Application of EWK and Modified X-W Fracture Models to Load-Bearing Lug Joints

2014 ◽  
Vol 670-671 ◽  
pp. 1068-1072
Author(s):  
Chao Liu ◽  
Qin Sun ◽  
Yan Jie Liu
Keyword(s):  
Ductile Fracture ◽  
Fracture Initiation ◽  
Complex Stress ◽  
Loading Conditions ◽  
Load Bearing ◽  
Ductile Materials ◽  
Fracture Models ◽  
User Material Subroutine ◽  
Stress States ◽  
Lug Joints

In the aeronautic field, ductile structure usually undergoes local fracture under complicated service loading conditions, which may triggers collapse of a structure. As a result, it is very essential to study the mechanism of fracture initiation and propagation of ductile materials especially under complex stress states. In this paper, a comparative study of fracture patterns of a load-bearing lug joints structure under several loading conditions with two ductile fracture models is performed by using the commercial finite element platform ABAQUS/ Explicit through a user material subroutine VUMAT. The numerical comparisons using two ductile fracture models in predicting failure of load-bearing lug joints structure shows that modified X-W fracture model agrees well with the experimental observation under complex stress states.

scholarly journals Benefits of Using Lode Angle Dependent Fracture Models to Predict Ballistic Limits of Armor Steel

2018 ◽  
Vol 183 ◽  
pp. 01052
Author(s):  
Christian C. Roth ◽  
Teresa Fras ◽  
Norbert Faderl ◽  
Dirk Mohr
Keyword(s):  
Fracture Initiation ◽  
Strain Rates ◽  
Plastic Response ◽  
Rate Dependent ◽  
Gas Gun ◽  
Fracture Models ◽  
Armor Steel ◽  
Stress States ◽  
Impact Experiments ◽  
Single Material

Ductile fracture experiments are carried out at different stress states, strain rates and temperatures on a range of flat Mars 300 steel specimens to calibrate both a plasticity and a fracture model. To predict the onset of fracture a stress state and strain rate-dependent Hosford–Coulomb fracture initiation model is used. Single material impact experiments are performed on targets of homogenous and perforated Mars 300 plates by accelerating cylindrical Mars 300 impactors in a single-stage gas gun. It is shown that the chosen modeling approach allows accurate modeling of the plastic response as well as the fracture patterns.

Comparison of Fracture Models to Quantify the Effects of Material Plasticity on the Ductile Fracture Propagation in Pipelines

2018 ◽  
Author(s):  
Aida Nonn ◽  
Marcelo Paredes ◽  
Vincent Keim ◽  
Tomasz Wierzbicki
Keyword(s):  
Ductile Fracture ◽  
Fracture Resistance ◽  
Pipeline Steel ◽  
Ductile Failure ◽  
Fracture Propagation ◽  
Plastic Behavior ◽  
Wide Range ◽  
X100 Pipeline Steel ◽  
Fracture Models ◽  
Stress States

Various numerical approaches have been developed in the last years aimed to simulate the ductile fracture propagation in pipelines transporting CO2 or natural gas. However, a reliable quantification of the influence of material plasticity on the fracture resistance is still missing. Therefore, more accurate description of the material plasticity on the ductile fracture propagation is required based on a suitable numerical methodology. In this study, different plasticity and fracture models are compared regarding the ductile fracture propagation in X100 pipeline steel with the objective to quantify the influence of plasticity parameters on the fracture resistance. The plastic behavior of the investigated material is considered by the quadratic yield surface in conjunction with a non-associated quadratic plastic flow potential. The strain hardening can be appropriately described by the mixed Swift-Voce law. The simulations of ductile fracture are conducted by an uncoupled, modified Mohr-Coulomb (MMC) and the micromechanically based Gurson-Tvergaard-Needleman (GTN) models. In contract to the original GTN model, the MMC model is capable of describing ductile failure over wide range of stress states. Thus, ductile fracture resistance can be estimated for various load and fracture scenarios. Both models are used for the simulation of fracture propagation in DWTT and 3D pressurized pipe sections. The results from the present work can serve as a basis for establishing the correlation between plasticity parameters and ductile fracture propagation.

