scholarly journals Implementation and application of Dung’s model to analyze ductile fracture of metallic material

2015 ◽  
Vol 18 (2) ◽  
pp. 139-148
Author(s):  
Hao Nguyen Huu ◽  
Trung N. Nguyen ◽  
Hoa Vu Cong
Keyword(s):  
Volume Fraction ◽  
Void Nucleation ◽  
Damage Model ◽  
Equivalent Plastic Strain ◽  
High Strength ◽  
Ductile Fractures ◽  
Final Failure ◽  
Microscopic Damage ◽  
Ductile Behavior ◽  
Tension Loading

In this paper, the Dung’s microscopic damage model which depicts void growth under plastic deformation is applied to predict ductile fractures in high strength steel API X65. The model is implemented as a vectorized userdefined material subroutine (VUMAT) in the ABAQUS/Explicit commercial finite element code. Notched and smooth round bars under uniaxial tension loading are simulated to show the effect of equivalent plastic strain versus the void volume fraction growth of the material at and after crack initiation. Predictions of the ductile behavior from void nucleation to final failure stage are compared with the built-in Gurson – Tvergaard – Needleman (GTN) model in ABAQUS. Also, comparison with experimental results from the literature is discussed.

scholarly journals Development of a Microscopic Damage Model for Low Stress Triaxiality

2011 ◽  
Vol 473 ◽  
pp. 460-467 ◽  
Author(s):  
Mohamed Achouri ◽  
Guenael Germain ◽  
Phillippe dal Santo ◽  
Serge Boude ◽  
Jean Lou Lebrun ◽  
...  
Keyword(s):  
Hsla Steel ◽  
Damage Model ◽  
Stress Triaxiality ◽  
High Strength ◽  
Material Behavior ◽  
Shear Tests ◽  
Damage Process ◽  
Microscopic Damage ◽  
Evolution Of Microstructure

This work dealsa contribution to ductile damageof High-Strength Low-Alloy (HSLA) steel under low stress triaxiality. This work is based on micrographics observations and in-situ shear tests to examine the evolution of microstructure in this kind of loading and to identify the damage process associated. Numerical simulations by finites elements has been performed to simulate the material behavior of nucleation mechanism and the interaction between cavities during the coalescence phase, as well as the effect of the relative position of the inclusions in the shear plane.The model used as a reference in this work is the Gurson-Tvergaard- Needleman (GTN) model. It has been recently improved in order to take into account the effects of low triaxiality during shearing. A new modelisunderdevelopmentto takeintoaccounttheeffects oflowtriaxiality stresses (or loading) during shearing.

Sulfide Stability, Void Nucleation and the Toughness of Ultra High Strength Steels

1990 ◽  
Vol 186 ◽  
Author(s):  
W. M. Garrison ◽  
J. L. Maloney
Keyword(s):  
Fracture Toughness ◽  
Volume Fraction ◽  
Void Nucleation ◽  
High Strength Steels ◽  
High Strength ◽  
Calcium Sulfide ◽  
Chromium Sulfide ◽  
Ultra High Strength Steels ◽  
Inclusion Volume ◽  
Inclusion Volume Fraction

The upper shelf fracture toughness of ultra high strength steels is dependent on both the microstructure, which is determined by composition and heat treatment, and on the inclusions present in the steel. The inclusions In ultra high strength steels are typically oxides and sulfides [1]. In most ultra high strength steels the sulfides are manganese sulfides, although depending on the composition of the steel and the melt practice used, other sulfides are found, such as chromium sulfide, calcium sulfide and lanthanum oxy-sulfide [2]. If the inclusions can be regarded as pre-existing voids then the inclusion volume fraction and spacing appear to be sufficient to characterize the inclusion population from the standpoint of fracture toughness [3,4]. The purpose of this paper is to discuss results which show sulfur can be gettered as particles which are much more resistant to void nucleation than manganese sulfides and that this increased resistance to void nucleation can result in vastly improved upper shelf fracture toughness. In particular, when HY180 steel contains manganese sulfides the fracture toughness is about 250 MPa but when the sulfur is gettered as particles containing titanium, carbon and sulfur the fracture toughness of HY180 steel will approach 550 MPa . These particles, believed to be titanium carbosulfides, are much more resistant to void nucleation than manganese sulfides and this increased resistance to void nucleation appears to be the reason for the improved fracture toughness.

