18380 - Mechanics of Machines and Mechanical Controls L

Learning outcomes

The course of study will provide students with the basis knowledge necessary to treat and solve, by means of mathematical methods, classical problems of kinematics, kinetostatics and dynamics.

Students will learn the fundamental methodologies that allow one to tackle major technical problems regarding the functioning and modeling of the principal devices suited to power transmission, as well as the connection between driving and operated machines.

Furthermore, they will learn to interpret and provide technical information through the language of the mechanical technical drawing.

Course contents

PART I: KINEMATICS AND KINETOSTATICS OF MULTIBODY SYSTEMS

1. Kinematics of a point
   Position, velocity and acceleration: intrinsic and Cartesian representations.
2. Kinematics of a rigid body
   Degrees of freedom (dof). Position, velocity and acceleration. Instantaneous rigid motions. Particular finite motions. Planar motion: instantaneous centre of velocity, centrodes, Rivals' Theorem. Examples: wheel on a rail, cylindrical roller bearing.
3. Kinematics of multibody systems
   Composition of mechanisms. Kinematics pairs. Computation of the dof .
   Kinematics of planar single-dof mechanisms: loop-closure equations; position, velocity and acceleration analyses; singularities. Examples: centred slider-crank linkage, four-bar linkage, outline on the single and double Cardan joint.
4. Kinetostatics of multibody systems
   Systems of applied vectors. Forces and couples. Reduction of force systems. Constraint reactions. Equations of static equilibrium. Equilibrium of planar systems of two, three and four forces. Exercises of graphical force analysis.
   D'Alembert's principle and inertia forces. Kinetic energy. Dynamically planar motions. Energy equation, principle of virtual work and Lagrange's equations. Kinetostatic and dynamic analysis of statically determinate and indeterminate mechanisms.
   Kinetostatic analyses of the slider-crank linkage and the four-bar linkage: graphical solution, free-body diagrams, division of the mechanism into unclosed kinematic chains, Lagrange's equation.
5. Dissipative actions in machine components
   Static and kinetic friction. Rolling friction. Modelling of friction in kinematic pairs. Outline on lubrication. Equilibrium of a vehicle in planar motion.
   Efficiency in direct and inverse motion. Machines arranged in series and in parallel.

PART II: CONSTANT-SPEED-RATIO POWER TRANSMISSION DEVICES

1. Gearing
   Constant-speed-ratio motion transmission between parallel shafts and concurrent shafts. Friction gears.
   Gear types. Involute spur gears: geometry, proportions and standards, interference, manufacture of gear teeth, nonstandard gear teeth, force transmission. Outline on involute helical, bevel, hypoid and worm gears. Ordinary and planetary gear trains.
2. Motion transmission by means of flexible elements
   Winches and hoists. Flat belt, V belt, synchronous belt and chain drives.
3. Couplings
   Rigid, flexible and mobile couplings.

PART III: VARIABLE-SPEED-RATIO POWER TRANSMISSION DEVICES

1. Design of the output motion
   Types of output displacements. Acceleration diagram. Velocity, acceleration and couple coefficients. Elementary and complex motions.
2. Linkages
   Single-dof planar linkages: RRRR, RRRP and RRPP kinematic chains.
3. Cam mechanisms
   Classification. Kinematic and kinetostatic analyses. Pressure angle. Undercutting. Force and form joint closure.
   Intermittent motion mechanisms: freewheels, Geneva mechanism, indexers.
4. Clutches and brakes
   Positive and friction clutches. Disk and drum brakes.

PART IV: DYNAMICS OF MACHINES

1. Connection between motor and operating machine
   Reduction of forces and inertias. Steady-state characteristics of driving machines and operating machines. Steady-state behaviour. Regulation of speed. Thermal problems for electric motors. Selection and verification of motors, gearboxes and gearmotors. Examples: translating saddle drive, rotary table drive.
2. Dynamics of single-dof machines
   Study of a start-up transient. Selection of a brake motor and study of the braking transient.
3. Vibrations of single-dof systems
   Free and forced vibrations. Isolation of vibrations. Rotor dynamics: static and dynamic unbalance, critical speeds of shafts.

PART V: MECHANICAL DRAWING

1. Introduction to mechanical drawing
   Standards. Methods of representation. Orthographic projection. Sections. Conventional representation of machine components. Dimensioning. Tolerances. Surface texture.
2. Fastening of mechanical elements
   Classification and working principles. Threaded fasteners. Shaft-hub connections. Rivets, welding and bonding. Mechanical springs.
3. Bearings
   Sliding-contact bearings. Rolling-contact bearing: roller bearings, ball screws, linear guiding systems.
4. Mechanical transmissions
   Assembly drawings. Examples of complex mechanical transmissions: couplings, gear trains, clutches brakes.

Readings/Bibliography

• Theory of Machines and Mechanisms.
  J. J. Uicker, G. R. Pennock, J. E. Shigley. Oxford University Press (ISBN 019515598X).
• Mechanics of Machines.
  W. L. Cleghorn.  Oxford University Press (ISBN: 0195154525).
• Drive Engineering - Practical Implementations: project planning of drives .
  Sew-Eurodrive Documentation. http://www.sew-eurodrive.com.
• Engineering Design Graphics (chap. 10, 14-18, 20-21, 23).
  J. H. Earle. Prentice Hall (ISBN 0-13-142573-0).

Teaching methods

The course of study is based upon theoretical lectures covering the subjects on the syllabus and more practical classes proposing applicative examples.

Assessment methods

Learning assessment consists of a written test and an oral examination, based respectively on the solution of applicative exercises and the discussion of subjects treated in the lectures.

Teaching tools

Notes written by the professor in charge of the course (in italian).

Office hours

See the website of Marco Carricato