Mechanism-Based Numerical Approach to Ductile Fracture in an 2024–T3 Aluminium Alloy

2014 ◽  
Vol 627 ◽  
pp. 74-78
Author(s):  
Wei Jiang ◽  
Ya Zhi Li ◽  
Yi Xiu Shu ◽  
Masanori Kikuchi
Keyword(s):  
Aluminum Alloy ◽  
Ductile Fracture ◽  
Shear Fracture ◽  
Complex Loading ◽  
Numerical Approach ◽  
Shear Loading ◽  
Constitutive Relationship ◽  
Propagation Path ◽  
Loading Conditions ◽  
Ductile Materials

Ductile fracture of 2024-T3 aluminum alloy has been investigated under tensile and shear loading conditions. In order to predict rupture, a void–based meso–damage constitutive relationship which can deal with both tensile and shear problems is developed and implemented in commercial software ABAQUS. The tensile and shear fracture behaviors including the load–displacement response and crack propagation path, of 2024–T3 aluminum alloy are analyzed using the proposed approach and compared with experimental data. It is shown that the proposed approach can be used to predict the failure of ductile materials under complex loading conditions.

Brittle Fracture Initiation Under Complex Stress States

1983 ◽  
Vol 105 (3) ◽  
pp. 143-148 ◽  
Author(s):  
J. Takagi ◽  
M. C. Shaw
Keyword(s):  
Brittle Fracture ◽  
Crack Initiation ◽  
Plane Stress ◽  
Fracture Initiation ◽  
Quantitative Agreement ◽  
Complex Stress ◽  
Good Qualitative Agreement ◽  
Classic Theory ◽  
Stress States ◽  
Disk Test

The brittle fracture locus for crack initiation in several brittle materials under biaxial states of plane stress is determined experimentally and compared with the classic theory due to Griffith. While good qualitative agreement is observed, the quantitative agreement is poor. It is found that replacing the two-dimensional hairline crack assumed by Griffith by a similar circular one leads to much better agreement between theory and experiment. The plane stress disk test is considered in terms of the new theory and some previously misunderstood aspects of this test are explained. Finally, the relation between crack initiation and crack propagation is briefly discussed.

Experimental Study to Calibrate Monotonic Micromechanics-Based Fracture Models of Q345 Steel

2011 ◽  
Vol 261-263 ◽  
pp. 545-550 ◽  
Author(s):  
Fang Fang Liao ◽  
Wei Wang ◽  
Yi Yi Chen
Keyword(s):  
Ductile Fracture ◽  
Good Accuracy ◽  
Steel Structures ◽  
Fracture Initiation ◽  
Monotonic Loading ◽  
Welded Steel ◽  
Steel Connections ◽  
Metal Deposit ◽  
Fracture Models ◽  
Material Tests

Micromechanics-based facture models have been proved to predict ductile fracture in steel structures with good accuracy. The stress modified critical strain (SMCS) model and the void growth model (VGM) are suitable to predict fracture initiation under monotonic loading. In order to calibrate the parameters in these models for the largely used Q345 steel in China, material tests, scanning electron microscope tests and finite element analyses were conducted. The test specimens were made from base metal, deposit metal and heat affected zone of Q345 steel to investigate crack initiation in welded connections. The results of this paper can be applied to predict ductile fracture in welded steel connections under monotonic loading.

scholarly journals Investigation of deformation twinning under complex stress states in a rolled magnesium alloy

2016 ◽  
Vol 683 ◽  
pp. 619-633 ◽  
Author(s):  
Wei Wu ◽  
Chih-Pin Chuang ◽  
Dongxiao Qiao ◽  
Yang Ren ◽  
Ke An
Keyword(s):  
Magnesium Alloy ◽  
Complex Stress ◽  
Deformation Twinning ◽  
Stress States

scholarly journals Prediction of Ductile Fracture in Metal Blanking

1999 ◽  
Vol 122 (3) ◽  
pp. 476-483 ◽  
Author(s):  
A. M. Goijaerts ◽  
L. E. Govaert ◽  
F. P. T. Baaijens
Keyword(s):  
Finite Element ◽  
Tensile Test ◽  
Ductile Fracture ◽  
Experimental Error ◽  
Fracture Initiation ◽  
Fracture Model ◽  
Ductile Fracture Model ◽  
Blanking Process ◽  
Ductile Fracture Initiation

This study is focused on the description of ductile fracture initiation, which is needed to predict product shapes in the blanking process. Two approaches are elaborated using a local ductile fracture model. According to literature, characterization of such a model should take place under loading conditions, comparable to the application. Therefore, the first approach incorporates the characterization of a ductile fracture model in a blanking experiment. The second approach is more favorable for industry. In this approach a tensile test is used to characterize the fracture model, instead of a complex and elaborate blanking experiment. Finite element simulations and blanking experiments are performed for five different clearances to validate both approaches. In conclusion it can be stated that for the investigated material, the first approach gives very good results within the experimental error. The second approach, the more favorable one for industry, yields results within 6 percent of the experiments over a wide, industrial range of clearances, when a newly proposed criterion is used. [S1087-1357(00)02202-4]

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