CN101923021B - Method for rapidly determining buckling strain capability of steel tube - Google Patents
Method for rapidly determining buckling strain capability of steel tube Download PDFInfo
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- CN101923021B CN101923021B CN2009100870545A CN200910087054A CN101923021B CN 101923021 B CN101923021 B CN 101923021B CN 2009100870545 A CN2009100870545 A CN 2009100870545A CN 200910087054 A CN200910087054 A CN 200910087054A CN 101923021 B CN101923021 B CN 101923021B
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Abstract
The invention provides a method for rapidly determining the buckling strain capability of a steel tube, belonging to the production control technical field of the high-deformability steel tube for a petroleum and gas pipeline. The method comprises the following steps: taking a longitudinal test piece from the tube, and then obtaining an engineering stress-engineering strain curve by a test; and calculating the critical buckling strain of the steel tube in a bending deformation mode according to a formula: epsiloncrit=15.963*Rt2.0/Rt1.0-15.139, wherein, the critical buckling strain is average strain that a compression side of the test piece stretches towards two sides over a distance which is twice as long as the external diameter length of the steel tube with a buckled position as a center. The method can help rapidly determine the critical buckling strain of the steel tube in the bending deformation mode by controlling the tensile property of the pipeline steel tube, and can carry out performance control by a conventional production control test according to the stress ratio of the critical buckling strain level so as to produce the steel tube which can meet the requirement for the critical buckling strain level.
Description
Technical field
The invention belongs to the production control technical field of oil and gas pipeline, relate to a kind of method of confirming buckling strain capability of steel tube fast with high deformability steel pipe.
Background technology
It is the inefficacy by Load Control that the generalized case underground pipelines lost efficacy; The design criteria that is based on stress limit that adopts; But for the pipeline of under rugged surroundings such as the multiple district of geologic hazards such as earthquake, rubble flow, landslide, tundra and seabed, laying; Its suffered magnitude of load is uncontrollable, and distortion also only just can stop after displacement has reached to a certain degree, and this moment, load received displacement or strain control.Adopt the stress limit criterion to design the safety that can't guarantee pipeline in this case merely, must adopt the strain limit criterion, i.e. the design strain of pipeline must be less than the strain allowable of pipeline.The strain allowable of pipeline is relevant with the geometrical factor of pipeline steel tube on the one hand; Like the external diameter of body and the ratio of wall thickness, reach of displacement etc.; On the other hand, also can not be ignored, like the yield tensile ratio of pipe line steel, extensibility, strain hardening index etc. with the relation of body material property.The critical flexing strain of general employing pipeline steel tube on the engineering (in the time of can being defined as the steel pipe flexing, the mean strain on the outer electrical path length of twice, down together) as its strain allowable.
For the steel pipe of confirming specification (caliber, wall thickness, grade of steel), it receives bending load and does the time spent, and the size of critical flexing strain depends on the mechanical property of tube material to comprise elastic modulus, yield strength, and working hardening performance fully.Therefore develop the high adaptability to changes pipeline steel tube that is used for using in the rugged surroundings area and just have the important engineering meaning.
Weigh the crooked deformability of tube product, the most conventional method obtains its critical flexing strain through carrying out full-scale real canal curvature test exactly, or on the basis of test, carries out accurate FEM calculation, obtains its critical flexing strain.But the cost of full-scale real canal curvature test is very high, can not be used for the production control test, and the high complexity of FEM calculation makes also it can't be used for production control.
Summary of the invention
The object of the invention is to provide a kind of full-scale real canal curvature test of avoiding carrying out repeatedly, can confirm that external diameter is 1219mm, and wall thickness is the method for confirming buckling strain capability of steel tube fast of vertical mechanical property of 22.0mm specification X80 level pipeline pipeline steel pipe.
The method of confirming buckling strain capability of steel tube fast adopts following steps:
1) on body, get longitudinal test piece, test obtains engineering stress-engineering strain curve;
The said longitudinal test piece specification of step 1) is insied width 38.1mm, gauge length 50.8mm.
Strain 2.0% corresponding stress value is defined as R on the said curve of step 1)
T2.0, strain 1.0% corresponding stress value is R
T1.0, the stress ratio parameters R that needs of acquisition thus
T2.0/ R
T1.0
2) calculate the critical flexing strain of steel pipe under the flexural deformation pattern by following formula:
ε
crit=15.963×R
t2.0/R
t1.0-15.139
ε
Crit: for steel pipe under the flexural deformation pattern during flexing, compressed side is that the mean strain on the twice outer diameter of steel pipes length is extended on middle mind-set both sides so that the flexing place to take place.
Step 2) described steel pipe is external diameter 1219mm, the X80 steel pipe of wall thickness 22.0mm specification.
The present invention can be through the tensile property of control pipeline steel tube; Confirm the critical flexing strain of steel pipe under the flexural deformation pattern fast; Stress ratio through critical flexing strain level; Can carry out Properties Control through the production control test of routine, produce the steel pipe that satisfies the requirement of critical flexing strain level.
