The Experts below are selected from a list of 131034 Experts worldwide ranked by ideXlab platform
Colin Cross - One of the best experts on this subject based on the ideXlab platform.
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Subsea Pipeline Lateral Buckling Design—Strain Concentration or Strain Capacity Reduction Factors
Journal of Offshore Mechanics and Arctic Engineering, 2018Co-Authors: M. Liu, Colin CrossAbstract:A Strain concentration factor is typically incorporated in the higher-pressure and high-temperature (HPHT) pipeline lateral buckling assessment to account for nonuniform stiffness or plastic bending moment. Increased Strain concentration can compromise pipeline low cycle fatigue and lateral buckling capacity, leading to an early onset of local buckling failure. In this paper, the philosophy of local buckling mitigation using the Strain concentration factor is examined. The local buckling behavior is evaluated. Global Strain reduction and evolution against buckling are analyzed with respect to varying joint mismatch level. The concept of a Strain reduction factor (SNRF) due to joint mismatch is developed based on the global Strain capacity reduction with reference to the uniform configuration. It is demonstrated that the SNRF in terms of Strain capacity reduction is a unique characteristic parameter. As opposed to Strain concentration, it is an invariant insensitive to evaluation methods and Design Strain demand level, hence more representative as a limiting Design metric to maintain the safety margin. The rationale for its introduction as an alternative to the Strain concentration factor is outlined and its benefits are established. The method for obtaining the SNRF and its application is developed. The discernible difference and scenarios for application of either factor are discussed, including low and high cycle fatigue, linearity and stress concentration, engineering criticality assessment (ECA), and lateral buckling. Additional causal factors giving rise to mismatch such as pipe schedule transition and buckler arrestor are also discussed. Iterations of finite element (FE) analyses are performed for a pipe-in-pipe (PIP) configuration in a case study.
M. Liu - One of the best experts on this subject based on the ideXlab platform.
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Subsea Pipeline Lateral Buckling Design—Strain Concentration or Strain Capacity Reduction Factors
Journal of Offshore Mechanics and Arctic Engineering, 2018Co-Authors: M. Liu, Colin CrossAbstract:A Strain concentration factor is typically incorporated in the higher-pressure and high-temperature (HPHT) pipeline lateral buckling assessment to account for nonuniform stiffness or plastic bending moment. Increased Strain concentration can compromise pipeline low cycle fatigue and lateral buckling capacity, leading to an early onset of local buckling failure. In this paper, the philosophy of local buckling mitigation using the Strain concentration factor is examined. The local buckling behavior is evaluated. Global Strain reduction and evolution against buckling are analyzed with respect to varying joint mismatch level. The concept of a Strain reduction factor (SNRF) due to joint mismatch is developed based on the global Strain capacity reduction with reference to the uniform configuration. It is demonstrated that the SNRF in terms of Strain capacity reduction is a unique characteristic parameter. As opposed to Strain concentration, it is an invariant insensitive to evaluation methods and Design Strain demand level, hence more representative as a limiting Design metric to maintain the safety margin. The rationale for its introduction as an alternative to the Strain concentration factor is outlined and its benefits are established. The method for obtaining the SNRF and its application is developed. The discernible difference and scenarios for application of either factor are discussed, including low and high cycle fatigue, linearity and stress concentration, engineering criticality assessment (ECA), and lateral buckling. Additional causal factors giving rise to mismatch such as pipe schedule transition and buckler arrestor are also discussed. Iterations of finite element (FE) analyses are performed for a pipe-in-pipe (PIP) configuration in a case study.
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Subsea Pipeline Lateral Buckling Design: Strain Concentration or Strain Reduction Factors
Volume 5B: Pipelines Risers and Subsea Systems, 2017Co-Authors: M. LiuAbstract:Strain based Design is normally applied for HPHT pipelines when the conventional stress based method becomes impractical. In addition to a Design safety factor, a Strain concentration factor is typically incorporated in the lateral buckling assessment to account for non-uniform stiffness or plastic bending moment due to geometry and material strength mismatch between adjacent pipe joints. Increased Strain concentration can compromise pipeline low cycle fatigue and lateral buckling capacity, leading to an early onset of local buckling failure. In this paper, the philosophy of local buckling mitigation using the Strain concentration factor is examined. The local buckling behaviour is evaluated in relation to Strain concentration. Global Strain reduction and evolution against buckling is analysed with respect to varying joint mismatch level derived according to a structural reliability analysis. The concept of a Strain reduction factor due to mismatch is developed and proposed based on the global Strain capacity reduction with reference to the uniform configuration. It is demonstrated that the Strain reduction factor is a unique characteristic parameter. As opposed to Strain concentrations it is an invariant insensitive to evaluation methods and the Design Strain demand level, hence more representative as a limiting Design metric to maintain the safety margin. The use of the Strain reduction factor is thus put forward in Strain based lateral buckling Design as an alternative to using the Strain concentration factor. The method for obtaining the Strain reduction factor and its application is developed. The rationale for its introduction is outlined and some of its benefits are established. The discernible difference and scenarios for application of either factors are discussed, including low and high cycle fatigue, linearity and stress concentration (SNCF from SCF for welds), ECA and lateral buckling. Additional causal factors giving rise to mismatch such as pipe schedule transition and buckler arrestor are also discussed. Iterations of FE analyses are performed for a pipe-in-pipe configuration in a case study.
