bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bedeutung von Eigenspannungsabbau und mikrostrukturellen Veränderungen für die Lebensdauervorhersage schwingbeanspruchter Schweißverbindungen
Authors: Lachmann C. , Nitschke-Pagel Th. , Wohlfahrt H. 
Published: February 2022

Abstract
Mit Hilfe der hier vorgestellten Untersuchungen soll die Lebensdauervorhersage für Schweißverbindungen in Bauteilen durch die Erfassung ermüdungsrelevanter Werkstoffveränderungen verbessert werden. Der in den unterschiedlichen Schweißnahtbereichen von Proben und Großbauteilen sowie in Schweißsimulationsproben röntgenographisch festgestellte Eigenspannungsabbau und stattfindende mikrostrukturelle Werkstoffveränderungen lassen sich last-, gefüge- und schwingspielzahlabhängig einordnen. Die Einbeziehung örtlicher Spannungsspitzen in die Berechnung von Vergleichsspannungen und eine Erweiterung des Modellansatzes nach Bergström ermöglichen eine schlüssige Bewertung des mehrachsig stattfindenden Eigenspannungsabbaus im Schweißnahtbereich. Mittels einer Vielparameter-Regressionsanalyse mikromagnetisch gemessener Kenngrößenverläufe können ermüdungsbedingte Werkstoffveränderungen der Restlebensdauer zugeordnet werden. Auf der Basis von Wöhlerversuchen wurden Methoden entwickelt, über äquivalente Probenversuche die Restlebensdauer einer Schweißnaht im Großbauteil zu ermitteln. Die Berücksichtigung des röntgenographisch gemessenen Eigenspannungsabbaus verbessert die Vorhersagegenauigkeit einer rechnerischen Lebensdauervorhersage auf Basis des örtlichen Konzepts.
Crystal orientation and residual stress in TiN film by synchrotron radiation
Authors: Hanabusa Takao , Kusaka Kazuya , Nishida Masayuki , Matsue Tatsuya , Sakata Osami 
Published: February 2022

Abstract
The residual stress in a TiN film, the thickness of which is less than 1 µm, deposited by arc ion plating was measured using the SPring-8 synchrotron radiation facility installed at Japan Synchrotron Radiation Research Institute (JASRI). Films thicker than 300 nm have a {111} texture, whereas those with a thickness of 100 nm have a relatively random orientation. Instead of the conventional laboratory X-ray equipment, ultrabright synchrotron radiation can be used to precisely measure the residual stress in thin films with a thickness of 100 to 800 nm. The residual stress in thicker TiN films is about 7 GPa in compression and it is not affected by the film thickness. The slightly small compressive stress in a film of 100 nm in thickness may be due to the different crystal orientations in the film.
Fatigue crack nucleation at grain boundaries – experiment and simulation
Authors: Vehoff Horst , Nykyforchyn Andrii 
Published: February 2022

Abstract
Fatigue crack nucleation at grain boundaries near the endurance limit was examined combining the results of the fatigue tests with local orientation measurements and with finite element (FE) calculations. Bicrystals and coarsegrained thin sheets were examined in which the orientation and inclination of each boundary could be measured directly. These results were used as input for the FE calculation in which the stress concentrations near the boundaries were calculated. In the fatigue tests, the boundaries, at which the first cracks nucleate, where measured by a replica technique. A comparison of the experimental results with the predictions of the FE calculation yields that the cracks nucleated and propagated along the boundaries with the largest stress concentration. Cracks which hit a boundary with a lower stress concentration either stop or propagate transgranularly, depending on the local stress concentration given by the microstructure. From these results, it can be concluded that elastic strain incompatibilities combined with the microstructure (grain size and orientation) can be used to predict the crack nucleation sites and the scatter in lifetime for fatigue near the endurance limit.
Fatigue and fracture-induced defect structures of metals investigated by positron microscopy
Authors: Egger W. , Kögel G. , Sperr P. , Triftshäuser W. , Bär J. , Rödling S. , Gudladt H.-J. 
Published: February 2022

