M. Oechsner

• Technical University of Darmstadt

Die Einschraubtiefe und die Größe des Vorlochdurchmessers bestimmen neben dem Scherfestigkeitsverhältnis der eingesetzten Werkstoffe die quasi‐statische Beanspruchbarkeit von Schraubenverbindungen mit gefurchtem Gewinde. Zur Validierung eines neuen Bewertungsansatzes zur Bestimmung der erforderlichen Mindesteinschraubtiefe werden Auszugsversuche mi...

This study investigates the influence of build orientation on the high-temperature mechanical properties of IN738LC manufactured via metal laser powder bed fusion (PBF-LB/M). Since the PBF-LB/M layer-wise manufacturing process significantly affects grain morphology and orientation—ranging from equiaxed to textured grains—mechanical properties typic...

The ability to assess the risk of corrosion of metallic structures in particular environments holds considerable significance in the field of automotive industry. In recent years, machine learning has evolved into a crucial tool to evaluate the complex and multidimensional corrosion phenomena. In this paper, the special case of non‐aqueous alcohola...

PBF-LB/M (Metal Laser Powder Bed Fusion) is a commonly used additive manufacturing process for gas turbine parts. This manufacturing method allows for small quantity batches with complex part designs. The mechanical behavior of PBF-LB/M components is strongly influenced by manufacturing process parameters, such as component geometry, build orientat...

Zum Schutz vor mechanischen und korrosiven Einflüssen werden Radsatzwellen heute üblicherweise lackiert. Beschädigungen im Betrieb erfordern jedoch enge Inspektionsintervalle zur Überprüfung zulässiger mechanischer und korrosiver Schädigungstiefen. Die Untersuchung einer möglichen Steigerung der Korrosionsschwingfestigkeit durch induktive Randschic...

We quantify the uncertainty of the L\"ammer model of damage evolution when fitted to (noisy) observations of damage evolution in cyclic fatigue experiments with and without dwell time. We therefore develop a bootstrap method by sampling over blocks of load cycles in the experiments in order to quantify the uncertainty in the material parameters of...

A mechanical test strategy is designed to determine the resistance of protective intermetallic aluminum layers on molybdenum substrates. Performing mechanical experiments, such as compression, four‐point bending and indentation tests, the specific failure behavior and a potential impact of observed phase transformations within the interface zone on...

High-strength HV-fastener sets of dimensions M48 and M64 with property class 10.9 were employed in offshore wind turbine frameworks. The M64 were used in coupling flanges within monopiles. The M48 were employed in another offshore wind farm and encountered natural weathering. In both installations, time-delayed fractures of the nuts were observed....

Aluminum alloys are widely used in automotive construction, and since the introduction of biogenic ethanol into fuels, the issue of nonaqueous alcoholate corrosion has become an important topic. In this paper, the kinetics of AA1050 temperature‐induced alcoholate pitting corrosion are examined experimentally with a specially constructed microreacto...

Metal Laser Powder Bed Fusion (PBF-LB/M) allows for high degrees of design freedom and the manufacture of high temperature Ni-based materials, such as IN738LC. The PBF-LB/M microstructure is dependent on several factors, including process parameters, component geometry, build orientation and post-processing steps (e.g. heat treatment). The correlat...

In fuel‐bearing components, particularly in automotive applications operating at elevated temperatures, the durability of light metals is significantly influenced by their susceptibility to alkoxide corrosion. Alkoxide corrosion is characterized by its spontaneous nature and exceptionally rapid degradation of materials once initiated. This study pr...

To determine the threshold behavior of Inconel 718 Single Edge Notched (SEN) specimen are pre-cracked in a compression pre-cracking procedure. At a load ratio of Rσ = 100 cracks are generated which remain unaffected by plastic deformation in the vicinity of their crack tip. In the described investigations the effective crack tip loading conditions,...

Der Schwellenwert gegen Ermüdungsrissausbreitung ∆Kth dient zur Bewertung der Wachstumsfähigkeit langer Risse unter zyklischer Beanspruchung. Aufgrund der nur sehr kleinen zyklischen Lasten und damit verbundenen kleinen Rissöffnungsweiten zeigen Rissschließeffekte einen besonders stark ausgeprägten Einfluss auf das Rissfortschrittsverhalten im Schw...

