The Conditions at Ductile Fracture in Tension Tests

2009 ◽  
pp. 115-115-18
Author(s):  
RJ Dexter ◽  
S Roy
Keyword(s):  
Ductile Fracture ◽  
Tension Tests

scholarly journals Comparison of Modified Mohr–Coulomb Model and Bai–Wierzbicki Model for Constructing 3D Ductile Fracture Envelope of AA6063

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Jianye Gao ◽  
Tao He ◽  
Yuanming Huo ◽  
Miao Song ◽  
Tingting Yao ◽  
...  
Keyword(s):  
Ductile Fracture ◽  
Fracture Criterion ◽  
Fracture Strain ◽  
Stress Triaxiality ◽  
Ductile Fracture Criterion ◽  
Forming Process ◽  
Tension Tests ◽  
Wide Range ◽  
Round Bar ◽  
Fracture Envelope

AbstractDuctile fracture of metal often occurs in the plastic forming process of parts. The establishment of ductile fracture criterion can effectively guide the selection of process parameters and avoid ductile fracture of parts during machining. The 3D ductile fracture envelope of AA6063-T6 was developed to predict and prevent its fracture. Smooth round bar tension tests were performed to characterize the flow stress, and a series of experiments were conducted to characterize the ductile fracture firstly, such as notched round bar 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-Wierzbicki (BW) model to develop the 3D ductile fracture envelope. Finally, two ductile damage models were proposed based on the 3D fracture envelope of AA6063. Through the comparison of the two models, it was found that BW model had better fitting effect, and the sum of squares of residual error of BW model was 0.9901. The two models had relatively large errors in predicting the fracture strain of SRB tensile test and torsion test, but both of the predicting error of both two models were within the acceptable range of 15%. In the process of finite element simulation, the evolution process of ductile fracture can be well simulated by the two models. However, BW model can predict the location of fracture more accurately than MMC model.

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.

scholarly journals Comparison of modified Mohr–Coulomb model and Bai–Wierzbicki model for constructing 3D ductile fracture envelope of AA6063

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

Abstract The 3D ductile fracture envelope of AA6063-T6 were developed to predict and prevent its fracture. Smooth round bar tension tests were performed to characterize the flow stress, and a series of experiments were conducted to characterize the ductile fracture firstly, such as notched round bar 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-Wierzbicki (BW) model to develop the 3D ductile fracture envelope. Finally, two ductile damage models were proposed based on 3D fracture envolope of AA6063. Through the comparison of the two models, it was found that BW model had better fitting effect, and the sum of squares of residual error of BW model was 0.9901. The two models had relatively large errors in predicting the fracture strain of SRB tensile test and torsion test, but both of the predicting error of both two models were within the acceptable range of 15%. In the process of finite element simulation, the evolution process of ductile fracture can be well simulated by the two models. However, BW model can predict the location of fracture more accurately than MMC model.

scholarly journals Comparison of modified Mohr–Coulomb model and Bai–Wierzbicki model for constructing 3D ductile fracture envelope of AA6063

2021 ◽  
Author(s):  
Jianye Gao ◽  
Tao He ◽  
Yuanming Huo ◽  
Miao Song ◽  
Tingting Yao ◽  
...  
Keyword(s):  
Ductile Fracture ◽  
Fracture Criterion ◽  
Fracture Strain ◽  
Stress Triaxiality ◽  
Ductile Fracture Criterion ◽  
Forming Process ◽  
Tension Tests ◽  
Wide Range ◽  
Round Bar ◽  
Fracture Envelope

Abstract Ductile fracture of metal often occurs in the plastic forming process of parts. The establishment of ductile fracture criterion can effectively guide the selection of process parameters and avoid ductile fracture of parts during machining. The 3D ductile fracture envelope of AA6063-T6 were developed to predict and prevent its fracture. Smooth round bar tension tests were performed to characterize the flow stress, and a series of experiments were conducted to characterize the ductile fracture firstly, such as notched round bar 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-Wierzbicki (BW) model to develop the 3D ductile fracture envelope. Finally, two ductile damage models were proposed based on the 3D fracture envelope of AA6063. Through the comparison of the two models, it was found that BW model had better fitting effect, and the sum of squares of residual error of BW model was 0.9901. The two models had relatively large errors in predicting the fracture strain of SRB tensile test and torsion test, but both of the predicting error of both two models were within the acceptable range of 15%. In the process of finite element simulation, the evolution process of ductile fracture can be well simulated by the two models. However, BW model can predict the location of fracture more accurately than MMC model.

