# Selecting an amplitude type to define

 Select ToolsAmplitudeCreate from the main menu bar to create an amplitude. For detailed information on amplitudes, see Amplitude Curves, and Specifying a spectrum.
 Related Topics Understanding the amplitude editors Entering tabular data In Other Guides Amplitude Curves
1. From the main menu bar, select ToolsAmplitudeCreate.

 Tip: You can also create an amplitude by clicking mouse button 3 on the Amplitudes container in the Model Tree or by clicking Create in the Amplitude Manager.

The Create Amplitude dialog box appears.

2. In the Name field, enter a name for the amplitude. For information on naming objects, see Using basic dialog box components.

3. Choose the Type of amplitude that you want to create:

• Choose Tabular to define the amplitude curve as a table of values at convenient points on the time scale. Abaqus interpolates linearly between these values, as needed. For more information, see Defining tabular data.

• Choose Equally spaced to give a list of amplitude values at fixed time intervals beginning at a specified value of time. Abaqus interpolates linearly between each time interval. For more information, see Defining equally spaced data.

• Choose Periodic to define the amplitude, a, as a Fourier series:

where $t0$, N, $ω$, $A0$, $An$, and $Bn$, $n=1,2⁢…⁢N$, are user-defined constants. For more information, see Defining periodic data.

• Choose Modulated to define the amplitude, a, as

where $A0$, A, $t0$, $ω1$, and $ω2$ are user-defined constants. For more information, see Defining modulated data.

• Choose Decay to define the amplitude, a, as

where $A0$, A, $t0$, and $td$ are user-defined constants. For more information, see Defining exponential decay.

• Choose Solution dependent to calculate amplitude values based on a solution-dependent variable. For more information, see Defining a solution-dependent amplitude for superplastic forming analysis.

• Choose Smooth step to define the amplitude, a, between two consecutive data points $(ti,Ai)$ and $(ti+1,Ai+1)$ as

where $ξ=(t-ti)/(ti+1-ti)$. For more information, see Defining smooth step data.

• Choose Actuator to import the current value of an actuator amplitude at any given time from a co-simulation with a logical modeling program. For more information, see Defining an actuator amplitude via co-simulation. No additional data is required to define the amplitude curve.

• Choose Spectrum to define a spectrum to be used in a response spectrum analysis. For more information, see Specifying a spectrum.

• Choose User to define the amplitude curve in user subroutine UAMP (Abaqus/Standard) or VUAMP (Abaqus/Explicit). For more information, see Defining an amplitude via a user subroutine.

• Choose PSD definition to define a frequency function that defines the frequency dependence of the random loading in a random response analysis step. This amplitude curve represents the power spectral density function for the random noise source. The PSD amplitude can be referenced in the correlation definition of a base motion boundary condition in a random response step. For more information, see Defining the frequency functions.

4. Click Continue.

The Edit Amplitude dialog box appears in which you can enter all of the data necessary to define the amplitude curve. See the following sections for detailed instructions: