Long and Short Radius Elbow Experiments and Evaluation of Advanced Constitutive Models to Simulate the Responses

2015 ◽  
Author(s):  
Nazrul Islam ◽  
Matthew Fenton ◽  
Tasnim Hassan
Keyword(s):  
Finite Element ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Constitutive Models ◽  
Image Correlation ◽  
Cycle Fatigue ◽  
Element Simulation ◽  
Piping Systems ◽  
Diameter Change ◽  
Dic Technique

Low-cycle fatigue (LCF) and strain ratcheting responses of long and short radius elbows are studied experimentally and analytically. Elbow piping components are widely used in piping systems, however, the prediction of their low-cycle fatigue and ratcheting responses remain a challenge. Hence, a systematic set of short and long radius elbow LCF responses are developed by prescribing displacement-controlled loading cycles with or without internal pressure. A setup comprised of four LVDTs was utilized to measure diameter change during cyclic loading. In order to evaluate the accuracy of the strain gage data, strains are also acquired using the digital image correlation (DIC) technique. Recorded fatigue responses are analyzed in understanding the differences in LCF lives between the long and short radius elbows. The Chaboche nonlinear kinematic hardening constitutive model in ANSYS and a modified version of this model are evaluated for their simulation capability against the recorded elbow responses. The experimental and finite element simulation responses are presented in this article.

Application of Noninteraction Constitutive Models for Deformation of IN617 Under Combined Extreme Environments

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Thomas Bouchenot ◽  
Calvin Cole ◽  
Ali P. Gordon ◽  
Casey Holycross ◽  
Ravi C. Penmetsa
Keyword(s):  
Finite Element ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Extreme Environments ◽  
Constitutive Models ◽  
Original Data ◽  
Industrial Sector ◽  
Cycle Fatigue ◽  
Simple Method ◽  
Finite Element Software

Next-generation, reusable hypersonic aircraft will be subjected to extreme environments that produce complex fatigue loads at high temperatures, reminiscent of the life-limiting thermal and mechanical loads present in large gas-powered land-based turbines. In both of these applications, there is a need for greater fidelity in the constitutive material models employed in finite element simulations, resulting in the transition to nonlinear formulations. One such formulation is the nonlinear kinematic hardening (NLKH) model, which is a plasticity model quickly gaining popularity in the industrial sector, and can be found in commercial finite element software. The drawback to using models like the NLKH model is that the parameterization can be difficult, and the numerical fitting techniques commonly used for such tasks may result in constants devoid of physical meaning. This study presents a simple method to derive these constants by extrapolation of a reduced-order model, where the cyclic Ramberg–Osgood (CRO) formulation is used to obtain the parameters of a three-part NLKH model. This fitting scheme is used with basic literature-based data to fully characterize a constitutive model for Inconel 617 at temperatures between 20 °C and 1000 °C. This model is validated for low-cycle fatigue (LCF), creep-fatigue (CF), thermomechanical fatigue (TMF), and combined thermomechanical-high-cycle fatigue (HCF) using a mix of literature data and original data produced at the Air Force Research Laboratory (AFRL).

Cyclic Deformation and Buckling Behavior of Pipe With Local Metal Loss Subjected to Seismic Ground Motion

2011 ◽  
Author(s):  
Masaki Mitsuya ◽  
Hiroshi Yatabe
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Cyclic Deformation ◽  
Deformation Behavior ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Earthquake Resistance ◽  
Metal Loss ◽  
Cycle Fatigue ◽  
Longitudinal Length

Buried pipelines may be deformed due to earthquakes and also corrode despite corrosion control measures such as protective coatings and cathodic protection. In such cases, it is necessary to ensure the integrity of the corroded pipelines against earthquakes. This study developed a method to evaluate the earthquake resistance of corroded pipelines subjected to seismic ground motions. Axial cyclic loading experiments were carried out on line pipes subjected to seismic motion to clarify the cyclic deformation behavior until buckling occurs. The test pipes were machined so that each one would have a different degree of local metal loss. As the cyclic loading progressed, displacement shifted to the compression side due to the formation of a bulge. The pipe buckled after several cycles. To evaluate the earthquake resistance of different pipelines, with varying degrees of local metal loss, a finite-element analysis method was developed that simulates the cyclic deformation behavior. A combination of kinematic and isotropic hardening components was used to model the material properties. These components were obtained from small specimen tests that consisted of a monotonic tensile test and a low cycle fatigue test under a specific strain amplitude. This method enabled the successful prediction of the cyclic deformation behavior, including the number of cycles required for the buckling of pipes with varying degrees of metal loss. In addition, the effect of each dimension (depth, longitudinal length and circumferential width) of local metal loss on the cyclic buckling was studied. Furthermore, the kinematic hardening component was investigated for the different materials by the low cycle fatigue tests. The kinematic hardening components could be regarded as the same for all the materials when using this component as the material property for the finite-element analyses simulating the cyclic deformation behavior. This indicates that the cyclic deformation behavior of various line pipes can be evaluated only based on their respective tensile properties and common kinematic hardening component.

