scholarly journals Effect of Stress Triaxiality on Plastic Damage Evolution and Failure Mode for 316L Notched Specimen

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1067 ◽  
Author(s):  
Peng ◽  
Wang ◽  
Dai ◽  
Liu ◽  
Liu ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Failure Mode ◽  
Damage Evolution ◽  
Stress Triaxiality ◽  
Image Correlation ◽  
Void Coalescence ◽  
Notched Specimen ◽  
Plastic Damage ◽  
Element Simulation

To reveal the effect of stress triaxiality on plastic damage evolution and failure mode, 316L notched specimens with different notch sizes are systematically investigated by digital image correlation (DIC) observation, plastic damage analysis by finite element simulation, and void mesoscopic observation. It was found that the plastic damage evolution and failure mode are closely related with notch radius and stress triaxiality. The greater the stress triaxiality at the root is, the greater the damage value at the root is and the earlier the fracture occurs. Moreover, void distribution by mesoscopic observation agrees well with damage distribution observed by finite element simulation with the Gurson-Tvergaard-Needleman (GTN) damage model. It is worth noting that, with the increase in stress triaxiality, the failure mode of notched specimen changes from ductility fracture with void coalescence at the center position to crack initiation at the notch root, from both mesoscopic observation and damage simulation.

Behavior of polyethylene under different triaxial stress states: An experimental and numerical study

2020 ◽  
pp. 146442072097058
Author(s):  
Limei Han ◽  
Yi Zhang ◽  
Shifeng Xue ◽  
Bo Zhou ◽  
Cuiwei Liu
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Damage Evolution ◽  
Fracture Strain ◽  
Damage Model ◽  
Stress Triaxiality ◽  
True Stress ◽  
Triaxial Stress ◽  
Element Simulation ◽  
Stress States

The behavior of a semi-crystalline polymer under different triaxial stress states is studied through the combination of experimental testing and finite element simulation. Polyethylene round bar specimens with four different notch radii were stretched at crosshead speed of 1 mm/min until fracture. The continuum damage mechanics damage model and Gurson–Tvergaard–Needleman damage model were proposed and applied to the finite element simulation. The results of engineering stress–displacement curves determined from finite element simulation match experimental results. Finite element simulation without considering damage and with the consideration of damage was conducted to determine the damaged and undamaged true stress–strain relationship of polyethylene materials, respectively. Damage evolution model was established based on the degradation of true stress. The finite element model was further applied to study the distribution of stress triaxiality for specimens with different notch radii and the effect of stress triaxiality on damage evolution, critical damage parameters, and fracture strain. The results show that the distribution of the stress triaxiality on the cross section of the specimen is not uniform, and as the stress triaxiality increases, the position where the maximum stress triaxiality occurs moves from the center point to two-third the radius from the center. Furthermore, the damaged true stress and the undamaged true stress increases with the decrease of the stress triaxiality when the strain is below 0.3, but decreases with the increase of stress triaxiality when the strain is larger than 0.3. In addition, it was found that the greater the stress triaxiality, the earlier the onset of damage and the faster the evolution, but the smaller the fracture strain.

Numerische Abbildung von Beton mit einem plastischen Schädigungsmodell – Grundlegende Untersuchungen zu Normalbeton und UHPC/Finite element simulation of concrete with a plastic damage model – Basic studies on normal strength concrete and UHPC

Bauingenieur ◽  
2015 ◽  
Vol 90 (06) ◽  
pp. 252-264 ◽  
Author(s):  
Dominik Kueres ◽  
Alexander Stark ◽  
Martin Herbrand ◽  
Martin Classen
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Damage Model ◽  
Normal Strength Concrete ◽  
Numerische Simulation ◽  
Plastic Damage ◽  
Element Simulation ◽  
Finite Elemente ◽  
Normal Strength ◽  
Basic Studies

Die numerische Simulation des Tragverhaltens von Beton- und Stahlbetonkonstruktionen mit nicht-linearen Finite-Elemente-Modellen gewinnt in der konstruktiven Ingenieurpraxis zunehmend an Bedeutung. In kommerziellen Finite-Elemente-Programmen stehen dem Anwender unterschiedliche Möglichkeiten zur Abbildung des Betonverhaltens in Form von plastischen Materialmodellen zur Verfügung. Zur Anwendung dieser Materialmodelle ist dabei in der Regel die Kenntnis des Betontragverhaltens unter einaxialer Druck- und Zugbeanspruchung erforderlich. Im vorliegenden Beitrag werden verschiedene Ansätze zur mathematischen Beschreibung dieser konstitutiven Beziehungen für Normalbeton und ultrahochfesten Beton (UHPC) vorgestellt und im Hinblick auf ihre Anwendbarkeit in plastischen Materialmodellen untersucht. Darauf aufbauend werden numerische Simulationen mit einem plastischen Schädigungsmodell unter Verwendung eines einheitlichen Parametersatzes durchgeführt und mit den Ergebnissen experimenteller Untersuchungen verglichen. Die Untersuchungen umfassen hierbei Materialprüfungen an Normalbeton und UHPC unter verschiedenen ein- und mehraxialen Spannungszuständen. Durch die Wahl geeigneter konstitutiver Beziehungen kann für die untersuchten Spannungszustände eine gute Übereinstimmung zwischen simuliertem und experimentell ermitteltem Betontragverhalten erreicht werden.

