An implicit unitless error and step‐size control method in integrating unified viscoplastic/creep ODE‐type constitutive equations

Cao, Jian; Lin, Jianguo; Dean, Trevor

doi:10.1002/nme.2112

Cited by 31 publications

(20 citation statements)

References 27 publications

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“…The unified viscoplastic constitutive equations were developed to predict flow stress and microstructure evolution for many types of metal materials [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. Recovery, recrystallization, grain size, and dislocation density were well described in the framework of the unified viscoplastic constitutive model.…”

Section: Constitutive Equations and Microstructural Model Of 21-4nmentioning

confidence: 99%

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Predicting the Microstructure of a Valve Head during the Hot Forging of Steel 21-4N

Huang

et al. 2018

Metals

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Abstract:Valve microstructure is important during hot forging. Austenitic 21-4N steel is often used in exhaust valves. In this study, the microstructure evolution of the forging valve process was predicted using the internal state variables (i.e., average grain size, recrystallized fraction, and dislocation density) modus for 21-4N. First, 21-4N was subjected to hot compression tests on a Gleeble-1500D and static grain growth tests in a heating furnace. A set of uniform viscoplastic constitutive equations was established based on experimental data. Next, the determined unified constitutive equations were conducted in DEFORM-3D, and the microstructure evolution of 21-4N during forging was calculated. Finally, the simulation results of grain size evolution were validated via experiments. Results showed good consistency between the simulations and experiments. Thus, the models adequately predicted the microstructure evolution.

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Section: Constitutive Equations and Microstructural Model Of 21-4nmentioning

confidence: 99%

“…The second term of Equation (9) describes the average grain size. Lin [37,38] defined two sub-objective functions on the basis of the logarithmic error between calculated values and experimental values. The following are the two sub-objective functions Equations (10) and (11):…”

Section: Constitutive Equations and Microstructural Model Of 21-4nmentioning

confidence: 99%

Predicting the Microstructure of a Valve Head during the Hot Forging of Steel 21-4N

Huang

et al. 2018

Metals

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“…(Lin et al, 2002;Lin and Liu, 2003). In those equations, hardening of a material during viscoplastic deformation is modelled according to the accumulation of plastic strain Cao et al, 2008). Recently dislocation-based hardening constitutive equations have been developed by in which the recovery of dislocations due to annealing and recrystallisation in hot forming conditions is included.…”

Section: Uniaxial Viscoplastic Damage Constitutive Equationsmentioning

confidence: 99%

Formability investigation using a new test design for hot stamping processes

Mohamed

Lin

Foster

et al. 2017

IJMPT

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Hot stamping is widely used in the forming of lightweight automotive panel components. The process optimisation requires knowledge of constitutive relations of work-piece material but assessment of formability of materials in hot stamping conditions is exceptionally challenging. A testing method and corresponding specimen design are developed in this paper for evaluating formability of materials in hot stamping conditions. A series of tests have been carried out for AA6082 aluminium alloy, at different forming rates and failure modes have been analysed. A set of stress-state dependent damage equations for AA6082 is introduced and this has been input into the FE code, ABAQUS. An FE model is developed and validated from the experimental 4 M. Mohamed et al.results. Failure modes at particular forming conditions are predicted and designed specimen shapes are optimised for different forming conditions. It is concluded that work-piece design is related to ductility for hot stamping conditions and recommendations for work-piece design are given.Keywords: testpiece design; hot stamping; AA6082; CDM model; formability; FE process modelling.Reference to this paper should be made as follows: Mohamed, M., Lin, J., Foster, A., Dean, T. and Dear, J. (2017)

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“…Evolutionary programming optimisation techniques, minimizing the residuals between the computed target values and experimental data, have been usually used to determine the model parameters [35]. The details of the optimisation method and the corresponding numerical procedure for this type of problem are described by Li et al [36], Lin et al [37,38], Cao et al [39,40] and Zhou et al [41]. Referring to the objective function developed by Cao and Lin [39], two sub-objective functions were defined as:…”

Section: Determination Of Model Parametersmentioning

confidence: 99%

Unified constitutive modelling for two-phase lamellar titanium alloys at hot forming conditions

Yang

Wang

et al. 2016

Manufacturing Rev.

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-In this paper, a set of mechanism based unified viscoplastic constitutive equations have been established for two-phase titanium alloys with initial lamellar microstructure, which models the softening mechanisms of the alloys in hot forming conditions. The dislocation density, rotation and globularization of lamellar a-phase and their effects on flow behaviour can also be modelled. The values of material constants in the equation set have been calibrated, according to stress-strain curves and globularization fractions of lamellar a-phase obtained from compression tests at a range of temperatures and strain rates, using a genetic algorithm (GA) based optimisation method. Based on the determined constitutive equations, flow stress and globularization evolution of Ti-17 and TA15 alloys at different temperatures and strain rates were predicted. Good agreements between the experimental and computed results were obtained.

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An implicit unitless error and step‐size control method in integrating unified viscoplastic/creep ODE‐type constitutive equations

Cited by 31 publications

References 27 publications

Predicting the Microstructure of a Valve Head during the Hot Forging of Steel 21-4N

Predicting the Microstructure of a Valve Head during the Hot Forging of Steel 21-4N

Formability investigation using a new test design for hot stamping processes

Unified constitutive modelling for two-phase lamellar titanium alloys at hot forming conditions

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