Numerical Modeling and Analytical Investigation of Autofrettage Process on the Fluid End Module of Fracture Pumps

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Mahdi Kiani ◽  
Roger Walker ◽  
Saman Babaeidarabad
Keyword(s):  
Residual Stresses ◽  
Kinematic Hardening ◽  
Analytical Formula ◽  
Strain Analysis ◽  
Material Model ◽  
Analytical Investigation ◽  
Stress Strain ◽  
Element Analysis ◽  
Hardening Material ◽  
Strain Evolution

One of the most important components in the hydraulic fracturing is a type of positive-displacement-reciprocating-pumps known as a fracture pump. The fluid end module of the pump is prone to failure due to unconventional drilling impacts of the fracking. The basis of the fluid end module can be attributed to cross bores. Stress concentration locations appear at the bores intersections and as a result of cyclic pressures failures occur. Autofrettage is one of the common technologies to enhance the fatigue resistance of the fluid end module through imposing the compressive residual stresses. However, evaluating the stress–strain evolution during the autofrettage and approximating the residual stresses are vital factors. Fluid end module geometry is complex and there is no straightforward analytical solution for prediction of the residual stresses induced by autofrettage. Finite element analysis (FEA) can be applied to simulate the autofrettage and investigate the stress–strain evolution and residual stress fields. Therefore, a nonlinear kinematic hardening material model was developed and calibrated to simulate the autofrettage process on a typical commercial triplex fluid end module. Moreover, the results were compared to a linear kinematic hardening model and a 6–12% difference between two models was observed for compressive residual hoop stress at different cross bore corners. However, implementing nonlinear FEA for solving the complicated problems is computationally expensive and time-consuming. Thus, the comparison between nonlinear FEA and a proposed analytical formula based on the notch strain analysis for a cross bore was performed and the accuracy of the analytical model was evaluated.

Critical Buckling Strain in High Strength Steel Pipes Using Isotropic-Kinematic Hardening

2010 ◽  
Author(s):  
A. Fathi ◽  
J. J. Roger Cheng ◽  
Samer Adeeb ◽  
Joe Zhou
Keyword(s):  
Kinematic Hardening ◽  
High Strength ◽  
Material Model ◽  
Test Results ◽  
Stress Strain ◽  
Hardening Material ◽  
Anisotropic Models ◽  
Steel Pipes ◽  
Strain Data ◽  
Critical Buckling Strain

High strength steel pipes (HSSP) have become more popular recently for highly pressurized pipelines built to transport natural gas from remote fields to energy markets. Material tests on HSSP showed significant material anisotropy caused by the pipe making process, UOE. A combined isotropic-kinematic hardening material model is developed based on observations made on longitudinal and transverse stress strain data of HSSP. This material model combines linear isotropic hardening with Armstrong-Fredrick kinematic hardening and can be easily calibrated by longitudinal and transverse tension coupon test results. The proposed material model is used to show how considering material anisotropy affects the critical buckling strain of HSSP in the longitudinal direction. Finite element (FE) models are developed to simulate one pressurized and one unpressurised HSSP tested under monotonic displacement-controlled bending. Isotropic and anisotropic material modeling methods are used for each HSSP models. In the isotropic material model, longitudinal stress-strain data of HSSP material is used to define the stress-strain relationship. In the anisotropic model combined hardening material model, calibrated by longitudinal and transverse HSSP stress-strain data, is used. Critical buckling strain predictions by isotropic and anisotropic models of these pipes are compared with test results and also with some available criteria in standards and literatures. These comparisons show that anisotropic models give predictions closer to test results.

Intensive Validation of Computer Prediction of Welding Residual Stresses in a Multi-Pass Butt Weld

2010 ◽  
Author(s):  
Weijing He ◽  
Liwu Wei ◽  
Simon Smith
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Kinematic Hardening ◽  
Cost Effective ◽  
Material Model ◽  
Element Analysis ◽  
Computer Prediction ◽  
Butt Weld ◽  
Very High

