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Download Example File for Version 10 (*.rsgz10) or Version 9 (*.rsr9)
A particular component can fail due to six independent primary failure modes: A, B, C, D, E and F. The component fails if mode A, B or C occurs. If mode D, E or F occurs alone, the component does not fail; however, the component will fail if any two (or more) of these modes occur (i.e., D and E; D and F; E and F). The objective is to analyze each failure mode using the 2-parameter Weibull distribution with MLE and to determine the lower 1-sided 90% confidence bound on the reliability of this component at 100 hours.
An independent test on each failure mode is conducted. The following tables record the times-to-failure data of each mode (in hours).
| Mode A | Mode B | Mode C | ||||||||
| Number in Group |
State | Time | Number in Group |
State | Time | Number in Group |
State | Time | ||
| 1 | F | 1144 | 1 | F | 19 | 1 | F | 2221 | ||
| 1 | F | 1719 | 1 | F | 140 | 1 | F | 2257 | ||
| 1 | F | 2129 | 1 | F | 292 | 1 | F | 2569 | ||
| 1 | F | 2803 | 1 | F | 432 | 1 | F | 3029 | ||
| 1 | F | 3020 | 1 | F | 528 | 1 | F | 3805 | ||
| 1 | F | 3082 | 1 | F | 552 | 10 | S | 5000 | ||
| 1 | F | 3589 | 1 | F | 605 | |||||
| 1 | F | 3973 | 1 | F | 734 | |||||
| 1 | F | 4337 | 1 | F | 779 | |||||
| 1 | F | 5011 | 1 | F | 874 | |||||
| 1 | F | 5029 | ||||||||
| 18 | S | 5500 | ||||||||
| Mode D | Mode E | Mode F | ||||||||
| Number in Group |
State | Time | Number in Group |
State | Time | Number in Group |
State | Time | ||
| 1 | F | 1063 | 1 | F | 1290 | 1 | F | 605 | ||
| 1 | F | 1085 | 1 | F | 2261 | 1 | F | 760 | ||
| 1 | F | 1399 | 1 | F | 2355 | 1 | F | 773 | ||
| 1 | F | 1445 | 1 | F | 3209 | 1 | F | 854 | ||
| 1 | F | 1550 | 1 | F | 3284 | 1 | F | 890 | ||
| 1 | F | 2056 | 1 | F | 3394 | 1 | F | 1165 | ||
| 1 | F | 4384 | 1 | F | 3596 | 1 | F | 1220 | ||
| 1 | F | 4863 | 1 | F | 4203 | 1 | F | 1320 | ||
| 8 | S | 5000 | 1 | F | 4254 | 1 | F | 1967 | ||
| 1 | F | 4294 | 1 | F | 2606 | |||||
| 1 | F | 4420 | 1 | F | 2834 | |||||
| 10 | S | 5000 | 15 | S | 3000 | |||||
Step 1: Create a new Weibull++ standard folio data sheet that holds grouped times-to-failure data with suspensions.
Step 2: Rename the folio to “Component” and the data sheet to “A.” Enter the data given for Failure Mode A and use the 2-parameter Weibull distribution with MLE to calculate the parameters, as shown next.
Figure 1: Data sheet A with data entered and results shown.
Step 3: Insert another data sheet into the folio by choosing Life Data > Folio Sheets > Insert Data Sheet. Rename the new data sheet to “B,” enter the data given for Failure Mode B and calculate the parameters. Repeat for the remaining failure modes.
Step 4: Add a diagram to the project by choosing Insert > Tools > Diagram. Click the Data Sheets page of the diagram control panel. All the calculated data sheets in the project will be shown. Drag a data sheet onto the diagram to create a block that represents that data sheet.
Figure 1: Degradation analysis folio.
The following plot shows the exponential curves for six of the tested samples (with the scaling adjusted to Y= 40 to 100 and X= 0 to 20).
Figure 2: Data Sheets page of the diagram control panel.
Step 5: Build the RBD that describes the reliability-wise configuration of the failure modes. To add a node that requires that 2 out of 3 paths must function for the system to function, choose Diagram > Diagram Tools > Add Node. Then double-click the node to specify the number of required paths.
Figure 3: Completed reliability block diagram.
Step 6: Return to the Main page of the diagram control panel, then click Calculate to analyze the diagram. Use the Quick Calculation Pad to calculate the lower 1-sided 90% confidence bound on the reliability at 100 hours. The lower bound is estimated to be 82.23%, as shown next.
Figure 4: Solving for the lower 90% 1-sided confidence bound on reliability at 100 hours.