Flexural and Shear Strength of Granite Reinforced by Metal Rods

2010 ◽  
Vol 133-134 ◽  
pp. 417-422 ◽  
Author(s):  
Sung Gul Hong ◽  
Woo Young Lim
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
High Strength Concrete ◽  
High Strength ◽  
Stone Masonry ◽  
Experimental Program ◽  
Notched Specimens ◽  
Dowel Action ◽  
Final Failure ◽  
Ductile Behavior

This paper investigates feasibility of reinforcement method for fractured granite of slab type and beam members used as components of old stone masonry pagodas. Investigation of the effect of reinforcement to flexural and shear strength is performed using the concept for the high strength concrete since the mechanical properties of granite are similar to properties of high strength of concrete. In this experimental program two types of notched specimens are intended for failures with shear and flexural cracks. Intended fractured specimens are reinforced by metal rods, so called pinning method. The rods are inserted in holes and bonded with inorganic cement. The metal rods are supposed to transfer forces by tensile resistance in flexure and dowel action in shear. Increase in shear and flexural capacities and ductile behavior after sudden yielding of the metal rods are observed. The final failure cracks in reinforced specimens occurred different from interfaces along the original cracks. Locations of metal rods, their numbers, and construction of anchored rod are main variables to be examined for guidelines for reinforcement methods.

scholarly journals Application of a Dung’s Model to Predict Ductile Fracture of Aluminum Alloy Sheets Subjected to Deep Drawing

2015 ◽  
Vol 18 (2) ◽  
pp. 38-48
Author(s):  
Hao Nguyen-Huu ◽  
Trung N.Nguyen ◽  
Hoa Vu - Cong
Keyword(s):  
Aluminum Alloy ◽  
Deep Drawing ◽  
Void Nucleation ◽  
Yield Criterion ◽  
Matrix Material ◽  
Damage Model ◽  
Isotropic Hardening ◽  
Microscopic Damage ◽  
Von Mises ◽  
Hardening Rules

In this paper, prediction of failed evolution of anisotropic voided ductile materials will be developed based on Dung’s microscopic damage model. An isotropic and anisotropic formulation of the Dung’s damage model that using von Mises yield criterion and Hill’s quadratic anisotropic yield criterion (1948) integrated with isotropic hardening rules of matrix material used to simulate the deep drawing process of aluminum alloy sheets. The model is implemented as a vectorized user-defined material subroutine (VUMAT) in the ABAQUS/Explicit commercial finite element code. The predictions of ductile crack behavior in the specimens based on void nucleation, growth and coelescence are compared with Gurson – Tvergaard – Needleman (GTN) model and experiment results from reference.

The stabilization of B.C.C. Cu in Cu/Nb nanolayered composites

1996 ◽  
Vol 54 ◽  
pp. 228-229
Author(s):  
H. Kung ◽  
A.J. Griffin ◽  
Y.C. Lu ◽  
K.E. Sickafus ◽  
T.E. Mitchell ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Layer Thickness ◽  
Volume Fraction ◽  
Ion Beam ◽  
High Strength ◽  
Cross Sectional ◽  
Metastable Structure ◽  
High Resolution Tem ◽  
Potential Improvement ◽  
Two Phases

Materials with compositionally modulated structures have gained much attention recently due to potential improvement in electrical, magnetic and mechanical properties. Specifically, Cu-Nb laminate systems have been extensively studied mainly due to the combination of high strength, and superior thermal and electrical conductivity that can be obtained and optimized for the different applications. The effect of layer thickness on the hardness, residual stress and electrical resistivity has been investigated. In general, increases in hardness and electrical resistivity have been observed with decreasing layer thickness. In addition, reduction in structural scale has caused the formation of a metastable structure which exhibits uniquely different properties. In this study, we report the formation of b.c.c. Cu in highly textured Cu/Nb nanolayers. A series of Cu/Nb nanolayered films, with alternating Cu and Nb layers, were prepared by dc magnetron sputtering onto Si {100} wafers. The nominal total thickness of each layered film was 1 μm. The layer thickness was varied between 1 nm and 500 nm with the volume fraction of the two phases kept constant at 50%. The deposition rates and film densities were determined through a combination of profilometry and ion beam analysis techniques. Cross-sectional transmission electron microscopy (XTEM) was used to examine the structure, phase and grain size distribution of the as-sputtered films. A JEOL 3000F high resolution TEM was used to characterize the microstructure.

