Development of a predictive simulation method for thin flash generation in flashless precision forging processes of aluminum parts using FEA and experiments


In this paper, the investigation of thin flash generation in precision forging process of an aluminum long flat part is described. The aim was to derive a predictive simulation method for thin flash generation in order to increase both process and part quality in the future. The forging processes were varied by use of different preforms with equal volumes but different mass distributions while using the same final part geometry. The experimentally forged parts were analyzed concerning the amount and part area of the generated thin flash. The conducted FE simulations were analyzed concerning the hydrostatic pressure values p in the part areas near to the tool gap between upper and lower die immediately before form-filling. For a more detailed comparison, single p values were included to hydrostatic pressure functions P. The comparison between the P functions and the experimentally determined thin flash height shows, that high pressure values as well as high gradients of the P functions indicate less thin flash generation. The method therefore allows a qualitative prediction of thin flash generation. It can provide two kind of information. First: The prediction of the specific locations where thin flash is likely to occur in one final part by use of one single preform. Second: The qualitative prediction of the specific final part areas were thin flash is likely to occur depending on different preform geometries. This method will decreases the necessity of time-consuming forging trials and can shorten the preform designing process in the future.

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Tb :

Billet temperature

vf :

Forming velocity/press speed

wg :

Width of gap




Effective strain

σf :

Flow stress

\(\dot {\varepsilon }\) :

Stain rate



m1, m9 :

Coefficient for dependence of the temperature

m2 :

Coefficient for dependence of strain hardening

m3 :

Coefficient for dependence of equivalent strain rate

m4 :

Coefficient for dependence of equivalent strain

m5 :

Coefficient for term coupling temperature and stress

m7 :

Coefficient for term sensitivity of material to stress

m8 :

Coefficient for term coupling temperature and stress rate

τR :

Friction stress

σN :

Normal stress


Coefficient of friction


Factor of friction


Shear yield strength

Tdie :

Initial die temperature

Ta :

Ambient temperature


Thermal effusivity

αT :

Heat transfer coefficient


Hydrostatic pressure


Hydrostatic pressure function.


Length of the measuring line


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The Research Project “ProGrAl” (STO 1011/4 − 1) has been funded by the German Research Foundation (DFG). The authors would like to thank the German Research Foundation (DFG) for the financial and organizational support of this Project. The authors declare that they have no conflict of interest.

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Richter, J., Stonis, M., Langner, J. et al. Development of a predictive simulation method for thin flash generation in flashless precision forging processes of aluminum parts using FEA and experiments. Prod. Eng. Res. Devel. 12, 419–429 (2018).

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  • Forging
  • Flashless precision forging
  • FEA
  • Aluminum
  • Predictive simulation method