TY - CHAP A1 - Nobre, J. P. A1 - Noster, Ulf A1 - Gibmeier, J. A1 - Altenberger, Igor A1 - Kornmeier, M. A1 - Dias, A. A1 - Scholtes, Berthold ED - Kainer, Karl U. T1 - Mechanical Behavior and Residual Stresses in AZ31 Wrought Magnesium Alloy Subjected to Four Point Bending T2 - Magnesium Alloys and Their Applications N2 - Several specimens of AZ31 magnesium alloy were taken in different directions from a rolled plate and subjected to tensile, compressive and four-point bending tests. Tensile and compressive tests allowed to characterize the mechanical properties of the material in the rolling and cross rolling directions. The bending tests were carried out in four different specimen types to take the effect of the anisotropy induced by the rolling procedure itself into account. Six strain gages per specimen allowed to observe the evolution of the strain with the bending moment during the tests. All bending specimens were bent until a total compressive deformation of 2.5 %. It was observed that the corresponding tensile strain was significant lower and slightly different for each specimen type. In addition, a characteristic non-uniform distribution of deformation twinning was observed. The induced residual stresses after bending were characterized by X-ray diffraction (XRD) and incremental hole-drilling (IHD). Due to the different mechanical behavior in tension and compression, an asymmetric residual stress distribution after bending could be observed. The neutral axis was, in all cases, shifted towards the tensile side. This observation agrees with the strain measurements during bending tests. Y1 - 2006 SN - 9783527607556 U6 - https://doi.org/10.1002/3527607552.ch53 SP - 336 EP - 341 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Voyer, Joel A1 - Peterlechner, Christian A1 - Noster, Ulf T1 - Flame sprayed Al-12Si coatings for the improvement of the adhesion of composite casting profiles JF - Journal of Thermal Spray Technology N2 - In this study, flame sprayed Al-12Si coatings were produced on the surface of inlays (aluminum profiles) of composite castings parts. The aim was to enhance the strength between the joining partners inlay and cast. Due to the high surface roughness and the presence of pores in the coatings, combined with the formation of an intermetallic phase at the interface, the adhesion of flame sprayed inlays could be enhanced by a factor of 2 compared to blank inlays and by a factor of 1.3 when compared to sand-blasted inlays. However, results also show that gaps are present, mostly at the interface between the inlays and the flame sprayed coatings, and these gaps have a negative effect on the joining strength of the composite casting parts. Therefore, optimizing the adhesion of the coating on the Al profiles via an improvement in both the sand-blasting and the flame spraying parameters would be beneficial for further enhancement of the adhesion of composite casting parts. KW - aluminum composites KW - fatigue and fracture KW - flame spray KW - influence of properties Y1 - 2008 U6 - https://doi.org/https://doi.org/10.1007/s11666-008-9235-8 SN - 1544-1016 SN - 1059-9630 VL - 17 IS - 5-6 SP - 824 EP - 830 PB - Springer CY - Boston, Mass. ER - TY - JOUR A1 - Anten, Kerstin A1 - Lebsanft, Markus A1 - Krauß, M. A1 - Noster, Ulf A1 - Scholtes, Berthold T1 - Einfluss von Randschichtzustand und Haltezeit auf die thermische Ermüdung der Magnesiumbasislegierung AZ31 JF - Materialwissenschaft und Werkstofftechnik N2 - Die vorliegende Arbeit befasst sich mit Untersuchungen zur thermischen Ermüdung der Magnesiumbasislegierung AZ31 im Temperaturbereich zwischen +50°C und +290°C. Die Experimente erfolgten unter konstanter Totaldeformation (out-of-phase-Beanspruchung) und es wurde der Verlauf der Spannungsamplitude sowie der plastischen Dehnungsamplitude über die Zahl der Temperaturzyklen ermittelt. Insbesondere wurde der Einfluss einer mechanischen Oberflächenbehandlung (Festwalzen) sowie von Haltezeiten auf den Verlauf der Schädigung untersucht. In beiden Fällen konnte kein signifikanter Unterschied zu unbehandelten Proben bzw. Beanspruchungen ohne Haltezeit festgestellt werden, welches auf die Wechselwirkungen zwischen Verformungs- und Rekristallisationsprozessen bei der thermischen Ermüdung zurückzuführen ist. T2 - Influence of near surface materials states and of hold-times on thermal fatigue of magnesium base alloy AZ31 Y1 - 2012 VL - 43 IS - 12 SP - 993 EP - 1000 PB - Wiley ER - TY - CHAP A1 - Juijerm, Patiphan A1 - Altenberger, Igor A1 - Noster, Ulf A1 - Scholtes, Berthold T1 - Residual stress relaxation and cyclic deformation behavior of deep rolled AlMg4.5Mn (AA5083) at elevated temperatures T2 - Materials Science Forum N2 - The cyclic deformation behavior of deep rolled and polished