A Rectangular Beam with Semicircular Notches Has Dimen- Sions $h=160 \mathrm{~mm} \text { and } h_{1}=140 \mathrm{~mm}$

A rectangular beam with semicircular notches has dimen- sions $h=160 \mathrm{~mm} \text { and } h_{1}=140 \mathrm{~mm}$ . The maximum allowable bending
Stress in the plastic beam is $\sigma_{\max }=6.5 \mathrm{MPa}$ , and the bending moment
Is $M=185 \mathrm{~N} \cdot \mathrm{m}$ . The minimum permissible width of the beam is: (A) $12 \mathrm{~mm}$
(B) $20 \mathrm{~mm}$
(C) $28 \mathrm{~mm}$
(D) $32 \mathrm{~mm}$

FIG. 5-50 Stress-concentration factor K for a notched beam of rectangular
Cross section in pure bending (h = height of beam; b = thickness of beam,
Perpendicular to the plane of the figure). The dashed line is for semicircular $\left(h=h_{1}+2 R\right)$