A Plasticity Induced Anisotropic Damage Model for Sheet Forming Processes

The global fuel crisis and increasing public safety concerns are driving the automotive industry to design high strength and low weight vehicles. The development of Dual Phase (DP) steels has been a big step forward in achieving this goal. DP steels are used in many automotive body-in-white structural components such as A and B pillar reinforcements, longitudinal members and crash structure parts. DP steels are also used in other industrial sectors such as precision tubes, train seats and Liquid Petroleum Gas (LPG) cylinders. Although the ductility of DP steel is higher than classical high strength steels, it is lower than that of classical deep drawing steels it has to replace. The low ductility of DP steels is attributed to damage development. Damage not only weakens the material but also reduces the ductility by formation of meso-cracks due to interacting micro defects. Damage in a material usually refers to presence of micro defects in the material. It is a known fact that plastic deformation induces damage in DP steels. Therefore damage development in these steels have to be included in the simulation of the forming process. In ductile metals, damage leads to crack initiation. A crack is anisotropic which makes damage anisotropic in nature. However, most researchers assume damage to be an isotropic phenomenon. For correct and accurate simulation results, damage shall be considered as anisotropic, especially if the results are used to determine the crack propagation direction. This paper presents an efficient plasticity induced anisotropic damage model to simulate complex failure mechanisms and accurately predict failure in macro-scale sheet forming processes. Anisotropy in damage can be categorized based on the cause which induces the anisotropy, i.e. the loading state and the material microstructure. According to the Load Induced Anisotropic Damage (LIAD) model, if the material is deformed in one direction then damage will be higher in this direction compared to the other two orthogonal directions, irrespective of the microstructure of the material. According to Material Induced Anisotropic Damage (MIAD) model, if there is an anisotropy in shape or distribution of the particles responsible for damage (hard second phase particles, inclusions or impurities) then the material will have different damage characteristics for different orientations in the sheet material. The LIAD part of the damage model is a modification of Lemaitre’s (ML) anisotropic damage model. Modifications are made for damage development under compression state and influence of strain rate on damage, and are presented in this paper. Viscoplastic regularization is used to avoid pathological mesh dependency. The MIAD part of the model is an extension of the LIAD model. Experimental evidence is given of the MIAD phenomenon in DP600 steel. The experimental analysis is carried out using tensile tests, optical strain measurement system (ARAMIS) and scanning electron microscopy. The extension to incorporate MIAD in the ML anisotropic damage model is presented in this paper as well. The paper concludes with a validation of the anisotropic damage model for different applications. The MIAD part of the model is validated by experimental cylindrical cup drawing wheras the LIAD part of the model is validated by the cross die drawing process.

Download Full-text

Advanced High Strength Steel Sheet Forming and Springback Simulation

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.97-101.200 ◽

2010 ◽

Vol 97-101 ◽

pp. 200-203 ◽

Cited By ~ 2

Author(s):

Ke Chen ◽

Jian Ping Lin ◽

Mao Kang Lv ◽

Li Ying Wang

Keyword(s):

High Strength Steel ◽

Yield Criterion ◽

Kinematic Hardening ◽

Sheet Material ◽

High Strength ◽

Material Model ◽

Sheet Forming ◽

Isotropic Hardening ◽

Advanced High Strength Steel ◽

Springback Prediction

With the increasing use of finite element analysis method in sheet forming simulations, springback predictions of advanced high strength steel (AHSS) sheet are still far from satisfactory precision. The main purpose of this paper was to provide a method for accurate springback prediction of AHSS sheet. Material model with Hill’48 anisotropic yield criterion and nonlinear isotropic/kinematic hardening rule were applied to take account the anisotropic yield behavior and the Bauschinger effect during forming processes. U-channel forming and springback simulation was performed using ABAQUS software. High strength DP600 sheet was investigated in this work. The simulation results obtained with the proposed material model agree well with the experimental results, which show a remarkable improvement of springback prediction compared with the commonly used isotropic hardening model.

