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Transverse through-wall airfoil cracking was found in a row 3 twin turbine vane segment of a type used in heavy-duty gas turbine engines for power generation. A laboratory investigation determined liquation cracking (LC), a hot cracking mechanism, as the metallurgical cause of failure. As became apparent only after the investigation, the root cause of failure was a malfunctioning plasma gun used for thermal spraying the thermal barrier ceramic top coat onto the subject part.

A metallographic section from the crack area of an exhaust gas turbocharger was supplied by the customer. The shaft made of quenched and tempered low-alloy steel and the charger wheel made of a nickel-based superalloy were joined by laser welding. For design reasons, the root side of the weld contained a geometric notch, at which a high cycle fatigue crack initiated during the test facility operation of the turbocharger. At the time of examination, it went through almost the entire weld root. As a corrective action, it was recommended that the welded joint be replaced by a shrink fit.

The damage case dealt with in the present work relates to a generally less common manufacturing defect that was discovered during its installation. The part was sourced from a supplier. An installation of the defective part in a large gas turbine engine used for energy generation could thus be prevented. The defect, a solidification crack, could have been repaired by welding and the component could have been used for operation. Instead, it was subjected to destructive examinations aiming at identifying what caused the crack. As the component could not possibly perform its function prior to being repaired by welding we are, in any event, talking about a damage case. The solidification crack initiated at a site of oxide infiltration. It was thus clearly a casting defect. The respective supplier was advised to reduce the content of non-metallic inclusions by the use of ceramic filters when the material is poured into the shell mold and a better control of the vacuum in the casting furnace.

When selecting case studies for presentation in this section Failure Analysis of Practical Metallography, the authors of this contribution asked themselves time and again what conditions actually constitute a component failure. Conventional wisdom has it that a failure occurred when a component or assembly lost its function intended by design. The authors readily admit that this is decidedly not the case for the “failure” presented in this contribution. Not only did no failure occur (the component was successfully used in engine service for the intended operating time), but the subject turbine blade did not loose its intended function by any stretch of the imagination. Why is this case study then presented here anyway? Because the evaluation and assessment of severity of indications found upon non-de structive testing of the subject turbine blade was only possible after destructive metallurgical investigation. One could jokingly concede that the blade definitely lost its function after metallographic cut-up. In any case, in the “failure case” presented in this contribution, the engineering department did not dare to release the subject turbine component for renewed engine service after refurbishment, since indications were detected that could not be properly assessed, without destroying the part; hence the subject component was not fit for engine service. The inclined reader may himself decide whether this fact makes it a component failure.

Protector tubes for temperature sensors were welded onto experimental gas turbine compressor blades. While the blades were made of a high alloy hard-martensitic stainless chromium steel, a high alloy metastable austenitic stainless steel was used for the tiny protector tubes. The dissimilar weld joint was applied using manual GTAW. A large amount of blocky delta ferrite formed in the HAZ immediately adjacent to the fusion line, on the side of the martensitic steel. Delta ferrite in such dissimilar welds might detrimentally affect the mechanical properties of the weld joint. It was therefore recommended not to use the affected experimental blades in test engine service. Even though no failure occurred in this case, one was prevented by declaring the subject instrumented parts unfit for test engine service.

Linear Friction Welding (LFW) is a rarely used joining technology. To test the suitability of this solid-state process for hot cracking-sensitive nickel base superalloys, tests were performed using conventionally and directionally cast slabs of Alloy 247. Since LFW does not involve melting of the weld flanks, there were some expectations that this special welding technique could overcome the poor weldability of Alloy 247. However, all tested specimens failed by liquation cracking (LC) within the Weld Center Zone (WCZ) at the directionally cast side.

Several high-pressure lift oil pump failures were reported from the field. These assemblies are used to inject lubrication oil into the sliding bearings of heavy rotating turbomachinery equipment, such as steam and gas turbine rotors, often weighing in excess of a hundred tons. This ensures that the rotor shaft “floats” on a lube oil film even at low rotational speeds, when hydro-dynamic lubrication conditions have not yet been fully established. A fractured spline shaft, which was the driven shaft of one of the failed pumps, was received from the client for the determination of the metallurgical root cause of failure. The subject spline shaft failed due to torsional overload. This cracked the hardened case and initiated high cycle fatigue (HCF) cracking as secondary damage. The main fatigue cracks were nucleated at overload fractures in the hardened case, in the fillet radii at the base of the teeth of the spline shaft. No evidence of any material defects that could have contributed to the failure or could even have been causative for it was found.

