The use of standard sequences in environmental testing

Laboratory tests to assess component behaviour in adverse environments are artificial, and designed to be consistent on repetition, but accelerated in attack. They each test for a particular weakness of design or of fabrication. In order to obtain a result quickly it is usual to apply a number of independent test procedures in parallel to as many separate groups of similar components. There are, however, two types of failure where it is advantageous to employ two or more individual procedures in sequence to a single group of components. (i) Where a sequence of adverse conditions, often encountered in nature, can lead to a failure which would not occur where any one of the conditions had been applied above. (ii) Where damage due to one procedure is not apparent immediately, but can be detected readily by the subsequent application of a second procedure. Practical examples of both types of failure are examined in detail. Both climatic environments and mechanical environments are considered, and also the combination of the two. The more specialized cases where the simultaneous application of two or more different procedures is essential, are considered. Such combined tests usually contain also an element of sequence, and these much more complicated cases are considered briefly.