2017 02 07

Pagina 1

Master of Science in Mechanical Engineering Politecnico di Milano Course of Machine Design 2 (Prof. S. Beretta, Prof. M. Giglio, Prof.ssa L. Vergani) Written test – 07.02.2017 Name: Surname: Polimi-ID: Exercise 1. Figure 1 shows a clamped beam with an additional support in C. The total length of the beam is 2l. Its section is characterized by an HE160_B profile. A concentrated load (P) is located at mid-span of AC segment and a sinusoidal alternate load is located in D, ܨሺݐሻ=ܨ଴݊݅ݏሺݐ߱ሻ. It is requested to: 1) Determine the diagram of internal bending moments, separately for each force component that is applied to the structure 2) Evaluate the maximum displacement in D (consider the worst configuration for F(t)) 3) Perform the fatigue assessment of the most stressed section, under the hypothesis of a notch coefficient ܭ௧ = 2. F0 = 5000 N P = 10000 N L = 2000 mm ݉௦ = 0.9, ݉ௗ = 0.73, q=0.9 Material: Fe410, UTS = 410, YS = 255 MPa Figure 1: Structure and load configuration. Exercise 2. The pin of a lug joint in a mechanical press (refer to Figure 2, left side) is designed to transmit the required load. It consists of a solid beam, which can be schematized as in the right side of Figure 2. During each press cycle, the maximum load (F) transmitted by the pin is 550 tons, while the minimum is zero. After how many years will the pin failure occur, supposing the machine will provide 55 press cycles/minute and it will be used 8h/day and 15days/month. Figure 2. (a) The entire press system; (b) drawings of the pin and (c) schematic representation of the pin for internal force calculation. Data: Material: UTS = 700 MPa Consider 107 as the threshold number of load cycles that distinguishes finite and infinite fatigue life. Exercise 3. Figure 3.a shows an infinite plate subject to an…