aluminium wrought alloy AlMg4,5Mn in the temperature range 20-300°C has been investigated. Results of quasistatic tension and compression tests of untreated specimens in the temperature range 20-300°C are presented. To characterize the fatigue behavior for stress-controlled tests as a function of test temperature, s-n curves, cyclic deformations curves and mean strains as a function of number of cycles are given. The residual stress- and work hardening states near the surface of deep rolled aluminium alloy AlMg4.5Mn before and after fatigue tests were investigated by X-ray diffraction methods. The investigated AlMn4.5Mn aluminium alloy shows cyclic hardening until fracture at all stress amplitudes in stress-controlled fatigue tests at 25-150°C. With increasing temperature the deformation behavior shifts from cyclic hardening to cyclic softening. Below a certain stress amplitude at a given temperature deep rolling led to a reduction of the plastic strain amplitude as compared to the untreated state through cyclically stable near-surface work hardening as indicated by stable FWHM-values. This reduction in plastic strain amplitude is associated with enhanced fatigue lives. The effectiveness of deep rolling is governed by the cyclic and thermal stability of near-surface work hardening rather than macroscopic compressive residual stresses. Since near-surface work hardening is known to retard crack initiation, deep rolling is also effective in temperature- and stress ranges where macroscopic compressive residual stresses have relaxed almost completely, but where near-surface work hardening prevails. Above certain stress amplitudes and temperatures, deep rolling has no beneficial effect on the fatigue behavior of AlMg4.5Mn. This is a consequence of instable near-surface microstructures, especially instable near-surface work hardening. KW - deep rolling KW - residual stress relaxation KW - high temperature fatigue Y1 - 2005 U6 - https://doi.org/10.4028/www.scientific.net/MSF.490-491.436 VL - 490-491 SP - 436 EP - 441 PB - Trans Tech Publications ER - TY - JOUR A1 - Kettner, Michael A1 - Noster, Ulf A1 - Kilian, Helmut A1 - Gradinger, Rudolf A1 - Kuehlein, Wolfgang A1 - Drevenstedt, Armin A1 - Stadler, Franz A1 - Ladstaetter, Elisabeth A1 - Lutz, Andreas T1 - The InnMag project - Processing Mg for civil aircraft application JF - Advanced Engineering Materials N2 - In the context of the “InnMag” project, partners from industry and science are co-operating to investigate the issues involved in adapting established production processes to the material Mg. The project's aim is to further the deployment of Mg interior parts in civil aircraft. The project covers every production step, from alloy selection, Mg ingot melting, alloying, direct chill casting, extruding, machining, surface treatment and component assembly. This paper discusses the project's targets and the results arrived at so far, particularly in the areas of direct chill casting and extrusion. Y1 - 2007 U6 - https://doi.org/10.1002/adem.200700143 VL - 9 IS - 9 SP - 813 EP - 819 PB - Wiley ER - TY - JOUR A1 - Mundl, A. A1 - Noster, Ulf T1 - Topology optimization using a structural component as example JF - Konstruktion T2 - Topologieoptimierung am Beispiel eines Strukturbauteils Y1 - 2006 IS - 1-2 SP - 65 EP - 68 PB - VDI Fachmedien ; Springer CY - Düsseldorf ER - TY - CHAP A1 - Ucsnik, Stephan A. A1 - Gradinger, Rudolf A1 - Noster, Ulf A1 - Pahr, Dieter H. T1 - Finite element based optimization of a novel metal-composite-joint T2 - 1st EUCOMAS, European Conference on Materials and Structures in Aerospace, Conference Berlin, May 26 - 27, 2008  N2 - Aerospace and automotive industries employ three main techniques to set up joints between metal and fibre reinforced plastics parts (FRP); adhesive bonding, mechanical fastening with rives/bolts and a hybrid combination. A new joint technique has been developed to combine the two advantageous mechanisms form-closure and adhesion in a fibre-friendly way. Prior is established through metal structures (pins) which are perpendicularly welded onto metal surfaces with an arc-welding-process. They intrude into the FRP during lay-up and therefore set up a first connection. The composite-matrix is responsible for latter adhesive bonding and final form closure. Finite-element-analyses of cylindrically shaped joints are carried out to get detailed knowledge of the influence of parameters like pin-number, pin-position, pin-height, pin-form sleeve-geometry, and stiffness behaviour. Long calculation times of 3D-models lead to the introduction of a corresponding 2D-axisymmetric-model which is used to run parameter-studies within a reasonable time. For this novel technique the combination of fibre-friendly form closure and adhesive bonding of interface plays a major role. A well selected amount of vertical reinforcements, their placement and geometrical dimensions will lead to a stiffer joint. Goal is to minimize fibre-deletion and overlap length to improve load-transfer and joint-strength, to reduce weight in high-strength-applications as well as the avoidance of safety rivets. Y1 - 2008 SN - 0083-5560 SP - 371 EP - 379 PB - VDI-Verlag CY - Düsseldorf ER - TY - CHAP A1 - Altenberger, Igor A1 - Noster, Ulf A1 - Scholtes, Berthold A1 - Ritchie, Robert O. ED - Wagner, Lothar T1 - High Temperature Fatigue of Mechanically Surface Treated Materials T2 - Shot peening N2 - Introduction The most well known effect of mechanical surface treatments on metallic materials is the improvement in fatigue properties. It is therefore not surprising that most of the archival literature on mechanical surface treatments, such as shot peening, deep rolling and laser shock peening, deals with the effect of near-surface properties on fatigue behavior. Most of these studies, however, are confined to room temperature fatigue behavior; in comparision, the effect of mechanical surface treatment on fatigue behavior at high temperatures has been rarely investigated [1-5]. The reason for this disparity can be found in the popular belief that fatigue strength improvement by mechanical surface treatments is mainly due to the presence of compressive residual stresses, and since such stresses should anneal out at elevated temperatures, mechanical surface treatments for high temperature applications would appear questionable. However, this view may be over simplistic as there is always a possibility that the residual stresses may be at least partially stable at elevated temperatures [6]; in addition, other factors may be involved, such as the nature of the near-surface microstructure. Accordingly, it is the objective of this study to examine the role of mechanical surface treatments on the high temperature fatigue behavior of several metallic engineering materials. Moreover, it is the aim of this work to clarify what are the critical temperature "thresholds' at which near-surface microstructures and residual stresses become unstable and whether this can explain the observed fatigue behavior. Y1 - 2003 SN - 9783527606580 U6 - https://doi.org/10.1002/3527606580.ch62 SP - 483 EP - 489 PB - Wiley-VCH CY - Weinheim; [Cambridge] ER - TY - BOOK A1 - Altenberger, Igor A1 - Wagner, Lothar A1 - Mhaede, Mansour A1 - Juijerm, Patiphan A1 - Noster, Ulf T1 - Effect of Deep Rolling on the Cyclic Performance of Magnesium and Aluminium Alloys in the Temperature Range 20-250°C T3 - The 10th International Conference on Shot Peening (ICSP), Conference Proceedings, Tokyo Japan, 15th to 18th September, 2008 N2 - Mechanical surface treatments such as deep rolling or laser-shock peening can markedly affect the cyclic performance of light-weight alloys, especially if significant thick work hardened surface regions are induced. At room temperature, the cyclic deformation behaviour is strongly influenced by the nature of the induced near-surface microstructures provided that they remain stable during fatigue loading. At elevated temperatures, the stability of near-surface work hardening and local microstructures plays an even more important role since the process-induced residual compressive stresses are likely to anneal out partially or completely. This overview illustrates to what extent deep rolling can effect the cyclic performance of various wrought light alloys being fatigue loaded in stress control at ambient and elevated temperatures. KW - Deep Rolling KW - Aluminum Alloys KW - Magnesium Alloys KW - High Temperature Fatigue Y1 - 2008 UR - https://www.researchgate.net/publication/273319235_Effect_of_Deep_Rolling_on_the_Cyclic_Performance_of_Magnesium_and_Aluminium_Alloys_in_the_Temperature_Range_20-250C ER - TY - CHAP A1 - Noster, Ulf A1 - Altenberger, Igor A1 - Ritchie, Robert O. A1 - Scholtes, Berthold ED - Wagner, Lothar T1 - Isothermal Fatigue Behavior and Residual Stress States of Mechanically Surface Treated Ti-6Al-4V: Laser Shock Peening vs. Deep Rolling T2 - Shot peening N2 - In this paper, the high-temperature fatigue behavior and residual stress states of a Ti-6Al-4V alloy are investigated after mechanical surface treatment. In particular, the two surface treatments investigated, laser shock peening and deep rolling, were observed to result in significantly different residual stress states. The consequent isothermal fatigue behavior at elevated temperatures, characterized using cyclic deformation curves, are discussed in terms of the stability of the near-surface work hardening and compressive residual stresses. Despite pronounced relaxation of the residual