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Dr. Jeremy Epp
Leibniz Institute for Materials Engineering - IWT, Department Physical Analysis, Bremen, Germany

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0 Additive Manufacturing
0 Heat Treatment
0 Microstructure
0 Steel
0 residual stresses

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Steel
X-ray diffraction
residual stresses
Microstructure
Heat Treatment
Additive Manufacturing
surface integrity
Material Characterization

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Journal article
Published: 10 July 2021 in Metals
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The surface and subsurface conditions of components are critical for their functional properties. Every manufacturing process modifies the surface condition as a consequence of its mechanical, chemical, and thermal impact or combinations of the three. The depth of the affected zone varies for different machining operations and is related to the process parameters and characteristics. Furthermore, the initial material state has a decisive influence on the modifications that lead to the final surface conditions. With this knowledge, the collaborative research center CRC/Transregio 136 “Process Signatures” started a first joint investigation to analyze the influence of several machining operations on the surface modifications of uniformly premanufactured samples in a broad study. The present paper focusses on four defined process chains which were analyzed in detail regarding the resulting surface conditions as a function of the initial state. Two different workpiece geometries of the same initial material (AISI 4140, 42CrMo4 (1.7225) classified according to DIN EN ISO 683-2) were treated in two different heat treating lines. Samples annealed to a ferritic-perlitic microstructure were additionally deep rolled as starting condition. Quenched and tempered samples were induction hardened before further process application. These two states were then submitted to six different manufacturing processes, i.e., grinding (with mainly mechanical or thermal impact), precision turning (mainly mechanical), laser processing (mainly thermal), electrical discharge machining (EDM, mainly thermal) and electrochemical machining (ECM, (mainly chemical impact). The resulting surface conditions were investigated after each step of the manufacturing chain by specialized analysis techniques regarding residual stresses, microstructure, and hardness distribution. Based on the process knowledge and on the systematic characterizations, the characteristics and depths of the material modifications, as well as their underlying mechanisms and causes, were investigated. Mechanisms occurring within AISI 4140 steel (42CrMo4) due to thermal, mechanical or mixed impacts were identified as work hardening, stress relief, recrystallization, re-hardening and melting, grain growth, and rearrangement of dislocations.

ACS Style

Florian Borchers; Brigitte Clausen; Lisa Ehle; Marco Eich; Jérémy Epp; Friedhelm Frerichs; Matthias Hettig; Andreas Klink; Ewald Kohls; Yang Lu; Heiner Meyer; Bob Rommes; Sebastian Schneider; Rebecca Strunk; Tjarden Zielinski. The Influence of Former Process Steps on Changes in Hardness, Lattice and Micro Structure of AISI 4140 Due to Manufacturing Processes. Metals 2021, 11, 1102 .

AMA Style

Florian Borchers, Brigitte Clausen, Lisa Ehle, Marco Eich, Jérémy Epp, Friedhelm Frerichs, Matthias Hettig, Andreas Klink, Ewald Kohls, Yang Lu, Heiner Meyer, Bob Rommes, Sebastian Schneider, Rebecca Strunk, Tjarden Zielinski. The Influence of Former Process Steps on Changes in Hardness, Lattice and Micro Structure of AISI 4140 Due to Manufacturing Processes. Metals. 2021; 11 (7):1102.

Chicago/Turabian Style

Florian Borchers; Brigitte Clausen; Lisa Ehle; Marco Eich; Jérémy Epp; Friedhelm Frerichs; Matthias Hettig; Andreas Klink; Ewald Kohls; Yang Lu; Heiner Meyer; Bob Rommes; Sebastian Schneider; Rebecca Strunk; Tjarden Zielinski. 2021. "The Influence of Former Process Steps on Changes in Hardness, Lattice and Micro Structure of AISI 4140 Due to Manufacturing Processes." Metals 11, no. 7: 1102.

Journal article
Published: 05 July 2021 in Forschung im Ingenieurwesen
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The radial infeed rotary swaging is widely used as a diameter reduction forming process of axisymmetric workpieces, improving the mechanical properties with excellent near net shape forming. In the present study, rotary swaging experiments with different parameter setups were performed on steel tubes and bars under different material states and several resulting property modifications were investigated such as stress-strain curve, hardness, fatigue strength and surface residual stresses. The results show a significant work hardening induced by the rotary swaging process and an improvement in the static and dynamic mechanical properties was observed. Furthermore, the hardness distribution was homogenous in the cross section of the rotary swaged workpieces. Moreover, depending on the process conditions, different residual stresses distribution were generated along the surface.

ACS Style

Dhia Charni; Svetlana Ortmann-Ishkina; Marius Herrmann; Christian Schenck; Jérémy Epp. Mechanical properties of rotary swaged steel components. Forschung im Ingenieurwesen 2021, 1 -10.

AMA Style

Dhia Charni, Svetlana Ortmann-Ishkina, Marius Herrmann, Christian Schenck, Jérémy Epp. Mechanical properties of rotary swaged steel components. Forschung im Ingenieurwesen. 2021; ():1-10.

Chicago/Turabian Style

Dhia Charni; Svetlana Ortmann-Ishkina; Marius Herrmann; Christian Schenck; Jérémy Epp. 2021. "Mechanical properties of rotary swaged steel components." Forschung im Ingenieurwesen , no. : 1-10.

Journal article
Published: 29 May 2021 in Materials Today Communications
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Stainless steels like X210Cr12 consist of metastable austenite that transforms into martensite when a critical temperature or critical strain is reached. However, the mechanism of martensite formation and the shape and appearance of martensite can differ significantly depending on the used mechanical or thermal pathway. This necessitates a systematic study on the martensitic transformation and twinning of metastable austenite in X210Cr12 after liquid nitrogen cooling, deep rolling and their sequential combinations. The thereby obtained surface modifications were characterized by hardness penetration measurements, electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and orientation and phase mapping using automated scanning electron nano-diffraction (SEND). X-Ray diffraction (XRD) was performed to measure residual stresses in the surface near regions of the samples. The here obtained results show that liquid nitrogen cooling yields formation of coarse grained martensite with grain sizes between 1 and 10 μm and deep rolling causes formation of a nanosized microstructure containing martensite and twins. Moreover, the here obtained results suggest that compressive residual stresses of up to −750 MPa together with the martensite/twin nanostructure stabilizes metastable austenite and prevents the formation of large martensite grains in the surface zone during subsequent liquid nitrogen cooling. A substantial hardness increase ranging from 355 HV0.1 up to about 850 HV0.1 was measured for all treatments. The highest value of about 950 HV0.1 was measured after martensite transformation induced by liquid nitrogen cooling.

ACS Style

Lisa C. Ehle; Joshua Spille; Heiner Meyer; Jeannine Kämmler; Jonas Werner; Alexander Schwedt; Jeremy Epp; Thomas E. Weirich; Joachim Mayer. Controlled twinning and martensitic transformation in metastable AISI D3 (X210Cr12) steel by sequential deep rolling and liquid nitrogen cooling. Materials Today Communications 2021, 28, 102484 .

AMA Style

Lisa C. Ehle, Joshua Spille, Heiner Meyer, Jeannine Kämmler, Jonas Werner, Alexander Schwedt, Jeremy Epp, Thomas E. Weirich, Joachim Mayer. Controlled twinning and martensitic transformation in metastable AISI D3 (X210Cr12) steel by sequential deep rolling and liquid nitrogen cooling. Materials Today Communications. 2021; 28 ():102484.

Chicago/Turabian Style

Lisa C. Ehle; Joshua Spille; Heiner Meyer; Jeannine Kämmler; Jonas Werner; Alexander Schwedt; Jeremy Epp; Thomas E. Weirich; Joachim Mayer. 2021. "Controlled twinning and martensitic transformation in metastable AISI D3 (X210Cr12) steel by sequential deep rolling and liquid nitrogen cooling." Materials Today Communications 28, no. : 102484.

Journal article
Published: 12 March 2021 in Metals
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In this work, the microstructural evolution during the dynamic transformation of austenite to bainite was directly observed by in-situ high energy synchrotron X-ray diffraction measurements during warm uniaxial compression performed at the P07 beamline of PETRA III, DESY (Deutsches Elektronen-Synchrotron). Plastic deformation triggers the phase transformation, which is continuously stimulated by the introduction of dynamic dislocations into the austenite. This scenario accelerates the kinetics of bainite formation in comparison with conventional isothermal treatment. No mechanical stabilization of austenite was observed during dynamic transformation. Evidence of carbon partitioning between phases during plastic deformation was obtained. Further post-process investigations suggest that the bainitic microstructure developed during compression is oriented perpendicular to the loading direction. The findings open up new possibilities to design carbide-free bainitic microstructures directly via thermomechanical processing.

ACS Style

William Bevilaqua; Jérémy Epp; Heiner Meyer; Juan Dong; Hans Roelofs; Alexandre Da Silva Rocha; Afonso Reguly. Revealing the Dynamic Transformation of Austenite to Bainite during Uniaxial Warm Compression through In-Situ Synchrotron X-ray Diffraction. Metals 2021, 11, 467 .

AMA Style

William Bevilaqua, Jérémy Epp, Heiner Meyer, Juan Dong, Hans Roelofs, Alexandre Da Silva Rocha, Afonso Reguly. Revealing the Dynamic Transformation of Austenite to Bainite during Uniaxial Warm Compression through In-Situ Synchrotron X-ray Diffraction. Metals. 2021; 11 (3):467.

Chicago/Turabian Style

William Bevilaqua; Jérémy Epp; Heiner Meyer; Juan Dong; Hans Roelofs; Alexandre Da Silva Rocha; Afonso Reguly. 2021. "Revealing the Dynamic Transformation of Austenite to Bainite during Uniaxial Warm Compression through In-Situ Synchrotron X-ray Diffraction." Metals 11, no. 3: 467.

Original
Published: 04 March 2021 in Archive of Applied Mechanics
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Additionally to the achievable tight geometrical tolerances, rotary swaging can influence intrinsic material properties by work hardening and residual stresses generation. Although residual stresses should be usually avoided, they can be used on purpose to improve the performance properties of a produced part. To find prospective process settings, 2D FEM simulation of the rotary swaging process was developed and revealed the development of residual stresses distributions in E355 steel tubes in the whole longitudinal section. Besides the closing time, also geometric features of the dies were varied. It was found that the closing time affects the residual stresses significantly at the surface, but not in the depth of the part. By shortening the calibration zone, the axial tensile residual stresses near the outer surface could be lowered, while compressive residual stresses near the inner surface remained almost unaffected. By applying a higher die angle, the tensile axial residual stresses were increased while reducing the compressive axial residual stresses. Experimental investigations of residual stresses were performed by X-ray diffraction which revealed a good agreement between simulation results and physical measurements. With these findings, the rotary swaging process can be optimized for shaping residual stresses profiles to improve the performance properties of the produced parts.

ACS Style

Svetlana Ortmann-Ishkina; Dhia Charni; Marius Herrmann; Yang Liu; Jérémy Epp; Christian Schenck; Bernd Kuhfuss. Development of residual stresses by infeed rotary swaging of steel tubes. Archive of Applied Mechanics 2021, 1 -11.

AMA Style

Svetlana Ortmann-Ishkina, Dhia Charni, Marius Herrmann, Yang Liu, Jérémy Epp, Christian Schenck, Bernd Kuhfuss. Development of residual stresses by infeed rotary swaging of steel tubes. Archive of Applied Mechanics. 2021; ():1-11.

Chicago/Turabian Style

Svetlana Ortmann-Ishkina; Dhia Charni; Marius Herrmann; Yang Liu; Jérémy Epp; Christian Schenck; Bernd Kuhfuss. 2021. "Development of residual stresses by infeed rotary swaging of steel tubes." Archive of Applied Mechanics , no. : 1-11.

Original research article
Published: 22 February 2021 in Metallurgical and Materials Transactions A
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An experimental heat treatment chamber and control system were developed to perform in-situ X-ray diffraction experiments during low-pressure carburizing (LPC) processes. Results from the experimental chamber and industrial furnace were compared, and it was proven that the built system is reliable for LPC experiments. In-situ X-ray diffraction investigations during LPC treatment were conducted at the German Electron Synchrotron Facility in Hamburg Germany. During the boost steps, carbon accumulation and carbide formation was observed at the surface. These accumulation and carbide formation decelerated the further carbon diffusion from atmosphere to the sample. In the early minutes of the diffusion steps, it is observed that cementite content continue to increase although there is no presence of gas. This effect is attributed to the high carbon accumulation at the surface during boost steps which acts as a carbon supply. During quenching, martensite at higher temperature had a lower c/a ratio than later formed ones. This difference is credited to the early transformation of austenite regions having lower carbon content. Also, it was noticed that the final carbon content dissolved in martensite reduced compared to carbon in austenite before quenching. This reduction was attributed to the auto-tempering effect.

ACS Style

Ogün Baris Tapar; Jérémy Epp; Matthias Steinbacher; Jens Gibmeier. In-Situ Synchrotron X-ray Diffraction Investigation of Microstructural Evolutions During Low-Pressure Carburizing. Metallurgical and Materials Transactions A 2021, 52, 1427 -1442.

AMA Style

Ogün Baris Tapar, Jérémy Epp, Matthias Steinbacher, Jens Gibmeier. In-Situ Synchrotron X-ray Diffraction Investigation of Microstructural Evolutions During Low-Pressure Carburizing. Metallurgical and Materials Transactions A. 2021; 52 (4):1427-1442.

Chicago/Turabian Style

Ogün Baris Tapar; Jérémy Epp; Matthias Steinbacher; Jens Gibmeier. 2021. "In-Situ Synchrotron X-ray Diffraction Investigation of Microstructural Evolutions During Low-Pressure Carburizing." Metallurgical and Materials Transactions A 52, no. 4: 1427-1442.

Journal article
Published: 24 December 2020 in Metals
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Non-destructive determination of workpiece properties after heat treatment is of great interest in the context of quality control in production but also for prevention of damage in subsequent grinding process. Micromagnetic methods offer good possibilities, but must first be calibrated with reference analyses on known states. This work compares the accuracy and reliability of different calibration methods for non-destructive evaluation of carburizing depth and surface hardness of carburized steel. Linear regression analysis is used in comparison with new methods based on artificial neural networks. The comparison shows a slight advantage of neural network method and potential for further optimization of both approaches. The quality of the results can be influenced, among others, by the number of teaching steps for the neural network, whereas more teaching steps does not always lead to an improvement of accuracy for conditions not included in the initial calibration.

ACS Style

Rahel Jedamski; Jérémy Epp. Non-Destructive Micromagnetic Determination of Hardness and Case Hardening Depth Using Linear Regression Analysis and Artificial Neural Networks. Metals 2020, 11, 18 .

AMA Style

Rahel Jedamski, Jérémy Epp. Non-Destructive Micromagnetic Determination of Hardness and Case Hardening Depth Using Linear Regression Analysis and Artificial Neural Networks. Metals. 2020; 11 (1):18.

Chicago/Turabian Style

Rahel Jedamski; Jérémy Epp. 2020. "Non-Destructive Micromagnetic Determination of Hardness and Case Hardening Depth Using Linear Regression Analysis and Artificial Neural Networks." Metals 11, no. 1: 18.

Journal article
Published: 10 November 2020 in Materials
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Martensitic steels are tempered to increase the toughness of the metastable martensite, which is brittle in the as-quenched state, and to achieve a more stable microstructure. During the tempering of steels, several particular overlapping effects can arise. Classical dilatometric investigations can only detect effects by monitoring the integral length change of the sample. Additional in-situ diffractometry allowed a differentiation of the individual effects such as transformation of retained austenite and formation of cementite during tempering. Additionally, the lattice parameters of martensite and therefrom the tetragonality was analyzed. Two low-alloy steels with carbon contents of 0.4 and 1.0 wt.% and a high-alloy 5Cr-1Mo-steel with 0.4 wt.% carbon were investigated by dilatometry and in-situ diffractometry. In this paper, microstructural effects during tempering of the investigated steels are discussed by a comparative study of dilatometric and diffractometric experiments. The influence of the chemical composition on the tempering behavior is illustrated by comparing the determined effects of the three steels. The kinetics of tempering is similar for the low-alloy steels and shifted to much higher temperatures for the high-alloy steel. During tempering, the tetragonality of martensite in the steel with 1.0 wt% carbon shifts towards a low carbon behavior, as in the steels with 0.4 wt.% carbon.

ACS Style

Martin Hunkel; Juan Dong; Jeremy Epp; Daniel Kaiser; Stefan Dietrich; Volker Schulze; Ali Rajaei; Bengt Hallstedt; Christoph Broeckmann. Comparative Study of the Tempering Behavior of Different Martensitic Steels by Means of In-Situ Diffractometry and Dilatometry. Materials 2020, 13, 5058 .

AMA Style

Martin Hunkel, Juan Dong, Jeremy Epp, Daniel Kaiser, Stefan Dietrich, Volker Schulze, Ali Rajaei, Bengt Hallstedt, Christoph Broeckmann. Comparative Study of the Tempering Behavior of Different Martensitic Steels by Means of In-Situ Diffractometry and Dilatometry. Materials. 2020; 13 (22):5058.

Chicago/Turabian Style

Martin Hunkel; Juan Dong; Jeremy Epp; Daniel Kaiser; Stefan Dietrich; Volker Schulze; Ali Rajaei; Bengt Hallstedt; Christoph Broeckmann. 2020. "Comparative Study of the Tempering Behavior of Different Martensitic Steels by Means of In-Situ Diffractometry and Dilatometry." Materials 13, no. 22: 5058.

Journal article
Published: 23 September 2020 in tm - Technisches Messen
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Grinding processes are often the last step in the value-added chain of high-performance hardened steel components. However, thermo-mechanical loads which can take place during the process can have a detrimental effect on the surface integrity of ground parts, which are generally tested by post-process measurements. In the present study, two different approaches for an in-process inspection of the workpiece surface integrity were assessed using magnetic Barkhausen noise analysis during cylindrical grinding of hardened workpieces. The results showed that both measuring systems are able to detect changes in the surface state of workpieces in-process or directly after grinding in the grinding machine. After preparations to protect the sensors from influences during the grinding process, changes in the residual stress state and a decrease of hardness could be reliably detected. Due to constant contact conditions between sensor and workpiece a high reproducibility of the measurements was achieved.

ACS Style

Rahel Jedamski; Jonas Heinzel; Maximilian Rößler; Jérémy Epp; Jochen Eckebrecht; Jens Gentzen; Matthias Putz; Bernhard Karpuschewski. Potential of magnetic Barkhausen noise analysis for in-process monitoring of surface layer properties of steel components in grinding. tm - Technisches Messen 2020, 87, 787 -798.

AMA Style

Rahel Jedamski, Jonas Heinzel, Maximilian Rößler, Jérémy Epp, Jochen Eckebrecht, Jens Gentzen, Matthias Putz, Bernhard Karpuschewski. Potential of magnetic Barkhausen noise analysis for in-process monitoring of surface layer properties of steel components in grinding. tm - Technisches Messen. 2020; 87 (12):787-798.

Chicago/Turabian Style

Rahel Jedamski; Jonas Heinzel; Maximilian Rößler; Jérémy Epp; Jochen Eckebrecht; Jens Gentzen; Matthias Putz; Bernhard Karpuschewski. 2020. "Potential of magnetic Barkhausen noise analysis for in-process monitoring of surface layer properties of steel components in grinding." tm - Technisches Messen 87, no. 12: 787-798.

Journal article
Published: 05 July 2020 in Metals
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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 “Process Signatures”, 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.

ACS Style

Florian Borchers; Brigitte Clausen; Sandro Eckert; Lisa Ehle; Jeremy Epp; Simon Harst; Matthias Hettig; Andreas Klink; Ewald Kohls; Heiner Meyer; Markus Meurer; Bob Rommes; Sebastian Schneider; Rebecca Strunk. Comparison of Different Manufacturing Processes of AISI 4140 Steel with Regard to Surface Modification and Its Influencing Depth. Metals 2020, 10, 895 .

