Influence of surface recrystallization on the low cycle fatigue behaviour of a single crystal superalloy

This paper investigated the effect of surface recrystallization (RX) on the low cycle fatigue (LCF) behaviour of a single crystal (SX) superalloy. LCF tests on both raw and recrystallized samples showed that fatigue life was significantly reduced by surface RX. Fractography indicated that fatigue cracks initiated from the casting defects in RX layer and multiple crack initiations were commonly observed. Moreover, RX grains exhibited predominantly transgranular cracking, in contrast to the intergranular fracture reported in literature. The fatigue crack propagation behaviour was discussed in light of fracture mechanics and crack growth life model. The fatigue cycles required to penetrate RX layer were estimated to be about one magnitude lower than that in forming an equivalent crack in SX specimens. It is suggested that the earlier crack initiation and promoted crack propagation in RX layer, as well as the trend of multiple initiations, are responsible for the fatigue degradation by RX.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110545/1/ffe12236.pd

Perceived and mentally rotated contents are differentially represented in cortical depth of V1

Primary visual cortex (V1) in humans is known to represent both veridically perceived external input and internally-generated contents underlying imagery and mental rotation. However, it is unknown how the brain keeps these contents separate thus avoiding a mixture of the perceived and the imagined which could lead to potentially detrimental consequences. Inspired by neuroanatomical studies showing that feedforward and feedback connections in V1 terminate in different cortical layers, we hypothesized that this anatomical compartmentalization underlies functional segregation of external and internally-generated visual contents, respectively. We used high-resolution layer-specific fMRI to test this hypothesis in a mental rotation task. We found that rotated contents were predominant at outer cortical depth bins (i.e. superficial and deep). At the same time perceived contents were represented stronger at the middle cortical bin. These results identify how through cortical depth compartmentalization V1 functionally segregates rather than confuses external from internally-generated visual contents. These results indicate that feedforward and feedback manifest in distinct subdivisions of the early visual cortex, thereby reflecting a general strategy for implementing multiple cognitive functions within a single brain region

Use of mechanical circulatory support in patients with non-ischaemic cardiogenic shock

Aims Despite its high incidence and mortality risk, there is no evidence-based treatment for non-ischaemic cardiogenic shock (CS). The aim of this study was to evaluate the use of mechanical circulatory support (MCS) for non-ischaemic CS treatment.Methods and results In this multicentre, international, retrospective study, data from 890 patients with non-ischaemic CS, defined as CS due to severe de-novo or acute-on-chronic heart failure with no need for urgent revascularization, treated with or without active MCS, were collected. The association between active MCS use and the primary endpoint of 30-day mortality was assessed in a 1:1 propensity-matched cohort. MCS was used in 386 (43%) patients. Patients treated with MCS presented with more severe CS (37% vs. 23% deteriorating CS, 30% vs. 25% in extremis CS) and had a lower left ventricular ejection fraction at baseline (21% vs. 25%). After matching, 267 patients treated with MCS were compared with 267 patients treated without MCS. In the matched cohort, MCS use was associated with a lower 30-day mortality (hazard ratio 0.76, 95% confidence interval 0.59-0.97). This finding was consistent through all tested subgroups except when CS severity was considered, indicating risk reduction especially in patients with deteriorating CS. However, complications occurred more frequently in patients with MCS; e.g. severe bleeding (16.5% vs. 6.4%) and access-site related ischaemia (6.7% vs. 0%).Conclusion In patients with non-ischaemic CS, MCS use was associated with lower 30-day mortality as compared to medical therapy only, but also with more complications. Randomized trials are needed to validate these findings.[GRAPHICS

Intermetallische NiAl-Komponenten fuer Systeme zur umweltfreundlichen Energiewandlung. Teilprojekt: Gusstechnologien Abschlussbericht

