Animating Natural Frequencies
Learn more about how to view your model oscillating at one of its natural frequencies:
About Animating Natural Frequencies
The Linear Modes Controls command lets you view your model oscillating at one of its natural frequencies. It cycles through the model deformation starting from the operating point of the requested natural frequency of the eigensolution. You can also see the effect of the damping on the model and display a table and plot of modes and frequencies.
When you perform a linear simulation of your model using Adams Linear, Adams Solver linearizes the model at an operating point you specify and calculates the eigenvalues and eigenvectors. Adams View then uses the information to display the animated deformed shape as predicted from the eigensolution. Because the linear solution eigenvectors are normalized, you can specify what the maximum amount the animated deformed shape should translate or rotate to get a meaningful animation or recognizable shape.
The animation frames correspond to a picture of the model interpolated between the maximum deformation in the positive and negative directions. The animation then cycles through the deformation of the model mode shape, from undeformed, to maximum deformed, to negative maximum deformed, and finally to the undeformed shape. This deformation is about the operating point of the requested natural mode of the eigensolution.
You control the number of frames per cycle and the number of cycles in an animation. Adams View performs the interpolation between the frames using trigonometric functions; therefore, the frames tend to be segregated at the maximum deformation in the positive and negative directions.
You can only animate periodic and aperiodic eigenmodes (that is, modes with an imaginary component of the eigenvalue = 0). However, when animating aperiodic modes, Adams View warns you that the node has no oscillatory motion.
Performing an Animation of Natural Frequencies
To animate the natural frequencies of your model:
1. If necessary, run a Linear simulation.
2. From the Review menu, select Linear Modes Control.
The Linear Modes Controls dialog box appears. It loads the eigensolution associated with the last linear simulation you ran.
3. If desired, enter the name of an eigensolution in an existing analysis and set the view for the animation. The eigensolution must be in an existing analysis that is associated with the current model.
4. If desired, set the option menu to define the mode to be used to calculate the deformation of the model. Set it to either:
♦Mode and enter the number of the mode to be used.
♦Frequency and enter the frequency of the mode.
If you specify the frequency, Adams View uses the mode closest to the specified frequency. If you specify neither the mode nor the frequency, Adams View deforms the model using the first mode.
Tip: | To view the modes in the eigensolution to see which you should use, see Plotting and Viewing Modes and Frequencies |
5. Set up the number of frames per cycle and number of cycles:
Note: | A full cycle goes from undeformed, to maximum positive displacement, back to undeformed, then to maximum displacement in the negative direction, and finally back to undeformed. |
♦Frames Per Cycles - Enter the number of frames to be displayed for each cycle. Adams View performs the interpolation between the frames using trigonometric functions; therefore, the frames tend to be segregated at the maximum deformation in the positive and negative directions.
♦Number of Cycles - Parameter used to specify the number of complete cycles to animate.
6. Select any of the following to set up the animation:
♦Show time decay - Specifies whether the amplitudes of the deformations are to remain constant or decay due to the damping factor calculated in the eigensolution.
♦Show trail - Shows the path, or trail, of parts from one frame to another. Showing the trail is useful in showing the relationship of the model parts between frames but often obscures the view of the motion.
♦Show undeformed - Specifies whether the undeformed model is to be displayed with the deformed shape superimposed on top of it. If you select Show undeformed, select a color for the undeformed model. If you do not specify a color, Adams View displays the undeformed model using the same color as the deformed mode.
♦Show icons - Turns on the display icons during an animation.
7. Set the maximum amount parts will translate or rotate from their undeformed position. If you do not specify maximum amounts, Adams View translates parts no more than 20 percent of model size and 20 degrees.
8. Select the Animate tool 
.
. Plotting and Viewing Modes and Frequencies
Plot the eigenvalues or view a table of eigenvalues in the Information window.
Plotting Eigenvalues
You can plot the real eigenvalues against the imaginary eigenvalues.
To plot eigenvalues:
1. At the bottom of the Linear Modes Controls dialog box, select Plot.
A Linear Modes Eigenvalue Plot window appears.
2. After viewing the plot, select Close and Delete Plot.
To save the plot:
1. Select Save Plot.
2. Enter a name for the plot.
3. Select Close and Save Plot.
Viewing Eigenvalues
You can display information about all an eigensolution's predicted eigenvalues in the Information window. Once you display the information in the Information window, you can save it to a file.
The information includes:
■Mode number - Sequential number of the mode that was predicted by the eigen solution.
■Frequency - Natural frequency corresponding to the mode.
■Damping - Damping ratio for the mode (the log decrement is another way to represent this quantity).
■Eigenvalues - List the real and imaginary part of the eigenvalue.
To view eigenvalues:
1. At the bottom of the Linear Modes Controls dialog box, select Table.
The Information window appears.
2. After viewing the information, select Close.