BASED ON THE EXTENDED THICK SHEAR ZONE ANALYSIS: METAL CUTTING AS MATERIAL CHARACTERIZATION TECHNIQUE

Abstract

Material characterization under various loading conditions is essential for researchers to evaluate its response under operational conditions. The presented research focuses on metal machining simulation and benefits from the variation of cutting conditions encountered along the drill bit cutting lip to conceive a procedure for updating material model subject to the cutting action. Specifically, the presented methodology, dubbed the drill lip cutting force prediction methodology, utilizes a small number of pre-cored drilling experiments to extract the Johnson-Cook (JC) parameters for Aluminum Al6061-T6 material.

Machining simulation is based on the existing thick shear zone simulation approach. The DLCFPM is modified to account for multiple material models popular in literature as an extension to Oxley machining prediction methodology through substituting the original velocity-modified power form material model by the widely used constitutive material model developed by Zerilli and Armstrong (ZA) of types applicable to hexagonal close-packed (HCP), body-centered cubic (BCC) and face-centered cubic (FCC) metals.

Magnesium alloy of the type AZ31B is used as an application and cutting experiments coupled with the HCP Zerilli Armstrong material model used to update the material parameters following the inverse methodology based on turning operations.

Also, the conceived machining forces simulation thick shear zone accounted for the variations of ZA constitutive laws applicable to body-centered cubic (BCC) and face-centered cubic (FCC) and validated against literature reported machining tests. Validation of the ZA FCC extension is performed against reported Aluminum 6061-T6 turning tests. And the BCC/FCC dual methodology is challenged against performed AISI 1045 literature reported turning experiments.

A thermal extension is adopted for the thick shear zone approach by modifying the moving heat source analytical solution. The adopted thermal extension is coupled with the conceived drill lip cutting force prediction methodology for simulating the drilling process. This methodology validated by comparing to experimentally collected drilling torque, thrust, and drill lip flank temperatures based on Aluminum 6061-T6 workpiece material.

The outcomes of the research are defined by extending the thick shear zone approach to account for the Zerilli Armstrong material model variations along with accounting for the modified moving heat source thermal model. The proposed thick shear zone approach validated for simulating machining response under simple orthogonal cutting along with simulating complex machining processes such as drilling. The conceived machining simulation methodology also used as a material characterization tool for modeling the material response subject to operating strain, strain rates, and temperatures encountered in machining through the inverse method. As an application, the conceived simulation method may be used by machinists for simulating cutting conditions, thus optimizing the tool geometry as well as identifying operational parameters that satisfy the reduced tool wear and energy consumption criteria.