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Brian N. Leis - One of the best experts on this subject based on the ideXlab platform.
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Finite Element Analysis of Burst Pressure for Pipelines With Long Corrosion Defects
Volume 6: Materials and Fabrication Parts A and B, 2012Co-Authors: Xian-kui Zhu, Brian N. LeisAbstract:Plastic collapse analysis and remaining burst strength determination are critical to a corroded pipeline in its fitness-for-service analysis and integrity assessment. For very long corrosion defects, the present authors proposed a theoretical solution for predicting the burst pressure of corroded pipe in terms of a newly developed Average Shear Stress yield theory, and validated it using full-scale burst data for long real corrosion defects. This paper then presents a finite element analysis (FEA) procedure to determine the remaining burst pressure for a very long blunt defect. A burst failure criterion that is referred to as von Mises equivalent Stress criterion is proposed first in reference to the von Mises theory. Detailed elastic-plastic FEA calculations are performed using ABAQUS for a series of corroded pipes with infinitely long defects in different widths. From the FEA results and using the proposed failure criterion, the numerical results of burst pressure are determined for the long defects. The results show that using the proposed failure criterion, the FEA simulation can accurately determine the burst pressure for corroded pipes with long defects that is consistent with the theoretical solution. The conventional assessment methods including ASME B31G, RSTRENG, PCORRC and LPC are also evaluated and discussed in comparison with the proposed theoretical solution of burst pressure for long corrosion defects.
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Determination of Burst Pressure for Line Pipes With Long Blunt Defects
Volume 6: Materials and Fabrication Parts A and B, 2011Co-Authors: Xian-kui Zhu, Brian N. LeisAbstract:Burst pressure is the maximum load in a pipeline. Its accurate prediction is critical to the safety design, integrity assessment and operational management of the pipeline. This paper overviews the commonly-used corrosion assessment methods, including ASME B31G, Modified B31G, LPC and PCORRC criteria, and describes three theoretical solutions of burst pressure for defect-free pipes in terms of Tresca criterion, von Mises criterion and ZL criterion — a newly proposed Average Shear Stress yield criterion and the associated flow rules. These three theoretical solutions are extended to those for corroded pipes with infinitely long corrosion defects. Followed this, an elastic-plastic finite element analysis is performed using the commercial software ABAQUS with an aim to demonstrate numerical determination of burst pressure corresponding to the Mises and ZL solutions. The corrosion assessment methods are then applied to evaluate the burst pressure for six corroded line pipes with real long corrosion defects. It is concluded that the ZL solution and the PCORRC criterion can determine reasonable and conservative predictions for corroded pipelines with very long corrosion defects.Copyright © 2011 by ASME
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Effect of Axial Tensile Strain on Yield Load-Carrying Capacity of Pipelines
2010 8th International Pipeline Conference Volume 4, 2010Co-Authors: Xian-kui Zhu, Brian N. LeisAbstract:This paper theoretically investigates the effect of axial tensile strain on the plastic yield load-carrying capacity of pipelines. The elasticity theory and three plastic yield criteria of Tresca criterion, von Mises criterion, and Average Shear Stress Yield (ASSY) criterion are adopted in the analysis. General solutions of elastic Stresses and strains are obtained for a thin-walled, end-caped pipe subjected to internal pressure and an axial strain that is used to represent the outside applied force. Based on the three plastic yield criteria, different nonlinear governing equations are obtained for determining the yield pressure, the yield hoop and axial Stresses as well as the yield hoop and radial strains for the pipe. The results showed that the pressure, Stresses and strains in the pipe at yield are functions of the axial strain, Poisson’s ratio, Young’s modulus, and yield strength of the pipe steel. The tensile strain limits are then obtained for different pipeline grades. It is concluded that the axial tensile strain can significantly reduce the limit load or the regulation-allowed operating pressure, and the tensile strain limits should be considered in strain-based design to prevent pipeline failure.Copyright © 2010 by ASME
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Average Shear Stress yield criterion and its application to plastic collapse analysis of pipelines
International Journal of Pressure Vessels and Piping, 2006Co-Authors: Xian-kui Zhu, Brian N. LeisAbstract:Abstract It is known that available analytical and empirical solutions for the burst pressure of defect-free line pipes cannot broadly fit experimental data for different materials. Usually the Tresca prediction provides a lower bound to the burst pressure, and the von Mises prediction provides an upper bound to the burst pressure. A new multiaxial yield criterion, referred to as the Average Shear Stress yield (ASSY) criterion for isotropic hardening materials, is developed in this paper based on the traditional Tresca and von Mises yield criteria so that the burst pressure of a pipeline at plastic collapse can be accurately predicted. As an application of the proposed criterion to the plastic collapse analysis of pipelines, an ASSY-based solution for defect-free line pipes is obtained and formulated as a function of the pipe geometry, the strain hardening exponent and the ultimate tensile Stress. Extensive experimental results are then adopted to validate the proposed solutions. Comparisons indicate that (1) the ASSY criterion can well fit the classical experimental data of different ductile metals for both initial and subsequent plastic yielding of a material; and (2) the ASSY-based solution of pipeline burst pressure closely matches the Average experimental data for the burst pressure of defect-free pipes for various pipeline steels.
