Yield Strength of Line Pipe: Analysis of Forming Operations and Flattened Straps

2010 ◽  
Author(s):  
William J. Walsh ◽  
David Preston
Keyword(s):  
Residual Stress ◽  
Yield Strength ◽  
Bauschinger Effect ◽  
Material Model ◽  
Mechanical Tests ◽  
Specimen Preparation ◽  
Line Pipe ◽  
Apparent Modulus ◽  
Roll Bending ◽  
Tension And Compression

The effects of line pipe forming processes (Spiral, UOE, JCE, 3 Roll Bending, ERW) on steel yield strength are investigated by material modeling and mechanical testing. A model is developed for predicting the performance of a flattened transverse-body-tensile sample as typically performed by pipe mills for yield strength determination. Consideration is given to the Bauschinger effect, and hardening behavior to examine the resulting residual stress patterns through the wall thickness and the effect on measured yield strength. The pipe forming processes are modeled as pure bending and analyses are performed to determine how well this assumption simulates the actual operations. Tensile and compression testing is performed to establish the Bauschinger effect in both the tension and compression initial loading directions. The tensile data is incorporated into the material model. The model illustrates the progressive evolution of the residual stress pattern throughout the sequence of forming operations and specimen preparation. In addition, the residual curvature remaining in flattened tensile samples is analyzed and correlated with mechanical tests. The apparent modulus caused by curvature is shown to cause significant variation in the reported yield strength of linepipe.

Calculation of Relaxation of Residual Stress and Change of Yield Strength in Shot Peened Layer

2005 ◽  
Vol 490-491 ◽  
pp. 396-403 ◽  
Author(s):  
Yan Huai Li ◽  
Jian Lu ◽  
Ke Wei Xu
Keyword(s):  
Residual Stress ◽  
Surface Layer ◽  
Yield Strength ◽  
Shot Peening ◽  
Axial Loading ◽  
Plasticity Theory ◽  
True Value ◽  
Simple Tension ◽  
Elasto Plasticity ◽  
Tension And Compression

Residual stresses distribution after shot peening and its relaxation during uni-axial loading were investigated experimentally and theoretically on stainless steel of AISI304. An analytical model was proposed based upon continuum plasticity theory and elasto-plasticity finite element (FE) analysis, in which both relaxation of shot peening induced residual stress and variation of yield strength in the surface layer were taken into consideration. The results show that the value of yield strength in surface layer is altered after shot peening, and the relaxation of residual stress takes place at the point where the combination of applied strain and residual strain exceeds the true value of yield strength. A fundamental agreement was proved between measurements and predictions in simple tension and compression.

The development of a material model for cast iron that can be used for brake system analysis

2002 ◽  
Vol 216 (5) ◽  
pp. 349-362 ◽  
Author(s):  
S Koetniyom ◽  
P C Brooks ◽  
D C Barton
Keyword(s):  
Finite Element ◽  
Cast Iron ◽  
System Analysis ◽  
Preliminary Investigation ◽  
Material Model ◽  
Mechanical Tests ◽  
Brake Disc ◽  
Tension And Compression ◽  
High Plastic Strain ◽  
Iron Material

This paper describes the methodology and reports the results of detailed thermomechanical finite element analyses of cast iron brake discs under repeated high g braking conditions. The thermal analysis allows for heat loss from the vanes in a back-ventilated disc design as well as heat transfer to other parts of the brake assembly. The cast iron material properties required for the non-linear structural analysis are generated by mechanical tests on samples cut from the brake disc. The material model developed by the authors allows for the variation of flow stress with temperature and for the different yield properties of cast iron in tension and compression. The finite element results, derived from a preliminary investigation, indicate regions of high plastic strain accumulation which may lead to disc crazing and/or cracking and enable comparisons to be made between back- and front-vented rotor designs.

