TENSILE STRAIN CAPACITY MODEL OF X65 STEEL PIPE UNDER PRE-STRAIN EFFECT AND CRACK-TIP CONSTRAINT
Response to geohazards or mechanical loading during pipeline installation or services naturally occurs and cause displacement in length, deform plastically and potentially lead to failure. Various contributed parameters to strain-based solution become more complex with pre-strain history. Until n...
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| Format: | Dissertations |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/55156 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | Response to geohazards or mechanical loading during pipeline installation or
services naturally occurs and cause displacement in length, deform plastically and
potentially lead to failure. Various contributed parameters to strain-based solution
become more complex with pre-strain history. Until now, strain-based guidelines
are still limited, especially for large pre-strain beyond yield which is followed by
crack or crack-like-flaw defect. The cases with such large pre-strained near to
collapse condition so that stable crack growth assessment can be ignored because
the yield occurred is near to the ultimate.
In this research, plasticity response was tested first to evaluate the stress-strain
behavior in plastic zone between yield and ultimate strength and remaining strain
capacity under several pre-strain level and cracked area parameter. Here, X65 pipe
steel specimens are subjected to crack after pre-strain and fracture response was
quantified by relation of crack-tip opening distance with Qp-constraint parameter
by utilizing finite element analysis to generate the crack-tip stress field. The
maximum strain was measured on its ultimate strength point for several level of
pre-strain with sequence of: loading-unloading, introducing of blunted crack and
reloading. As the result, remaining strain capacity was reaching ?r = 0.4% when
pre-strain level was ?o = 5.2% and. It is also known that stress-strain curve in platic
zone between the yield to ultimate strength is near to linier due to pre-strain. ?-Qp
parameter is proposed here as part of fitness-for-service assessment procedure for
defected steel pipe occurred after pre-strained. For geometrical and defect studied in
this research, „failure? condition was presented in value combination of ? > 0,03 mm
and Qp ~ -0.5 |
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