OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.10 Component testing – Page 159
SECTION 10 COMPONENT TESTING
1 General
1.1 Introduction
1.1.1 Component testing is carried out for either:
— qualification based entirely on tests on full scale or large scale components, or
— updating or verification of analysis by testing.
1.1.2 This standard gives procedures to evaluate test results and shows procedures to determine test
programmes.
1.1.3 A structure or part of a structure can in some cases be qualified by testing only, i.e. no structural analysis
as presented in Sec.9 is performed. This approach is presented in [2].
1.1.4 Testing can in some cases be carried out to document the design or increase confidence in design
calculations. It is an alternative or complement to analysis based on basic material properties. See [3].
1.1.5 If the component is checked by qualification testing only, design calculations are not relevant. The test
results are the only relevant information to evaluate whether the component is fit for purpose. This also means
that the qualification is only valid for the conditions tested.
1.1.6 If testing is carried out to complement the analysis, it is done to reduce or to eliminate the influence of
systematic errors introduced in the design methodology or to verify that the assumptions regarding failure
mechanisms, failure modes etc. on which the design is based are correct.
1.1.7 In most practical cases component testing is used in combination with a structural analysis to evaluate
the component for a wider range than the actual test conditions.
1.2 Failure mode analysis
1.2.1 An analysis of all possible failure modes in the structure shall be done as described in Sec.3.
1.2.2 It shall be shown by testing or analysis that none of the possible failure modes will be critical for the
performance and safety of the structure.
Guidance note:
A special concern with composite materials is that minor loads may cause failures even though the structure can well
withstand the main loads for which it was designed or built. Such minor loads can be through thickness loads in
laminates or sandwich structures or loads oriented perpendicular to the main fibre direction in the laminate.
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1.2.3 An evaluation of failure modes is especially critical if long-term performance shall be documented and
data must be extrapolated to longer lifetimes than test times. In that case failure may be caused by failure modes
that were not critical in a short-term test (see [4]).
1.2.4 Temperature changes may introduce different failure mechanism. If the structure is exposed to different
temperatures and resulting thermal stresses, possible changes of failure modes should be evaluated.
Analytically these changes are modelled by temperature dependent material properties and by possible changes
in the failure criteria that are applied, e.g. ductile brittle transition. Testing should be done for all conditions
that cannot be modelled in a satisfactory way.
1.3 Representative samples
1.3.1 Test specimens shall represent the actual structure.
1.3.2 Production methods and materials shall be exactly the same, and production tolerances should be known
and controlled. The tolerances for producing the test samples should be representative of production conditions
of the product.
1.3.3 If the qualification is based on testing only [2], no changes shall be made to materials or production
without new tests.
1.3.4 If testing is combined with analysis changes in materials or geometry may be permitted, if the
consequences of the changes can be treated with confidence by the analytical methods.
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