Choose the right physical model
A small-displacement linear study can answer some stiffness questions. Contact separation, snap fits, large deformation, impact, or material yielding may require different physics. A modal shape shows a vibration mode with arbitrary normalization; its plotted amplitude is not an operating displacement prediction. Provide geometry and units, sourced material properties, physical attachment, loads, and the quantity you need. Distinguish an applied force from a prescribed displacement: the latter can be used to calculate the reaction needed to impose that motion.Start with a controlled example
Set up a simple stiffness calculation
Compare with the beam estimate
For the idealized end load above, the elementary bending estimate isdeflection = F L³ / (3 E I), with I = width × thickness³ / 12. In consistent N and mm units, E = 70,000 N/mm² and I = 106.67 mm⁴.
These are beam-theory reference values. A three-dimensional finite-element model can differ because of its formulation and end constraints. Ask Adam to explain the difference and mesh sensitivity. A factor-of-1,000 discrepancy is a reason to check units before changing the physics.
Inspect setup and results
1
Verify the physical inputs
Read back material assignments, units, load direction and total, support locations, and contact assumptions.
2
Run and preserve evidence
Keep the input deck or native study, mesh, solver version, logs, and achieved load or time step.
3
Check numerical behavior
Review termination, finite results, equilibrium where available, and refinement of the requested response.
4
Interpret the engineering result
Compare against the supplied requirement and explain the effect of assumptions, singularities, or missing checks.
Compare a design change
Compare two revisions at the same conditions