EMMC Translation case Residual stresses and structural changes generated at different steps in gear manufacturing: Modelling and validation

Transcription

1 2018 IK4-TEKNIKER EMMC Translation case Residual stresses and structural changes generated at different steps in gear manufacturing: Modelling and validation V. García Navas, O. Gonzalo, I. Quintana, J. Lambarri and A. Igartua Morning Session Glasgow, June 14, 2018

2 Table of contents 1. Overview of IK4-TEKNIKER 2. Context for the translation case 3. Business case 4. Industrial case 5. Analysis of the experimental data 6. Modelling workflow 7. Validation and conclusions

3 WHO WE ARE R&D Centre (not-for-profit Private Foundation) Applied research spanning 37 years. Mission: To enhance the positioning and competitiveness of our clients through technology transfer. Specialised in Manufacturing. Founder members of the IK4 Research Alliance.

4 IK4-TEKNIKER IN FIGURES TOTAL REVENUE ACTIVITY REVENUES 2016 PEOPLE data

5 Modelling / Simulation tools at IK4-TEKNIKER

6 Translation case context End user: manufacturer of transmission systems for high tonnage vehicles Manufacturing technology: Hot Forging Client not expert in material science Previous relation with IK4-TEKNIKER

7 Translation step 1: Business case Problem: Geometrical distortions during the manufacturing process Impact: Several 100k per year due to scrap parts and oversizing Funding under Manunet Innotek program Timeline: Whole project : 24 months Modelling task: 12 months

8 Translation step 2: Industrial case Manufacturing of transmission elements: gears, rings, Process chain: Forging Normalizing Quenching Tempering Machining Tight tolerances Components must withstand high loads High rate of rejections after heat treatments

9 Translation step 2: Industrial case What is the root cause of distortions? Hot forging defects include banding and decarburization at the surface Other common sources of distortions: Part support in the oven Distribution of parts in the quenching bath Well known and accounted for Translation case goal: asses the effect of manufacturing stages on microstructure and dimensional accuracy, including the influence of pre-existing banding and decarburization

10 Translation step 3: Analysis of experimental data Manufacture of a ring with simplified geometry Cut sections and perform different heat treatments: Forged ring 270mm outer diam. 190mm inner diam. 80mm height

11 Translation step 3: Analysis of experimental data Macrostructural data Fibre clearly present in all cases

12 Translation step 3: Analysis of experimental data Microstructural data Decarburization

13 Translation step 3: Analysis of experimental data Microstructural data Banding

14 Translation step 3: Analysis of experimental data CCT diagram (low alloy steel) Thermophysical and mechanical properties (density, enthalpy, heat conductivity, young modulus, thermal expansion coefficients, etc.)

15 Translation step 4: Modelling workflow Continuum approach: coupled thermo-metallurgical + mechanical (FEM) user case input model raw output processed output Geometry, thermophysical properties, initial conditions, heat exchange coefficient, chemical composition, Heat equation Metallurgy equations Temperature Phase volume fractions Thermal field Thermal gradients Hardness Mechanical properties, hardening law, clamping conditions Mechanical analysis Node displacements, forces Stresses Strains

16 Translation step 4: Modelling workflow The following simulations were carried out 3D models, assuming homogeneous material - Normalizing - Normalizing + quenching 2D models, including banding and decarburization - Quenching Experimental thermal cycle

17 Translation step 4: Modelling workflow 3D Mesh 2D Mesh

18 Translation step 5: Strategy for model validation Measure bulk residual stresses measurements at Institute Laue - Langevin

19 Translation step 5: Strategy for model validation Hardness measurements Samples cut after residual stress measurements

20 Hardness and mean stress maps for 2D model Translation step 5: Strategy for model validation

21 Translation step 6: Conclusions Microsegregations produced during forging form banded structures that align following the plastic flow. These banded structures are not completely removed by the normalizing process, and are still present during all the subsequent heat treatments performed on the parts. Banded structures and decarburization result in inhomogeneities in terms of hardness and residual stresses. Microstructure inhomogeneities must be included in the model for accurate predictions

22 Translation step 6: Recommendations for end user At forging: optimize process for more homogeneous fibre structure Increase machining depth after normalizing to remove decarburized zone

23 Acknowledgements The present work was developed in the framework of the Manunet Era-Net project PRO-ENG: Contribution of metallurgical and mechanical characteristics for the high load capacity gears manufacture improvement, financed by the Department of Industry, Trade and Tourism of the Basque Government, under the Innotek program.

24 Eskerrik asko! Gracias! Thank you! IK4-TEKNIKER 2018