AMA Style

Florian Borchers, Brigitte Clausen, Sandro Eckert, Lisa Ehle, Jeremy Epp, Simon Harst, Matthias Hettig, Andreas Klink, Ewald Kohls, Heiner Meyer, Markus Meurer, Bob Rommes, Sebastian Schneider, Rebecca Strunk. Comparison of Different Manufacturing Processes of AISI 4140 Steel with Regard to Surface Modification and Its Influencing Depth. Metals. 2020; 10 (7):895.

Chicago/Turabian Style

Florian Borchers; Brigitte Clausen; Sandro Eckert; Lisa Ehle; Jeremy Epp; Simon Harst; Matthias Hettig; Andreas Klink; Ewald Kohls; Heiner Meyer; Markus Meurer; Bob Rommes; Sebastian Schneider; Rebecca Strunk. 2020. "Comparison of Different Manufacturing Processes of AISI 4140 Steel with Regard to Surface Modification and Its Influencing Depth." Metals 10, no. 7: 895.

Journal article
Published: 06 May 2020 in Metals
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Thermomechanical processing of low carbon bainitic steels is used to obtain a bainitic microstructure with good strength and toughness by continuous cooling after forging without the need of further heat treating, hence reducing manufacturing costs. However, hot forging parameters can significantly influence the microstructure in the forged material. A series of heat treating and forging experiments was carried out to analyze the effect of austenitizing time and temperature on the grain growth and the effect of forging temperature on the Prior Austenite Grain Size (PAGS) and continuously cooled microstructure. The forged microstructures were characterized by optical microscopy, microhardness tests, and X-ray diffraction. The results indicate that at 1200 °C austenitizing temperature abnormal grain growth takes place. Forging temperature significantly affects the PAGS and the subsequently formed microstructure. At high forging temperature (1200 °C), an almost fully bainitic microstructure was obtained. As the forging temperature was reduced to 1100 and 1000 °C, the PAGS refined, while the polygonal ferrite faction increased and the amount of retained austenite decreased. Further evaluations showed that a decrease in the forging temperature results in a higher carbon concentration in solution in the retained austenite leading to a stabilization effect.

ACS Style

Antonio Carlos De Figueiredo Silveira; William Lemos Bevilaqua; Vinicius Waechter Dias; Pedro José De Castro; Jeremy Epp; Alexandre Da Silva Rocha. Influence of Hot Forging Parameters on a Low Carbon Continuous Cooling Bainitic Steel Microstructure. Metals 2020, 10, 601 .

AMA Style

Antonio Carlos De Figueiredo Silveira, William Lemos Bevilaqua, Vinicius Waechter Dias, Pedro José De Castro, Jeremy Epp, Alexandre Da Silva Rocha. Influence of Hot Forging Parameters on a Low Carbon Continuous Cooling Bainitic Steel Microstructure. Metals. 2020; 10 (5):601.

Chicago/Turabian Style

Antonio Carlos De Figueiredo Silveira; William Lemos Bevilaqua; Vinicius Waechter Dias; Pedro José De Castro; Jeremy Epp; Alexandre Da Silva Rocha. 2020. "Influence of Hot Forging Parameters on a Low Carbon Continuous Cooling Bainitic Steel Microstructure." Metals 10, no. 5: 601.

Journal article
Published: 01 March 2020 in Scripta Materialia
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ACS Style

Jeremy Epp; Juan Dong; Heiner Meyer; Annika Bohlen. Analysis of cyclic phase transformations during additive manufacturing of hardenable tool steel by in-situ X-ray diffraction experiments. Scripta Materialia 2020, 177, 27 -31.

AMA Style

Jeremy Epp, Juan Dong, Heiner Meyer, Annika Bohlen. Analysis of cyclic phase transformations during additive manufacturing of hardenable tool steel by in-situ X-ray diffraction experiments. Scripta Materialia. 2020; 177 ():27-31.

Chicago/Turabian Style

Jeremy Epp; Juan Dong; Heiner Meyer; Annika Bohlen. 2020. "Analysis of cyclic phase transformations during additive manufacturing of hardenable tool steel by in-situ X-ray diffraction experiments." Scripta Materialia 177, no. : 27-31.

Journal article
Published: 13 January 2020 in Quantum Beam Science
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Mechanical loading scenarios, comparable to a deep rolling process, were reproduced in static indentation experiments on AISI 4140H steel samples with a cylindrical deep rolling tool and investigated in situ with synchrotron radiation at the European Synchrotron Radiation Facility (ESRF) on beamline ID11. Through the use of spatially resolved diffraction data, two-dimensional (2D) equivalent von Mises stress maps were recorded during loading and after unloading. The material modifications were analyzed in the material below the contact zone for different loading conditions. It was demonstrated that the characteristics of internal material load and residual stress distributions can be evaluated through data fitting and the effect of the applied force could be linked to the stress fields by an empirical model. The experimental values were then compared to a contact mechanics approach in order to analyze the correlation between the theoretical maximum loading stresses and the stored elastic residual stresses remaining by considering the dissipation of a certain amount of energy through plastic deformation.