Numerical simulation of ductile fracture in polyethylene pipe with continuum damage mechanics and Gurson-Tvergaard-Needleman damage models

2019 ◽  
Vol 233 (12) ◽  
pp. 2455-2468
Author(s):  
Yi Zhang ◽  
P-Y Ben Jar ◽  
Shifeng Xue ◽  
Lin Li
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Constitutive Equations ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Experimental Testing ◽  
Monotonic Loading ◽  
Test Method ◽  
Strain Level ◽  
Element Simulation

A phenomenon-based hybrid approach of experimental testing and finite element simulations is used to describe the fracture behavior of pipe-grade polyethylene. The experimental testing adopts a modified D-split test method to stretch the pipe ring (notched pipe ring) specimens that have symmetric, double-edged flat notches along the pipe direction. Two series of experimental testing were conducted: (1) monotonic loading till fracture and (2) monotonic loading to a predefined strain level, keeping constant displacement for a period of time, and then unloaded. Crosshead speeds of 0.01, 1, and 100 mm/min were used in both series of tests. Likewise, two series of finite element simulation were conducted to establish the constitutive equations, either with or without considering damage evolution during the deformation process. The constitutive equation without the consideration of damage was established using results from the first series of experimental testing, and that with damage was inspired from the second series which showed the decrease in unloading modulus with the increase of crosshead speed or the predefined strain level. The results show that with the consideration of damage evolution, the constitutive equations enable the finite element simulation to determine the whole stress–strain relationship during both necking and fracture processes.

Local Approach of Fracture in the Ductile Regime and Application to VVER Materials

2002 ◽  
Author(s):  
B. Z. Margolin ◽  
V. I. Kostylev ◽  
E. Keim ◽  
R. Chaouadi
Keyword(s):  
Finite Element ◽  
Crack Resistance ◽  
Ductile Fracture ◽  
Finite Element Simulation ◽  
Volume Fraction ◽  
Stress Triaxiality ◽  
Local Approach ◽  
Gurson Model ◽  
Element Simulation

Within the TACIS R2.06/96 project: “Surveillance Program for VVER 1000 Reactors”, sponsored by the European Commission, the local approach of fracture has been applied in the ductile regime. Two different models were applied and compared, namely Tvergaard-Needleman-Gurson versus Prometey model. The main tasks are: • perform special Local Approach experiments on smooth and notched cylindrical specimens; • predict JR-curve on the basis of the ductile fracture models; • compare two models of ductile fracture, namely, the Tvergaard-Needleman-Gurson model and the Prometey model. In this paper, the Tvergaard-Needleman-Gurson and Prometey models are briefly described. The parameters of both models were calibrated by using experimental data obtained on tensile specimens. While only smooth tensile specimens are used to calibrate the Tvergaard-Needleman-Gurson model, notched tensile in addition to smooth tensile specimens are used to calibrate the Prometey model. In the latter, standard smooth tensile specimens are used to determine the mechanical properties (the yield stress σy, the ultimate stress σu, the ultimate elongation δu, the area reduction Z) and notched cylindrical specimens to determine the strain at rupture. The numerical analysis comprises essentially two steps: • Step 1: finite element simulation of the smooth tensile specimen (determination of true stress-strain curve and critical void volume fraction for the Tvergaard-Needleman-Gurson model) and simulation of the notched cylindrical specimen up to rupture (determination of stress triaxiality for the Prometey model); • Step 2: finite element simulation of the 2T CT specimen and determination of the crack resistance behaviour in the ductile regime (J-Δa curve). It is found that both models were able to correctly predict the crack resistance behaviour of the investigated materials. The numerical and the experimental results were in very good agreement. The main difference between the two models is that the required number of calibrated parameters in the Prometey model is less than in the Tvergaard-Needleman-Gurson model but additional tests on notched specimens are required for the Prometey model.

scholarly journals Modeling the influence of connecting elements in wood products behavior: a numerical multi-scale approach

2018 ◽  
Vol 19 (3) ◽  
pp. 301 ◽  
Author(s):  
Luc Chevalier ◽  
Heba Makhlouf ◽  
Benoît Jacquet-Faucillon ◽  
Eric Launay
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Failure Process ◽  
Numerical Procedure ◽  
Wood Products ◽  
Image Correlation ◽  
Bending Test ◽  
3D Finite Element ◽  
Multi Scale ◽  
Element Simulation

Wood furniture is often composed of simple parts that may be modeled as beams or plates. These particularities allow using simplified approaches that reduces the number of degrees of freedom (dof for short) in a finite element simulation of the furniture's behavior. Generally, connections are not taken into account in such simulations but these connections are critical in the failure process of the furniture and it worth studying it precisely. Using a multi-scale approach, this paper introduces a numerical procedure to identify the connection contribution in the furniture's stiffness. Comparing 3D finite element calculations with a Timoshenko's beam calculation on a corner of two wooden parts, we identify the specific behavior of the connection elements (pins, nut, screw… and local 3D effects) to introduce it as a punctual 0D element in the beam code. Two validations of the approach are presented here: (i) a numerical validation by comparing the result of the beam code with a complete 3D finite element simulation on a representative plane structure of wooden furniture; (ii) an experimental validation by managing a global bending test and measuring the displacement field using digital image correlation (DIC for short).

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