Leadership and management skills are critical for health programs to deliver high-quality interventions in complex systems. In malaria-eliminating countries, national and subnational health teams are reorienting strategies to address focal transmission while preventing new cases and adapting to decentralization and declines in external financing. A capacity-strengthening program in two regions in Namibia helped malaria program implementers identify and address key operational, political, and financial challenges. The program focused on developing skills and techniques in problem-solving and teamwork, engaging decision-makers, and using financial evidence to prioritize domestic resources for malaria through participatory approaches. Results of the program included an observed 40% increase in malaria case reporting, 32% increase in reporting and tracing of imported malaria cases, 10% increase in malaria case management, integration of malaria activities into local operational plans, and an increase in subnational resources for malaria teams. To promote program sustainability beyond the implementation period, key program aspects were institutionalized into existing health system structures, program staff were trained in change leadership, and participants integrated the skills and approaches into their professional roles. A capacity-strengthening program with joint focus on leadership, management, and advocacy has potential for application to other health issues and geographies.

The case of damage presented here relates to the switching bridge of a medium voltage switch, a so-called make switch. Such assemblies are used for fast high current switching operations in medium voltage technology. The copper switching bridge failed due to low-cycle fatigue fractures symmetrically initiated where the transition radius between the copper bridge and the shaft was too sharp. The primary cause of the damage was the fact that the design principle of avoiding too sharp transition radii was needlessly violated where there were no apparent structural limitations. It is remarkable that, time and again, the violation of the same simple design rules causes component damages. The respective simple principles of good design practice thus violated are the same in virtually any mechanical engineering sector.

Large hot-rolled rings made of Alloy 718 were used as semi-finished product for turbomachinery components. Samples taken from one such ring exhibited non-uniform mechanical properties, partly below specified limits. Too high a volume fraction of delta phase in the microstructure was identified as the metallurgical root cause of failure. The case study presented in this contribution shows that such deviation from specified material properties does indeed constitute component failure, since the subject raw forging could not be used as is for fabrication of rotating equipment for gas turbine engines. To salvage the subject part and avoid having to scrap it at high cost, successful heat treatment tests were performed in the laboratory with the aim of eliminating delta phase to an extent, sufficient for property recovery. Heat treatment parameters were derived and recommended to the client. They were successfully applied before final machining and the subject hot-rolled ring was salvaged.

Metallic heat shields, used in combustion chambers of heavy-duty gas turbine engines and made of nickel-based superalloys, were accidentally heat treated during fabrication, using wrong parameters. There were concerns about embrittlement. Nondestructive metallurgical material characterization using the replica technique verified embrittlement by secondary phases. In spite of this, it was recommended to the client to use the affected parts as is, this on the grounds that no grain growth was observed and hardness was not elevated. While the case study presented in this contribution may appear trivial at first sight, it interestingly shows how metallographic examinations may sometimes be performed non-destructively, without sacrificing any engine components. The inclined reader should also note the superb quality of the photomicrographs presented in this contribution. They were taken from replica foils, not actual metallographic sections.

One definition of failure is that the subject component lost its function intended by design. The case study presented in this contribution is admittedly borderline in this respect. The parts in question have never seen any engine service and were taken straight out of fabrication, namely the weld shop. Welded components for turbomachinery exhibited excessive areas of lack of fusion in welds. Some of the subject assemblies were put in engine service in non-OEM machinery, without experiencing any failures. This was before weld imperfections were detected in fabrication. However, even though faulty components did not yet fail in service, the presented case is still categorized as a failure case, since the subject weld imperfections were so severe that failure had to be considered imminent. This

Failure analysts are sometimes surprised to find well-known metallurgical failure mechanisms at work in completely unexpected places. This contribution is an eloquent example for just such an incidental convergence of well-known failure mechanism and fabrication process where it was not reported to have previously occurred. Liquid Metal Embrittlement (LME) was observed in Narrow Gap Welds (NGW) produced for Welding Procedure Qualification (WPQ). The embrittling liquid metal was copper in this case. It is believed to have originated from copper backing used for weld pool protection. It was recommended to replace copper backing with ceramic weld pool protection.

DNA metabarcoding is increasingly important for studying feeding interactions, yet it remains unresolved whether reporting read counts or occurrences is to be preferred. To address this issue for gut content samples, basic experimental data on the relationship between read numbers and initial prey DNA amounts and how both change over digestion time is needed. Using regurgitates of the carabid Pseudoophonus rufipes the digestion of Taraxacum officinale seeds was documented for 128 h post-feeding to determine how the number of (1) seed DNA copies and (2) metabarcoding reads change over digestion time, and (3) how they correlate to each other. Additionally, we tested (4) whether PCR cycle-numbers during library preparation affect this correlation. The number of copies and reads both decreased with digestion time, but variation between samples was high. Read and copy numbers correlated when using a library preparation protocol with 35 cycles (R2 = 42.0%), yet a reduction to 30 cycles might significantly improve this correlation, as indicated by additional PCR testing. Our findings show that protocol optimization is important to reduce technical distortions of read numbers in metabarcoding analysis. However, high inter-sample variation, likely due to variable digestive efficiency of individual consumers, can blur the relationship between the amount of food consumed and metabarcoding read numbers.

