Page 275 - Handbook of Materials Failure Analysis

6 Parametric Accelerated Life Testing 271

Total components: 25,000ea

Automobile
System

5 system ( ) Sub
Engine system Transmissionsystem Drive system Electric system Body system

Engine Emission Exhaust Trans- Trans- Steering Body
Engine Engine Engine Drive Climate Audio Paint Squeaks
-major -minor cooling electrical fuel system mission mission system sus- Break Power system video trim hard- rattles
Main
module
system system major minor pension ware
17
( )
E E 4
G Air sensor C Exhaust pipe Exhaust manifold Muffler Torque converter Transmission body Torque converter Clutch Shift lever Tr. Control system Tr. Cooling system Drive shaft CV Joint Differential gear W ESC Tie rod Busing Shock absorber Ball joint ECS Break Disk Master cylinder ABS Parking braek Cruise control Horn Wiper Lights Heated seat TPMS Compressor Cond
parts
Main
(25,000) R U D
Pulley
Starter
Battery
Radiator
Alternator
Timing belt
Fuel gauge
Thermostat
Water pump
Engine body
Fuel supplier
Timing chain
Cooling pan
Engine sensor
Turbo charge
Cylinder head
Ignition system
Accessories belt
Engine mounting
(a) Automobile field
l
Straight line Wear-out
failure
Overstress
failure
L2 L1 t MTTF
(b) Product lifetime L and failure rate l s
Bx
FIGURE 11.8
Product lifetime such as automobile L BX .
2. After assuming a shape parameter that is indicating the intensity of wear-out
failure in the distribution of Weibull, calculate the necessary sample size
considering the lifetime target.
3. Performing longer than minimum actual test periods, shape parameter will be
determined.
Let us suppose that there is no initial failure, product lifetime L 2 due to overstress will
determine in Figure 11.8b. The cumulative failure rate of set lifetime is the sum of the
failure rate of each units.