The course-module aims at preparing mechanical design engineers/analysts with particular reference to the field of machines. The intended learning outcomes are developed with the intent to develop the competences normally required in a working context.
Machine Design engineers/analysts are typically tasked with designing structural and mechanical components of machines, and the systems which these components are part of (bolted connections, transmissions, bearings, shafts, couplings, springs etc.).
At the threshold professional level the Machine Design engineers/analysts must be able to analyse an existing machine component or design modification to meet given requirements. They apply methods and use existing software according to given specifications and under the supervision of a senior engineer.
At the standard professional level the Machine Design engineers/analysts must be able to produce new designs for machine components or systems to meet specified requirements. They choose the appropriate analytical or numerical methods and use them under their own responsibility.
Aim of this course module is the threshold level, with a strong opening toward the standard level. In order to drive the students toward the desired working competences, the Program of this course-module submits to the students’ attention a number of design problems which are notable for their importance, repeated occurrence, and solution difficulty. They are purposely of a limited number to allow a sufficiently deep exploration of all the aspects which affect the performance of the mechanical component. The method of approaching these exemplar problems is meant to be easily extended to the other cases that the professionals will encounter during their working life.

Whatever the type of mechanical structure or machine, the design problem, the material, the loading and the ensuing stress and strain distribution, Machine Design engineers/analysts must know that the following is always required of them:
•investigate, define a problem and identify constraints taking account of mechanical and thermal stress conditions, functional requirements, material strength; normally with an incomplete set of information
•identify, classify and describe the mechanical performance of machine components and their assembly through the use of analytical methods and modelling techniques, whether analytical or numerical
•identify the critical weak points for strength, according to all possible failure mechanisms, evaluate uncertainties and apply the appropriate safety coefficients, assess whether the stresses are admissible
•define the shape and size of components of the machine components and their assembly, predict strength and life
•understand which are the governing parameters in a given design, propose the appropriate modifications in the form, dimensions and materials of a component or its interface in order to improve performance
•recognize the importance of standards, codes and regulations
•deploy all the appropriate arguments to approve a design, and be able to take a responsible decision based on firm grounds
•manage the design process and evaluate outcomes, i.e., be able to analyse and interpret results
•know how to check the theoretical or numerical predictions or models with appropriate experimental tests, know how to read, interpret and assess the results of test results produced by others
•be able to present, in both oral and written forms, a clear and well-structured set of relevant considerations on design assumptions and results
•be able to read, understand and comment a variety of technical material

Attendance of this module requires fluency in spoken and written english as a necessary pre-requisite: all lectures and tutorials, and all study materials will be in english. Standard mathematics for engineers is sufficient. It is assumed that students taking this course-module already has knowledge and understanding of the strength of materials principles; in detail, they know and use strain and stress tensors and their principal properties, preferably in matrix notation, their graphical representation through Mohr circles, the two and three dimensional behaviour of elastic materials, the constant force design criteria of brittle and ductile materials (maximum normal stress, maximum shear stress or Tresca, maximum distortion energy or Von Mises). Moreover they master the mechanics of forces and the dynamic of rigid bodies; as to deformable bodies, they master bar and beam problems for tension, bending and torsion, and know ensuing the cross section stress distribution. It is an advantage if students have a prior knowledge of basic machine design elements, of technical drafting and of elements of mechanical machining technologies.

