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21. CIRP Conference on Electro Physical and Chemical Machining, ISEM XXI, Zurich, Switzerland, 14 Jun 2022 - 17 Jun 2022; Procedia CIRP 113, 23-28 (2022). doi:10.1016/j.procir.2022.09.114 special issue: "21st CIRP Conference on Electro Physical and Chemical Machining, ISEM XXI June, 14 to 17, 2022 in Zurich / edited by Konrad Wegener, Stefan Fabbro, Paulo Matheus Borges", Published by Elsevier, Amsterdam [u.a.]

Electrical discharge machining (EDM) is a versatile unconventional machining process allowing high precision manufacturing. Due to the thermal main active principle, the process-induced heat affected rim zone always needs to be particularly considered regarding its characteristics as the resulting surface integrity has to fulfill the needed functional properties for advanced applications. Today, no deterministic model is available especially for the residual stress prediction. As consequence, current process design is based on experience and heuristic optimization. The paper therefore mechanistically links the material modification and the process-induced load. Inversion of the according process signature component finally allows model-based process design.

Materials science and engineering technology = Materialwissenschaft und Werkstofftechnik 52(11), 1214-1229 (2021). doi:10.1002/mawe.202100087, Published by Wiley-VCH, Weinheim

The energy distribution in electrical discharge machining is still subject to discussions. On the one hand, it is important to know the exact amount of energy that is applied to a workpiece, since solely this heat is responsible for the loads that are applied to the material and result in material modifications. On the other hand, it is very difficult to directly measure the heat due to the diminutive temporal and spatial scales. Hence, a method was developed to measure the size of the gas bubble that evolves during the discharge and used to model the energy fraction that dissipates during the formation of named bubble. With the easily measurable general energy input and the developed model, the number of unknown fractions of the energy distribution can be reduced. This step allows for a better assumption of the energies that load and modify the workpiece material.

18th CIRP Conference on Modeling of Machining Operations, CMMO, online, 15 Jun 2021 - 17 Jun 2021; Procedia CIRP 102, 482-487 (2021). doi:10.1016/j.procir.2021.09.082 special issue: "18th CIRP Conference on Modeling of Machining Operations (CMMO), Ljubljana, Slovenia, June 15-17, 2021 / Edited by Edvard Govekar, Franci Pu��avec, Rok Vrabic", Published by Elsevier, Amsterdam [u.a.]

18th CIRP Conference on Modeling of Machining Operations, CMMO, online, 15 Jun 2021 - 17 Jun 2021; Procedia CIRP 102, 204-209 (2021). doi:10.1016/j.procir.2021.09.035 special issue: "18th CIRP Conference on Modeling of Machining Operations (CMMO), Ljubljana, Slovenia, June 15-17, 2021 / Edited by Edvard Govekar, Franci Pu��avec, Rok Vrabic", Published by Elsevier, Amsterdam [u.a.]

Abrasive waterjet (AWJ) machining has proven to be one of the most flexible non-conventional production techniques for difficult-to-machine materials. However, the prediction of process results is challenging since multiple physical processes occur simultaneously. Until now, the use of alternative abrasive material for special applications has received limited attention. In this work, different solid materials of altered shape and mechanical properties were used to analyze the physical phenomena experimentally. A ceramic and a steel abrasive material of either circular or angular geometry were used. The experiments were conducted by AWJ controlled-depth machining on 42CrMo4 steel in various structural modifications regarding the interference of particle interactions. Furthermore the study aims to gain a fundamental understanding of the AWJ erosion process of different abrasive grit for a better prediction and optimization of AWJ machining, in particular for future applications.

Electrical discharge machining is a process with main thermal active principal. Thus, for example for steel materials it is unavoidable to modify the rim zone of the final workpiece. Knowledge or even prediction of these modifications would improve industrial applications. Basis for this is the information about the time and locally resolved temperature field, which is not available in that form today. Hence the objective of this work is to establish a model of the temperature field within the electrodes rim zone during electrical discharge machining process. In this work, this field is modeled for the electrical discharge machining process based on the measurable discharge energy of a single discharge. First, an energy dissipation model for a single discharge is presented. In the next step, the interaction of two consecutive discharges is analyzed. Both results are the inputs for a macroscopic process model to calculate the temperature field of the whole workpiece. Finally, by coupling this macroscopic temperature field and the single discharge model it is possible to determine the locally resolved temperature field at any time of the process. For typical conditions, it is very unlikely that two discharges affect each other regarding overlaying temperature fields in the micro range but over time, a macroscopic heating could take place depending on the dielectric cooling efficiency.