Investigation of ductile fracture behavior of lap-welded joints with 460 MPa steel

2017 ◽  
Vol 21 (9) ◽  
pp. 1376-1387 ◽  
Author(s):  
Gang Shi ◽  
Yufeng Chen
Keyword(s):  
Ductile Fracture ◽  
Welded Joints ◽  
High Strength Steel ◽  
Fracture Behavior ◽  
Steel Structures ◽  
High Strength ◽  
Welded Steel ◽  
Fracture Parameters ◽  
Tension Tests ◽  
Micromechanics Models

Fractures in welded connections usually occurred at Earthquake. The lap-welded joints are an important type of welded connections in high strength steel structures. In this article, the ductile fracture behavior of lap-welded joints has been studied experimentally and numerically with 460 MPa steel. A series of coupon tests were used to determine two corresponding weld materials (ER55-D2 and ER55-G) mechanical properties. Two micromechanics models (void growth model and stress-modified critical strain models) had been calibrated by circumferentially notched tension specimens and calculated the fracture parameters numerically, which had been applied in predicting in five lap-welded joints. The experimental study showed that the fracture mode of 460 MPa lap-welded joints exhibited plastic damage under the tension tests. Numerical analysis of the fracture parameters also showed that the ductile fracture behavior of lap-welded joint with ER55-G was better. The study establishes an accurate numerical model for analyzing the ductile fracture behavior of Q460 high strength steel lap-welded joints that is applicable in predicting the fracture failure of welded steel structures.

Prediction of ductile fracture for Al6016-T4 with a ductile fracture criterion: Experiment and simulation

2019 ◽  
Vol 29 (8) ◽  
pp. 1199-1221 ◽  
Author(s):  
Saijun Zhang ◽  
Yanchun Lu ◽  
Zhaohui Shen ◽  
Chi Zhou ◽  
Yanshan Lou
Keyword(s):  
Ductile Fracture ◽  
Metal Forming ◽  
Fracture Criterion ◽  
Stress Triaxiality ◽  
Yield Function ◽  
Isotropic Hardening ◽  
Ductile Fracture Criterion ◽  
Fracture Locus ◽  
Hardening Law ◽  
Tension Tests

The key point in this paper is the prediction of the onset of ductile fracture with a newly proposed ductile fracture criterion in various stress state ranging from shear to uniaxial tension. A series of tension tests with different material orientations are carried out up to fracture. The anisotropic Drucker yield function with an isotropic hardening law is identified to describe the elastic–plastic behaviors of Al6016-T4 aluminum alloy. The uncoupled ductile fracture criterion is calibrated and then utilized to construct the fracture locus of Al6016-T4, which is implemented into the ABAQUS/Explicit to validate the prediction of ductile fracture criterion by comparing experimental results to numerical ones. The validation demonstrates that the ductile fracture criterion can accurately predict the onset of ductile fracture for Al6016-T4 in medium stress triaxiality ranging from 0.1 to 0.44 where most ductile fracture occurs in sheet metal forming.

scholarly journals Micromechanical modelling of ductile fracture in pipeline steel using a bifurcation-enriched porous plasticity model

2020 ◽  
Vol 227 (1) ◽  
pp. 57-78
Author(s):  
Sondre Bergo ◽  
David Morin ◽  
Tore Børvik ◽  
Odd Sture Hopperstad
Keyword(s):  
Ductile Fracture ◽  
Pipeline Steel ◽  
Simulation Models ◽  
Void Coalescence ◽  
Explicit Finite Element ◽  
Gtn Model ◽  
Porous Plasticity ◽  
Tension Tests ◽  
Wide Range

AbstractIn this paper, we investigate the possibility of predicting ductile fracture of pipeline steel by using the Gurson–Tvergaard–Needleman (GTN) model where the onset of void coalescence is determined based on in situ bifurcation analyses. To this end, three variants of the GTN model, one of which includes in situ bifurcation, are calibrated for a pipeline steel grade X65 using uniaxial and notch tension tests. Then plane-strain tension tests and Kahn tear tests of the same material are used for assessment of the credibility of the three models. Explicit finite element simulations are carried out for all tests using the three variants of the GTN model, and the results are compared to the experimental data. The capability of the simulation models to capture onset of fracture and crack propagation in the pipeline steel is evaluated. It is found that the use of in situ bifurcation as a criterion for onset of void coalescence in each element makes the GTN model easier to calibrate with less free parameters, all the while obtaining similar or even better predictions as other widely used formulations of the GTN model over a wide range of different stress states.

