Stress and Strain

Stress and Strain

Material selection is not about picking the strongest material — it is about matching material behavior to the load case. Understanding stress and strain is how you do that.

Normal Stress

Stress is force per unit area:

σ = F / A

Units: Pascals (Pa = N/m²), or MPa for structural work.

Strain

Strain is the fractional deformation:

ε = ΔL / L₀

Strain is dimensionless.

Hooke's Law

In the elastic region, stress and strain are proportional:

σ = E · ε

Where E is the elastic modulus (material stiffness), measured in GPa.

Why This Matters for CatBot

The QDD actuator housing must transmit large torques without deflecting. Knowing the elastic modulus of the chosen material tells you how much the housing will twist under load — directly affecting position accuracy.