Abstract
Defect distributions close to cracks from monotonic and fatigue fractures have been investigated for the first time by positron lifetime studies. The positron beams probe either the depth profile of defects at sub-μm resolution or the lateral distribution of defects at a few μm spatial resolution. Both in pure Cu and in the precipitation-hardened alloy Al 6013, in addition to dislocations, large clusters of up to 30 vacancies were detected close to a fatigue crack exclusively, whereas at monotonic fractures only the annihilation characteristics of dislocations were observed. If this characteristic difference holds as a general rule, then positron lifetime microscopy will provide a simple, quantitative method to distinguish a posteriori monotonic fractures from fatigue fractures without any further fractographic studies.
Deformation and fracture of Nb/α-Al2O3 composites in compression and bending studied by optical methods
Authors: Liu Y. , Kohnle C. , Brunner D. , Rühle M. 
Published: February 2022

AbstractThe fracture behavior of Nb/α-Al2O3composites was investigated both in compression tests and bending tests using an optical full-field method for the observation of strain fields on the metal surfaces. Joints of polycrystalline materials were prepared by high-vacuum diffusion bonding. The building up of the strain near the interface during the tests, finally leading to the fracture, was studied by examining the strain and displacement fields of the whole metal layer. In compression tests, two types of fracture, fracture of alumina and fracture of interfaces, were detected by cross-examination of the stress –strain curve and the strain maps. The fracture of alumina in compression tests was influenced by the Nb layer thickness and can be rationalized by an extension of Cottrell’s model. For four-point bending tests, the results of the strain maps, determined experimentally by means of the optical method, confirmed the strain maps resulting from finite element simulations.
Der dynamische SD-Effekt und der Einfluss auf die Fließortkurve
Authors: Meyer Lothar W. , Hahn Frank 
Published: February 2022

Abstract
Biaxiale dynamische Werkstoffuntersuchungen des Einsatzstahls 20MoCrS4 werden unter kombinierter Zug/ Druck –Torsions-Belastung an dünnwandigen Rohrproben durchgeführt. Es wird eine Auswertemethode vorgestellt, mit der der Fließort bei vorgegebenem festen Verhältnis von wahrer Dehnung zur Scherung eindeutig bestimmt werden kann. Die Untersuchungen zeigen, dass der Fließort von der Formänderungsgeschwindigkeit abhängig ist. Höhere Belastungsgeschwindigkeiten führen zur Ausdehnung der Fließortkurve und zur Verschiebung des Mittelpunktes der Ellipse. Damit wird der dynamische SD (strength differential)-Effekt) auch unter biaxialer Beanspruchung nachgewiesen. Für die Finite-Elemente-Methode hat das zur Folge, dass für eine präzise Simulation plastischer Vorgänge unbedingt der Geschwindigkeitseinfluss auf die Veränderung der Fließfläche berücksichtigt werden muss.
Einfluss der Umformgeschwindigkeit und -temperatur auf das Fließverhalten metallischer Werkstoffe
Authors: El-Magd Essam , Abouridouane Mustapha 
Published: February 2022

Abstract
Das Fließ- und Bruchverhalten der Al-Legierung AA7075-T7351, der Mg-Legierung AZ80 und der Ti-Legierung TiAl6V4 wird im quasistatischen und dynamischen Druckversuch bei Umformgeschwindigkeiten im Bereich 0.001 − 5000 s−1 und Temperaturen von Raumtemperatur bis zu 450 C untersucht. Zur Beschreibung des Geschwindigkeits- und Temperatureinflusses auf das mechanische Materialverhalten im Druckversuch können konstitutive Stoffgesetze, deren Parameter aus den Versuchsergebnissen bestimmt werden, herangezogen werden. Diese Stoffgesetze sollen in die Finite-Element-Simulation implementiert werden, um die lokalen Spannungs- und Verzerrungszustände zum Zeitpunkt des Bruchs zu ermitteln. Mit Hilfe der experimentell ermittelten Fließkurven wird der Einfluss von Umformgeschwindigkeit und Temperatur auf den Bruchstauchgrad bestimmt. Ergänzende metallographische Untersuchungen geben darüber hinaus Aufschluss über Schädigungsbeginn, -art und -entwicklung im verformten Material.
Thermozyklisches Kriechen einer kurzfaserverstärkten Aluminium-Kolbenlegierung
Authors: Schnabl Andreas , Degischer Hans Peter 
Published: February 2022

