scholarly journals Localized Necking Model for Punching Fracture Simulation in Unstiffened and Stiffened Panels

2021 ◽  
Vol 11 (9) ◽  
pp. 3774
Author(s):  
Sung-Ju Park ◽  
Kookhyun Kim
Keyword(s):  
Ductile Fracture ◽  
Fracture Initiation ◽  
Fracture Model ◽  
Model Parameters ◽  
Stiffened Panels ◽  
Plane Strain Tension ◽  
Localized Necking ◽  
Hardening Law ◽  
Numerical Predictions ◽  
Fracture Simulation

The ductile fracture of thin-shell structures was studied here using a localized necking model. The punching experiments for unstiffened and stiffened panels were compared with numerical predictions using a combined ductile fracture and localized necking model using shell elements. The plasticity and fracture model parameters of JIS G3131 SPHC steel were identified by performing calibration experiments on standard flat bars, notched tension, central hole tension, plane strain tension, and shear specimens. The plasticity beyond the onset of necking was modeled using the Swift hardening law. The damage indicator framework with a combined Hosford–Coulomb fracture model and the domain of shell-to-solid equivalence (DSSE) were adopted to characterize the fracture initiation. The model parameters were calibrated based on the loading paths to fracture initiation, which were extracted from a non-linear finite element (FE) analysis. The presented HC–DSSE model was validated using punch tests and was able to predict fracture initiation with good accuracy.

scholarly journals Evaluation of Localized Necking Models for Fracture Prediction in Punch-Loaded Steel Panels

2021 ◽  
Vol 9 (2) ◽  
pp. 117
Author(s):  
Burak Can Cerik ◽  
Kangsu Lee ◽  
Joonmo Choung
Keyword(s):  
Mesh Size ◽  
Fracture Initiation ◽  
Analytical Models ◽  
Original Form ◽  
Proportional Loading ◽  
Stiffened Panels ◽  
Shell Elements ◽  
Localized Necking ◽  
Numerical Predictions ◽  
Steel Panels

This study compared the experimental test results on punch-loaded unstiffened and stiffened panels with numerical predictions using different localized necking modeling approaches with shell elements. The analytical models that were derived by Bressan–Williams–Hill (BWH) were used in their original form and extended version, which considers non-proportional loading paths while using the forming-severity concept and bending-induced suppression of through-thickness necking. The results suggest that the mesh size sensitivity depends on the punch geometry. Moreover, the inclusion of bending effects and the use of the forming-severity concept in the BWH criterion yielded improved estimations of fracture initiation with shell elements.

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]

Assessment of Gurson-Tveergard-Needleman Model Under High Stress Triaxiality

2016 ◽  
Author(s):  
Jiru Zhong ◽  
Tong Xu ◽  
Kaishu Guan
Keyword(s):  
Ductile Fracture ◽  
Volume Fraction ◽  
Stress Triaxiality ◽  
Fracture Initiation ◽  
Tensile Specimen ◽  
Void Volume Fraction ◽  
Model Parameters ◽  
Gtn Model ◽  
Notched Specimens ◽  
Critical Void

The Gurson-Tveergard-Needleman (GTN) model has been widely used to describe ductile fracture. In this paper, a series of tensile tests were carried out on notched specimens to assess the GTN model. The GTN model parameters were calibrated from a smooth tensile specimen by a hybrid particle swarm optimization, and the reliability of the calibrated parameters was verified by the profile of the smooth tensile specimen. The calibrated parameters were used to predict the ductile fracture of notched specimens. A comparison of fracture initiation sites between simulations and experiments indicates that the GTN model has a good performance on predicting fracture initiation site but fails at predicting fracture moment. The assessment of the transformability of the GTN model parameters was performed by comparing the load-displacement curves between simulations and experiments. It is observed that the GTN model parameters are material constant, except the critical void volume fraction fc. The influence of stress triaxiality on the critical void volume fraction fc is also discussed.

scholarly journals Modeling of Ductile Fracture for SS275 Structural Steel Sheets

2021 ◽  
Vol 11 (12) ◽  
pp. 5392
Author(s):  
Yonghyun Cho ◽  
Changkye Lee ◽  
Jurng-Jae Yee ◽  
Dong-Keon Kim
Keyword(s):  
Finite Element ◽  
Ductile Fracture ◽  
Structural Steel ◽  
Fracture Behavior ◽  
Weighted Average ◽  
Image Correlation ◽  
Model Parameters ◽  
Suitable Model ◽  
Element Analysis ◽  
Fracture Simulation

A series of earthquake events give impetus to research on the ductile fracture behavior of steel materials. In the last decades, many fracture models have been developed and utilized in the mechanical or aerospace engineering. Nevertheless, very little application to structural members used in the construction industry has been made due to the lack of a suitable model for the fracture behavior of constructional steel. This paper presents the experimental and finite element (FE) technique to predict ductile fracture in mild carbon structural steel (SS275) sheets, which has been widely used in building structures. The post-necking true stress–strain responses were successfully estimated using the weighted-average method. The Bao and Wierzbicki (BW) model, which requires only two model parameters, was selected for the identification of fracture locus. Each model parameter was calibrated from uniaxial tension and in-plane shear specimens with the aid of digital image correlation (DIC) and finite element analysis. Fracture simulation was then performed and validated based on the experimental results of the specimens under combined tension and shear stress state.