stresses, both laser shock peening and deep rolling led to a significant improvement in the cyclic deformation behavior and, hence, increased fatigue lifetimes at elevated temperatures as compared to untreated materials states. Y1 - 2003 SN - 9783527606580 U6 - https://doi.org/10.1002/3527606580.ch57 SP - 447 EP - 453 PB - Wiley-VCH CY - Weinheim; [Cambridge] ER - TY - JOUR A1 - Noster, Ulf A1 - Scholtes, Berthold T1 - Isothermal strain-controlled quasi-static and cyclic deformation behavior of magnesium wrought alloy AZ31 JF - International Journal of Materials Research / Zeitschrift für Metallkunde N2 - The low-cycle and high-cycle fatigue behavior of the Mg-base wrought alloy AZ31 is investigated in the temperature range 20– 300 °C using total-strain-controlled push – pull tests. It is shown that the mechanical properties of the material are substantially influenced by the direction dependent formation of deformation twins and resulting deformation asymmetry. As a consequence tensile mean stresses develop during total-strain-controlled fatigue tests without mean strain. Y1 - 2003 U6 - https://doi.org/10.1515/ijmr-2003-0098 VL - 94 IS - 5 SP - 559 EP - 563 ER - TY - JOUR A1 - Bitsche, Robert A1 - Noster, Ulf A1 - Peterlechner, Christian T1 - Fügepartner schlüssig zu Leichtbaukomponenten verbinden? JF - Lightweight Design N2 - Kombinationen aus kraft- und formschlüssigen Verbindungen erhöhen die Leistung bei im Hybridguss verbundenen Gussteilen mit Anbau- oder Einlegeteilen und machen separate Fügeprozesse überflüssig. Simulations-Methoden unterstützen das Design kraft- und formschlüssiger Verbindungen. Ergebnisse eines Ausdrückversuchs zeigen eine relativ gute Übereinstimmung zwischen gemessenen und mittels Simulation ermittelten Kraft-Weg-Kurven. Y1 - 2008 U6 - https://doi.org/10.1007/BF03223528 VL - 1 IS - 2 SP - 30 EP - 34 PB - Springer ER - TY - CHAP A1 - Billinger, Wolfgang A1 - Noster, Ulf ED - Degischer, Hans Peter T1 - Bauteilfertigung T2 - Leichtbau Y1 - 2009 SN - 9783527628247 U6 - https://doi.org/10.1002/9783527628247.ch4 SP - 247 EP - 278 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Nalla, Ravi K. A1 - Altenberger, Igor A1 - Noster, Ulf A1 - Liu, G.Y. A1 - Scholtes, Berthold A1 - Ritchie, Robert O. T1 - On the influence of mechanical surface treatments—deep rolling and laser shock peening—on the fatigue behavior of Ti–6Al–4V at ambient and elevated temperatures JF - Materials Science and Engineering: A N2 - It is well known that mechanical surface treatments, such as deep rolling, shot peening and laser shock peening, can significantly improve the fatigue behavior of highly-stressed metallic components. Deep rolling (DR) is particularly attractive since it is possible to generate, near the surface, deep compressive residual stresses and work hardened layers while retaining a relatively smooth surface finish. In the present investigation, the effect of DR on the low-cycle fatigue (LCF) and high-cycle fatigue (HCF) behavior of a Ti–6Al–4V alloy is examined, with particular emphasis on the thermal and mechanical stability of the residual stress states and the near-surface microstructures. Preliminary results on laser shock peened Ti–6Al–4V are also presented for comparison. Particular emphasis is devoted to the question of whether such surface treatments are effective for improving the fatigue properties at elevated temperatures up to ∼450 °C, i.e. at a homologous temperature of ∼0.4T/Tm (where Tm is the melting temperature). Based on cyclic deformation and stress/life (S/N) fatigue behavior, together with the X-ray diffraction and in situ transmission electron microscopy (TEM) observations of the microstructure, it was found that deep rolling can be quite effective in retarding the initiation and initial propagation of fatigue cracks in Ti–6Al–4V at such higher temperatures, despite the almost complete relaxation of the near-surface residual stresses. In the absence of such stresses, it is shown that the near-surface microstructures, which in Ti–6Al–4V consist of a layer of work hardened nanoscale grains, play a critical role in the enhancement of fatigue life by mechanical surface treatment. KW - Deep rolling KW - Elevated temperature behavior KW - Fatigue KW - Laser shock peening KW - Residual stress KW - Surface treatment KW - Ti–6Al–4V Y1 - 2003 U6 - https://doi.org/10.1016/S0921-5093(03)00069-8 SN - 1873-4936 VL - 355 IS - 1-2 SP - 216 EP - 230 PB - Elsevier ER - TY - JOUR A1 - Noster, Ulf A1 - Scholtes, Berthold T1 - Bauschingerefekt und mechanische Zwillingsbildung der Magnesiumlegierung AZ31 JF - Härterei-technische Mitteilungen : HTM ; Zeitschrift für Werkstoffe, Wärmebehandlung, Fertigung Y1 - 2003 UR - https://www.researchgate.net/publication/285130307_Bauschingerefekt_und_mechanische_Zwillingsbildung_der_Magnesiumlegierung_AZ31 