Many problems which arise in engineering defy exact analysis. It is often not
even necessary to obtain rigorously accurate results to practical engineering
problems, since data, variables and factors are themselves usually only
approximations.
In design, as one proceeds from a brief to the manufacturing details, one
needs to start with approximate assessment of forces, stresses, speeds, power
etc., so as to be able to lay out principal geometries. The iterative process
leading to a final design usually involves a gradual enhancement of the
accuracy of calculated predictions. The value of mathematical precision is
often reduced, and even negated, because one invariably has to use idealized
simplifications and models to represent real physical situations. Thus
approximate methods of calculations with a reasonable knowledge of the
degree of accuracy involved can, in general, be much more valuable than
complex and time-consuming precise and rigorous mathematical analyses.
The expression “degree of accuracy” implies, per se, the need to assess the
magnitude and direction of the error invoved.
This book has been written with this underlying philosophy. It is hoped that
the information collated, the techniques and methods elucidated, and the case
studies described will be of help to engineering designers in their various and
demanding tasks.