A comprehensive systematic comparative study on high-strain-rate tests (Split Hopkinson Pressure Bar), with and without in-situ heating of the specimens and their respective influence on the quality of empirical material models is presented. The determination of material constitutive model parameters is one of the most challenging aspects of the modelling and simulation of machining processes. Chip formation and process forces show a significant dependence on the actual constitutive model and its parameters as well as on the testing method. Typically, the influences of strain, strain rate, and temperature are investigated in separate experiments of quasi-static compression tests and tests, because the most widespread phenomenological constitutive material models (e.g. Johnson–Cook model) neglect interactions between temperature and strain rate. In contrast, the presented work demonstrates, that a coupled experimental approach of strain rate and temperature in the same test increases the quality of such uncoupled material models as well. The authors compared both approaches (separated and in situ temperature-dependent experiments) by determining the constitutive model parameters for AISI 5115 steel samples taken from a single material batch. The parameters are calculated based on a covariance matrix adaptation evolution strategy and applied in identical two-dimensional orthogonal FEM cutting simulations. Process forces and chip thickness values were used for comparison with the machining experiments. The work therefore gives new aspects to decide for a suitable experimental approach when calibrating a constitutive equation. © 2022 Elsevier B.V.

Numerical simulation of metal cutting with rigorous experimental validation is a profitable approach that facilitates process optimization and better productivity. In this work, we apply the Smoothed Particle Hydrodynamics (SPH) and Finite Element Method (FEM) to simulate the chip formation process within a thermo-mechanically coupled framework. A series of cutting experiments on two widely-used workpiece materials, i.e., AISI 1045 steel and Ti6Al4V titanium alloy, is conducted for validation purposes. Furthermore, we present a novel technique to measure the rake face temperature without manipulating the chip flow within the experimental framework, which offers a new quality of the experimental validation of thermal loads in orthogonal metal cutting. All material parameters and friction coefficients are identified in-situ, proposing new values for temperature-dependent and velocity-dependent friction coefficients of AISI 1045 and Ti6Al4V under the cutting conditions. Simulation results show that the choice of friction coefficient has a higher impact on SPH forces than FEM. Average errors of force prediction for SPH and FEM were in the range of 33% and 23%, respectively. Except for the rake face temperature of Ti6Al4V, both SPH and FEM provide accurate predictions of thermal loads with 5–20% error. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

The friction in the contact zones during chip formation has a significant effect on tool wear and surface integrity. Especially the interaction of cooling lubricants and different surface preparations is rather unexplored. In the context of the present publication, the friction between tool and workpiece is therefore investigated in a special test under conditions close to machining for specific prepared tool surfaces when using a cooling lubricant. The results of the investigation are used to develop friction models depending on relative speed, surface preparation and intermediate medium, which will be implemented in new finite element formulations for chip formation simulation. © 2021 Elsevier B.V.. All rights reserved.

Mechanical properties of BTA deep drilled components made of AISI 4140+QT under quasi-static loading are analyzed in instrumented compression tests, inspired by the tube-flattening test according to DIN EN ISO 8492. Digital image correlation (DIC) analysis is used to observe spatial strain distribution on the front side of specimens during compression. It is found that microstructural changes resulting from drilling, particularly the formation of white etching layers (WEL), play a key role in the loading capability of the components under compression. Higher forces needed to be applied to compress specimens with WEL and crack initiation was observed at lower displacements. © 2021 The Authors. Published by Elsevier B.V.

In the machining process, both the tool wear and the surface integrity of the machined workpiece are significantly influenced by the friction. For this reason, the reliable prediction of friction behavior is of great importance for simulation-based tool and process design. It is known from previous investigations that the relative speed is a significant factor influencing the friction behavior between metallic materials and cemented carbide. The exact relationship, particularly in relation to the topography of the tool surfaces, is mainly unexplored. In the context of this publication, results from a friction characterization under machining-similar conditions for AISI 1045 and differently prepared cemented carbide surfaces are presented. The focus of the paper is to develop models for the friction coefficient, based on these results, which take the relative speed and the surface topography into account. Within a Finite-Element chip formation simulation, these models are compared to conventional models that assume the friction coefficient to be constant. For the validation of the simulations, results are used, which were determined from orthogonal cutting tests with differently prepared rake faces. Within the scope of these cutting tests, knowledge was gained about the influence of the rake face topography and the cutting parameters on the friction in the secondary shear zone. © 2021 Elsevier B.V.