Supposedly simple cases of failure are most often best suited to communicate the principles of component failure analysis in the field of materials engineering to a wide readership, especially to those peers in the specialist community who are just beginning to familiarize themselves with the subject. The present case of failure relates to components that failed as early as during the assembly, and more specifically, during the final assembly stage of combustion chamber components for heavy-duty gas turbine engines. Hence, they lost their functionality (in fact, the common definition of component failure). At tightening torques of the nuts opposite of the tapered heads as low as below 25 Nm, so-called twistoff bolts which, when welded into combustion chamber sheets, take on the function of stud bolts, sheared off. By way of exception, a materialographic failure analysis could show that the primary cause of the failure was not the component’s design, but the disregard of the drawing specifications during final assembly. However, on a secondary level, design deficiencies had to be mentioned, as untempered welded joints in martensitic chromium steels invariably act as metallurgical notches. If the respective part is subjected to dynamic loads, as is the case in virtually all turbo machinery, they are thus to be avoided.

In this contribution, a case study is presented describing the failure of a combustion chamber assembly in a non-OEM (Original Equipment Manufacturer) gas turbine engine used for power generation. It showed how even advanced fabrication methods, such as Electron Beam (EB) welding, could trigger fatigue fracture, even if there are no material defects, no weld imperfections, no fabrication flaws, and even if everything is within specified limits. As is so often the case in component failures, the fact that failures occur anyway, despite the absence of out-of-spec material properties, and even though there were no fabrication flaws, is attributable to the design; which is often not sturdy enough to withstand unexpected dynamic loading.

Short fillet welds used to fasten a large retainer ring to so-called dog bone seals failed in the turbine exhaust casing of a non-OEM heavy-duty gas turbine engine used for power generation. The subject fillet welds fractured due to high cycle fatigue loading. Neither weld imperfections nor any other material defects were found that could have contributed to the failure. It was concluded that an unfavorable design, specifying very short fillet welds for fastening the dog bone seal segments to the retainer ring, was the root cause of failure. In a purely static loading situation, this design would probably not have failed. However, in a dynamic loading scenario as is the case in any gas turbine engine exhaust, such a design is simply not sturdy enough.

The Covid-19 pandemic has pushed many hospitals to their capacity limits. Therefore, a triage of patients has been discussed controversially primarily through an ethical perspective. The term triage contains many aspects such as urgency of treatment, severity of the disease and pre-existing conditions, access to critical care, or the classification of patients regarding subsequent clinical pathways starting from the emergency department. The determination of the pathways is important not only for patient care, but also for capacity planning in hospitals. We examine the performance of a human-made triage algorithm for clinical pathways which is considered a guideline for emergency departments in Germany based on a large multicenter dataset with over 4,000 European Covid-19 patients from the LEOSS registry. We find an accuracy of 28 percent and approximately 15 percent sensitivity for the ward class. The results serve as a benchmark for our extensions including an additional category of palliative care as a new label, analytics, AI, XAI, and interactive techniques. We find significant potential of analytics and AI in Covid-19 triage regarding accuracy, sensitivity, and other performance metrics whilst our interactive human-AI algorithm shows superior performance with approximately 73 percent accuracy and up to 76 percent sensitivity. The results are independent of the data preparation process regarding the imputation of missing values or grouping of comorbidities. In addition, we find that the consideration of an additional label palliative care does not improve the results.