Abstract
Die mit Saffil®-Fasern verstärkte Kolbenlegierung AlSi12CuMgNi wird bei konstanten Lastniveaus im Bereich zwischen 50 und 300 °C thermisch zykliert, bis sie bricht. Durch die Widerstandserwärmung in der ,,Gleeble 1500” – Apparatur sowie durch die Abkühlung mit Druckluft können dabei Aufheiz- bzw. Abkühlraten von 12,5 K/s erreicht werden. Die Verstärkung mit Kurzfasern bewirkt bei allen Proben eine Erhöhung der Lebensdauer und eine Verringerung der minimalen Kriechrate, wobei der Einfluß der Wärmebehandlung verglichen mit den unverstärkten Proben vernachlässigbar wird. Die Wirkung der Kurzfaserverstärkung wird mit modifizierten Werkstoffgesetzen für isothermes Kriechen beschrieben.
Modeling of deformation behavior of copper under equal channel angular pressing
Authors: Baik Seung Chul , Hellmig Ralph Jörg , Estrin Yuri , Kim Hyoung Seop 
Published: February 2022

Abstract
The deformation behavior of copper during equal channel angular pressing (ECAP) was calculated using a three-dimensional version of a constitutive model based on the dislocation density evolution. Finite element simulations of the variation of the dislocation density and the dislocation cell size with the number of ECAP passes are reported. The calculated stress, strain and cell size are compared with the experimental data for Cu deformed by ECAP in a modified route-C regime. The results of finite element (FE) analysis were found to be in good agreement with the experiments. After a rapid initial decrease down to about 200 nm in the first ECAP pass, the average cell size was found to change little with further passes. Similarly, the strength increased steeply after the first pass, but tended to saturate with further pressings. The FE simulations also showed strain non-uniformities and the dependence of the resulting strength on the location within the workpiece.
Determination of the local oxygen distribution in a commercial titanium alloy by 3-dimensional atom probe
Authors: Reissig Lutz , Czubayko Ulrich , Wanderka Nellia , Völkl Rainer , Glatzel Uwe 
Published: February 2022

AbstractThe local oxygen concentration of titanium alloys, such as Ti6Al4V, is of great interest but experimentally difficult to determine. One method to measure the local distribution with atomic level resolution is the 3-dimensional atom probe. We show a way how to prepare Ti6Al4V samples and present and discuss first results.
Microstructure and electrochemical properties of FeCoNiCuZn high-entropy alloy films by DC electrodeposition
Authors: Wang Ziyao , Huo Jiaxiang , Luan Xuezhu , Sun Shineng , Ma Guofeng 
Published: February 2022

Abstract
High-entropy alloys show great potential for industrial application because of their excellent physical and chemical properties. In this work, a simple DC electrodeposition method was introduced to prepare FeCoNiCuZn high-entropy alloy films on a 304 steel substrate. The phase composition, micromorphology, element composition and electrochemical properties of the films were characterized, analyzed and discussed, which provided reference and inspiration for preparing high-entropy alloy two-dimensional materials by electrochemical methods.
Testing Investment Forecast Efficiency with Forecasting Narratives
Authors: Foltas Alexander 
Published: February 2022

Abstract
I analyze the narratives that accompany business cycle forecasting reports of three German institutes using topic models. To this end, I gather multiple similar topics into different economic subject categories, allowing me to map shifting prioritizations within and between these subjects. Subsequently, I examine whether forecasting narratives contain additional information not captured by traditional indicators and include them in a random forest-based investment-forecast efficiency analysis. I find multiple correlations between narratives and forecast errors and conclude that forecasters inefficiently incorporate qualitative information in these cases. I raise the idea that further investigations with more precise identification of forecasting narratives could improve qualitative information processing or lead to scientific guidelines for forecast adjustments.
Effect of thermal annealing on the structural and optical properties of TiO2 nanostructures**
Authors: Hassan Ahmed T. , Hassan Ehssan S. , Abdulmunem Oday M. 
Published: February 2022

