Calculating damage in LMS Tecware ProcessBuilder
LMS Tecware ProcessBuilder is a graphical environment where multiple methods can be combined together to create a data processing routine. Methods that can be combined include:
Building a Processing Routine
To calculate damage from a load time history in Tecware Processbuilder, the following steps are required:
Select Time Histories
Time history file selection can be done via the menu File-Data Import, or just by drag-and-drop of time data files from the Windows Explorer to the ProcessBuilder.
First select some time data to process, by choosing the ‘Data Import’ icon in the upper left as shown in Figure 1. An ‘Import’ dialog box will open.
In the ‘Import’ dialog box, several different file types can be selected, including LMS LDSF, RPC, ASCII, etc. Navigate to a directory containing data and double click on it to select it for processing as shown in Figure 2.
Press ‘Open’ when finished. There are checkboxes for selecting entire files or individual channels to be processed. By default, all added data is to be processed.
Next a processing routine consisting of different methods is built.
Drag and drop from the ‘Input/Output’ methods (right side of screen) one ‘Input’ method and one ‘Output’ method as shown in Figure 3. These will be at the beginning and end of the process.
Then from the ‘Histogram Counting’ methods, drag and drop the ‘Rainflow Counting’ icon in the middle screen (Figure 4).
From the group ‘Export/Convert’ drag and drop the ‘Export Properties’ method into the process as shown in Figure 5. ‘Export Properties’ allows data results to be exported into Excel easily.
Note: Dropping a method on an existing method in the middle area automatically connects the two methods.
In the end, the process should look like Figure 7.
Double-clicking an individual method will open the parameters. For Rainflow Counting, adjustments can be made to the number of bins, the limits, hysteresis gate, and whether groups of channels should share the same limits.
To compare different loads based on their damaging behavior, the damage can be calculated based on a SN-Curve. The SN-Curve can come from a number of different sources:
Now press the “Run” button to run the methods as shown in Figure 8. Methods will turn green as they are completed.
Viewing Results: Excel
The Excel file with the damage values is available using a right-click on the ‘Export Properties’ method, and select ‘Show Excel’ as shown in Figure 9.
The Excel file contains one line per channel and a default set of attributes like path, file name, channel name, unit, statistics and damage as shown in Figure 10. If multiple files were processed, they appear on different Excel worksheets.
To change the selection of attributes, double-click on the ‘Export Properties’ method and press the button ‘Select Properties’ as in Figure 11.
Either remove ‘Selected Properties’ on the right, or add more attributes from the ‘Available Properties’ area on the left. If the ‘Available Properties’ on the left is empty, a run must be processed, so that the available attributes are filled in as shown in Figure 12.
Viewing Results: Rainflow Matrices and Data Graphs
To view the input data time histories or the resulting rainflow matrices, right click on the ‘Rainflow Counting’ method, and select “Show data in input” or “Show data in output” as appropriate (Figure 13). For the Rainflow Counting method, input data is the time history, while the output data is the rainflow matrix.
After selecting ‘Show data in output’ a ‘Management of Results’ dialog box is opened (Figure 14). Here one can view the Rainflow matrices and use the arrow buttons to scroll thru the different channels.
From the Rainflow matrix display, it is possible to view the cycle counts and accumulated damage. To do so, choose ‘Analyze -> Range Pair’ from the menu (Figure 15). An accumulated cycle display is shown, showing the amplitude of the cycles versus the number of cycles.
To see the residue, select ‘Options -> Graphic Residue’ in the Rainflow display menu.
In the RangePair display, one can then switch to accumulated damage using the toggle bar in the lower left (Figure 16). Remember, when the accumulated damage is equal to or greater than one, failure occurs.
There are several other methods for fatigue life calculation in LMS Tecware ProcessBuilder. There are methods for Stress Life and Strain Life calculations.
These other fatigue methods can be run via LMS Test.Lab tokens with LMS Test.Lab 16A revision or higher.
More Fatigue and Durability links: