General instructions

This section describes information common to multiple methods, or steps in the methods.

Adding rolling cycles

When adding many 100 steps, Abaqus CAE is rather slow. Therefore, a script is provided to extend a simulation by adding cycles with the same content repeated. Typically, if e.g. 25 is specified as the "cycle" above, then it sufficies to generate 26 cycles, and repeat these. The first cycle is not repeated, hence “doubling” the number of cycles will then give 51 cycles in total.

To add cycles, call the python script append_extra_cycles.py with the multiplication factor as the first argument and the input file as the second argument. The input file defaults to “rollover.inp”. If called with multiplication factor 4 in the above example, 101 cycles would be created.

Running simulation

To run the simulation the following (generated) files are required to be in the simulation directory:

  • rollover.inp (can have different name): The Abaqus input file

  • load_param.txt (must have this name): Automatically generated file in the same directory as rollover.inp when creating rollver. Describes the loading parameters

  • uel_stiffness.txt (must have this name): File specifying the wheel stiffness matrix. Automatically generated when creating the wheel, automatically copied to the same directory as rollover.inp when creating rollover

  • rp_coord.txt (must have this name): File specifying the location of the reference points. Automatically generated in the same folder as rollover.inp when creating rollover.

In addition, the user subroutine object file must be available, but it does not need to reside in the simulation directory, but can be in a separate directory and its path specified as <path_to_usub>.

Run the simulation by

abaqus job=rollover user=<path_to_usub>

The json format

The json format is used for the input data. Mostly, the files should be written with a similar formatting as for a Python dictionary. However, there are a few important differences:

  • Booleans are written true and false, as opposed to True and False.

  • All strings (keywords and variables) must be enclosed in double quotes (single quotes are not accepted).

  • Exponential formats must be written A.BeC (as opposed to A.eC) where A, B, and C are integers. E.g. 1.0e-3 is ok, but not 1.e-3.

  • Python’s None is written as null.

  • Comma is not allowed after the last item in a dictionary

To ensure the correct data format, one can write the following code in Python to generate the json file:

import json
filename = 'example.json'    # Give the filename that you want to save to

# Define the parameters you want to save as a Python dictionary
param = {'key1': [1,2,3],    # Example of list data
        'key2': 'this is a string example data' # Example of string data
        }
with open(filename, 'w') as fid:
   # Using indent=1 for nicer output, but not required
   json.dump(param, fid, indent=1)

The data folder and how to specify paths

In the repository, there is a folder named “data”. This contains some examples (which are version controlled). However, additional contents added to the subfolders are ignored by the version control and are suitable for adding data that can be reused later. Examples include profile sketches, generated wheels and rails, and compiled user subroutines.

To simplify the use of contents from this folder, path inputs in the *_settings.json files can be relative the data folder. To do this, the path should start by ":/", e.g. ":/rails/rail_example.cae". Otherwise, and absolute or relative (to the Abaqus working directory) path can be specified.

Creating a profile sketch

To create a profile sketch in Abaqus CAE, perform the following steps:

  1. Open Abaqus CAE

  2. Double-click “Sketches” in the model tree

  3. Give your sketch a name (this will have no effect later) and press “Continue”

  4. Draw a profile and exit the sketch.

  5. Go “File”-“Export”-“Sketch…” and choose a location to save the sketch.

  6. In the new dialog box, select the sketch you want to export and press “OK”

  7. Choose the ACIS version. Just make sure that it can be read by your system, press ok and you are done.

Note

The sketch will only contain the geometry, so if you later want to edit a dimension later, you need to save the .cae file containing the sketch. Then you can edit the sketch in this file later and export it again.