2009

A factor of safety can be calculated as the ratio of the maximum allowable
stress to the equivalent stress (von-Mises) and must be over 1 for the design
to be acceptable. (Less than 1 means there is some permanent deformation.)
Factor of safety results immediately points out areas of potential yield, where
equivalent stress results always show red in the highest area of stress, regardless
of how high or low the value. Since a factor of safety of 1 means the material
is essentially at yield, most designers strive for a safety factor of between 2 to
4 based on the highest expected load scenario. Unless the maximum expected
load is frequently repeated, the fact that some areas of the design go into yield
does not always mean the part will fail. Repeated high load may result in a
fatigue failure, which is not simulated by Autodesk Inventor Simulation Stress
Analysis. Always, use engineering principles to evaluate the situation.
Frequency Modes
Use vibration analysis to test a model for:
■ Its natural resonant frequencies (for example, a rattling muffler during idle
conditions, or other failures)
■ Random vibrations
■ Shock
■ Impact
Each of these incidences may act on the natural frequency of the model,
which, in turn, may cause resonance and subsequent failure. The mode shape
is the displacement shape that the model adopts when it is excited at a
resonant frequency.
Frequency Modes | 11