Abstract
In this work, TiO nanostructure films were deposited via vacuum thermal evaporation at a temperature of 80°C. The TiO thin films were annealed under vacuum for 1 h at three different degrees (200, 300, and 400°C) in addition to the thin film prepared at 80°C. X-ray Diffraction (XRD) showed that all the deposited and annealed TiO films had anatase polycrystalline diffraction patterns with a predominant reflection of the (200) plane. As a result, the particle size increased with annealing temperature. Scanning Electron Microscopy (SEM) measurements showed that at the annealed temperature of 200°C, the shape of the TiO nanostructures began to change from a condensed cluster distribution to a conical shape. As the annealing temperature was increased to 400°C, all the conical shapes transformed into clear spherical shapes. The spherical shapes recorded 45 (nm) height and (20) (nm) base width. Optical measurements were performed using Ultraviolet-Visible spectroscopy (UV-Vis). The transmittance is reduced from 79.63% for the TiO sample prepared at 80°C to 71.91% for the TiO sample annealed at 400°C. The optical energy gap values decrease from 3.279 eV for the prepared TiO sample at 80°C to 3.115 eV for the TiO sample annealed at 400°C.
Forming evolution of titanium grade2 sheets
Authors: Tekin Merve , Ertan Rukiye , Özgül Hande Güler 
Published: February 2022

Abstract
Titanium and its alloys take attention, especially in aerospace, automotive, and biomedical applications because of their strength, corrosion resistance, and biocompatibility. Titanium components, in general, are produced by sheet metal forming. However, the springback effect is a critical problem in the forming process due to difficult formability of titanium sheets. In the present study, the hot forming process was applied to sheets to investigate the effect of deformation temperature on microstructure, mechanical properties, and springback behavior of commercially pure grade 2 titanium sheets. The springback angles were measured at the CAD model after the sheets were scanned by the 3D scanner. The tensile test, hardness measurements, and microstructural analysis were examined by using specimens that were cut from the sidewall and the bottom of the deformed sheet as U-profile. The results reveal that the microstructure is substantially changed, and the springback is reduced with increasing temperature; thus, optimum results were obtained compared to the data obtained at room temperature.
Effect of Cloisite 15A on the mechanical properties of an abaca-based composite
Authors: Anandraj Mohan Kumar , Rathanasamy Rajasekar , Rathinasamy Parameshwaran , Palaniappan Sathish Kumar 
Published: February 2022

Abstract
The combined effect of resin containing nanoclay along with natural fibers elevates the mechanical properties. In addition, the dispersion of nanoclay at the fiber-matrix interface would create strong physical interaction between the two. The significant enhancement in mechanical properties is achieved for the composite containing 30 wt.% abaca fiber content and 2 wt.% nanoclay, which is treated by 8 vol.% NaOH concentration. The enhancement in the mechanical properties can be attributed to the wettability of fiber by the matrix, homogeneous distribution of fibers and nanoclay in the matrix phase and physical interaction between reinforcement and matrix. Increase in the addition of abaca fiber and nanoclay beyond the above mentioned content leads to drop in the mechanical properties. This can be due to many nanoclay agglomerates are not broken down to nano scale during preparation, it may also be the reason for drop in the mechanical properties.
Effect of austempering treatment on metallurgical structure of Ce inoculated X210Cr12 cold work tool steel
Authors: Teker Tanju , Yilmaz S. Osman , Eruslu S. Özmen 
Published: February 2022

Abstract
The effect of austempering treatment on metallurgical structure of X210Cr12 cold work tool steel inoculated with Ce was researched. Microstructural changes, elemental characterizations, and phase formations of the samples were examined by using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, elemental mapping, and microhardness test. Ce inoculation reduced the grain size, and the austenitizing temperature had a huge effect on the austenitizing process. The austenitizing process increased the hardness by reducing the retained austenite, but the degree was dependent on the austenitization temperature. The austempering treatment improved the hardness resistance by depositing more equal carbides composed of nano-sized carbides. High austempering period and increase of austempering temperature decreased the homogeneity and hardness of the microstructure.
Analysis of residual stresses and distortions of a titanium alloy ring-stiffened cylindrical shell
Authors: Ge Keke , Yu Yue , Xu Qiang , Zhang Aifeng , Feng Shichao 
Published: February 2022

