Environmental Engineering Reference
In-Depth Information
• Critical dimensions;
• Dimensions allowable for operation;
• Allowable dimensions of discontinuities in manufacture (the norms
of defects in component) using the valid regulatory documents and/
or Technical Instructions for manufacture.
For the selected product, it is necessary to define the probability of
the existence of defects which determine its quality, reliability and safety
(regulatory requirements for its quality, reliability and safety).
Further, the regulatory curve is plotted in the coordinates lgP-χ fr the
state of the product using the fixed points of this curve: the point that
characterises the probability of formation of a defect of the critical size,
and the point which characterises the probability of occurrence of the defect
allowed in the operation of the characteristic size.
The product is inspected by any chosen NDT method. Repair is carried
out in accordance with the inspection results.
.The test specimen is prepared for the given product, as described in
section 5.3.2.
The selected method of non-destructive inspection is used to inspect
the test specimen for the given product and the results of inspection are
compared with the actual defects found in the test specimen. The ratio
of 'the number of defects detected in the test specimen
N
det.ts
(χ) divided
by the number of the defects embedded in the test specimen
N
emb.ts
(χ)' is
determined for each characteristic defect size χ. This ratio characterises the
probability of detection of the given characteristic size of the defect
P
d.d
(χ):
P
d.d
(χ) =
N
det.ts
(χ)/
N
emb.ts
(χ)
The initial defectiveness of the component
N
in
(χ) =
f
(χ) is determined.
This parameter is determined as the ratio of the number of defects of the
given characteristic size
N
det.comp
(χ), detected in inspection, to the probability
of detection of defects by the given method of non-destructive inspection:
N
in
(χ) =
N
det.comp
(χ)/
P
d.d
(χ),
On the graph which shows the regulatory curve of the state of the
component it is necessary to plot the probabilistic part of the curve of initial
defectiveness
P
in
(χ
>
χ
*
), which reflects the probability of existence of
a defect with the characteristic size χ
>
χ
*
, where χ
*
is the characteristic
size of the defect given as the lower boundary of the range of characteristic
dimensions of the defects whose probability of existence resistance is being
investigated.
The residual defectiveness
N
res
= φ(χ) is determined as the difference
of the initial defectiveness
N
in
(χ) and other defects detected in inspection
N
det.comp
(χ).
This is followed by the analysis of the position of the curves of the
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