scholarly journals Mechanical properties, deformation and fracture mechanisms of bimodal Cu under tensile test

2021 ◽  
Vol 60 (1) ◽  
pp. 15-24
Author(s):  
Silu Liu ◽  
Yonghao Zhao
Keyword(s):  
Yield Strength ◽  
Grain Refinement ◽  
Volume Fraction ◽  
Shear Fracture ◽  
High Strength ◽  
Tensile Specimen ◽  
Deformation Mechanisms ◽  
Fracture Mechanisms ◽  
Fracture Angle ◽  
Area Reduction

Abstract Metals with a bimodal grain size distribution have been found to have both high strength and good ductility. However, the coordinated deformation mechanisms underneath the ultrafine-grains (UFGs) and coarse grains (CGs) still remain undiscovered yet. In present work, a bimodal Cu with 80% volume fraction of recrystallized micro-grains was prepared by the annealing of equal-channel angular pressing (ECAP) processed ultrafine grained Cu at 473 K for 40 min. The bimodal Cu has an optimal strength-ductility combination (yield strength of 220 MPa and ductility of 34%), a larger shear fracture angle of 83∘ and a larger area reduction of 78% compared with the as-ECAPed UFG Cu (yield strength of 410 MPa, ductility of 16%, shear fracture angle of 70∘, area reduction of 69%). Grain refinement of recrystallized micro-grains and detwinning of annealing growth twins were observed in the fractured bimodal Cu tensile specimen. The underlying deformation mechanisms for grain refinement and detwinning were analyzed and discussed.

scholarly journals The Modified Void Nucleation and Growth Model (MNAG) for Damage Evolution in BCC Ta

2021 ◽  
Vol 11 (8) ◽  
pp. 3378
Author(s):  
Jie Chen ◽  
Darby J. Luscher ◽  
Saryu J. Fensin
Keyword(s):  
Growth Model ◽  
Damage Evolution ◽  
Volume Fraction ◽  
Void Nucleation ◽  
Nucleation And Growth ◽  
Void Coalescence ◽  
Hydrodynamic Simulations ◽  
Void Evolution ◽  
Void Nucleation And Growth ◽  
Nucleation Growth

A void coalescence term was proposed as an addition to the original void nucleation and growth (NAG) model to accurately describe void evolution under dynamic loading. The new model, termed as modified void nucleation and growth model (MNAG model), incorporated analytic equations to explicitly account for the evolution of the void number density and the void volume fraction (damage) during void nucleation, growth, as well as the coalescence stage. The parameters in the MNAG model were fitted to molecular dynamics (MD) shock data for single-crystal and nanocrystalline Ta, and the corresponding nucleation, growth, and coalescence rates were extracted. The results suggested that void nucleation, growth, and coalescence rates were dependent on the orientation as well as grain size. Compared to other models, such as NAG, Cocks–Ashby, Tepla, and Tonks, which were only able to reproduce early or later stage damage evolution, the MNAG model was able to reproduce all stages associated with nucleation, growth, and coalescence. The MNAG model could provide the basis for hydrodynamic simulations to improve the fidelity of the damage nucleation and evolution in 3-D microstructures.

scholarly journals Design of Low-Cost and High-Strength Titanium Alloys Using Pseudo-Spinodal Mechanism through Diffusion Couple Technology and CALPHAD

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2910
Author(s):  
Chaoyi Ding ◽  
Chun Liu ◽  
Ligang Zhang ◽  
Di Wu ◽  
Libin Liu
Keyword(s):  
Diffusion Couple ◽  
Titanium Alloys ◽  
High Throughput ◽  
Volume Fraction ◽  
Raw Materials ◽  
Low Cost ◽  
High Strength ◽  
High Yield ◽  
Α Phase ◽  
Cr System