ACS Style

Heiner Meyer; Jérémy Epp. Spatial Internal Material Load and Residual Stress Distribution Evolution in Synchrotron In Situ Investigations of Deep Rolling. Quantum Beam Science 2020, 4, 3 .

AMA Style

Heiner Meyer, Jérémy Epp. Spatial Internal Material Load and Residual Stress Distribution Evolution in Synchrotron In Situ Investigations of Deep Rolling. Quantum Beam Science. 2020; 4 (1):3.

Chicago/Turabian Style

Heiner Meyer; Jérémy Epp. 2020. "Spatial Internal Material Load and Residual Stress Distribution Evolution in Synchrotron In Situ Investigations of Deep Rolling." Quantum Beam Science 4, no. 1: 3.

Article
Published: 01 January 2020 in Materials Research
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It is well recognized the importance of the rheological characterization for the development of the steel in thermomechanical treatments, especially for the mechanical properties improvement of bainitic steels in subsequent hot forging optimization. Therefore, the plastic strain behaviour of a low carbon high silicon bainitic steel was studied through isothermal compression tests using a thermomechanical simulator at temperatures of 1123 K – 1423 K and strain rates of 0.1 – 5 s-1. Arrhenius equation was used to obtain the constitutive constants, which represents the material behaviour of flow stress in high temperature. Besides, work hardening, dynamic recovery, and the JMAK model in the dynamic recrystallization (DRX) of the steel parameters were determined. The second part of this research compared two proposed modified models from the literature, which showed the differences in modelled flow curves behaviour when they are applied for high strain levels. The flow curves were modelled in high strain levels for further implementation in numerical simulation, thus allowing an adjustment of parameters in hot forming processes for this bainitic steel. The proposed models presented an agreement with experimental values. However, only the Avrami equation to DRX showed the dynamic recovery mechanism in high strain levels, which has represented physical behaviour during the thermomechanical process.

ACS Style

Thiago Marques Ivaniski; Tomaz Fantin De Souza; Jérémy Épp; Alexandre Da Silva Rocha. Constitutive Modelling of High Temperature Flow Behaviour for a Low Carbon High Silicon Bainitic Steel. Materials Research 2020, 23, 1 .

AMA Style

Thiago Marques Ivaniski, Tomaz Fantin De Souza, Jérémy Épp, Alexandre Da Silva Rocha. Constitutive Modelling of High Temperature Flow Behaviour for a Low Carbon High Silicon Bainitic Steel. Materials Research. 2020; 23 (5):1.

Chicago/Turabian Style

Thiago Marques Ivaniski; Tomaz Fantin De Souza; Jérémy Épp; Alexandre Da Silva Rocha. 2020. "Constitutive Modelling of High Temperature Flow Behaviour for a Low Carbon High Silicon Bainitic Steel." Materials Research 23, no. 5: 1.

Artigos
Published: 01 January 2020 in Matéria (Rio de Janeiro)
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RESUMO Os novos aços bainíticos de resfriamento contínuo (CCBS) são uma excelente alternativa quando se requer elevada dureza, tenacidade e resistência à fadiga. Contudo, estima-se que a taxa de desgaste dos CCBS seja insuficiente para aplicação em componentes com alta solicitação mecânica, sendo necessário aprimorar suas propriedades de superfície. O objetivo deste estudo é o de analisar os efeitos da nitretação a plasma sobre à microestrutura e propriedades de desgaste do aço bainítico de resfriamento contínuo DIN18MnCrSiMo6-4. Portanto, tratamentos com duração de 6 horas foram conduzidos com pressão de 3 mbar, mistura gasosa composta por 76% N2 + 24% H2, e temperaturas de 400, 450, 500 e 550 °C, respectivamente. As amostras foram analisadas através de microscopia eletrônica de varredura, difração de raios-X, microdureza e ensaios de desgaste por deslizamento recíproco. Nas condições investigadas, foi possível obter uma camada de compostos e atingir um aumento de até 393% na dureza superficial, entretanto, o uso de temperaturas mais elevadas durante os tratamentos favoreceu a formação de camadas mais profundas. Em todas as amostras nitretadas, constatou-se a formação predominante da fase de nitretos ε-Fe2-3N e, em menor quantidade, da fase de nitretos γ’-Fe4N. Nos ensaios de deslizamento recíproco houve diminuição do desgaste das amostras nitretadas na temperatura de 550°C.

ACS Style

Rafael Luciano Dalcin; Leonardo Fonseca Oliveira; Alexandre Da Silva Rocha; Célia De Fraga Malfatti; Gelsa Edith Navarro Hidalgo; Jérémy Epp; Hans-Werner Zoch. Microestrutura e Propriedades de Desgaste do Aço Bainítico de Resfriamento Contínuo DIN 18MnCrSiMo6-4 Nitretado a Plasma em Diferentes Temperaturas. Matéria (Rio de Janeiro) 2020, 25, 1 .