Abstract
Ring-stiffened cylindrical shell is the main pressure structure of underwater carrier equipment, and the residual stress and deformation introduced by welding of ring-ribbed frame and cylinder body pose a great threat to the performance and safety of the structure. In this paper, finite element software is used to numerically simulate the residual stress and deformation caused by fillet welding. The influence of welding position, constraint tooling and post-weld heat treatment PWHT on the residual stress and deformation is analyzed systematically. The results show that the gravity has little effect on the welding residual stress and deformation, but it has a significant impact on deformation uniformity. Under the action of restraint, the welding distortion is effectively controlled, but it will lead to the increase of the overall stress level of the structure simultaneously. Heat treatment can dramatically diminish the welding residual stress at the expense of deformation, which may result in structural maladjustment.
Corrosion behavior of 316 stainless steel, copper, and brazed joint in lithium bromide solution at different temperatures
Authors: Zhang Xiang , Qiu Yunlong , Zhu Weifei , Yu Xinhua , Cao Yanan , Wang Xiaohuan , Liang Yanqin 
Published: February 2022

Abstract
Lithium bromide (LiBr) corrosion on austenitic 316 stainless steel (AISI 316) and copper will largely determine the overall performance of refrigeration compression systems. In this work, the corrosion behavior of AISI 316, copper, and brazed joint was studied in LiBr solution at different temperatures by using the polarization curve and electrical impedance spectroscopy. The morphology and chemical composition of the samples before and after corrosion were characterized to elucidate the corrosion mechanism. The passivation film of AISI 316 stainless steel is more prone to breakdown as the temperature increases, and the corrosion resistance of copper and brazed joint also decreases with the increasing temperature. Zero-resistance ammeter technology was employed to analyze the effect of temperature on galvanic corrosion. The degree of galvanic corrosion increases with temperature for all galvanic pairs (AISI 316-Cu, AISI 316-brazed joint, and Cu-brazed joint). For AISI 316-Cu and AISI 316-brazed joint galvanic pairs, AISI 316 functions as the cathode, while copper or brazed joint serves as the anode. For the Cu-brazed joint pair, the brazed joint is preferred to be corroded at room temperature, whereas at 50 and 75 °C, copper corrosion occurs in priority.
Control of the bainitic structure for a wear-resisting hard-faced rail track
Authors: Suwanpinij Piyada , Thonondaeng Thanaporn , Kumma Parinya , Suksawat Bandit , Lothongkum Gobboon 
Published: February 2022

Abstract
Carbide-free bainite with filmlike retained austenite structure has been reported for its higher wear resistance and toughness compared with conventional bainite and pearlite structure. In order to take advantage from such beneficial structure, this study employs the surface welding method with self-shielded wire electrode containing low carbon (0.15 mass%), high silicon, and nickel on two pearlitic rail steels, R260 and R350HT. The preheating temperature and other welding parameters were carefully selected to avoid too high dilution, which leads to martensite formation. The weld metal, heat-affected zone, and base material were investigated by scanning electron microscopy. Microhardness and wear tests were carried out to ensure improved properties after the surface repair. The results show significant improvements in hardness and wear rate in weld metal compared with the base material.
Online monitoring of 3D printing of steel via optical emission spectroscopy
Authors: Pignatelli Giuseppe , Strasse Anne , Gumenyuk Andrey , Gornushkin Igor 
Published: February 2022

Abstract
Additive manufacturing by laser metal deposition (LMD) requires continuous online monitoring to ensure quality of printed parts. Optical emission spectroscopy (OES) is proposed for the online detection of printing defects by monitoring minute variations in the temperature of a printed spot during laser scan. A two-lens optical system is attached to a moving laser head and focused on a molten pool created on a substrate during LMD. The light emitted by the pool is collected by an ultraviolet–visible (UV–vis) spectrometer and processed. Two metrics are used to monitor variations in the surface temperature: the spectrally integrated emission intensity and correlation coefficient. The variations in the temperature are introduced by artificial defects, shallow grooves, and holes of various widths and diameters carved on a substrate surface. The metrics show sufficient sensitivity for revealing the surface defects, except for the smallest holes with an under-millimeter diameter. Additionally, numeric simulations are carried out for the detection of emission in the UV–vis and near-infrared (NIR) spectral ranges at various surface temperatures. It is concluded that both the metrics perform better in the NIR range. In general, this work demonstrates that spectrally resolved OES suits well for monitoring surface defects during 3D metal printing.