Academic Year 2018/2019 - 1° Year

ING-IND/13 - 6 CFU - 1° Semester

Teaching is divided into two parts. In the first part the basic concepts of mechanics applied to machinery are provided; in the second part the mechanical vibrations of systems with one and two degrees of freedom are studied.

1. GENERALITY ON MECHANISMS Machines and mechanisms, kinematic pairs, degrees of freedom of the kinematic pairs, degrees of freedom of planar and spatial mechanisms. 2. EFFICIENCY. Definition of mechanism efficiency, in series and in parallel efficiency, inverse motion. 3. FRICTION AND WEAR. Coefficient of friction and work, notes on the theory of sliding friction, rolling friction, friction circle. Examples: revolute pair, inclined plane. Contact pressures distribution and Reye's hypothesis. Applications: flat sliding pair, turning pair, disc brake, contact brake-pulley and brake drum. 4. GEAR WHEELS. Friction gears, conjugate profiles, primitive and fundamental circles, definition of involute of a circle. Spur gears and relative dimensioning, determination of the arc of action, non-interference condition. Spur gears with helical teeth, determination of the arc of action. Hints on bevel gears. 5. Gearboxes. Ordinary gearboxes, planetary gears and Willis’ formula, automotive differential. Examples and exercises on gearboxes. 6. FLEXIBLES. Lifting devices, elastic and inelastic stiffness, friction in the pivots, lifting hoists, pulley block.

MECHANICAL VIBRATIONS

1. ONE DEGREE OF FREEDOM VIBRATING SYSTEMS: FREE OSCILLATIONS. General information on mechanical vibrations, free elementary oscillator, equivalent systems, springs in series and in parallel. Examples. 2. ONE DEGREE OF FREEDOM VIBRATING SYSTEMS: DAMPED OSCILLATIONS. Elementary damped oscillator, critical, hyper-critical and sub-critical damping, method of the logarithmic decrement. Examples. 3. ONE DEGREE OF FREEDOM VIBRATING SYSTEMS: FORCED OSCILLATIONS. Elementary forced oscillator, amplification factor, Argand-Gauss plane representation with rotating vectors. Applications: Foundations, constraints displacement, seismographs and accelerometers. 4. ONE DEGREE OF FREEDOM VIBRATING SYSTEMS: TORSION OSCILLATOR. Elementary torsional oscillator, trees arranged in series and parallel, reduction of the rotating masses. Examples.

1. Funaioli E., Maggiore A., Meneghetti U., “Lezioni di Meccanica Applicata alle Macchine – Vol. 1”, Pàtron Editore.

2. Jacazio G., Piombo B., “Meccanica Applicata alle Macchine – Vol.2”, Levrotto & Bella Torino.

3. Diana G., Cheli F., “Dinamica e vibrazione dei sistemi”, Utet Libreria.