AMA Style

Rafael Luciano Dalcin, Leonardo Fonseca Oliveira, Alexandre Da Silva Rocha, Célia De Fraga Malfatti, Gelsa Edith Navarro Hidalgo, Jérémy Epp, Hans-Werner Zoch. Microestrutura e Propriedades de Desgaste do Aço Bainítico de Resfriamento Contínuo DIN 18MnCrSiMo6-4 Nitretado a Plasma em Diferentes Temperaturas. Matéria (Rio de Janeiro). 2020; 25 (2):1.

Chicago/Turabian Style

Rafael Luciano Dalcin; Leonardo Fonseca Oliveira; Alexandre Da Silva Rocha; Célia De Fraga Malfatti; Gelsa Edith Navarro Hidalgo; Jérémy Epp; Hans-Werner Zoch. 2020. "Microestrutura e Propriedades de Desgaste do Aço Bainítico de Resfriamento Contínuo DIN 18MnCrSiMo6-4 Nitretado a Plasma em Diferentes Temperaturas." Matéria (Rio de Janeiro) 25, no. 2: 1.

Journal article
Published: 05 December 2019 in High-Throughput
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The development of novel structural materials with increasing mechanical requirements is a very resource-intense process if conventional methods are used. While there are high-throughput methods for the development of functional materials, this is not the case for structural materials. Their mechanical properties are determined by their microstructure, so that increased sample volumes are needed. Furthermore, new short-time characterization techniques are required for individual samples which do not necessarily measure the desired material properties, but descriptors which can later be mapped on material properties. While universal micro-hardness testing is being commonly used, it is limited in its capability to measure sample volumes which contain a characteristic microstructure. We propose to use alternative and fast deformation techniques for spherical micro-samples in combination with classical characterization techniques such as XRD, DSC or micro magnetic methods, which deliver descriptors for the microstructural state.

ACS Style

Matthias Steinbacher; Gabriela Alexe; Michael Baune; Ilya Bobrov; Ingmar Bösing; Brigitte Clausen; Tobias Czotscher; Jérémy Epp; Andreas Fischer; Lasse Langstädtler; Daniel Meyer; Sachin Raj Menon; Oltmann Riemer; Heike Sonnenberg; Arne Thomann; Anastasiya Toenjes; Frank Vollertsen; Nicole Wielki; Nils Ellendt. Descriptors for High Throughput in Structural Materials Development. High-Throughput 2019, 8, 22 .

AMA Style

Matthias Steinbacher, Gabriela Alexe, Michael Baune, Ilya Bobrov, Ingmar Bösing, Brigitte Clausen, Tobias Czotscher, Jérémy Epp, Andreas Fischer, Lasse Langstädtler, Daniel Meyer, Sachin Raj Menon, Oltmann Riemer, Heike Sonnenberg, Arne Thomann, Anastasiya Toenjes, Frank Vollertsen, Nicole Wielki, Nils Ellendt. Descriptors for High Throughput in Structural Materials Development. High-Throughput. 2019; 8 (4):22.

Chicago/Turabian Style

Matthias Steinbacher; Gabriela Alexe; Michael Baune; Ilya Bobrov; Ingmar Bösing; Brigitte Clausen; Tobias Czotscher; Jérémy Epp; Andreas Fischer; Lasse Langstädtler; Daniel Meyer; Sachin Raj Menon; Oltmann Riemer; Heike Sonnenberg; Arne Thomann; Anastasiya Toenjes; Frank Vollertsen; Nicole Wielki; Nils Ellendt. 2019. "Descriptors for High Throughput in Structural Materials Development." High-Throughput 8, no. 4: 22.

Journal article
Published: 14 March 2019 in Materials
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Infeed rotary swaging is a cold forming production technique to reduce the diameter of axisymmetric components. The forming is achieved discontinuously by a series of radial strokes that are spread over the shell of the part. Due to tolerances within the rotary swaging machine, these strokes perform individually and the resulting stroke pattern is not homogeneous with regards to circumferential and longitudinal distribution. Nevertheless, in combination with the high number of performed strokes and the large contact area between the dies and the part, the external part properties, such as diameter, roundness and surface roughness, show even values along the finished part. In contrast, strength-defining internal part properties, like microstructure and residual stress components, are more sensitive to the actual pattern and temporal sequence of the individual strokes, which is investigated in this study. The impact of process fluctuations during the conventional process, which are induced by the tolerances of machine tool components, was verified by numerical simulations, physical tests and measurements of residual stress distributions at the surface and at depth. Furthermore, a method is introduced to maintain the stroke following angle ∆φ at zero by flat dies, and thus the actual pattern and temporal sequence of the strokes was homogenized. The results show that the residual stress fluctuations at the surface could be controlled and reduced. Furthermore, it is demonstrated that the depth profile of the residual stresses at a distance of 300 µm from the surface developed independently from the process fluctuations.

ACS Style

Svetlana Ishkina; Dhia Charni; Marius Herrmann; Yang Liu; Jérémy Epp; Christian Schenck; Bernd Kuhfuss; Hans-Werner Zoch. Influence of Process Fluctuations on Residual Stress Evolution in Rotary Swaging of Steel Tubes. Materials 2019, 12, 855 .

