zhfzzz / pdprop2

Version 2: Added code to pdprop files for multiple da/dN lines for fatigue crack propagation.

pdprop2

Version 2: Added code to pdprop files for multiple da/dN lines for fatigue crack propagation.

Pdprop version 1 enabled the use of only a single da/dN vs Delta_K file.
The extension to use multiple da/dN files of different R-ratios, including several pre-computed sets based on ASME and Hasegawa et al, caused substantial changes in the propagation computation models and some of the supporting files and scripts. The changes were made for better simulation of variable amplitude fatigue histories where cycles with different R-ratios are common. A good reference explaining the concept of multiple R-ratio lines is: K.Hasegawa, M.Vratislav, Y.Yamaguchi, Y.Li, “Fatigue Crack Growth Rates for Ferritic Steels Under Negative R Ratio”. ASME 2016 Pressure Vessels and Piping Conference, 50350, p. V01AT01A007.

It was thought best to present all the files, old unchanged and new changed, in a separate repository pdprop2.

------------------------Readme file from older pdprop: Simulation of metal fatigue crack propagation with accounting for material memory effects.

The software can be used to simulate crack propagation in plates and pipes. At this time the following geometries are incluced

1. A full width surface crack in a plate
2. Elliptical surface crack in a plate
3. Internal elliptical surface crack in pipe
4. Center thru crack in a plate
5. Edge thru crack in a plate
6. Rod surface crack

Loading can be specified with a variable amplitude bending and membrane (axial) stress history. The sequence effects of the stress history is modelled by rules that mimic the material's memory of prior stress-strain behavior. Estimation of the Stress Intensity follows the rules set out by British Standard BS7910. For elliptical shaped cracks a separate memory model is run for each of the "a" and "c" crack lengths; i.e. where "a" is the depth of the crack, and "c" is the 1/2 width of the crack on the surface.

A example set of material data is provided: A36 steel with da/dn curves, crack initiation data, and a short stress history. One of the three problem folders also contains a sample output report generated from a simulation run. The large output file created by a simulation is not, however, included in the folder.

Prerequisites: gfortran (a subset of gcc), gnuplot, htmldoc, bash, Linux

The code is contained in a compressed tar file. It was developed on openSuse Linux. There are some bash scripts that help the user during problem setup, for final report generation, and for initial compile of all the software. All of the runtime code is written in gfortran. All code is GPL licensed.

A readme file in the tar file will explain how to setup the files and run the compile script. Each of the three crack type geometries is located in its own folder and a setup script is provided to help the user with the problem definition.

It is expected that the user has an understanding of metal fatigue and the terms used in BS7910.

Note: Some example result files may be out of data due to software changes. These will be updated shortly

For reference on how the material memory logic works the reader is referred to: Conle, A., T.R.Oxland, T.H.Topper, "Computer-Based Prediction of Cyclic Deformation and Fatigue Behavior," Low Cycle Fatigue ASTM STP 942, 1988, pp.1218-1236

An example of how both the crack initiation and the propagation software can be applied to a fatigue life prediction case history is provided here: http://fde.uwaterloo.ca/Fde/Crackgrowth/Case5/case5_HeulerSeeger.html

A tutorial on fatigue testing and calculation can be found at http://fde.uwaterloo.ca/FatigueClass/classIndex.html