Welding and joining technology is fundamental to offshore engineering. The construction of engineering facilities and pipelines requires the extensive use of welding and associated structural integrity assessments of safety critical or heavily loaded sections. Proof of integrity is based upon the externally applied loads and in service stresses as well as the welding residual stresses. The level and distribution of residual stresses arises from the complex thermo-mechanical history of heat flow and thermal expansion at very high temperatures during welding, so it has not been possible to make very accurate assessments of these in the same way that service stresses can be defined. Conservative assumptions are therefore made and this often means that the as-welded stresses are assumed to be of yield magnitude. The peak values of stress may well be very high, but the shrinkage of the latter passes of multi-pass welds may compress earlier passes giving rise to much lower levels of stress. There is considerable engineering interest in the utilisation of lower levels of residual stress where they exist or of the design of welds with lower residual stresses in sensitive areas such as the weld root. Currently there is no single technique that can claim to provide cost effective, accurate distributions of residual stresses in welds. The current paper provides an important contribution to the understanding of measurement and prediction techniques. It describes an extensive set of measurements taken on a girth butt weld. The weld was made using submerged arc and was made in 18 passes. The pipe was X52 with a 32mm wall thickness and 910mm outside diameter. Temperature, strain and displacement values were measured throughout the production of the weld. The intermediate values between each pass were recorded as well as the time varying history during the production of individual passes. The final through thickness residual stress distribution was measured. Finite Element Analysis (FEA) modelling was undertaken to determine whether modelling could provide a satisfactory prediction of the final residual stresses. Intermediate results were also used to understand the behaviour of the weld and the model more clearly. The modelling used material properties measured on material from a separate specimen. The weld cross section was identified for each pass so that the heat input method could be developed to represent the actual melt pool conditions of the weld. The measured values of hoop residual stress were up to the yield stress magnitude just below the cap, but were 20% of yield in the root of the weld. The axial residual stresses were less than 50% of yield. Linear kinematic hardening provided the most accurate prediction of residual stress. The hoop stresses were predicted to an accuracy of 10% with this material model. Other hardening models were less accurate, but all models were conservative. The results provide a basis for the adoption of more accurate distributions of residual stresses in Engineering Critical Assessments (ECAs) and assessments of weld performance under fatigue and corrosive conditions.

Computational Investigation of Composite Repair Materials Preventive Effects on Wrinkle Bends Fatigue Failure

2017 ◽  
Author(s):  
Mahdi Kiani ◽  
Timothy Mally ◽  
Roger Walker ◽  
Eric Locke
Keyword(s):  
Fatigue Life ◽  
Internal Pressure ◽  
Kinematic Hardening ◽  
Experimental Tests ◽  
Material Model ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Hardening Material ◽  
Composite Repair ◽  
Repair Materials

Wrinkle bending was a vintage technique in pipeline construction for aligning pipe sections. However, this process causes severe geometry changes over the pipeline structure and thus stress concentrations are developed. These stress concentrations have the potential to cause catastrophic pipeline failure due to internal pressure cycles, seismic effects and temperature changes. Different techniques have been studied and examined to mitigate the destructive effects that wrinkle bends pose to pipeline integrity. Composite repair methods and materials have been proven as one of the most reliable and efficient technologies to repair different pipeline defects. Designing an economical composite repair for a wrinkled pipe with proper performance requires precise design considerations. Finding an economical balance can be achieved multiple ways, such as performing experimental tests or applying analytical formulas and procedures. Each of these two methods has its own drawbacks: cost, errors and time can prevent accurate experimental tests and poor accuracy. Applicability of suggested analytical design equations can render certain analyses useless. To technically and economically improve the design and application processes of composite repair systems for wrinkle bends, elastic finite element analysis (FEA) was performed. The FEA analysis was conducted to study the effects of applying composite repairs on the elastic stress concentration factor of the wrinkle section of a Grade X52 carbon steel pipe. Moreover, a nonlinear kinematic hardening material model was developed and calibrated for this same steel. An elastic-plastic FEA was implemented to evaluate the stress-strain response of a wrinkled pipe subjected to a cyclic bending loading and constant internal pressure. Different strain based fatigue life estimation approaches were used to estimate the fatigue life enhancement achieved by utilizing a proprietary composite repair installation method.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

Cord/Rubber Material Properties

1985 ◽  
Vol 58 (4) ◽  
pp. 830-856 ◽  
Author(s):  
R. J. Cembrola ◽  
T. J. Dudek
Keyword(s):  
Finite Element ◽  
Material Model ◽  
Rubber Composites ◽  
Stress Strain ◽  
Element Analysis ◽  
Rubber Layer ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Interlaminar Shear ◽  
Mechanics Of Composite Materials

