Toward a better understanding of tool wear effect through a comparison between experiments and SPH numerical modelling of machining hard materials

The aim of this study is to improve the general understanding of tungsten carbide (WC–Co) tool wear under dry machining of the hard-to-cut titanium alloy Ti6Al4V. The chosen approach includes experimental and numerical tests. The experimental part is designed to identify wear mechanisms using cutting force measurements, scanning electron microscope observations and optical profilometer analysis. Machining tests were conducted in the orthogonal cutting framework and showed a strong evolution of the cutting forces and the chip profiles with tool wear. Then, a numerical method has been used in order to model the machining process with both new and worn tools. The use of smoothed particle hydrodynamics model (SPH model) as a numerical tool for a better understanding of the chip formation with worn tools is a key aspect of this work. The redicted chip morphology and the cutting force evolution with respect to the tool wear are qualitatively compared with experimental trends. The chip formation mechanisms during dry cutting process are shown to be quite dependent from the worn tool geometry. These mechanisms explain the high variation of the experimental and numerical feed force between new and worn tools

Damage modes of straight tungsten carbide in dry machining of titanium alloy TA6V

In the present study, dry machining of the titanium alloy TA6V with cemented tungsten carbide tools is tested. The main objective is to analyse the feasibility of the dry machining process on the difficult to cut materials as titanium alloys. The wide accepted tool material for machining this kind of materials i.e. straight tungsten carbide (WC-Co), was initially chosen. During the trials, the tool was rigidly mounted on tool holder with rake angles of $0^{\circ}$, $15^{\circ}$ and $30^{\circ}$. Three cutting speeds (15, 30 and 60 m/min) and three feeds (0.1, 0.2 and 0.3 mm) were used. In order to avoid the shock at the beginning of the cutting operation, the workpiece was prepared by carrying out a chamfer. All inserts have achieved 5 passes (1 pass $=$ 1 m). During the trials the cutting force components were measured using a piezoelectric dynamometer. Scanning electron microscope (SEM) supported by energy dispersive x-ray (EDX) and optical profilometer were investigated in the detailed analysis of tool wear. The correlation between the evolution of cutting forces, the tool damage modes and the workpiece roughness show the influence of the cutting parameters and the insert geometry on the tool wear and on the quality of the finished surface when dry machining TA6V

Evaluation of the performance of coated and uncoated carbide tools in drilling thick CFRP/aluminium alloy stacks

This paper aims to establish the wear mechanisms of coated and uncoated tungsten carbide drills when drilling carbon fibre reinforced plastics (CFRP)/aluminium alloy (Al) stacks. During the drilling experiments, thrust forces were measured. A scanning electron microscope (SEM) and a numerical microscope, provided with a scanning device, were periodically used to analyse tool wear mechanisms and to measure wear progression of the tool cutting edges. For both coated and uncoated drills, abrasion was the dominant tool wear mechanism, affecting the entire cutting edges. Higher wear was observed on uncoated tools which caused a significant increase in thrust force during drilling both Al and CFRP materials. The influence of these phenomena on the quality of the holes and on the generated roughness was also discussed.FUI-Usinage de Multi-Matériaux et Innovation (U2MI

Sub-millimeter measurement of finite strains at cutting tool tip vicinity

The present paper details a simple and effective experimental procedure dedicated to strain measurement during orthogonal cutting operations. It relies on the use of high frame-rate camera and optical microscopy. A numerical post-procedure is also proposed in order to allow particle tracking from Digital Image Correlation (DIC). Therefore strain accumulation within finite strains framework is achieved. The significant magnitude of the calculated strains is partially due to a singular side effect that leads to local material disjunction. The strain localization in the Adiabatic Shear Band (ASB) exhibits different strain paths at various locations along this band and a non-linear evolution of the strain accumulation. A focus is made on the formation mechanisms of serrated chips obtained from Ti6Al4V titanium alloy. The side observation performed during this work allow to proposed three possible scenarios to explain this very phenomenon

Application of high-performance computing to a bolt static tensile test

International audienceFaced with an increasingly fast-changing market, airplane manufacturers have to reduce the development time of their new programs whilst dealing with more and more complex composite structures. The European project Maaximus (More Affordable Aircraft Structure Lifecycle through eXtended, Integrated & Mature nUmerical Sizing) aims at providing methods and tools to enable the fast development and right-first-time validation of a highly optimized composite airframe. In this context, accurate models of fasteners are crucial to ensure correct structure modeling at a higher level. The present study focuses on the mechanical behavior of a threaded assembly subjected to an axial tensile load. After a review of the state-of-the-art in this domain, the first part of the paper shows what benefits can be expected from explicit simulation for large quasistatic models. Parallelization strategies for High-Performance Computing (HPC) are presented, bringing out the need for consistency between the parallelization strategy and the computation structure. These simulation techniques are then applied to the modeling of a tensile test of a fastener. The results of corresponding experiments for two fastener diameters are presented. A successful correlation between simulations and experiments is found, both qualitatively and quantitatively. This study shows the efficiency of a well-chosen resolution algorithm in a coherent HPC environment for solving large non-linear models