Hintergrund Die situationsbedingte Verknappung medizinischer Ressourcen endet bei einem Massenanfall von Verletzen (MANV) lageabhängig nicht mit dem Abtransport der Patienten von der Einsatzstelle. Folglich ist in den aufnehmenden Kliniken eine Eingangssichtung erforderlich. Ziel dieser Studie war es im ersten Schritt einen Referenz‐Patientenvignettensatz mit definierten Sichtungskategorien zu erstellen. Dies erlaubte im zweiten Schritt, die rechnergestützte Evaluation der diagnostischen Güte klinischer Sichtungsalgorithmen für MANV-Lagen. Methodik In einen mehrstufigen Bewertungsprozess durch zunächst sechs, später 36 Sichtungsexperten gingen 250 in der Übungspraxis validierte Fallvignetten ein. Diese Algorithmen – unabhängige Expertenbewertung aller Vignetten – dienten als Goldstandard für die Analyse der diagnostischen Güte der folgenden innerklinischen Algorithmen: Manchester Triage System (MTS Modul MANV), Emergency severity Index (ESI), Berliner Sichtungsalgorithmus (BER), die prähospitalen Algorithmen PRIOR und mSTaRT, sowie zwei Projektalgorithmen aus einer Kooperation des Bundesamts für Bevölkerungsschutz und Katastrophenhilfe (BBK) mit dem Haschemitischen Königreich Jordanien – innerklinischer jordanisch-deutscher Projektalgorithmus (JorD) und prähospitaler Sichtungsalgorithmus (PETRA). Jede Patientenvignette durchlief computergestützt eine Sichtung durch alle angegeben Algorithmen, um vergleichend die Testgüte für alle Verfahren zu erheben. Ergebnisse Von den ursprünglich 250 Vignetten konnte eine Sichtungsreferenzdatenbank mit 210 Patientenvignetten algorithmenunabhängig validiert werden. Diese bildeten den Goldstandard für den Vergleich der analysierten Sichtungsalgorithmen. Die Sensitivitäten für die innerklinische Detektion von Patienten der Sichtungskategorie I lagen zwischen 1,0 (BER, JorD, PRIOR) und 0,57 (MANV-Modul MTS). Die Spezifitäten lagen zwischen 0,99 (MTS und PETRA) und 0,67 (PRIOR). Gemessen am Youden-Index ergab sich bei BER (0,89) und JorD (0,88) die beste Gesamtperformance für die Detektion von Patienten der Sichtungskategorie I. Eine Übertriage ist am ehesten bei PRIOR, eine Untertriage beim MANV-Modul von MTS zu erwarten. Bis zum Entscheid SK I benötigen die Algorithmen folgende Schrittanzahlen (Median [IQR]): ESI 1 [1–2]; JorD 1 [1–4]; PRIOR 3 [2–4]; BER 3 [2–6]; mSTaRT 3 [3–5]; MTS 4 [4–5]; PETRA 6 [6–8]. Für die SK II und III besteht ein positiver Zusammenhang zwischen der Schrittanzahl bis zum Entscheid und der Testgüte. Schlussfolgerung In der vorliegenden Studie konnte eine Übertragbarkeit prähospitaler algorithmenbasierter Vorsichtungsergebnisse auf die Ergebnisse klinischer Algorithmen gezeigt werden. Die höchste diagnostische Güte für die innerklinischen Sichtung lieferten BER und JorD, die allerdings auch die meisten Algorithmusschritte bis zum Entscheid benötigen.

International audience; Abstract Carabids are important biological control agents of weeds and other pests in agricultural fields. The carabid community is built upon direct and indirect ecological effects of landscape complexity, field management intensity and biotic components that in interaction make any prediction of community size and composition challenging. We analyse a large-scale sample of 60 European cereal fields using structural equation modelling to quantify the direct effects of field management intensity and the surrounding landscape, and their indirect effect via biotic components, on carabid diversity. Our results highlight that direct and indirect effects of increasing landscape complexity, mediated by trophic resources, mainly affect carabids positively. Field management intensity only ever affects carabids through indirect effects that are generally negative, by suppressing standing weeds and weed seeds. Indirect effects on granivore carabid species depended on weed seed availability, whereas omnivores depended on the availability of both weed seeds and animal prey. Synthesis and applications. A consideration of both the direct and indirect effects of landscape and field management is necessary for predicting carabid communities. These indirect effects, mediated via trophic resources, supports the diversity and abundance of carabid communities and their provision of ecosystem services. Our results show that promoting crop diversity and connectivity to semi-natural habitats will directly enhance carabid communities in farmland by manipulating their migration from source habitats and indirectly by promoting the presence and diversity of their trophic resources. A reduction in field management intensity will preserve local standing weeds and weed seeds, and indirectly support carabid communities. These local and landscape modifications could contribute to improve the natural regulation of pests and weeds by carabids.

Exhaust stack liners of a test rig for gas turbine burners failed locally by ruptured fasteners and fallen-off liner plates. Misalignment of the plating relative to each other and relative to their fasteners caused restraint of the expanding and shrinking liner plates upon start-up and shutdown of the burner rig. The fastening holes of the failed liner plates were not concentric, but misaligned relative to each other and relative to their fastener bolts. This exerted a shear loading on the threads of the fastening bolts, which in turn caused a mean stress shift and damaged the threads of the fasteners by nicking. So pre-loaded, the fastening bolts were not able to withstand the vibratory loads from the flowing exhaust gases and failed due to fatigue.

Elastic sealing elements used in combustion chamber assemblies of heavy-duty gas turbine engines used for power generation fractured from high cycle fatigue failure. The subject assembly was burner rig tested in a special testing facility. It was speculated that the affected spring seals likely failed due to forced excitation during burner rig testing, since no material imperfections or fabrication flaws, such as spot weld imperfections, were detected that could have contributed to the failure.

