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ENGR5004 / Week 3
Old spec Statics Session 5 Example 1TutorialOld spec ENGR216Third4 min

ENGR216 (old spec) Statics session 5 worked example 1 (slide 8) official answers

A steel bar of rectangular cross section, 20 mm wide and 64 mm deep, is subjected to two equal and opposite couples MM acting in the vertical plane of symmetry of the bar (pure bending about the horizontal centroidal axis). Determine the value of MM that makes the maximum stress equal to the allowable stress of 250 MPa.

Bar loaded by equal and opposite end couples M and M' in its vertical plane of symmetry; cross section 20 mm wide by 64 mm deep.
Bar loaded by equal and opposite end couples M and M' in its vertical plane of symmetry; cross section 20 mm wide by 64 mm deep.
Formulas you may need
  • Pure bending: σx=−MyI\sigma_x = -\dfrac{My}{I}, σmax=∣M∣cI\sigma_{max} = \dfrac{|M|c}{I} (on the formula sheet)
  • Rectangle I=bh312I = \dfrac{bh^3}{12} (on the formula sheet)