Achtung:

Sie haben Javascript deaktiviert!
Sie haben versucht eine Funktion zu nutzen, die nur mit Javascript möglich ist. Um sämtliche Funktionalitäten unserer Internetseite zu nutzen, aktivieren Sie bitte Javascript in Ihrem Browser.

Bildinformationen anzeigen
Bildinformationen anzeigen
Bildinformationen anzeigen
SFB/Transregio 285

A05 - Schädigungsmodellierung für die Simulation mechanischer Fügeprozesse

Das Teilprojekt befasst sich mit der Modellierung und Simulation der Plastizität und Schädigung während mechanischer Fügeverfahren vor dem Hintergrund der angestrebten Wandlungsfähigkeit der Prozesse. Dazu werden einerseits Materialmodelle entwickelt, robust und effizient numerisch umgesetzt und experimentell validiert. Andererseits wird eine numerische Methode, die sogenannte Parametrische Finite Elemente Methode (PFEM), weiterentwickelt, die die effiziente Berechnung einer großen Anzahl verschiedener Prozessvarianten ermöglicht und damit das ideale Lösungsverfahren zur Simulation wandlungsfähiger Prozesse darstellt.

Verfahrensbedingt gehen die im TRR betrachteten mechanischen Fügeprozesse lokal mit sehr großen inelastischen Formänderungen einher. Dabei kommt es insbesondere zu einer Verkopplung von finiter Plastizität und Schädigung. Zum besseren Verständnis dieser während des Fügeprozesses auftretenden mesostrukturellen Phänomene sind geeignete Materialmodelle und ihre Verwendung in der Prozesssimulation unabdingbar. Die Entwicklung dieser Materialmodelle und ihre Anwendung zur virtuellen Optimierung der Prozessführung stellen Schwerpunkte dieses Projekts dar.

Des Weiteren zeichnen sich die betrachteten mechanischen Fügeprozesse, wie Clinchen oder Stanznieten, durch hohe Anforderungen an die Wandlungsfähigkeit aus. Zielgerichtete Änderungen innerhalb der Prozesskette – des Halbzeugs, der Fügestelle oder des Fügeprozesses – sollen möglich sein. Die Prozesssimulation sollte diesen Anforderungen an die Wandlungsfähigkeit Rechnung tragen und solche Variationen idealerweise von Beginn an berücksichtigen. Daraus ergibt sich der zweite Schwerpunkt des vorliegenden Projekts: Die PFEM wird um Plastizität und Schädigung erweitert und zur Simulation mechanischer Fügeprozesse verwendet. Neben den üblichen physikalischen Koordinaten, die den Raum diskretisieren, werden in der PFEM zusätzliche parametrische Koordinaten eingeführt, die einen oder mehrere geometrische oder werkstoffliche Parameter der Fügestelle repräsentieren. Die Lösung dieses höherdimensionalen Problems liefert simultan und sehr effizient die Lösungen für kontinuierliche Variationen (anstatt einer sehr aufwändigen diskreten Abtastung) dieser Parameter und erlaubt somit einen direkten Vergleich verschiedener Prozessvarianten im Sinne der Wandlungsfähigkeit.

Die zentralen Fragestellungen im TP A05 sind somit zusammenfassend (i) die physikalisch nichtlineare und geometrisch exakte Materialmodellierung von verkoppelter Plastizität und Schädigung, (ii) deren physikalisch motivierte Regularisierung und (iii) die numerische Umsetzung der Modelle für die Prozesssimulation im Rahmen der PFEM, um der angestrebten Wandlungsfähigkeit der Fügeprozesse Rechnung zu tragen.

Veröffentlichungen


Liste im Research Information System öffnen

Inverse parameter identification of an anisotropic plasticity model for sheet metal

J. Friedlein, S. Wituschek, M. Lechner, J. Mergheim, P. Steinmann, IOP Conference Series: Materials Science and Engineering (2021), 1157, pp. 012004

The increasing economic and ecological demands on the mobility sector require efforts to reduce resource consumption in both the production and utilization phases. The use of lightweight construction technologies can save material and increase energy efficiency during operation. Multi-material systems consisting of different materials and geometries are used to achieve weight reduction. Since conventional joining processes reach their limits in the connection of these components, new methods and technologies are necessary in order to be able to react versatilely to varying process and disturbance variables. For fundamental investigations of new possibilities in joining technology, numerical investigations are helpful to identify process parameters. To generate valid results, robust and efficient material models are developed which are adapted to the requirements of versatile joining technologies, for instance to the high plastic strains associated with self-piercing riveting. To describe the inherent strain-induced plastic orthotropy of sheet metal an anisotropic Hill-plasticity model is formulated. Tensile tests for different sheet orientations are conducted both experimentally and numerically to adjust the anisotropic material parameters by inverse parameter identification for aluminium EN AW-6014 and steel HCT590X. Then, the layer compression test is used to validate the model and the previously identified parameters.