Pressure equipment poses a high risk of harming people and the environment in case of failure. They are, therefore, highly regulated by the Pressure Equipment Directive. To enable laser powder bed fusion of metals (PBF-LB/M) for the manufacturing of such components, component appearance and quality need to be characterized and qualified for each sp...

Metal Laser Powder Bed Fusion (PBF-LB/M) allows for high degrees of design freedom and the manufacture of high temperature Ni-based materials, such as IN738LC. The PBF-LB/M microstructure is dependent on several factors, including process parameters, component geometry, build orientation and post-processing steps (e.g. heat treatment). The correlat...

Components manufactured with Metal Laser Powder Bed Fusion (PBF-LB/M) are built in a layerwise fashion. The PBF-LB/M build orientation affects grain morphology and orientation. Depending on the build orientation, microstructures from equiaxed to textured grains can develop. In the case of a textured microstructure, a clear anisotropy of the mechani...

In present work, the monotonic and cyclic properties of a novel Al‐Mg‐Zn‐Cu‐Si compositionally complex alloy (CCA) are investigated. Microstructural studies reveal that a eutectic phase and fishbone‐type structures are embedded in the Al‐matrix. The mechanical properties of this CCA obtained under compressive loading are found to be promising. Howe...

The desire to apply annealed float glass with its economic and optical advantages in comparison to tempered glass is limited in part by the reduced edge strength. In the design standard for glass DIN 18008 the edge strength amounts only 80 % of the surface strength. Due to temperature stresses, the edge strength of annealed float glass is a decisiv...

In this paper the effect of an accelerated creep strain rate under thermal cycling conditions is introduced. The effect occurs in the industrial furnace sector, where thin walled structures are exposed to very high temperatures up to 80% of the melting temperature and low mechanical loadings which represent the dead weight of the components. The ef...

Die ultraschallbasierte Vorspannkraftermittlung an Schrauben wird derzeit überwiegend mit der Ein-Moden-Methode realisiert. Diese Methode basiert auf der Laufzeitmessung von Longitudinalwellen. Hierbei ist für jede Schraube eine Referenzmessung im nicht verspannten Zustand notwendig. In der vorliegenden Publikation wird die Ein-Moden-Methode um ein...

Feuerverzinkte Stahlbauten haben sich im Hochbau etabliert und gehören zum Stand der Technik. Sie erreichen Korrosionsschutzdauern in der Größenordnung der Lebensdauer des Bauwerks (100 Jahre). Die Anwendung dieses Korrosionsschutzsystems hätte auch im Brückenbau ein großes Potenzial. Wirtschaftlichkeit und Nachhaltigkeit im Brückenbau sind neben d...

Precise determination of the remaining service life of technical components requires sufficient knowledge of fatigue crack growth behaviour and the growth rate of defects. Cracks in real components often experience multiaxial far field stresses due to their complex geometry and composite loadings acting on it. Digital image correlation (DIC) is wel...

Friction stir welding enables joining of high‐strength, lightweight aluminum alloys, e.g., EN‐AW‐7075, below the melting point by induced plastic deformation. Therefore, heat transfer into the adjacent regions beneath the weld seam is significantly reduced as compared to fusion welding processes such as laser beam welding. However, specific zones a...

Der Beitrag stellt die Ermittlung der lokalen zyklischen Beanspruchung an einer Rissspitze vor, welche auf der Berechnung des J-Integrals als Intensitätsparameter basiert. Anhand von Rissfortschrittssimulationen mittels Finite Elemente Methode unter Berücksichtigung von plastizitätsinduziertem Rissschließen wird das Vorgehen für ein ausgewähltes Be...

Bedingt durch die kleinen Lastschwingweiten und damit verbundenen kleinen Rissöffnungsweiten haben Rissschließeffekte einen teils ausgeprägten Einfluss auf den Schwellenwert gegen Ermüdungsrissausbreitung. Sie führen zu einem vorzeitigen Kontakt der Rissflanken und damit einer Reduktion der zum Rissfortschritt beitragenden Lastschwingweite. Damit e...

The effects of solution heat treatment parameters and quench media as a processing tool for tailoring microstructure, mechanical and corrosion properties in roll forming of EN AW 7075 alloy were studied. The highest yield stress and ultimate tensile strength were obtained for the specimens quenched in water, while the air-cooled specimens exhibited...

