Exam 2022 09 06 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 – 06.09.2022 Name: Surname: Polimi-ID: Do not write here TOTAL Instructions For each of the following 8 questions, select the right answe r 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 About the design criteria, indicate which of the following is CORRECT: • Safe life design is commonly applied for infinite life components with no damages allowed X • If you consider the fatigue assessment, the static assessment is not needed due to lower safety factor in any application • Safe Life criterion is based on Fracture Mechanics application • Presence of defects is not considered in the damage tolerance approach Question # Text Yes 2 Regarding FEM, select the CORRECT sentence among the following: • Distributed loads are converted into equivalent loads at nodes X • It can be modelled as a plane problem if the structure has a constant thickness • Within an element, the shape functions can build the relationship between the displacement field and the strain field • Due to the isoparametric formulation, results obtained with any kind of element’s shape are good Question # Text Yes 3 The Stair Case method for fatigue testing permits to obtain: • The fatigue limit of the real component under biaxial stress state • 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 • The Wohler diagram in the low-cycle fatigue region • The simplified fatigue limit of material based on static strength data of the material 2 Question # Text…