OVERVIEW

Fundamentals of mechanics of machines: principles, kinematic and dynamic laws, mechanical components.

AIMS AND CONTENT

LEARNING OUTCOMES

Fundamentals of kinematic, static and dynamic analysis of machines. Dynamic models at 1 g.d.l. Basic mechanical components: bearings, sprockets, ropes, belts, chains, couplings, clutches, brakes. Applications in industry.

AIMS AND LEARNING OUTCOMES

The Applied Mechanics for Machines course aims to provide operational concepts regarding the functionality of mechanical systems used in industrial contexts. By the end of the course, students will have acquired knowledge of the fundamental issues related to industrial mechanical systems.

Specifically, students will be able to:

• Understand the phenomena related to the kinematics, statics, and dynamics of machines.

• Evaluate the mechanical characteristics of the basic components of industrial transmissions.

TEACHING METHODS

The course consists of 60 hours of lectures, conducted both at the blackboard and with a projector. Theoretical topics are accompanied by practical exercises.

Students with disabilities or Specific Learning Disabilities (SLD) may request compensatory/dispensatory measures for the exam. The arrangements will be defined on a case-by-case basis in collaboration with the Engineering Reference for the University Committee for Support to Students with Disabilities and SLD. Students wishing to make such a request are encouraged to contact the course instructor well in advance, copying the Engineering Reference (https://unige.it/commissioni/comitatoperlinclusionedeglistudenticondisabilita.html), without sending any documentation related to their disability.

SYLLABUS/CONTENT

Kinematics of the Material Point and Rigid Body. Cartesian and local coordinates. Bour's formula and Poisson's formula. Relative motion theorem and Coriolis theorem. Special cases of mobile frames in translational and rotational motion. Rigid body condition and planar motion. Galileo-Varignon formula and Rivals' theorem. Chasles' theorem and determination of the instantaneous center of rotation. Examples.

Definition of Kinematic Element and Kinematic Pair. Lower and higher kinematic pairs. Definition of kinematic chain and mechanism; kinematic inversion. Examples: RRRR chain and RRRP chain. Degrees of freedom of planar motion; Grubler's formula and limitations. Introduction to graphical methods. Kinematic analysis of the four-bar linkage and slider-crank mechanism: position, velocity, acceleration. Determination of the velocity pole. Resolution of the configuration problem using parametric CAD software. Examples.

Analytical Methods for Kinematic Analysis of Mechanisms. Closure equations. Position problem. Independent and dependent variables. Velocity problem. Jacobian matrix and instantaneous critical forms. Classification of mechanisms based on the velocity ratio. Accelerations problem. Examples.

Elements of Surface Mechanics. Mean roughness. Roughness parameter. Maximum surface asperity parameter. Abbot-Firestone curve. Wear: running-in wear, adhesive, abrasive, corrosive, erosive, fatigue, and pitting. Analytical models: Reye's hypothesis and Holm and Archard model. Example: wear and pressure distribution on a pad under asymmetric load. Sliding friction; Coulomb's model; friction cone, static and dynamic friction coefficients. Exercises.

Non-Ideal Elastic Bodies. Stress-strain diagram and hysteresis cycle; dissipated energy. Rolling friction; coefficient and rolling friction parameter. Comparison of dissipated energy in sliding and pure rolling cases. Equilibrium of rolling bodies.

Statics. Equivalent force systems. Varignon's theorem. Distributed loads and equivalent systems. Equations of statics. Elementary static equilibrium problems: body subjected to two and to three forces. Active forces and reactions. Types of constraints. Solution of static problems using graphical methods. Application to slider-crank mechanism. Analytical method of the free-body.  Superposition principle. Virtual work principle. Virtual power principle. Force multipliers in dead-center configurations, mechanical gain. Examples and exercises.

Efficiency. Manufacturing and construction of kinematic pairs. Prismatic pair with sliding contact: calculation of driving force and efficiency. Revolute pair: friction circle and approximate efficiency calculation. Rolling bearings: kinematic and static analysis, deformations, and load distribution.

Dynamics. Equations of motion. D'Alembert's principle. Inertia force and torque. Forward and inverse dynamic problems, examples. Dynamic model: Newton-Euler equations, power balance equation, virtual work principle. Examples.

Work and Efficiency. Mechanical work; kinetic energy theorem; stationary and periodic regimes. Efficiency in series and parallel arrangements. Power flows. Examples.

Motors and transmissions. Load-speed curves. Direct motor-load coupling, stability of operating points. Coupling with transmission: reduced equations of motion. Transient period. Periodic regime: irregularity degree. Flywheel. Exercises.

Transmission Joints. Positioning and operating irregularities. Rigid joints and connecting elements. Elastic joints. Articulated joints: universal, Oldham, Rzeppa. Homokinetic condition.

Belt Transmission. Operating principles. Tension in belt-pulley contact.

Friction Wheels. Synchronization. Involute of a circle. Geometry and types of gears. Introductioon to modular design. Gear transmission. Ordinary and epicyclic gear trains. Willis' formula. Exercises.

Vibrations. Harmonic motion. Simple harmonic oscillator. Natural frequency. Newtonian method and energy method. Free damped vibrations. Underdamped and overdamped motion. Logarithmic decrement. Forced vibrations with damping. Representation with rotating vectors. Dynamic amplification and attenuation. Examples.

RECOMMENDED READING/BIBLIOGRAPHY

Textbook:

M. Callegari, P. Fanghella, F. Pellicano. "Meccanica applicata alle macchine", 2a Ed., UTET Università, 2017.                                                                                                  

Teaching materials and solved exercises are available on AulaWeb.

TEACHERS AND EXAM BOARD

Exam Board

MATTEO VEROTTI (President)

LUIGI CARASSALE

DANIELE SIVORI

MARCO LEPIDI (President Substitute)

LESSONS

LESSONS START

https://corsi.unige.it/8716/p/studenti-orario

Class schedule

The timetable for this course is available here: Portale EasyAcademy

EXAMS

EXAM DESCRIPTION

The exam consists of a written test and an oral test, and includes the submission of the exercises assigned during the course.
The written test will focus on exercises similar to those covered during the lectures, as well as open-ended questions on the topics discussed in the course. After the written test, a partial grade (out of 30) will be provided: only students who achieve a score of 18/30 or higher will be allowed to take the oral exam.
The oral exam will complete the assessment with a discussion of additional topics covered during the course. The final grade will be based on the overall performance of the student in both the written and oral parts of the exam.
The written test has a maximum duration of 150 minutes. The date of the oral exam will be announced after the corresponding written test, along with the results of the written test, based on the number of students participating in each exam session.

ASSESSMENT METHODS

The written test aims to verify the actual acquisition of basic knowledge on the topics of Applied Mechanics, through the solution of simple exercises similar to those covered during the course, and through a concise written presentation of topics from the syllabus.
The oral test aims to complement the assessment of the student's preparation, with a discussion of one or more topics explicitly outlined in the exam syllabus.

Exam schedule

FURTHER INFORMATION

The teacher is available for detailed information.