Cover Picture: (Materialwiss. Werkstofftech. 12/2022)

https://www.schweissenundschneiden.de/artikel/vorspannkraft-monitoring-mittels-ultraschallmethoden-ohne-referenzmessung-verlaessliche-vorspannkraftermittlung-fuer-verbaute-schraubenverbindungen Ultraschallsysteme werden seit über fünfzehn Jahren zur Bestimmung der Vorspannkraft in Schrauben bei der Montage genutzt. Die kommerziell verfügbaren indu...

With the onset of VHCF research, material behavior inconsistent with conventional versions of the Miner rule started occurring repeatedly: instead of decreasing the residual lifetime of a specimen, load cycles just below the so-called endurance limit increase lifetime compared to CA tests even if only the cycles of the highest load step are counted...

Rising demands on material performance at high temperature in components under complex loading such as steam- and gas turbine housings require an increase in versatility and precision of component life modelling approaches. However, the database to calibrate those models is commonly derived from uniaxial testing. The impact of multiaxial loading, b...

This study focuses on the influence of microstructure and ductility on the short crack behavior and the FCG threshold. For this, an additively manufactured batch of the nickel-based alloy IN718, made via Laser Powder Bed Fusion (LPBF) process, is compared to both conventionally wrought and cast IN718 material. An initial characterization revealed s...

The majority of lifetime models associates the failure of thermal barrier coatings to an oxidation of the bond coat. A thickening of the thermally grown oxide leads to a conversion of stresses at the undulated ceramic-metal interface, supporting the propagation of existing micro cracks. However, in plasma-sprayed multilayer thermal barrier coatings...

Turbinenscheiben sind thermisch und mechanisch hochbeanspruchte, sicherheitsrelevante Komponenten in Gasturbinen. Ihre Integrität wird in Bauteiltests unter Überdrehzahlbedingungen nachgewiesen. Kontext des Aufsatzes ist die Erarbeitung einer zusätzlichen Bewertungsebene auf der Grundlage von Versuchen unter monotoner Beanspruchung, die die Beanspr...

Die Atmosphäre hat einen teils ausgeprägten Einfluss auf das Rissfortschrittsverhalten kohlenstoffarmer Stähle. So kann die Luftfeuchte das Risswachstum durch korrosionsbedingte Metallauflösung im Vergleich zu in inerter Umgebung durchgeführten Risswachstumsversuchen beschleunigen – Korrosionsprodukte, konkret zwischen den Rissflanken eingeschlosse...

Rising demands on material performance at high temperature in components under complex loading such as steam- and gas turbine housings require an increase in versatility and precision of component life modelling approaches. However, the database to calibrate those models is commonly derived from uniaxial testing. The impact of multiaxial loading, b...

This study focuses on the influence of microstructure and ductility on the short crack behavior and the fatigue crack growth threshold. An additively manufactured batch of the nickel-based alloy IN718, made via Laser Powder Bed Fusion (LPBF) process, is compared to both conventionally wrought and cast IN718 material. Initial characterization reveal...

barrier coatings to an oxidation of the bond coat. A thickening of the thermally grown oxide leads to a conversion of stresses at the undulated ceramic-metal interface, supporting the propagation of existing micro cracks. However, in plasma-sprayed multilayer thermal barrier coatings consisting of gadolinium zirconate (GZO) and yttria-stabilized zi...

Applying damage-tolerant design approaches requires a comprehensive understanding and reliable modeling of crack growth under service conditions. This in turn requires gathering the necessary database for model parametrization and validation from the observation of crack growth in component-like test piece geometries at service-like thermo-mechanic...

Components made from coarse-grained alloys often exhibit crack initiation in the far field of notches or bore holes when subjected to static and cyclic loading at high temperature or under thermo-mechanical fatigue (TMF) conditions. It is often the combination of elevated stress and a weak spot in the microstructure that defines the site of crack i...

The impact of crack closure and environmental effects on the experimental determination of the fatigue crack propagation threshold is a major problem for the assessment of cyclically loaded components, especially at low stress ratios R. In this work, the influence of the experimental procedure and air humidity on da/dN−ΔK data at different R is dis...

The robust determination of the threshold against fatigue crack propagation ∆Kth is of paramount importance in fracture mechanics based fatigue assessment procedures. The standards ASTM E647 and ISO 12108 introduce operational definitions of ∆Kth based on the crack propagation rate da/dN and suggest linear fits of logarithmic ∆K– da/dN test data to...

