Application of a continuum damage mechanics (CDM)-based model for predicting formability of warm formed aluminium alloy

Bai, Qian; Mohamed, Mohamed S.; Shi, Zhusheng; Lin, Jianguo; Dean, T. A.

doi:10.1007/s00170-016-8853-4

Cited by 18 publications

(5 citation statements)

References 16 publications

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“…To summarize, a set of viscoplastic models were proposed emphasizing the combined impact of dislocations and precipitates for AA7075 alloy, as shown in Equation (19). To calibrate the material parameters based on the stress-strain curves derived by uniaxial hot stretching of the AA7075 alloy, they were classified into macroscopic state variables, such as strain rate and microscopic damage, grain size, dislocation density, and precipitateinduced damage [53,54]. The detailed calibration and optimization methods based on the genetic algorithm were described in our previous work [31].…”

Section: Parameter Calibrationmentioning

confidence: 99%

Uncovering Dislocation- and Precipitate-Induced Viscoplastic Damage in Al-Zn-Mg Alloy

et al. 2023

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The existing phenomenological theories of plastic forming of sheet metal lack the predictability of the influences of dislocations and precipitates on viscoplastic damage in Al-Zn-Mg alloys. This study examines the evolution of grain size that occurs when the Al-Zn-Mg alloy undergoes a hot deformation process, specifically concentrating on dynamic recrystallization (DRX). The uniaxial tensile tests are conducted at deformation temperatures ranging from 350 to 450 °C and strain rates of 0.01–1 s−1. The intragranular and intergranular dislocation configurations and their interactions with dynamic precipitates are revealed by transmission electron microscopy (TEM). In addition, the MgZn2 phase induces microvoid formation. Subsequently, an improved multiscale viscoplastic constitutive model is established that emphasizes the effect of precipitates and dislocations on the evolution of microvoid-based damage. Using a calibrated and validated micromechanical model, the simulation of hot-formed U-shaped parts is conducted through finite element (FE) analysis. During the hot U-forming process, the formation of defects is expected to have an impact on both the distribution of thickness and the level of damage. In particular, the damage accumulation rate is influenced by temperature and strain rate, and local thinning is caused by the damage evolution of U-shaped parts.

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Section: Parameter Calibrationmentioning

confidence: 99%

Uncovering Dislocation- and Precipitate-Induced Viscoplastic Damage in Al-Zn-Mg Alloy

et al. 2023

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“…The M-K model was adopted to predict FLCs at elevated temperatures for AA5083 by Zhang et al (2009) and for AA3003 by Abedrabbo et al (2006aAbedrabbo et al ( , 2006b. By contrast, the plane-stress CDM-based model of Lin et al (2014), in which a set of dislocation-based hardening constitutive equations and a damage variable was used, was developed purposely for predicting FLCs in sheet metals under hot stamping conditions and was successfully applied to the formability prediction for AA5754 in warm forming processes (Bai et al, 2016). A modification of this CDM-based model was adopted by Shao et al (2017) for the prediction of FLCs in AA6082 under hot stamping conditions.…”

Section: Introductionmentioning

confidence: 99%

“…By contrast, the plane-stress CDM-based model of Lin et al. (2014), in which a set of dislocation-based hardening constitutive equations and a damage variable was used, was developed purposely for predicting FLCs in sheet metals under hot stamping conditions and was successfully applied to the formability prediction for AA5754 in warm forming processes (Bai et al., 2016). A modification of this CDM-based model was adopted by Shao et al.…”

Section: Introductionmentioning

confidence: 99%

A CDM-based unified viscoplastic constitutive model of FLCs and FFLCs for boron steel under hot stamping conditions

