고체역학 (Beer) — Transformations of Stress and Strain: Problem 7.160

7.160 Two steel plates of uniform cross section $10 \times 80 \text{ mm}$ are welded together as shown. Knowing that centric $100\text{-kN}$ forces are applied to the welded plates and that the in-plane shearing stress parallel to the weld is $30 \text{ MPa}$, determine (a) the angle $\beta$, (b) the corresponding normal stress perpendicular to the weld.