scholarly journals Integrating the Shape Constants of a Novel Material Stress-Strain Characterization Model for Parametric Numerical Analysis of the Deformational Capacity of High-Strength X80-Grade Steel Pipelines

2019 ◽  
Vol 9 (2) ◽  
pp. 322 ◽  
Author(s):  
Onyekachi Ndubuaku ◽  
Michael Martens ◽  
J. Cheng ◽  
Samer Adeeb
Keyword(s):  
Axial Compression ◽  
Goodness Of Fit ◽  
Predictive Accuracy ◽  
Limit State ◽  
Pipe Material ◽  
Stress Strain ◽  
Line Pipe ◽  
Diverse Range ◽  
Strain Characterization ◽  
Characterization Model

Pipelines typically exhibit significant inelastic deformation under various loading conditions, making it imperative for limit state design to include considerations for the deformational capacity of pipelines. The methods employed to achieve higher strength of API X80 line pipe steels during the plate manufacturing process tend to increase the hardness of the pipe material, albeit at the cost of ductility and strain hardenability. This study features a simple and robust material stress-strain characterization model, which is able to mathematically characterize the shape of a diverse range of stress-strain curves, even for materials with a distinct yield point and an extended yield plateau. Extensive parametric finite element analysis is performed to study the relationship between relevant parameters and the deformational capacity of API X80 pipelines subjected to uniform axial compression, uniform bending, and combined axial compression and bending. Nonlinear regression analysis is employed to develop six nonlinear semi-empirical equations for the critical limit strain, wherein the shape constants of the material model are adapted as dimensionless parameters. The goodness-of-fit of the developed equations was graphically and statistically evaluated, and excellent predictive accuracy was obtained for all six developed equations.

Minimum Wall Thickness Requirements for Ultra Deep-Water Pipelines

2003 ◽  
Author(s):  
Enrico Torselletti ◽  
Luigino Vitali ◽  
Roberto Bruschi ◽  
Leif Collberg
Keyword(s):  
Wall Thickness ◽  
Deep Water ◽  
Failure Modes ◽  
Limit State ◽  
Strain Curve ◽  
External Pressure ◽  
Design Guidelines ◽  
Compressive Yield Strength ◽  
Pipe Material ◽  
Line Pipe

The offshore pipeline industry is planning new gas trunklines at water depth ever reached before (up to 3500 m). In such conditions, external hydrostatic pressure becomes the dominating loading condition for the pipeline design. In particular, pipe geometric imperfections as the cross section ovality, combined load effects as axial and bending loads superimposed to the external pressure, material properties as compressive yield strength in the circumferential direction and across the wall thickness etc., significantly interfere in the definition of the demanding, in such projects, minimum wall thickness requirements. This paper discusses the findings of a series of ultra deep-water studies carried out in the framework of Snamprogetti corporate R&D. In particular, the pipe sectional capacity, required to sustain design loads, is analysed in relation to: • The fabrication technology i.e. the effect of cold expansion/compression (UOE/UOC) of TMCP plates on the mechanical and geometrical pipe characteristics; • The line pipe material i.e. the effect of the shape of the actual stress-strain curve and the Y/T ratio on the sectional performance, under combined loads; • The load combination i.e. the effect of the axial force and bending moment on the limit capacity against collapse and ovalisation buckling failure modes, under the considerable external pressure. International design guidelines are analysed in this respect, and experimental findings are compared with the ones from the application of proposed limit state equations and from dedicated FE simulations.

New Limit State Functions for Determining the Puncture Resistance to External Force

2002 ◽  
Author(s):  
Jianhui Liu ◽  
Andrew Francis
Keyword(s):  
Internal Pressure ◽  
Failure Mode ◽  
External Force ◽  
Maximum Stress ◽  
Limit State ◽  
Pipe Material ◽  
Stress Strain ◽  
Indentation Force ◽  
The Impact ◽  
Dent Depth

