Exam 2023 06 28 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 – 28.06.2023 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 About the fatigue crack propagation, indicate which of the following is CORRECT: • Paris law is able to describe the fatigue crack growth process in the stable zone without the effect of loading ratio R X • Stress Intensity Factor changes when load changes in time only if the frequency of the cycle is very low • The value of ∆𝐾𝑡h is experimentally determined by static test to fracture • Walker law can don’t take loading ratio R into account Question # Text Yes 2 In FEM, which of the following sentences can introduce the difference between beam elements and bar/truss elements? • Beam and Bar/Truss elements are perfectly equivalent from the application point of view, but Bar/Truss elements have a more efficient formulation to save computational time • Beam elements can withstand all types of load, while Bar/Truss elements can withstand only axial load X • Bar/Truss elements can withstand all types of load, while Beam elements can withstand only axial load • Beam elements differently to the Bar/Truss elements are able to be applied for elasto-plastic analysis Question # Text Yes 3 When assessing groove welds subjected to multi-axial stress states (for example, butt or tee joints), an equivalent stress to be compared with the limits from the standards can be computed by • Comparing the maximum principal stress in the structure with…