The desire to apply annealed float glass with their economic and optical advantages is limited by the reduced edge strength due to the cutting process. The edge strength of annealed float glass is a decisive factor especially for insulating glazing due to temperature stress. In standards (e. g. DIN EN 18008), the edge strengths are reduced compared...

Experiments to describe the crack growth behavior are expensive and complex, while the evaluation depends mainly on the determined crack lengths over the testing period. Digital image correlation (DIC) is well established for crack-length and displacement measurements, but it normally requires sample preparation with speckle paint and interferes wi...

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Economic efficiency and sustainability in bridge construction are determined not only by the costs of new construction but also, in particular, by the maintenance costs incurred during the service life. A successfully completed research project has shown that hot-dip galvanizing can be used as a basic and advantageous corrosion protection over the...

Der Lebensdauernachweis von zyklisch beanspruchten Schraubendruckfedern kann mit Goodman-Diagrammen aus der DIN EN 13906-1 erfolgen. Eine Auslegung gemäß der FKM-Richtlinie „Rechnerischer Festigkeitsnachweis für Maschinenbauteile“ kann aufgrund zu hoher Zugfestigkeiten der Federstähle nicht erfolgen. In dem vorliegenden Beitrag wird der Berechnungs...

Rotary components in turbine machinery such as gas turbine blades and discs or turbocharger wheels need to be designed so that high cycle fatigue (HCF) loads are well below the fatigue endurance limit to ensure safe operation. This requires an accurate measurement of the fatigue endurance limit and the related intrinsic fatigue crack growth (FCG) t...

Ultraschallsysteme werden seit über fünfzehn Jahren zur Bestimmung der Vorspannkraft in Schrauben bei der Montage genutzt. Die kommerziell verfügbaren industriellen Systeme basieren auf Longitudinalwellen. Bei der Nutzung dieser Ein-Moden-Methode ist jedoch die Kenntnis der Referenzlaufzeit jeder Schraube im nicht verspannten Zustand und eine mater...

The growth of short cracks in round bar specimens with a circumferential notch has been investigated by an extensive experimental study. This specific specimen geometry has been applied to determine notch support based on a reduced crack growth rate due to the induced stress gradient compared to situations without a notch. At the same time, this in...

div class="section abstract"> A test sample configuration with a circular cross-section has been conceptualized to reproduce all geometrically relevant flow-guided elements - straight segments, deflections, bifurcations, impingement regions, confluence - as they can also be found in the cooling systems of realistic Internal Combustion (IC) engines....

The fatigue behavior of bolted joints is critical to failure for many applications due to the high notch effect. Among other parameters, the lifetime is based on the influence of the surface system, consisting of corrosion protection and lubricant. With the intention of considering the surface system in the design and dimensioning process of bolted...

In the European standards specifying disc spring manufacturing, geometry, shape and characteristic, an edge rounding is prescribed. Common methods for the calculation of disc spring characteristics, even in these standards, are based on a rectangular cross-section. This discrepancy can lead to a considerable divergence of the computed characteristi...

The investigation of crack growth in low cycle creep-fatigue conditions shows a significant influence of dwell times on crack closure. The observed cracks here are present in a round bar specimen with a circumferential notch. This component-like structure was originally chosen to determine notch support. Therefore, a fracture mechanical approach ba...

Die Feuerverzinkung gewährleistet für Stahl- und Stahlverbundbrücken den dauerhaftesten Korrosionsschutz von rund 100 Jahren und leistet damit einen wesentlichen Beitrag zur Nachhaltig- und Wirtschaftlichkeit. Die laufenden Kosten haben im Brückenbau neben den Neubaukosten im Lebenszyklus einen hohen Beitrag. Zur Nutzung des Potentials der Feue...

To make powder bed fusion (PBF) via laser beam (-LB) for metals (/M) available for highly regulated components such as pressure equipment according to the Pressure Equipment Directive, system-specific qualification methods need to be established to deal with process- and geometry-dependent inhomogeneous material behavior. Therefore, the material pr...

Rising demands on material performance at high temperature in components under complex loading such as gas turbine housings demand an increase in versatility and precision of component life modelling approaches. However, the database to train those models is commonly derived from uniaxial testing. The impact of multiaxial loading, both proportional...

