Machine Design prepares engineering students to design and identify how a system consisting of fixed and moving parts – the so–called "machine" – can convert and transmit the energy in the best way to be suited for a specific application. By the end of the semester the student will be able to deal with functional requirements and design specifications, to use a variety of existing mechanical components and devices and their most appropriate domain of application, to determine the shape and size of the machine components and to predict their strength and life, to choose the materials best suited for the application, to take into account up-to-date standards or codes of practice and technological constraints, to employ some suitable analytical models and numerical tools, to deploy the whole design process, and to be able to take a responsible decision based on the best current practice.

Foreword: Machine Design engineers/analysts are typically tasked with designing structural and mechanical components of machines (bolted connections, transmissions, bearings, shafts, couplings, springs, etc.) and the assembled systems which these components are part of. 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.
As a consequence this Subject Module aims at competences at the threshold level through the study of a selection of representative and complementary classes of problems each requiring a specific treatment (Contents 1 to 5), and introduces students to the standard level by exposure to a semester-long Technical Project where an assembled machine is examined and design alternatives are proposed and compared.
In order to develop the required competences applicable to any type of mechanical structure or machine, students are required, by the end of this subject module, to show achievement of the following main points of knowledge:
- know the theory, and the experimental evidence in support, which underpin the mathematical models of mechanical components
- 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
- analyse an existing machine component to check whether it meets given requirements
- identify the governing parameters in a component design, define the shape and size of machine components, know how to introduce appropriate design modifications to improve strength and life or to upgrade specifications; this may extend, in some selected cases, to propose new designs for machine components or systems while taking full responsibility to that
- analyze the mechanical performance of interacting components assembled in a machine, i.e. kinematics, exchanged loads and stresses by means of analytical methods and modelling techniques, whether analytical or numerical
- identify among technical solutions compatible with the state-of-art of the availble technologies a suitable architecture and/or mechanism to convert and transmit energy to be exploited in the design operation
- know their theoretical background of the relevant standards, codes and regulations which are used in the field and skills:
- correctly read the mechanical drawing of a machine or its subsystem, identify parts and their assembly, understand constraints taking account of mechanical and thermal stress conditions, functional requirements, material strength
- be able to propose more ways to assemble components into a mechanical system to achieve the same function
- be able to apply the theory and the mathematical models to component and machine designs
- indentify which data are needed to a design, and where they can be found
- deploy the appropriate reasoning to approve a design, and be able to take a responsible decision based on evidence
- know how theoretical or numerical predictions or models can be checked with appropriate experimental tests
- 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 technical material from books, manuals and any other source.

Attendance of this module requires fluent spoken and written English as a necessary pre-requisite: all lectures and tutorials, and all study material will be in English. Standard mathematics for engineers is sufficient. It is assumed that students taking this subject-module already have 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 would be an advantage if students would have a prior knowledge of basic machine design elements, technical drawing and elements of mechanical machining technologies.

1 – The design process: methods, goals, activities. Needs, requirements, constraints, innovation targets. Tools and examples of design of systems and machines. Outlines of related standards. Concept, synthesis, verification and validation. Safety and reliability. Functional, operational and architectural requirements. Role of standards, best practices and modelling activity in design. Example of deployment of the whole design process (3 hrs., lecture; application to the subject of the Technical Project, 1.5 hrs. tutorials)
2 – Fundamentals of machine design: Review of applied criteria for static strength of isotropic materials (reading material provided; tutorial 3 hrs)
3 – Design against failure: fatigue and fracture (lectures 9 hrs, tutorials 9 hrs):
- Overview of fatigue problems (reading and self instruction, material provided)
- Stress-life fatigue: basic material properties, specimen testing and specimen fatigue (ref. to FKM standards)
- Stress-life fatigue: component fatigue, finite and infinite life (ref. to FKM standards)
- Stress-life fatigue: thermal effects and thermomechanical fatigue behaviour, relation with creep and other effects
- Crack propagation: linear fracture mechanics, basics, applications, Paris law
- Tutorials: use of the main fatigue diagrams; application of FKM standards; notch effect; application to the Technical project; fracture mechanics: computation of crack propagation and path.
4 – Design of assemblies: supports and bearings (lectures 9 hrs, tutorials 9 hrs):
- Contact mechanics and damage (reading and self instruction, material provided)
- Rolling bearings: static loading, fatigue conditions
- Design of bearing assemblies, main solutions for bearing arrangements
- Tutorials: application of Hertz theory on a selection of contact cases; angular contact bearings, preload diagram; load-life rating of
the bearings for the Technical Project; bearing assemblies and related problems
5 – Design of power transmission: gears (lectures 9 hrs, tutorials 9 hrs):
- Summary of motion transmission, tooth shape (reading and self instruction, material provided)
- 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
- Tutorials: geometry and kinematics of gears, spur gears profile shift, design of the gears of the Technical Project
6 – Design of joining systems: bolted connections (lectures 6 hrs, tutorials 6 hrs):
- Threaded fasteners and connections (reading and self instruction, material provided)
- Prestressed single bolt connections (non gasketed)
- Refinements and special problems
- Elements of gasketed bolted connections
- Tutorial: selection of overview exercises
- Tutorials: application to a hydraulic piston or to a tie-rod connection
7 – Advanced topics: overview of some widely-used technologies based on the electromechanical energy conversion and multiphysics modelling in designing systems and machines. Adaptive systems. Role of the product scale. Special, functional and new materials. Examples and current applications. (Seminar lecture 3 hrs.)
8 – Seminars, visits, unplanned teaching and student support (lectures 1.5 hrs, tutorials 3 hrs).