VL - 58 SP - 322 EP - 327 PB - Hanser ER - TY - JOUR A1 - Bartsch, Alexander A1 - Burger, Moritz A1 - Grad, Marius A1 - Esper, Lukas A1 - Schultheiß, Ulrich A1 - Noster, Ulf A1 - Schratzenstaller, Thomas T1 - Enhancement of laser cut edge quality of ultra-thin titanium grade 2 sheets by applying an in-process approach using modulated Yb:YAG continuous wave fiber laser JF - Discover Mechanical Engineering N2 - Titanium is used in many areas due to its excellent mechanical, biological and corrosion-resistant properties. Implants often have thin and filigree structures, providing an ideal application for fine cutting with laser. In the literature, the main focus is primarily on investigating and optimizing the parameters for titanium sheets with thicknesses greater than 1 mm. Hence, in this study, the basic manufacturing parameters of laser power, cutting speed and laser pulse of a 200 W modulated fiber laser are investigated for 0.15 mm thick grade 2 titanium sheets. A reproducible, continuous cut could be achieved using 90 W laser-power and 2 mm/s cutting-speed. Pulse pause variations between 85 and 335 μs in 50 μs steps and a fixed pulse width of 50 μs show that a minimum kerf width of 23.4 μm, as well as a minimum cut edge roughness Rz of 3.59 μm, is achieved at the lowest pulse pause duration. An increase in roughness towards the laser exit side, independent of the laser pulse pause duration, was found and discussed. The results provide initial process parameters for cutting thin titanium sheets and thus provide the basis for further investigations, such as the influence of cutting gas pressure and composition on the cut edge. KW - Laser cutting KW - Titanium sheet KW - Kerf Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-65647 N1 - Corresponding author: Alexander Bartsch IS - 10 PB - Springer ER - TY - INPR A1 - Grad, Marius A1 - Haag, Lydia A1 - Hahn, Konstantin A1 - Schultheiß, Ulrich A1 - Esper, Lukas A1 - Noster, Ulf T1 - Influence of carbon content on the formation of TiC at diffusion bonded titanium-steel interface N2 - Hot pressing of pure Ti and various carbon steels in a temperature range of 950 – 1050 °C creates an up to 9 μm thick compound layer of TiC at the Ti/ steel interface. The calculation of the activation energy for layer formation is 126.5 - 136.7 kJ/mol, independent of the steels carbon content. As the carbon content of the steel increases, the layer thickness also increases, which provides enormous potential for the surface modification of Ti/ Ti-alloys. Y1 - 2023 U6 - https://doi.org/10.2139/ssrn.4261928 PB - Elsevier ER - TY - INPR A1 - Burger, Moritz A1 - Bartsch, Alexander A1 - Grad, Marius A1 - Esper, Lukas A1 - Schultheiß, Ulrich A1 - Noster, Ulf A1 - Schratzenstaller, Thomas T1 - Enhancement of laser cut edge quality of ultra-thin titanium grade 2 sheets by applying in-process approach using modulated Yb:YAG continuous wave fibre laser N2 - Titanium is used in many areas due to its excellent mechanical, biological and corrosion-resistant properties. Implants often have thin and filigree structures, providing an ideal application for laser fine cutting. In literature, the main focus is primarily on investigating and optimizing the parameters for titanium sheet thicknesses greater than 1 mm. Hence, in this study, the basic manufacturing parameters of laser power, cutting speed and laser pulsing of a 200 W modulated fibre laser are investigated for 0.15 mm thick titanium grade 2 sheets. A reproducible, continuous cut could be achieved using 90 W laserpower and 2 cutting-speed. Pulse pause variations between 85–335 μs in 50 μs steps and fixed pulse duration of 50 μs show that a minimum kerf width of 23.4 μm, as well as a minimum cut edge roughness Rz of 3.59 μm, is achieved at the lowest pulse pause. An increase in roughness towards the laser exit side, independent of the laser pulse pause, was found and discussed. The results provide initial process parameters for cutting thin titanium sheets and thus provide the basis for further investigations, such as the influence of cutting gas pressure and composition on the cut edge. Y1 - 2023 U6 - https://doi.org/10.21203/rs.3.rs-2520041/v1 N1 - Erschienen in der Zeitschrift: Discover Mechanical Engineering, https://opus4.kobv.de/opus4-oth-regensburg/frontdoor/index/index/docId/6564 ER - TY - GEN A1 - Esper, Lukas A1 - Noster, Ulf A1 - Schultheiss, Ulrich A1 - Bund, Andreas T1 - Quasi-in-Situ Analysis of Electropolished Additively Manufactured Stainless Steel Surfaces T2 - ECS Meeting Abstracts, F01: Advances in Industrial Electrochemistry and Electrochemical Engineering N2 - Progress in additive manufacturing is leading to the emergence of new areas of application. Laser Powder Bed Fusion (L-PBF) is increasingly used for the development of metallic medical implants, but for high-risk implants like vascular support structures (stents), surface quality is critical to ensure successful implantation without harming the surrounding tissue and ensure the patients’ health. Therefore, enhancing the surface quality is crucial. Electropolishing is a method for removing surface roughness by smoothing out micro-peaks and valleys. However, L-PBF structures have a high surface roughness due to metal particles adhering on the surface. To achieve a smooth surface for additively manufactured implants like stents using electropolishing, the removal of these particles needs to be studied in more detail. The objective of this study is to examine the electropolishing mechanism of 316L stainless steel samples additively manufactured through Laser Powder Bed Fusion (L-PBF). The main objective is to investigate the removal properties and surface characteristics during electropolishing. To achieve this, various surfaces were characterized for morphology and roughness during Hull cell experiments. Markings are utilized on the Hull cell sample surfaces to identify points of interest during quasi-in-situ measurements. The surfaces are then analyzed after multiple time steps, applying different currents to investigate particle dissolution. The surface characteristics are analyzed through scanning electron microscopy, and surface roughness is analyzed using laser scanning microscopy. The results show that the electropolishing process preferentially removes the adhering particles present on the surface of the samples. Increasing the current density results in faster particle dissolution and a smoother surface (see Figure 1a and b). The mechanism of material removal of various surface features, as shown in Figure 1 (red circle, yellow arrow and red square), was assessed based on the experimental results of the surface structures seen on the SEM images. It was found that different surface features were removed during the experiment at different polishing times and current densities. The amount of charge flowed was found to correlate with surface morphology. Based on the obtained results, various surface features (such as large adherent particles, agglomerates of smaller particles, and valleys) and their changes with increasing test duration and current density were observed by quasi-in situ analyses. A reduction in the diameter of round particles adhering to the surface was observed at both low and higher current densities (see Figure 1a red circle a). Increasing the polishing time resulted in leveling of both large particles and valleys (see Figure 1b red square). Also, dissolution of agglomerates of smaller particles occurred at different polishing times as a function of current density and polishing time (see Figure 1a yellow arrow) are observed. Smoothed surface structures can be observed in regions with equivalent surface charge density (see Figure 2). As a result, comparable surface morphologies may appear at the same area charge density, irrespective of a specific current density. So, it may be adequate to only consider the amount of charge flowed to describe the electropolishing of additive materials. In conclusion, comprehending the dissolution characteristics of particles on L-PBF surfaces is essential for attaining satisfactory surface finish in electropolishing. The results of this study offer valuable perspectives into the electropolishing mechanism of additively manufactured 316L stainless steel and can guide future investigations on surface finishing and polishing of additive manufactured implants like stents. Figure 1 KW - General Earth and Planetary Sciences KW - General Environmental Science Y1 - 2023 U6 - https://doi.org/10.1149/MA2023-02241342mtgabs SN - 2151-2043 VL - MA2023-02 SP - 1342 EP - 1342 PB - The Electrochemical Society ER - TY - JOUR A1 - Grad, Marius A1 - Schultheiß, Ulrich A1 - Diemar, Andreas A1 - Spieß, Lothar A1 - Noster, Ulf T1 - Preparation methodology for the microstructural characterization of diffusion layers in a titanium/steel composite JF - Practical Metallography N2 - Hot pressing of titanium and carbon steel leads to the formation of a diffusion layer at the interface. Depending on the carbon content of the steel used, it either exclusively contains TiC or additional other phases. In the case of steel with a medium carbon concentration (0.67 wt.