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Table 2 Classification of DDR

From: Weakness Ranking Method for Subsystems of Heavy-Duty Machine Tools Based on FMECA Information

Category

Description

DDR Score

Trapezoidal fuzzy number DDR Score

Class I (Cannot detect)

Almost impossible to be detected

10

\(\widetilde{r}_{1}\) = (9, 10, 10, 10)

Class II (Very difficult to detect)

Slight possibility of being detected

9, 8, 7

\(\widetilde{r}_{2}\) = (6, 7, 9, 10)

Class III (Difficult to detect)

Can be detected on the spot or during disassembly

6, 5, 4

\(\widetilde{r}_{3}\) = (3, 4, 6, 7)

Class IV (Able to detect)

Self-warning

3, 2

\(\widetilde{r}_{4}\) = (1, 2, 3, 4)

Class V (Easy to detect)

Visual detection

1

\(\widetilde{r}_{5}\) = (1, 1, 1, 2)