00687 - Mechanics of Machines

Learning outcomes

The course provides the fundamentals for the kinematic, static, and dynamic analysis of mechanical systems of the type commonly found in machinery.

Course contents

Introduction.

Terminolgy of Mechanism Theory: Definition of machine. Kinematic chains and mechanisms. Kinematic pairs. Mobility analysis. Gruebler criteria.

Kinematics of a rigid body: The relative instantaneous center. Kennedy-Aronhold Theorem. Velocity and acceleration relationships.

Kinematic analysis of mechanisms: The four bar mechanism. The slider-crank mechanism. 2R planar manipulator. Closed-loop and Open-loop mechanisms. Graphical Kinematics: velocities and accelerations. Analytical Kinematics of planar mechanisms.

Machine's Efficiency: Principle of Tribology. Contact forces. Efficiency. Friction. Coulomb friction. Coefficient of friction. Wear. Reye principle. Rolling friction.

Statics and Dynamics: The free-body diagram. Superposition. Graphical force analysis. Analytical Statics.  Calculating Reactions. The Principle of Virtual Work. Kinetic Energy. D'Alembert principle and Inertial forces. Lagrange's equations.

Static analysis of mechanisms: Ideal (workless) constraints. Reaction in ideal mechanisms. Static effects of friction. Slider friction. The inclined plane (ramp). Efficiency of the screw. Friction in hinge joints. Problems.

Gears: Fundamental law of Gearing. Spur Gears and helical gears. Gear Tooth forces. Gear trains. Planetary Gear trains.

Pulleys: fixed and movable pulley; pulley system; block and tackle.

Belt drives: flat belts; trapezoidal belts.

Reciprocating engine dynamics: inertial forces; bearing reactions; balance of slider-crank machines.

Flywheel calculations.

Mechanical vibrations: Single dof model. Free response and forced response of the single dof system. The seismograph and the accelerometer. Vibration isolation.

Balancing of machinery: balance of rigid rotors.

Readings/Bibliography

1. FUNAIOLI E., MAGGIORE A., MENEGHETTI U.,

Lezioni di Meccanica Applicata alle Macchine. Prima parte: Fondamenti di Meccanica delle Macchine, ed. Pàtron, Bologna.

2. Callegari M., Fanghella P., Pellicano F., Meccanica Applicata alle Macchine , CittàStudi, 2013.

3. Doughty S., Mechanics of Machines, John-Wiley & Sons, 1988.

4. C. E. Wilson, J. P. Sadler, Kinematics and dynamics of machinery, Prentice Hall, 2003.

5. Copy of the slides.

Teaching methods

The course is based on lectures dealing with the theoretical aspects of the course topics and application examples.

Assessment methods

The final examination is oral and consists of three questions that aim to ensure the acquisition of knowledge expected by the course program and to assess the achievement of learning objectives:

• knowledge of the functional principles of machines and mechanisms;
• ability to solve simple problems of kinematics, kinetostatic and dynamics of planar mechanisms.

In the course of the examination it will be assessed the ability of the student to resolve new problems or at least to set up the correct resolutive strategy. The assessment of such ability has a fundamental weight in the attribution of the final marks.

To be admitted to the oral examination, students must successfully pass a short 30-minute written test. During the test it is not allowed to use books, notes, calculators, or electronic media. A typical example of a test is available: http://diem1.ing.unibo.it/mechmach/rivola

Teaching tools

Blackboard, PC.

The teaching materials (diagrams and slides) is available on: http://campus.unibo.it/

Username and password are reserved for students enrolled at the University of Bologna.

Links to further information

http://diem1.ing.unibo.it/mechmach/rivola/

Office hours

See the website of Alessandro Rivola