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22-Mec-B9 Advanced Engineering Structures: May 2018

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

  1. Question 1 Thermal stresses in a restrained two-segment rod
  2. Question 2 Crack growth life and the inspection interval
  3. Question 3 Shear centre and shear flow in an idealised wing box
  4. Question 4 Coffin–Manson fit and Miner’s cumulative damage rule
  5. Question 5 Torsion of a three-cell thin-wall box
  6. Question 6 Shear flow and bending stresses in a closed trapezoidal beam
  7. Question 7 Yield prediction by the Tresca and von Mises criteria
  8. Question 8 Shear flow, shear centre and torsion of an open I-section

Start with Question 1 →

Paper format. National Exams, May 2018 — 16-Mec-B9 Advanced Engineering Structures. Three hours, open book, any non-communicating calculator permitted. Eight questions are printed, each worth 20 marks, and the rubric states that any five constitute a complete exam paper. All eight are worked here. Marks for the individual parts are those printed inside each problem.

Reference texts. T. H. G. Megson, Aircraft Structures for Engineering Students, 6th ed. (thin-walled open and closed sections, shear flow, shear centre, multi-cell torsion, crack growth and Miner cumulative damage); A. P. Boresi and R. J. Schmidt, Advanced Mechanics of Materials, 6th ed. (yield criteria, unsymmetrical bending, torsion of non-circular sections, shear centre); N. E. Dowling, Mechanical Behavior of Materials, 4th ed. (Paris law, Coffin–Manson, Palmgren–Miner); R. C. Hibbeler, Mechanics of Materials, 10th ed. (statically indeterminate axial members, thermal stress).

Check: the modulus printed for rod (2) in Question 1. The paper prints E2 = 95,000 GPa. No solid has a Young’s modulus of that order — diamond, the stiffest bulk material known, reaches about 1,200 GPa — so the value as printed is not physically realisable and is almost certainly a units slip for 95,000 MPa = 95 GPa, a figure entirely typical of an aluminium alloy and consistent with the way E1 = 150 GPa is written on the same line. Question 1 is therefore worked at E2 = 95 GPa, and the answers obtained by taking the printed number literally are carried alongside in the results table, because the two readings give opposite answers to part (b). Under the paper’s own instruction 1, a candidate should record this assumption with the answer script.