Strength of three-sheet spot welds with critical nugget sizes in tensile shear, cross tension, peel and fatigue tests

2021 ◽  
pp. 146442072110663
Author(s):  
K Siimut ◽  
MFR Zwicker ◽  
CV Nielsen
Keyword(s):  
Ductile Fracture ◽  
Thin Sheet ◽  
Fatigue Tests ◽  
Weld Strength ◽  
Tensile Shear ◽  
Spot Welds ◽  
Load Range ◽  
Tension Tests ◽  
Lower Load ◽  
Cross Tension

Plug failures have been observed in three-sheet spot welds, where the weld nugget did not penetrate into the outer sheet. Such solid-state bonds were found to be formed as a result of high contact pressure and temperature during welding. The strength of single spot welds was studied in a three-sheet combination (0.61 mm DX54 on two 1.21 mm DP600) with nugget penetrations into the thin sheet below 40%. The static strength was evaluated by tensile shear, cross tension and mechanized peel testing, and fatigue tests were carried out in tensile shear configuration at 30 Hz and mean load of 2 kN. It was found that loading of the specimens in tensile shear, mechanized peel and cross tension tests leads to a plug failure and a ductile fracture of the thin sheet. The weld strength is not correlated with the nugget penetration into the thin sheet but is determined by the area of the bonded interface, instead, as shown by peel and cross tension tests. Fatigue tests revealed that the specimens break by a plug failure. The failure mechanism was found to be ductile for the highest load range after approximately 33 000 cycles. At lower load ranges, evidence of a crack was found in the DX54 sheet, leading to higher stress concentration and subsequent ductile fracture. It was estimated that a load range of 940 N leads to failure after approximately 106 cycles.

Intertester-Reliabilität des Upper Limb Neural Tension Tests (ULNT) 1

2019 ◽  
Vol 23 (02) ◽  
pp. 75-80
Author(s):  
Beate Schüßler ◽  
Andrea Pfingsten ◽  
Thomas Schöttker-Königer
Keyword(s):  
Upper Limb ◽  
Tension Test ◽  
Tension Tests

ZusammenfassungZur Überprüfung der Nervenleitfähigkeit werden Kraft, Reflexe und Sensibilität getestet. Bei der Untersuchung der Mechanosensitivität eines Nervs kommen neurodynamische Tests zum Einsatz. Der Upper Limb Neural Tension Test (ULNT) 1 bestimmt die Mechanosensitivität des N. medianus.Ziel der Studie war die Untersuchung der Intertester-Reliabilität des ULNT 1 von nicht spezialisierten Physiotherapeuten bei Probanden mit unilateralen Nacken- und/oder Armsymptomen.Die Therapeuten beurteilten binär und metrisch die Kriterien patientenspezifische Symptome, strukturelle Differenzierung und Bewegungsausmaß sowie das Gesamtergebnis bei 33 Patienten mit unilateralen Nacken- und/oder Armsymptomen. Bei den binären Daten bestimmte der Fleiss-Kappa und bei den metrischen Daten der Intraklassen-Korrelationskoeffizient die Reliabilität. Die zusätzlich erstellten Regressionsmodelle sollten den Einfluss der einzelnen Beurteilungskriterien auf die Gesamtentscheidung herausfiltern.Mit Ausnahme der Reproduzierbarkeit patientenspezifischer Symptome scheint die Beurteilung des ULNT 1 durch nicht spezialisierte Therapeuten nur schlecht vergleichbar zu sein. Da die metrische Bewertungsweise die individuellen Schwellenwerte besser darstellt, ist diese der binären vorzuziehen.

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