A New Modular Material Model for the Design of Light Weight Structures in Automotive Engineering with respect to Crashworthiness

Transcription

1 2 nd European HyperWorks Technology Conference 2008 Strasbourg Septeber 30 th October 1 st, 2008 A New Modular Material Model for the Design of Light Weight Structures in Autootive Engineering with respect to Crashworthiness G. Oberhofer 2, M. Franzen 1, A. Bach 1, H. Gese 2, H. Lanzerath 1 1 Ford Forschungszentru Aachen, Suesterfeldstrasse 200, D Aachen, Gerany 2 Matfe Partnerschaft Dr. Gese & Oberhofer, Nederlingerstr. 1, München, Gerany 1 H. Lanzerath

2 About R&A at Ford Motor Copany in Europe Ford Forschungszentru Aachen GbH founded in 1994 Managing Director: Dr. Charles Wu R&A FoE: 250 eployees R&A FNA: 900 eployees (Dearborn, Mi.) Project co-ordination with all FMC brands 2 H. Lanzerath

3 About 3 H. Lanzerath

4 Content of Presentation o Mechanical Properties of Materials o Material Modeling in Crash Siulation o User Material Model MF_GenYld+CrachFEM o Exaples o Discussion and Outlook 4 H. Lanzerath

5 Mechanical Properties of Materials Microstructure of Metallic Materials (Crystal Structure) 12 equivalent gliding planes => very good forability energetic different gliding planes => good forability Few gliding planes => liited forability at RT Aluiniu γ-iron (Austenite) α-iron (Ferrite) Magnesiu Titaniu 5 H. Lanzerath

6 Mechanical Properties of Materials Mesostructure of Metallic Materials (Texture) Wrought alloy Wrought alloy with texture Dendritic cast structure with Eutectic Hot-rolled sheet (re-crystallized structure) Cold-rolled sheet Extrusion profile Al-Casting Mg-Casting 6 H. Lanzerath

7 Mechanical Properties of aterials Daage and Failure of Metallic Materials 7 H. Lanzerath

8 Mechanical Properties of Materials Daage and Failure of Polyeric Materials Shear band foration Loading Direction Loading Direction Crazing Shear band foration Crazing Shear Shear band foration and crazing dependent on the state of stress for PMMA (Model Sternstein) Source: M. Junginger: Charakterisierung und Modellierung unverstärkter theroplastischer Kunststoffe zur nuerischen Siulation von Crashvorgängen, Dissertation a Fraunhofer-Institut für Kurzzeitdynaik (Ernst-Mach-Institut), Schriftenreihe Forschungsergebnisse aus der Kurzzeitdynaik, Heft Nr. 3, H. Lanzerath

9 Mechanical Properties of Materials Anisotropic Hardening of Polyers von Mises equivalent stress [MPa] Copression Copacting of olecule chains hoogeneous initial state Shear Sliding of olecule chains Tension Orientation of olecule chains von Mises equivalent strain [-] Source: M. Junginger: Charakterisierung und Modellierung unverstärkter theroplastischer Kunststoffe zur nuerischen Siulation von Crashvorgängen, Dissertation a Fraunhofer-Institut für Kurzzeitdynaik (Ernst-Mach-Institut), Schriftenreihe Forschungsergebnisse aus der Kurzzeitdynaik, Heft Nr. 3, H. Lanzerath

10 Content of Presentation o Mechanical Properties of Materials o Material Modeling in Crash Siulation o User Material Model MF_GenYld+CrachFEM o Exaples o Discussion and Outlook 10 H. Lanzerath

11 Material Modeling in Crash Siulation Modeling of Elasto-Viscoplastic Material Behavior a b c d The flow stress curve is derived fro uniaxial tension Extrapolation with analytical hardening law a b c d 11 H. Lanzerath

12 Material Modeling in Crash Siulation Elasto-Plastic Material Model on Macroscopic Level (Yield Locus, Flow Potential) Stress Yield Locus v. Mises Yield Locus 12 H. Lanzerath

13 Material Modeling in Crash Siulation Elasto-Plastic Material Model on Macroscopic Level (Yield Locus, Flow Potential) Flow Potential Flow potential for the plane stress state 13 H. Lanzerath

14 Material Modeling in Crash Siulation Elasto-Plastic Material Model on Macroscopic Level (Yield Locus, Flow Potential) Orthotropic yield loci for textured aluinu extrusion profiles Barlat et al von Mises 0,50 y 0,25 0,00-0,50 0,00 0,50 x -0,25 extrusion dir. -0,50 14 H. Lanzerath

15 Material Modeling in Crash Siulation Engineering Failure Criteria for Metallic Materials a b c d Total elongation fro tensile tests: a b c based on coplete easureent length deforation is localized in the diffusenecking or localized necking beyond unifor elongation no useful easure for the ductility! Cross-section reduction at fracture: d first qualitative easure for the ductility of the aterial however, stress state is not constant at the fracture location value cannot be used for a fracture odel 15 H. Lanzerath