Traditionally, a key component of the design philosophy applied to high-pressure pipelines has been the stipulation that the nominal hoop stress is less than some fraction of the specified minimum yield strength (SMYS). However, more recently both designers and operators have recognised that whilst this approach generally leads to conservatively safe designs, there may be some situations in which the conservatism is not adequate. This has resulted in a move towards limit state, and structural reliability based, methods that address actual failure modes, and consequently the contributions to structural integrity of other factors in addition to stress. One such failure mode is the puncture of a pipeline wall due an external force. This situation can arise from the impact of excavating machinery for onshore pipelines or drop objects and anchors for offshore lines. A limit state function describing this failure mode is given in DNV guidelines No 13. However, this function does not take account of the internal pressure. In this paper the influence of pressure on the pipeline indentation is addressed using both theoretical and finite element analyses. A closed-form solution of force-deformation relationship based on a consideration of rigid-plastic deformation theory, that gives a good agreement with results from both FE analyses and experimental tests, is presented. The analytical results show that indentation force, and the maximum stress/strain, required to produce a given dent depth, increase with increasing internal pressure. However, the relationship between indentation force and maximum stress/strain is not sensitive to internal pressure. The analysis therefore shows that an indentation force criterion governed solely by the dent depth, such as that given in DNV guidelines No. 13, may be highly unconservative when the pressure in the pipeline is high. Consequently, a new local denting criterion for puncture of pressurised pipes, which is based the maximum acceptable strain of the pipe material, and thereby removes the above unconservatsim, has been proposed and is presented in this paper.

Thermal Ageing Effects on Thickwalled Line Pipe

2007 ◽  
Author(s):  
Josh R. Hines ◽  
Chris M. Timms ◽  
Duane D. DeGeer
Keyword(s):  
Thermal Treatment ◽  
Yield Strength ◽  
Material Properties ◽  
Limit State ◽  
Axial Direction ◽  
Tensile Yield Strength ◽  
Pipe Material ◽  
Line Pipe ◽  
Axial Tensile ◽  
Extended Duration

Line pipe is often coated prior to installation in order to achieve some protection against the environment. Many of the coatings used today require the pipe to not only be cleaned and degreased, but also to be preheated to a temperature of 200–240°C during application of the coating material. A typical coating thermal cycle involves rapid heating of the pipe using induction coils, application of the coating, and quenching to cool the pipe for handling purposes. It is generally understood that this thermal treatment on UOE line pipe, which can last from a couple to as many as ten minutes, has an effect on the pipe yield and, to a lesser extent, tensile strength. For ultra-deepwater offshore applications, where collapse is often the controlling design case, the increase in hoop-compressive yield strength is viewed as desirable because of the corresponding increase in collapse pressure. For onshore applications, however, bending due to differential ground movements can be the primary design consideration. In this case, an increase in tensile yield strength in the longitudinal direction may occur, and may result in a higher Y/T ratio. This increased Y/T can reduce the critical buckling strain of a pipeline designed to this limit state. In this paper, the effects of a coating thermal treatment on X70 grade UOE line pipe material properties are presented with particular attention being paid to the effect on the hoop-compressive and axial tensile yield as well as Y/T ratio. Both coating mill and coupon scale thermal treatment were investigated. Comparison was made between full thickness and round bar axial tensile samples. In addition, the influence of over-ageing or extended duration heating is investigated with respect to its impact on strength and ductility as well as the Charpy impact properties. Results of this study indicate increases between 13 and 16% for hoop-compressive yields while increases in the axial direction were approximately half that magnitude. Y/T ratio increases of around 5% were seen in the axial direction. The over ageing study did not demonstrate any detrimental effect of extended duration thermal treatment on the tested material properties.

Investigation of the Stress-Strain Behaviour of Large-Diameter X100 Linepipe in View of Strain-Based Design Requirements

2008 ◽  
Author(s):  
Andreas Liessem ◽  
Jens Schro¨der ◽  
Martin Pant ◽  
Gerhard Knauf ◽  
Steffen Zimmermann ◽  
...  
Keyword(s):  
Circumferential Stress ◽  
Ring Expansion ◽  
Ground Movement ◽  
Pipe Material ◽  
Stress Strain ◽  
Line Pipe ◽  
Cold Forming ◽  
Strain Capacity ◽  
Strain Behaviour ◽  
Experimental Step