Download Full-text

Anisotropic Damage Model for Concrete Affected by Alkali-Aggregate Reaction

International Journal of Damage Mechanics ◽

10.1177/1056789510386857 ◽

2010 ◽

Vol 20 (4) ◽

pp. 598-617 ◽

Cited By ~ 18

Author(s):

Claudia Comi ◽

Umberto Perego

Keyword(s):

Chemical Reaction ◽

Material Properties ◽

Damage Model ◽

Experimental Tests ◽

Anisotropic Damage ◽

Damage Development ◽

Two Phase ◽

Alkali Aggregate Reaction ◽

Significant Damage ◽

Strength And Stiffness

An anisotropic two-phase coupled chemo-thermo-damage model is proposed, for the simulation of the behavior of concrete affected by the alkali-aggregate reaction, which may create significant damage in existing concrete structures. The chemical reaction produces a gel expanding in the concrete pores, leading to macroscopic strength and stiffness deterioration in the concrete skeleton. The model is capable to account for the anisotropic damage development and consequent directional degradation of material properties. The model is validated against experimental tests taken from the literature.

Download Full-text

Predicting the damage development in epoxy resins using an anisotropic damage model

Polymer Engineering & Science ◽

10.1002/pen.25383 ◽

2020 ◽

Vol 60 (6) ◽

pp. 1324-1332

Author(s):

Jonas Maximilian Müller ◽

Nicolas Rozo Lopez ◽

Enzo Alexander Klein ◽

Christian Hopmann

Keyword(s):

Epoxy Resins ◽

Damage Model ◽

Anisotropic Damage ◽

Damage Development

Download Full-text

Validation of Modified Lemaitre’s Anisotropic Damage Model with the Cross Die Drawing Test

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.488-489.49 ◽

2011 ◽

Vol 488-489 ◽

pp. 49-52 ◽

Cited By ~ 1

Author(s):

M.S. Niazi ◽

H. H. Wisselink ◽

T. Meinders

Keyword(s):

Strain Rate ◽

Automotive Industry ◽

Damage Model ◽

Anisotropic Damage ◽

Rate Dependency ◽

Damage Models ◽

Rate Dependent ◽

Drawing Test ◽

Dp Steels ◽

The Cross

Dual Phase (DP) steels are widely replacing the traditional forming steels in automotive industry. Advanced damage models are required to accurately predict the formability of DP steels. In this work, Lemaitre’s anisotropic damage model has been slightly modified for sheet metal forming applications and for strain rate dependent materials. The damage evolution law is adapted to take into account the strain rate dependency and negative triaxialities. The damage parameters for pre-production DP600 steel were determined. The modified damage models (isotropic and anisotropic) were validated using the cross die drawing test. The anisotropic damage model predicts the crack direction more accurately.

Download Full-text

MITTAL DI-FORM T700, HF80Y100T

Alloy Digest ◽

10.31399/asm.ad.sa0561 ◽

2007 ◽

Vol 56 (2) ◽

Keyword(s):

Automotive Industry ◽

High Strength ◽

Martensite Phase ◽

Carbon Steels ◽

Ferrite Phase ◽

Dual Phase ◽

Low Carbon ◽

Advanced High Strength Steel ◽

Dp Steels ◽

Soft Ferrite

Abstract MITTAL DI-FORM T700 and HF80Y100T are low-carbon steels with a manganese and silicon composition. Dual-phase (DP) steels are one of the important advanced high-strength steel (AHSS) products developed for the automotive industry. Their microstructure typically consists of a soft ferrite phase with dispersed islands of a hard martensite phase. The martensite phase is substantially stronger than the ferrite phase. The DI-FORM grades exhibit low yield-to-tensile strengths, and the numeric designation in the name corresponds to the tensile strength. This datasheet provides information on microstructure and tensile properties as well as deformation and fatigue. It also includes information on forming. Filing Code: SA-561. Producer or source: Mittal Steel USA Flat Products.

