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1

Prediction of forming limits and microstructural evolution during warm stretch forming of DP590 steel

Pandre Sandeep, Morchhale Ayush, Kotkunde Nitin, Singh Swadesh Kumar, Ravindran Sujith

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

397--419

EN

Dual-phase (DP) steel has an excellent blend of various mechanical properties; hence it is used immensely in the automotive industries. It is challenging to form high strength DP steel into desirable complex shapes because of their limited formability at room temperature conditions. One of the proven alternatives is warm/hot forming. In-detail investigation of forming limits over DP590 steel has been carried out in present work. Firstly, various constitutive models and yield criteria have been formulated for DP steel at different temperatures and strain rates. The modified Arrhenius (m-A) constitutive model and Barlat 1989 yielding function displayed the best prediction of flow stress and anisotropic yielding behavior, respectively. The experimental forming limits (FLD) were evaluated at 300, 473 and 673 K temperatures using Nakazima tests. The forming limits of the material are improved by approximately 24% on increasing the temperature from 300 to 673 K. The textural analysis of the deformed surface has been done using electron back scattered diffraction (EBSD) studies, and γ fibers are found to be responsible for improvement in the formability of the material. Additionally, Marciniak and Kuczynski (MK) model was used to predict the theoretical FLD using all the possible combinations of constitutive models and yield criteria. Finally, the m-A constitutive model, along with Barlat 1989 yielding function has shown the best prediction for forming limits at all the temperatures. The finite element study has also been performed using mentioned material models for accurate prediction of dome height, surface strain and thickness distribution across the specimens.

2

A new strain based rectangular finite element with drilling rotation for linear and nonlinear analysis

Rebiai C., Belounar L.

Archives of Civil and Mechanical Engineering

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2013

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Vol. 13, no. 1

72--81

EN

In this paper a new membrane finite element for linear and materially nonlinear analysis is developed. The displacements field of this element has been developed by the use of the strain based approach, and it is based on the assumed functions for the various components of strain which satisfy the compatibility equation. This rectangular finite element has the three degrees of freedom at each of the four corner nodes (the two translations and the in-plane rotation) and the displacement functions of the developed element satisfy the exact representation of the rigid body modes. For elastoplastic analysis, Von Mises, Tresca and Mohr–Coulomb yield criteria are adopted, and both initial stress and initial strain methods are employed. Numerical experiments in both linear and nonlinear analysis have been conducted to assess accuracy and reliability of the developed element compared to the theoretical results and other membrane finite elements.

3

Wyznaczanie parametrów modeli ściśliwych materiałów plastycznych

Okoński S.

Archiwum Odlewnictwa

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2006

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R. 6, nr 21/2

103-108

PL

Przedstawiono metodykę określania stałych i funkcji materiałowych wchodzących do warunków plastyczności ściśliwych materiałów plastycznych z izotropowym wzmocnieniem. Podano przykładowe wartości tych parametrów dla 3 gatunków spieków metali (ASC100.29, Distaloy Cu i PNC-60).

EN

Methods of estimation of constitutive parameters for the yield conditions for plastic compressible materials with isotropic hardening have been elaborated. The values of these parameters for sintered metals (Distaloy Cu, ASC100.29 and PNC-60) have been presented.

4

Coercive limits for a subclass of monotonne constitutive equations in the theory of inelastic material behaviour of metals

Chełmiński Krzysztof

Matematyka Stosowana : matematyka dla społeczeństwa

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1997

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Nr 40

41--81

EN

We prove existence and uniqueness of strong global in tme solution for a subclass of monotone constitutive equations in the theory of inelastic material behaviour of metals without the coercivity assumption for the free energy function. We approximate noncoercive models by a sequence of coercive problems and prove the convergence result.