OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.4 Materials - laminates – Page 70
Check that T > -t(α) is fulfilled, where t(α) is to be taken from Table 4-12.
Table 4-12 t(α)
t(α)
N Confidence 1-α = 0.75
2 1.000
5 0.741
10 0.703
15 0.692
20 0.688
25 0.685
100 0.677
Infinity 0.675
8.7.6 Calculate
where σˆ is the standard deviation of the measurements of the material to be checked for similarity. Check that
C 2 < χ 2 (α), where χ 2 (α) is to be taken from Table 4-13.
Table 4-13 χ 2 (α)
χ 2 (α)
N Confidence 1-α = 0.75
2 1.323
5 5.385
10 11.389
15 17.117
20 22.718
25 28.241
50 55.265
8.7.7 If all of the above conditions are fulfilled the typical data may be used to represent the similar material.
8.7.8 If neither the simplified similarity test nor the hypothesis test is passed, the material property has to be
measured directly (see [8.4]).
8.8 Confirmation testing for long term data - high safety class
8.8.1 At least 9 tests shall be carried out.
8.8.2 Test data shall be evenly distributed over the logarithmic time or number of cycles scale.
8.8.3 At least two test results shall fall within 90% of the anticipated lifetime or the anticipated number of
cycles.
8.8.4 If the anticipated lifetime exceeds 10000 hours testing up to 10000 hours is sufficient. The strain levels
should be chosen such that failure occurs after about 10 2 , 10 3 and 10 4 hours, respectively.
8.8.5 If the anticipated lifetime exceeds 10 6 cycles testing up to 10 6 cycles is sufficient. The strain levels
should be chosen such that failure occurs after about 10 3 , 10 4 and 10 6 cycles, respectively.
8.8.6 No more than 2.5% of the measured points should lie below µ-2σ, no more than 16% below µ-σ and no
more than 50% below the mean µ. If the data points for a material do not fulfil these requirements more testing
should be carried out.
8.9 Confirmation testing for long term data - normal safety class
8.9.1 At least 3 survival tests shall be carried out.
C
2
2 ( 1) ˆ σ
= n −
2
σ
0
8.9.2 Tests shall be carried out at strain levels where the anticipated mean lifetime or number of cycles is 1000
hours or 10 4 cycles respectively. If the expected lifetime or fatigue cycles of the structure are less, tests shall
be carried out up to the expected values.
8.9.3 Tested specimens shall not fail before the testing time or number of cycles has exceeded the characteristic
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