16 Material Modeling in Crash Siulation Sheet Instability Ductile fracture Shear fracture Localized neck Failure odes depend on: Material Loading situation (state of stress / strain, strain rate) Process history (e.g. pre-strain, heat treatent,...) 16 H. Lanzerath

17 Content of Presentation o Mechanical Properties of Materials o Material Modeling in Crash Siulation o User Material Model MF_GenYld+CrachFEM o Exaples o Discussion and Outlook 17 H. Lanzerath

18 Features of MF_GenYld + CrachFEM Isotropic, kineatic and anisotropic hardening Prediction of local necking of etal sheets with Crach Versatile odeling of stress and strain anisotropy Prediction of ductile fracture with noral and shear fracture odes 18 H. Lanzerath

19 MF_GenYld Modular cobination of yield loci and hardening odels 19 H. Lanzerath

20 Standard hardening odel: isotropic yield locus based on equivalent stress and hardening curves for uniaxial tension MF_GenYld: allows an anisotropic evolution of the yield locus for biaxial tension, uniaxial copression, biaxial copression and shear. MF_GenYld Modeling of anisotropic hardening hardening of polyers and soe etallic aterials (austenitic steel and agnesiu sheets) are dependent on the stress state 20 H. Lanzerath

21 CrachFEM Coprehensive odel for aterial failure 21 H. Lanzerath

22 CrachFEM - Prediction of Localized Necking The Crach algorith predicts local instability under tension. The neck, i.e. a zone with an initial iperfection d, is evaluated in the direction of the first principal strain γ. Crach requires the following data: plastic anisotropy (Hill 1948) total hardening (Swift) kineatic hardening (Backhaus) strain rate sensitivity initial inhoogeneity d Instability prediction is cobined with a esh size-independent odel for post-critical elongation. 22 H. Lanzerath

23 CrachFEM Criteria for ductile noral fracture and ductile shear fracture Integral Daage Accuulation CrachFEM can odel failure under: ductile noral fracture d and ductile shear fracture s. eq 0 d eq eq ( η) = 1 Fracture is described by curves of fracture strain over the stress state Linear strain paths: This is the exact fracture criterion Non-linear strain paths: can be accounted for by using an integral failure criterion according to Kologorov integral daage accuulation with tensorial description of daage is also included 23 H. Lanzerath

24 MF_GenYld + CrachFEM and coercial FE code RADIOSS Coupling of user aterial odel and RADIOSS Explicit FE Progra MF_GenYld + CrachFEM RADIOSS LS-DYNA PaStap/Crash ABAQUS/Explicit... Interface shared or static objects MF_GenYld plastic hardening odules plastic orthotropy (yield loci) anisotropic hardening CrachFEM prediction of local necking for shells prediction of ductile noral/shear fracture Most coercial explicit FE codes ake the inclusion of user aterial odels easy by providing a shared object interface. 24 H. Lanzerath

25 Material Models for Crash Siulation Material Metals Non-Fiber Reinforced Polyers Elasticity Yield Surface 2 linear isotropic 1 2 linear isotropic 1 Plasticity Hardening Rule pl /s 20 1/s 250 1/s pl. Failure Onset of failure 2 = f & 1, 1 = f, & DF 2 τ ax = f & 3,, Necking SF = f, & DF 2 τ ax = f & 3,, SF Crack Propagation?? Short Fiber Reinforced Polyers linear orthotropic 2 1 pl. = f, & 2, γ DF τ ax = f,, & 3, γ SF? 25 H. Lanzerath

26 Content of Presentation o Mechanical Properties of Materials o Material Modeling in Crash Siulation o User Material Model MF_GenYld+CrachFEM o Exaples o Discussion and Outlook 26 H. Lanzerath

27 Material Models for Crash Siulation Material Metals Non-Fiber Reinforced Polyers Elasticity Yield Surface 2 linear isotropic 1 2 linear isotropic 1 Plasticity Hardening Rule pl /s 20 1/s 250 1/s pl. Failure Onset of failure 2 = f & 1, 1 = f, & DF 2 τ ax = f & 3,, Necking SF = f, & DF 2 τ ax = f & 3,, SF Crack Propagation?? Short Fiber Reinforced Polyers linear orthotropic 2 1 pl. = f, & 2, γ DF τ ax = f,, & 3, γ SF? 27 H. Lanzerath

28 Exaple UHSS Grade 3-Point Bending of UHSS Profile Failure Siulation Force [ kn ] INST Displaceent [ ] experient SIM_NF SIM_SF SIM_INST SF NF instability (INST) ductile noral fracture (NF) ductile shear fracture (SF) 28 H. Lanzerath

29 Exaple Magnesiu 3-Point Bending of Magnesiu Profile Failure Siulation & Test Experient* CrachFEM Isotropic Force [kn] Isotropic v. Mises yield locus Experient* RADIOSS_MF_GenYld+CrachFEM Displaceent [] *Source: ScienceDirect 2006; Cato Doru (SINTEF) 29 H. Lanzerath

