ABSTRACT
The majority of topics within mechanics of solids assume homogeneous, fault free material for analysis. This is a necessary first step to predict the behaviour of materials under load, but professional engineers have to be aware of limitations that occur due to inconsistent material properties. In addition, there are situations where stress levels are increased around features such as existing cracks or around sites from which a crack could grow. Cracks can result from minor problems, many of which are almost inevitable during manufacture, such as inclusions of impurities during melting, or as part of a welding process. However, many problems can be prevented at the design stage with some knowledge of fracture mechanics and attention to detail. In many cases it is a case of accepting the existence of cracks, understanding them and living with them. This involves potential problem areas being identified and then arrangements made to monitor them. To emphasise this point, aircraft have been described as a series of cracks flying in close formation!