% C), a pure TiC layer forms. A preparation methodology was developed to make statements about functional and microstructural properties of the respective layers such as layer thickness, porosity, or grain size. However, apart from the diffusion layer’s microstructure, it also reveals the microstructure of the two base substrates. A comparison based on electron backscatter diffraction (EBSD) examinations yields similar results in terms of microstructure. A micrograph analysis based on the new preparation methodology also allows confirming the element distribution measurement by glow discharge optical emission spectroscopy (GDOES). The methodology therefore provides a way of quickly and reliably controlling the layer formation during the hot pressing process of titanium and carbon steel. N2 - Beim Heißpressen von Titan und Kohlenstoffstahl entsteht an der Grenzfläche eine Diffusionsschicht, welche abhängig vom Kohlenstoffgehalt des verwendeten Stahls entweder ausschließlich TiC oder zusätzliche andere Phasen enthält. Im Fall eines Stahls mit mittlerer Kohlenstoffkonzentration (0,67 wt.-% C) bildet sich eine reine TiC-Schicht. Um eine Aussage über die funktionalen und mikrostrukturellen Eigenschaften, wie Schichtdicke, Porosität oder Korngröße, entsprechender Schichten treffen zu können, wurde eine Präparationsmethodik entwickelt. Hierbei wird jedoch nicht nur das Gefüge der Diffusionsschicht, sondern auch das der beiden Grundsubstrate entwickelt. Ein Vergleich mit Elektronenrückstreubeugungs-Untersuchungen (EBSD) liefert hinsichtlich der Mikrostruktur vergleichbare Ergebnisse. Auch die Messung der Elementverteilung durch Glimmentladungsspektroskopie (GDOES) kann durch eine Schliffbildanalyse unter Anwendung der neuen Präparationsmethodik belegt werden. Die Methodik stellt also eine Möglichkeit zur schnellen und sicheren Kontrolle der Schichtbildung beim Heißpressen von Titan und Kohlenstoffstahl dar. T2 - Präparationsmethodik zur mikrostrukturellen Charakterisierung von Diffusionsschichten eines Titan-Stahl-Verbunds KW - Diffusion layers KW - TiC KW - microstructure KW - preparation methodology KW - EBSD KW - GDOES Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-78346 SN - 2195-8599 N1 - Corresponding author der OTH Regensburg: Marius Grad VL - 61 IS - 12 SP - 938 EP - 946 PB - Walter de Gruyter GmbH ER - TY - CHAP A1 - Altenberger, Igor A1 - Nalla, Ravi K. A1 - Noster, Ulf A1 - Liu, G.Y. A1 - Scholtes, Berthold A1 - Ritchie, Robert O. ED - Lütjering, G. ED - Albrecht, J. T1 - Effects of Deep Rolling on the Fatigue Behavior of Ti-6Al-4V at Ambient and Elevated Temperatures T2 - Ti-2003 Science and Technology, Proceedings of the 10th World Conference on Titanium, held at the CCH-Congress Center Hamburg, Germany 13-18 July 2003, Vol 1 Y1 - 2003 UR - http://www.titaniumthemetal.org/epub/World-Conference-Proceedings-2003-Section-2/F7E2908C00CB5A5E8414934CBF8702B1/WTC%202003%20Sec%202.pdf SN - 3-527-30306-5 SP - 1059 EP - 1066 PB - Wiley ER - TY - CHAP A1 - Altenberger, Igor A1 - Noster, Ulf A1 - Nalla, Ravi K. A1 - Ritchie, Robert O. A1 - Scholtes, Berthold T1 - Residual stress relaxation in fatigue of mechanically surface treated materials T2 - Proceedings 132nd Annual TMS Meeting, March 2–6, 2003, San Diego, California Y1 - 2003 UR - https://www.researchgate.net/publication/273462779_Residual_stress_relaxation_in_fatigue_of_mechanically_surface_treated_materials SP - 312 ER - TY - CHAP A1 - Altenberger, Igor A1 - Nalla, Ravi K. A1 - Noster, Ulf A1 - Scholtes, Berthold A1 - Ritchie, Robert O. T1 - On the fatigue behavior and associated effect of residual stresses in deep rolled and laser shock peened Ti-6Al-4V at ambient and elevated temperatures T2 - 2003 TMS annual meeting N2 - Mechanical surface treatments, such as deep rolling, shot peening and laser shock peening, can significantly improve the fatigue behavior of highly stressed metallic components. Deep rolling is an especially attractive technique since it is possible to generate deep, near-surface compressive residual stresses and work hardening while retaining a relatively smooth surface finish. Indeed, this technique is best known for increasing the fatigue strength and lifetime of steel components such as crankshafts. Although most work on deep rolling has been on steels, recently it has also been applied with reasonable success to titanium alloys. Accordingly, in this investigation, we examine the effect of deep rolling on the high-cycle fatigue behavior of Ti-6Al-4V, with particular emphasis on the thermal and mechanical stability of the residual stress states and near-surface microstructures. Preliminary results on laser shock peened Ti-6Al-4V are also presented for comparison. In addition, we examine whether these surface treatments are effective in retaining fatigue strength at the higher temperatures of 300 to 450C. Based on the cyclic deformation and stress/life behavior, together with the X-ray and microstructural observations, it is found that deep rolling can be quite effective in retarding the initiation and initial propagation of