Weibull++ Example 4 - Degradation Analysis Example
Background
Five turbine blades were tested for crack propagation. The test units were cyclically stressed and inspected every 100,000 cycles for crack length. Failure is defined as a crack of length 30 mm or greater.
Using Weibull++ 7's Degradation Analysis module and Quick Calculation Pad, determine the B10 life for the blades using degradation analysis with an exponential model for the extrapolation.
Experiment and Data
The table shown next displays the test results for the five units at each cycle.
| Cycle (x100) | Unit A | Unit B | Unit C | Unit D | Unit E |
| 100 | 15mm | 10mm | 17mm | 12mm | 10mm |
| 200 | 20mm | 15mm | 25mm | 16mm | 15mm |
| 300 | 22mm | 20mm | 26mm | 17mm | 20mm |
| 400 | 26mm | 25mm | 27mm | 20mm | 26mm |
| 500 | 29mm | 30mm | 33mm | 26mm | 33mm |
Analysis
Step 1: Using Weibull++ 7, create a Degradation Analysis Folio and enter the data into the Data sheet. Select Exponential for the model and enter 30 for the Critical Degradation, as shown next.
Calculate the parameters. To view them, click the Show Fit Parameters button in the Control Panel. The parameter results will appear in the Results Panel, as shown next.
Step 2: Next, plot the data from the degradation analysis, as shown next.
Step 3: Transfer the extrapolated failure times from the Degradation Analysis Folio to a new Standard Folio. Analyze the data using the 2-parameter Weibull distribution and MLE, as shown next.
Step 4: Using the QCP, the B(10) life is calculated to be 399,597 cycles, as shown next.
