Exam 2022 02 16 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 – 16.02.2022 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 answers to “-1” and no answers to “0”. 1) Insert Name, Surname, ID# 2) Provide answers 3) Save as pdf 4) Return by email to [email protected] Question # Text Yes 1 The Stair Case method for fatigue testing permits to obtain: • The fatigue limit of the real component under biaxial stress state • The Wohler diagram in the low-cycle fatigue region • The fatigue limit of material at 50% probability of failure, with also the possibility to calculate the fatigue limit at different probability of failure X • None of the others Question # Text Yes 2 The fatigue notch factor Kf permitted to: • Carry out the assessment of mechanical components in plastic field • Calculate the stress-strain values in the notch region • Estimate the fatigue limit of the component in presence of geometrical change of shape/dimension X • None of the others Question # Text Yes 3 In FEM, the isoparametric formulation is required to: • Generate elements with an arbitrary shape X • Generate elements with quadratic shape functions • Avoid the shear locking • None of the other 2 Question # Text Yes 4 The presence of a single stress cycle with increased/reduced values (overload/underload) in crack propagation: • Produce a benefit in fatigue life in the case of underloads (single load with minimum stress less than the nominal one) • Produce an acceleration in crack growth rate in case of overloads (single load…