Reliability Analysis

It is defined as the probability that a given system will perform it’s function adequately for it’s specified period of lifetime under specified operating conditions.

Common measures are :

1. Failure rate.
2. Mean time between failures(MTBF)
3. Survival percentage.

Failure Rate:

Rate which components of population fail.

R(t)=N_s(t)/N_f(t)

 

Where,
            N_s(t)- No. of components that survived during time ’t’
            N_f(t) – No. of failures that occurred during the same time.


Mean time between Failures(MTBF):

The reciprocal of the failure rate(1/λ).
Where
           λ —-Failure rate.

Failure rate = (No.of failure )/(Time period during all components were exposed to failure)

Reliability Analysis:
Failure Mode and Effect Analysis(FMEA)

Purpose :
1. To recommend design changes.
2. To identify design weakness.
3. To help in choosing alternatives.

Four Stages:
I^st Stage – System boundaries and the scope of the analysis is decided.
II^nd Stage – Data Collection
                      Ex: Specification,Operating Procedure,Working Conditions.
III^rd Stage- Preparing the component or parts list.

IV^th Stage – Failure frequency and the functions of the part identified,causes of       failures,Failure detection.