Study on Bauschinger Effect in X80 Steel under Axial Loading and Bending

2011 ◽  
Vol 197-198 ◽  
pp. 1686-1689 ◽  
Author(s):  
Ling Wang ◽  
Pu Rong Jia
Keyword(s):  
Plastic Strain ◽  
Yield Strength ◽  
Bauschinger Effect ◽  
Pipeline Steel ◽  
Axial Loading ◽  
Bending Moment ◽  
Experimental Tests ◽  
X80 Pipeline Steel ◽  
Tension And Compression ◽  
X80 Steel

The Bauschinger effect (BE) of X80 Pipeline Steel was tested through axial tension and compression loading. Forward and reverse axial loading schemes were performed to investigate the influence of deformation history on the mechanical character. The curves of forward and reverse stress-strain were both recorded. The results show that the yield strength decreases as the pre-plastic strain increases. On the basis of the experimental data, an empirical formula was derived regarding the decrement of the yield strength as a function of the pre-plastic strain. Additionally, further investigations on the BE of X80 steel were conducted by bending tests. The bending moment-strain curves were all recorded for both first and reverse loading. It shows that the yield moment also decreases as the pre-plastic strain increases. Based on the theory of elastic-plastic mechanics, the formula of yield moment decrement as the pre-plastic strain increase was obtained. The results show that the experimental tests are in good agreement with the formula prediction.

scholarly journals Yield-strength prediction of flattened steel pipes by competing Bauschinger effect and strain hardening during pipe-forming

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Dae Woong Kim ◽  
Wan-Keun Kim ◽  
Jin-ho Bae ◽  
Won-Doo Choi ◽  
Hyoung Seop Kim ◽  
...  
Keyword(s):  
Yield Strength ◽  
Strain Hardening ◽  
Bauschinger Effect ◽  
Strain Range ◽  
Granular Bainite ◽  
Strength Prediction ◽  
Line Pipe ◽  
Steel Pipes ◽  
Steel Sheets ◽  
Relationship Of

Abstract Since flattened steel sheets often show the unexpectedly lower or higher yield strength than leveled sheets, unceasing efforts have been made to accurately predict the yield strength in pipe-forming industries. In the present investigation, the yield strength of line-pipe or casing-pipe steels was predicted by competing Bauschinger effect and strain hardening occurred during the pipe-forming. Yield drop (YD) and yield rise (YR) parameters were newly defined from cyclic simulation analyses of outer and inner walls of pipes to express more reasonably the Bauschinger effect and strain hardening. The YD increased abruptly until the pre-strain of about 1%, and then saturated, while the YR increased linearly with increasing pre-strain. By combining the YD and YR, the variation in yield strength (Δσ) showed a down-and-up behavior as the Bauschinger effect and strain hardening were dominant at low and high pre-strains, respectively, and plausibly explained the relationship of Δσ and piping strain used in pipe-forming industries. According to the microstructural analyses related to the down-and-up Δσ behavior, the polygonal ferrite reduced the yield-strength reduction in the low pre-strain range, whereas the granular bainite or pearlite expanded it. This yield strength prediction coupled with microstructural analyses provide a good idea for designing and reliably predicting the yield strength of in various steel pipes.

Evaluation of the residual stress in stainless steel 304L hydraulically expanded joints

2020 ◽  
pp. 095440892096401
Author(s):  
Ying Hong ◽  
Xuesheng Wang ◽  
Yan Wang ◽  
Zhao Zhang ◽  
Yong Han
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Yield Strength ◽  
Residual Stresses ◽  
Heat Exchangers ◽  
Nuclear Power ◽  
The Finite Element Method ◽  
Power Stations ◽  
Stainless Steel 304 ◽  
Initial Clearance

Stainless steel 304 L tubes are commonly used in the fabrication of heat exchangers for nuclear power stations. The stress corrosion cracking (SCC) of 304 L tubes in hydraulically expanded tube-to-tubesheet joints is the main reason for the failure of heat exchangers. In this study, 304 L hydraulically expanded joint specimens were prepared and the residual stresses of a tube were evaluated with both an experimental method and the finite element method (FEM). The residual stresses in the outer and inner surfaces of the tube were measured by strain gauges. The expanding and unloading processes of the tube-to-tubesheet joints were simulated by the FEM. Furthermore, an SCC test was carried out to verify the results of the experimental measurement and the FEM. There was good agreement between the FEM and the experimental results. The distribution of the residual stress of the tube in the expanded joint was revealed by the FEM. The effects of the expansion pressure, initial tube-to-hole clearance, and yield strength of the tube on the residual stress in the transition zone that lay between the expanded and unexpanded region of the tube were investigated. The results showed that the residual stress of the expanded joint reached the maximum value when the initial clearance was eliminated. The residual stress level decreased with the decrease of the initial tube-to-hole clearance and yield strength. Finally, an effective method that would reduce the residual stress without losing tightness was proposed.