The use of high strength steels is considered as the best economical option to transport large gas volumes under high pressure from remote areas to the market. Exploration of new energy resources located in areas of complex ground and ambient climate imposes strict requirements on pipeline material and design. One of the major research issues in such areas is differential ground movement, which may be associated with large longitudinal straining in addition to plastic circumferential elongation. Hence, common design principles need thorough re-consideration, notably with respect to strain hardening properties of both base metal and girth welds. The present paper addresses several characteristics of axial and circumferential stress-strain behaviour as it is encountered in high-grade UOE line pipe. Two delivery states are taken into account, namely the “as expanded” as well as the “as coated” state. In a first experimental step, the effect of thermal cycle of the anti-corrosion coating process on stress-strain behaviour is simulated subjecting pipe material to temperatures in the range of 180° up to 250° C. In a second experimental step, stress-strain behaviour in both axial and transverse direction is mapped along the pipe production process in order to assess when and to what extent plastic strain capacity is lost during cold forming. The experimental work is complemented by instrumented ring expansion tests and instrumented burst tests. In a third future step, stress-strain information measured in both directions will be analyzed using a theoretical model based on Hill’s plasticity in order to clarify in which way circumferential stress-strain behaviour may impose constraints on strain capacity of axial direction. Within the scope of this paper, first and foremost, underlying principles are outlined and discussed and indications with respect to modelling implications given. Based upon these three sequential investigatory steps, it will be possible to draw conclusions with respect to stress-strain behaviour of parent material and the pipe forming process and to show that unfavourable effects triggered by coating do not show within the structure while they might do in material tests.

Explosion Recurrence Modelling

2004 ◽  
Author(s):  
Sirous F. Yasseri ◽  
Jake Prager
Keyword(s):  
Risk Assessment ◽  
Goodness Of Fit ◽  
Residential Buildings ◽  
Limit State ◽  
Life Time ◽  
Assessment Method ◽  
The North ◽  
Offshore Installations ◽  
Risk Assessment Method ◽  
Explosion Load

This paper describes a recurrence law for explosions. The proposed recurrence law fits quite well to the historic explosion data in residential buildings as well as to the data on offshore installations in the North Sea. Generally quantified explosion risk assessment is performed for offshore installations, since it is believed historic data does not correspond to a specific installation and it may not be appropriate for use in performance based explosion engineering, which may in itself require realistic load description of explosion recurrence. The goodness-of-fit of the model for explosion occurrence data obtained using the quantified risk assessment method is also discussed. The paper then introduces the concept of performance-based design, which is an attempt to design structures with predictable performance under explosion loading. Performance objectives such as life safety, collapse prevention, or immediate resumption of operation are used to define the state of an installation following a design explosion. The recurrence law is then used to associate a level of explosion load to each limit state using a desirable level of probability of exceedance during the installations life time.

Girth Weld Strength Matching Effect on Tensile Strain Capacity of Grade X70 High Strain Line Pipe

2018 ◽  
Author(s):  
Hisakazu Tajika ◽  
Takahiro Sakimoto ◽  
Tsunehisa Handa ◽  
Rinsei Ikeda ◽  
Joe Kondo
Keyword(s):  
High Strain ◽  
Limit State ◽  
Full Scale ◽  
Bending Test ◽  
High Grade ◽  
Line Pipe ◽  
Bending Tests ◽  
Strain Capacity ◽  
Pipeline Project ◽  
Pipe Bending