The potential of intermetallic NiAl base materials was to be utilized, e.g. as heat shields in combustion chambers. In this sub-project, DPC-B worked on fine casting technologies and powder metallurgical processes for producing testable test bodies and components. Isotropic material characteristics were to be achieved within a component. The main processes were metal-cutting and electrochemical processes, as well as forming and joining processes. A particular aspect is the development of thermally sprayed coatings of intermetallic NiAl powders.Im Rahmen dieses Verbundforschungsvorhabens sollte das Potential der intermetallischen NiAl-Basiswerkstoffe technisch nutzbar gemacht werden. Durch gezielte Legierungsmodifikation und optimierte Herstellungsprozesse sollten die NiAl-Cr-(IP27) und NiAl-TaCr-Werkstoffe (IP75) so entwickelt werden, dass thermisch hochbelastete Gasturbinenkomponenten, wie sie z.B. Hitzeschilde im Bereich der Brennkammer darstellen, hergestellt und durch Einsatz in einer Gasturbine erprobt werden koennen. Hierzu sollten im Teilprojekt 'Gusstechnologie' bei DPC-B sowohl durch das Feingussverfahren als auch durch pulvermetallurgische Prozesse prueffaehige Probekoerper und Bauteilkomponenten hergestellt werden. Im Bauteil werden durch schmelz- und pulvermetallurgische Herstellungstechniken weitgehend isotrope Materialeigenschaften eingestellt. Als wichtige Verfahren fuer eine Komponentendarstellung sind weiterhin spanabhebende und elektrochemische Bearbeitungsverfahren sowie Umformungs- und Fuegeverfahren anzusehen. Eine Besonderheit der Verarbeitungstechnologien ist die Entwicklung von thermisch gespritzten Schutzschichten aus intermetallischen NiAl-Pulvern. (orig.)SIGLEAvailable from TIB Hannover: F02B1492 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

MARCKO Grosse Gasturbinenschaufeln. Teilprojekt: Defekte in gerichtet erstarrten Gefuegen Abschlussbericht

In big gas turbines, small structural inhomogeneities - whose probability of occurrence increases proportionately with the dimensions of the turbine blades -may reduce blade life. Investigations of the production mechanisms of defects during casting are therefore of vital importance for economically efficient design. This sub-project coprised the production of test pieces for investigation of casting defects and the application of the results on the casting of big DS and SC blades. Scientific and technical goals were defined as follows: Definition of appropriate methods and critical parameter sets of the casting and solidification process for selective production of structural anomalies. Development of specific technologies for creating reproducible defects. Establishment of the nucleation technique also for orientations far from the preferred direction. Production of test pieces of different geometries, free of defects and with defined defects, by monocrystalline directional drilling, for calculation of design curves by the project partners. Verification of existing models for numeric simulation of solidification by comparing them with the results of the casting experiments. Application of the findings to other monocrystalline materials. Application of the results in practical production.Innerhalb der Gesamtzielsetzung des Verbundprojektes 'Grosse Turbinenschaufeln neuer Technologie fuer umweltschonende Gasturbinen' zielte das Teilvorhaben 'Defekte in gerichtet erstarrten Gefuegen' auf die Erhoehung der Ausbringrate bei der Herstellung grosser einkristallin gerichtet erstarrter Gasturbinenschaufeln nach dem Feingussverfahren ab. Geringe giessbedingte Gefuegeinhomogenitaeten, deren Wahrscheinlichkeit proportional mit den Abmessungen der Turbinenschaufeln steigt, koennen zu lebensdauerreduzierenden Faktoren werden. Der Untersuchung der Entstehungsmechanismen von Giessdefekten kommt daher eine entscheidende Bedeutung bei der oekonomischen Verfahrensauslegung zu. Hauptarbeitsziel des Teilvorhabens war es, neben der Herstellung von Probekoerpern fuer Untersuchungen zur Festlegung von zulaessigen bzw. unzulaessigen Gefuegedefekten die dabei gewonnenen Erkenntnisse auf die Giesstechnik grosser DS- bzw. SC-Schaufeln zu uebertragen. Die wesentlichen wissenschaftlichen und technischen Arbeitsziele waren: - Definition geeigneter Methoden und kritischer Parametersaetze des Giess- und Erstarrungsprozesses fuer die gezielte Einstellung von Gefuegeanomalien, - Entwicklung spezieller Techniken zur reproduzierbaren Erzeugung dieser Gefuegefehler, - Etablierung der Ankeimtechnik auch fuer die Orientierungen weit ab von der Vorzugsrichtung, -Bereitstellung von defektfreien und definiert defektbehafteten einkristallin gerichtet erstarrten Probekoerpern unterschiedlicher Geometrie fuer die Ermittlung von Designkurven bei den Projektpartnern, - Verifikation bestehender Modelle zur numerischen Erstarrungssimulation durch Vergleich mit Ergebnissen aus den Giessversuchen, - Uebertragung der am ausgewaehlten Versuchswerkstoff CMSX-4 ermittelten Erkenntnisse hinsichtlich Fehlerentstehung und Giesstechnik, wie z.B. die Ankeimmethode, auf andere aktuelle Einkristallwerkstoffe, - Nutzung der gewonnenen Erfahrungen ueber die gezielte Fehlereinstellung, um im Umkehrschluss bei der Fertigung von grossen stengel- und einkristallin gerichtet erstarrten Turbinenschaufeln Fehlergroesse und -haeufigkeit positiv beeinflussen zu koennen. (orig.)Available from TIB Hannover: F02B1490 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

