Numerical Investigation of Ductile Fracture in Pipelines Under Complex Loading Using a Phenomenological Damage Model

2021 ◽  
Author(s):  
Iago S. Santos ◽  
Diego F. B. Sarzosa
Keyword(s):  
Ductile Fracture ◽  
Mechanical Response ◽  
Numerical Study ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Numerical Procedure ◽  
Complex Loading ◽  
Experimental Tests ◽  
Compact Tension ◽  
Axial Tensile

Abstract This paper presents a numerical study on pipes ductile fracture mechanical response using a phenomenological computational damage model. The damage is controlled by an initiation criterion dependent on the stress triaxiality and the Lode angle parameter, and a post-initiation damage law to eliminate each finite element from the mesh. Experimental tests were carried out to calibrate the elastoplastic response, damage parameters and validate the FEM models. The tested geometries were round bars having smooth and notched cross-section, flat notched specimens under axial tensile loads, and fracture toughness tests in deeply cracked bending specimens SE(B) and compact tension samples C(T). The calibrated numerical procedure was applied to execute a parametric study in pipes with circumferential surface cracks subjected to tensile and internal pressure loads simultaneously. The effects of the variation of geometric parameters and the load applications on the pipes strain capacity were investigated. The influence of longitudinal misalignment between adjacent pipes was also investigated.

Experimental and Numerical Study of Ductile Fracture Initiation in Aluminum 6061-T6

2015 ◽  
Author(s):  
W. Rekik ◽  
O. Ancelet ◽  
C. Gardin
Keyword(s):  
Numerical Simulation ◽  
Ductile Fracture ◽  
Void Growth ◽  
Numerical Study ◽  
Micromechanical Model ◽  
Stress Triaxiality ◽  
Fracture Initiation ◽  
Compact Tension ◽  
Growth Ratio ◽  
Ductile Fracture Initiation

This work deals with the characterization of ductile damage in Aluminum 6061-T6 alloy. In this paper we discuss the stress triaxiality effect on the initiation and the evolution of damage through a sequence of tensile tests conducted on round specimens with different rate of trixialities and tearing tests on precracked Compact Tension specimens. Scattering of ductility and toughness values was highlighted between the three characteristic directions studied in this topic. Based on the experimental results, numerical simulation has been performed in order to analyze and predict ductile fracture initiation of this aluminum alloy by simulating void growth according to the Rice-Tracey micromechanical model. The numerical simulation was conducted in two steps: first the critical void growth ratio (R / R0)c was evaluated for tensile cylindrical specimens with different degrees of triaxiality and then used to analyze crack growth initiation on Compact Tension specimen. Due to the Al-6061-T6 highly sensitivity to triaxiality, a necessary adaptation of the Rice-Tracey model’s coefficient was made.

Failure Limit State Investigation of Misaligned Welded Plates by Using a Damage Model-Based Upon Triaxiality and Lode Parameters

2020 ◽  
Author(s):  
Iago S. Santos ◽  
Diego F. B. Sarzosa
Keyword(s):  
Numerical Study ◽  
Limit State ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Failure Behavior ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Strain Capacity ◽  
Combined Loads ◽  
Welded Structure

Abstract This paper presents a numerical study using the finite element method to assess the structural integrity of welded plates. Different levels of weld misalignment were introduced on the FEM models to investigate the influence of this welding imperfection parameter on the limit state of the structure. The models were loaded under displacement-controlled condition to introduce traction and torsion loads seeking to understand the effects of combined loads on the strain capacity of the misaligned welded structure. Surface elliptical cracks having different crack-size ratios were modeled to study the crack growth behavior by taking into account the misalignment of the weld and combined loads. The damage model is based on a failure surface and post-initiation behavior to model the ductile crack initiation and propagation steps, respectively. The models provide useful information to track the evolution of damage on the hot spot point of the welded structure. The model used is dependent on stress triaxiality and a Lode-based parameter and the damage level is driven by the plastic strain. The evolution of stress triaxiality and Lode parameter with loading are presented, and the influence of misalignment on them are shown. An exponential softening law was adopted to predict post-initiation failure behavior. The calibration steps of the parameters required for damage model application are shown for a A285 pressure vessel steel. Overall, the numerical models reveal the deleterious effects of weld misalignment and combined torsional and tensile loads on the strain capacity of the weld.

