When estimating failure rates for mechanical components, the approach depends on component type, operating environment, load cycles, and material properties.

The mechanical failure figure uses λ = failures per million hours (FPMH) or failures per 10Ʌ6 cycles.

Common Mechanical Components

Bearings (rolling element), plain bearings/bushings, gears, springs (coil, leaf), seals (O-rings, lip seals), fasteners (bolts, rivets), shafts/couplings, valves, pumps (centrifugal/gear), fans/blowers, actuators (mechanical), connectors (mechanical joints).

Estimation Methods

Empirical / Handbook-Based

Use failure rate models or tables from:

• NSWC-98/LE1: Mechanical Equipment Reliability Sourcebook (Naval Surface Warfare Center)
• NPRD-2016: Non-Electronic Parts Reliability Data
• FIDES 2009: Includes mechanical part models
• These provide baseline failure rates adjusted for:
• Load factor (operating stress/rated stress)
• Environmental factor (temperature, humidity, dust, etc.)
• Duty cycle and maintenance level

Analytical / Physics-of-Failure

Derive from fatigue, wear, or corrosion models. This method applies to rotating components such as shafts, springs, and bearings.

Statistical / Field Data

Fit failure data to a distribution (e.g., Weibull, lognormal)

Combining Mechanical and Electronic Reliability

When mechanical and electronic subsystems coexist (e.g., mechatronic actuators), the total system failure rate is:

λtotal=λelectronic + λmechanical 

and the total system MTBF is: 

MTBF=1/λtotal

The reliability report includes the MTBF figure for the whole system.