AMA Style

Svetlana Ishkina, Dhia Charni, Marius Herrmann, Yang Liu, Jérémy Epp, Christian Schenck, Bernd Kuhfuss, Hans-Werner Zoch. Influence of Process Fluctuations on Residual Stress Evolution in Rotary Swaging of Steel Tubes. Materials. 2019; 12 (6):855.

Chicago/Turabian Style

Svetlana Ishkina; Dhia Charni; Marius Herrmann; Yang Liu; Jérémy Epp; Christian Schenck; Bernd Kuhfuss; Hans-Werner Zoch. 2019. "Influence of Process Fluctuations on Residual Stress Evolution in Rotary Swaging of Steel Tubes." Materials 12, no. 6: 855.

Journal article
Published: 09 October 2018 in Computers & Mathematics with Applications
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A challenge in the additive manufacturing process of laser beam melting of metals is the formation of residual stresses, which can cause large part deformations, when the part is released, lower the application range concerning tensile loads and provoke cracks. Due to the complexity and the interaction of different process parameters, the use of experimental studies for investigation is tedious and costly. An effective approach to analyze the effects is the numerical process simulation based on the method of finite elements. In this paper, the recently developed method of Mechanical Layer Equivalent for fast calculations of process induced distortions in laser beam melting is used to analyze the residual stresses during laser beam melting. For this purpose, small test samples have been generated additively and residual stresses have been measured by X-ray diffraction and compared to simulated values. The results show that despite the simplifications the model inhibits reliable prediction of residual stresses can be achieved.

ACS Style

Marvin Siewert; Fabian Neugebauer; Jeremy Epp; Vasily Ploshikhin. Validation of Mechanical Layer Equivalent Method for simulation of residual stresses in additive manufactured components. Computers & Mathematics with Applications 2018, 78, 2407 -2416.

AMA Style

Marvin Siewert, Fabian Neugebauer, Jeremy Epp, Vasily Ploshikhin. Validation of Mechanical Layer Equivalent Method for simulation of residual stresses in additive manufactured components. Computers & Mathematics with Applications. 2018; 78 (7):2407-2416.

Chicago/Turabian Style

Marvin Siewert; Fabian Neugebauer; Jeremy Epp; Vasily Ploshikhin. 2018. "Validation of Mechanical Layer Equivalent Method for simulation of residual stresses in additive manufactured components." Computers & Mathematics with Applications 78, no. 7: 2407-2416.

Conference paper
Published: 01 October 2018 in ABM Proceedings
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ACS Style

Carolina Vaghetti; Vinicius Waechter Dias; Jeremy Epp; Juan Dong; Alexandre Da Silva Rocha. ESTUDO DAS DISTORÇÕES E DISTRIBUIÇÕES DE TENSÕES RESIDUAIS EM EIXOS TEMPERADOS POR INDUÇÃO. ABM Proceedings 2018, 1 .

AMA Style

Carolina Vaghetti, Vinicius Waechter Dias, Jeremy Epp, Juan Dong, Alexandre Da Silva Rocha. ESTUDO DAS DISTORÇÕES E DISTRIBUIÇÕES DE TENSÕES RESIDUAIS EM EIXOS TEMPERADOS POR INDUÇÃO. ABM Proceedings. 2018; ():1.

Chicago/Turabian Style

Carolina Vaghetti; Vinicius Waechter Dias; Jeremy Epp; Juan Dong; Alexandre Da Silva Rocha. 2018. "ESTUDO DAS DISTORÇÕES E DISTRIBUIÇÕES DE TENSÕES RESIDUAIS EM EIXOS TEMPERADOS POR INDUÇÃO." ABM Proceedings , no. : 1.

Journal article
Published: 28 September 2018 in Quantum Beam Science
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Residual stresses originating from elasto-plastic deformation during mechanical processing can be analyzed post-process with various known methods. A new measurement method to measure and evaluate the strain and stress fields in situ under the contact point during a deep rolling process was developed to describe the dependence of the residual stresses from the internal material load. Using synchrotron radiation at European Synchrotron Radiation Facility (ESRF) (ID11), diffraction measurements were performed in transmission geometry during dynamical loading with different process parameters. The strain and stress fields were analyzed with high spatial resolution in an 8 mm × 4 mm area around the contact point during the process using a 13-mm tungsten carbide roller on samples of AISI 4140H steel. Fast data acquisition allowed the reconstruction of full two-dimensional (2D) strain and stress maps. These could be used to determine the response from the initial material state in front of the roller to the mechanically loaded region with plastic deformation up to the processed material with the resulting residual stresses. This comprehensive analysis was then used to link the internal material load with the resulting residual stresses in the final material state.

ACS Style

Heiner Meyer; Jérémy Epp. In Situ X-ray Diffraction Analysis of Stresses during Deep Rolling of Steel. Quantum Beam Science 2018, 2, 20 .

AMA Style

Heiner Meyer, Jérémy Epp. In Situ X-ray Diffraction Analysis of Stresses during Deep Rolling of Steel. Quantum Beam Science. 2018; 2 (4):20.

Chicago/Turabian Style

Heiner Meyer; Jérémy Epp. 2018. "In Situ X-ray Diffraction Analysis of Stresses during Deep Rolling of Steel." Quantum Beam Science 2, no. 4: 20.