The BTA (Boring and Trepanning Association) deep-hole drilling process is used to machine bores with large diameters (D > 40 mm) and a bore-length (l) to diameter ratio lager than ten (l/D >10). The resulting bore surface and its sub-surface zone are influenced by the cutting action and the self-guiding effect of the tool. The Guide pads support the asymmetric tool on the bore surface while burnishing the surface. The mechanical/thermal loads induced by the process lead to hardening, microstructure alteration and substantial residual stresses in the sub-surface. Particularly the residual stress state influences the fatigue strength and reliability of the machined part. To predict the residual stress in BTA deep-hole drilling, for the first time a novel analytical modeling approach is developed based on eigenstrain theory, integrating the machining process of cutting insert and the burnishing process of guide pad. A semi-analytical 3D contact model is built for the cycling incremental plasticity due to the equivalent mechanical/thermal loading of cutting process. Furthermore, an approximate estimation is provided for the contact condition between the inclined guide pad and bore hole, which facilitates the incremental contact analysis in the burnishing process. With the induced inelastic deformation known, residual stress distribution in the machined surface is constructed based on the eigenstrain theory. The results of the model are compared to X-Ray-Diffraction (XRD) measurements of BTA deep-hole drilled specimens. © 2021 The Author(s).

The article deals with aspects of developing methods specifi-cally for surface conditioning in deep hole drilling parallel to machining. This involves metrological and simulation-based approaches for identifying thermo-mechanical process conditi-ons in both BTA and ELB process. Ways for obtaining process data both with sensor technology used in-situ and with FEM simulations performed concomitantly are investigated. These data form the basis of a deep hole process control. The second part presents the work and the results on single lip deep hole drilling. © 2021, VDI Fachmedien GmBbH & Co.. All rights reserved.

The BTA deep hole drilling process is analysed to determine the relationships between process-structure and residual stress as a function of surface conditioning during the machining process. The residual stresses, the hardness and structural changes in the microstructure are used as indicators for a following process control in order to generate an improved component service life or reliability. In the first tests, the deep-drilled samples are examined with regard to residual stresses, bore tolerances, microstructure and hardness in the sub-surface zone. Furthermore, the specimens will be subjected to a heat treatment to establish a stress-free microstructure as a reference state for the magnetic residual stress measurement. © 2020 The Authors.

In machining, the thermal load significantly influences the tool wear and the workpiece quality, thus limiting the productivity. Therefore, a new experimental setup for the high-speed measurement of the rake face temperature in orthogonal cutting without substantially affecting the chip formation was developed. The investigations focus on the influence of different rake face preparation methods and cutting parameters on the temperature of the rake face, measured in the immediate vicinity of the cutting edge. The presented results significantly improve the understanding of the process and provide new insights for the tool development and the validation of cutting models. © 2020 CIRP

In this study, the influence of cutting speed and feed rate on surface integrity in Boring Trepanning Association (BTA) deep hole drilling of AISI 4140+QT is investigated. Microstructure and micro-hardness in the subsurface zones of bores are analyzed, using metallographic and micromagnetic methods. It was found that when using high feed rates and cutting speeds, white etching layers (WEL) form at the surface of the bores. These layers are up to three times harder than the substrate material and have a maximum thickness of approx. tWEL ≈ 12 μm. WEL were usually followed by a transitional layer, so that elevated hardness was observed until a depth of dsurf = 35 μm below the surface. Magnetic Barkhausen noise (MBN) analysis proved to be applicable for the fast and reliable detection of WEL. The presented results contribute to gaining a deeper understanding of the complex interrelations between the design of the BTA process, the resulting microstructure in the machined component and the properties of the conditioned surface. Based on discovered correlations, a dynamic process control will be developed for BTA deep hole drilling, which will allow reliably tailoring surface integrity of components to specific demands, like an optimized fatigue performance. © 2020 Walter de Gruyter GmbH, Berlin/Boston 2020.