Xian-kui Zhu - One of the best experts on this subject based on the ideXlab platform.
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Finite Element Analysis of Burst Pressure for Pipelines With Long Corrosion Defects
Volume 6: Materials and Fabrication Parts A and B, 2012Co-Authors: Xian-kui Zhu, Brian N. LeisAbstract:Plastic collapse analysis and remaining burst strength determination are critical to a corroded pipeline in its fitness-for-service analysis and integrity assessment. For very long corrosion defects, the present authors proposed a theoretical solution for predicting the burst pressure of corroded pipe in terms of a newly developed Average Shear Stress yield theory, and validated it using full-scale burst data for long real corrosion defects. This paper then presents a finite element analysis (FEA) procedure to determine the remaining burst pressure for a very long blunt defect. A burst failure criterion that is referred to as von Mises equivalent Stress criterion is proposed first in reference to the von Mises theory. Detailed elastic-plastic FEA calculations are performed using ABAQUS for a series of corroded pipes with infinitely long defects in different widths. From the FEA results and using the proposed failure criterion, the numerical results of burst pressure are determined for the long defects. The results show that using the proposed failure criterion, the FEA simulation can accurately determine the burst pressure for corroded pipes with long defects that is consistent with the theoretical solution. The conventional assessment methods including ASME B31G, RSTRENG, PCORRC and LPC are also evaluated and discussed in comparison with the proposed theoretical solution of burst pressure for long corrosion defects.
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Determination of Burst Pressure for Line Pipes With Long Blunt Defects
Volume 6: Materials and Fabrication Parts A and B, 2011Co-Authors: Xian-kui Zhu, Brian N. LeisAbstract:Burst pressure is the maximum load in a pipeline. Its accurate prediction is critical to the safety design, integrity assessment and operational management of the pipeline. This paper overviews the commonly-used corrosion assessment methods, including ASME B31G, Modified B31G, LPC and PCORRC criteria, and describes three theoretical solutions of burst pressure for defect-free pipes in terms of Tresca criterion, von Mises criterion and ZL criterion — a newly proposed Average Shear Stress yield criterion and the associated flow rules. These three theoretical solutions are extended to those for corroded pipes with infinitely long corrosion defects. Followed this, an elastic-plastic finite element analysis is performed using the commercial software ABAQUS with an aim to demonstrate numerical determination of burst pressure corresponding to the Mises and ZL solutions. The corrosion assessment methods are then applied to evaluate the burst pressure for six corroded line pipes with real long corrosion defects. It is concluded that the ZL solution and the PCORRC criterion can determine reasonable and conservative predictions for corroded pipelines with very long corrosion defects.Copyright © 2011 by ASME
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Limit Load Analysis of Cylindrical Vessels Under Internal Pressure and Axial Strain
Volume 6: Materials and Fabrication Parts A and B, 2011Co-Authors: Xian-kui ZhuAbstract:Strain-based design is a newer technology used in safety design and integrity management of oil and gas pipelines. In a traditional Stress-based design, the axial Stress is relatively small compared to the hoop Stress generated by internal pressure in a line pipe, and the limit state in the pipeline is usually load-controlled. In a strain-based design, however, axial strain can be large and the load-carrying capacity of pipelines could be reduced significantly below an allowed operating pressure, where the limit