Abstract
The finite element modeling is significantly dependent on the accurate prediction of the material behavior. In order to increase the accuracy of numerical simulations, a new phenomenological model is proposed in this study. Its mathematical formulation allows suitable predictions of the Ti6Al4V sensitivity to strain rates and temperatures, while maintaining a low identification cost of its constitutive coefficients. A subroutine VUMAT is developed, and its reliability is investigated in the case of the modeling of uniaxial tensile and impact tests. In addition, the 3D numerical analysis of the machining process is investigated based on the definition of the rheological Johnson-Cook model and the proposed one. Experimental orthogonal machining tests are also established for several cutting conditions. The significant sensitivity of the chip serration, the segments geometry, and the cutting forces to the feed rate is pointed out. Comparisons of the numerical results corresponding to different constitutive models are carried out. High-correlation levels with the experimental results are reached with the definition of the proposed phenomenological model, which is not the case of the Johnson-Cook empirical law. Moreover, intuitive insights about the effect of cutting conditions on the material flow towards the workpiece edges are provided with the 3D modeling. A pronounced increase of the width of side burrs with the feed rate rise was underlined. The results presented in this study point out the inability of 2D numerical simulations to accurately predict the phenomena induced during the machining process, even in the case of an orthogonal machining.
Highlights
The commonly used biphasic Ti6Al4V titanium alloy is known for its interesting strength-to-weight ratio, as well as its excellent resistance to corrosion
The high gradients of plastic strains, strain rates, and temperatures, which are encountered during the Ti6Al4V machining, result in an accelerated tool wear, mainly in the case of high chemical affinity with the cutting tool material [2]
Errors up to 31% were reached, while it was ranged between 0.8 and 11% in the case of the proposed model’s definition to the workpiece. Even though this rheological model resulted in high correlations with the experimental chip morphology, segments geometry, and cutting forces, an underestimation of the experimental feed forces was noted for the investigated cutting conditions
Summary
The commonly used biphasic Ti6Al4V titanium alloy is known for its interesting strength-to-weight ratio, as well as its excellent resistance to corrosion. In. The availability of powerful and efficient commercial codes has encouraged the establishment of numerical analyses, mainly in the case of the machining process, where severe dynamic and non-linear conditions are taking place. Despite the reliability of these constitutive models, they have been uncommonly used for the modeling of the machining process, in which heavy interactions between the involved phenomena are taking place These constitutive models are characterized by the complicated identification of their numerous and coupled coefficients, where the setting up of particular experimental tests and the use of evolved equipment are deeply required. Attention is paid to the effect of this constitutive model on the accurate prediction of the material behavior, to the identification of its coefficients, as well as to its implementation in the numerical software Abaqus®. The 3D modeling of the orthogonal machining highlighted the sensitivity of side burrs to the cutting conditions
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