Stochastic local FEM for computational homogenization of heterogeneous materials exhibiting large plastic deformations

D. Pivovarov, J. Mergheim, K. Willner, P. Steinmann, Computational Mechanics (2021)

Computational homogenization is a powerful tool allowing to obtain homogenized properties of materials on the macroscale from simulations of the underlying microstructure. The response of the microstructure is, however, strongly affected by variations in the microstructure geometry. In particular, we consider heterogeneous materials with randomly distributed non-overlapping inclusions, which radii are also random. In this work we extend the earlier proposed non-deterministic computational homogenization framework to plastic materials, thereby increasing the model versatility and overall realism. We apply novel soft periodic boundary conditions and estimate their effect in case of non-periodic material microstructures. We study macroscopic plasticity signatures like the macroscopic von-Mises stress and make useful conclusions for further constitutive modeling. Simulations demonstrate the effect of the novel boundary conditions, which significantly differ from the standard periodic boundary conditions, and the large influence of parameter variations and hence the importance of the stochastic modeling.


Anisotropic plasticity‐damage material model for sheet metal — Regularised single surface formulation

J. Friedlein, J. Mergheim, P. Steinmann, PAMM (2021), 21

Sheet metal forming as well as mechanical joining demand increasingly accurate and efficient material modelling to capture large deformations, the inherent sheet orthotropy and even process-induced damage, which is expected to be influential. To account for large strains the additive logarithmic strain space is utilised that enables a straightforward incorporation of plastic anisotropy, herein modelled by a Hill48 yield function. A gradient-enhancement is used to equip the ductile damage model with an internal length scale curing the damage-induced localisation. An affine combination of the local and non-local softening variable is derived enabling a more efficient single surface formulation for the regularised plasticity-damage material model.


A finite plasticity gradient-damage model for sheet metals during forming and clinching

J. Friedlein, J. Mergheim, P. Steinmann, Key Engineering Materials (2021), 883 KEM, pp. 57

In recent years, clinching has gathered popularity to join sheets of different materials in industrial applications. The manufacturing process has some advantages, as reduced joining time, reduced costs, and the joints show good fatigue properties. To ensure the joint strength, reliable simulations of the material behaviour accounting for process-induced damage are expected to be beneficial to obtain credible values for the ultimate joint strength and its fatigue limit. A finite plasticity gradient-damage material model is outlined to describe the plastic and damage evolutions during the forming of sheet metals, later applied to clinching. The utilised gradient-enhancement cures the damage-induced localisation by introducing a global damage variable as an additional finite element field. Both, plasticity and damage are strongly coupled, but can, due to a dual-surface approach, evolve independently. The ability of the material model to predict damage in strongly deformed sheets, its flexibility and its regularization properties are illustrated by numerical examples.


Observations on additive plasticity in the logarithmic strain space at excessive strains

J. Friedlein, J. Mergheim, P. Steinmann, International Journal of Solids and Structures (2022), 239-240, pp. 111416

Additive plasticity in the logarithmic strain space is compared to multiplicative plasticity for various loading cases including coaxial and non-coaxial plastic deformations. Even though both finite plasticity approaches are based on total Lagrangian descriptions, the former is popular due to its inherent similarity to the infinitesimal theory and its easy extensibility. However, since its introduction several limitations of additive plasticity in the logarithmic strain space have been discovered. In this study, these problems such as stress rotation and softening are considered, revealing that fundamental differences compared to multiplicative plasticity occur for non-coaxial plastic deformations. We focus in particular on the observed softer response of the additive based approach, which is analysed in depth using three numerical examples including two well-known benchmarks for finite plasticity. By means of these finite element simulations the softer and possibly even localising response of additive plasticity in the logarithmic strain space is confirmed.


A Review on the Modeling of the Clinching Process Chain - Part I: Design Phase

B. Schramm, S. Martin, C. Steinfelder, C.R. Bielak, A. Brosius, G. Meschut, T. Tröster, T. Wallmersperger, J. Mergheim, Journal of Advanced Joining Processes (2022), 6, 100133

DOI


A Review on the Modeling of the Clinching Process Chain - Part II: Joining Process

B. Schramm, J. Friedlein, B. Gröger, C.R. Bielak, M. Bobbert, M. Gude, G. Meschut, T. Wallmersperger, J. Mergheim, Journal of Advanced Joining Processes (2022), 100134

DOI


A Review on the Modeling of the Clinching Process Chain - Part III: Operational Phase

B. Schramm, S. Harzheim, D. Weiß, T.D. Joy, M. Hofmann, J. Mergheim, T. Wallmersperger, Journal of Advanced Joining Processes (2022), 100135

DOI


Liste im Research Information System öffnen

Kontakt

Prof. Dr.-Ing Paul Steinmann

Sonderforschungsbereich Transregio 285

Teilprojekt A05

Paul Steinmann
Telefon:
+49 9131 8528501

Kontakt

Prof. Dr.-Ing. Julia Mergheim

Sonderforschungsbereich Transregio 285

Teilprojekt A05

Julia Mergheim
Telefon:
+49 9131 8528505

Kontakt

M. Sc. Johannes Friedlein

Sonderforschungsbereich Transregio 285

Teilprojekt A05

Johannes Friedlein
Telefon:
+49 9131 85 64400