Engineering Science 3  MECH 226  Home Page 

1. Introduction.
These notes are designed to help you to learn how to solve a range of problems in engineering science. For the majority of problems in statics it can be assumed that superposition applies, this requires that only small strains and small deflections are occurring. In such cases the various loads and moments acting on a body can be separated and the effects of each calculated as though the one being considered is the only force or moment acting. The total resulting stresses (and strains) can then be found by summing the individual contributions of all the forces and moments. In the early days of engineering, machinery was slow moving and the main forces present were those due to gravity acting on the machine masses. However a key aspect of engineering progress has been the requirement for machinery to operate at ever increasing speeds. It is now very common for dynamic (or inertia) load effects to dominate and gravity forces are commonly insignificant. A systematic approach is important  the procedure below is applicable to many problems. The consideration given to the effects of friction is often different in static and dynamic problems. Frequently in statics problems friction plays a vital role  eg the forces acting on a ladder leaning against a wall  and in these cases, friction must be considered. However in dynamics problems it is common for friction effects to be quite small and consequently ignored. This is partly due to the fact that in most dynamic systems the efficiency has to be quite high, e.g. better than 95% for a good gearbox, so the error that occurs in ignoring friction is normally quite small and it greatly simplifies the initial problem solution. Where a detailed design is required for a critical high powered system, then the friction effects would be considered, mainly because a great deal of heat may need to be dissipated. 2. Units
3. For all problems it is vital that you understand the configuration.

4. For statics problems it is usual to resolve forces and moments so their components are parallel or perpendicular to the axes of the component parts (and xyz axes). Statics problems that are determinant can now be solved by considering the effects of the components of the forces and moments and summing the individual results  the problems considered in this module involve only small strains and small displacements so superposition can be used. 5. For dynamics problems: 6. Energy Methods 7. Vibration Problems The following topics are of interest: NB: It will not be possible in this module to cover all these topics. 
Links to Notes for this Module: Not all of these topics will be covered, some are included for completeness and provide supplementary information. Topics marked '*' are of primary importance.
Previous Exam Questions  from June 2003:
References
1. 'Mechanics and Materials for Design', by N H Cook, McGrawHill, Int. student Ed.,
1985, ISBN: 007Y66157X.
2. 'Mechanics of Materials', Gere and Timoshenko, Brooks/Cole, 2nd ed. 1984, ISBN: 0534030998.
There are several books with titles 'Mechanics of Materials' or 'Strength of Materials' or similar which are suitable for the 'statics' part of the course contents.
3. 'Principles of Engineering Mechanics', H R Harrison and T Nettleton, Arnold, 1978, ISBN: 0713133783 (deals with dynamics rather than statics).
There are several American textbooks on Dynamics, but they tend to have a lot more than is needed for this course on dynamics and barely enough on vibration:
4. 'Mechanics for Engineers  Dynamics', F P Beer and E R Johnson, McGrawHill, Int. Ed., 4th Ed. 1987, ISBN: 0071001352.
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David J Grieve, 26th November 2003.