Most of the components’ lifetime is consumed in the range of crack initiation and short crack growth. This paper shows the impact of notches in these early stages under creep-fatigue loading at high temperature. With the focus on round bar specimens having a circumferential notch the influence of different notch shapes, loading levels and condition...

Laser powder bed fusion (LPBF) has indisputable advantages when designing new components with complex geometries due to toolless manufacturing and the ability to manufacture components with undercuts. However, fatigue properties rely heavily on the surface condition. In this work, in-process surface parameters (three differing contour parameter set...

Components made of cast nickel alloys that are exposed to high temperature creep and creep-fatigue loadings can exhibit grain structures with average grain sizes of several millimetres in some areas. Investigations into the cracking behaviour of coarse-grained nickel casting alloys have revealed the occurrence of cracks away from stress concentrati...

Wasserstoff gilt als eine der Schlüsseltechnologien im Rahmen der gesellschaftspolitischen Anstrengungen für eine nachhaltige Energieversorgung und klimaneutrale Mobilität. Neben der elektrochemischen Umsetzung in der Brennstoffzelle, der Funktion als Primäredukt für synthetische Kraftstoffe aller Art oder auch der direkten Verbrennung in der Gastu...

Fracture deformation parameters, like fracture elongation, reduction of area and uniform elongation, are valid experimental properties to interpret a material’s ductility. Optimizing alloy compositions in order to assure a sufficient ductility even under high temperatures and long operational times is of crucial interest in order to keep modern hea...

Rising demands on material performance at high temperature in components under complex loading such as gas turbine housings demand an increase in versatility and precision of component life modelling approaches. However, the database to train those models is commonly derived from uniaxial testing. The impact of multiaxial loading, both proportional...

The significance of accelerated determination of creep properties is reflected by the amount of available research work, which comprises a variety of material types and application fields. As an outcome, several analytically based as well as experimentally based extrapolation methods have been developed or evolved. In contrast to experimental metho...

In diesem Beitrag stellen wir das am Zentrum für Konstruktionswerkstoffe (MPA-IfW) der TU Darmstadt entwickelte Verfahren zum Kalibrieren der Parameter Verformungsmodul, Federhöhe und wirksamer coulombscher Reibfaktor in rechnerischen Modellen von Tellerfedern anhand experimentell ermittelter Kennlinien vor. Wir definieren den Bauteilparameter Verf...

Cost efficiency and sustainability of construction measures are determined not only by the cost of the new building itself, but also by subsequent improvements and running costs. This also includes the cost of replacing bolts that were not installed in accordance with the requirements given in the decisive specifications. Here, the subsequent contr...

de In dieser Studie wird die Entwicklung verschiedener thermisch gespritzter Beschichtungen für den Einsatz im Armaturenbau diskutiert. Basierend auf etablierten Verschleißschutzschichten der Armaturenindustrie wurden verschiedene Festschmierstoffe in diese Beschichtungen integriert, um das Verschleiß- und Reibungsverhalten bei anwendungsnahen Bela...

Cold extruded components are characterized by residual stresses, which originate from the experienced manufacturing process. For industrial applications, reproducibility and homogeneity of the final components are key aspects for an optimized quality control. Although striving to obtain identical deformation and surface conditions, fluctuation in t...

Wirtschaftlichkeit und Nachhaltigkeit im Brückenbau sind neben den Neubaukosten insbesondere von den während der Lebensdauer anfallenden Unterhaltungskosten bestimmt. Das Forschungsvorhaben FOSTA P835 - Feuerverzinken im Stahl und Verbundbrückenbau – IGF-Nr. 351 ZBG zeigt, dass die Feuerverzinkung als Korrosionsschutz grundlegend und vorteilhaft ei...

For the generation of fatigue curves by means of fatigue tests, an ultimate number of cycles has to be defined. This ultimate number of cycles limits the permissible range of the S-N curve for the design of components. This introduces tremendous expenses for testing components that reach the VHCF regime. We conduct an artificial censoring experimen...

In fatigue tests on steels, results obtained in ultrasonic fatigue tests often deviate from results obtained in conventional fatigue tests. One reason for this deviation is the difference in control types of ultrasonic and conventional fatigue tests: ultrasonic fatigue tests are typically conducted under displacement-control, while conventional fat...