Creep Simulation of the Hydroprocessing Reactor Using a Physically-Based CDM Model

2015 ◽  
Author(s):  
Yu Zhou ◽  
Chen Xuedong ◽  
Fan Zhichao ◽  
Jie Dong
Keyword(s):  
Damage Mechanics ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Three Dimensional ◽  
Critical Issue ◽  
Fe Modelling ◽  
Creep Failure ◽  
Good Tool ◽  
Element Analysis ◽  
Physically Based

Creep failure is one of the most important failure modes in the design of hydroprocessing reactors at elevated temperatures, and the accurate prediction of the creep behavior in structural discontinuities is a critical issue for component design. A physically-based continnum damage mechanics (CDM) model was adopted to describe all three creep stages of 2.25Cr-1Mo-0.25V ferritic steel widely used in manufacturing modern hydroprocessing reactors. The material constants in the damage constitutive equations were identified using an efficient optimization scheme based on genetic algorithm (GA). The user-defined subroutine implementing the CDM model was developed using user programmable features (UPFs) in ANSYS. Three-dimensional finite element analysis of the hydroprocessing reactor was conducted to determine the critical regions, and the studies on the stress redistribution and the prediction of damage evolution in these regions during creep were carried out. The results show that FE modelling based on CDM theory can provide a good tool for creep design of complex engineering components.

Progressive failure analysis of scarf-repaired composite laminate based on damage constitutive model

2016 ◽  
Vol 233 (2) ◽  
pp. 180-188 ◽  
Author(s):  
Qiuyi Shen ◽  
Zhenghao Zhu ◽  
Yi Liu
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Composite Laminate ◽  
Damage Mechanics ◽  
Cohesive Zone Model ◽  
Load Capacity ◽  
Three Dimensional ◽  
Zone Model ◽  
State Variables ◽  
Element Analysis

A three-dimensional finite element model for scarf-repaired composite laminate was established on continuum damage model to predict the load capacity under tensile loading. The mixed-mode cohesive zone model was adopted to the debonding behavior analysis of adhesive. Damage condition and failure of laminates and adhesive were subsequently addressed. A three-dimensional bilinear constitutive model was developed for composite materials based on damage mechanics and applied to damage evolution and loading capacity analyses by quantifying damage level through damage state variables. The numerical analyses were implemented with ABAQUS finite element analysis by coding the constitutive model into material subroutine VUMAT. Good agreement between the numerical and experimental results shows the accuracy and adaptability of the model.

Finite Element Analysis of Local Inelastic Strain Based on Stress Redistribution Locus

2008 ◽  
Author(s):  
Shunji Kataoka ◽  
Takuya Sato
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Loading ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Pressure Vessels ◽  
Stress Redistribution ◽  
Strain Diagram ◽  
Element Analysis ◽  
Inelastic Analysis

Creep-fatigue damage is one of the dominant failure modes for pressure vessels and piping used at elevated temperatures. In the design of these components the inelastic behavior should be estimated accurately. An inelastic finite element analysis is sometimes employed to predict the creep behavior. However, this analysis needs complicated procedures and many data that depend on the material. Therefore the design is often based on a simplified inelastic analysis based on the elastic analysis result, as described in current design codes. A new, simplified method, named, Stress Redistribution Locus (SRL) method, was proposed in order to simplify the analysis procedure and obtain reasonable results. This method utilizes a unique estimation curve in a normalized stress-strain diagram which can be drawn regardless of the magnitude of thermal loading and constitutive equations of the materials. However, the mechanism of SRL has not been fully investigated. This paper presents results of the parametric inelastic finite element analyses performed in order to investigate the mechanism of SRL around a structural discontinuity, like a shell-skirt intersection, subjected to combined secondary bending stress and peak stress. This investigation showed that SRL comprises a redistribution of the peak and secondary stress components and that although these two components exhibit independent redistribution behavior, they are related to each other.

Substrate Damage Modeling for Advanced Turbine System Airfoils

2009 ◽  
Author(s):  
Ventzislav G. Karaivanov ◽  
Sean Siw ◽  
Minking K. Chyu ◽  
William S. Slaughter ◽  
Mary Anne Alvin
Keyword(s):  
Fatigue Damage ◽  
Damage Mechanics ◽  
Three Dimensional ◽  
Department Of Energy ◽  
Internal Cooling ◽  
Element Analysis ◽  
Service Operation ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Damage Simulation

The Department of Energy (DOE) is developing advanced hydrogen-fired and oxy-fueled turbine technologies that are projected to operate with turbine inlet temperatures (TIT) of 1425°C and 1760°C, respectively. At these temperatures, the airfoil will require not only internal cooling, but also stable thermal barrier coatings (TBCs) in order to achieve extended service operation in these advanced high steam-containing environments. We previously developed a computational methodology, based on three-dimensional finite element analysis (FEA) and damage mechanics, for predicting the evolution of creep in the hydrogen-fired and oxy-fueled airfoils. This methodology has been extended to fatigue damage evolution. Currently, the model allows for the interaction between creep and fatigue damage. Simulation results will be presented that visualize creep and fatigue damage for hydrogen-fired and oxy-fuel airfoils. Additionally, the influence of dynamic changes in the TBC microstructure and phase composition with operational time will be discussed relative to all projected damage mechanisms.

