*3.1. Finite Element Modeling of Vit1 BMG Turning Simulation*

The accuracy of material model has a great influence on the success of simulation. In order to accurately reflect the nonlinear problem in the cutting process, it is necessary to comprehensively consider the stress–strain state of each point in the BMG under the complex strain state. The constitutive model of the material represents the stress–strain relationship of the material under load and describes it by mathematical expression. D–P model is a constitutive model of geotechnical materials. It not only considers the effect of intermediate principal stress on material yield, but also explains the experimental phenomena of "shear expansion effect" and "tension compression asymmetry" of metallic glass [8,23]. In this study, the D–P model is used as the constitutive model of vit1-metallic glass, and its main parameters [14,24] are shown in Table 3. Specifically, the D–P plasticity is defined by dilatancy angle, friction angle and flow–stress ratio, d-p hardening is defined by yield stress and absolute plastic strain.



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The material parameters of vit1 BMG and turning tool are shown in Table 4. The constitutive model of metallic glass and the physical parameters of material are introduced into ABAQUS (Dassault Systèmes, Vélizy-Villacoublay Cedex, France), and the chip separation criterion is shear criterion.


**Table 4.** Physical parameters of Bulk metallic glass (BMG) and turning tool.

Figure 7 shows the parameters and meshing of BMG turning simulation. YG-8 cemented carbide tool with 10◦ rake angle α and 7◦ relief angle β is chosen, and the nose radius *r*<sup>ε</sup> is set as 0.2 mm. The longitudinal ultrasonic vibration is applied to the tool in the amplitude *A* paralleling to the relative turning motion. Due to the short cutting distance, the deformation of the turning tool could be ignored, and the tool is then set as a rigid body. In order to reduce the amount of calculation and ensure the accuracy of calculation, the side grid close to the cutting surface is relatively dense, and the side grid of the principle cutting surface is relatively sparse. *α β* ݎ<sup>ఌ</sup>

**Figure 7.** Parameters and meshing of BMG turning simulation.