30 Material Models for Crash Siulation Material Metals Non-Fiber Reinforced Polyers Elasticity Yield Surface 2 linear isotropic 1 2 linear isotropic 1 Plasticity Hardening Rule pl /s 20 1/s 250 1/s pl. Failure Onset of failure 2 = f & 1, 1 = f, & DF 2 τ ax = f & 3,, Necking SF = f, & DF 2 τ ax = f & 3,, SF Crack Propagation?? Short Fiber Reinforced Polyers linear orthotropic 2 1 pl. = f, & 2, γ DF τ ax = f,, & 3, γ SF? 30 H. Lanzerath

31 Exaple Non-Fiber Reinforced Polyers Erichsen Test of Polyer Disk Failure Siulation and Test Material PPT15+EPDM Isotropic v. Mises yield locus Experient 2.5 Force [kn] [ Experient RADIOSS_MF_GenYld+CrachFEM Displaceent [] Physical Tests Siulation Bi-Axial tension is correctly represented including fracture tie and ode Standard aterial odel can neither account for the asyetry nor fracture => Material odel shows significant advantage over standard ethod! 31 H. Lanzerath

32 Exaple Non-Fiber Reinforced Polyers Deforation Test of Polyer Interior Attachent Point Material PPT20 RADIOSS_MF_GenYld+CrachFEM Experient Force [kn] [ 1.0 Isotropic v. Mises yield locus 0.5 Physical Tests Displaceent [] Maxiu force is correctly displayed by new aterial odel Energy absorption of new aterial odel is uch closer to physical test results => Material odel shows significant advantage over standard ethod! 32 H. Lanzerath

33 Material Models for Crash Siulation Material Metals Non-Fiber Reinforced Polyers Elasticity Yield Surface 2 linear isotropic 1 2 linear isotropic 1 Plasticity Hardening Rule pl /s 20 1/s 250 1/s pl. Failure Onset of failure 2 = f & 1, 1 = f, & DF 2 τ ax = f & 3,, Necking SF = f, & DF 2 τ ax = f & 3,, SF Crack Propagation?? Short Fiber Reinforced Polyers linear orthotropic 2 1 pl. = f, & 2, γ DF τ ax = f,, & 3, γ SF? 33 H. Lanzerath

34 Content of Presentation o Mechanical Properties of Materials o Material Modeling in Crash Siulation o User Material Model MF_GenYld+CrachFEM o Exaples o Discussion and Outlook 34 H. Lanzerath

35 Conclusion Replaceent of physical tests by virtual assessent is the target for the future within autootive product developent Qualitatively good siulation results regarding deforation and fracture behavior are needed Coplex yield behavior can be described with aterial odel MF_GenYld in an appropriate and flexible way for all kind of aterials One set of aterial data can be used in all FEA codes Enhanceents in copatibility and exchangeability of aterial odels between different developent partners (aterial producer, coponent supplier, OEM) For the prediction of fracture the CrachFEM algorith has been used and coupled to the MF-GenYld aterial odel Copared to standard aterial odels the odeling with MF-GenYld and CrachFEM shows an increased accuracy in the deforation and fracture behavior for the analyzed aterials MF_GenYld and CrachFEM have been integrated in the workstation and cluster environent at the Ford Motor Copany for RADIOSS and LS-DYNA 35 H. Lanzerath

36 Conclusion The trend in autootive design is to use aterials that offer lightweight potential at affordable costs. New aterials and anufacturing processes as well as increasing developent targets require ore accurate CAE tools. The availability of advanced CAE tools is one of the enablers for the ipleentation of new aterials is necessary to utilize new aterials for cost efficient lightweight design guarantees high efficiency during the vehicle developent process For new aterial siulation ethods new and advanced aterial tests as well as aterial input cards are required. Suppliers (either coponent or aterial suppliers) will be asked by the OEM's to deliver reliable aterial cards, which are systeatically validated against test results. Guarantee of a sooth integration into the CAE developent processes. Therefore standardized physical aterial tests and validation procedures are required. aterial odel facilitates the exchangeability of aterial odels between different developent partners (aterial producer, coponent supplier, OEM) 36 H. Lanzerath

37 Outlook on Casting-to-Crash Mapping and Ford R&A Europe are partner in the EC-funded project NADIA ( One goal of the project is the apping of local properties after casting and solidification on to the FEM esh of the crash siulation Casting siulation Crash siulation 37 H. Lanzerath

38 2 nd European HyperWorks Technology Conference 2008 Strasbourg Septeber 30 th October 1 st, 2008 A New Modular Material Model for the Design of Light Weight Structures in Autootive Engineering with respect to Crashworthiness G. Oberhofer 2, M. Franzen 1, A. Bach 1, H. Gese 2, H. Lanzerath 1 1 Ford Forschungszentru Aachen, Suesterfeldstrasse 200, D Aachen, Gerany 2 Matfe Partnerschaft Dr. Gese & Oberhofer, Nederlingerstr. 1, München, Gerany Thank you for your attention! 38 H. Lanzerath