


Politecnico di Torino  
Academic Year 2009/10  
06ASBDR Structural elements of machines 

1st degree and Bachelorlevel of the Bologna process in Mechanical Engineering  Vercelli 





Objectives of the course
This course introduces students to theoretical and practical machine design. Class will have a three step flow. In the first step some basic failure analysis skills will be developed: how a component will fail, how design changes could be made to avoid failure, with emphasis on fatigue failures. Practical aspects of machine design will be then analyzed in order to understand engineering assumptions and solution idealizations, and to develop experience in the process of realization of a relatively simple design, like shafts and axles, power transmission elements, joints. Analytical formulations will be developed and presented to the students.
The second step will involve example problems will be solved to help students understand how to use our analytical knowledge to solve practical problems. The third step is the crown of the course where the students, by using the basic 'analytical and creative skills' developed also in other courses in the context of the design process (design techniques, technical drawing, statics, kinematics and dynamics, solid mechanics, materials engineering) will design a 'machine' to satisfy a particular need. 
Expected skills
By the end of this course students should have an understanding of the mechanical behavior of materials and simple components of a mechanical assembly. This will include the deformation behavior of metals and the ways that metals can fail. Students should have answers to the following questions: why do materials behave differently under cyclic loads compared to static loads? Why and how do components fail? Can we prevent failure?
Students should be able to design simple mechanical assembly and its components, like shafts and axles, power transmission elements, joints. They should be also able to perform those activities in teamwork. 
Prerequisites
Solid mechanics, kinematics & dynamics engineering, technical drawing, solid mechanics, materials engineering.

Syllabus
This course focuses on properties of materials and how and why they fail and the consequences. An important part of being an engineer is the ethical responsibility to the public with regard to the engineering decisions made. These aspects will be covered during lectures on failure, safety factors and materials selection and component design.
Part I Basics Introduction to mechanical design, materials, load and stress analysis, deflection and stiffness, Reliability, Safety Factors. Part II Failure Prevention Failures resulting from static loading, review, brittle failure, ductile failure. Fatigue failure resulting from variable loading, cyclic stresses, the SN curve, fatigue life methods, factors that affect fatigue life, mean stress correction methods, Miner's rule. Stress concentration factors, static and cyclic. Contact stress, Hertz theory and application to rolling contact bearings. Part III Design of Mechanical Elements Shafts and axles, shaft components, rolling contact bearings, keys, splines, interference fits, gears, screws, fasteners, welding, bonding. 
Laboratories and/or exercises
Example problems will be solved to help students understand how to use our analytical knowledge to solve practical problems.
The design project (power transmission case study) is a major part of the course lab. A common problem will be defined during the first few sessions of the class. The material required for the design project will be made available through lectures, readings and assigned problems. The delivery of this material will be timed so that it is available when you need it for the design project. Students will work in groups of 2 or 3 to complete the design project. These teams will design a 'solution' for the defined 'problem' using common machine elements. A detailed report of the project results must be turned in at the end of the course. This report must include all the calculations and technical drawings. 
Bibliography
Textbook:
Shigley, Budynas and Nisbett Mechanical engineering design, Mc GrawHill. R.C. Juvinall, K.M. Marshek, Fundamentals of Machine Component Design, Wiley. J. A. Collins, Failure of materials in mechanical design, J. Wiley. There will be some handouts in this course and they will be made available on the course website. 
Revisions / Exam
Exams consist in two parts: written and oral: Written examination consists in the solution of one or two exercises regarding simple design problems, as developed in the practical lab. No books or student notes are admitted. In the oral examination the project report will be discussed.

Notes The project report must be completed and submitted in order to be admitted to exam. 