Hochintegrierte Leitschaufelsegmente der naechsten Generation auf Basis des Liquid Metal Cooling Prozesses Abschlussbericht

A knowledge base for producing guide vane segments by the new liquid metal cooling process (LMC) was developed in this project. Apart from extending the analytical possibilities for analysis of tin and providing information on the fate of tin in nickel base alloys, the focus was on the parameters that influence the process result.Im Rahmen des Verbundprojektes wurde eine Wissensbasis zur Herstellung von Leitschaufelsegmenten mit dem neuartigen Liquid Metal Cooling Verfahren (LMC) geschaffen. Neben einer Erweiterung der analytischen Moeglichkeiten zur Bestimmung von Zinn und den Erfahrungen zum Verbleib von Zinn innerhalb von Nickelbasislegierungen ist hier im wesentlichen ein umfassendes Verstaendnis der verschiedenen Einflussgroessen auf das Prozessergebnis zu nennen. (orig.)SIGLEAvailable from TIB Hannover: F03B1075 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

Impella support compared to medical treatment for post-cardiac arrest shock after out of hospital cardiac arrest

AIMS: To compare survival outcomes of Impella support and medical treatment in patients with post-cardiac arrest cardiogenic shock related to acute myocardial infarction (AMI). METHODS: Retrospective single center study of patients resuscitated from out of hospital cardiac arrest (OHCA) due to AMI with post-cardiac arrest cardiogenic shock between September 2014 and September 2016. Patients were either assisted with Impella or received medical treatment only. Survival outcomes were compared using propensity score-matched analysis to account for differences in baseline characteristics between both groups. RESULTS: A total of 90 consecutive patients with post-cardiac arrest shock due to AMI were included; 27 patients in the Impella group and 63 patients in the medical treatment group. Patients with Impella support had a longer duration of low-flow time (29.54 ± 10.21 versus 17.57 ± 8.3 min, p \u3c 0.001), higher lactate levels on admission (4.75 [IQR 3.8-11] versus 3.6 [IQR 2.6-3.9] mmol/L, p = 0.03) and lower baseline systolic LVEF (25% [IQR 25-35] versus 45% [IQR 35-51.25], p \u3c 0.001) as compared to patients without circulatory support. After propensity score matching, patients with Impella support had a significantly higher survival to hospital discharge (65% versus 20%, p = 0.01) and 6-months survival (60% versus 20%, p = 0.02). CONCLUSION: The results from our study suggest that Impella support is associated with significantly better survival to hospital discharge and at 6 months compared to medical treatment in OHCA patients admitted with post-cardiac arrest cardiogenic shock and AMI