fatigue cracks in Ti-6Al-4V at such higher temperatures, despite the almost complete relaxation of the residual stresses at the surface. This clearly implies that, in addition to residual stresses, near-surface microstructures, which in Ti-6Al-4V consist of ultrafine near-surface nanostructures, play a critical role in the enhancement of fatigue lifetimes by mechanical surface treatments. Y1 - 2003 UR - https://www.researchgate.net/publication/273462702_On_the_fatigue_behavior_and_associated_effect_of_residual_stresses_in_deep_rolled_and_laser_shock_peened_Ti-6Al-4V_at_ambient_and_elevated_temperatures SP - 359 PB - The Minerals, Metals & Materials Society (TMS) ER - TY - JOUR A1 - Esper, Lukas A1 - Schultheiss, Ulrich A1 - Grad, Marius A1 - Noster, Ulf A1 - Bund, Andreas T1 - Application of the Hull Cell for Identifying Electropolishing Parameters to Adjust Surface Morphology in Additive Manufacturing JF - ECS Advances N2 - Additively processed materials are increasingly used to manufacture customized parts, e.g. medical implants. Implant surfaces often require a smooth finish, which can be achieved by post-processing and well-defined process parameters. In this study, the effects of electropolishing of metal parts produced by laser powder bed fusion are investigated using Hull cell experiments and a three-electrode setup. Current density voltage curves were measured with the three-electrode setup to identify the regimes for electropolishing. Subsequently different constant-currents were applied and Hull cell experiments were conducted. The surface roughness (Sz, Sa) and the mass removal were analysed. Surface morphologies were assessed using laser scanning and scanning electron microscopy. A reduction of the initial surface roughness of more than 90% to Sa < 0.3 μm has been achieved. Considering the passed electrical charge during electropolishing, results from Hull cell experiments are systematically correlated with current-controlled electropolishing. This approach enables the precise tailoring of polishing parameters to achieve surfaces with defined roughness. Furthermore, the study demonstrates the suitability of Hull cells in determining electropolishing parameters for additive materials and highlights their contribution to post-processing in additive manufacturing. Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-86295 SN - 2754-2734 N1 - Corresponding author der OTH Regensburg: Lukas Esper VL - 4 IS - 4 PB - The Electrochemical Society ER - TY - JOUR A1 - Gersch, Sebastian A1 - Noster, Ulf A1 - Schulz, Carsten A1 - Bagdahn, Jörg T1 - Influence of the Process-Related Surface Structure of L-PBF Manufactured Components on Residual Stress Measurement Using the Incremental Hole Drilling Method JF - Applied Sciences N2 - Laser Powder Bed Fusion (L-PBF) parts combine geometric freedom with process-induced rough surfaces that challenge residual-stress metrology. We evaluated the accuracy of the incremental hole-drilling (IHD) method with electronic speckle pattern interferometry (ESPI) by applying defined stresses via four-point bending to stress-relieved AlSi10Mg coupons, rather than measuring unknown process stresses. Flat specimens (2 mm, thin per ASTM E837) were analyzed on up-skin, side-skin, and CNC-milled surfaces; thin-specimen calibration coefficients were used. After a preliminary inter-specimen check (three specimens per surface; spread < 8 MPa), one representative specimen per surface was tested with three drill sites to assess intra-specimen uniformity. Measured IHD–ESPI stresses agreed best at 70 MPa: deviations were ~4.1% (up-skin), 6.0% (side-skin), and 6.24% (CNC-milled). At 10 MPa the relative errors increased (23.6%, 18.4%, and 1.40%), consistent with reduced ESPI signal-to-noise and fixture compliance in the low-stress regime. At 140 MPa, deviations rose again (21.1%, 14.3%, and 13.1%), reflecting operation near the ~60% Rp0.2 elastic limit of hole-drilling and potential local plasticity. Surface-dependent artifacts also mattered as follows: the side-skin required no coating and performed comparably to CNC-milled, whereas the up-skin’s roughness plus matting spray introduced fringe distortions and chip/coating debris near the hole. This controlled study indicates that IHD–ESPI can provide reliable results on L-PBF AlSi10Mg in the mid-stress range when surface preparation, coating, and rig compliance are carefully managed. Limitations include excluding down-skin surfaces and testing only one specimen per condition; thus, results should be generalized cautiously. KW - L-PBF KW - residual stress KW - hole drilling method KW - surface roughness KW - surface condition KW - AlSi10Mg Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-84929 SN - 2076-3417 VL - 15 IS - 18 PB - MDPI ER -