Constitutive Models in Simulating Low-Cycle Fatigue and Ratcheting Responses of Elbow

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
T. Hassan ◽  
M. Rahman
Keyword(s):  
Damage Accumulation ◽  
Low Cycle Fatigue ◽  
Constitutive Models ◽  
Strain Accumulation ◽  
Cycle Fatigue ◽  
Force Response ◽  
Reasonable Accuracy ◽  
Experimental Trend ◽  
Strain Responses ◽  
Diameter Change

As stated in the sister article that the objective of this study was to explore the low-cycle fatigue and ratcheting failure responses of elbow components through experimental and analytical studies. Low-cycle fatigue and ratcheting damage accumulation in piping components may occur under load reversals induced by earthquakes or thermomechanical operations. Ratcheting damage accumulation can cause failure of components through cracking or plastic buckling. Hence, design by analysis of piping components against ratcheting failure will require simulation of this response with reasonable accuracy. In developing a constitutive model that can simulate ratcheting responses of piping components, a systematic set of elbow experiments involving deformation and strain ratcheting were conducted and reported in the sister article. This article will critically evaluate seven different constitutive models against their elbow response simulation capabilities. The widely used bilinear, multilinear, and Chaboche models in ansys are first evaluated. This is followed by evaluation of the modified Chaboche, Ohno–Wang, modified Ohno–Wang, and Abdel Karim–Ohno models. Results from this simulation study are presented to demonstrate that all the seven models can simulate the elbow force response reasonably. The bilinear and multilinear models can simulate the initial elbow diameter change or strain accumulation, but always simulate shakedown during the subsequent cycles when for some of the cases the experimental trends are ratcheting. Advanced constitutive models like Chaboche, modified Chaboche, Ohno–Wang, modified Ohno–Wang, and Abdel Karim–Ohno can simulate many of the elbow ratcheting responses well, but for some of the strain responses, these models simulate negative ratcheting, which is opposite to the experimental trend. Finally, implications of negative ratcheting simulation are discussed and suggestions are made for improving constitutive models ratcheting response simulation.

scholarly journals Finite Element Simulation of Multi-Axial Low Cycle Fatigue of Material SA333

2014 ◽  
Vol 86 ◽  
pp. 158-165
Author(s):  
J. De ◽  
S. Bhattacharjee ◽  
S. Dhar ◽  
S.K. Acharyya ◽  
S.K. Gupta ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Element Simulation

Low-Cycle Fatigue and Ratcheting Responses of Elbow Piping Components

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
T. Hassan ◽  
M. Rahman ◽  
S. Bari
Keyword(s):  
Constitutive Model ◽  
Internal Pressure ◽  
Damage Accumulation ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Constitutive Models ◽  
Code Design ◽  
Cycle Fatigue ◽  
Fatigue Damage Accumulation ◽  
Piping Systems

The objective of this study was to investigate low-cycle fatigue and ratcheting responses of elbows through experimental and analytical studies. Low-cycle fatigue and ratcheting damage accumulation in piping components may occur under repeated reversals of loading induced by earthquake and/or thermomechanical operation. Ratcheting and fatigue damage accumulation can cause failure of piping systems through fatigue cracks or plastic buckling. However, the ratcheting damage induced failures are yet to be understood clearly; consequently, ASME Code design provisions against ratcheting failure continue to be a controversial issue over the last two decades. A systematic set of piping component experimental responses involving ratcheting and a computational tool to simulate these responses will be essential to rationally address the issue. Development of a constitutive model for simulating component ratcheting responses remains to be a challenging problem. In order to develop an experimentally validated constitutive model, a set of elbow experiments was conducted. The loading prescribed in the experiments involved displacement-controlled or force-controlled in-plane cyclic bending with or without internal pressure. Force, displacement, internal pressure, elbow diameter change, and strains at four locations of the elbow specimens were recorded. This article presents and discusses the results from the experimental study. A sister article evaluates seven different constitutive models against simulating these elbow ratcheting and fatigue responses.

