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.

Terminology 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.

Balancing of machinery: balance of rigid rotors.

Flywheel calculations.

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

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 (Terza Edizione), CittàStudi, 2022.

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. Additional materials: Lecture slides are made available before class at https://virtuale.unibo.it/, along with exam examples, exercises, figures, and/or animations.

The book (2) is available in digital form: www.pandoracampus.it
See instructions on: sba.unibo.it

Teaching methods

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

Class attendance, although not mandatory, plays a fundamental role in the learning and evaluation process.

Assessment methods

The exam is taken through the Esami On Line platform Esami On Line (EOL). General guidelines, information on the examination structure, and the rules to be observed are available at https://virtuale.unibo.it.

The final exam is written and consists in solving three problems 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.

During the examination, the use of textbooks, notes, or other written materials is not permitted. Access to online learning resources is prohibited.

The use of Artificial Intelligence (AI) tools is strictly forbidden. Any such use constitutes a violation of academic integrity.

Students are advised to use a non-programmable pocket calculator.

The examination lasts two hours and covers three categories of topics. Each category consists of a number of multiple-choice questions and/or short-answer questions and is assigned a maximum score of 11 points.

The examination is deemed passed only if the candidate obtains at least 6 points in each category.

If the total score exceeds 30 points, the final grade will be awarded as 30 cum laude (30L), recognizing an outstanding level of understanding and mastery of the course material.

For students who have " Mechanics of Machines and Materials (Integrated Course)" in their study plan, the overall grade of the Integrated Course will be recorded once both the "Mechanics of materials and structures" examination and the "Mechanics of Machines" examination have been passed. The overall grade will be calculated as the average of the grade obtained in the two individual exams (the evaluation of "30 with honors" obtained in one of the individual exams is equivalent to 31). If this average is greater than or equal to 30, the final grade will be "30 e lode". If the average is a semi-integer number, the final grade will be obtained by rounding up the average.

The order of the two exams is irrelevant. The results of the two exams do not expire.

In accordance with the University Didactic Regulations, students may request the cancellation of a positive grade and retake the examination. The following rules apply:

• a positive grade may be cancelled only on the day of the examination;
• a cancelled grade cannot be reinstated under any circumstances;
• each student may request grade cancellation only once during the course.

 

 

Teaching tools

Blackboard, PC.

On the E-learning Platform (https://virtuale.unibo.it), students may find: slides of the course lectures; exercises and application examples.

Office hours

See the website of Alessandro Rivola