STRUCTURAL DRAWING AND DESIGN (UNIT 2)
Learning outcomes of the course unit
Knowledge and understanding:
Upon completion of the course, students will have acquired fundamental knowledge relating to the mechanics of elastically deformable bodies, with specific attention to beam theory.
Students will be capable of designing and performing structural verification of simple elements, with specific emphasis on mechanical components.
Students will have the skills to critically evaluate the stress state of simple mechanical components and therefore to assess their suitability for meeting specific load requirements during use.
Students will have the ability to clearly present technical reports relating to dimensioning of simple structural elements.
Students will be capable of assessing the adequacy, or lack thereof, of component geometry and materials in meeting load requirements during use. Students will also be able to identify alternatives in terms of geometry and/or materials to satisfy structural requirements in working conditions.
Knowledge and understanding:
At the end of the course, students will have acquired the basic knowledge of the mechanics of deformable elastic bodies, with particular reference to the technical theory of beams.
The student will be able to perform the design and verification of some simple structural elements, with particular reference to the organs of machines.
The student will have the tools to critically evaluate the output of a structural software.
The student must possess the ability to clearly present a technical report on the design of simple structural elements.
Important prerequisites for this course are knowledge of mathematical analysis, linear algebra and physics.
It is essential to have a basic knowledge of calculus, linear algebra and physics.
Course contents summary
This course provides students with the fundamentals of mechanical component design and construction. The first part of the course reviews the most important mechanical properties of materials commonly utilised in the industrial sector. Subsequently, resolution of beams and simple isostatic rectangular structures will be covered. Definition of internal loads will then be presented, together with area geometry. These two themes will provide preparation for the subsequent phase in which internal stresses in solids and beams will be calculated.
In the final part of the course, topics covered up to this point will be exploited to perform verifications of simple mechanical components through definition of strength requirements and the safety factor.
Practical exercises will be given during lessons throughout the entire course, covering all of the treated topics.
The course aims to provide a unified treatment of the main aspects of the mechanical behavior of structures, referring mainly to the linear elastic response but also with nods to the behavior beyond the elastic limit.
The first part of the course is devoted to the evaluation of the static schemes and strain in elastic solids under assigned external actions. Structural theories for beams and the evaluation of the load bearing capacity of structures will subsequently be addressed.
Specific themes covered within the course include:
1. Fundamental principles of mechanics. Static equilibrium equations. Introduction to the most commonly used industrial materials. Linear-elastic behaviour.
2. Constraints, free-body diagrams, calculation of constraint reaction forces for bodies comprising several elements.
3. Characteristic stress diagrams for long thin members (thin beams).
4. Area geometry
5. Internal stresses
6. Stress state and strength criteria for ductile and fragile materials.
7. Component verification methods.
The applied aspect of these themes will be covered through introduction of a large number of examples and exercises to be resolved in class.
The topics covered are more specifically as follows.
Basic principles of mechanics. Fundamental equations of statics.
Constraints, Free Body Diagrams, calculation of constraint reactions in variously articulated bodies.
Diagrams of stress characteristics in elongated bodies (slender beams).
Stress tensor. Strain tensor. Mohr’s graphical representation. Strength criteria for ductile and brittle materials.
Constitutive relations. Linear elastic constitutive relation. Thermal variations.
De Saint Venant problem. Normal stress. Twist. Simple bending. Shear flow.
Technical theory of beams. Calculation of the elastic curve under the most varied load conditions. Solution of statically undetermined structures.
Notes on buckling. Euler beam.
The application aspect is taken care of through the introduction of a large number of solved examples and exercises.
Slides used throughout the course will be available to students in PDF format via the Elly online platform, together with all teaching material and practical exercises covered during lessons. To download this material, students must log on to Elly and register for PROGETTAZIONE E DISEGNO DI COMPONENTI INDUSTRIALI (2° MODULO).
Further to material provided within the course, students can expand upon covered topics by studying from the following texts (in Italian):
1. C. Comi, L. Corradi Dell’Acqua – Introduzione alla Meccanica strutturale – McGraw Hill
2. F.P. Beer, E.R. Johnston, J.T. De Wolf, D.F. Mazurek – Meccanica dei Solidi – McGraw Hill
S. Crandall, N. Dahl, T. Lardner, An introduction to the mechanics of solids, McGraw-Hill, 1978 ISBN-13 :978-0-07-013441-6
O. Belluzzi, Building Science, Vol I, Freeman, 1973.
F.P. Beer, É.R. Johnston, Jr., J.T. Dewolf: Solid Mechanics. Elements of building science (second edition). McGraw-Hill, Milano, 2002.
L. Corradi Dell'Acqua, Structural Mechanics, Vol I, Mac-Graw Hill, 2010.
Additional material presented during the lectures.
Teaching activities will be conducted in the form of frontal lessons followed by tutorials. Themes covered in the course will be presented during lessons, both from a theoretical point of view and through practical examples. Refinement of the presented topics will be provided during subsequent tutorials, where teaching staff will provide worked solutions to practical exercises. Exercises will also be provided for students to complete a home.
We provide lectures and exercises on the blackboard. As a rule, lectures will follow as much as possible the recommended text, so that the student can critically review what has been developed in the classroom. From time to time, homework exercises will be assigned; clarification will be given during office hours.
Assessment methods and criteria
Exams will be held jointly with “module I” of the same course.
The written exam will comprise the following:
- Task 1: preparation of a technical drawing of two components based on a small assembly drawing. Further to simple graphical representation with orthogonal projections, it is necessary to indicate dimensions, surface finish and tolerances necessary for complete component functionality.
- Task 2: exercise based on a mechanical design problem where verification of structural integrity is required, together with calculation of the safety factor.
- Task 3: response to a question relating to part of the theory covered during the course (both modules I and II).
Written exams are assigned grades from 0 to 30, with the three tasks weighted 0.46, 0.36 and 0.18, respectively (tasks 1, 2 and 3).
Written exam results are published on esse3, usually within 2/3 days of the exam date. All students that do not achieve a pass grade can view their marked exam through appointment with the course coordinator.
Where a grade equal or greater than 18/30 is achieved, the exam is considered passed and the grade can be directly confirmed and reported.
Where a grade equal or greater than 16/30 is achieved, it is possible to undertake an oral exam with the possibility of increasing or decreasing the grade achieved in the written exam.
The written exam only gives access to the oral exam immediately following. The oral exam can only be undertaken within the date indicated on esse3 and cannot be postponed to a later date.
The exam is based on a written test and an oral test. In the written test, the student will be asked to solve a few exercises of the same type as those carried out in the classroom during recitation. The oral test will be aimed at verifying the learning of the basic theoretical knowledge.
It is strongly recommended to attend the course.