Stress-Strain Curve & Hall-Petch Yield

This simulator pulls a virtual test bar and traces its stress-strain curve live, alongside a schematic specimen that stretches, necks and fractures in sync with the plot. Choose a material to set its Young's modulus and base strength, then tune grain size to watch the Hall-Petch relation shift the yield point — smaller grains mean a higher yield stress because grain boundaries block dislocation glide. Ductile metals show a clear elastic-to-plastic transition and neck before breaking; the brittle ceramic preset snaps with almost no warning, illustrating why crack-sensitive materials are designed with large safety margins.