state is controlled by an axial strain. In this case, the limit load analysis is of great importance. The present paper confirms that the Stress, strain and load-carrying capacity of a thin-walled cylindrical pressure vessel with an axial force are equivalent those of a long pressurized pipeline with an axial tensile strain. Elastic Stresses and strains in a pressure vessel are then investigated, and the limit Stress, limit strain and limit pressure are obtained in terms of the classical Tresca criterion, von Mises criteria, and a newly proposed Average Shear Stress yield criterion. The results of limit load solutions are analyzed and validated using typical experimental data at plastic yield.Copyright © 2011 by ASME
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Effect of Axial Tensile Strain on Yield Load-Carrying Capacity of Pipelines
2010 8th International Pipeline Conference Volume 4, 2010Co-Authors: Xian-kui Zhu, Brian N. LeisAbstract:This paper theoretically investigates the effect of axial tensile strain on the plastic yield load-carrying capacity of pipelines. The elasticity theory and three plastic yield criteria of Tresca criterion, von Mises criterion, and Average Shear Stress Yield (ASSY) criterion are adopted in the analysis. General solutions of elastic Stresses and strains are obtained for a thin-walled, end-caped pipe subjected to internal pressure and an axial strain that is used to represent the outside applied force. Based on the three plastic yield criteria, different nonlinear governing equations are obtained for determining the yield pressure, the yield hoop and axial Stresses as well as the yield hoop and radial strains for the pipe. The results showed that the pressure, Stresses and strains in the pipe at yield are functions of the axial strain, Poisson’s ratio, Young’s modulus, and yield strength of the pipe steel. The tensile strain limits are then obtained for different pipeline grades. It is concluded that the axial tensile strain can significantly reduce the limit load or the regulation-allowed operating pressure, and the tensile strain limits should be considered in strain-based design to prevent pipeline failure.Copyright © 2010 by ASME
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theoretical and numerical predictions of burst pressure of pipelines
Journal of Pressure Vessel Technology-transactions of The Asme, 2007Co-Authors: Xian-kui Zhu, Ia N LeisAbstract:To accurately characterize plastic yield behavior of metals in multiaxial Stress states, a new yield theory, i.e., the Average Shear Stress yield (ASSY) theory, is proposed in reference to the classical Tresca and von Mises yield theories for isotropic hardening materials. Based on the ASSY theory, a theoretical solution for predicting the burst pressure of pipelines is obtained as a function of pipe diameter, wall thickness, material hardening exponent, and ultimate tensile strength. This solution is then validated by experimental data for various pipeline steels. According to the ASSY yield theory, four failure criteria are developed for predicting the burst pressure of pipes by the use of commercial finite element softwares such as ABAQUS and ANSYS , where the von Mises yield theory and the associated flow rule are adopted as the classical metal plasticity model for isotropic hardening materials. These failure criteria include the von Mises equivalent Stress criterion, the maximum principal Stress criterion, the von Mises equivalent strain criterion, and the maximum tensile strain criterion. Applications demonstrate that the proposed failure criteria in conjunction with the ABAQUS or ANSYS numerical analysis can effectively predict the burst pressure of end-capped line pipes.
Corey S O'hern - One of the best experts on this subject based on the ideXlab platform.
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Measurements of the yield Stress in frictionless granular systems.
