OS-C501
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Offshore Standard DNV-<strong>OS</strong>-<strong>C501</strong>, November 2013<br />
Sec.6 Failure mechanisms and design criteria – Page 103<br />
Table 6-7 Minimum list of failure modes and failure mechanisms (Continued)<br />
Minimum list of Failure Mechanisms Comments<br />
Failure Modes<br />
Fibre Failure<br />
Is assumed to cause leakage. Shall always be checked.<br />
Matrix Cracking<br />
Is assumed to cause leakage unless a liner or other barrier can keep the<br />
fluid out of the laminate.<br />
Matrix Crack Growth If data exist that show leakage will only occur after a certain crack<br />
density has been reached, this failure mechanism may be used instead<br />
of simple matrix cracking. No design criterion is given in this<br />
document.<br />
Delamination<br />
May cause leakage, especially if it causes the violation of a<br />
displacement requirement.<br />
Yielding<br />
May cause leakage.<br />
Buckling<br />
May cause leakage.<br />
Unacceptably large May cause leakage.<br />
Leakage displacement<br />
Sandwich core failure May cause leakage<br />
Sandwich core yield May cause leakage<br />
Sandwich buckling May cause leakage<br />
Stress Rupture<br />
Fatigue<br />
Impact<br />
Wear<br />
Fire<br />
Explosive Decompression<br />
Effects shall be checked for all failure mechanisms mentioned above.<br />
Special failure mechanisms that may lead to leakage.<br />
Chemical decomposition /<br />
galvanic corrosion<br />
Buckling<br />
Buckling (local or<br />
global)<br />
Blast/Burst<br />
Impact<br />
Excessive<br />
deformation,<br />
Ovalisation,<br />
Excessive<br />
displacement<br />
Wear<br />
2 Design criteria - general approach<br />
2.1 General<br />
Sandwich buckling<br />
Unacceptably large<br />
displacement<br />
Impact<br />
Unacceptably large<br />
displacement<br />
Wear<br />
Chemical decomposition /<br />
galvanic corrosion<br />
Buckling is treated as a failure mode and failure mechanism in this<br />
standard.<br />
Buckling needs special analysis methods and special design criteria.<br />
The effect of other failure mechanisms, such as delamination and<br />
matrix cracking, on buckling shall be considered carefully.<br />
Buckling may lead to violation of displacement requirements.<br />
Consider same failure mechanisms as for fracture.<br />
Treated as a failure mode and failure mechanism in this standard.<br />
2.1.1 A design criterion shall be assigned to each relevant mechanism of failure.<br />
2.1.2 Design criteria for typical mechanisms of failure and materials are described in the following chapters.<br />
2.1.3 If no design criterion is known for a relevant mechanism of failure the following alternative options may<br />
be used:<br />
— it may be possible to perform a component test that evaluates the relevant design criteria without the need<br />
of a detailed knowledge of the failure mechanisms. This should be documented. See Sec.10<br />
— a design criterion may be proposed. It should be documented by experiments and/or experience that the<br />
proposed design criterion is applicable for the component. Details are given under [19].<br />
2.1.4 A modelling uncertainty shall be assigned to each design criterion and/or the strength parameters used<br />
in it. A modelling uncertainty factor is included in the design criteria equations proposed in this standard.<br />
DET NORSKE VERITAS AS