Fabrication Uncertainty in B2 for Nuclear Pipe Bends Subjected to In-Plane Opening Moment

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Pronab Roy ◽  
Siddhartha Ghosh
Keyword(s):  
Random Variable ◽  
Nonlinear Finite Element ◽  
Conservative Estimate ◽  
Element Analysis ◽  
Stress Indices ◽  
Primary Stress ◽  
Reliability Based Design ◽  
Probabilistic Characterization ◽  
Geometric Uncertainty

For reliability-based design of pipe bends and elbows, a probabilistic characterization of the primary stress indices (B1 and B2) is essential. This paper aims at the characterization of the fabrication/geometric uncertainty in B2, for thin stainless steel long radius pipe bends, subjected to in-plane opening moment. This characterization is performed in a framework based on Monte Carlo simulation and nonlinear finite element analysis. A revision of the code-based expression for B2 is proposed where a random variable K replaces the constant numerator in this expression. The statistics for K are provided for different pipe nominal dimensions, which indicates that the existing provision gives a very conservative estimate of the plastic collapse moment for pipe bends subjected to in-plane opening flexure.

Probabilistic Characterization of an Allowable Design Moment in a Piping Elbow

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Yonghee Ryu ◽  
Abhinav Gupta ◽  
Bu Seog Ju
Keyword(s):  
Nuclear Power ◽  
Stress Index ◽  
Design Equation ◽  
Design Code ◽  
Straight Pipe ◽  
Reliability Level ◽  
Reliability Based Design ◽  
Probabilistic Characterization ◽  
Definition Of

The design of a nuclear power plant piping requires consideration of the effects of pressure and moment loads according to the appropriate design equation, which is Piping design equation (9) in NC/ND-3600, Section III of the ASME Boiler and Pressure Vessel Code. The design moment is influenced significantly by the definition of the B2 stress index in piping elbows. This paper presents a study on reliability-based design for piping elbows on the level D service limit in the design code. Probability density functions (PDFs) of the design moment were calculated using the ASME equation and modified B2 equations. The PDFs of the design moment were evaluated by the collapse moment using the closed-form equations. The probability distribution of the design moment using the modified B2 equation was closer to the distributions of the collapse moment than its design moment using the ASME B2 equation. Probabilistic analyses were conducted to evaluate reliability levels in straight pipe as well as piping elbows using the ASME and modified B2 equations. It was observed that the minimum reliability level (MRL) of the design equation for the straight pipe was slightly higher than the MRL of the elbow. The MRLs of the design equation using the ASME and modified B2 equations were similar for the same values of bend parameter h, and the MRL of the design equation did not show influence of changes in bend parameter, piping type, and B2 stress index.

Structural mechanics characterization of steel intermeshed connection using nonlinear finite element analysis

2021 ◽  
Vol 238 ◽  
pp. 112264
Author(s):  
Mohammad E. Shemshadian ◽  
Arturo E. Schultz ◽  
Jia-Liang Le ◽  
Debra F. Laefer ◽  
Salam Al-Sabah ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Nonlinear Finite Element Analysis ◽  
Structural Mechanics ◽  
Nonlinear Finite Element ◽  
Element Analysis

Development of the Primary Stress Indices and Primary Plus Secondary Stress Indices for Pipe Cross Connection

2015 ◽  
Author(s):  
Timothy M. Adams ◽  
Jie Wen
Keyword(s):  
Branch Pipe ◽  
Bending Moments ◽  
Bending Stress ◽  
Secondary Stress ◽  
Element Analysis ◽  
Stress Indices ◽  
Primary Stress ◽  
Pipe Model ◽  
Stress Components ◽  
Cross Connection

The current ASME Boiler Pressure Vessel Code doesn’t provide the primary stress indices (B2) and primary plus secondary stress indices (C2) for a pipe cross connection. In this study, two types of Finite Element Analysis (FEA) models were created to calculate the stress indices for such a configuration: the first was a 3D solid model to calculate the stress intensities and the second a simplified pipe model to calculate the bending moments to obtain the pipe nominal stresses. For both types of FEA models, loads were applied in one direction at either run pipe or branch pipe to ensure in-plane or out-of-plane bending moments were produced in the model. This analysis includes 28 cases for multiple combinations of loads and boundary conditions. As defined in NB-3682, stress indices are determined by B, C = σ/S where σ is elastic stress in the component and S is the nominal stress in the component. The B2 indices were calculated by two methods: method one which is the default solution in FEA program, all six stress components were applied to calculate the membrane plus bending stress; method two, axial and hoop normal stress components and torsional shear stress components were used to get the membrane plus bending stress. The results show that the method two for B2 indices are more reasonable and realistic. For C2 indices method one was determined to be more appropriate. This paper presents the results of the analysis, the basis for stress indices development and the resulting stress indices.

scholarly journals Design and Characterization of Microscale Auxetic and Anisotropic Structures Fabricated by Multiphoton Lithography

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 446
Author(s):  
Ioannis Spanos ◽  
Zacharias Vangelatos ◽  
Costas Grigoropoulos ◽  
Maria Farsari
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Mechanical Performance ◽  
Element Analysis ◽  
Mechanical Responses ◽  
Multiphoton Lithography ◽  
Anisotropic Structures ◽  
Scanning Electron

The need for control of the elastic properties of architected materials has been accentuated due to the advances in modelling and characterization. Among the plethora of unconventional mechanical responses, controlled anisotropy and auxeticity have been promulgated as a new avenue in bioengineering applications. This paper aims to delineate the mechanical performance of characteristic auxetic and anisotropic designs fabricated by multiphoton lithography. Through finite element analysis the distinct responses of representative topologies are conveyed. In addition, nanoindentation experiments observed in-situ through scanning electron microscopy enable the validation of the modeling and the observation of the anisotropic or auxetic phenomena. Our results herald how these categories of architected materials can be investigated at the microscale.

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