1. Name: Chen Xuesheng Supervisor: Dr. Raj Balendra Project: Precision Cold Forging Status: The Second Year of Ph.D Research Title of presentation:

2. 1. Introduction 1.1 Current situation What is upsetting? Still to be one of the main means to measure working material properties and one operation which has been studied most Necessity to obtain more accurate material properties in precision cold forging

4. I) Geometric errors of specimen II) Strain rate III) Friction IV) Thermal expansion V) Non-uniform distribution of compositions VI) Errors from measuring system 1.2 Problems existed Factors affecting measuring accuracy. Kopp presents that:

5. The treatment about friction at present: I) Minimise friction by lubrication and by carefully designed geometry, although with some stroke, contact pressure errors and limited compression stroke; and it is difficult to obtain large strain experiment II) Remove the influence of friction by iterative FE simulation. Parteder developed a numerical technical to interpret flow-curve under sticking interface condition Aim of this research: Develop a numerical method to interpret the material flow curve under coulomb friction condition

6. 2. Algorithm

9. Or if close enough to

10. 3. Iteration process

11. 4. Examples 4.1 Iteration precision From : to get barrelling shape and forging force by FE simulation, then start iteration from

12. Initial point First iteration Second and after iterations

13. 4.2 The comparison between this approach and conventional method Experiment and FE results by this approach FE results by conventional data

14. Conventional result Barrelling size form 0.5 to 1.5 mm

17. 5. Conclusions The minimisation technique presented here can interpret material flow curve and frictional coefficient properly, errors caused by friction is minimised, both forging force and shape of free surface from FE simulation will be closest to the corresponding experiment results; The approach provides a possibility to conduct relative large compression stroke upsetting test in order to get material flow curve at large equivalent strain; Both the errors of flow curve and frictional coefficient are proportional to the relative barrelling size when the compression stroke is relatively small. This make it possible to check the effectiveness of lubricants and to get the corresponding frictional coefficient by simple upsetting test.

18. Questions?