Recent advances in modelling of metal machining processes

Finite element simulation of conventional and high speed machining of Ti6Al4V alloy

In literature, five different sets of work material constants used in the Johnson–Cook's (J–C) constitutive equation are implemented in a numerical model to describe the behaviour of AISI 316L steel. The aim of this research is to study the effects of five different sets of material constants of the J–C constitutive equation in finite-element modelling of orthogonal cutting of AISI 316L on the experimental and predicted cutting forces, chip morphology, temperature distributions and residual stresses. Several experimental equipments were used to estimate the experimental results, such as piezoelectric dynamometer for cutting forces measurements, thermal imaging system for temperature measurements and X-ray diffraction technique for residual stresses determination on the machined surfaces; while an elastic–viscoplastic FEM formulation was implemented to predict the local and global variables involved in this research. It has been observed that all the considered process output and, in particular the residual stresses are very sensitive to the J–C's material constants.

The influence of Johnson-Cook material constants on finite element simulation of machining of AISI 316L steel

In this article, deep ball-burnishing as a mechanical surface treatment for improving productivity and quality of rotating shafts is presented. When this technique is combined and applied after conventional turning, the resulting process is rapid, simple and cost-effective, directly applicable in lathes and turning centers of production lines. This process provides good surface finish, high compressive residual stresses, and hardness increment of the surface layer. These characteristics are the key for the fatigue life improvement of the component, and for wear resistance due to the higher hardness. This work presents a complete analysis of the principal beneficial aspects produced by the application of ball-burnishing. To determinate the influence of each process parameter, several tests were carried out. Once the optimum parameters were established, a complete analysis of the surface characteristics was performed. Surface topographies, sub-surface micro-hardness and residual stresses were measured. Complementary, a finite element model of ball-burnishing was used to understand and predict residual stress values and their variety with the process parameters. Results show that burnishing is an economical and feasible mechanical treatment for the quality improvement of rotating components, not only in surface roughness but in compressive residual stresses as well.

http://www.ehu.eus/manufacturing/docpubli/316.pdf

Surface improvement of shafts by the deep ball-burnishing technique

The objective of the research was to improve the wear resistance of titanium alloys by ball burnishing process. Burnishing process parameters such as burnishing speed, burnishing feed, burnishing force and number of pass were considered to minimize the specific wear rate and coefficient of friction. Taguchi optimization results revealed that burnishing force and number of pass were the significant parameters for minimizing the specific wear rate, whereas the burnishing feed and speed play important roles in minimizing the coefficient of friction. After burnishing surface microhardness increased from 340 to 405 Hv, surface roughness decreased from 0.45 to 0.12 μm and compressive residual stress were generated immediately below the burnished surface. The optimization results showed that specific wear rate decreased by 52%, whereas coefficient of friction was reduced by 64% as compared to the turned surface. The results confirm that, an improvement in the wear resistance of Ti–6Al–4V alloy has been achieved by the process of ball burnishing.

Wear resistance enhancement of titanium alloy (Ti–6Al–4V) by ball burnishing process

Finite Element Modeling of Roller Burnishing Process

Determination of flow stress for metal cutting simulation : a progress report

The accuracy of the results obtained from FEM simulation of machining operations depends on the accuracy of input data. Especially, the flow stress data of the workpiece and the friction along tool–chip interface are extremely crucial for the prediction of cutting variables such as cutting forces, chip formation and temperature distribution. The experimental procedures used to determine flow stress and friction are difficult and costly. Understanding how the input variables affect the FEM predictions can lead to more reliable simulation of machining processes. In this study, the sensitivity analysis of flow stress and friction on FEM simulation is conducted. A power law equation was assumed to represent the flow stress of the workpiece. Magnitudes and dependency of the flow stress upon temperature were varied and used in cutting simulations. Sensitivity analysis on friction was conducted by assuming different constant values of friction factors (for shear friction law) and coefficients of frictio...

Effects of flow stress and friction models in finite element simulation of orthogonal cutting—a sensitivity analysis

Hard roller burnishing is a cost-effective finishing and surface enhancement process where a ceramic ball rolls on the machined surface to flatten the roughness peaks The ball is supported and lubricated by hydrostatic fluid in a special tool holder The process not only improves surface finish but also imposes favorable compressive residual stresses in functional surfaces, which can lead to long fatigue life Most research in the past focused on experimental studies There is still a special need for a reliable finite element method (FEM) model that provides a fundamental understanding of the process mechanics In this study, two-dimensional (2D) and three-dimensional FEM models for hard roller burnishing were established The developed 2D FEM model was used to study the effects of process parameters (ie, burnishing pressure, feed rate) on surface finish and residual stresses The simulation results were evaluated and compared to the experimental data Results show that the established FEM model could predict the residual stresses and provided useful information for the effect of process parameters Both FEM and experiments show that burnishing pressure is the most influence, where high burnishing pressure produces less roughness and more compressive residual stress at the surface

Partchapol Sartkulvanich

Papers

Finite Element Modeling of Roller Burnishing Process

Determination of flow stress for metal cutting simulation : a progress report

Effects of flow stress and friction models in finite element simulation of orthogonal cutting—a sensitivity analysis

Finite Element Modeling of Hard Roller Burnishing: An Analysis on the Effects of Process Parameters Upon Surface Finish and Residual Stresses

Finite element analysis of the effect of blanked edge quality upon stretch flanging of AHSS