Abstract Recent developments in nonlinear finite element methods (FEM) and mechanics of composite materials have made it possible to handle complex tire mechanics problems involving large deformations and moderate strains. The development of an accurate material model for cord/rubber composites is a necessary requirement for the application of these powerful finite element programs to practical problems but involves numerous complexities. Difficulties associated with the application of classical lamination theory to cord/rubber composites were reviewed. The complexity of the material characterization of cord/rubber composites by experimental means was also discussed. This complexity arises from the highly anisotropic properties of twisted cords and the nonlinear stress—strain behavior of the laminates. Micromechanics theories, which have been successfully applied to hard composites (i.e., graphite—epoxy) have been shown to be inadequate in predicting some of the properties of the calendered fabric ply material from the properties of the cord and rubber. Finite element models which include an interply rubber layer to account for the interlaminar shear have been shown to give a better representation of cord/rubber laminate behavior in tension and bending. The application of finite element analysis to more refined models of complex structures like tires, however, requires the development of a more realistic material model which would account for the nonlinear stress—strain properties of cord/rubber composites.

Effect of Residual Stress or Plastic Deformation History on Fatigue Life Simulation of Pipeline Dents

2018 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Rick Wang
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Strain History ◽  
Deformation History ◽  
Stress Strain ◽  
Element Analysis ◽  
Fea Model

Mechanical dents often occur in transmission pipelines, and are recognized as one of major threats to pipeline integrity because of the potential fatigue failure due to cyclic pressures. With matured in-line-inspection (ILI) technology, mechanical dents can be identified from the ILI runs. Based on ILI measured dent profiles, finite element analysis (FEA) is commonly used to simulate stresses and strains in a dent, and to predict fatigue life of the dented pipeline. However, the dent profile defined by ILI data is a purely geometric shape without residual stresses nor plastic deformation history, and is different from its actual dent that contains residual stresses/strains due to dent creation and re-rounding. As a result, the FEA results of an ILI dent may not represent those of the actual dent, and may lead to inaccurate or incorrect results. To investigate the effect of residual stress or plastic deformation history on mechanics responses and fatigue life of an actual dent, three dent models are considered in this paper: (a) a true dent with residual stresses and dent formation history, (b) a purely geometric dent having the true dent profile with all stress/strain history removed from it, and (c) a purely geometric dent having an ILI defined dent profile with all stress/strain history removed from it. Using a three-dimensional FEA model, those three dents are simulated in the elastic-plastic conditions. The FEA results showed that the two geometric dents determine significantly different stresses and strains in comparison to those in the true dent, and overpredict the fatigue life or burst pressure of the true dent. On this basis, suggestions are made on how to use the ILI data to predict the dent fatigue life.

scholarly journals Validation of Welding Simulations Using Thermal Strains Measured with DIC

2011 ◽  
Vol 70 ◽  
pp. 129-134 ◽  
Author(s):  
Maarten De Strycker ◽  
Pascal Lava ◽  
Wim Van Paepegem ◽  
Luc Schueremans ◽  
Dimitri Debruyne
Keyword(s):  
Residual Stresses ◽  
Cross Section ◽  
Circular Cross Section ◽  
Welding Process ◽  
Weld Bead ◽  
Image Correlation ◽  
Steel Tubes ◽  
Element Analysis ◽  
Strain Evolution ◽  
The Cross

Residual stresses can affect the performance of steel tubes in many ways and as a result their magnitude and distribution is of particular interest to many applications. Residual stresses in cold-rolled steel tubes mainly originate from the rolling of a flat plate into a circular cross section (involving plastic deformations) and the weld bead that closes the cross section (involving non-uniform heating and cooling). Focus in this contribution is on the longitudinal weld bead that closes the cross section. To reveal the residual stresses in the tubes under consideration, a finite element analysis (FEA) of the welding step in the production process is made. The FEA of the welding process is validated with the temperature evolution of the thermal simulation and the strain evolution for the mechanical part of the analysis. Several methods for measuring the strain evolution are available and in this contribution it is investigated if the Digital Image Correlation (DIC) technique can record the strain evolution during welding. It is shown that the strain evolution obtained with DIC is in agreement with that found by electrical resistance strain gauges. The results of these experimental measuring methods are compared with numerical results from a FEA of the welding process.

