Abstract: The foundations of micro-milling are similar to macro-milling but the phenomena it involves are not a simple scaling-down of macro-cutting. The importance of the minimum chip thickness is one of the significant differences between the two processes. The lagrangian FEM model presented in this paper aims to study the depth of cut influence on chip formation of Ti6Al4V in orthogonal cutting. It is firstly used to compare the modelled saw-toothed macro-chip morphology and cutting forces to experimental cutting results from literature. Then a minimum chip thickness prediction is performed by decreasing the depth of cut. Finally this study is the opportunity to highlight the specific features of micro-cutting reported in literature, such as the effective negative rake angle of the tool or the size effect. The model presented brings therefore a numerical contribution to the comprehension of these phenomena.
Abstract: 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.
Abstract: The machining of metal matrix composites (MMC) induces cyclic loadings on tools, which creates new challenges for machining. In particular the distributed reinforcement, consisting of silicon carbide (SiC) or aluminum oxide (Al2O3), evokes especially high mechanical loads. The development of metal matrix composites is pointing towards higher fractions of reinforcements, which affects the resulting forces and temperatures. In this regard the influence of varying particle filling degrees, particle diameters, cutting velocities and tool geometries in terms of rake angle and cutting edge radius have been investigated by means of cutting simulation. For the process a self-designed continuous remeshing routine was used for which a dual phase material behavior has been implemented. The developed simulation model enables investigations of the machining behavior of metal matrix composites to the extent that ideal process strategies and tool geometries can be identified by multiple simulations.
Abstract: Industrial applications of titanium alloys especially in aerospace, marine and offshore industries have grown significantly over the years primarily due to their high strength, light weight as well as good fatigue and corrosion-resistance properties. The machinability of these difficult-to-cut metallic materials with conventional turning (CT) techniques has seen a limited improvement over the years. Ultrasonically-assisted turnning (UAT) is an advanced machining process, which has shown to have specific advantages, especially in the machining of high-strength alloys. In this study a three-dimensional finite element model of ultrasonically-assisted oblique cutting of a Ti-based super-alloy is developed. The nonlinear temperature-sensitive material behaviour is incorporated in our numerical simulations based on results obtained with split-Hopkinson pressure bar tests. Various contact conditions are considered at the tool tip-workpiece interface to get an in-depth understanding of the mechanism influencing cutting parameters. The simulation results obtained are compared for both CT and UAT conditions to elucidate main deformation mechanisms responsible for the observed changes in the material’s responses to cutting techniques.
Abstract: The paper aims to predict component conditions after each subprocess of a manufacturing process chain. A continuous simulation has to be achieved, considering the inheritance of component states. To identify functional descriptions between component conditions as input and output quantities a broaching simulation is being developed. It includes multiple chip formation with multi-toothed broaching tools and machining history of a component as well. For this purpose component conditions are extracted from and transferred to a workpiece model as an initial condition. The 2D finite element chip formation model uses remeshing for material separation allowing highly detailed surface layer characterizations. Parallel experimental studies vary process parameters, whose objective is optimization of process control and forecast of component properties. Characterization of component conditions is based on distortion analysis, cutting force and surface measurements. Comparing the specific cutting forces between simulation model and performed experiments show a reasonable agreement of results
Abstract: Latest research clearly demonstrates the excellent capability of the gear skiving process. For further improvement of the process and particularly for the enhancement of the process reliability fundamental scientific research is conducted. In this paper the result of investigation of process kinematics and chip formation mechanisms are presented. First the experimental analyses will be described, which represent an essential basis for developing and validating the models. In further experiments the material behavior of the test material SAE 5120 was determined and a material model was developed. The modeling of the process represents a central aspect of the research. This includes the basic modeling of the kinematics in a 3D-model. The simulation enables analysis of the kinematical conditions as well as the chip formation mechanisms and evaluation of the effects on process reliability. The results support the tool and process design and are an important basis for the implementation of the process.
Abstract: Machining of large monolithic structures is standard practice in today’s aerospace world. Driven by cost and performance, it is becoming necessary for airframe manufacturers to machine parts better, faster, lighter, and cheaper than ever before. When machining these large monolithic structures, however, distortion becomes a significant problem. The typical solution to this problem is to machine with lower than optimum material removal rates, and perform additional fixture rotations – both of which add unnecessary time and cost to the manufacturing process. A finite element model has been developed specifically to predict and control these distortions. The model takes into consideration the machining-induced residual stresses, as well as the bulk stresses in the material from the manufacturer.
Abstract: Multi-axis controlled machining has been increasing with the demand for high quality in mold manufacturing. The cutter axis inclination should be properly determined in the milling operations. The paper discusses the cutting process of ball end mill with the cutter axis inclination. Two mechanistic models are presented to show the effect of the cutter axis inclination on the tool wear and the surface finish. The actual cutting time during a rotation of the cutter reduces with increasing the cutter axis inclination. Then, the tool is cooled in the non-cutting time. The tool wear is suppressed with reducing the cutting temperature. The surface finish is also improved by increasing cutting velocities with the cutter axis inclination. When the cutter is inclined in the feed direction, the effect of the edge roughness on the surface finish is eliminated. The discussion based on the simulation is verified in the cutting tests for brittle materials.
Abstract: In turning, the applied forces have to be known as accurately as possible, especially in the case of difficult-to-cut materials for aircraft workpieces finishing operations. Traditionally, edge discretisation methodology based on local cutting laws is used to determine the cutting forces and results are usually considered suitable. Nevertheless, only the rake face is considered in most of studies and the cutting relations are determined by direct identification with a straight edge. This study deals with finishing operations of Inconel 718 alloy with one type of round insert. The main objective is to formulate a novel cutting forces model, taking into account the clearance face. First, a generic model based on a geometrical description using homogeneous matrix transformation is presented. Then, cutting coefficients are identified by inverse identification from experimental measurements distributed with an orthogonal design experiment including tool wear. Finally, modeling and experimental values of the cutting forces are compared and the identified model is analysed.