The Effects of Plate Stress-Strain Behavior and Pipemaking Variables on the Yield Strength of Large-Diameter DSAW Line Pipe

1984 ◽  
Vol 106 (2) ◽  
pp. 119-126 ◽  
Author(s):  
A. K. Shoemaker
Keyword(s):  
Yield Strength ◽  
Order Approximation ◽  
Large Diameter ◽  
Strain Level ◽  
Plate Material ◽  
Stress Strain ◽  
Line Pipe ◽  
Strain Behavior ◽  
Accumulated Strain ◽  
Cyclic Straining

Recent stringent specifications for large-diameter double-submerged-arc-welded gas-transmission line pipe include requirements that limit the range of allowable pipe yield strengths instead of the previous requirement of a minimum yield-strength value. These restricted pipe yield-strength ranges require control of the range of the yield strength in the plate used to make the pipe, knowledge of the relationship between the plate and pipe yield strength, and the effect of pipemaking (forming) variables on this relationship. The present study was conducted to determine the interrelationships among plate yield strength, plate stress-strain properties, pipe-forming variables, and pipe yield strength. In the first part of this work, pipe-forming strains were measured after each forming operating during actual pipe fabrication and the strains compared to the calculated values. The experimental and analytical values were in good agreement; thus, the cyclic straining of the original plate material during pipe forming was determined. In the second part of the program, specimens of typical line-pipe steels were cyclically loaded in the laboratory according to the cyclic histories that sections in the plate would experience when fabricated into pipe. The results showed a significant effect of the plate stress-strain behavior, as well as the amount of straining (or forming) on the resulting yield strength. Because of the complexities of all these interrelationships and the strain gradients developed through the pipe wall during pipemaking, a series of pipe were fabricated from steels having different plate stress-strain properties and the plate and pipe yield strengths were compared. Varying amounts of sinking (compressive straining) in the pipe O press and of pipe expansion were examined. Correlation of the plate and pipe yield strengths showed that, as a first order approximation, the pipe yield strength equated to the flow stress in the plate at a strain level equal to the total accumulated strain that occurs at the neutral axis of the pipe during the pipemaking operation. This approximation can only be made if work hardening occurs in the plate material at that total accumulated strain level. Otherwise, it can only be stated that the pipe yield strength will be less than that of the original steel plate.

scholarly journals Evaluation of stress-strain behavior of surface treated steels by X-ray diffraction

2012 ◽  
Vol 2 (1) ◽  
Author(s):  
Luis Coelho ◽  
A. Batista ◽  
J. Nobre ◽  
M. Marques
Keyword(s):  
Yield Strength ◽  
Plasma Nitriding ◽  
Nitrided Layer ◽  
Experimental Methodology ◽  
X Ray Diffraction ◽  
Stress Strain ◽  
X Ray ◽  
Strain Behavior ◽  
Four Point Bending ◽  
Nitride Layers

AbstractX-ray diffraction assisted four-point bending method (XRDABM) enables to analyze the evolution of surface stress with the strain during bending of specimens. This experimental methodology was used to characterize the stress-strain behavior of two plasma nitriding steels, DIN 40 Cr Mn Mo 7 and DIN 32 Cr Mo V 13, with gradients of mechanical properties across the surface layers, allowing the characterization of the in-depth evolution of the local yield strength in the nitrided layer. The results show a significantly increase of the yield strength of the nitride layers and a good agreement between the in-depth evolution of the yield strength and the XRD peak breadth for the two nitrided steels.

Comparison Between Yield Strength Results Obtained From Methods Using Both Flattened and Non-Flattened Specimens

2020 ◽  
Author(s):  
Pratham Nayyar ◽  
Dimitris Dimopoulos ◽  
William Walsh
Keyword(s):  
Yield Strength ◽  
Large Diameter ◽  
Longitudinal Direction ◽  
Ring Expansion ◽  
Test Methods ◽  
Production Test ◽  
Pipe Axis ◽  
Line Pipe ◽  
Expansion Test ◽  
Weld Properties

Abstract Tensile properties of API 5L large diameter pipes are typically determined with the use of full thickness flattened strap samples extracted in the transverse direction with respect to the longitudinal pipe axis (TPA) [1, 2, 3, 4]. It has been well established that the process of sample flattening has a significant influence on determination of the yield strength of the pipe [5, 6]. The flattening process is sensitive to a number of variables such as method of flattening, equipment used, number/sequence of strokes, and operators conducting the flattening. As a result, issues with repeatability are frequently encountered and despite several efforts, the industry lacks any type of official standard for universal use. Historically, the industry has been focused on ensuring that the actual strength of pipes was safely higher than the specified minimum. Recently, there has been interest to also establish an upper limit on pipe strength particularly in the longitudinal direction with respect to the pipe axis (LPA) in order to avoid under matching between pipe and girth weld properties. These new requirements create the need for enhanced process control to minimize the variation due to flattening. Samples obtained from longitudinally welded (SAWL) and helically welded (SAWH) seam Grade X70M line pipe of various nominal wall thickness to diameter (t/D) ratios were flattened using different procedures, measured for curvature, and tensile tested, all in controlled laboratory environments with minimized repeatability variation. Special attention was given to the definition and measurement of different types of curvatures observed through the range of different t/D ratios and effort was made to assess criteria for curvature measurement prior to testing. Additionally, non-flattened specimens were tensile tested using round bar and full ring expansion test methods, and a comparison between the results obtained from both flattened and non-flattened specimen methods was made. The sample transverse yield strength results confirmed the expected variation between samples flattened by different methods. In addition, a much greater variation was observed when comparing the yield strength results between flattened and non-flattened samples. Considerations of extending the use of non-flattened specimens as a production test and benefits or limitations associated with such practice are discussed.

