2016 09 20

Page 1

Exercise 2. Consider the case presented in Exercise 1 and the loads previously evaluated. 1. Design the bolt connection (select the bolt nominal diameter), considering: a. only torsion (neglect bending moment) b. friction joint (f=0.2) c. bolt class 10.9 d. number of bolts ݊௕ൌ4 e. bolts are located on a circumference with diameter db = 100 mm, as in Figure 2. 2. Which is the effect of the bending moment on the bolt assessment? Figure 2 – Scheme of the beam. 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 – 20.09.2016 Name: Surname: Polimi-ID: Do not write here 1 2 3 4 TOTAL Exercise 1. Consider three shafts, linked together by means of circular bolted flanges as schematized in Figure 1. The shafts are grounded by means of four bearings and, after bolt connection at the central flanges, they can be assimilated to a single beam. The beam is subjected to a torque T, provided by the engine. Owing to an accidental damage, located at the mid-span of the central shaft, an unbalanced force F is generated. Data: F = 1500 N T = 1200 Nm Span: l = 700 mm Material: Al E = 70 GPa Shaft cross- section: circular (d = 60 mm) Figure 1 – Scheme of the beam. 1. Evaluate the diagrams of internal forces (only torsion and bending moments) 2. Perform a displacement-based assessment at the point of force application: ൑݈800ൗ 3. Considering the same cross-section geometry, size the shaft in order to reduce the maximum deflection by 20%. Exercise 4. Describe the effect of an overload or subsequent overloads on the fatigue life of a cracked component. Master of Science in Mechanical Engineering Politecnico di Milano Course of Machine Design 2 (Prof. S. Beretta, Prof. M. Giglio,…