In general we perform bump/impact test to find natural frequency as rough test to prove if resonance problem exists. But however if we would like to see mode shape, several measurement points of transfer function/frequency response function between input force and vibration output is required. Modal analysis software is then used to curve fit the data and identify natural frequency, mode shape, and damping.
Motion amplification (MA) camera is a modern tool which is normally used for non-contact vibration measurement. During a vibration measurement training class conducted by Machinosis, we illustrated how to apply MA camera to do simple bump test on the rotor kit installed on a table to identify natural frequency and associated mode shape.
In the first video, the rotor kit is not running, motion amplification camera is used to record object motion when striking force applied. It clearly represents object motion and natural frequency as a consequence of striking force in vertical direction on the table.
In second video, the rotor kit is running at 2000 rpm, the motion amplification video clearly shows object motion and dominant frequencies, when striking force applied on the table.
These videos reveal two important information:
1. Natural Frequency : 18, 34 Hz
2. Mode shape: vertical movement of the table supporting the rotor kit (not rotor kit itself)
These information is normally acquired using vibration transducer(s), force hammer, vibration data collector, and modal analysis software to create object model and animation. In many cases, it is time consuming with conventional vibration measurement tools but this can be done quickly and effectively with MA camera.
From these examples, MA camera is alternative tool that help to provide the same information in short period of time.