Exam 2024 07 12 WT2 solutions

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1 Master of Science in Aeronautical Engineering Politecnico di Milano Course of Machine Design (Prof. M. Giglio) Written test 2 –12.07.2023 Name: Surname: Polimi-ID: Do not write here TOTAL Instructions For each of the following 8 questions, select the right answer among those provided, by adding the symbol “x” as appropriate in the yellow-colored cells. Correct answers correspond to “+1”, wrong and no answers to “- 0.5”. Question # Text Yes 1 Considering the different Design Criteria: • Fail Safe criterion considers very high safety factors to avoid failures • Safe Life criterion is based on Fracture Mechanics application • Damage Tolerance approach is useful for assessment of components designed for infinite life • Damage Tolerance approach permits to evaluate the residual life and the inspection intervals X Question # Text Yes 2 Regarding FEM, select the CORRECT sentence among the following: • Due to the isoparametric formulation, results obtained with any kind of element’s shape are good • The use of truss elements permits to take into account the axial force and bending moment effects • Within an element, the shape functions link the displacement field with the strain field • Distributed loads are converted into equivalent loads at nodes X Question # Text Yes 3 The yield stress of a ductile material is generally __________ as compared to fatigue strength for infinite life • Higher X • Same • Lower • Negligible 2 Question # Text Yes 4 Consider a shear bolted joint where the bolts are subject to both shear and axial static stresses. What is the assessment criterion recommended by the standards? • sigma/sigma_b_adm< sigma_yield / sigma_VonMises • sigma_UTS / sigma_VonMises > 1 • sigma_yield / sigma_VonMises < 1 • (sigma/sigma_b_adm)^2 + (tau/tau_b_adm)^2 < 1 X…