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Reliability Engineering

FMEA Risk Priority Number (RPN) Calculator

Calculate RPN = S×O×D for each failure mode. Quantify Pareto analysis, risk matrix, and countermeasure effectiveness. AIAG FMEA 5th edition compliant.

Max RPN
Average RPN
RPN > 100 Count
RPN > 200 Count
Total Risk Reduction
FMEA Table
0 (0 = show all)
# Part / Function Failure Mode Effect Cause S O D RPN Countermeasure S' O' D' RPN' Red.%
RPN Pareto Chart
Before/After RPN Comparison

Theory

$\text{RPN} = S \times O \times D \quad (\text{max } 1000)$

Severity S: 1 (no effect) – 10 (hazardous without warning)    Occurrence O: 1 (extremely rare) – 10 (almost certain)

Detection D: 1 (always detected) – 10 (undetectable)

Risk reduction rate: $\dfrac{\text{RPN} - \text{RPN}'}{\text{RPN}} \times 100\%$

CAE Integration: Set O and S scores from FEM stress analysis results / Compare RPN before and after structural optimization / Complementary use with FTA (FMEA: bottom-up, FTA: top-down) / Preliminary analysis for ISO 26262 and IEC 61508 functional safety.