Residual Stresses in Orthogonal Cutting of Metals: The Effect of Thermomechanical Coupling Parameters and of Friction

Abstract

The generation of residual stresses in orthogonal machining is analysed by using an Arbitrary Lagrangian Eulerian (ALE) finite element approach. It is shown that a substantial level of tensile residual stresses can be obtained in the vicinity of the machined surface without any contribution of thermal effects. This motivates the development of a parametric study to analyse the effects of the thermomechanical coupling parameters on residual stresses. The roles of thermal expansion, of thermal softening and of the Taylor-Quinney coefficient (controlling the heat generated by plastic flow) are considered separately. The influence of friction is also analysed by assuming dry cutting conditions and a Coulomb friction law. The friction coefficient has a complex effect by controlling heat generation (frictional heating) along the tool rake and clearance faces and the propensity for the chip to stick to the tool. Geometrical effects such as the tool rake angle and the tool edge radius are also discussed.

Analysis of adiabatic shear banding in orthogonal cutting of Ti alloy

“…Below the crack a layer of two elements is less deformed to a level of about ε¼ 0.4. The plastic work per unit volume in the highly deformed elements can be estimated as s Y ε crit ¼ 2400 MJ=m 3 if we consider that the yield stress for Ti alloys is about s Y ¼ 800 MPa and that the accumulated plastic strain is close to the value ε¼ 3. Considering that the element size is δ ¼ 1 μm, that a layer of 4 adjacent elements is highly deformed at the crack tip and neglecting the work of deformation in the elements below the crack, a lower bound of the plastic work associated to the propagation of the ductile crack is obtained as:…”

“…Numerical simulations permit to gather information on difficult to measure variables during machining processes and also diminish the need of experimental work which is commonly time consuming and expensive. These approaches have been used for decades focusing on different aspects of the metal cutting process such as, interface contact [2,18], constitutive model of the workpiece [19], surface integrity [3] or influence of tool wear [20]. The simulation of oblique cutting commonly performed in real industrial applications needs three dimensional (3D) modeling.…”

“…Finite element (FE) method has been widely used to model metal cutting and to improve the understanding of mechanisms of chip generation, contact phenomena [2] and the effect in surface integrity [3]. This approach allows gathering information on difficult to measure variables during the machining process.…”

A constitutive model for analyzing martensite formation in austenitic steels deforming at high strain rates

“…The thermodynamic process deviates from the isothermal conditions and approaches adiabaticity, leading to large variations in the temperature field (Liang and Khan, 1999;Khan et al, 2004). Also, forming and machining processes, used to elaborate components made of metastable austenitic steels, take place under non isothermal conditions (Hänsel et al, 1998;Miguélez et al, 2009). Since temperature strongly affects the SIMT process, its effect on strain hardening and ductility of metastable austenitic steels deforming at high strain rates needs to be considered.…”

Numerical analysis of the tool wear effect in the machining induced residual stresses

“…Tensile residual stresses in the vicinity of the machined surface, has negative effects on fatigue, fracture resistance and on stress corrosion and therefore can substantially reduce the component life [1]. The residual stress level is strongly related to both mechanical and thermal phenomena induced during chip removal [2]. As is well known these phenomena depend on the tool geometry.…”