Abstract
Understanding the effect of thermomechanical loads during finish cutting processes, in our case hard milling, on the surface integrity of the workpiece is crucial for the creation of defined quality characteristics of high-performance components. Compared to computationally generated modifications by simulation, the measurement-based determination of material modifications can only be carried out selectively and on a point-by-point basis. In practice, however, detailed knowledge of the changes in material properties at arbitrary points of the high-performance component is of great interest. In this paper, a modification of the well-known Johnson–Cook material model using the finite element software Abaqus is presented. Special attention was paid to the kinematic hardening behavior of the used steel material. Cyclic loads are relevant for the chip formation simulation because, during milling, after each cut, the material under the surface is loaded plastically several times and not necessarily in the same direction. Therefore, in analogy, multiple bending was investigated on samples made of 42CrMo4. A pronounced Bauschinger effect was observed in the bending tests. An adaptation of the material model to the results of the bending tests was only possible to a limited extent without kinematic hardening, which is why the Johnson–Cook model was supplemented by the Armstrong–Frederick hardening approach. The modified Johnson–Cook–Armstrong–Frederick material model was developed for practical use as a VUMAT and verified by bending tests for simulation use.
Highlights
In the die and mold making industry, hard milling is a competitive process allowing for high production rates and high surface quality while ensuring a favorable residual stress state of the workpiece surface layer
The standard Johnson–Cook model was extended by a kinematic strain hardening model based on the approach proposed by Armstrong and Frederick
Both the standard Johnson–Cook model and its modification with kinematic strain hardening were utilized in the simulation of a cyclic bending test
Summary
In the die and mold making industry, hard milling is a competitive process allowing for high production rates (material removal rates) and high surface quality while ensuring a favorable residual stress state of the workpiece surface layer. Both the surface quality and the residual stress state of the top layer significantly influence the machining time and improve the fatigue strength, corrosion resistance and creep resistance. An important criterion for the part quality is the residual stress state of the surface layer [1]
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have