Recently high grade pipeline project have been planned in hostile environment like landslide in mountain area, liquefaction in reclaimed land or the frost heave in Polar Regions. Geohazards bring large scale ground deformation and effect on the varied pipeline to cause large deformation. Therefore, strain capacity is important for the pipeline and strain based design is also needed to keep gas transportation project in safe. High grade steel pipe for linepipe tends to have higher yield to tensile (Y/T) ratio and it has been investigated that the lower Y/T ratio of the material improves strain capacity in buckling and tensile limit state. In onshore pipeline project, pipe usually transported in 12 or 18m each and jointed in the field. Girth weld (GW) is indispensable so strength matching of girth weld towards pipe body is important. In this study strain capacity of Grade X70 high strain pipes with size of 36″ OD and 23mm WT was investigated with two types of experiments, which are full scale pipe bending tests and curved wide plate tests. The length of the specimen of full scale bending tests were approximately 8m and girth weld was made in the middle of joint length. A fixed internal pressure was applied during the bending test. Actual pipe situation in work was simulated and both circumferential and longitudinal stress occurred in this test. Test pipes were cut and welded, GTAW in first two layer and then finished by GMAW. In one pipe, YS-TS over-matching girth weld (OVM) joint was prepared considering the pipe body grade. For the other pipe, intentionally under-matching girth weld (UDM) joint was prepared. After the girth welding, elliptical EDM notch were installed in the GW HAZ as simulated weld defect. In both pipe bending tests, the buckling occurred in the pipe body at approximately 300mm apart from the GW and after that, deformation concentrated to buckling wrinkle. Test pipe breaking locations were different in the two tests. In OVM, tensile rupture occurred in pipe body on the backside of buckling wrinkle. In UDM, tensile rupture occurred from notch in the HAZ. In CWP test, breaking location was the HAZ notch. There were significant differences in CTOD growth in HAZ notch in these tests.

Development of X90 and X100 Steel Grades for Seamless Linepipe Products

2014 ◽  
Author(s):  
Diana Toma ◽  
Silke Harksen ◽  
Dorothee Niklasch ◽  
Denise Mahn ◽  
Ashraf Koka
Keyword(s):  
Wall Thickness ◽  
Deep Water ◽  
High Strength ◽  
Oil And Gas Industry ◽  
Pipe Material ◽  
Line Pipe ◽  
Materials Development ◽  
Additional Tool ◽  
Technical Requirements ◽  
Steel Grades

The general trend in oil and gas industry gives a clear direction towards the need for high strength grades up to X100. The exploration in extreme regions and under severe conditions, e.g. in ultra deep water regions also considering High Temperature/High Pressure Fields or arctic areas, becomes more and more important with respect to the still growing demand of the world for natural resources. Further, the application of high strength materials enables the possibility of structure weight reduction which benefits to materials and cost reduction and increase of efficiency in the pipe line installation process. To address these topics, the development of such high strength steel grades with optimum combination of high tensile properties, excellent toughness properties and sour service resistivity for seamless quenched and tempered pipes are in the focus of the materials development and improvement of Vallourec. This paper will present the efforts put into the materials development for line pipe applications up to grade X100 for seamless pipes manufactured by Pilger Mill. The steel concept developed by Vallourec over the last years [1,2] was modified and adapted according to the technical requirements of the Pilger rolling process. Pipes with OD≥20″ and wall thickness up to 30 mm were rolled and subsequent quenched and tempered. The supportive application of thermodynamic and kinetic simulation techniques as additional tool for the material development was used. Results of mechanical characterization by tensile and toughness testing, as well as microstructure examination by light-optical microscopy will be shown. Advanced investigation techniques as scanning electron microcopy and electron backscatter diffraction are applied to characterize the pipe material up to the crystallographic level. The presented results will demonstrate not only the effect of a well-balanced alloying concept appointing micro-alloying, but also the high sophisticated and precise thermal treatment of these pipe products. The presented alloying concept enables the production grade X90 to X100 with wall thickness up to 30 mm and is further extending the product portfolio of Vallourec for riser systems for deepwater and ultra-deep water application [1, 3, 4].

Stress–strain relationship in axial compression for concrete using recycled saturated coarse aggregate

2011 ◽  
Vol 25 (5) ◽  
pp. 2335-2342 ◽  
Author(s):  
González-Fonteboa Belén ◽  
Martínez-Abella Fernando ◽  
Carro López Diego ◽  
Seara-Paz Sindy
Keyword(s):  
Axial Compression ◽  
Coarse Aggregate ◽  
Stress Strain ◽  
Strain Relationship

Analytical stress–strain model of reinforced concrete masonry wallettes under axial compression

Structures ◽  
2021 ◽  
Vol 34 ◽  
pp. 2922-2935
Author(s):  
Tatheer Zahra ◽  
Julian Thamboo ◽  
Mohammad Asad ◽  
Mengli Song
Keyword(s):  
Reinforced Concrete ◽  
Axial Compression ◽  
Stress Strain ◽  
Concrete Masonry ◽  
Strain Model
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