Circumferential Compression Material Characterization for Pipe Collapse Load Prediction

2012 ◽  
Author(s):  
Garret Meijer ◽  
Trent Kaiser
Keyword(s):  
Yield Strength ◽  
Material Characterization ◽  
Test Methods ◽  
Strain Rates ◽  
Collapse Load ◽  
Stress Strain ◽  
Material Response ◽  
Strain Behavior ◽  
Measured Stress ◽  
The Impact

Pipe collapse limits are controlled by circumferential compressive material response. In addition to yield strength and elastic modulus, elastic-plastic transition and plastic collapse performance of thick-wall pipes also depends on the character of yielding and post-yield hardening. Accurate characterization of all these properties is necessary to obtain a reliable estimate of collapse load. Common standardized material test methods provide convenient means to acquire basic mechanical properties (i.e., yield strength, elastic modulus and elongation) under laboratory conditions (i.e., room temperature and relatively rapid loading). However, these test methods include specimen preparation, such as pipe-wall straightening, and rapid strain rates that are known to impact material response, particularly in the yield transition and post-yield regimes that are important to elastic-plastic collapse. Therefore, these common laboratory techniques are useful for providing an index of material properties, but their simplified methodologies can have a significant impact on the accuracy of collapse performance estimates. This paper describes a circumferential compressive material testing technique, developed to complement strain-based design in the energy industry, used to demonstrate differences in pipe material response measured from circumferential compressive tests and standard axial tensile tests. This technique avoids straightening the pipe wall by plastic deformation that leads to artificial rounding of the measured stress-strain yield behavior. Strain controlled loading is used to reveal yield behaviors that may be impacted by changing strain rates under stroke and load control testing. Accurate circumferential compressive material characterization improves the identification of yield and anisotropic behaviors (tension-compression and axial-circumferential) that arise from material processing, pipe manufacturing and subsequent loading. The impact of the material response is illustrated in a numerical pipe collapse simulation that directly incorporates the measured stress-strain behavior. The impact of yield strength, stress-strain yield shape and post-yield hardening are explored. Using the measured stress-strain behavior and collapse simulation results, the sensitivity of collapse load predictions to material behavior is discussed and the requirement for accurate circumferential compressive and in-situ material characterization is demonstrated.

Methods for Collapse Pressure Prediction of UOE Linepipe

2006 ◽  
Author(s):  
Andreas Liessem ◽  
Ulrich Marewski ◽  
Johannes Groß-Weege ◽  
Gerhard Knauf
Keyword(s):  
Boundary Conditions ◽  
Large Diameter ◽  
External Pressure ◽  
Test Method ◽  
Future Research ◽  
Line Pipe ◽  
Cold Forming ◽  
Research Issues ◽  
Collapse Pressure ◽  
Strain Behavior

Line pipe intended for deep water applications has to be designed predominantly with regard to external pressure in order to avoid plastic collapse. As a consequence of cold forming during UOE pipe manufacture and the subsequent application of anticorrosion coating, the characteristic stress strain behavior has to be taken into account for a reliable prediction of the collapse pressure. Verification of collapse resistance of large diameter pipes against external pressure requires adequate and reliable component testing using a sufficient number of pipe samples. These samples have to be subjected to test conditions, which closely simulate the situation in service. As the test results may depend significantly on its boundary conditions, the results needs to be thoroughly analysed and compared with existing prediction methods. It is for these reasons that such full-scale testing is time-consuming and costly. The work presented in this paper aims at clarifying and quantifying the effect of existing test boundary conditions on the results of collapse tests (collapse pressures). Correlations will be established between material properties found in laboratory tests and associated component behavior. In this context it had been necessary to develop an accurate and reproducible compression test method. The actual collapse pressures and those predicted using current available equations are compared and verified by Finite Element calculations. The paper concludes with a discussion of the major findings and with a brief outlook to future research issues.

Beneficial stress-strain behavior of moly-columbium steel line pipe

JOM ◽  
1975 ◽  
Vol 27 (9) ◽  
pp. 15-23 ◽  
Author(s):  
G. Tither ◽  
M. Lavite
Keyword(s):  
Stress Strain ◽  
Line Pipe ◽  
Strain Behavior

Stress Strain Behavior of Steel Fibre Based Concrete in Compression

2012 ◽  
Vol 1 (3) ◽  
pp. 32-38
Author(s):  
Tantary M.A ◽  
◽  
Upadhyay A ◽  
Prasad J ◽  
◽  
...  
Keyword(s):  
Steel Fibre ◽  
Stress Strain ◽  
Strain Behavior
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