Repairable Systems SimuMatic Setup

For reliability growth data analysis only.

Weibull++'s Repairable Systems SimuMatic tool generates multiple data sets using Monte Carlo simulation. It then analyzes each data set individually (e.g., to find the instantaneous MTBF at a specified time) and also analyzes the group of data sets as a whole (i.e., it shows the average and median parameter values for all data sets).

To create a SimuMatic folio for growth data, choose Home > Insert > SimuMatic and choose the Repairable Systems SimuMatic option.

The setup window will appear. Follow the steps outlined below to generate and analyze the simulated data sets.

  1. On the Main tab of the window, select a data type and time units in the Data Type area. In the Parameters area, enter the beta and lambda values for the Crow-AMSAA model that will be used to generate the data set.

    In the Data Sets / Points area, enter the following information:
    • Specify the Number of Data Sets that will be generated.
    • Specify the Number of systems for which data will be generated. This value is fixed at 1 unless you selected a multiple systems data type on the Main tab (i.e., Multiple Systems - Concurrent or Repairable Systems).
    • Use the Test termination field to specify what will determine the end of the observation period for the simulated data.
      • If the period will end after a specific number of failures have been observed, choose Failure Terminated from the drop-down list and enter the number of Failures in the next field.
      • If the observation period will end at a specific time, choose Time Terminated from the drop-down list and enter a Time in the next field.
    • If you selected to generate Grouped Failure Times data, click the Set Intervals link to open a window that allows you to specify the intervals that will contain the failures. You need at least three intervals to simulate this type of data.
  2. On the Settings tab, specify how you want to generate the data set and where you want the data to be stored.
    • Select the Use Seed check box if you would like to set a consistent starting point from which the random numbers will be generated. Using the same seed value and keeping all other settings the same will allow you to replicate your results.
    • In the Math Precision area, enter the number of decimal places that will be used for each simulated data point. (This does not affect the precision used in the calculated parameters and other results.)
  3. On the Analysis tab, enter the bounds that will be shown in the SimuMatic plots. For example, if you enter 90, then the plots will show 90% one-sided upper and 90% one-sided lower confidence bounds.
  4. On the Test Design tab, select the Calculate Target Time check box if you wish to a) calculate the time at which the demonstrated MTBF reaches a certain value and b) mark the lower confidence bound on this value on the instantaneous MTBF vs. time plot. For example, if you wanted to know the time for an instantaneous MTBF of 1,000 hours, then you would enter 1,000 in the Instantaneous MTBF field. To mark the 90% lower confidence bound on this value in the IMTBF vs. time plot, you'd enter 90 in the Lower 1-sided Confidence Level field.
  5. On the Results tab, specify the metrics that will be calculated.
    • The first four areas are for instantaneous MTBF calculations (i.e., the MTBF over a small interval dt that begins at a specified time) and cumulative MTBF calculations (i.e., the MTBF from time = 0 up to a specified end time). Click the arrow to open a drop-down table where you can enter the user-specified values.
      • The two areas on the left (e.g., Instantaneous MTBF Given Time) allow you to specify up to ten different times and SimuMatic will calculate the MTBF(s).
      • The two areas on the right (e.g., Time Given Instantaneous MTBF) allow you to specify up to ten different MTBFs and SimuMatic will calculate the time(s).
    • In the Metrics to Calculate area, select the metrics you wish to calculate for each data set. You can then use the results on the Sorted sheet to estimate, for example, the one-sided 90% lower confidence bound on any of these values at the end of the test. (See SimuMatic Example.)
  6. Click the Generate button to create and analyze the data. The results will be displayed in the Repairable Systems SimuMatic folio.

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