The low cycle fatigue (LCF) of dies

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The low cycle fatigue (LCF) of dies

Die tool life is a significant part of the final cost of the part. Therefore, prediction of the service life of dies at the stage of their design increases the efficiency of technological preparation of production. The greatest influence on the durability of dies is wear and fatigue failure.

This section describes how QForm UK simulation of fatigue failure of dies is carried out. The classic model for simulation low-cycle fatigue is the deformation fit by Coffin-Manson. The pulsating cycle of loading dies and the phenomenon of thermocyclic softening complicate the use of the full Coffin-Manson model to analyze the durability of dies. Most researchers, when simulation the fatigue life of dies, do not take into account the plastic component of strain and use either the elastic component of the Coffin-Manson law, or fit by Basquina, based on cycle stress analysis.

In QForm UK to analyze the durability of dies, it is proposed to use the Gusenkov deformation-kinetic criterion:

•Elastic-Plastic Thermomechanical Fatigue Analysis of Forging Dies //A. Vlasov, N. Biba and S. Stebunov, Volume 716 of Key Engineering Materials, 2016 Trans Tech Publications Ltd, Switzerland, p.667

This criterion makes it possible to take into account both elastic and plastic components of strain with thermocyclic softening. To the commercial software QForm UK integrated subroutine, which makes it possible to predict the number of cycles before the destruction of the die tool.

A good convergence of the simulation results the tool life in QForm UKwith industrial data obtained when forging a cone gear on a mechanical press and when forging a lever on a hammer.