Mustapha Abouridouane

3D Modelling and Simulation of Gun Drilling

The main objective of this paper is the development and validation of a three dimensional thermomechanically coupled finite element model for gun drilling AISI 4150 quenched and tempered steel. The Lagrangian formulation proposed in the FE code DEFORM 3DTM and the constitutive Johnson-Cook material model were utilized to simulate the chip formation and to predict the cutting reaction forces as well as the temperature in gun drilling process using carbide gun drills with two different diameters. During gun drilling simulation, modified gun drill cutting edge rounding and friction law are performed to investigate the effect of tool wear and lubrication on feed force and torque respectively. Experimental gun drilling tests were carried out in steel AISI 4150 for the validation of the developed 3D FE model. The developed and validated 3D FE model can be used for optimizing the cutting process in gun drilling (good surface finish and straightness) taking into account the complex gun drill geometry, cutting conditions, heat transfer and the thermo-mechanical behaviour of the workpiece material.

Thermal evaluation by infrared measurement of implant site preparation between single and gradual drilling in artificial bone blocks of different densities.

The aim of this study was to investigate the influence of bone density and drilling protocol on heat generation during implant bed preparation. Ten single and 10 gradual implant sites with diameters of 2.8, 3.5, and 4.2mm were prepared in four artificial bone blocks (density types I-IV; D1-D4). Drilling was done at constant speed (1500rpm) and with external irrigation (50ml/min); vertical speed was set at 2mm/s. An infrared camera was used for temperature measurements. Significantly higher temperatures for single drilling were found between 2.8-mm drills in D1 (P=0.0014) and D4 (P<0.0001) and between 3.5-mm drills in D3 (P=0.0087) and D4 (P<0.0001), as well as between 4.2-mm drills in D1 (P<0.0001) and D4 (P=0.0014). Low bone density led to a thermal decrease after single drilling and a thermal increase after gradual drilling. Burs with a large diameter always showed a higher temperature generation. In comparisons between 2.8- and 4.2-mm diameters for both single and gradual drills, significant differences (P<0.001) were noted for bone types II, III, and IV. Single drilling could generate more heat than traditional sequential drilling, and bone density, as well as drill diameter, influenced thermal increases. Particularly in lower-density bone, conventional sequential drilling seems to raise the temperature less.

Microstructure-based 3D FE modeling for micro cutting ferritic-pearlitic carbon steels

The mechanics of the cutting process on the microscopic level differ fundamentally from the conventional macro cutting. For example, the tool edge radius influences the cutting mechanism in micro machining significantly with regard to the effective rake angle, the minimum chip thickness, the dominance of ploughing, and the related elasto-plastic deformation of the workpiece material. These phenomena, known as size effects, have a profound impact on the cutting force, process stability, and resulting surface finish in micro cutting. Therefore, microstructural effects in microscale cutting require quite different assumptions to be made concerning underlying material behaviour during micro cutting and have led to the need for new modeling approaches to account for such effects.This paper presents a three-dimensional finite element approach to incorporate microstructure into micro cutting simulation based on the concept of a representative volume element (RVE) and constitutive material modeling as well as using the Lagrangian formulation proposed in the implicit FE code Deform 3D™. Micro drilling and micro milling tests using solid carbide tools with different diameters (d = 50 μm − 1 mm) were performed on ferrite-pearlite two-phase steel AISI 1045 for the verification of the developed 3D multiphase FE computation model regarding chip formation, feed force, and torque. The developed 3D multiphase FE model was successfully used to predict size effects in micro cutting.Copyright

Estimation of the influence of tool wear on force signals: A finite element approach in AISI 1045 orthogonal cutting

Industrial concerns arise regarding the significant cost of cutting tools in machining process. In particular, their improper replacement policy can lead either to scraps, or to early tool replacements, which would waste fine tools. ISO 3685 provides the flank wear end-of-life criterion. Flank wear is also the nominal type of wear for longest tool lifetimes in optimal cutting conditions. Its consequences include bad surface roughness and dimensional discrepancies. In order to aid the replacement decision process, several tool condition monitoring techniques are suggested. Force signals were shown in the literature to be strongly linked with tools flank wear. It can therefore be assumed that force signals are highly relevant for monitoring the condition of cutting tools and providing decision-aid information in the framework of their maintenance and replacement. The objective of this work is to correlate tools flank wear with numerically computed force signals. The present work uses a Finite Element Model with a Coupled Eulerian-Lagrangian approach. The geometry of the tool is changed for different runs of the model, in order to obtain results that are specific to a certain level of wear. The model is assessed by comparison with experimental data gathered earlier on fresh tools. Using the model at constant cutting parameters, force signals under different tool wear states are computed and provide force signals for each studied tool geometry. These signals are qualitatively compared with relevant data from the literature. At this point, no quantitative comparison could be performed on worn tools because the reviewed literature failed to provide similar studies in this material, either numerical or experimental. Therefore, further development of this work should include experimental campaigns aiming at collecting cutting forces signals and assessing the numerical results that were achieved through this work.