Environmental Engineering Reference
In-Depth Information
• determination of load distribution;
• determining the actual defect component (residual defects);
• identify future operating conditions;
• identify changes in defect during the operation;
• determination of changes in mechanical properties during the
operation;
• determining the mechanism of fracture: brittle, quasi-brittle or
ductile;
• determining the probability of failure and its changes during
operation.
The distribution laws of mechanical properties, loading, defects, the
effects of ageing, cyclic loading, the influence of corrosive environment
and fracture mechanisms are taken into account.
The basis of the following methods is to consider the following
characteristics of manufacturing techniques and quality control of structural
elements (products).
In manufacture, products usually contain technological defects of
integrity of metal. Integrity defects may also arise during the operation.
Non-destructive testing is performed to identify and eliminate these defects.
It is believed that after the non-destructive testing and repairs conducted
on the basis of NDT results the product is free from defects identified by
NDT. It is assumed that the reliability and safety of the product in operation
is guaranteed (see regulatory documents on nuclear energy, for example,
Ref. 73, 6, 91).
In fact, there are practically no NDT methods and means in engineering
which would guarantee with 100% certainty detection of all defects.
Therefore, there is always a certain probability of missing a defect, including
critical defects (i.e. propagation of such a defect during operation will lead
to product damage or destruction). It is known that in almost all cases, NC
there is a substantial likelihood of missing a large defect that substantially
exceed the permissible size (see Section 5.1, 5.2). In practice, it turns
out that products almost always contain defects after NDT and remoal of
the identified defects. These remaining defects ultimately determine the
reliability and operating efficiency of the products.
The technical result obtained when using the methods described below
can be used for assessing the actual defectiveness of the product after
testing and repair of the identified defects and to determine the actual level
of reliability and safety of the product before it is destroyed or damaged
in service.
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