Software for the Evaluation of Stress-Strain Diagrams

As a successful provider of material databases, M-Base for a long time has been involved in the process of material data generation and we have developed a series of tools supporting the user to manage the workflow from testing machines to the final datasheet, and integration into our databases.
For the classical tests with tensile load, we have now merged these tools into one comprehensive program for test evaluation. Stress-strain diagrams represent the most important information for engineers for material selection and design. Depending on the exact application, specific requests have to be applied on the graphs, which in many cases cannot be matched by the original test data.
In order to be stored in databases, curves need to be reduced to a limited number of control points and a couple of mathematical requirements have to be followed. For example curves representing different temperatures must not cross each other and curves should show no swinging. If stress-strain curves are converted, e.g. to secant modulus curves, even the smallest imperfections will lead to dramatic errors. Also curves from different tests (different temperatures, orientations, strain rates, etc.) tend to overlap in the low strain area. This is well inside the test accuracy, but will lead to mathematical problems in CAE programs and looks imperfect in datasheets.

 

These problems discourage many users from entering stress-strain data into databases and very often designers are restricted to use less meaningful single point data, even though complete curves have been measured.

 

The new software developed by M-Base will now help to reduce these problems. The program is able to read in raw data from the test machine via a simple data interface and convert the input into a format that can easily be stored in databases and which fulfills all mathematical and formal requirements.

 

On top of that the program offers an interface for transferring the information to target systems, like datasheet print, CAE-systems, etc.

 

The following features are available:

  • curves can be smoothed, oscillations eliminated
  • aareas with critical information, especially at start (e.g. offsets) will be eliminated/corrected
  • engineering properties, like modulus, yield and breakpoints can be detected automatically
  • quasistatic tests can be handled, as well as dynamic tests with shaking curves
  • representative curves or average curves can be generated from a number of tests
  • the number of control points can be adjusted to the requirements of the target system (e.g. CAMPUS rules)
  • the position of control points can be optimized
  • curves can be presented till yield (CAMPUS principle) or beyond yield till break (even with extremely high elongations)
  • presentation as true stress-strain is possible
  • the generated curves are built on a mathematical model, they fulfill all requirements, like no inclinations, no swinging in stress-strain or secant modulus curves
  • several material models are available for the fitting function. Model parameters are documented

 

If, for physical reasons, curves need to be in a certain order (temperatures, orientation, strain rate) the results can be checked for plausibility and under certain conditions the requested order can be enforced. Also curves that are not allowed to cross will be de-tangled.

 

The software is able to import original test data (force-displacement) as well as stress-strain data, allowing third parameters like temperature, strain rate or orientation. Isochronous stress-strain diagrams (creep) can also be prepared.

 

The new software is available as stand alone package to be installed on customers PC with minimal hardware requirements. For interested customers M-Base offers a free and unbinding trial with a couple of sample files to benchmark the software. The software can also be offered in consulting projects.