Die Haartransplantationstechniken haben sich in den letzten Jahren rasant weiterentwickelt. Durch ein neues Entnahmeverfahren fur Follikular Units, die FUE(Follikular-Unit-Exzision)-Technik, ist die Haartransplantation fur eine Vielzahl von Patienten und Arzten interessant geworden. Der Anteil der etablierten Streifenentnahme mit mikroskopischer Follikelpraparation ging in den letzten Jahren zugunsten der FUE-Technik deutlich zuruck. Derzeit werden weltweit etwa 70 % aller Haartransplantationen in FUE-Technik, etwa 30 % mit Streifenentnahme durchgefuhrt. Bei der FUE-Technik wird die zu transplantierende Einheit direkt einzeln aus dem Haarkranz entnommen, eine aufwendige mikroskopische Praparation entfallt. Die gewonnenen Follikular Units sind sofort bereit fur die Transplantation. Das ist schonend fur den Patienten und spart in mikroskopischer Praparation speziell ausgebildetes Personal. Die Resultate beider Techniken sind absolut vergleichbar und asthetisch beeindruckend. Dank neuer technischer Innovationen beim Equipment konnen die Dissektions- und Transsektionsrate fur Haarwurzeln beim Entnahmeprozess gering gehalten werden. Auch aus diesem Grund ist es wichtig, dass die FUE-Technik nur approbierte und speziell dafur ausgebildete Arzte anwenden.

Severe scaling caused the guiding pin of two control valves of a smaller industrial steam turbine to seize which thus led to a malfunction. The customer sought clarification on whether the oxidation products are really common scale. This could be confirmed.

The up-scaling of the pyrolysis technologies is the next step to achieve the industrial scale and to fulfill the energy and petrochemical demand in large-scale units. The overall goal of this study...

A first-stage turbine vane was received in the laboratory directly from fabrication, prior to its use in engine service. The part had not yet been covered with its customary coating system that protects these parts against hot corrosion. A first visual inspection revealed multiple cracks on the airfoil’s hot gas path side, fairly centered in the part. After cutting the part open, it soon became apparent that the cracking was even more severe inside, suggesting crack initiation from that cooled side. Fractography allowed to determine liquation cracking as the metallurgical failure mechanism. Since the part was received immediately after pre-heat before plasma coating, that process step was concluded to have caused the cracking.

Strictly speaking, this contribution is not about a case study in failure analysis. However, the investigation described herein was inspired by a failure case. A heavyduty gas turbine engine used in a power and desalination plant in the Middle East experienced creep damage and cracking in some of its row 4 turbine blades after only some 15,000 operating hours. Microstructural alterations detrimental to the creep strength of the alloy were determined to be the metallurgical root cause of the failure. It was believed that said microstructural alterations were brought about by unusual transient operating conditions in engine service. Heat treatment tests were ordered to verify or disprove this hypothesis. It was established that the peculiar gamma prime morphology found in the failed blades can be produced by very high solutioning temperatures and subsequent rapid cooling. Such conditions in engine service are conceivable if sufficient unburnt fuel enters the turbine and ignites downstream of the combustion chamber (high temperature), and if water used in fuel line purging is injected into the turbine section immediately thereafter (rapid cooling). Solutioning above 1240 °C, followed by a water quench, produced said mono-modal fine γ' morphology.

Facultative scavenging by predatory carnivores is a prevalent but frequently underestimated feeding strategy. DNA-based methods for diet analysis, however, do not allow to distinguish between scavenging and predation, thus, the significance of scavenging on population dynamics and resource partitioning is widely unknown. Here, we present a methodological innovation to differentiate between scavenging and fresh prey consumption using prey RNA as a target molecule. We hypothesized that the rapid post-mortem breakdown of RNA in prey tissue should lead to a significantly lower detection probability of prey RNA than DNA when carrion rather than fresh prey is consumed. To test this hypothesis, ground beetles (Pseudoophonus rufipes [De Geer]) were offered either fresh or 1-day-old dead Drosophila melanogaster fruit flies (carrion). The detectability of prey RNA and DNA in the beetles' regurgitates was assessed with diagnostic Drosophila-specific RT-PCR and PCR assays at 0, 6, 12, 24 and 48 h post-feeding. After fresh fly consumption, prey RNA and DNA were detectable equally well at all times. When carrion prey was consumed, the detection strength of prey RNA immediately after feeding was significantly lower than that of prey DNA and reached zero in most samples within 6 h of digestion. Our findings provide evidence that prey RNA allows distinguishing between the consumption of fresh and scavenged prey, thereby overcoming a long-known weakness of molecular diet analysis. The assessment of prey RNA offers a generally applicable approach for examining the importance of scavenging in food webs to unravel its functional consequences for populations, communities, and ecosystems.

Helical tension springs used in switch mechanisms of medium voltage switches failed prematurely in test rigs. The switch mechanism assemblies did not reach the required number of cycles to failure. The springs failed by low cycle fatigue fracture. They were phosphate coated for corrosion protection but not shot peened. The material used for the springs is a usual patented spring steel. Chemical composition, mechanical properties, and microstructure of the failed springs and a reference spring alike were all unremarkable. The subject springs were assembled and rig tested at three different locations but failed only at two of them, not in the third. It was concluded that misalignment from assembly was the root cause of failure.