5th CIRP Conference on Surface Integrity, Viruell, CSI 2020, online, 1 Jun 2020 - 5 Jun 2020; Procedia CIRP 87, 509-514 (2020). doi:10.1016/j.procir.2020.02.066 special issue: "5th CIRP Conference on Surface Integrity (CSI 2020) / Edited by Pedro J. Arrazola, Aitor Madariaga", Published by Elsevier, Amsterdam [u.a.]

20th CIRP Conference on Electro Physical and Chemical Machining, ISEM 2020, online, 19 Jan 2021 - 21 Jan 2021; Procedia CIRP 95, 238-243 (2021). doi:10.1016/j.procir.2020.01.149 special issue: "20th CIRP Conference on Electro Physical and Chemical Machining / Edited by Konrad Wegener, Moritz Wiessner", Published by Elsevier, Amsterdam [u.a.]

20th CIRP Conference on Electro Physical and Chemical Machining, ISEM 2020, online, 19 Jan 2021 - 21 Jan 2021; Procedia CIRP 95, 688-693 (2021). doi:10.1016/j.procir.2020.02.298 special issue: "20th CIRP Conference on Electro Physical and Chemical Machining / Edited by Konrad Wegener, Moritz Wiessner", Published by Elsevier, Amsterdam [u.a.]

5th CIRP Conference on Surface Integrity , Virtuell, CSI 2020, online, 1 Jun 2020 - 5 Jun 2020; Procedia CIRP 87, 273-278 (2020). doi:10.1016/j.procir.2020.02.114 special issue: "5th CIRP Conference on Surface Integrity (CSI 2020) / Edited by Pedro J. Arrazola, Aitor Madariaga", Published by Elsevier, Amsterdam [u.a.]

20th CIRP Conference on Electro Physical and Chemical Machining, ISEM 2020, online, 19 Jan 2021 - 21 Jan 2021; Procedia CIRP 95, 726-730 (2021). doi:10.1016/j.procir.2020.01.170 special issue: "20th CIRP Conference on Electro Physical and Chemical Machining / Edited by Konrad Wegener, Moritz Wiessner", Published by Elsevier, Amsterdam [u.a.]

20th CIRP Conference on Electro Physical and Chemical Machining, ISEM 2020, online, 19 Jan 2021 - 21 Jan 2021; Procedia CIRP 95, 178-182 (2021). doi:10.1016/j.procir.2020.02.318 special issue: "20th CIRP Conference on Electro Physical and Chemical Machining / Edited by Konrad Wegener, Moritz Wiessner", Published by Elsevier, Amsterdam [u.a.]

Modelling of ECM is a powerful tool to improve the cost- and time intensive tool-development process. However, for certain combinations of process and geometric parameters, the simulation results include non-physical negative pressure values inside the electrolyte flow. These phenomena occur near the narrow opening into the machining gap. According to Bernoulli's law, it is plausible that low-pressure values are present in this region possibly leading to evaporation. Based on these facts, it was hypothesized that cavitation could occur during ECM. In order to successfully validate this hypothesis, the electrolyte flow is analysed both in experimental as well as simulation-based studies.

ESAFORM 2021 : 24th International Conference on Material Forming 24th International Conference on Material Forming, ESAFORM 2021, online, 14 Apr 2021 - 16 Apr 2021; Li��ge : ULi��ge Library 1518, 1-9 (2021). doi:10.25518/esaform21.1518, Published by ULi��ge Library, Li��ge

The generator technology of electrical discharge machining (EDM) has evolved significantly over the last decades. This enabled EDM to become a crucial technology in die and mold manufacturing. Moreover, EDM became a more important technology due to the enhanced power efficiency, process-based power dissipation and control strategies especially for tools made from hard materials like cemented carbides. Even though, EDM is considered a standard process for this application today, cemented carbide tools still suffer from premature failure. This is often due to thermally affected rim zones resulting from the EDM processes. Thus, the formation of cracks and white layer should be investigated for contemporary EDM technology. To get a better understanding of the impact of the machining process different cemented carbide grades need to be compared. Therefore in this paper, four kinds of cemented carbides, three versions with normal binder phase content and a variant almost binder free, are analyzed. The materials are machined using roughing and finishing technologies. Then the materials are investigated under the specific consideration of the machined surface integrity of sinking EDM.

