Fatigue life

The fatigue life of a vehicle in terms of kilometres travelled and the type of application it is operated under is significant when determining whether the failure should be considered acceptable, premature, or somewhere in between. When working in linehaul operation a chassis failure would not be expected. However, the rigors of logging and its poor road and skid site access and other off-road usage such as quarrying, means higher fatigue loadings that can result in a failure much earlier in the vehicle's life even if it is no longer operating in that high fatigue environment.

First failure of a chassis rail (only use this code after the vehicle has traveled these distances)

Truck or tractor units

After at least 250,000km for a unit used for at least 30% of its operating life, at time of failure, on unsealed roads or in off-road conditions (loggers and milk tankers are two vehicle groups that generally fall into this category).

After at least 500,000km for a unit that does not spend at least 30% of its operating life off-road or on unsealed roads.

Trailers

After at least 250,000km for a trailer that does not spend at least 30% of its operating life off-road or on unsealed roads.

Cross-members and gussets

Technical Bulletin 1 – Heavy vehicle repair thresholds identifies those cross-members where the first failure, at whatever mileage, may be repaired using this code without requiring HV engineer certification.

Subsequent failure of cross-members if the failure does not occur within 250,000km of the repair.

Failure of gussets or auxiliary components of the chassis occurring after 250,000km.