The relationship between the cutting speed, the feed, the resulting process forces during the BTA deep hole-drilling process and the functional properties in the bore sub-surface zone of AISI 4140 and AISI 304 L is analysed. Due to the asymmetric design of the drill head radial forces occur which are supported through guide pads on bore surface. The result is an inner force flow inside the tool that affects a self-guiding effect during the drilling process. Due to this process the bore (sub-)surface zone is impinged with thermal and mechanical loads resulting in hardening, structural changes in microstructure and the occurrence of residual stresses, which can influence the fatigue strength, service life or reliability of the part. Residual stresses are measured using the magnetic Barkhausen noise method. Understanding the relationship between the process forces and functional properties in the bore sub-surface zone is essential for a following process control in order to generate defined bore sub-surface zones. © 2020 The Author(s).

The MERCUR research project Pr-2017-0003 "Analysis of the product development process in the combination of additive and subtractive manufacturing processes for the manufacture of multi-material products" combines different manufacturing and post-treatment processes to connect the respective advantages. The additive fused deposition modeling (FDM) together with the anisotropic component properties resulting from the process are used in this investigation. The influence of chemical and mechanical post-treatment steps on these properties will be investigated. © Carl Hanser Verlag.

The machining of hardened steel is characterized by a segmented chip formation. The segmentation is often referred to thermoplastic instabilities or material damage. In this paper the mechanisms for shear band initiation are analyzed and discussed through experimental and simulative investigations. The hardened low alloy steel 51CrV4+Q is machined in an orthogonal cutting process. The chips reveal signs of ductile damage and white layer shear bands. By Finite-Element chip formation simulations the conditions within the primary shear zone are analyzed and based on this an appropriate ductile fracture model for the simulation of shear bands and segmented chips is presented. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of The 17th CIRP Conference on Modelling of Machining Operations

The heat treatment has a major impact on the mechanical properties of steel alloys and therefore on the condition of a machining processes. In this paper, the low alloy steel 51CrV4 with different heat treatments is investigated in terms of its mechanical properties under high dynamic conditions using a Split Hopkinson Pressure Bar (SHPB) and by means of orthogonal cutting tests. The latter provide a detailed insight in the ongoing processes during chip formation by analyzing the present microstructure of the generated chips. Furthermore, the obtained data from the SHPB tests is used as an input for material models applied for the simulation of chip formation with the Finite-Element-Method. The results reveal fundamental differences in the chip formation mechanisms between the differently heat treated workpiece materials. © 2017 The Authors.

WC-W2C iron based cermet coatings are widely used in the field of wear protection. In surface engineering, machine hammer peening (MHP) is a novel surface treatment technology, which enhances the surface properties, especially for surfaces in tribological contact. In this study, the wear behavior of peened WC-W2C FeCrCMnSi arc sprayed coatings is characterized and compared to conventional coatings under as-sprayed conditions. The resulting strain hardening effects were measured by mechanical response using nanoindentation. In addition, residual stresses at the surfaces were determined using X-ray diffraction and the sin2ψ method. © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.

Internal traverse grinding with electroplated cBN wheels using high-speed process conditions combines high material removal rates and a high surface quality of the workpiece in one single grinding stroke. In order to capture the macroscopic and mesoscopic thermo-mechanical loads onto the workpiece during internal traverse grinding, numerical simulations are conducted at the two scales. This results in a hybrid approach coupling two finite element models with a geometric kinematic simulation. The article focuses on the influence of multiple grain engagements onto a surface layer region using a two-dimensional chip formation simulation. © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.

In order to fully utilize a machine tool and to identify its natural frequencies, modal analysis can be performed. This provides information about the vibration characteristics of the machine structure during the machining process. In this article, an optimization of experimental modal analysis will be presented. The classical measurement chain to perform a modal analysis is always based upon the principle of excitation, signal transmission, signal detection, and signal analysis of results. The conventional method, wherein the excitation is effected by a modal hammer and the signal detection is done by an acceleration sensor, is now replaced by a process in which excitation is achieved via an automated modal pendulum and the signal detection by means of laser or acceleration. Within the framework of this research, there are two key elements that will be discussed in detail. The first element includes the motivation for the development of the pendulum and the aspired improvements of the new model. A prototype is tested and its performance is valuated. The second key element represents an experimental analysis of the performance, including a comparison between the conventional modal hammer and the developed modal pendulum. Here it should be shown that the repeatability of the hammer strikes of the pendulum is significantly higher than that of the conventional hammer. In addition, the adjustability of the force excitation is to be ensured. © 2014 The Authors. Published by Elsevier B.V.

Presently, the main mechanism for phase transformations in machining of steels is not absolutely clear and is still subject to research. This paper presents, three different approaches for modeling phase transformations during heating in machining operations. However, the main focus lies on two methods which can be classified into a stress related method and a thermal activation related method for the description of austenitization temperature. Both approaches separately showed very good agreements in the simulations compared to the experimental validation but were never compared in a simulation. The third method is a pre-calculated phase landscape assigning the transformation results based on a micro-mechanically motivated constitutive model to the workpiece in dependence on the temperature and strain history. The paper describes all three models in detail, and the results are also presented and discussed. © 2015, German Academic Society for Production Engineering (WGP).

Due to friction and material deformation in the shear zone, workpieces in NC-milling processes are subjected to heat input and thermal loading. Ongoing geometric changes as well as time-varying contact and cutting conditions result in an inhomogeneous temperature field that is constantly in flux. Such thermally loaded workpieces often exhibit complex and transient thermomechanical deformations, which may result in erroneous material removal with respect to the desired shape. In order to meet critical manufacturing tolerances, it is therefore necessary to avoid and compensate these effects. Predicting the deformation exhibited by a thermally loaded workpiece is a problem of linear thermoelasticity, which can be solved by use of the finite element (FE) method. A prerequisite to this is the accurate calculation of the temperature field that results within the workpiece material during the course of the milling process. Although the FE method may be used for this as well, the practical application to realistic milling processes is limited due to the required computational resources. This paper presents a fast geometric process simulation for the prediction of cutting forces, heat input and thermal loading in dry NC milling. The temperature field of the workpiece is continuously updated, such that it is possible to determine the temperature of any material point at any point in time of the milling process. Individual models comprising the simulation system are described in detail, along with the experiments that are required to calibrate them. The accuracy of the geometric process simulation is validated by comparison with experimental data for a non-trivial milling process. © 2015, German Academic Society for Production Engineering (WGP).

In the machining of large structural components such as those used in the construction of airplanes, most of the material is removed, while at the same time, a large amount of heat is inserted into the workpiece. During roughing operations in dry milling, the thermal load can lead to workpiece distortions that result in a violation of the manufacturing tolerances of the finished part. Although the variation of process parameter values and milling strategies can influence and significantly reduce the thermal loading, effects such as chatter or limitations of the machine also have to be taken into account. In this paper, the interrelation between process parameter values and dynamic tool behavior is investigated, as both have a large influence on the thermal loading of the workpiece. Milling with a high material removal rate typically results in a lower heat input into the workpiece, but this approach is limited and may lead to process instabilities, manifested in chatter of the tool. In this paper, a basic experimental analysis for the influencing process parameters feed per tooth fz, axial immersion ap, radial immersion ap, and spindle speed n is conducted, and the effects of chatter on the thermal loading of the workpiece is analyzed by experiment. A geometric simulation of the milling process is utilized in order to reduce the experimental effort, as well as to to increase the knowledge of the heat input mechanisms. The simulation system is able to calculate the transient dynamic behavior of the tool with high accuracy and can therefore be used to predict the process stability in advance. Additionally, a thermal model is used to simulate the temperature of the workpiece material during the dry milling process. © 2015 Authors. Published by Elsevier B.V.

In this chapter, applications of computational intelligencemethods in the field of production engineering are presented and discussed. Although a special focus is set to applications in machining, most of the approaches can be easily transferred to respective tasks in other fields of production engineering, e.g., forming and coating. The complete process chain of machining operations is considered: The design of the machine, the tool, and the workpiece, the computation of the tool paths, the model selection and parameter optimization of the empirical or simulation-based surrogate model, the actual optimization of the process parameters, the monitoring of important properties during the process, as well as the posterior multicriteria decision analysis. For all these steps, computational intelligence techniques provide established tools. Evolutionary and genetic algorithms are common networks. Fuzzy logic represents an intuitive way to formalize expert knowledge in automated decision systems. © Springer-Verlag Berlin Heidelberg 2015.

The composition of different materials and their specific properties like tensile strength and toughness is one way to achieve workpiece characteristics which are tailored to the later application. Another approach is the subsequent local heat treatment of workpieces made of homogeneous materials. However, both ways are costly and go along with several subsequent process steps. Therefore, mono-material workpieces which were manufactured by thermo-mechanical forming processes may provide such tailored properties in the form of functional gradations. Furthermore, the process chain is shortened by the combination of forming and heat treatment, but nevertheless machining processes are still needed for proper workpiece finish. This puts the challenge of varying process conditions due to hardness alterations within a single process step, e.g. turning. In addition to experimental investigations simulative analysis techniques are desired to evaluate mechanical as well as thermal loads on tool and workpiece. In the case of FE-based microscopic chip formation simulations proper material behaviour needs to be determined with respect to material hardness. This paper describes the approach of fitting Johnson-Cook material parameters as a function of workpiece material hardness. In order to achieve realistic stress states within the process zone, this approach considers the yield strength as a linear function of the hardness. It is shown how the hardness influences the cutting conditions and how the Johnson-Cook parameters are identified. Then these parameters are validated in three-dimensional simulations of exterior dry turning by comparison of simulated process forces and chip formation to experimentally achieved ones. © 2014 Trans Tech Publications, Switzerland.

In the first part of the presented work the results of research regarding integration of acoustic emission sensor technology during the machining of material compounds will be depicted. Extruded aluminium alloys (AW6060) provide as a matrix material, while functional elements in form of conductive paths and reinforcing elements (1.4310) are embedded. The aim of this research is to detect material transitions precisely and to generate an automatable process controlling. To analyse the acoustic emission signals a real-time capable system is used. The frequency spectrum as well as the root mean square-value will be depicted for the experiments. The second part of the work outlines the development and testing of an automated modal impact hammer to provide an impulse based structural excitation source for experimental modal analysis. The use of this pendulum is to increase the repeatability, to enable the variability of the excitation force and to prevent so called double hits. Therefore it is well suited for frequency response measurements of tools. With these measured data, stability charts can be simulated in further steps. With this the milling tool can be used in the optimum range of parameters. (C) 2014 Elsevier B.V.

This paper is focused on the virtual five-axis milling of light weight components with respect to joining elements and reinforced as well as functionally enhanced structural parts. The underlying concept here consists of a geometrical model representing the time and space discretized milling process and its ever changing engagement situations. This geometric information is then used to calculate physical process properties like forces and temperatures, which are necessary for optimization tasks and for the reliable prediction of process results. Additionally a decision-tree based process planning system is presented, supporting the user in maintaining knowledge from real and virtual milling processes. © 2014 Elsevier B.V.

This work presents an efficient finite element based scheme for the prediction of process properties and especially the material condition of workpiece surfaces after turning. This is achieved by using a database generated with the help of a micromechanically motivated material model - capable of simulating interactions of phase transitions and plasticity - for the efficient post-processing of a macroscopic thermo-mechanically coupled finite element simulation of the turning process. This modelling technique is applied to the martensitic part of a functionally graded workpiece which is produced by thermo-mechanically controlled forging processes. Those workpieces provide locally varying material conditions, which are tailored to the later application. The resulting pre-products have to be turned in order to achieve the desired final workpiece geometry and surfaces. Such processes strongly affect material properties such as hardness and ductility. A deterioration of the functionality of the gradation, i.e. the martensitic surface properties, may occur by generation of residual tensile principal stresses which can occur accompanied by white layer formation. These deteriorations can be avoided by adjusting the process parameters appropriately. Especially the cutting speed is supposed to be on a low level (vc < 80 m/min) to avoid thermally driven formation of a white layer and the generation of tensile residual stresses. It is shown how finite element simulations can give insight into the material interactions and thereby facilitate the support of the process parameter adjustment in order to support efficient and reliable part production in industrial applications. © 2014 Elsevier B.V.

In the field of machining technology the vibration of the system machine, tool and workpiece during processing is the limiting factor of productivity. Therefore the process monitoring of vibration today plays an important role for the real time monitoring of machining processes, as well as for the optimization of simulation models. For monitoring workpiece vibrations, different kinds of strategies are in use. As the piezoelectric acceleration sensors were already field-tested at the department of machining technology (ISF), the use of Contact Emission-Sensors, which are customarily used for stringed instrument tuning, could pose an effective alternative strategy. Proving the possibility of using those sensors, could simplify the future choice of the process monitoring strategy for different machining operations and has cost saving potentials, due to an abbreviated measurement chain. Within this work the workpiece vibration during a 5-axis milling process were detected simultaneously by two monitoring strategies. In these experiments, the detection of vibration by a piezoelectric acceleration sensor was chosen as the reference strategy. The second technique deployed was the measurement of the contact-emission with a common contact microphone. On a milling machine for five-axis simultaneous machining, aluminium shafts were fixed in a three-jaw chuck one-sided and processed with an end mill. The geometry of the milling pockets was varied in the different processing sessions, as well as the feed parameters, in order to obtain both stable and unstable processing. The vibration measurements resulting from the two monitoring strategies were compared in form of time signal and frequency spectrum as well as in the combined form of a 3-dimensional waterfall diagram. Monitoring structure borne noise is an easy, cost-efficient alternative to measures with an acceleration sensor. Delivering reliable results concerning the vibration frequencies, which are multiples of the spindle rotation frequency, this method could be applied for process monitoring. The experiments have shown that the location of the Contact Emission-Sensors has major impact on the quality of results. To implement the Contact Emission-Sensors for this kind of measurements, the sensor must be positioned close to the place of vibration origin taking into account both damping characteristics of all components involved and the way of workpiece clamping.

In production engineering, there are several applications where the geometry of a designed workpiece has to be modified, e.g., optimization of forming tools during springback compensation in sheet metal forming. In general, the modified shape of the workpiece is given as a mesh and has to be converted to a parametric representation by surface reconstruction before manufacturing. In this paper, a new approach for obtaining small shape modifications by direct deformation of the NC programs is presented. In an iterative process, the CAM data is modified by a free-form deformation and is verified by a milling simulation so that the modified workpiece can be manufactured directly on the basis of the original CAD/CAM data without surface reconstruction. © 2012 Elsevier Ltd. All rights reserved.

The main goal in the design of milling processes for components in the aerospace industry is the optimization of productivity while maintainig process stability. These two goals can be conflicting, especially if long tools are required, which are particularly susceptible to vibrations. In order to reduce the number of costly experiments, simulation-based approaches can be used to evaluate generated NC programs beforehand. In this paper, a modeling approach for the detailed simulation of engagement conditions, process forces, and dynamic tool behavior is used to detect instable process conditions. Additionally, an algorithm is presented to change the axial immersion in order to avoid regenerative chatter during milling. To demonstrate the effectiveness of the simulation approach and of the compensation strategy, a comparison is shown between experimental and simulated results and between the workpiece generated by the original and the optimized NC programs.

During roughing in NC milling, heat is introduced into the workpiece. For the manufacturing of large structural components, a constantly changing temperature field is created due to the rapid movement and the varying contact conditions between tool and workpiece. Therefore, significant deformations can cause form errors that lead to rejects in the production process. In this paper, a simulation system for the prediction of transient workpiece temperatures is presented. In order to calibrate the system, simple experiments have been conducted, and a model for the introduction of energy into the workpiece via cutting has been developed. The newly developed cutting-energy input model makes it possible to perform fast simulations. Therefore, it can be used to perform simulations of the thermoelastic workpiece deformations during milling of complex shaped parts. Copyright © 2013 Elsevier B.V.

This article presents research work on the influence of the design characteristics of the joint partner elements and especially of grooving and pocketing on the tensile and torsional strength of tubular joints produced by hydraulic expansion when tubes are made of aluminum EN AW-6060. In general, joining of tubular elements can be performed by different methods, but internal expansion presents an interesting alternative to other methods like welding and mechanical forming processes. Commonly, hydraulic expansion is used for the manufacturing of heat exchangers. As a result, time effective and resistant joints must be produced in particular when applying hydraulic expansion in the manufacturing of lightweight structures. © Taylor and Francis Group, LLC.

This paper is focused on the drilling of bore holes with high length-to-diameter ratios and diameters less than 2 mm which are needed, for example, in medical and automotive applications. In the presented research, the influence of cutting data and tool design on tool wear and chip formation has been analysed. First the experimental set-up is described followed by an in-depth process analysis of the single-lip deep hole drilling process under investigation. The next section deals with a process combination, where laser and mechanical drilling are combined in order to improve process reliability and productivity. © 2012 CIRP.

The highest geometric precision in a milling simulation can be achieved by using a CSG-based workpiece model. This allows the prediction of cutting forces, process dynamics and surface structures. To further improve the accuracy of the predictions, a new global CSG model is proposed to replace the previously used local CSG model without any negative impact on the runtime of the simulation. In addition, the runout of the tool has to be included in the modeling process to obtain correct results. In this paper, the new modeling techniques and their experimental validation are presented. © 2012 The Authors.

During the grinding of hard materials using cylindrically and spherically shaped mounted points - like for the machining of complex forming tools with abrasive-wear-resistant coatings - the process force is an important factor influencing the accuracy of the machining outcome. A simulation-based prediction of these forces could be used to adapt the tool path and, thereby, to keep the grinding forces at a low level. In this paper, a simulation system based on the modeling of each grain of the grinding tool and the validation of this simulation model are presented. © 2012 The Authors.

Experiments on dry face turning of functionally graded heat treatable steel are conducted. The workpieces have a hardened zone of approx. 60 HRC and a non-hardened zone of approx. 30 HRC. PCBN tools are used with different feeds, cutting speeds and depths of cut. Measurements of residual stresses in the surface layer reveal compressive stresses in the hardened zone and tensile stresses in the non-hardened zone. These experimental observations are compared with the results of representative simulations of the cutting process. A large-deformation thermo-elastoviscoplastic material model is used and the geometry of the cutting tool is precisely reflected by the finite element discretisation. To predict the overall response, an adaptive remeshing scheme and full thermo-mechanical coupling is accounted for. Moreover, measured residual stresses are incorporated as initial conditions within the simulation. © 2012 Published by Elsevier Ltd.

Light-metal extrusions are widely used as frame-structure elements. Joining these profiles via screw coupling is a challenging task due to the small wall thickness of the extrusions and the missing accessibility within a frame structure. The combination of flow drilling and thread forming offers a possibility to cope with this task. These processing techniques allow the manufacture of stable threads in thin-walled structures with the profile accessible from one side only. Nowadays, aluminium profiles can be continuously reinforced through composite extrusion. Mechanical properties, like increased tensile strength compared with homogeneous profiles, make reinforced profiles preferable for applications such as safety-relevant components. However, the reinforcement can seriously affect machining processes as well as the machining results. Therefore, the flow-drilling operation, the thread-forming operation, and the process results have been analysed in detail with a new, difficult-to-machine material combination, namely steel-wire-reinforced aluminium extrusions. The crucial factor when machining lightweight extrusions are the forces acting perpendicular to the thin walls, so the influence of the reinforcement and the processing parameters on the feed force during flow drilling is presented. To examine the effect of the reinforcement on the thread-forming result and to quantify the benefit of flow drilling, the threads are stressed with a defined tensile load until failure.

