16 February 2018
- Last edited 16 February 2018
I'm glad to know that the data is as you said.
The only difference between your extraction and mine is that you picked your zero one time step away from mine. After deleting one cell, and shifting all cells up one, the two curves are aligned, and only off vertically by a constant of 9e-6 so I think you have done a good job isolating a section of data to use.
Location of Accelerometer on Cart
A cart with wheels rolls over bumps in the floor, which creates a transient vibration in the cart structure. The cart consists of a base where the wheels are attached, and a column with a component on top. One accelerometer is on the base and another accelerometer is under the component where it bolts to the column. The acceleration-time history is recorded as the wheels roll over bumps in the floor.
Take the wheels off the base and bolt the base to a servo-controlled shaker table. Play back the recorded acceleration-time history from the base accelerometer into the shaker table controller. The base, column and component will reproduce a similar transient vibration on the shaker table that was observed when the wheels rolled over the bumps in the floor.
Make an ANSYS model of the base, column and component structure but without wheels, and add a fixed support on the base where the accelerometer was mounted. Now use the base accelerometer data as an acceleration load on that model. The base, column and component will show a transient vibration like it had when the cart was on wheels.
But play back the acceleration-time history from the component accelerometer into the shaker table controller. It will not reproduce the transient vibrations that were observed in the base, column and component. Similarly, insert the acceleration data from the component accelerometer into the ANSYS model with the fixed support on the base, a similar transient will not be seen as was observed when the cart had wheels.
Now unbolt the component from the top of the column where the component accelerometer was mounted, and bolt that component onto the shaker table. Play back the acceleration-time history recorded by the component accelerometer and the component would experience a similar transient vibration that it saw when the cart rolled over the bumps in the floor.
But play back the acceleration-time history from the base accelerometer into to the shaker table and the component will not experience a similar transient as it saw when the wheels were rolling over bumps in the floor.
Make an ANSYS model of the component and add a fixed support to the component where it bolts to the column. Use the component accelerometer as the acceleration load for the ANSYS model of the component. The component model will show a similar transient that was obsvered as when the wheels rolled over the bumps.
Do you see how the location of the accelerometer determines what can be in the ANSYS model if you want to use that accelerometer time-history as an acceleration load to the model?
It seems to me that you want an accelerometer mounted to a stake in the ground to record the ground motion in order to use that data as an acceleration load to a structure that is mounted to the ground. The accelerometer mounted to the top of the structure is seeing the response of the struture to the ground motion, so it not ideal to use as an acceleration load for the ground motion.
A Seismograph instrument may be more appropriate than an accelerometer, since you are trying to record the seismic vibrations in the ground and use that to simulate vibrations in a structure that is built on the ground.