Hyperelastic Muscle Simulation

2007 ◽  
Vol 345-346 ◽  
pp. 1241-1244 ◽  
Author(s):  
Mohd. Zahid Ansari ◽  
Sang Kyo Lee ◽  
Chong Du Cho
Keyword(s):  
Skeletal Muscle ◽  
Silicone Rubber ◽  
Soft Tissues ◽  
Material Model ◽  
Incompressible Material ◽  
Material Behavior ◽  
Rubber Tube ◽  
Stress Strain ◽  
Element Analysis ◽  
Strain Behavior

Biological soft tissues like muscles and cartilages are anisotropic, inhomogeneous, and nearly incompressible. The incompressible material behavior may lead to some difficulties in numerical simulation, such as volumetric locking and solution divergence. Mixed u-P formulations can be used to overcome incompressible material problems. The hyperelastic materials can be used to describe the biological skeletal muscle behavior. In this study, experiments are conducted to obtain the stress-strain behavior of a solid silicone rubber tube. It is used to emulate the skeletal muscle tensile behavior. The stress-strain behavior of silicone is compared with that of muscles. A commercial finite element analysis package ABAQUS is used to simulate the stress-strain behavior of silicone rubber. Results show that mixed u-P formulations with hyperelastic material model can be used to successfully simulate the muscle material behavior. Such an analysis can be used to simulate and analyze other soft tissues that show similar behavior.

scholarly journals A Simplified Method for Elastic-Plastic-Creep Structural Analysis

1985 ◽  
Vol 107 (1) ◽  
pp. 231-237 ◽  
Author(s):  
A. Kaufman
Keyword(s):  
Finite Element ◽  
Stress Relaxation ◽  
Kinematic Hardening ◽  
Nonlinear Finite Element ◽  
Strain History ◽  
Stress Strain ◽  
Element Analysis ◽  
Inelastic Analysis ◽  
Simplified Method ◽  
Time Required

A simplified inelastic analysis computer program (ANSYMP) was developed for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects can be calculated on the basis of stress relaxation at constant strain, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials, and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.

Method and Verification for Material Calibration of the Chaboche Plasticity Model for Multiple Material Directions

2021 ◽  
Author(s):  
Charles R. Krouse ◽  
Grant O. Musgrove ◽  
Taewoan Kim ◽  
Seungmin Lee ◽  
Muhyoung Lee ◽  
...  
Keyword(s):  
Experimental Data ◽  
Kinematic Hardening ◽  
Material Model ◽  
Brute Force ◽  
Hardening Material ◽  
Material Constants ◽  
Automated Method ◽  
Chaboche Model ◽  
Multiple Material ◽  
Brute Force Approach

Abstract The Chaboche model is a well-validated non-linear kinematic hardening material model. This material model, like many models, depends on a set of material constants that must be calibrated for it to match the experimental data. Due to the challenge of calibrating these constants, the Chaboche model is often disregarded. The challenge with calibrating the Chaboche constants is that the most reliable method for doing the calibration is a brute force approach, which tests thousands of combinations of constants. Different sampling techniques and optimization schemes can be used to select different combinations of these constants, but ultimately, they all rely on iteratively selecting values and running simulations for each selected set. In the experience of the authors, such brute force methods require roughly 2,500 combinations to be evaluated in order to have confidence that a reasonable solution is found. This process is not efficient. It is time-intensive and labor-intensive. It requires long simulation times, and it requires significant effort to develop the accompanying scripts and algorithms that are used to iterate through combinations of constants and to calculate agreement. A better, more automated method exists for calibrating the Chaboche material constants. In this paper, the authors describe a more efficient, automated method for calibrating Chaboche constants. The method is validated by using it to calibrate Chaboche constants for an IN792 single-crystal material and a CM247 directionally-solidified material. The calibration results using the automated approach were compared to calibration results obtained using a brute force approach. It was determined that the automated method achieves agreeable results that are equivalent to, or supersede, results obtained using the conventional brute force method. After validating the method for cases that only consider a single material orientation, the automated method was extended to multiple off-axis calibrations. The Chaboche model that is available in commercial software, such as ANSYS, will only accept a single set of Chaboche constants for a given temperature. There is no published method for calibrating Chaboche constants that considers multiple material orientations. Therefore, the approach outlined in this paper was extended to include multiple material orientations in a single calibration scheme. The authors concluded that the automated approach can be used to successfully, accurately, and efficiently calibrate multiple material directions. The approach is especially well-suited when off-axis calibration must be considered concomitantly with longitudinal calibration. Overall, the automated Chaboche calibration method yielded results that agreed well with experimental data. Thus, the method can be used with confidence to efficiently and accurately calibrate the Chaboche non-linear kinematic hardening material model.

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