Four aluminum (
G=36GPa
) rivets (
B,C,D,E
) and a copper (
G=20
GPa) rivet (A) are used to fasten a rigid plate on a fixed mount. Rivets
A
,
D
, and
E
have a diameter of 60 mm while rivets
B
and
C
have a diameter of 30 mm . Calculate the largest shear stress (MPa) that develops in the bolt assembly if a couple force
F=15kN
is applied on the rigid plate as shown.