Modally tuning (using an oscilloscope, shaker and amplifier) an 8-storey tower скачать в хорошем качестве

Modally tuning (using an oscilloscope, shaker and amplifier) an 8-storey tower

In this short (solo handheld) video, I demonstrate (one-handed!) how to tune mode shapes on a structure (our 8-storey Tower at UTS in the Dynamics and Mechanics of Solids Lab) using an oscilloscope with generator, an electrodynamic shaker and an amplifier. This video is mainly targeted at our undergraduate cohort completing the lab exercises in the 43018 Dynamics Systems and Control B subject but should also be applicable to any other inexperienced modal test engineer. In the video, we start with the natural frequencies determined from a modal analysis on the sister tower to this with a Siemens Simcenter Testlab Modal Impact and Analysis campaign. However, the tower in this video is deliberately different (2.5 mm rather than 3 mm RHS wall thickness)...so, it's natural frequencies are slightly lower. By slowly adjusting the frequency downwards from 26.7 and 74.2 Hz, I monitor the output from an accelerometer attached to the top of the tower for the maximum response. This allows me to determine the frequencies for the second and third bending mode of 25.2 and 70.3 Hz, respectively. Using my hands/fingers, I can feel the vibration along the length of the beam including identifying the nodal lines for the two shapes of which there are one and two respectively for these second and third modes. I don't note it in the video but, for the third mode at around 70 Hz, it's also possible to hear the sound of the vibration in the video recording when the camera is close to the tower!