This paper aims to visualize spatio-temporal phenomena in electro physical and chemical processes in order to understand machining mechanisms and to achieve a technological breakthrough. In situ measurement methods to visualize the time evolution of stress, strain, temperatures, fluid velocities, and species density distributions, together with 2D or 3D images of the workpieces being processed are summarized. Applications of these methods to fundamental studies on electrical discharge machining, electrochemical machining, laser processing and additive manufacturing are introduced. Signal recording and processing technologies and real time monitoring enabling closed-loop feedback control are also discussed.

17th CIRP Conference on Modelling of Machining Operations, 17th CIRP CMMO, Sheffield, UK, 13 Jun 2019 - 14 Jun 2019; Procedia CIRP 82, 14-19 (2019). doi:10.1016/j.procir.2019.04.165 special issue: "17th CIRP Conference on Modelling of Machining Operations (17th CIRP CMMO) / Edited by Erdem Ozturk, Tom Mcleay, Rachid Msaoubi", Published by Elsevier, Amsterdam [u.a.]

For the successful implementation of bio-degradable magnesium implants in medicine, a defined corrosion behaviour according to the bone growth needs to be established. While conventional concepts focus on a defined adaptation of the base alloy composition, the presented approach focusses on a defined macro- and microstructuring of the implant. This includes both, a defined surface enlargement and conversion by surface modification as well as the realization of inner channels for ingrowth achieved by a process combination of plasma electrolytic oxidation (PEO) and electrical discharge machining (EDM). Resulting surface characteristics as well as in-vitro behaviour have been comprehensively analyzed and preliminary in-vivo results are given.

9th CIRP Conference on High Performance Cutting, HPC 2020, online, 24 May 2021 - 26 May 2021; Procedia CIRP 101, 81-84 (2021). doi:10.1016/j.procir.2021.02.010 special issue: "9th CIRP Conference on High Performance Cutting / Edited by Erdem Ozturk, David Curtis, Hassan Ghadbeigi", Published by Elsevier, Amsterdam [u.a.]

20th CIRP Conference on Electro Physical and Chemical Machining, ISEM 2020, online, 19 Jan 2021 - 21 Jan 2021; Procedia CIRP 95, 189-194 (2021). doi:10.1016/j.procir.2020.01.198 special issue: "20th CIRP Conference on Electro Physical and Chemical Machining / Edited by Konrad Wegener, Moritz Wiessner", Published by Elsevier, Amsterdam [u.a.]

The international journal of advanced manufacturing technology (2021). doi:10.1007/s00170-021-07858-x, Published by Springer, London

The efficiency of material removal by electrochemical machining (ECM) and rim zone modifications is highly dependent on material composition, the chemical surface condition at the break through potential, the electrolyte, the machining parameters and the resulting current densities and local current density distribution at the surfaces. The ECM process is mechanistically determined by transpassive anodic metal dissolution and layer formation at high voltages and specific electrolytic compositions. The mechanisms of transpassive anodic metal dissolution and oxide formation are not fully understood yet for steels such as 42CrMo4. Therefore, martensitic 42CrMo4 was subjected to ECM in sodium nitrate solution with two different current densities and compared to the native oxide of ground 42CrMo4. The material removal rate as well as anodic dissolution and transpassive oxide formation were investigated by mass spectroscopic analysis (ICP-MS) and (angle-resolved) X-ray photoelectron spectroscopy ((AR)XPS) after ECM. The results revealed the formation of a Fe3&minus, xO4 mixed oxide and a change of the oxidation state for iron, chromium and molybdenum, e.g., 25% Fe (II) was present in the oxide at 20.6 A/cm2 and was substituted by Fe (III) at 34.0 A/cm2 to an amount of 10% Fe (II). Furthermore, ECM processing of 42CrMo4 in sodium nitrate solution was strongly determined by a stationary process with two parallel running steps: 1. Transpassive Fe3&minus, xO4 mixed oxide formation/repassivation, as well as 2. dissolution of the transpassive oxide at the metal surface.

9th CIRP Conference on High Performance Cutting, HPC 2020, online, 24 May 2021 - 26 May 2021; Procedia CIRP 101, 202-205 (2021). doi:10.1016/j.procir.2020.11.009 special issue: "9th CIRP Conference on High Performance Cutting / Edited by Erdem Ozturk, David Curtis, Hassan Ghadbeigi", Published by Elsevier, Amsterdam [u.a.]

20th CIRP Conference on Electro Physical and Chemical Machining, ISEM 2020, online, 19 Jan 2021 - 21 Jan 2021; Procedia CIRP 95, 262-267 (2021). doi:10.1016/j.procir.2020.02.281 special issue: "20th CIRP Conference on Electro Physical and Chemical Machining / Edited by Konrad Wegener, Moritz Wiessner", Published by Elsevier, Amsterdam [u.a.]