Chronische Schmerz- und Funktionserkrankungen sind haufig multifaktoriell bedingt. Um Chronifizierungsprozesse zu reduzieren und ein gutes funktionelles Ergebnis zu erreichen, sind fruhzeitig abgestimmte interdisziplinare Versorgungskonzepte sinnvoll. In unserem Team hat sich das Konzept „Befundeinordnung im 4‑Ebenen-Modell“ etabliert. Um im Versorgungsalltag verschiedene Faktoren fruhzeitig zu screenen, eignen sich die aus der Nationalen VersorgungsLeitlinie zum nichtspezifischen Kreuzschmerz bekannten („yellow/blue/black) flags“. „Flags“ sind in vielen Fachgebieten ein etabliertes Instrument; sie werden fur eine abgestimmte Kommunikation uber sektorale Schnittstellen genutzt. Im beruflichen Umfeld sind „soft skills“ wesentlich, deshalb wurden die „blue/black flags“ durch das Mini-ICF-APP erganzt. Fur den noch „weisen Fleck“ von Funktionsstorungen wurde im Rahmen uberregionaler interdisziplinarer Arbeitsgesprache eine Arbeitsversion von „white flags“ als Screeninginstrument entwickelt.

Zusammenfassung Hintergrund Großschadenslagen stellen den Rettungsdienst vor die Herausforderung, vielen Patienten mit begrenzten Ressourcen das Überleben zu sichern. Um hier eine Fehlverteilung von Ressourcen zu verhindern, ist eine genaue Vorsichtung essenziell. Aktuelle Studien zeigen, dass bei den verwendeten Vorsichtungsalgorithmen weiterhin Verbesserungsbedarf besteht. Ziel der Arbeit In dieser Arbeit untersuchten wir, welchen Einfluss eine veränderte Reihenfolge der Abfragen/Items auf die Qualität der Vorsichtungsalgorithmen hat. Material und Methoden Wir verwendeten eine Datenbank von 492 Luftrettungseinsätzen. Allen Patienten wurde durch eine Gruppe von Notärzten eine Referenzsichtungskategorie (SK) vergeben. Die Vorsichtungsalgorithmen mSTaRT, ASAV und PRIOR wurden in Excel-Befehle übersetzt und die SK für jeden Patienten berechnet. Anschließend rotierte die Reihenfolge der Items. Die berechneten SK wurden hinsichtlich Sensitivität, Spezifität, Unter‑/Übertriage und Youden-Index für die SK I (rot) ausgewertet. Ergebnisse mSTaRT zeigte keinerlei Veränderung der Qualität. Die Originalvariante von ASAV erreichte die beste Performance. Eine Rotation der Items führte zu einer Zunahme der Übertriage um 15 % bei sinkender Qualität. PRIOR profitierte am meisten von den Rotationen, wobei insbesondere die Variante mit einer initialen Abfrage der Gehfähigkeit zu einer Abnahme der Übertriage von 22 % führte. Dies führte zur stärksten Verbesserung des Youden-Index (+0,12). Diskussion Wir konnten demonstrieren, dass eine Rotation der Items innerhalb der Vorsichtungsalgorithmen ASAV und PRIOR einen Einfluss auf Über- und Untertriage hat. Insbesondere die Position der Abfrage der Gehfähigkeit hat einen bedeutenden Einfluss auf die Spezifität der Algorithmen.

Fractured wire ropes of a pantograph actuator system for electrical trucks were received from the client. They failed by low cycle fatigue (LCF) fracture during service in a customized test rig. The client reported wide scatter of the number of testing cycles to failure. A laboratory order was placed for a metallurgical failure analysis of the subject stranded ropes, this to derive recommendations for design improvements, so that the minimum number of cycles to failure could be increased, and the scatter decreased.

Even very simple cases of component failure can represent an enrichment for this section Failure Analysis. Besides the instructive value of an easily understandable content, they allow those failure analysts becoming acquainted with the field to gradually get to know the most important material-related mechanisms governing component failure cases. A look back by the authors on the section Failure Analysis of Practical Metallography cases revealed only one single erosion failure case in the past 10 years. It won't therefore do any harm to address this interesting failure mechanism once again. The erosion failure of a fan impeller presented in this article was very easily solved However, it was rather unexpected. Who would have considered it possible that an air extraction system in a factory workshop is subject to such high erosive distress? Hence, the main message of this short article is that the experts tasked with investigating the component failures should be very thorough and propose all sorts of damage hypotheses, sometimes even those which, at first glance, appear unlikely, and may only reject them when the examination results indicate the contrary.

