As Stephan notes, both SPMLab and NanoScope software have simple controls in ramp mode where you can type in the approach rate or retract rate that you desire. These rates control the speed of the piezo during ramping, so they are indirectly related to the loading rate (which would presumably be dF/dt where F is the load). To measure the loading rate of a force curve, load the file into NanoScope Analysis, set the "X data type" to "Time" and the "Plot Units" to "Force". If you have a good Spring Constant and Deflection Sensitivity, you should see a plot with horizontal axis of Time and vertical axis Force. Drag two cursors from the left axis onto the plot and position them to select the range of data that you would like to use for your calculation. Read the "dY/dX" result for "Marker Pair 1" (it will probably be in nN/s) or set the "Fit Type" to "Line" and read the "Least Squares Equation" result. The dF/dt number is just in front of the "x".

The stress and strain states of the material under the tip are complicated (stress and strain in the sample depend on position as well as load), so the loading rate might not be the best way to describe the situation. Instead, researchers often use an "Effective strain rate" defined as (1/h)*(dh/dt) where h(t) is the displacement as a function of time. In standard force curves, this effective strain rate is not a constant, but varies during the ramp of the Z piezo.

B. N. Lucas, W. C. Oliver, G. M. Pharr, and J-L. Loubet published a nice paper on "Time Dependent Deformation During Indentation Testing" that appeared in Mat. Res. Soc. Symp. Proc. Vol. 436 in 1997.

The same authors have also published other papers on this sort of thing, so you might want to do a literature search.

To analyze the effective strain rate for a force curve, you will need to do the following:

Load the force curve into MatLab, Excel, Igor, or your favorite math program either directly from the binary or by first exporting it to ASCII from NanoScope Analysis

Calculate the displacement h(t) by subtracting the cantilever deflection (in nm) from the Z position (in nm) and adding a constant to set the point where tip and sample first touch to zero

Calculate (1/h)*(dh/dt) for each pair of points in the curve

I attached the force-curve dialog for Innova and the Dimension Edge. As you can see the Approach Rate and Retreat Rate can by selected by the user by simply typing in the speed desired. If the check-box on the right is enabled, both rates will be the same. If the check-box connecting the Z-Start value is checked, the relative rate (in Hertz) will stay the same. You can select one or two absolute trigger values on the bottom. For zooming into a region of interest you either type new start and end values or simply draw a box around the area of the force curve you want to examine in more detail.

In short, your speed controls are there and depending on the spring constant of your cantilever you can easily calculate the rate in forcechange/second that you inquired about.

As Stephan notes, both SPMLab and NanoScope software have simple controls in ramp mode where you can type in the approach rate or retract rate that you desire. These rates control the speed of the piezo during ramping, so they are indirectly related to the loading rate (which would presumably be dF/dt where F is the load). To measure the loading rate of a force curve, load the file into NanoScope Analysis, set the "X data type" to "Time" and the "Plot Units" to "Force". If you have a good Spring Constant and Deflection Sensitivity, you should see a plot with horizontal axis of Time and vertical axis Force. Drag two cursors from the left axis onto the plot and position them to select the range of data that you would like to use for your calculation. Read the "dY/dX" result for "Marker Pair 1" (it will probably be in nN/s) or set the "Fit Type" to "Line" and read the "Least Squares Equation" result. The dF/dt number is just in front of the "x".

The stress and strain states of the material under the tip are complicated (stress and strain in the sample depend on position as well as load), so the loading rate might not be the best way to describe the situation. Instead, researchers often use an "Effective strain rate" defined as (1/h)*(dh/dt) where h(t) is the displacement as a function of time. In standard force curves, this effective strain rate is not a constant, but varies during the ramp of the Z piezo.

B. N. Lucas, W. C. Oliver, G. M. Pharr, and J-L. Loubet published a nice paper on "Time Dependent Deformation During Indentation Testing" that appeared in Mat. Res. Soc. Symp. Proc. Vol. 436 in 1997.

The same authors have also published other papers on this sort of thing, so you might want to do a literature search.

To analyze the effective strain rate for a force curve, you will need to do the following:

Load the force curve into MatLab, Excel, Igor, or your favorite math program either directly from the binary or by first exporting it to ASCII from NanoScope Analysis

Calculate the displacement h(t) by subtracting the cantilever deflection (in nm) from the Z position (in nm) and adding a constant to set the point where tip and sample first touch to zero

Calculate (1/h)*(dh/dt) for each pair of points in the curve