Post-Buckling Behavior of Z-Shaped Columns under Variables of Lengths and Initial Imperfections

2013 ◽  
Vol 437 ◽  
pp. 62-65
Author(s):  
Ji Nao Zhang
Keyword(s):  
Failure Modes ◽  
Control Method ◽  
Three Dimensional ◽  
Initial Imperfection ◽  
Maximum Load ◽  
Element Analysis ◽  
Initial Imperfections ◽  
Solution Methods ◽  
Post Buckling ◽  
Displacement Control Method

This paper conducts three-dimensional, nonlinear finite element analysis to investigate the results of using different solution methods and the influence of initial imperfections and material plasticity on failure modes and maximum load of various Z-shaped column lengths; it also compares the column buckling responses between various lengths, each with different initial imperfections. Further analyses include investigating the element suitability and computational costs. Results showed that both displacement control method and Riks method are fully capable of receiving promising results from this analysis. In terms of the effects of initial imperfection and material plasticity on the maximum load that column could carry, the imperfection is the major contributing factor when the column is long whereas the plasticity is the major contributing factor when the column is short.

Building Three-Dimensional Merged Surface Model from Polygonal Models

2012 ◽  
Vol 566 ◽  
pp. 336-341
Author(s):  
Jian Jun Du ◽  
Xin Yu Guo ◽  
Sheng Lian Lu ◽  
Bo Xiang Xiao ◽  
Jian Wei Wu
Keyword(s):  
Three Dimensional ◽  
Surface Model ◽  
Element Analysis ◽  
Detection Techniques ◽  
Physically Based ◽  
Intersection Line ◽  
Searching Method ◽  
Water Proof ◽  
Merging Method ◽  
Polygonal Models

Three-dimensional surface merging plays an important role in rapid prototyping manufacture, physically based modeling and finite element analysis. In this paper, a rapid merging method is proposed to build three-dimensional water-proof surface model from polygonal models. To rapidly determine merging boundaries, collision detection techniques are used to obtain the intersection triangle pairs between the two input models, and then the intersection line loops are accurately computed. Furthermore, triangle tessellation and edge searching method is used to generate new triangles and classify each triangle in models into different triangle sets. Finally, an inclusion test determines the position of each triangle set and stitches the labeled triangle sets into the merged model. The experimental results demonstrate the robustness and adaptability of the presented method.

Three-Dimensional Modeling of Creep Damage in Airfoils for Advanced Turbine Systems

2008 ◽  
Author(s):  
Ventzislav G. Karaivanov ◽  
Danny W. Mazzotta ◽  
Minking K. Chyu ◽  
William S. Slaughter ◽  
Mary Anne Alvin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Gas Turbines ◽  
Damage Mechanics ◽  
Thermal Loading ◽  
Three Dimensional ◽  
Creep Damage ◽  
Creep Model ◽  
Working Fluid ◽  
Element Analysis

Future oxy-fuel and hydrogen-fired turbines promise increased efficiency and low emissions. However, this comes at the expense of increased thermal load from higher inlet temperatures and a change in the working fluid in the gas path, leading to aero-thermal characteristics that are significantly different than those in traditional gas turbines. A computational methodology, based on three-dimensional finite element analysis (FEA) and damage mechanics is presented for predicting the evolution of creep in airfoils in these advanced turbine systems. Information revealed from three-dimensional computational fluid dynamics (CFD) simulations of external heat transfer and thermal loading over a generic airfoil provides detailed local distributions of pressure, surface temperature, and heat flux penetrating through the thermal barrier coated layer. There is an additional mechanical loading due to the centrifugal acceleration of the airfoil. Finite element analysis is then used to predict temperature and stress fields over the domain of the airfoil. The damage mechanics-based creep model uses a scalar damage parameter. This creep model is coupled with finite element analysis to predict the evolution of stress and creep damage over the entire airfoil. Visualization of the creep damage evolution over the airfoil shows the regions that are most susceptible to failure by creep.

Evaluation of the Effects of Inclusion Distribution on the Local Ductility of DP Steel

2012 ◽  
Vol 706-709 ◽  
pp. 1527-1532 ◽  
Author(s):  
Y. Suwa ◽  
T. Matsuno ◽  
S. Hirose ◽  
N. Fujita ◽  
A. Seto
Keyword(s):  
Finite Element ◽  
Damage Mechanics ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Element Analysis ◽  
Dp Steel ◽  
The Difference ◽  
Inclusion Distribution

In the present study, the effects of inclusions on the local ductility of DP steel are investigated using finite element analysis (FEA). In order to evaluate local ductility, a continuum damage mechanics (CDM) model has been incorporated into the Abaqus/Explicit® commercial finite element code. Furthermore, three-dimensional representative volume elements (RVEs) with ferrite, martensite, and inclusion phases have been used to evaluate the stress-strain response. Simulation results show that the volume fraction of the martensite as well as the difference in hardness between the ferrite and the martensite phases dominates the effect of inclusions on local ductility.

Behaviour of concrete block masonry prisms under axial compression

1995 ◽  
Vol 22 (5) ◽  
pp. 898-915 ◽  
Author(s):  
E. H. Fahmy ◽  
T. G. M. Ghoneim
Keyword(s):  
Finite Element ◽  
Axial Compression ◽  
Modulus Of Elasticity ◽  
Failure Modes ◽  
Three Dimensional ◽  
Concrete Block ◽  
Element Model ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

A nonlinear three-dimensional finite element model was developed to study the complex behavior of ungrouted and grouted concrete block masonry prisms under axial compression. The model detects crack initiation and traces crack propagation in the masonry assemblage. Variable strengths for blocks, mortar, and grout were used to study the effect of the mechanical properties of prism constituents, and their combinations, on the prism strength and modulus of elasticity. The effect of the number of courses was also investigated. The results of the finite element analysis were used to develop simplified relationships to predict prism strength and modulus of elasticity. Good agreement was observed between the available experimental data and the predicted prism strengths. Key words: compressive strength, concrete blocks, failure modes, finite element, masonry, modulus of elasticity, prisms.

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