Following the regional outbreak in China, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread all over the world, presenting the healthcare systems with huge challenges worldwide. In Germany the coronavirus diseases 2019 (COVID-19) pandemic has resulted in a slowly growing demand for health care with a sudden occurrence of regional hotspots. This leads to an unpredictable situation for many hospitals, leaving the question of how many bed resources are needed to cope with the surge of COVID-19 patients.In this study we created a simulation-based prognostic tool that provides the management of the University Hospital of Augsburg and the civil protection services with the necessary information to plan and guide the disaster response to the ongoing pandemic. Especially the number of beds needed on isolation wards and intensive care units (ICU) are the biggest concerns. The focus should lie not only on the confirmed cases as the patients with suspected COVID-19 are in need of the same resources.For the input we used the latest information provided by governmental institutions about the spreading of the disease, with a special focus on the growth rate of the cumulative number of cases. Due to the dynamics of the current situation, these data can be highly variable. To minimize the influence of this variance, we designed distribution functions for the parameters growth rate, length of stay in hospital and the proportion of infected people who need to be hospitalized in our area of responsibility. Using this input, we started a Monte Carlo simulation with 10,000 runs to predict the range of the number of hospital beds needed within the coming days and compared it with the available resources.Since 2 February 2020 a total of 306 patients were treated with suspected or confirmed COVID-19 at this university hospital. Of these 84 needed treatment on the ICU. With the help of several simulation-based forecasts, the required ICU and normal bed capacity at Augsburg University Hospital and the Augsburg ambulance service in the period from 28 March 2020 to 8 June 2020 could be predicted with a high degree of reliability. Simulations that were run before the impact of the restrictions in daily life showed that we would have run out of ICU bed capacity within approximately 1 month.Our simulation-based prognosis of the health care capacities needed helps the management of the hospital and the civil protection service to make reasonable decisions and adapt the disaster response to the realistic needs. At the same time the forecasts create the possibility to plan the strategic response days and weeks in advance. The tool presented in this study is, as far as we know, the only one accounting not only for confirmed COVID-19 cases but also for suspected COVID-19 patients. Additionally, the few input parameters used are easy to access and can be easily adapted to other healthcare systems.HINTERGRUND: Die COVID-19-Pandemie zeichnet sich durch einen sich langsam aufbauenden Bedarf von Ressourcen des Gesundheitswesens mit lokalen Hotspots aus und erzeugt dadurch enorme Probleme. Für die Krankenhäuser liegt eine der größten Herausforderungen in der Vorhaltung von Bettenkapazitäten, insbesondere da der Bedarf schwer vorherzusehen ist.Um den Entscheidungsträgern eine Hilfestellung zu geben, wurden mehrere simulationsbasierte Prognosen für die benötigte Bettenkapazität am Universitätsklinikum Augsburg durchgeführt, um bei variablen Pandemieverläufen die benötigten Bettenkapazitäten abschätzen zu können.Als Input dienen aktuelle Erkenntnisse über den Verlauf der Ausbreitung, insbesondere die Wachstumsrate an kumulierten Neuinfektionen pro Tag. Zur Abbildung von Unsicherheit werden mittels Verteilungsfunktionen, basierend auf Realdaten der Wachstumsrate, die Verweildauer sowie der Anteil der hospitalisierten COVID-19-Patienten im Einzugsgebiet modelliert. Im Anschluss erfolgt eine Monte-Carlo-Simulation, die eine Abschätzung der benötigten Bettenkapazitäten für mehrere Tage in der Zukunft erlaubt.Mithilfe von mehreren simulationsbasierten Kapazitätsprognosen im Zeitraum vom 28.03.2020 bis zum 08.06.2020 konnte die benötigte Intensiv- und Normalbettenkapazität am Universitätsklinikum Augsburg sowie im Rettungsdienstbereich Augsburg mit einer hohen Zuverlässigkeit prognostiziert werden.Mithilfe des entwickelten Simulationsmodells zur Abschätzung der benötigten Bettenkapazität kann den Kliniken und dem Katastrophenschutz eine Hilfestellung zur Abschätzung der kurzfristigen Entwicklung des Kapazitätsbedarfs für Verdachtsfälle sowie bestätigte COVID-19-Patienten gegeben werden. Der operative Einsatz der Methode am Universitätsklinikum Augsburg zeigte verlässliche Ergebnisse.

This short article presents a simple case of failure, from a materials engineering point of view. One may therefore ask what makes it worth publishing. The inclined reader, though, will notice the somewhat surprising nature of the macroscopic damage pattern. The type of defect reported in the context of the first examination of the component, which had to be performed non-destructively, was therefore wrong. This is an example of the risk of misinterpretation in cases where the customer dictates how the examination is carried out that all those working in the field of damage analysis are aware of. It also demonstrates that using the scanning electron microscope is not a luxury, not even in the manufacturing control, as some damage patterns cannot be elucidated without using this device that has revolutionized the component failure analysis.

