On the Effect of Johnson Cook Material Constants to Simulate Al2024-T3 Machining Using Finite Element Modeling

Abstract

Finite element modeling (FEM) of machining has recently become the most attractive computational tool to predict and optimize metal cutting processes. High speed computers and advanced finite element code have offered the possibility of simulating complex machining processes such as turning, milling, and drilling. The use of an accurate constitutive law is very important in any metal cutting simulation. It is desirable that a constitutive law could completely characterize the thermo-visco-plastic behavior of the machined materials at high strain rate. However, there exist several constitutive laws that are adopted for machining simulation, the choice of which is difficult to make. The most commonly used law is that of Johnson and Cook (JC) which combines the effect of strains, strain rates and temperatures. Unfortunately, the different coefficients provided in the literature for a given material are not reliable since they affect significantly the predicted results (cutting forces, temperatures, etc.). These discrepancies could be attributed to the different methods used for the determination of the material parameters. In the present work, three different sets of JC are determined based on orthogonal machining tests. These three sets are then used in finite element modelling to simulate the machining behavior of Al 2024-T3 alloy. The aim of this work is to investigate the impact of the three different sets of JC constants on the numerically predicted cutting forces, chip morphology and tool-chip contact length. It is concluded that these predicted parameters are sensitive to the material constants.

3D Finite Element Modelling of Cutting Forces in Drilling Fibre Metal Laminates and Experimental Hole Quality Analysis

“…The overestimation in thrust force prediction in the FE models can be due to several reasons, first the strengths and failure energies in different directions at high strain rates (as expected in material removal processes such as the drilling process) for modelling damage behaviour of homogenised composite ply is not well documented in the literature. Furthermore most of such studies focusing on the high strain-rate behaviour of composites are primarily conducted using uniaxial tension, compression or torsion tests [15,40,52]. Drilling mainly induces bending stresses locally on the workpiece during its entry and exit; though in the absence of suitable data for high-strain behaviour of composites under bending load, the strengths and failure energies from uniaxial tensile tests [44,45,53] was employed in drilling simulations here which has probably led to overestimated results.…”

“…Previous numerical studies considered FE based and analytical-modelling of GLAREs to study their damage under high and low-speed impact, and blast loading primarily [7][8][9][10]. Development of FE models of machining metals and advanced alloys has surged over the years [11][12][13][14][15], while such application to GLAREs is not widely reported. The present work investigates the performance of aerospace structural material GLARE, a fibre metal laminate to machining process using twist drilling operations.…”

Numerical and experimental investigation of Johnson–Cook material models for aluminum (Al 6061-T6) alloy using orthogonal machining approach

“…2 As a result, thermal softening of the material occurs due to quasi-adiabatic condition. 13 Wu and To 11 also deduced that the adiabatic heating effect which occurs during HSM causes thermal softening of the material and produce serrated chips. 11 Therefore, thermal softening along with reduced coefficient of friction was incorporated at higher cutting conditions which resulted in decreased cutting forces.…”

“…Johnson-Cook material model (JC) is extensively used in machining to predict cutting forces, chip morphologies, residual stresses, and temperatures. 2,3,6,[10][11][12][13] The material behavior in JC material constitutive model is represented in terms of strains, strain rates, and temperatures. 2 Higher cutting speed effects heat transfer and cutting temperatures due to short contact time.…”

“…20 The most commonly used material model applied in the finite element modeling of machining processes is the JC, which incorporates the effect of strain, strain rate, and temperature. 13 The JC material coefficients are material specific and determined through different method. Values of JC material coefficients significantly affect the accuracy of the predicted results.…”