Description of drawings
Fig. 1 is a body longitudinal stretching sample synoptic diagram;
Fig. 2 is critical flexing strain and stress ratio R
T2.0/ R
T1.0Graph of a relation.
Embodiment
Specify the present invention below in conjunction with accompanying drawing.
The object of the invention is to provide a kind of full-scale real canal curvature test of avoiding carrying out repeatedly, can confirm that external diameter is 1219mm, and wall thickness is the method for confirming buckling strain capability of steel tube fast of vertical mechanical property of 22.0mm specification pipeline steel tube.
The method of confirming buckling strain capability of steel tube fast adopts following steps:
1) on body, get longitudinal test piece, test obtains engineering stress-engineering strain curve;
The said longitudinal test piece specification of step 1) is insied width 38.1mm, gauge length 50.8mm.
Strain 2.0% corresponding stress value is defined as R on the said curve of step 1)
T2.0, strain 1.0% corresponding stress value is R
T1.0, the stress ratio parameters R that needs of acquisition thus
T2.0/ R
T1.0
Stress ratio is on the tensile stress strain curve, the ratio of corresponding stress when differently strained, and it can reflect in the tension test process, the trend that material rises along with the increase of strain at a certain stage stress, the reinforcement trend when expressing material deformation.Stress ratio can define material in the stress ratio in different distortion stage, so can embody the reinforcement ability of material when a certain certain variations level more targetedly.Stress ratio under 1.0% and 2.0% strain has represented this specification steel pipe when flexural deformation is issued to flexing, the strain hardening level of main crushed element on the body.
2) calculate the critical flexing strain of steel pipe under the flexural deformation pattern by following formula:
ε
crit=15.963×R
t2.0/R
t1.0-15.139
ε
Crit: being defined as steel pipe during flexing, on crooked inboard (compressed side just) body, is the center so that the flexing place to take place under the flexural deformation pattern, extends the last mean strain of distance that is equivalent to twice outer diameter of steel pipes length to both sides;
The Finite element analysis of deformation that line pipe is crooked can well be verified by full-scale actual loading test, and the finite element model that uses process to verify can effectively be studied the deformational behavior of relevant steel pipe.Steel pipe through to the various stress ratio levels produced carries out analytical calculation, has finally obtained above-mentioned relational expression.Final through simple small sample mechanical property test result, the deformability of prediction tube product.
Step 2) described steel pipe is external diameter 1219mm, the X80 steel pipe of wall thickness 22.0mm specification.
Claims (1)
1. method of confirming fast buckling strain capability of steel tube, its characteristic adopts following steps:
1) on body, get longitudinal test piece, test obtains engineering stress-engineering strain curve;
2) calculate the critical flexing strain of steel pipe under the flexural deformation pattern by following formula:
ε
crit=15.963×R
t2.0/R
t1.0-15.139
ε
Crit: for steel pipe under the flexural deformation pattern during flexing, compressed side is that the mean strain on the twice outer diameter of steel pipes length is extended on middle mind-set both sides so that the flexing place to take place;
Said longitudinal test piece specification is insied width 38.1mm, gauge length 50.8mm;
Strain 2.0% corresponding stress value is defined as R on the said curve
T2.0, strain 1.0% corresponding stress value is R
T1.0, the stress ratio parameters R that needs of acquisition thus
T2.0/ R
T1.0
Described steel pipe is external diameter 1219mm, the X80 steel pipe of wall thickness 22.0mm specification.
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Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
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EP1843143B1 (en) * | 2005-12-15 | 2021-02-03 | JFE Steel Corporation | Methods for evaluating local buckling capability of steel pipe |
CN102410957B (en) * | 2011-07-25 | 2014-04-02 | 西北工业大学 | Test sample and method for testing performance parameters of pipe under complex stress state |
CN102494948A (en) * | 2011-12-09 | 2012-06-13 | 上海锅炉厂有限公司 | Method for simulating deformation of tension side of elbow by tension |
CN103091167B (en) * | 2013-01-23 | 2014-10-29 | 西北工业大学 | Method for continuously measuring change of shrinkage strain ratio of titanium alloy pipe |
CN103760018A (en) * | 2013-12-19 | 2014-04-30 | 中国石油天然气集团公司 | Measuring method of critical buckling strain of steel pipe |
CN104596845B (en) * | 2014-11-20 | 2017-04-05 | 中国石油天然气集团公司 | A kind of measuring method of the true stress―strain curve of metal weldedstructure |
CN111766136B (en) * | 2020-08-14 | 2023-06-06 | 中国石油天然气集团有限公司 | Method for obtaining tensile performance parameters of steel plate for manufacturing pipe and steel plate selection method |
Citations (1)
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CN1890498A (en) * | 2003-12-10 | 2007-01-03 | 杰富意钢铁株式会社 | Method of determining strain hardening characteristics of line pipe |
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CN1890498A (en) * | 2003-12-10 | 2007-01-03 | 杰富意钢铁株式会社 | Method of determining strain hardening characteristics of line pipe |
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