Zhang

Shi

Yardley

et al. 2022

International Journal of Damage Mechanics

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Forming limit curves (FLCs), which are constructed using the limit strains at localised necking, are the most widely used tools for the evaluation of the formability of sheet metals. Fracture forming limit curves (FFLCs) are more recently developed, complementary tools for formability evaluation which are instead constructed using the limit strains at fracture. Since the formability depends strongly on forming conditions such as strain state, temperature and strain rate, models for predicting FLCs and FFLCs are essential for the optimisation and further application of hot forming processes in which these forming conditions vary significantly with both position and time. However, no model has so far been developed to predict FFLCs either alone or in conjunction with FLCs for sheet metals such as boron steel under hot stamping conditions. In this study, a set of unified viscoplastic constitutive equations for the prediction of both FLCs and FFLCs based on continuum damage mechanics (CDM) has been formulated from a set of recently developed constitutive equations for dislocation-based hardening, in combination with two novel coupled variables characterising the accumulated damage leading to localised necking and fracture. The novel variables take into account the effects of strain state, temperature and strain rate on the formability of sheet metals. The material constants in the CDM-based constitutive equations have been calibrated using experimental data comprising true stress-true strain curves and limit strains of a 22MnB5 boron steel obtained at a range of temperatures and strain rates. Investigation of the effect of varying selected parameters in the coupled damage variables on the resulting computed FLCs and FFLCs has demonstrated the flexibility of the model in enabling curves of different shapes and numerical values to be constructed. This indicates the potential of the CDM-based constitutive model for application to other materials for warm or hot stamping processes.

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“…Compared to ductile fracture modeling at isothermal conditions, the literature shows significantly fewer approaches for non-isothermal processes. Lin et al [ 27 ] introduced a Continuum Damage Mechanics (CDM) based model with temperature and strain rate effects to predict the formability at non-isothermal conditions which was successfully applied by Bai et al [ 28 ] for warm forming. Johnson and Cook [ 29 ] introduced a phenomenological fracture model for ballistic problems which takes into account the effects of stress state, strain rate and temperature.…”

Section: Introductionmentioning

confidence: 99%

A Generalized Stress State and Temperature Dependent Damage Indicator Framework for Ductile Failure Prediction in Heat-Assisted Forming Operations

Camberg

Erhart²,

Tröster

2021

Materials

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Heat-assisted forming processes are becoming increasingly important in the manufacturing of sheet metal parts for body-in-white applications. However, the non-isothermal nature of these processes leads to challenges in evaluating the forming limits, since established methods such as Forming Limit Curves (FLCs) only allow the assessment of critical forming strains for steady temperatures. For this reason, a temperature-dependent extension of the well-established GISSMO (Generalized Incremental Stress State Dependent Damage Model) fracture indicator framework is developed by the authors to predict forming failures under non-isothermal conditions. In this paper, a general approach to combine several isothermal FLCs within the temperature-extended GISSMO model into a temperature-dependent forming limit surface is investigated. The general capabilities of the model are tested in a coupled thermo-mechanical FEA using the example of warm forming of an AA5182-O sheet metal cross-die cup. The obtained results are then compared with state of the art of evaluation methods. By taking the strain and temperature path into account, GISSMO predicts greater drawing depths by up to 20% than established methods. In this way the forming and so the lightweight potential of sheet metal parts can by fully exploited. Moreover, the risk and locus of failure can be evaluated directly on the part geometry by a contour plot. An additional advantage of the GISSMO model is the applicability for low triaxialities as well as the possibility to predict the materials behavior beyond necking up to ductile fracture.

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Application of a continuum damage mechanics (CDM)-based model for predicting formability of warm formed aluminium alloy

Cited by 18 publications

References 16 publications

Uncovering Dislocation- and Precipitate-Induced Viscoplastic Damage in Al-Zn-Mg Alloy

Uncovering Dislocation- and Precipitate-Induced Viscoplastic Damage in Al-Zn-Mg Alloy

A CDM-based unified viscoplastic constitutive model of FLCs and FFLCs for boron steel under hot stamping conditions

A Generalized Stress State and Temperature Dependent Damage Indicator Framework for Ductile Failure Prediction in Heat-Assisted Forming Operations

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