Material models for the thermoplastic material behaviour of a dual-phase steel on a microscopic and a macroscopic length scale

Zeller, Sebastian; Baldrich, Martina; Gerstein, Gregory; Nürnberger, Florian; Löhnert, Stefan; Maier, Hans Jürgen; Wriggers, Peter

doi:10.1016/j.jmps.2019.04.012

Cited by 6 publications

(6 citation statements)

References 75 publications

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“…Several factors come into play to create hurdles during slip activities, i.e., impurity atoms, dislocation structures and atomic lattices, etc. All these entities define the limit to initiate plastic deformation [1] [5]. For instance, τ α g = τ α ρ + τ α x + τ α i , is a sum of resistances to dislocations which defines the yield stress.…”

Section: Crystal Plasticitymentioning

confidence: 99%

“…Crystal plasticity is a micromechanical material model that can be used to perform simulations of metallic materials. To take into account the specific material behaviour at the local material points in the context of finite element simulations of representative volume elements (RVE), constitutive equations are solved at each material point inside the RVE [1]. In our current project, a dislocation density-based material model is proposed.…”

Section: Introductionmentioning

confidence: 99%

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Material modeling of ferritic steel on microscopic length scale under cyclic loading

Ahmed

Löhnert

Wriggers

2021

Proc Appl Math and Mech

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A material model for the polycrystalline microstructure of formable steels is developed to determine the residual stress state resulting from incompatible plastic deformation of individual grains under non-monotonic loading. The glide of mobile dislocations on a specific slip system mainly governs the shear rates. During the movement, dislocations experience several types of resistance. The existing immobile dislocation structures on non-parallel slip planes reduce the slip activities. This is reflected in a nonlinear isotropic hardening criterion. Furthermore, piled up dislocations on parallel slip planes also create hindrance to mobile dislocations. This effect creates residual stresses within the material which are taken into account by an additional kinematic hardening law. Residual stresses play a crucial role as well, especially during cyclic loading. Both, nonlinear isotropic and kinematic hardening criteria can define the plastic character of ferritic steel under non-monotonic loadings.

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Section: Crystal Plasticitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Material modeling of ferritic steel on microscopic length scale under cyclic loading

Ahmed

Löhnert

Wriggers

2021

Proc Appl Math and Mech

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“…This work can be classified in the group of dislocation density based crystal plasticity in a continuum mechanics framework. The model for ferrite developed in [4] is extended to capture the characteristic mechanisms occurring in aluminium, ferrite and pearlite on a microscopic scale.…”

Section: Intermetallic Phasesmentioning

confidence: 99%

“…During plastic deformation, the dislocation structure changes due to the elementary processes of multiplication and annihilation. The increase in dislocation density by multiplication can be traced back to the expansion of dislocation loops (see [4]). An annihilation process that decreases the dislocation density may become possible when a dislocation (of screw or edge character) is pinned by an obstacle and another dislocation of same character but opposite sign approaches.…”

Section: Evolution Equation For the Dislocation Densitiesmentioning

confidence: 99%

“…An annihilation process that decreases the dislocation density may become possible when a dislocation (of screw or edge character) is pinned by an obstacle and another dislocation of same character but opposite sign approaches. If the distance between the two dislocations is not larger than a critical value, the obstacle can be overcome due to an attractive stress field around the two dislocations and they annihilate each other [4,6].…”

Section: Evolution Equation For the Dislocation Densitiesmentioning

confidence: 99%

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Developing a model for the microscopic material behaviour of a tailored formed joining zone of an aluminium‐steel hybrid solid component

Baldrich

Löhnert

Wriggers

2018

Proc Appl Math and Mech

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Tailored Forming is a complex process joining two materials before forming. Especially the joining zone of the hybrid solid component is a possible weakness. Hence, our goal is to predict and adjust the thermomechanical material behaviour of the joining zone during and after the tailored forming process. The hybrid solid components studied in this work are composed of the aluminium alloy EN AW-6082 and the steel 20MnCr5. Metallurgical investigations on both materials show a polycrystalline microstructure. In the steel component, the two constituents ferrite and pearlite can be found with nearly the same volume fraction and randomly distributed grains. Furthermore, between the two bulk materials aluminium and steel, a thin layer of brittle intermetallic phases can be observed. In this work, the intermetallic phases are considered to behave purely thermoelastic, whereas the material model for aluminium, ferrite and pearlite represents thermoplastic material behaviour. We present the dislocation density based models for the thermoplastic materials formulated in a continuum mechanics framework. Thereby, different mechanisms of annihilation contributing to the evolution equation for the internal variables will be on focus.In order to investigate new ways to produce light weight and load-adjusted hybrid solid components, a process chain is developed in which two different materials are joined before being formed. During this so-called tailored forming process, one or more intermetallic phases evolve between the base materials aluminium and steel. Consisting of the five phases aluminium, ferrite, pearlite and two intermetallic phases with significantly different material properties, the joining zone might loose its load-bearing capacity due to crack initiation and propagation as a result of high mechanical stresses. To prevent the hybrid solid component from damage and failure, our goal is to understand, predict and adjust the material properties and the thermomechanical behaviour of the joining zone. Therefore, different micromechanically motivated material models are formulated. Intermetallic phasesIntermetallic phases that form between aluminium and steel mainly can be determined to be a dominant orthorhombic Al 5 Fe 2phase and to a much smaller extend the monoclinic Al 3 Fe-phase [1]. These brittle intermetallic phases are unfavourable with regard to the thermomechanical properties of the hybrid part. As a consequence, to achieve a high mechanical strength of the hybrid solid component, the aim is to keep the layer of intermetallic phases as thin as possible [1]. a) b) 10

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Multilevel Material Modeling to Study Plastic Deformation for Sheet-Bulk Metal Forming Under Different Loading Histories

Ahmed

Lyu

Löhnert

et al. 2020

Lecture Notes in Production Engineering

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Material models for the thermoplastic material behaviour of a dual-phase steel on a microscopic and a macroscopic length scale

Cited by 6 publications

References 75 publications

Material modeling of ferritic steel on microscopic length scale under cyclic loading

Material modeling of ferritic steel on microscopic length scale under cyclic loading

Developing a model for the microscopic material behaviour of a tailored formed joining zone of an aluminium‐steel hybrid solid component

Multilevel Material Modeling to Study Plastic Deformation for Sheet-Bulk Metal Forming Under Different Loading Histories

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