Credits 8, 84 classroom hours (42 lesson hours, 42 tutorial hours). The total study load for this course-module is 200 to 240 total hours, i.e., 25 to 30 hours per credit. This includes classroom hours, self study, completion of tutorials at home and reporting.
The students will develop specific knowledge and understanding of the following subjects together with the skills and the know-how required while giving shape and dimensions to a machine component or assembly.
Subjects:
0 – Review of applied criteria for static strength of isotropic metallic materials (tutorials 3 hrs)
1 – Design against fatigue (lessons 9 hrs, tutorials 6 hrs):
- History and overview of fatigue problems
- Stress-life fatigue: basic material properties, specimen testing
- Stress-life fatigue: component fatigue
- Tutorial 1a: selection of overview exercises
- Tutorial 1b: Application to the design of gearbox shafts
2 – Bolted connections (lessons 6 hrs, tutorials 6 hrs):
- Prestressed single bolt connections (non gasketed)
- Refinements and special problems
- Elements of gasketed bolted connections
- Tutorial 2a: selection of overview exercises
- Tutorial 2b: application to an hydraulic piston or to a tie-rod connection
3 – Hertz contact and rolling bearings (lessons 9 hrs, tutorials 9 hrs):
- Hertz theory and applications
- Rolling bearings: static loading
- Rolling bearings: fatigue
- Design of bearing arrangements
- Tutorial 3a: application of Hertz theory to strength of a selection of contact cases
- Tutorial 3b: application to loading and stresses in a high speed bearing
4 – Gears (lessons 9 hrs, tutorials 9 hrs):
- Summary of motion transmission, tooth shape
- Spur and helical gears with parallel axes: kinematics, geometry, forces
- Cutting techniques and profile displacement
- Criteria for strength assessment of gears: fatigue, hertz contact, wear, scuffing
- Tutorial 4a: selection of overview exercises
- Tutorial 4b: sizing of a set of gears in a gearbox
5 – Rotating discs (lessons 6 hrs, tutorials 6 hrs):
- Summary of plane elastic fields and elastic stresses in discs and thick-walled tubes
- Plastic stresses in thick-walled tubes
- Rotating discs: elastic and plastic solutions (fatigue, thermal stresses, burst)
- Tutorial 5: numerical calculation of elastic and plastic stresses in a rotating disc, strength assessment
6 – Seminars, visits, unplanned teaching and student support (lessons 3 hrs, tutorials 3 hrs).

Tutorials
Class hours are equally shared between theoretical lessons and application tutorials, in order to achieve a balance between knowledge and skills. The course-module is organised to allow students to progress incrementally in the development of their understanding and skills, under expert supervision.
Lessons on a subject will be followed by specific tutorials, where students are required to apply knowledge to working context problems. The tutor will provide organised materials and frames for solutions. However, the student themselves will solve the proposed tasks in small groups of up to 3 individuals. For each task each group will produce a final report; the set of all reports will be examined during the final exam.
The tutor will assist the groups during the tutorial class hours, supporting students in their learning progression and clarifying doubts. Attendance to both lessons AND tutorials is strongly recommended, this being vital to achieve the intended learning outcomes. Teacher and tutor are available weekly during the teaching period to meet students for consultation; please contact them by e-mail.
Tutorials may benefit from using EXCEL or MATLAB. Writing reports with editing software is not required; handwritten reports in block letters are preferred. Students will use drawing instruments (compass, set squares, scale rulers).

Lessons: the subject is fully treated in notes and slides provided by the teacher. Reference textbooks of international standing will also be suggested.
Tutorials: texts of problems, datasheets of materials, extracts of standards and manuals will be provided by the tutor.
All materials will be made available on the course website, in the “materials” section.

Acquired learning outcomes will be assessed by means of a final exam; in order to properly assess specific subjects listed in the “Program” section together with the general learning outcomes listed in the “Expected knowledge and skills” section, the examination is composed of different sections:
a) written session, day 1:
test, duration 2 hrs 30 min, closed book, composed of three questions, two on chapters or sections of the lectures to prove knowledge, one problem to prove solving skills (drawing instruments will be needed); each question scores max 8 (eight) points; the minimum score to pass is 14 (fourteen), however each question must separately score at least 50% or 4 (four) points, which means the each question requires at least a “threshold” performance
b) oral session, day 2:
b1) preliminarily, each student is informed on the reasons for grading obtained, and may appeal with appropriate explanations
b2) students will engage in a technical discussion proposed by the teacher, to show that knowledge and understanding of the course-module subjects has been acquired: max additional 4 (four) points
b3) students will submit the full set of tutorial reports to the tutor, who will investigate effective personal acquisition of implied skills: max additional 4 (four) points