The high cost of development and raw materials have been obstacles to the widespread use of titanium alloys. In the present study, the high-throughput experimental method of diffusion couple combined with CALPHAD calculation was used to design and prepare the low-cost and high-strength Ti-Al-Cr system titanium alloy. The results showed that ultra-fine α phase was obtained in Ti-6Al-10.9Cr alloy designed through the pseudo-spinodal mechanism, and it has a high yield strength of 1437 ± 7 MPa. Furthermore, application of the 3D strength model of Ti-6Al-xCr alloy showed that the strength of the alloy depended on the volume fraction and thickness of the α phase. The large number of α/β interfaces produced by ultra-fine α phase greatly improved the strength of the alloy but limited its ductility. Thus, we have demonstrated that the pseudo-spinodal mechanism combined with high-throughput diffusion couple technology and CALPHAD was an efficient method to design low-cost and high-strength titanium alloys.

Numerical Investigation on Shear Failure of Concrete Beam Strengthened by Bonded Steel Plate

2013 ◽  
Vol 351-352 ◽  
pp. 1552-1557
Author(s):  
Da Guo Wang ◽  
Zhi Xiu Wang ◽  
Bing Xu
Keyword(s):  
Numerical Investigation ◽  
Concrete Beam ◽  
Shear Failure ◽  
Steel Plate ◽  
Damage Model ◽  
Adhesive Layer ◽  
Aggregate Gradation ◽  
Brittle Damage ◽  
Plastic Yield ◽  
Final Failure

Based on micromechanics, an elastic-plastic-brittle damage model of concrete beam reinforced with stick steel is proposed by considering the aggregate gradation curve algorithms and the heterogeneity. In the model, the concrete beam reinforced with stick steel is taken as a five-phase composite material that consists of the mortar matrix, coarse aggregate, bonds between mortar and aggregate, steel plate, and the adhesive layer between steel plate and concrete beam. Through the numerical investigation on shear failure of concrete beam reinforced with stick steel under external force, the results show that the model can clearly simulate microscopic plastic yield, and the initiation and extension of crack. The strength of the steel plate is relatively stronger, so it cant enhance the shear capability of the each side of the beam and the concrete beam bears the larger shear stress, which results that a large number of elements, from the supports to the load points, begin to yield. When the strain of the elements exceeds the yield strength, the elements will produce failure until the failure of the whole specimen. The final failure mode of concrete beam reinforced with stick steel is the shear failure.

Numerical Modeling of Tube Hydropiercing Using Phenomenological and Micro-Mechanical Damage Criteria

2013 ◽  
Vol 549 ◽  
pp. 172-179 ◽  
Author(s):  
Amir Hassannejadasl ◽  
Daniel E. Green
Keyword(s):  
Experimental Studies ◽  
Three Dimensional ◽  
Equivalent Plastic Strain ◽  
Mechanical Damage ◽  
High Strength ◽  
Dimensional Finite Element ◽  
Steel Dp600 ◽  
Three Dimensional Finite Element ◽  
Jc Model ◽  
Damage Criteria

Hydropiercing is an efficient way of piercing holes in mass produced hydroformed parts with complex geometries. By driving piercing punches radially into a hydroformed and fully pressurized tube, holes will be pierced and extruded into the tube-wall. Recent experimental studies have shown that the formability of advanced high strength steel (AHSS) tubes can be increased with the application of internal pressure. In this study, three-dimensional finite element simulations of a tube hydropiercing process of a dual phase steel (DP600) were performed in LS-DYNA, using phenomenological, micromechanical and combined damage criteria. Damage was included in the numerical analysis by applying constant equivalent plastic strain (CEPS), the Gurson-Tvergaard-Needleman (GTN), and the Extended GTN (GTN+JC) model. In order to calibrate the parameters in each model, a specialized hole-piercing fixture was designed and piercing tests were carried out on non-pressurized tube specimens. Of the various ductile fracture criteria, the results predicted with the GTN+JC model, such as the punch load-displacement, the roll-over depth, and the quality of the clearance zone correlated the best with the experimental data.

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