Download Full-text

Effect of Rare Earth Ce on Deep Stamping Properties of High-Strength Interstitial-Free Steel Containing Phosphorus

Materials ◽

10.3390/ma13061473 ◽

2020 ◽

Vol 13 (6) ◽

pp. 1473

Author(s):

Hao Wang ◽

Yanping Bao ◽

Chengyi Duan ◽

Lu Lu ◽

Yan Liu ◽

...

Keyword(s):

Solid Solution ◽

Grain Size ◽

Rare Earth ◽

High Strength ◽

Rolling Process ◽

P Element ◽

Second Phase ◽

Strengthening Effect ◽

Interstitial Free ◽

If Steel

The influence of rare earth Ce on the deep stamping property of high-strength interstitial-free (IF) steel containing phosphorus was analyzed. After adding 120 kg ferrocerium alloy (Ce content is 10%) in the steel, the inclusion statistics and the two-dimensional morphology of the samples in the direction of 1/4 thickness of slab and each rolling process were observed and compared by scanning electron microscope (SEM). After the samples in each rolling process were treated by acid leaching, the three-dimensional morphology and components of the second phase precipitates were observed by SEM and energy dispersive spectrometer (EDS). The microstructure of the sample was observed by optical microscope, and the grain size was compared. Meanwhile, the content and strength of the favorable texture were analyzed by X-ray diffraction (XRD). Finally, the mechanical properties of the product were analyzed. The results showed that: (1) The combination of rare earth Ce with activity O and S in steel had lower Gibbs free energy, and it was easy to generate CeAlO3, Ce2O2S, and Ce2O3. The inclusions size was obviously reduced, but the number of inclusions was increased after adding rare earth. The morphology of inclusions changed from chain and strip to spherical. The size of rare earth inclusions was mostly about 2–5 μm, distributed and dispersed, and their elastic modulus was close to that of steel matrix, which was conducive to improving the structure continuity of steel. (2) The rare earth compound had a high melting point. As a heterogeneous nucleation point, the nucleation rate was increased and the solidification structure was refined. The grade of grain size of products was increased by 1.5 grades, which is helpful to improve the strength and plasticity of metal. (3) Rare earth Ce can inhibit the segregation of P element at the grain boundary and the precipitation of Fe(Nb+Ti)P phase. It can effectively increase the solid solution amount of P element in steel, improve the solid solution strengthening effect of P element in high-strength IF steel, and obtain a large proportion of {111} favorable texture, which is conducive to improving the stamping formability index r90 value.

Download Full-text

Finite Element Modeling of Damage Formation in Rubber-Toughened Polymer

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.297-300.1019 ◽

2005 ◽

Vol 297-300 ◽

pp. 1019-1024

Author(s):

Mitsugu Todo ◽

Yoshihiro Fukuya ◽

Seiya Hagihara ◽

Kazuo Arakawa

Keyword(s):

Finite Element ◽

Damage Zone ◽

Damage Model ◽

Crack Tip ◽

Optical Microscope ◽

Toughening Mechanism ◽

Element Analysis ◽

Zone Formation ◽

Macro Scale ◽

Rubber Toughened

Microscopic studies on the toughening mechanism of rubber-toughened PMMA (RTPMMA) were carried out using a polarizing optical microscope (POM) and a transmission electron microscope (TEM). POM result showed that in a typical RT-PMMA, a damage zone was developed in the vicinity of crack-tip, and therefore, it was considered that energy dissipation due to the damage zone development was the primary toughening mechanism. TEM result exhibited that the damage zone was a crowd of micro-crazes generated around rubber particles in the vicinity of notch-tip. Finite element analysis was then performed to simulate such damage formations in crack-tip region. Macro-scale and micro-scale models were developed to simulate damage zone formation and micro-crazing, respectively, with use of a damage model. It was shown that the damage model introduced was successfully applied to predict such kind of macro-damage and micro-craze formations.