Credits 8, 81 classroom hours (40.5 lecture hours, 40.5 tutorial hours). The total study load for this subject 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.
Class hours are equally shared between theoretical lectures and application tutorials, in order to achieve a balance between knowledge and skills. The subject is organised to allow students to progress incrementally in the development of their knowledge and skills under expert supervision.
All lecture materials will be made available on the subject unit website before the class activity. Students are urged to download or print them so to have them at hand to take notes.
Lectures on a section of the material 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 students will solve the proposed tasks themselves in small groups (max 3 students)
Moreover, there will be a semester-long project, the so – called "Technical project": in order to enhance problem solving capabilities, encourage independent thinking and develop professional reporting skills.
For each task, each group of students will produce a final report. The set of all reports will be examined during the final exam. Students are asked to work cooperatively in a small group.
The tutor will assist the groups during the tutorial class hours, supporting students in their learning progression and clarifying their doubts. Attendance to both lectures AND tutorials is strongly recommended, this being vital to achieve the expected learning outcomes. The teacher and the tutor are available weekly during the teaching period in order 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. although a clear and professional presentation is strictly required. Drawing tools (pencil, compass, scale rulers...) are necessary.

Lectures: the subject is fully treated in the slides provided by the teacher. Reference textbooks of international standing are suggested (some herein at the end). Some additional slides cover several topics belonging the required background of students (mainly fundamentals of strength of materials and of machine design)
Tutorials: texts of problems, datasheets of materials, extracts or abstracts of standards and handbooks will be provided by the tutor. All lecture materials will be made available on the subject website before the lecture. Students should either download or print the files before the lecture and use the copy to facilitate taking notes.
Selection of references (just suggested readings):
• P.R.N. Childs, Mechanical design engineering handbook, Elsevier, 2014.
• R.C. Juvinall, K.M. Marshek, Fundamentals of machine component design, John Wiley & Sons, 2011
• R. Budynas, Shigley’s mechanical engineering design, McGraw Hill, 2014.
• R.Stephens,A.Fatemi,R.Stephens,H.Fuchs, Metal fatigue in engineering, Wiley,2000.
• N. Recho, Fracture mechanics and crack growth, ISTE Wiley, 2012.
• S.S.Manson, Fatigue and durability of metals at high temperatures,ASM, 2009.
• V.Popov, Contact mechanics and friction, Springer, 2010.
• F.Litvin, Gear geometry and applied theory, Cambridge University Press, 2004.
• T. Harris, M. Kotzaias, Rolling bearing analysis – Essential concepts of bearing technology, CRC,2006.
• J. Bickford, Introduction to the design and behavior of bolted joints, CRC Press, 2007
• J.E.Carryer, Introduction to mechatronic design, Pearson, 2010.
Assessment and grading criteria

Achieved learning outcomes will be assessed by means of a final exam. This is based on an analytical assessment of student achievement of the "expected learning outcomes" described above.
In order to properly assess such achievement, the examination is composed of different sections:
a) Written session, day 1:
-) a test, duration 2 hrs, closed books, composed of three questions, two on chapters or sections of the lectures to assess knowledge, one problem to assess problem solving skills; each question scores max 8 points.
To be eligible to attend the oral exam the student must score in the written test a minimum total of 12 points with a minimum of 4 (50%) points for each question.
b) The oral session, day 2, consists of:
-) a review of the written output, in which examiners inform the student on grading criteria, and receive any student appeal supported by appropriate explanations;
-) a technical conversation with the lecturer to bring out the ability to deal responsibly with a mechanical design problem identifying an appropriate application of acquired knowledge (max additional 4 points)
-) a discussion with the tutor, to whom the student will submit the full set of tutorial reports; the tutor will investigate the effective personal achievement of skills and know how based on contents of reports (max additional 4 points)