Impingement cooling plates welded to the inner shrouds of first-stage turbine vanes were found cracked after refurbishment, before installation in a heavy-duty gas turbine engine. The metallurgical root cause of the failure was determined to be embrittlement and surface melting from thermal over-exposure. This was not brought about by engine service, but was a result of the complex repair process, part of which are several heat treatment operations. The latter are tailor-made for the base alloy of the turbine vanes. For the lower-grade impingement cooling plates, however, the peak temperature from these furnace runs was too high. They should have been removed from the vanes prior to the high-temperature heat treatment operations, but were left attached to the vanes for cost reasons.

Swivel arms in a turning gear application failed in service due to fatigue cracking. 2 out of 52 components were affected. Turning gears are mainly used to spin heavy-duty gas turbine engines rotors after shut-down to prevent distortion of the still-hot rotor. The design of the swivel arms, that was not robust enough to tolerate deviations in fabrication, was identified as the root cause of the failures.

With a novel class of heavy-duty gas turbine engines, turbine exhaust temperatures are expected to further increase. There are concerns that the propensity to cracking in service of the welded turbine exhaust casing (TEC) liners might also increase. Cold-formed “collars”, featuring large stress-reducing fillet radii, were designed to decrease thermal stresses in the welds, where the struts of the turbine bearing casing are aerodynamically clad by liner plates. Such collars were received from a supplier in the course of a product and process qualification (PPQ). The results of the metallurgical investigation ordered by an internal client are the subject of this contribution. It was found that deformation martensite was present in the subject cold-formed fillet pieces, despite a pre-heat of 150 °C and a post-fabrication 920 °C annealing process. However, the amount of deformation martensite found, at below 5 % volume fraction, was considered not to be detrimental for engine operation.

One ring of a gland seal from a gas compressor was found fractured. The failure was detected because water leaked into the leaking gas system. The supplier apparently never had issues with this assembly. The field record is unremarkable, according to the manufacturer. However, the incident natural gas compressor is used in intermittent service only, while the assembly was originally designed for more or less permanent operation, according to the supplier of the compressor. It is hypothesized that hydrogen embrittlement initiated surface cracks in the subject ring, at the fastening hole, where wall thickness is minimal, and eventually caused delayed fracture due to the hoop stresses from shrink fitting of the gland seal ring. This was assisted by a hard and relatively brittle (quenched and tempered) microstructure, with manganese sulfide stringers and grain boundary carbide precipitates as contributing factors. All this eventually lead to brittle overload failure of the subject ring by predominantly transgranular lamellar tearing along MnS stringers, where the hoop stress caused decohesion at the interface between MnS inclusions and the matrix. This fracture morphology is typical of lamellar tearing (Terassenbruch). Actually, a mixed mode fracture morphology was observed. Interspersed in the predominantly transgranular overload fracture were areas of intergranular fracture along grain boundaries, embrittled by secondary carbide precipitates, a common condition in quenched and tempered hard martensitic stainless steels. No evidence of cyclic crack propagation, i. e. fatigue fracture, was found. Dimensions were not checked by the investigating laboratory. The hypothesis of dimensional deviations as a contributing factor to the fracture of the ring can therefore not be proven or ruled out within the scope of this investigation, and is mentioned here just for the sake of completeness and as a recommendation to the supplier of the assembly and to the manufacturer of the gland seal to look into this matter more closely. Finally, the strength of the steel, exceeding specified values, will likely have exacerbated the sensitivity of the microstructure to brittle overload failure by predominantly transgranular lamellar tearing, and partly intergranular cleavage. It also increased the propensity of the steel to failure by hydrogen embrittlement. From a design point of view, the combination of a sensitive microstructure due to MnS stringers, combined with too high a strength level, and the shrink-fitting of the gland seal assembly, is not well suited for this application, particularly if and when corrosion can produce hydrogen and embrittle the material further. It is strongly recommended to avoid in future strength levels exceeding the specification and what is usual for such applications, by sufficiently high tempering temperatures and times at temperature, and to avoid dimensional deviations that might increase hoop stresses in this interference fit. Still better would be to eliminate the shrink fit from this design altogether. It is understood by the authors that, in the meantime, the gland seal was re-designed and no shrink fit of the gland seal rings is needed any more.

A novel tip of a fuel gasification burner, designed-to-SLM (Selective Laser Melting) and made by SLM, was introduced by the client. This component failed prematurely by cracking at the cooled tip. The metallurgical cause of the failure was overheating due to blocked cooling passages, probably as a result of contaminated cooling water, leading to corrosion in the non-stainless piping systems upstream of the burner. Corrosion products, mainly iron oxides, spalled off said non-stainless components, causing blockages in the intricate cooling cavities of the AM-built burner tip. This lead to excessive thermal overload, reaching the melting temperature of the alloy at the burner tip. As a result, the subject burner tip failed by TMF cracking. Neither manufacturing nor design flaws were identified in the course of this failure investigation. It is speculated that the subject component will perform well if cooled properly. The root cause of the failure is the operation of the cooling water system of the subject burner that allowed loose corrosion products to form and to enter the burner tip.