Reliability Prediction Analyses
What is Reliability Prediction Analyses (RPA)?
RPA is the quantitative evaluation of a product’s Reliability performance. It entails Failure Rate (ʎ) and Mean Time Between Failure (MTBF) estimations.
Definitions:
- MTBF is calculated as the arithmetic mean (average) time between failures of a
system. - MTBF unit is depicted in hours.
In general, MTBF is the "up-time" between two failure states of a repairable system during operation as outlined here:
Equations:
Reliability Graph (Bathtub Curve):
Notes:
- Constant failure rate (ʎ) is utilized to estimate MTBF.
- Environmental Stress Screening (ESS) addresses infant mortality failures during manufacturing process. ESS eliminates manufacturing defects.
- Weibull Analyses predicts Wear Out failures.
Weibull Analyses:
A statistical analysis that predicts the probabilities of infant mortality and wear out
failures.
Dansob Weibull Analyses emphasizes on wear out failures only.
Objective:
The primary objective of Weibull Analyses is to espouse and improve product reliability by introducing Scheduled Maintenance Interval (SMI).
SMI is established by converting an exponential probability density function into a constant probability density function.
Equations:
F(t, ʎ, k) = Probability Density Function
k = Shape Parameter
ʎ = Failure Rate (per hour)
t = time (in hours)
Graph:
