Zusammenfassung Bei Zerspanungsprozessen wird die mechanische Energie in den Scher- und Reibzonen zwischen Werkzeug und Werkstück weitgehend in Wärme umgewandelt. Dadurch entstehen außerordentlich hohe mechanische und thermische Spannungen, die zu einer thermisch bedingten Verschiebung der Werkzeugspitze und damit zu einer geringeren Bearbeitungsgenauigkeit führen. Während der Zerspanung verursacht die Prozesswärme einen erheblichen Wärmeeintrag in das Werkzeug und sein Spannsystem.

During the grinding process, a large proportion of the cutting energy is converted into heat. Since not all the heat can dissipate into the cooling lubricant, the material structure of the workpiece can suffer from thermally-induced damage, which has a negative effect on component quality. The generation and distribution of heat is influenced by the change of the grinding wheel topography due to wear. A means of wear analysis for grinding wheel topographies has been developed to describe and explain the wear condition of the grinding wheel and is presented in this paper. For this purpose, creep feed grinding investigations were conducted on bearing steel with electroplated cBN grinding wheels with two different grain specifications. Static and kinematic topography parameters describing the topography changes of the grinding wheels due to wear and their influence on the thermo-mechanical load were investigated in the tests. The static parameters such as the Abbott-Firestone curve or the wear volume make it possible to quanitfy the wear mechanisms. By determining the kinematic topography parameters such as engagement areas or angles, the change in engagement conditions could be derived, which is important for determining the heat flows into the workpiece.

The smoothed particle hydrodynamics (SPH) is applied to model the single-grain diamond scribing of the silicon carbide fiber reinforced silicon carbide (SiCf/SiC). Experiments of diamond scribing on SiCf/SiC were performed with three parameters: fiber orientation, depth of cut, and speed of cut. The scribing force and 3D shape diamond tip was measured. The SPH simulation based on JH-2 material model of the SiCf and SiC matrix as well as the experimental modeling is performed. Comparison of SPH-predicted and experimentally measured force identifies parameters for the JH-2 work-material and SPH modeling of SiCf/SiC for accurate prediction of diamond scribing force.

A large part of the energy introduced during grinding is converted into heat. As not all the heat can be dissipated by the cooling lubricant, thermally induced displacements in machine components occur. These displacements have a negative influence on the component quality. Since the grinding wheel topography changes during the grinding process due to wear, the wear mechanisms of grain splintering, grain breakage as well as abrasion were identified and quantified. In addition, their effect on heat generation was investigated. To predict the wear mechanisms, a Finite Element (FE) simulation model was developed that determines the grain shape change considering the cleavage planes in the grain. Three-dimensional real cBN grain geometries were used for the simulation of a single grain engagement in the workpiece of the 100Cr6 steel. In the presented model, the orientation of the cleavage planes is varied and their influence on the wear mechanisms as well as the resulting forces is investigated. In addition, empirical tests were conducted in order to adjust the model. The simulation showed that a cleavage plane variation resulted in stronger crack propagation when the cleavage plane was oriented away from the workpiece and when the distance of the cleavage plane from the point of application of the load was smaller.

Ein großer Teil der beim Schleifen erzeugten Energie wird in Wärme umgewandelt. Da nicht die gesamte Wärme durch den Kühlschmierstoff abgeführt werden kann, können thermisch bedingte Bauteildefekte auftreten. Die Wärmestromaufteilung wird durch die verschleißbedingte Veränderung der Schleifscheibentopografie beeinflusst. In dieser Arbeit wird eine Methodik zur Entwicklung eines Verschleißmodells vorgestellt, das die verschleißbedingte Topografieänderung von galvanisch gebundenen cBN-Schleifscheiben erklären und vorhersagen kann. A large amount of the energy generated during grinding is converted into heat. As the cooling lubricant cannot dissipate all of the heat, thermally induced component defects can occur. The heat flux distribution is influenced by the wear-related change in the grinding wheel topography. This paper presents a method for developing a wear model to explain and predict the wear-induced topography change of electroplated cBN grinding wheels.

Dieser Beitrag stellt die Ergebnisse von Verschleißuntersuchungen beim Einkornritzen mit CBN-Körnern dar. Der Fokus der Forschungsarbeit liegt auf der Identifizierung und Quantifizierung der Verschleißmechanismen in Abhängigkeit von den Prozesseinstellgrößen und den Korneigenschaften. Es werden charakteristische Phasen der Verschleißentwicklung identifiziert, die eine Zuordnung der Verschleißmechanismen Mikrobruch, Makrobruch und Abrasion zulassen.   The content of the paper is the presentation of the results of wear investigations on CBN grains used in single grain scratching. The focus of the research work is on the identification and quantification of the wear mechanisms as a function of the process parameters and the grain properties. Characteristic phases of wear development were identified, which allow an allocation of the wear mechanisms micro fracture, macro fracture and abrasion.

Dieser Beitrag stellt die numerische Modellierung des CBN-Kornverschleißes beim Einkorneingriff mit der Finite-Elemente-Methode vor. Es wird erstmalig eine dreidimensionale Verschleißsimulation unter Verwendung realer CBN- Korngeometrien im Korn-Werkstückkontakt durchgeführt. Dazu werden drei reale Korngeometrien simuliert, um die Verschleißmechanismen des realen Korneingriffs abzubilden. Abschließend werden die Simulationsergebnisse mit empirischen Untersuchungen verglichen.   This article is about the numerical modeling of CBN grain wear in single grain engagement using the finite element method. A three-dimensional wear simulation using real CBN grain geometries in grain-workpiece contact is conducted for the first time. For this purpose, three real grain geometries are simulated to represent the wear mechanisms of the real grain engagement. Finally, the simulation results are compared with empirical investigations.

A large amount of the energy produced during grinding is converted into heat. Since not all of the heat can be dissipated by the cooling lubricant, thermally induced displacements in machine components occur, which has a negative influence on the component quality. The generation and distribution of heat is influenced by the change of the grinding wheel topography due to wear.Therefore, the wear mechanisms of grains were identified and quantified and their effect on heat generation was investigated. For this purpose, creep feed grinding investigations on bearing steel were conducted with electroplated CBN grinding wheels with different grain specifications.

The quantification of the heat flow distribution in the cutting zone is still an unsolved problem from an analytical as well as experimental perspective. Yet the heat flows into the tool and the time-variant temperature fields in the tool significantly influence the tool wear rate. This publication shows the results of a model extended measuring approach in order to monitor as well as investigate heat flows and their partitioning in the milling process under dry conditions. Therefore, the cutting power in the process was measured by means of a dynamometer as well as the temperature in the tool by an embedded thermocouple. The time response of the embedded thermocouple was accounted by an analytical time response function. By further data post processing of the temperature, the heat flow into the tool was inversely determined by comparison of the measured temperature trend at a distinct point with an analytically modeled, transient temperature as a solution of the heat conduction equations by a Green’s function. As input into the analytical model, an iteratively determined partition of the measured time-variant cutting power signal was used. The results showed a decreasing heat partition into the tool with rising cutting velocity. The introduced approach is a valuable tool not only to determine the heat partition in the milling process but also to understand and monitor the comprehensive thermo-mechanical conditions in the cutting zone. Understanding and monitoring thermo-mechanical conditions in the cutting process finally enable the exploitation of economic and ecologic process potentials.

Cold forming, particularly forward impact extrusion, is used for mass production of steel components. To ensure robust forming processes, the workpieces are usually phosphated and then soaped as well as mineral oil-based lubricants are used. As these lubricants are often harmful to the environment and health, alternative approaches are to be investigated from an ecological, economic and legislative perspective. To achieve dry, lubricant-free cold forming of steel, two approaches are being pursued here. The tool-sided approach focuses on self-lubricating hard coatings, which are deposited on the forming tools by means of physical vapor deposition (PVD). The developed coating system CrAlN+Mo:S is synthesized in an industrial coating unit by a hybrid sputtering process, which combines direct current (DC) and high power pulsed magnetron sputtering (HPPMS) technology. The coating consists of a hard matrix CrAlN which is modified by Mo and S to provide friction reduction due to the in situ formation of MoS2 reaction layers under tribological load. The workpiece-sided approach focuses on the surface structuring by shot peening with various peening materials and particle shapes. In order to evaluate the influence of the self-lubricating tool coating CrAlN+Mo:S and the various workpiece topographies, dry full forward impact extrusion tests were carried out in an industrial scale with coated and uncoated tools. On the one hand, a one-shouldered die geometry and on the other hand a two-shouldered die geometry were tested. The field trials reveal that for both die geometries, the tool coating significantly reduces the punch force and the wear compared to the uncoated dies. Depending on the workpiece topography, it was shown that a smoother surface leads to reduced adhesive wear. Furthermore, it was proven that the dies with an opening diameter of D = 31.4 mm and an outlet diameter of d = 20.7 mm could be coated continuously over a length of l = 50 mm on the entire inner surface. After the dry field trials, the CrAlN+Mo:S coating remained completely intact. Hence, the developed coating system CrAlN+Mo:S exhibits great potential to conduct dry, lubricant-free cold forming of steel at industrial scale.

The machining process has a major influence on the microstructure and the residual stresses of the manufactured surface and it’s final functionality. This functionality of surface integrity is of particular interest in safety critical aero engine parts made of temperature resistant super alloys such as nickel-chromium-based alloys. Besides the high tool wear, the machining of such materials is in particular challenging with regard to process induced microstructure alterations and the formation of low toughness and high hardness white layers. The current publication shows an experimental study and affiliated methodology in order to examine the influence of the process state conditions on the surface integrity, with regard to localized temperatures and forces causing white layer as well as residual stresses. On the experimental side a tailor made orthogonal milling setup was used in order to evaluate the transient temperature fields occurring in the workpiece together with the fluctuating process forces acting on its surface. This setup included a synchronized dynamometer, a thermal camera as well as a ratio pyrometer. The cutting forces and cutting normal forces under known engagement conditions were calculated from the transformed Cartesian dynamometer measurements and the measured cutter rotation angle. An evaluation of the surface integrity alteration was finally carried out analyzing the surface microstructure by light microscopy as well as residual stress measurements by X-ray diffraction.

Processes in cold forming are accompanied by high process loads, which are reduced by means of lubricants. Lubricants are ecologically and economically questionable and increasingly restricted by legislation. In a current research project, the substitution of lubricants by coatings for tools and texturing of workpieces in a full forward extrusion process is investigated. Exact friction values of combinations of texturing and coating are necessary to investigate the process numerically and experimentally. For solid forming, the ring compression test has proven to be a valid analogy test for determining the friction factor. In this paper, the latest investigations concerning the dry tribological contact of coated and uncoated tools with different textured workpiece surfaces are shown in the ring compression test. The flow and adhesion behavior of the active partners under loads of cold forming are investigated. Furthermore, the friction factor for numerical investigations of full forward extrusion process is determined.

Tools in cold forging processes experience high loads. In order to reduce the process loads, solid and liquid lubricants are used. The use of lubricants is disadvantageous due to ecological, economical, and legislative reasons. Novel approaches in cold forging aim at the use of ecologically benign lubricants or avoiding the usage of lubricants completely. This paper focuses on the substitution of lubricants in cold forging by surface textures on workpieces and self-lubricating coatings on tools. The potential of surface textures on workpieces and self-lubricating tool coatings to reduce friction and wear in dry forging was demonstrated in preliminary work using analogy experiments. After analogy tests under dry tribological boundary conditions have shown positive results in preliminary work, dry full forward extrusion tests were performed in this work. Firstly, the focus of the investigations was on feasibility. Secondly, the potentially best combination with regard to friction and wear reduction was selected. Thirdly, in addition to force profiles, the surface of cold forging dies was studied by means of SEM. At the same time, the processes were supported by a validated numerical FE process simulations with the simulation software Forge NxT 2.1. The dry full forward extrusion experiments were successful, because the specimens were extruded until the final point and could be ejected without failure. It was observed that the highest wear of the dies occurred not in the region with the highest tool load but in the region with relatively low loads. Furthermore, it was shown that no wear model suitable for cold forging exists so far.

Large-scale cyber-physical systems such as manufacturing lines generate vast amounts of data to guarantee precise control of their machinery. Visions such as the Industrial Internet of Things aim at making this data available also to computation systems outside the lines to increase productivity and product quality. However, rising amounts and complexities of data and control decisions push existing infrastructure for data transmission, storage, and processing to its limits. In this paper, we exemplarily study a fine blanking line which can produce up to 6.2 Gbit/s worth of data to showcase the extreme requirements found in modern manufacturing. We consequently propose integrated data processing which keeps inherently local and small-scale tasks close to the processes while at the same time centralizing tasks relying on more complex decision procedures and remote data sources. Our approach thus allows for both maintaining control of field-level processes and leveraging the benefits of "big data" applications.

Highly iterative product development is a promising approach to continuously involve customers in development and to meet global challenges such as short product life cycles and increasing variant diversity. In this context, the planning of production technologies, which takes place in parallel to product development, faces the challenge of processing uncertain product information in early planning phases. This is due to the frequent change of the required product characteristics while the product is being developed. Technology planners must therefore adapt the effort of their planning methods to the existing information uncertainty. This paper presents a new methodology for processing uncertain information from various information sources in technology planning. Firstly, individual information are modelled using fuzzy sets. Afterwards, a new method based on the Dempster–Shafer theory of evidence is presented, which enables an aggregation of individual information from different sources considering their uncertainties. The aggregated information regarding the product characteristics are used to determine the product maturity in the current iteration loop of the highly iterative development process. Finally, the user of the methodology selects a suitable technology planning level based on the prevailing product maturity.

This paper presents an analytical model to analyze the energy partitioning in grinding based on the process parameters and the grinding wheel topography. Therefore, the energy-partitioning model of Demetriou und Lavine is coupled with a kinematic topography analysis, which predicts the kinematic engagement conditions along the contact zone using measured grinding wheel topographies. The coupling of both models allows to evaluate grinding wheels of different specifications with regard to their thermal behavior in the grinding process without preliminary experimental investigations for the first time. With the developed model, the influence of an electroplated CBN grinding wheel topography on the resulting temperature field in the workpiece external zone is investigated in creep feed grinding.

Industrial standard for introducing compressive residual stresses and improving the fatigue life of compressor blades in pumps, martensitic chromium-nickel stainless steel X3CrNiMo13-4 is surface treated by means of shot peening. Due to the process principle, the kinetic impact energy of the shot peening medium is lower and the resulting surface roughness is higher when compared with another mechanical surface treatment technology machine hammer peening. Machine hammer peening is an incremental, high-frequency surface treatment process that offers advantages over shot peening due to its deterministic process kinematics. However, the influence of the process parameters of machine hammer peening such as impact force, impact angle, and stroke length on the surface integrity of X3CrNiMo13-4 is unknown. Therefore, the objective of this work is to investigate the influence of peening strategies on the residual stresses and the surface roughness depending on various combinations of process parameters. Additionally, the surface layer state after machine hammer peening is compared to both, a milled and a shot peened surface. The results show that machine hammer peening leads to smoother surfaces accompanied by higher compressive residual stresses compared to an industrial shot peening reference.

Cemented carbides are brittle-hard materials. Their properties are adjusted by the chemical composition, especially the binder fraction and the average hard phase grain size. This research work focuses on grinding of cemented carbides with tungsten carbide (WC) as hard phase and cobalt (Co) as binder phase material. Previous work showed that the WC-Co cemented carbide specification influences the grinding behavior. This study focuses on the influence of the cemented carbide specification on the grinding wheel wear. For this purpose, grinding tests were carried out with cemented carbides that differ in cobalt content and average WC grain size. Based on the thermo-mechanical load collective and the grinding wheel wear, conclusions were drawn about the influence of the cemented carbide specification on the wear behavior of the grinding wheel and the wear mechanisms.

A method for the development of a predictive model for the die roll height in fine blanking using artificial neural networks and support vector machines is presented. Since artificial neural networks require big amounts of training data and generation using experiments is very time consuming and cost intensive, a validated FE model is used instead. The required training data will be determined using learning curves. The optimal architecture and hyperparameter of the artificial neural network will be derived. Additionally, the die roll height is modelled using support vector machines and also conventional statistical regression models. Finally the accuracy of the methods is compared.