This is the Documentation of the Python Creep Macro.

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Lukas Gartmair Lukas_Gartmair@gmx.de v.1.0 ########

Usage:

The program is written for a certain data scheme (only this scheme) that looks as the following:

Zeit [s] Weg [mm] Kraft [N] Epsilon 0 Epsilon w Sigma 0 Sigma w Epsilon w Punkt Temperatur [°C] 0.24 2.9546998e-4 4.080 0 -3.8922959e-5 0 -0.198 -1.8551e-05 1099.97 0.74 3.6588452e-4 10.200 0 -4.8198611e-5 0 -0.495 -1.1669e-05 1100.00

• It has to contain at least the columns TIME / LONGITUDINATION / FORCE exactly in this order! Addiotional columns are ignored.
• The longitudination is decreasing
• So does the force

Options:

Enter all options with a dot! Example: height = 22.45 mm A comma will raise an error. Currently dummy values are set in main.

Output:

Datapoint Nr. Strain / % Strainrate / %/s Filtered Strain / % Filtered Strainrate / %/s

What the program does:

1st

• Read in the specimen data and file paths
• Correct height/area with respect to the thermal expansion coeff
• Get the start of the desired stresslevel
• Check for equally small values in the beginning and cut them
• Get the slope of long - force plot and correct longitudination

2nd

• Calculate strain true and stress true
• Get the transition from elast to plast and get the elast slope
• Calculate strain plast and strainrate plast

3rd

• Filter the data like getting iteratively windows, calc the linear sub slope and take the desired number of points that are closest to this fit
• Get the errors for the slope and the y-intersection for each window

4th

• Plot the results
• Write a summary file

The function for the window_selcetion works this way:

1st define a window_interval for the slopes

3rd the slopes refering to the window size from stepp 1 are calculated and depending on their value decided whether a new window start has to take place or not

2nd define a window interval for the strain dependent selection

4th a new strain based window is placed every nth percentage of total strain

5th the windows are generated with the intervals determined above

6th the window indices are reduced - every window must have at least 3 points to generate the fit in the next step

7th. fit every window and get the closest point to its fit