Wrinkling Prediction and Optimization of Sheet Metal Forming Process by Numerical Simulation

2015 ◽  
Vol 818 ◽  
pp. 252-255 ◽  
Author(s):  
Ján Slota ◽  
Marek Šiser
Keyword(s):  
Numerical Simulation ◽  
Material Model ◽  
Mechanical Tests ◽  
Simulation Software ◽  
Forming Process ◽  
Part Geometry ◽  
Nominal Thickness ◽  
430 Stainless Steel ◽  
Metal Forming Process ◽  
Aisi 430

The paper deals with optimization of forming process for AISI 430 stainless steel with nominal thickness 0.4 mm. During forming of sidewall for washing machine drum, some wrinkles remain at the end of forming process in some places. This problem was solved by optimization the geometry of the drawpiece using numerical simulation. During optimization a series of modifications of the part geometry to absolute elimination of wrinkling was performed. On the basis of mechanical tests, the material model was created and imported into the material database of Autoform simulation software.

Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress

2000 ◽  
Vol 123 (1) ◽  
pp. 150-154
Author(s):  
John H. Underwood ◽  
Michael J. Glennon
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Fatigue Life ◽  
Yield Strength ◽  
Residual Stresses ◽  
Solid Mechanics ◽  
Element Model ◽  
Pressure Vessels ◽  
Material Strength ◽  
Element Analysis

Laboratory fatigue life results are summarized from several test series of high-strength steel cannon breech closure assemblies pressurized by rapid application of hydraulic oil. The tests were performed to determine safe fatigue lives of high-pressure components at the breech end of the cannon and breech assembly. Careful reanalysis of the fatigue life tests provides data for stress and fatigue life models for breech components, over the following ranges of key parameters: 380–745 MPa cyclic internal pressure; 100–160 mm bore diameter cannon pressure vessels; 1040–1170 MPa yield strength A723 steel; no residual stress, shot peen residual stress, overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid mechanics analysis. Shot peen and overload residual stresses are modeled by superposing typical or calculated residual stress distributions on the applied stresses. Overload residual stresses are obtained directly from the finite element model of the breech, with the breech overload applied to the model in the same way as with actual components. Modeling of the fatigue life of the components is based on the fatigue intensity factor concept of Underwood and Parker, a fracture mechanics description of life that accounts for residual stresses, material yield strength and initial defect size. The fatigue life model describes six test conditions in a stress versus life plot with an R2 correlation of 0.94, and shows significantly lower correlation when known variations in yield strength, stress concentration factor, or residual stress are not included in the model input, thus demonstrating the model sensitivity to these variables.

Prediction for Post-Forming Spring Back of CICC in the Superconducting Tokamak Fusion Device via Virtual Manufacturing

2000 ◽  
Author(s):  
Yeong Sung Suh ◽  
Jong Sung Ahn ◽  
Sun Woong Choi ◽  
Hyun Ki Park ◽  
Yong Jin Kim ◽  
...  
Keyword(s):  
Residual Stress ◽  
Cross Section ◽  
Virtual Manufacturing ◽  
Von Mises Stress ◽  
Radius Of Curvature ◽  
Spring Back ◽  
Cross Sectional ◽  
Fusion Device ◽  
Roll Bending ◽  
Superconducting Tokamak

Abstract To construct the CICC for the superconducting Tokamak fusion device, the 3-roll bending, that inherently has a difficulty to form the coil with accurate radius of curvature, is used for continuous winding. In order to obtain precise dimension, a trial-an-error operation is inevitable. To reduce the effort of tryout, a relation between travel of the bending roller and spring back displacement was obtained via virtual manufacturing. The radius of CICC after forming was expressed as a function of the bend-roll travel. Next, the variation of the CICC cross-section (reduction of the conduit cross-section) was investigated during the first turn and during conduit bending with largest curvature. With largest curvature, the cross-sectional area was not much reduced. Finally, the residual stress on the CICC before roll bending was measured in order to examine the influence of the original residual stress on the final deformation behavior. The principal stress and von Mises stress were measured at the surface of CICC using specially designed strain gauge. The measured values were considered in the virtual forming. The results indicate that the residual stresses generated during the fabrication of the CICC (before coiling) do not have much influence on the final stress state.