Ultra-Low-Cycle Fatigue Behavior of Full-Scale Straight Pipes Under Alternating Bending

2016 ◽  
Author(s):  
João C. R. Pereira ◽  
Jeroen Van Wittenberghe ◽  
Abílio Jesus ◽  
Philippe Thibaux ◽  
António A. Fernandes
Keyword(s):  
Finite Element ◽  
Large Scale ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Fatigue Behavior ◽  
Full Scale ◽  
Small Scale ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Practical Applications

Ultra or extreme low-cycle fatigue of steels has been deserving increasing interest by the researchers since it corresponds to a fatigue domain not fully understood nor explored. It has been recognized that fatigue damage under extreme loading conditions is representative of several practical applications (e.g. seismic actions, accidental loads) and pipelines are a type of components that could undergo such extreme loading conditions. In addition, concerning the pipelines, reeling could also contribute to significant plastic cycles. ULCF damage corresponds to a transition damage behavior between the LCF and monotonic ductile damage. Therefore studies on ULCF usually needs to cover those bounding damage processes. ULCF testing exploring large-scale specimens is rare. The aim of this paper is to investigate the ultra-low-cycle fatigue of large-scale straight pipes subjected to cyclic pure bending tests which were performed under the framework of the ULCF European/RFCS project. In detail, two steel grades used on pipelines manufacturing were investigated, namely the X60 and X65 piping steels, respectively with the following nominal diameters of 16” (w.t. 9.5 mm) and 8 5/8” (w.t. 5.59 mm). A specifically developed testing setup was used to perform the cyclic bending of the straight pipes, combined with internal pressure, until the pipes collapse. The failure was preceded by local plastic instability (buckling), motivating the concentration of cyclic plastic deformation leading to macroscopic crack initiation and propagation. In addition to the full-scale tests, the plain material was investigated under monotonic and ULCF conditions using both smooth and notched specimens. In order to assess the stress/strain fields in the straight pipes, finite element models of the straight pipes were developed and simulations were performed under the experimental displacement histories. Nonlinear plasticity models with kinematic hardening, inputted on finite element simulations, were calibrated by means of small-scale data. Moreover, the test data of small-scale tests was used on the identification of damage models constants (e.g. Coffin-Manson), which in turn were applied to simulate the failure cycles of the tested straight pipes. The ASME B&PVC VIII Div.2 procedures were also used to compute the failure cycles for the straight pipes to allow an assessment of these existing procedures.

Finite element simulation technique for evaluation of opening stresses under high plasticity

2021 ◽  
pp. 1-21
Author(s):  
Ans Al Rashid ◽  
Ramsha Imran ◽  
Zia Ullah Arif ◽  
Muhammad Yasir Khalid
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Finite Element Simulation ◽  
Crack Closure ◽  
Low Cycle Fatigue ◽  
Simulation Technique ◽  
Experimental Results ◽  
High Plasticity ◽  
Cycle Fatigue ◽  
Element Simulation

Abstract The crack closure phenomenon is important to study as it estimates the fatigue life of the components. It becomes even more complex under low cycle fatigue (LCF) since under LCF high amount of plasticity is induced within the material near notches or defects. As a result, the assumptions used by the linear elastic fracture mechanics (LEFM) approach become invalid. However, several experimental techniques are reported on the topic, the utilization of numerical tools can provide substantial cost and time-saving. In this study, the authors present a finite element simulation technique to evaluate the opening stress levels for two structural steels (25CrMo4 and 30NiCrMoV12) under low cycle fatigue conditions. The LCF experimental results were used to obtain kinematic hardening parameters through the Chaboche model. The finite element analysis (FEA) model was designed and validated, following the fatigue crack propagation simulation under high plasticity conditions using ABAQUS. Crack opening displacement vs. stress data was exported from ABAQUS, and 1.5% offset method was employed to define opening stress levels. Numerical simulation results were compared with the experimental results obtained earlier through the digital image correlation (DIC) technique. To conclude, FEA could be a valuable tool to predict crack closure phenomena and, ultimately, the fatigue life of components. However, analysis of opening stresses using crystal plasticity models or extended finite element method (XFEM) tools should be explored for a better approximation in future studies.

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