

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Last updated April 28th, 2018