INFORMAZIONI SU

Applied Mechanics - 2nd module (the English translation of "Meccanica applicata alle macchine II")

Applied Mechanics - 2nd module (traduzione in inglese del programma di Meccanica applicata alle macchine II) - cdl in Ingegneria Meccanica

Teacher

prof. Alessandro GASPARETTO

Credits

6 CFU

Language

Italian

Objectives

The course provides the basic concepts of applied mechanics, such as: principles of tribology, principles of motor-load coupling, steady and transient state of operation for a machine, properties and characteristics of mechanical transmissions and machine components.

Acquired skills

- Ability to model a mechanical system in the presence of friction.
- Ability to select the motor to be coupled to a mechanical load.
- Ability to select and size the transmission and other components of a mechanical system.

Lectures and exercises (topics and specific content)

Contact mechanics: introduction to the course; notes on the mechanical characterization of materials; contact between solid bodies,  phenomenology physical and Hertz’s model; adhesion and friction; modeling of the phenomenon according to Coulomb, results from experimental tests and application examples; rolling friction; wear, Holm’s model and Reye's hypothesis; friction in prismatic pairs; friction in revolute pairs, circle of friction; application examples (10 hours).
Motor-load coupling: energy balance of a machine; absolute regime, transient regime, periodic regime of a machine; efficiency of a machine; reversibility of the motion; motor-load coupling; mechanical characteristic of the motor and of the load; direct coupling, calculation of the operating point; motor-load coupling through speed reducer, calculation of the operating point; case of load in rectilinear motion; stability of the steady state; mechanical transient; calculation of the startup time; dynamic analysis of the transient in a motor-load system; torques and inertias reduced to the motor axis and to the load axis; effect of the change of the transmission ratio on the operating point at steady state; criteria for selection of the motor and of the reducer; gears; static adaptation of the motor to the load; most common laws of motion; dynamic adaptation of the motor to the load; periodic regime; inertia reduced to the free coordinate; calculation of the velocity within a machine cycle; design of the flywheel; static and dynamic balancing of rotors; balancing of a rod-crank mechanism with the method of the substituted masses (20 hours).
Mechanical transmissions and other machine components: friction wheels; spur gears with straight teeth; spur gears with helical teeth; conical gears; transmissions screws; odinary gears planetary gears; Willis’s formula; conical planetary gears, differential for motor vehicles; transmission of motion through belts; flat belts, V-belts and timing belts; traction winches and capstans; chains for the transmission of motion; comparative evaluation of the characteristics of the main mechanical transmissions; the Cardan joint; the double Cardan joint; the Rzeppa and Bendix-Weiss joints; screw-and-nut transmissions; applications to lifting equipments; discussion on the reversibility of the motion; lifting winches and hoists; clutches; dynamic analysis and calculation of the dissipated energy in a clutch; calculation of the pressure in the contact area of a clutch; brakes, types and parameters; roller bearings, classification and criteria for selection (25 hours).
Mechanical vibrations: free response of a simple oscillator; frequency response of a simple oscillator; mechanical resonance (5 hours).

References

- Appunti delle lezioni
- Dispense sul sito del materiale didattico
- M. Giovagnoni, A. Rossi, Una introduzione allo studio dei meccanismi, Ed. Cortina, Padova

Type of exam

Written and oral

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