How can you analyze data sets with more than one failure mode in
Weibull++ offers two options for analysis when a group of
products fails due to more than one failure mode.
- Competing Failure Modes:
For data with up to four failure modes, you can enter all
of the data in a single Data Sheet, using subset IDs to
differentiate among the modes. Select a Weibull,
exponential, normal or lognormal distribution with the CFM
option under Parameters/Type. When you click Calculate,
the Competing Failure Modes Select Subsets window will
appear, as shown next.
This window allows you to
specify which subset ID(s) represent which failure modes. In
the analysis, each failure mode is analyzed separately, with
data from the other modes treated as suspensions. The
failure modes are then combined in a series reliability
model, wherein the overall reliability of the series system
is equal to the product of the reliability values of the
failure modes that compose the system.
- Reliability Block
Diagrams: Weibull++'s Diagrams offer greater flexibility
for analyzing more complex systems of failure modes. You can
consider unlimited failure modes, each analyzed with the
lifetime distribution appropriate to its data set, and model
the failure behavior by describing the reliability-wise
relationships among the modes (i.e. series, parallel,
k-out-of-n). The data set for each failure mode is entered
on a separate Data Sheet and analyzed with the chosen
distribution. When you create the Diagram, a template for
each Standard Folio, containing a block for each Data Sheet
within the Folio, is created. You can drag these blocks into
the Diagram and arrange and connect them using node blocks
and connector blocks to model the configuration of the
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