Karl-heinz Schleifer - One of the best experts on this subject based on the ideXlab platform.
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Development of a modified subtraction hybridization technique and its application for the Design of Strain specific PCR systems for lactococci
FEMS Microbiology Letters, 1998Co-Authors: Lars Wassill, Wolfgang Ludwig, Karl-heinz SchleiferAbstract:A modified genomic DNA subtraction hybridization approach for the Design of Strain specific PCR systems was developed and evaluated. The method is based on the magnetic separation of homologous and heterologous hybrids of amplified reference (subtracter) and target (probe) DNA fragments from probe specific fragments. The sequence data of the latter fragments were used for diagnostic primer Design. Strain diagnostic PCR systems were Designed and evaluated for Lactococcus lactis subsp. lactis Strains WS1678, NIZO 3F27, WS1684 and NIZO L5K5I. At least one of the primers may be used as a Strain specific hybridization probe.
George P. Kouretzis - One of the best experts on this subject based on the ideXlab platform.
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stress analysis of buried steel pipelines at strike slip fault crossings
Soil Dynamics and Earthquake Engineering, 2007Co-Authors: Dimitris K Karamitros, George D. Bouckovalas, George P. KouretzisAbstract:Existing analytical methods for the stress analysis of buried steel pipelines at crossings with active strike-slip faults depend on a number of simplifications, which limit their applicability and may even lead to non-conservative results. The analytical methodology presented herein maintains the well-established assumptions of existing methodologies, but also introduces a number of refinements in order to achieve a more wide range of application without any major simplicity sacrifice. More specifically, it employs equations of equilibrium and compatibility of displacements to derive the axial force applied on the pipeline and adopts a combination of beam-on-elastic-foundation and elastic-beam theory to calculate the developing bending moment. Although indirectly, material and large-displacement non-linearities are also taken into account, while the actual distribution of stresses on the pipeline cross-section is considered for the calculation of the maximum Design Strain. The proposed methodology is evaluated against the results of a series of benchmark 3D non-linear analyses with the finite element method. It is shown that fairly accurate predictions of pipeline Strains may be obtained for a wide range of crossing angles and fault movement magnitudes encountered in practice.
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ANALYTICAL VERIFICATION OF BURIED STEEL PIPELINES AT STRIKE-SLIP FAULT CROSSINGS
2007Co-Authors: Dimitris K Karamitros, George D. Bouckovalas, George P. KouretzisAbstract:Existing analytical methods for the stress analysis of buried steel pipelines at crossings with active strike-slip faults depend on a number of simplifications, which limit their applicability and may even lead to non-conservative results. The analytical methodology presented herein maintains the wellestablished assumptions of existing methodologies, but also introduces a number of refinements in order to achieve a more wide range of application without any major simplicity sacrifice. More specifically, it employs equations of equilibrium and compatibility of displacements to derive the axial force applied on the pipeline and adopts a combination of beam-on-elastic-foundation and elasticbeam theory to calculate the developing bending moment. Although indirectly, material and largedisplacement non-linearities are also taken into account, while the actual distribution of stresses on the pipeline cross-section is considered for the calculation of the maximum Design Strain.
Daniel Sánchez-portal - One of the best experts on this subject based on the ideXlab platform.
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Strain-Tunable Spin Moment in Ni-Doped Graphene
The Journal of Physical Chemistry C, 2011Co-Authors: Elton J. G. Santos, Andrés Ayuela, Daniel Sánchez-portalAbstract:Graphene, due to its exceptional properties, is a promising material for nanotechnology applications. In this context, the ability to tune the properties of graphene-based materials and devices with the incorporation of defects and impurities can be of extraordinary importance. Here, we investigate the effect of uniaxial tensile Strain on the electronic and magnetic properties of graphene doped with substitutional Ni impurities (Nisub). We have found that, although Nisub defects are nonmagnetic in the relaxed layer, uniaxial Strain induces a spin moment in the system. The spin moment increases with the applied Strain up to values of 0.3–0.4 μB per Nisub, until a critical Strain of ∼6.5% is reached. At this point, a sharp transition to a high-spin state (∼1.9 μB) is observed. This magnetoelastic effect could be utilized to Design Strain-tunable spin devices based on Ni-doped graphene.