A Method of Determining Unified Viscoplastic Constitutive Equations for Hot Forging Simulations

Politis, Nicholas J.; Politis, Denis J.; Davies, Catrin M.; Lin, Jianguo

doi:10.4028/www.scientific.net/kem.716.251

Cited by 2 publications

(1 citation statement)

References 16 publications

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“…This was achieved with a simplistic objective function, which is a 'worst case' scenario for the optimiser to solve, and thus faster solution times would be observed with improved objective functions. The paper presents a significant extension of the work performed by Politis et al 16 and consists of (i) the method of obtaining the experimental material properties, along with the experimental results; (ii) a description of the unified visco-plastic constitutive equations; (iii) a discussion of potential solver solutions; (iv) the solution method developed to determine the equation constants, along with the optimised constants, and solver performance data; and (v) an improved optimisation method utilising multiple solvers, and performance data.…”

Section: Introductionmentioning

confidence: 82%

Development of a computational optimisation system to determine constitutive equation constants for metal alloys

Politis

2017

Proceedings of the Institution of Mechanical Engineers, Part L:

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Simulations of metal forming processes typically use constitutive equations to describe material properties over a wide range of temperatures and strain rates. Classically, determining a set of values for the large number of constants present in more complex constitutive models presented great difficulty to researchers. In this paper, an algorithmic method of determining the constants of such constitutive equations is presented. The Genetic Algorithm implementation utilising MATLAB is described, and example fits to experimental data are presented. A study is performed to improve the performance of the method by combining the Genetic Algorithm and Particle Swarm optimisation methods into a hybrid algorithm and to exploit the inherent advantages of both methods of solution. Comparative performance between the GA-only and hybrid algorithm are presented, and it is found that such a Hybrid Solver is significantly more computationally efficient and produces more accurate parameter estimations.

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Section: Introductionmentioning

confidence: 82%

Development of a computational optimisation system to determine constitutive equation constants for metal alloys

Politis

2017

Proceedings of the Institution of Mechanical Engineers, Part L:

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Numerical and Experimental Study on Hot Forming by Partition Cooling of 38MnB5Nb

Liang

Wang

et al. 2022

Metals

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Tailored properties hot forming of 38MnB5Nb by partition cooling can be configured on-demand. A gradient distribution microstructural characteristic can be generated by undertaking an appropriate cooling-tempering process for the regions with different properties requirements before forming. A unified viscoplastic constitutive model coupled with the primary cooling temperature and related material constants is established based on genetic algorithm. Meanwhile, the use of the mixture of jet air and dry ice particles to cool the partition region is essential to achieve different primary cooling temperatures. In this paper, the inverse heat conduction problem is solved to obtain the relationship between the interfacial heat transfer coefficient and different cooling conditions in the partition cooling process. The U-shaped part is taken as an example to simulate the change of temperature, stress-strain, thickness, and spring-back in the process of partition cooling and tailored hot forming properties. The results show that the gradient microstructural characteristic formed by partition cooling has a great influence on the stress field distribution. The maximum stress of 345 MPa can be reached after complete pressure holding in the partition slow cooling tailored properties of the hot forming process. The maximum stress can reach 743 MPa in the partition fast cooling tailored properties of the hot forming process due to the relatively high deformation resistance of the tempered martensite at the bottom center. The maximum residual stress in the two processes after spring-back drops to 305 MPa and 545 MPa, respectively. The spring-back is small under the two processes, with a maximum spring back angle of no more than 1°.

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A Method of Determining Unified Viscoplastic Constitutive Equations for Hot Forging Simulations

Cited by 2 publications

References 16 publications

Development of a computational optimisation system to determine constitutive equation constants for metal alloys

Development of a computational optimisation system to determine constitutive equation constants for metal alloys

Numerical and Experimental Study on Hot Forming by Partition Cooling of 38MnB5Nb

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