0

# finite element analysis (FEA)

Linear elastic models: linear = proportional, elastic = recoverable (not plasticly deformed)

Key types of loading:

- tension (pulling); stress (MPa) = normal force (N) /area (mm2)…= F/A
- compression (pushing); stress (negative MPa) = normal force (N) /area (mm2)… = F/A
- shear (along surface); stress = shear force (N) / area (mm)… = F/A
- bending (flexure); bending stress = moment (Nm) X distance from neutral axis (m) / second moment of area (m4)…= My/I
- torsion (twisting); shear stress = torque (Nm) x radius (m) / polar second moment of area (m4)…Tr/J
- peel (bond strength)
- cleavage (rigid peel)

second moment of area calculator

polar second moment of area calculator (Ip)

Main failure modes to consider:

- yielding (plastically deformed): stress (MPa) < yield strength (MPa); safety factor = yield strength (MPa) / max stress (MPa); if safety factor <= 1 then yielding occurs. Run static study.
- buckling (under compression + high aspect ratio): if buckling load factor < 1 then buckling occurs. Run buckling study.
- fatigue (accumulated damage, e.g. comet plane): Fatigue strength (MPa) = stress at which failure occurs after
*n*cycles (see S-N curve); If the max stress > fatigue strength, then fatigue failure occurs. Run static study but compare to fatigue strength, not yield. - delamination (separation of layers): difficult to simulate.

Some useful videos on creating, editing and using various tools in FEA using Solidworks Simulation: