The following conclusions could be drawn from this
study:
1. Dynamic loading analysis of the crankshaft results in
more realistic stresses whereas static analysis
provides an overestimate results. Accurate stresses
are critical input to fatigue analysis and optimization
of the crankshaft.
2. There are two different load sources in an engine;
inertia and combustion. These two load source
cause both bending and torsional load on the
crankshaft.
3. The maximum load occurs at the crank angle of 355
degrees for this specific engine. At this angle only
bending load is applied to the crankshaft.
4. Considering torsional load in the overall dynamic
loading conditions has no effect on von Mises stress
at the critically stressed location. The effect of
torsion on the stress range is also relatively small at
other locations undergoing torsional load. Therefore,
the crankshaft analysis could be simplified to
applying only bending load.
5. Critical locations on the crankshaft geometry are all
located on the fillet areas because of high stress
gradients in these locations which result in high
stress concentration factors.
6. Superposition of FEM analysis results from two
perpendicular loads is an efficient and simple
method of achieving stresses at different loading
conditions according to forces applied to the
crankshaft in dynamic analysis.
7. Experimental and FEA results showed close
agreement, within 7% difference. These results
indicate non-symmetric bending stresses on the
crankpin bearing, whereas using analytical method
predicts bending stresses to be symmetric at this
location. The lack of symmetry is a geometry
deformation effect, indicating the need for FEA
8
modeling due to the relatively complex geometry of
the crankshaft.
8. Using the rainflow cycle counting method on the
critical stress history plot shows that in an entire
cycle only one peak is important and can cause
fatigue damage in the component.