Forming-induced damage and its effects on product properties

Tekkaya, A. Erman; Khalifa, Nooman Ben; Hering, Oliver; Meya, Rickmer; Myslicki, Sebastian; Walther, Frank

doi:10.1016/j.cirp.2017.04.113

Cited by 47 publications

(38 citation statements)

References 11 publications

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“…For the sake of comparison with the results in [1], the software Abaqus is used as the solver for the FEM problem. For the sake of comparison with the results in [1], the software Abaqus is used as the solver for the FEM problem.…”

Section: Numerical Implementationmentioning

confidence: 99%

“…Large triaxiality values are equivalent to a highly tensile oriented stress state, which in turn favours damage evolution, see [1]. subject to η(s) ≤ η crit with η = σ h σ vM and σ h = where U(s) is the current deformation with design s of the sheet and U pre the deformation of the sheet when no additional compressive forces are present.…”

Section: Numerical Implementationmentioning

confidence: 99%

“…In [1], elastomer bending is presented, where superposed stresses due to the reaction forces of the elastomer cushion lead to reduced damage growth. In [1], elastomer bending is presented, where superposed stresses due to the reaction forces of the elastomer cushion lead to reduced damage growth.…”

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confidence: 99%

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Load Optimisation for Air Bending in the Context of Damage Reduction

Guhr

Barthold

Meya

et al. 2019

Proc Appl Math and Mech

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Load optimisation applied to air bending is used to optimise the damage state in the formed component. In [1], elastomer bending is presented, where superposed stresses due to the reaction forces of the elastomer cushion lead to reduced damage growth. Replacing the elastomer cushion with compressive loads allows for optimisation of these loads such that the damage, estimated with the stress triaxiality, is reduced. The optimisation is accomplished with the commercial FEM-Software Abaqus as the solver for the mechanical problem where Sequential Quadratic Programming (SQP) is used within Matlab to generate improved loads.The results obtained in [1], where damage evolution in selected forming processes was investigated, show the possibilities of superimposing stresses in bending to yield lesser damaged components, while maintaining the same deformation and final shape. The disadvantage of the elastomer cushion, however, is the inhomogeneous triaxiality distribution and the impossibility to directly define the forces imposed by the elastomer. The objective of load optimisation is to generate loads which yield a reduced damage state and, to later on improve the elastomer cushion for a precise setup of the reaction forces. Theory of load optimizationThe main idea for load optimisation has been presented in e.g. [2]. There, the external loads f within the equilibrium condition of the finite element formulationcan be optimised to generate new improved loads for a given problem. For the optimisation, the external loads are replaced by polynomial functions, with the coefficients of the polynomial as the design variables for the optimisation. Numerical implementationThe main part of this work is the implementation of the optimisation framework. For the sake of comparison with the results in [1], the software Abaqus is used as the solver for the FEM problem. This allows for the use of the same material properties as well as the in-built contact formulations. With this in mind, the optimisation framework is built around Abaqus in order to allow mathematical optimisation. For the optimisation, Matlab is used with its solver quadprog for SQP. In order to transfer the data from the simulations for the optimisation within Matlab, the python library and interface provided by Abaqus are utilised.The problem is defined in the Complete Abaqus Environment (CAE) and includes the region for the objective function, the area for the side constraints and the nodes for the load application. The input file created this way can then be altered to allow for optimisation. The complete optimisation framework consists of the following steps:1. Run a structural analysis (Abaqus) for the material response of the problem with design variables s.2. Perturb design variable s i (Matlab) and calculate the structural response (Abaqus) and the numerical gradient for the corresponding design variable via finite differences.3. Use the objective functions, side constraints and gradients for SQP and generate a new design (Matlab).For the mathematical optimisa...

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Section: Numerical Implementationmentioning

confidence: 99%

Section: Numerical Implementationmentioning

confidence: 99%

mentioning

confidence: 99%

“…

…”

mentioning

confidence: 99%

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Load Optimisation for Air Bending in the Context of Damage Reduction

Guhr

Barthold

Meya

et al. 2019

Proc Appl Math and Mech

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“…Although fractures are important, there is a growing interest of the scientific community to study the appearance and evolution of damage in general, particularly in dual-phase steels [16][17][18], as it can lead to failure. Damage can affect the mechanical properties of a component under service loads [19]. Reduction of damage that can lead to central burst appearance in DP800 steel obtained by cold forward extrusion is investigated in this paper.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Induced Central Damage in Cold Extrusion of Dual-Phase Steel DP800 Using Double-Pass Dies

Amigo

Camacho

2017

Metals

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Advanced High Strength Steels (AHSS) are a promising family of materials for applications where a high strength-to-weight ratio is required. Central burst is a typical defect commonly found in parts formed by extrusion and it can be a serious problem for the in-service performance of the extrudate. The finite element method is a very useful tool to predict this type of internal defect. In this work, the software DEFORM-F2 has been used to choose the best configurations of multiple-pass dies, proposed as an alternative to single-pass extrusions in order to minimize the central damage that can lead to central burst in extruded parts of AHSS, particularly, the dual-phase steel DP800. It has been demonstrated that some geometrical configurations in double-pass dies lead to a minimum value of the central damage, much lower than the one obtained in single-pass extrusion. As a general rule, the position of the minimum damage leads to choosing higher values of the contacting length between partial reductions (L) for high die semiangles (α) and to lower values of the reduction in the first pass (R A ) for low total reductions (R T ). This methodology could be extended to find the best configurations for other outstanding materials.

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Damage Optimisation for Air Bending

Guhr

Barthold

2021

Proc Appl Math and Mech

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Load and shape optimisation are applied to the process of air bending to optimise the damage state in the formed component. The enhanced process of elastomer bending is optimised, which yields a reduced damage state due to the superimposed radial stresses in the critical area of the forming process. The optimisation presented here is twofold. First, the elastomer is replaced by nodal loads to generate optimised loads for a reduced damage state. Second, the elastomer itself is optimised via shape optimisation by adjusting the layer for two kinds of elastomer of varying stiffness. The optimisation is accomplished with the commercial FEM software Abaqus as the solver for the mechanical problem and Matlab is used for optimisation.

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Forming-induced damage and its effects on product properties

Cited by 47 publications

References 11 publications

Load Optimisation for Air Bending in the Context of Damage Reduction

Load Optimisation for Air Bending in the Context of Damage Reduction

Reduction of Induced Central Damage in Cold Extrusion of Dual-Phase Steel DP800 Using Double-Pass Dies

Damage Optimisation for Air Bending

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