Physical review. E Statistical nonlinear and soft matter physics, 2006Co-Authors: Corey S O'hernAbstract:We perform extensive molecular dynamics simulations of two-dimensional frictionless granular materials to determine whether these systems can be characterized by a single static yield Shear Stress. We consider boundary-driven planar Shear at constant volume and either constant Shear force or constant Shear velocity. Under steady flow conditions, these two ensembles give similar results for the Average Shear Stress versus Shear velocity. However, near jamming it is possible that the Shear Stress required to initiate Shear flow can differ substantially from the Shear Stress required to maintain flow. We perform several measurements of the Shear Stress near the initiation and cessation of flow. At fixed Shear velocity, we measure the Average Shear Stress Sigma(yv) in the limit of zero Shear velocity. At fixed Shear force, we measure the minimum Shear Stress Sigma(yf) required to maintain steady flow at long times. We find that in finite-size systems Sigma(yf) > Sigma(yv), which implies that there is a jump discontinuity in the Shear velocity from zero to a finite value when these systems begin flowing at constant Shear force. However, our simulations suggest that the difference Sigma(yf) - Sigma(yv), and thus the discontinuity in the Shear velocity, tend to zero in the infinite-system-size limit. Thus, our results imply that in the large-system limit, frictionless granular systems can be characterized by a single static yield Shear Stress. We also monitor the short-time response of these systems to applied Shear and show that the packing fraction of the system and shape of the velocity profile can strongly influence whether or not the Shear Stress at short times overshoots the long-time Average value.
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Measurements of the yield Stress in frictionless granular systems
Physical Review E, 2006Co-Authors: Corey S O'hernAbstract:We perform extensive molecular dynamics simulations of 2D frictionless granular materials to determine whether these systems can be characterized by a single static yield Shear Stress. We consider boundary-driven planar Shear at constant volume and either constant Shear force or constant Shear velocity. Under steady flow conditions, these two ensembles give similar results for the Average Shear Stress versus Shear velocity. However, near jamming it is possible that the Shear Stress required to initiate Shear flow can differ substantially from the Shear Stress required to maintain flow. We perform several measurements of the Shear Stress near the initiation and cessation of flow. At fixed Shear velocity, we measure the Average Shear Stress $\Sigma_{yv}$ in the limit of zero Shear velocity. At fixed Shear force, we measure the minimum Shear Stress $\Sigma_{yf}$ required to maintain steady flow at long times. We find that in finite-size systems $\Sigma_{yf} > \Sigma_{yv}$, which implies that there is a jump discontinuity in the Shear velocity from zero to a finite value when these systems begin flowing at constant Shear force. However, our simulations show that the difference $\Sigma_{yf} - \Sigma_{yv}$, and thus the discontinuity in the Shear velocity, tend to zero in the infinite system size limit. Thus, our results indicate that in the large system limit, frictionless granular systems are characterized by a single static yield Shear Stress. We also monitor the short-time response of these systems to applied Shear and show that the packing fraction of the system and shape of the velocity profile can strongly influence whether or not the Shear Stress at short times overshoots the long-time Average value.Comment: 7 pages and 6 figure
R E Ávila - One of the best experts on this subject based on the ideXlab platform.
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A variational model for Shear Stress in friction stir welding based on the weld shape in transverse sections
Modelling and Simulation in Materials Science and Engineering, 2006Co-Authors: R E ÁvilaAbstract:A model is proposed to interpret observed shapes of transverse cross sectional macrostructures in aluminium friction stir welds. The model applies calculus of variations to minimize a functional corresponding to the work done to Shear the material rotating around the tool, thus allowing calculation of an Average value for the Shear Stress on the outer Shearing surface around the carousel, as a function of the radial position only and independent of the angular position on that surface. The main point is that there is valuable information to be obtained from observing the geometry of the outer shape of the carousel. Thus, a formula is given to calculate the distribution of the Average Shear Stress at the interface between the rotating material and the nearly stationary base material, on the basis of the observed weld shape.
Larry V. Mcintire - One of the best experts on this subject based on the ideXlab platform.
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Endothelial cell responses to atheroprone flow are driven by two separate flow components: low time-Average Shear Stress and fluid flow reversal.
American journal of physiology. Heart and circulatory physiology, 2009Co-Authors: Daniel E. Conway, Marcie R. Williams, Suzanne G. Eskin, Larry V. McintireAbstract:To simulate the effects of Shear Stress in regions of the vasculature prone to developing atherosclerosis, we subjected human umbilical vein endothelial cells to reversing Shear Stress to mimic the...