Metals : open access journal 11(7), 1102 (2021). doi:10.3390/met11071102 special issue: "Special Issue "High-Performance Applications of Metals and Alloys: Material Properties, Behaviour Modeling, Optimal Design and Advanced Processes" / Special Issue Editors: Prof. Dr. Cristiano Fragassa, Guest Editor ; Dr. Grzegorz Lesiuk, Guest Editor ; Dr. Jeremy Epp, Guest Editor", Published by MDPI, Basel

20th CIRP Conference on Electro Physical and Chemical Machining, ISEM 2020, online, 19 Jan 2021 - 21 Jan 2021; Procedia CIRP 95, 360-365 (2021). doi:10.1016/j.procir.2020.02.325 special issue: "20th CIRP Conference on Electro Physical and Chemical Machining / Edited by Konrad Wegener, Moritz Wiessner", Published by Elsevier, Amsterdam [u.a.]

20th CIRP Conference on Electro Physical and Chemical Machining, ISEM 2020, online, 19 Jan 2021 - 21 Jan 2021; Procedia CIRP 95, 290-295 (2021). doi:10.1016/j.procir.2020.01.165 special issue: "20th CIRP Conference on Electro Physical and Chemical Machining / Edited by Konrad Wegener, Moritz Wiessner", Published by Elsevier, Amsterdam [u.a.]

20th CIRP Conference on Electro Physical and Chemical Machining, ISEM 2020, online, 19 Jan 2021 - 21 Jan 2021; Procedia CIRP 95, 694-699 (2021). doi:10.1016/j.procir.2020.01.163 special issue: "20th CIRP Conference on Electro Physical and Chemical Machining / Edited by Konrad Wegener, Moritz Wiessner", Published by Elsevier, Amsterdam [u.a.]

The demand for higher efficiency in aircraft propulsion engines leads to materials with increasing thermomechanical strengths and new designs inducing filigree geometries of blisks and disks. Because of new designs which induce tighter tolerances, the high mechanical process forces in conventional cutting processes like broaching cause inacceptable geometrical deviations and high tooling costs. Due to the electro-thermal material removal mechanism, electrical discharge machining (EDM) ensures a force free and thus precise machining. The manufacture of fir tree slots in nickel-based alloys by wire EDM has been investigated in the last few years and the process was verified as an alternative technology for broaching. To get a better competitive position, the productivity can be prospectively increased by using an additional indexing rotary axis which ensures a precise and automated production of rotationally symmetric components and reduce production times, e.g., for the manufacture of fir tree slots on a disk. Nevertheless, the application of these axes cause changed flushing conditions and can also affect the electrical contacting as well. Both influence the process performance and demand a technology development or adjustment of standard machining technologies. The influence of these changed machining conditions has not been investigated scientifically to date. In this paper, the surface integrity and process performance of fir tree slots machined by wire EDM on the machine table are compared with the manufacture by using an additional indexing rotary axis.

19th Machining Innovations Conference for Aerospace Industry 2019, MIC 2019, Garbsen, Germany, 27 Nov 2019 - 28 Nov 2019; Procedia manufacturing 40, 22-26 (2020). doi:10.1016/j.promfg.2020.02.005 special issue: "19th Machining Innovations Conference for Aerospace Industry 2019 (MIC 2019), 27-28 November 2019, Garbsen, Germany / Edited by Berend Denkena", Published by Elsevier, Amsterdam [u.a.]

5th CIRP Conference on Surface Integrity, CSI 2020, Mondragón, Spain, 1 Jun 2020 - 5 Jun 2020; Procedia CIRP 87, 456-641 (2020). doi:10.1016/j.procir.2020.02.096 special issue: "5th CIRP Conference on Surface Integrity (CSI 2020) / Edited by Pedro J. Arrazola, Aitor Madariaga", Published by Elsevier, Amsterdam [u.a.]

5th CIRP Conference on Surface Integrity, Virtuell, CSI 2020, online, 1 Jun 2020 - 5 Jun 2020; Procedia CIRP 87, 474-479 (2020). doi:10.1016/j.procir.2020.02.111 special issue: "Part of special issue: 5th CIRP Conference on Surface Integrity (CSI 2020) / Edited by Pedro J. Arrazola, Aitor Madariaga", Published by Elsevier, Amsterdam [u.a.]

