Topology optimization of automotive components subjected to low cycle fatigue

Frankenthal, 28.06.2017András TANOS, R&D Engineer

FÉMALK Co. – at a glance

Usual requirements of engine suspension mounts

Material testing

• Monotonic properties• Cyclic properties

Validation of material models

Optimization with fatigue constraint

CAD interpretation

Verification

Questions

Contents

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Introduction - FÉMALK Co.

2/14

Aluminium high pressuredie casting foundry

Founded in 1989

100 % family ownership

100 % automotive industry

€ 93,3 million income in 2016

250 - 1000 ton machines

More than 1100 coworkers

Major customers - FÉMALK Co.

3/14

Development project - Requirements

4/14

Dimensions

Feasibility

Prescribed minimum breaking force

Low-cycle fatigue requirementss of fully reversed load cycles

Maximum mass

Prescribed minimum of the first natural frequency

Monotonic material properties

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𝑅𝑅𝑅𝑅𝑅.2 - 0.2% Offset yield strength𝑅𝑅𝑚𝑚 - Ultimate tensile strength𝐸𝐸 - Modulus of elasticity (Young’s modulus)𝐾𝐾 - Monotonic strength coefficient𝑛𝑛 - Monotonic strain hardening exponent

𝜀𝜀 = 𝜀𝜀𝑒𝑒 + 𝜀𝜀𝑝𝑝 =𝜎𝜎𝐸𝐸 +

𝜎𝜎𝐾𝐾

1𝑛𝑛

Cyclic measurements

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𝐾𝐾𝐾 - Cyclic strength coefficient𝑛𝑛𝐾 - Cyclic strain hardening exponent

𝜀𝜀 = 𝜀𝜀𝑒𝑒 + 𝜀𝜀𝑝𝑝 =𝜎𝜎𝐸𝐸 +

𝜎𝜎𝐾𝐾𝐾

1𝑛𝑛′

Cyclic measurements

7/14

𝜀𝜀𝑎𝑎 = 𝜀𝜀𝑎𝑎𝑒𝑒 + 𝜀𝜀𝑎𝑎𝑝𝑝 =

𝜎𝜎𝑓𝑓𝐾𝐸𝐸 2𝑁𝑁𝑓𝑓

𝑏𝑏 + 𝜀𝜀𝑓𝑓𝐾 2𝑁𝑁𝑓𝑓𝑐𝑐

𝜎𝜎𝑓𝑓𝐾 - Fatigue strength coefficient𝑏𝑏 - Fatigue strength exponent𝜀𝜀𝑓𝑓𝐾 - Fatigue ductility coefficient𝑐𝑐 - Fatigue ductility exponent

Validation, FEM

8/14

Validation

9/14

𝐹𝐹, kN Life, -

9 4509 4409 370

Development of a new component

10/14

Interpretation, CAD

11/14

Verification of final design

12/14

feasibility static strength Fatigue life mass 1st natural frequency

original proposal not OK questionable unknown 2111 g 755 Hz

final geometry OK OK OK 1755 g 866 Hz

Ansys results Optistruct results

Similar, optimized project

13/14

Mass: -400 gRigidity: ↑Strength : ↑Feasibility : OK

1650 g1250 g

Predecessorgeometry

STL from OSSmooth

Optimized design

References

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Y.-L. Lee, J. Pan, R. Hathaway and M. Barkey, Fatigue Testing and Analysis, Burlington: Elsevier Butterworth-Heinemann, 2005.

ASTM, “Standard practice for statistical analysis of linear or linearized stress-life (S-N) and strain-life (e-N) fatigue data,” ASTM Standard E 739, Vols. ASTM Designation E 739-91, pp. 1-7, 1998.

Altair, “OptiStruct optimization training material,” Cologne, 2016.

ASTM, “Standard practice for strain-controlled fatigue testing,” ASTM Standard E 606, Vols. ASTM Designation: E 606-92, pp. 1-7, 1998.

C. R. Williams, Y.-L. Lee and J. Rilly, “A practical method for statistical analysis of strain–life fatigue data,” International Journal of Fatigue, vol. 25, no. 5, pp. 427-436, 2003.

M. Avalle, G. Belingardi, M. P. Cavatorta and R. Doglione, "Casting defects and fatigue strength of a die cast aluminium alloy: a comparison between standard specimens and production components," International Journal of Fatigue, vol. 24, pp. 1-9, 2002.

B. Desmorat and R. Desmorat, “Topology optimization in damage governed low cycle fatigue,” Comptes Rendus Mécanique, vol. 336, pp. 448-453, 2008.

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Thank you for your attention!