Structure Assessment Using Instrumented Indentation: Strength, Toughness and Residual Stress

2018 ◽  
Author(s):  
Dongil Kwon ◽  
Jong Hyoung Kim ◽  
Ohmin Kwon ◽  
Woojoo Kim ◽  
Sungki Choi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Residual Stress ◽  
Tensile Properties ◽  
Hole Drilling ◽  
Uniaxial Tensile ◽  
Small Scale ◽  
Specimen Preparation ◽  
Instrumented Indentation ◽  
Uniaxial Tensile Testing

The instrumented indentation technique (IIT) is a novel method for evaluating mechanical properties such as tensile properties, toughness and residual stress by analyzing the indentation load-depth curve measured during indentation. It can be applied directly on small-scale and localized sections in industrial structures and structural components since specimen preparation is very easy and the experimental procedure is nondestructive. We introduce the principles for measuring mechanical properties with IIT: tensile properties by using a representative stress and strain approach, residual stress by analyzing the stress-free and stressed-state indentation curves, and fracture toughness of metals based on a ductile or brittle model according to the fracture behavior of the material. The experimental results from IIT were verified by comparing results from conventional methods such as uniaxial tensile testing for tensile properties, mechanical saw-cutting and hole-drilling methods for residual stress, and CTOD test for fracture toughness.

Detection and In-Field Verification of Potential Pipeline Expansion Due to Low Yield Strength Pipe in High Strength Line Pipe

2010 ◽  
Author(s):  
Jill Braun ◽  
Stuart Clouston
Keyword(s):  
High Resolution ◽  
Yield Strength ◽  
Measurement Errors ◽  
High Strength ◽  
Lessons Learned ◽  
Chemical Compositions ◽  
Line Pipe ◽  
Variable Yield ◽  
Field Verification ◽  
Pipe Joints

On May 21, 2009, the Pipeline & Hazardous Materials Safety Administration (PHMSA) issued an Advisory Bulletin (PHMSA-2009-0148) entitled, “Potential for Low and Variable Yield, Tensile Strength and Chemical Compositions in High Strength Line Pipe” [1] recommending that pipeline operators investigate whether recently constructed pipelines contain pipe joints not meeting the minimum specification requirements (74FR2390). Based on PHMSA’s technical reviews, high resolution deformation tool inspection combined with comprehensive infield verification has been recommended in accordance with the “Interim Guidelines for Confirming Pipe Strength in Pipe Susceptible to Low Yield Strength,” issued by PHMSA in September 2009[2]. Kern River Gas Transmission Company (Kern River) underwent a detailed program of engineering and assessment in order to proactively demonstrate compliance with the interim guidelines. This paper discusses the process, inspection results and infield verifications performed by the pipeline operator. In particular, detailed consideration to the methodology of detection and assessment of potential pipeline expansions is presented with discussion on the special considerations needed for low level anomaly identification, reporting and verification of expansions as defined in the PHMSA guidelines. High resolution caliper analysis approaches developed for this particular application are discussed and appropriate techniques are recommended that consider the effects of possible asymmetry of expansions and impact of other deformations such as ovality. Field verification practices and findings are reviewed in detail with particular focus on the challenges facing the pipeline operator in resolving both tool and in-field measurement errors that can significantly impact the number of identifiable candidate expansions for verification. In conclusion, an overview of the assessment criteria and field activity to comply with the PHMSA interim guidelines are presented along with the lessons learned from the analysis, verification and remediation steps that may assist other pipeline operators as they address these newly established regulatory requirements.

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