Consider a circular hollow section, with outer diameter dD (in mm), and thickness tD (in mm). The circular hollow sectio

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Consider a circular hollow section, with outer
diameter dD (in
mm), and
thickness tD (in
mm).
The circular hollow section is made from aluminium which has a
density of 2700 kg/m3 and a shear
modulus G = 30000 MPa.
Part D
dD = 170 mm
tD = 7.5 mm
The CHS is changed so that the thickness is
now 1.5tD but
the diameter dD is
unchanged. The material is changed to steel which has a
density of 7850 kg/m3 and a shear
modulus G = 70000 MPa.
What twisting moment (in kNm) will cause a maximum shear stress
of 105 MPa?