Estimation of Ballistic Limit Velocities for Woven Composite Beams

2009 ◽  
Author(s):  
E. Sevkat ◽  
B. M. Liaw ◽  
F. Delale ◽  
B. B. Raju
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Damage Model ◽  
Experimental Tests ◽  
Composite Beams ◽  
Ballistic Limit ◽  
Gas Gun ◽  
Graphite Fibers ◽  
Ballistic Limit Velocity ◽  
Good Agreement

This paper presents an experimental and numerical study to estimate ballistic limit velocity, V50, of plain-weave hybrid S2 glass-IM7 graphite fibers/toughened SC-79 resin (cured at 177°C) composite beams. The tests were conducted on hybrid S2 glass-IM7 graphite fibers/toughened SC-79 resin and nonhybrid S2 glass-fiber/toughened SC-79 resin composites beams using high-speed gas-gun. The ballistic impact tests were then modeled using 3-D dynamic nonlinear finite element (FE) code, LS-DYNA, modified with a proposed user-defined nonlinear-orthotropic damage model. The ballistic limit velocities, V50, for both composite beams were then estimated using (a) only experimental tests, (b) combined experimental and numerical tests, (c) FE calculated residual velocities, and (d) FE calculated residual and transferred energies. For each type of composite beams, the parameters for the well-known Lambert-Jones equation were also computed. Good agreement between experimental and numerical results was observed.

scholarly journals Comparison of MMC and BW fracture models for constructing 3D ductile fracture envelope of AA6063 during cold forming

2020 ◽  
Author(s):  
Jianye Gao ◽  
Tao He ◽  
Yuanming Huo ◽  
Miao Song ◽  
Tingting Yao ◽  
...  
Keyword(s):  
Ductile Fracture ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Compression Tests ◽  
Cold Forming ◽  
Tension Tests ◽  
Wide Range ◽  
Round Bar ◽  
Fracture Models ◽  
Fracture Envelope

Abstract The 3D ductile fracture envelopes of AA6063-T6 was developed to predict and prevent its fracture. Smooth round bar (SRB) tension tests were carried out to characterize the flow stress, and a series of experiments were conducted to characterize the ductile fracture firstly, such as notched round bar (NR) tension tests, compression tests and torsion tests. These tests cover a wide range of stress triaxiality (ST) and Lode parameter (LP) to calibrate the ductile fracture criterion. Plasticity modeling was performed, and the predicted results were compared with corresponding experimental data to verify the plasticity model after these experiments. Then the relationship between ductile fracture strain and ST with LP was constructed using the modified Mohr–Coulomb (MMC) model and Bai and Wierzbicki (BW) model to develop the 3D ductile fracture envelope. Finally, a new ductile damage model was proposed based on the 3D fracture envelope of AA6063. The final results show that the predicted results from the proposed ductile fracture model showed good agreement with experimental results.

An Experimental and Numerical Study on the Axial Compression Response of Flexible Pipes

2010 ◽  
Author(s):  
Jose´ Renato M. de Sousa ◽  
Paula F. Viero ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Axial Compression ◽  
Failure Modes ◽  
Mechanical Response ◽  
Numerical Study ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Mechanical Analysis ◽  
Fe Model ◽  
Flexible Pipe ◽  
Flexible Pipes

This paper deals with a nonlinear three-dimensional finite element (FE) model capable of predicting the mechanical response of flexible pipes subjected to axisymmetric loads focusing on their axial compression response. Moreover, in order to validate this model, experimental tests carried out at COPPE/UFRJ are also described. In these tests, a typical 4″ flexible pipe was subjected to axial compression until its failure is reached. Radial and axial displacements were measured and compared to the model predictions. The good agreement between all obtained results points that the proposed FE model is efficient to estimate the response of flexible pipes to axial compression and, furthermore, has potential to be employed in the identification of the failure modes related to excessive axial compression as well as in the mechanical analysis of flexible pipes under other types of loads.