The surface and subsurface conditions of components are significant for their functional properties. Every manufacturing process step changes the surface condition due to its mechanical, chemical and/or thermal impact. The depth of the affected zone varies for different machining operations, and is predetermined by the process parameters and characteristics. Furthermore, the initial state has a decisive influence on the interactions that lead to the final surface conditions. The aim of the investigation presented here is to compare the influence of the load characteristics over the depth applied to manufactured components by several different machining operations and to determine the causing mechanisms. In order to ensure better comparability between the surface modifications caused by different machining operations, the same material was used (AISI 4140, German steel grade 42CrMo4 acc. to DIN EN 10083-3) and annealed to a ferritic-pearlitic microstructure. Based on interdisciplinary cooperation within the collaborative research center CRC/Transregio 136 &ldquo, Process Signatures&rdquo, seven different manufacturing processes, i.e., grinding, turning, deep rolling, laser processing, inductive heat treatment, electrical discharge machining (EDM) and electrochemical machining (ECM), were used, and the resulting surface zones were investigated by highly specialized analysis techniques. This work presents the results of X-ray measurements, hardness measurements and electron microscopic investigations. As a result, the characteristics and depths of the material modifications, as well as their underlying mechanisms and causes, were studied. Mechanisms occurring within 42CrMo4 steel due to thermal, mechanical, chemical or mixed impacts were identified as phase transformation, solidification and strengthening due to dislocation generation and accumulation, continuum dynamic recrystallization and dynamic recovery, as well as chemical reactions.

17th CIRP Conference on Modelling of Machining Operations, CIRP CMMO, Sheffield, UK, 13 Jun 2019 - 14 Jun 2019; Procedia CIRP 2019(82), 432-437 (2019). doi:10.1016/j.procir.2019.04.144 special issue: "17th CIRP Conference on Modelling of Machining Operations (17th CIRP CMMO)/ Edited by Erdem Ozturk, Tom Mcleay, Rachid Msaoubi", Published by Elsevier, Amsterdam [u.a.]

Electrical discharge machining (EDM) is an ablative process with main thermal active principle. The applied thermal energy during this process leads to microstructure modifications in the rim zone of the eroded workpiece. These induced microstructure modifications directly affect the functionality of the workpiece. Nevertheless, these modifications cannot be easily predicted. Therefore, finding new methods for prediction of these modifications is of great interest both in academia and in industry. The microstructure modifications in the rim zone of an eroded workpiece are partly results of liquid-solid phase transformations in the recast layer and solid-solid phase transformations in the heat affected zone (HAZ). Therefore, by simulation of the microstructure evolution in these regions, their final microstructure can be predicted. Despite of the recent advances in the material simulation science, only few studies on simulation of microstructure evolution during EDM can be found in literature. This can be explained by the high temperature and temperature gradients that act during this process. These extreme boundary conditions evoke different complexities during material simulations. In this work, the complexities, which appear during the simulation of microstructure evolution for EDM are addressed. Furthermore, a simulation model for description of the microstructure evolution in a steel material under high temperature gradients is developed. The developed model is based on the phase field approach. Due to the potentials of this mathematical approach in describing the kinematics of multiphase systems, it became an attractive method for simulation of microstructure evolution. Although, the implemented temperature gradients are lower than the actual values, this model can be later used for simulation of the microstructure evolution in the HAZ of an eroded workpiece.

For the manufacturing of cost intensive high precision titanium parts for space applications, Wire EDM is without any appreciable alternative when it comes to filigree structures with high aspect ratio, as it allows machining independently of mechanical material properties like hardness or high temperature strength. Nevertheless, cost effectiveness is one of the key factors for guaranteeing a competitive position in high-wage markets like Western Europe. Therefore, an increase of productivity is crucial to maintain reasonable production costs whilst ensuring a consistent or even increasing quality of the part’s surface. For that reason, this paper aims to present an analysis of cutting rate related process signal characteristics for Ti-6Al-4V in order to systematically increase productivity including the influence of different wire electrodes.

In electrical discharge machining (EDM) material removal and rim zone modifications are resulted by generated heat during numerous discharges. By estimating the temperature field applied on the workpiece as material loading, removal rate and induced modifications in the rim zone can be predicted. Different scientists tried to simulate the induced temperature field on the workpiece during a single or multiple discharges. However, due to the complex removal mechanism in EDM, these models are mostly incomplete and contain considerable uncertainties. In this study, the strengths and weaknesses of typical heat transfer models for a single discharge are discussed. For this propose a finite element model is constructed and influences of different modeling parameters on the obtained results have been analyzed. Moreover, potentials of reverse microstructure simulation as an assistant for modification of heat source models discussed.