Microstructure-based material model for thermo …Microstructure-based material model for...
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Microstructure-based material model for thermo-mechanical fatigue of cylinder heads J.C. Pina, V.G. Kouznetsova, M.G.D. Geers M2i-Materials Innovation Institute Eindhoven University of Technology, Faculty of Mechanical Engineering P.O. Box 513, 5600 MB Eindhoven, The Netherlands Phone: 040-2475169, e-mail: [email protected] Introduction Thermo-mechanical fatigue (TMF) arises as a conse- quence of thermal related stresses that develop due to thermo-mechanical cycling loading. TMF failure in truck engines can be described as: • Engine start-stop cycle results in large temperature variations. • The constrained condition found in cylinder heads, produces compressive and tensile stresses. • Continuous thermal cycling produce valve bridge cracking, resulting in cylinder head TMF failure (Figure 1). DAF XF Truck engine DAF XF Truck cylinder head TMF cracks at cylinder head valve bridge Figure 1 : TMF cracks at valve bridges (Courtesy of DAF Trucks N.V.). Cast iron heterogonous microstructure (fer- rite/pearlite matrix & graphite inclusions, Figure 2), makes prediction of its response at the macro level very complex. a) Flake graphite b) Compacted graphite c) Spheroidal graphite Figure 2 : Graphite morphologies found in cast irons [1]. Aim of the project Develop a microstructure-based model for TMF life prediction that considers the differ- ent microstructural phases, their interaction and im- pact on TMF response. Modelling approach The basic phenomena to include in the model are: • 3D Representative Volume Element (RVE) since the microstructure is inherently three-dimensional. • Microcrack initiation & propagation through the graphite-matrix interface. • Graphite anisotropy of mechanical & thermal prop- erties. • Creep & stress relaxation. • Thermo-mechanical cycling. Example Figure 3 shows a microstructure-based material model for nodular cast iron [2]. Equivalent von Mises stress 3.80e+08 3.70e+08 3.60e+08 3.50e+08 3.40e+08 3.30e+08 3.20e+08 3.10e+08 3.00e+08 2.90e+08 2.80e+08 Figure 3 : Microstructure-based material model of nodular cast iron under static tensile loading (vertical direction) [2]. Future work • Improvement of existing cast iron model [2], by in- cluding graphite anisotropy and the different matrix phases (pearlite & ferrite). • Development of cast iron microstructure-based model for thermo-mechanical loading conditions, including creep and stress relaxation. • Development of cast iron microstructure-based model for TMF life prediction, where the influence of damage evolution at the micro level is incorpo- rated at the macro level. References 1. Sj¨ ogren, T. (2005), PhD Thesis, J¨ onk¨ oping University, Swe- den. 2. van den Oord, G.A.H. (2009), Master Thesis, Eindhoven Uni- versity of Technology, The Netherlands.
Transcript of Microstructure-based material model for thermo …Microstructure-based material model for...
Microstructure-based material model forthermo-mechanical fatigue of cylinder heads
J.C. Pina, V.G. Kouznetsova, M.G.D. Geers
M2i-Materials Innovation InstituteEindhoven University of Technology, Faculty of Mechanical Engineering
P.O. Box 513, 5600 MB Eindhoven, The NetherlandsPhone: 040-2475169, e-mail: [email protected]
IntroductionThermo-mechanical fatigue (TMF) arises as a conse-quence of thermal related stresses that develop dueto thermo-mechanical cycling loading.TMF failure in truck engines can be described as:
• Engine start-stop cycle results in large temperaturevariations.
• The constrained condition found in cylinder heads,produces compressive and tensile stresses.
• Continuous thermal cycling produce valve bridgecracking, resulting in cylinder head TMF failure(Figure 1).
DAF XF Truck engine
DAF XF Truck cylinder head
TMF cracks at cylinderhead valve bridge
Figure 1 : TMF cracks at valve bridges (Courtesy ofDAF Trucks N.V.).
Cast iron heterogonous microstructure (fer-rite/pearlite matrix & graphite inclusions, Figure 2),makes prediction of its response at the macro levelvery complex.
a) Flake graphite b) Compacted graphite c) Spheroidal graphite
Figure 2 : Graphite morphologies found in cast irons [1].
Aim of the project Develop a microstructure-basedmodel for TMF life prediction that considers the differ-ent microstructural phases, their interaction and im-pact on TMF response.
Modelling approachThe basic phenomena to include in the model are:
• 3D Representative Volume Element (RVE) sincethe microstructure is inherently three-dimensional.
• Microcrack initiation & propagation through thegraphite-matrix interface.
• Graphite anisotropy of mechanical & thermal prop-erties.
• Creep & stress relaxation.• Thermo-mechanical cycling.
Example Figure 3 shows a microstructure-basedmaterial model for nodular cast iron [2].
Equivalent von Mises stress
3.80e+08
3.70e+08
3.60e+08
3.50e+08
3.40e+08
3.30e+08
3.20e+08
3.10e+08
3.00e+08
2.90e+08
2.80e+08
Figure 3 : Microstructure-based material model ofnodular cast iron under static tensile loading (verticaldirection) [2].
Future work• Improvement of existing cast iron model [2], by in-
cluding graphite anisotropy and the different matrixphases (pearlite & ferrite).
• Development of cast iron microstructure-basedmodel for thermo-mechanical loading conditions,including creep and stress relaxation.
• Development of cast iron microstructure-basedmodel for TMF life prediction, where the influenceof damage evolution at the micro level is incorpo-rated at the macro level.
References1. Sjogren, T. (2005), PhD Thesis, Jonkoping University, Swe-
den.2. van den Oord, G.A.H. (2009), Master Thesis, Eindhoven Uni-
versity of Technology, The Netherlands.