Rotary Shouldered Thread Connections: Working Limits Under Combined Static Loading

2000 ◽  
Vol 123 (3) ◽  
pp. 456-463 ◽  
Author(s):  
S. Baragetti ◽  
A. Baryshnikov
Keyword(s):  
Stress State ◽  
Oil And Gas ◽  
Fatigue Crack Initiation ◽  
Load Condition ◽  
Numerical Procedure ◽  
Experimental Tests ◽  
Drill String ◽  
Axial Tensile ◽  
Initiation And Propagation ◽  
Bending Loads

Rotary shouldered connections (RSC), used in the oil and gas industries, are probably the most stressed components of the drill string because they are subjected both to make-up torque and to axial and bending loads. Since loads can vary and can result in fatigue crack initiation and propagation, there is often severe damage to the first threads engaged. Such damage leads to shoulder load reduction and discontinuity in the drill string. Once we know the geometric dimensions and the materials of the pin and box elements composing the RSCs, API standards make it possible to evaluate the working limits of RSCs when they are subjected to make-up torque, torsion and tension. It is not, however, possible to establish the stress state of the connection for extreme working limits. The aim of this paper is to propose a numerical procedure, confirmed by full-scale experimental tests, which enables the evaluation both of the working limits, combined make-up and axial tensile loads, and of the stress state of RSCs for any load condition and, in particular, when RSCs are subjected to extreme combinations of make-up, torsion and axial tensile loads.

An Experimental and Numerical Study on the Axial Compression Response of Flexible Pipes

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
José Renato M. de Sousa ◽  
Paula F. Viero ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Axial Compression ◽  
Failure Modes ◽  
Mechanical Response ◽  
Numerical Study ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Mechanical Analysis ◽  
Fe Model ◽  
Flexible Pipe ◽  
Flexible Pipes

This paper deals with a nonlinear three-dimensional finite element (FE) model capable of predicting the mechanical response of flexible pipes subjected to axisymmetric loads focusing on their axial compression response. Moreover, in order to validate this model, experimental tests are also described. In these tests, a typical 4 in. flexible pipe was subjected to axial compression until its failure is reached. Radial and axial displacements were measured and compared to the model predictions. The good agreement between all results points out that the proposed FE model is effective to estimate the response of flexible pipes to axial compression and; furthermore, has potential to be employed in the identification of the failure modes related to excessive axial compression as well as in the mechanical analysis of flexible pipes under other types of loads.

ATLAS+ European Project: Prediction of Large Ductile Tearing in Piping Using Local Approach

2019 ◽  
Author(s):  
Arnaud Blouin ◽  
Stéphane Marie ◽  
Al Mahdi Remmal
Keyword(s):  
Laboratory Tests ◽  
Damage Model ◽  
Experimental Tests ◽  
Compact Tension ◽  
Theoretical Background ◽  
Bending Test ◽  
Continuum Damage ◽  
Single Edge ◽  
Local Approach ◽  
Ductile Tearing

Abstract In the frame of the European ATLAS+ project it was decided to evaluate if a continuum damage model can simulate a four-points beading test on a ferritic pipe (A508 type). In this paper, the theoretical background is presented. Then, based on finite elements analyses, the GTN model damage parameters are defined by simulating laboratory tests on Notched Tensile specimens and Compact Tension specimens. From that identification, experimental tests on Single Edge Notched Tensile specimens are simulated in order to verify if the previous parameters are able to describe a large ductile tearing. Finally, the four points bending test simulation is also presented.

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