The layout of temperature control systems for moulds is decisive for the performance and stability of the production process. A design and optimisation approach for temperature control systems is introduced, coping with geometric constraints and complex thermal dependencies and allowing a significant reduction of manufacturing costs. Five-axis milling processes are increasingly used for the production of moulds in order to achieve high surface qualities and low manufacturing times. The CAM-programming required for the milling of free-formed surfaces in this field is complex and error-prone. An approach is shown, which automatically generates five-axis NC-paths from existing error-free three-axis paths. Copyright © 2011 Inderscience Enterprises Ltd.

In most cases the simulation of temperature distributions in machined workpieces is carried out by moving a heat source along a predefined workpiece model within a commercial FEM-system. For performance reasons, the material removal is often neglected or performed by removing small predefined parts of the workpiece. Furthermore, the heat source often has a constant heat flux and therefore it is not dependent on the current tool engagement. In this paper we present a voxel-based finite difference method for the thermal behavior of the process-state dependent workpiece, which is integrated into the milling simulation system NCChip, developed at the ISF. This simulation is capable of modeling the cutting forces along any arbitrary NC-path. Since the tool rotation and the cutting edges in this time domain simulation are divided into discrete angle steps and cutting wedges respectively, the thermal energy that is applied to the workpiece at each time step and at each cutting wedge can be computed as a fraction of the corresponding cutting work. In this way, the correct heat is introduced to the workpiece exactly at the current contact zone of the tool. © (2011) Trans Tech Publication.

Newly developed functionally graded workpieces made of AISI 6150 (51CrV4), pose great challenges to the machining process due to the combination of different material properties (e. g., hardness) within one workpiece. A material model including more information than experimentally identified stress-strain curves for different temperatures is necessary to model the process more realistically. Therefore, the Johnson-Cook material model has been implemented for three-dimensional turning simulations within the Finite Element software DEFORMTM 3D. This paper outlines the adopted method to modify the parameters of the Johnson-Cook material model for two-dimensional and three-dimensional FE-simulations in order to take material hardness into account. The primary objective was to improve passive and feed force computation by using this modeling approach, as it was observed that common material modeling showed large deviations of the feed force and passive force from the measured force components. The calculated feed force and passive force, as well as the cutting force, are validated experimentally. In conclusion it is shown that the application of the Johnson-Cook material model reveals more valid results for modeling the turning of workpieces with varying hardness values. © 2010 Springer-Verlag France.

By manufacturing structured functional-surface coated composites using suitable materials, the properties of components? surfaces can be specifically matched to their requirements which the specified substrate material can not, or can only partially, fulfil. In conventional process chains, thermal spraying and structuring by milling are independent stages in the component?s final processing phase. Using the procedure introduced here, thermal spraying is to be directly integrated into the high pressure die casting process. In this way, a manufacturing procedure for coated castings with functionalized surfaces is realised which, as far as possible, eliminates the finishing operation of coated cast parts. In contrast to conventional coating processes, the coating-layer is not applied to the component but to the casting mould or to the corresponding inserts and is transferred to the component as a structured functional-surface during each cast. Transferring this type of coating from the tooling surface to the casting; which is also referred to as transplant coating, requires a narrow process-window with respect to the coating adhesion to both the tooling surface and the cast part. The coating adhesion at the tooling surface must be high enough such that the coating is not detached during either the coating or the mould filling processes, but also low enough to be completely detached from the tooling during mould stripping and be able to be removed together with the cast part. For this reason, the initial priority of the current investigations is to obtain a specific coating adhesion by adapting both the tooling surface, which is manufactured by milling, as well as the coating systems and the atmospheric plasma spray?s parameters for the most precise moulding of such plasma sprayed structures. Furthermore, investigations are introduced on forming composites from the cast material and the coating materials and results are presented of preliminary casting tests for transplanting thermally sprayed coatings onto aluminium and magnesium alloys during high pressure die casting. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.