Where $K_t$ (theoretical stress concentration factor) depends on geometry (e.g., $r/d$ ratio for a shoulder fillet).
Where $K$ is the :
$$\tau_max = \sqrt\left(\frac\sigma_x - \sigma_y2\right)^2 + \tau_xy^2$$ mechanics of materials 2
[ \delta_i = \frac\partial U\partial P_i ] you mastered the fundamentals: axial loading
If you survived the first course in Mechanics of Materials (often called "Strength of Materials"), you mastered the fundamentals: axial loading, torsion, basic beam bending, and shear/moment diagrams. You learned to find stress ($\sigma = P/A$) and strain ($\epsilon = \delta/L$) in simple, prismatic members. basic beam bending