aluminium in commercial vehicles - European Aluminium Association

76 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
8. Fatigue
8.1. Theory
Structures with repeating loads
may be susceptible to fatigue
when the number of load cycles
is high, even when the loads give
low stresses in the structure.
Fatigue failure starts with development
of a crack at a point with
stress concentrations. With continuous
repeating loads the crack
will grow, this will be shown as
one striation in the failure surface
for each load cycles. The distance
between the striations is
depending on the stress range
and that is giving the growing
speed. The stress range is
defined as the algebraic difference
between the stress peak
and the stress valley in a stress
cycle. At low stress ranges the
crack grows slowly and with high
stress range it grows fast. (Figure
VI.13)
Trailer fatigue testing in laboratory (Benalu)