Download Full-text

Microstructural Refinement in a Commercial Aluminum Alloy Processed by ECAP Using a Die Channel Angle of 110 Degrees

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1114.3 ◽

2015 ◽

Vol 1114 ◽

pp. 3-8

Author(s):

Nicolae Şerban ◽

Doina Răducanu ◽

Nicolae Ghiban ◽

Vasile Dănuţ Cojocaru

Keyword(s):

Grain Refinement ◽

Cross Section ◽

High Strength ◽

Secondary Phase ◽

Coarse Grained ◽

Metallographic Analysis ◽

Second Phase ◽

Channel Angle ◽

Ambient Temperatures ◽

Fine Grained

The properties of ultra-fine grained materials are superior to those of corresponding conventional coarse grained materials, being significantly improved as a result of grain refinement. Equal channel angular pressing (ECAP) is an efficient method for modifying the microstructure by refining grain size via severe plastic deformation (SPD) in producing ultra-fine grained materials (UFG) and nanomaterials (NM). The grain sizes produced by ECAP processing are typically in the submicrometer range and this leads to high strength at ambient temperatures. ECAP is performed by pressing test samples through a die containing two channels, equal in cross-section and intersecting at a certain angle. The billet experiences simple shear deformation at the intersection, without any precipitous change in the cross-section area because the die prevents lateral expansion and therefore the billet can be pressed more than once and it can be rotated around its pressing axis during subsequent passes. After ECAP significant grain refinement occurs together with dislocation strengthening, resulting in a considerable enhancement in the strength of the alloys. A commercial AlMgSi alloy (AA6063) was investigated in this study. The specimens were processed for a number of passes up to nine, using a die channel angle of 110°, applying the ECAP route BC. After ECAP, samples were cut from each specimen and prepared for metallographic analysis. The microstructure of the ECAP-ed and as-received material was investigated using optical (OLYMPUS – BX60M) and SEM microscopy (TESCAN VEGA II – XMU). It was determined that for the as-received material the microstructure shows a rough appearance, with large grains of dendritic or seaweed aspect and with a secondary phase at grain boundaries (continuous casting structure). For the ECAP processed samples, the microstructure shows a finished aspect, with refined, elongated grains, also with crumbled and uniformly distributed second phase particles after a typical ECAP texture.

Download Full-text

Cross-Ply Laminates under Static Three-Point Bending: A Numerical Development Model

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.498.42 ◽

2012 ◽

Vol 498 ◽

pp. 42-54 ◽

Cited By ~ 1

Author(s):

S. Benbelaid ◽

B. Bezzazi ◽

A. Bezazi

Keyword(s):

Numerical Model ◽

Damage Mechanics ◽

Progressive Failure ◽

Damage Model ◽

Continuum Damage Mechanics ◽

Failure Criteria ◽

Continuum Damage ◽

Damage Development ◽

Element Analysis ◽

Progressive Failure Analysis

This paper considers damage development mechanisms in cross-ply laminates using an accurate numerical model. Under static three points bending, two modes of damage progression in cross-ply laminates are predominated: transverse cracking and delamination. However, this second mode of damage is not accounted in our numerical model. After a general review of experimental approaches of observed behavior of laminates, the focus is laid on predicting laminate behavior based on continuum damage mechanics. In this study, a continuum damage model based on ply failure criteria is presented, which is initially proposed by Ladevèze. To reveal the effect of different stacking sequence of the laminate; such as thickness and the interior or exterior disposition of the 0° and 90° oriented layers in the laminate, an equivalent damage accumulation which cover all ply failure mechanisms has been predicted. However, the solution algorithm using finite element analysis which implements progressive failure analysis is summarized. The results of the numerical computation have been justified by the previous published experimental observations of the authors.

Download Full-text