The bar is held fixed at the wall and pulled by a load expressed as a percentage of the material's yield strength. Below 100% the bar only stretches elastically — remove the load and it snaps back — following Hooke's law, E = σ/ε. Push past 100% and the excess stress drives permanent plastic strain that accumulates over time (a simplified stand-in for plastic flow and creep), so the bar keeps growing even at constant load. Temperature adds its own reversible thermal strain on top, sized by the material's expansion coefficient.
ε_elastic = σ / E
ε_thermal = α · ΔT
dε_creep/dt = k · max(0, σ − σ_yield)
ε_total = ε_elastic + ε_thermal + ε_creep
- Applied load — stress as a fraction of the chosen material's yield strength; above 100% the bar starts yielding and creeping.
- Temperature — shifts thermal strain relative to a 20 °C reference; a bigger coefficient of thermal expansion (α) moves the bar more per degree.
- Material — sets stiffness (E), yield strength, thermal expansion coefficient and creep rate; rubber has huge reversible elastic strain but a low yield, steel is stiff and mostly elastic until it clearly yields.
- Time-dependent creep — toggle off to freeze plastic/creep accumulation and see only the instantaneous elastic + thermal response.
Deformation is magnified for visibility — real engineering strains at these loads are a fraction of a percent, far too small to see on a rendered bar, so the geometry exaggerates the true strain by a fixed factor while the strain readouts stay physically accurate.