Anisotropic Ductile Fracture of AA6260-T6 Al-Alloy Extrusions

2011 ◽  
Author(s):  
M. Luo ◽  
T. Wierzbicki ◽  
D. Mohr
Keyword(s):  
Ductile Fracture ◽  
Weighting Function ◽  
Extrusion Direction ◽  
Material Point ◽  
Surface Strain ◽  
Image Correlation ◽  
Fracture Model ◽  
Model Parameters ◽  
Al Alloy ◽  
Wide Range

The anisotropic ductile fracture of AA6260-T6 extruded aluminum alloy profiles is studied within a phenomenological framework. A basic fracture testing program covering a wide range of stress states and three distinct material orientations (i.e. 0°, 45° and 90° with respect to the extrusion direction) is carried out. It comprises notched tensile specimens, tensile specimens with a central hole, butterfly shear specimens and circular punch specimens. The surface strain fields are determined using Digital Image Correlation (DIC), while a finite element simulation is performed of each experiment to determine the local stress and strain histories at the material point where fracture initiates. The experimental-numerical analysis reveals a strong anisotropy of the present material ductility/fracture, which cannot be approximated by existing isotropic fracture models. A new non-associated anisotropic fracture model is proposed incorporating the stress state dependent Modified Mohr-Coulomb (MMC) weighting function and a material direction sensitive damage rule. All seven fracture model parameters are identified for the present extruded aluminum using an inverse method. The good agreement of the model predictions with the results from fourteen distinct experiments demonstrates the remarkable predictive capabilities of the proposed model.

Experimental and Numerical Investigation on the Influence of Process Speed on the Blanking Process

2002 ◽  
Vol 124 (2) ◽  
pp. 416-419 ◽  
Author(s):  
A. M. Goijaerts ◽  
L. E. Govaert ◽  
F. P. T. Baaijens
Keyword(s):  
Stainless Steel ◽  
Constitutive Model ◽  
Numerical Simulations ◽  
Ferritic Stainless Steel ◽  
Fracture Criterion ◽  
Fracture Initiation ◽  
Rate Dependence ◽  
Numerical Predictions ◽  
Punch Velocity ◽  
Blanking Process

In a previous work a numerical tool was presented which accurately predicted both process force and fracture initiation for blanking of a ferritic stainless steel in various blanking geometries. This approach was based on the finite element method, employing a rate-independent elasto-plastic constitutive model combined with a fracture criterion which accounts for the complete loading history. In the present investigation this work is extended with respect to rate-dependence by employing an elasto-viscoplastic constitutive model in combination with the previously postulated fracture criterion for ferritic stainless steel. Numerical predictions are compared to experimental data over a large range of process speeds. The rate-dependence of the process force is significant and accurately captured by the numerical simulations at speeds ranging from 0.001 to 10 mm/s. Both experiments and numerical simulations show no influence of punch velocity on fracture initiation.

Transferability of the Gurson Damage Model Parameters with Charpy and Tensile Tests with Different Constrain Level

2009 ◽  
Vol 65 ◽  
pp. 19-31
Author(s):  
Ruben Cuamatzi-Melendez ◽  
J.R. Yates
Keyword(s):  
Strain Rate ◽  
Damage Model ◽  
Rolling Direction ◽  
Fracture Initiation ◽  
Tensile Tests ◽  
Model Parameters ◽  
Gurson Model ◽  
Finite Element Program ◽  
Element Program ◽  
Gurson's Model

Little work has been published concerning the transferability of Gurson’s ductile damage model parameters in specimens tested at different strain rates and in the rolling direction of a Grade A ship plate steel. In order to investigate the transferability of the damage model parameters of Gurson’s model, tensile specimens with different constraint level and impact Charpy specimens were simulated to investigate the effect of the strain rate on the damage model parameters of Gurson model. The simulations were performed with the finite element program ABAQUS Explicit [1]. ABAQUS Explicit is ideally suited for the solution of complex nonlinear dynamic and quasi–static problems [2], especially those involving impact and other highly discontinuous events. ABAQUS Explicit supports not only stress–displacement analyses but also fully coupled transient dynamic temperature, displacement, acoustic and coupled acoustic–structural analyses. This makes the program very suitable for modelling fracture initiation and propagation. In ABAQUS Explicit, the element deletion technique is provided, so the damaged or dead elements are removed from the analysis once the failure criterion is locally reached. This simulates crack growth through the microstructure. It was found that the variation of the strain rate affects slightly the value of the damage model parameters of Gurson model.

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