Superposition of Causes of Failures. Chain Systems
In the preceding chapters, we considered the interaction of “peak” loads and the process of wear. The action of wear showed up in the constant lowering of the maximum admissible load level, and the exceeding of this level by a “peak” in the load led to failure. Thus, the wear and the instantaneous injury leading to failure depend on the maximum admissible load. However, we rather frequently observe objects where the wear and the failures due to “peak” loads are unconnected with each other. Aviation equipment is an example. The gradual wear of such equipment does not lead to a drop in their durability under overloading. This is explained by the fact that the parts of the devices detecting the overloadings, to all intents and purposes, do not wear out. But wear can cause a violation of its capacity to function by causing the operating characteristic η(t) to get outside admissible limits. Overloadings, in turn, can cause a failure if their value exceeds the calculated limits. Consequently, the “peak” loads, which appear here in the form of overloadings, and wear, which affect the behavior of the operating characteristic η(t), act parallel to but independently of each other. Such examples could be multiplied. Actually, any object that has several operating parts that do not interact with each other also has several causes of failure that act parallel to but independently of each other.
KeywordsFatigue Eter Germanium
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