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Item type:Publication, Access status: with files , Merging nano and macro structure design: opportunities for the structural integrity of steel infrastructure(Elsevier, 2025-12-10); ; ; ; Merging the macro-level design with the nano-level design in structural engineering, hence, using the superior properties of nanostructured metallic multilayers for protecting fatigue-critical joints of the macrostructure and ensuring the structural integrity of the steel infrastructure are the objectves of a research effort at TU Hamburg. Nanostructured metallic multilayers (NMM) have significantly higher strength, fatigue resistance and ductility than monolithic homogeneous metal cross sections. The superior structural properties of these nanostructured cross sections are known, and so it is surprising why no attempt has been made to date to use nanostructured cross sections in macro cross sections in structural engineering to improve the cross section properties. This paper links the advantages of nanostructured multilayers with the needs of homogeneous metallic macro-cross sections and examines the question to which extent the high-performance material nanolaminate can compensate for the structural weak parts of metallic infrastructure. The welded joint subjected to fatigue is addressed as vulnerable part of metallic infrastructure. The article provides insights on how nanostructured multilayer can potentially contribute to the future of steel construction, further, how nanostructured multilayer can potentially affect fatigue design. The design as well as the maintenance of cyclically loaded metallic infrastructures, such as bridges and offshore wind turbines, are discussed herein and it is shown how sustainability, resource conservation, reduction of CO2 footprint, readiness, security of supply and economic viability of steel infrastructure can potentially be achieved.Publicationtype: Journal Article17 10 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Significant improvement of the fatigue performance of ER70S-6 WAAM un-milled structures: a Cu/Ni multilayer nanotechnology approach(Elsevier, 2025-12-10); ; ; ; In recent years, the adoption of Wire Arc Additive Manufacturing (WAAM), now defined as Directed Energy Deposition based on Gas Metal Arc Welding (DED-Arc), in steel construction has increased significantly. However, the sequential layer deposition inevitably creates surface notches that cause high stress concentrations, leading to fatigue crack initiation. The current industrial standard for post-processing, CNC milling, is time-consuming and resource-intensive. A novel research approach focuses on directly controlling critical residual stresses of as-built specimens by introducing near-surface compressive residual stresses using a Cu/Ni nanostructured metallic multilayer (NMM). This study investigates the effect of NMM on DED-Arc structures and extends its application to metallic 3D-printed components. Optical microscopy provides detailed surface morphology and reliable roughness measurements, while X-ray diffraction (XRD) confirms the presence of residual tensile stresses in the NMM and the resulting residual compressive stresses in the steel substrate. Preliminary tension-tension fatigue testing provides insights into the fatigue strength increase due to NMM treatment of DED-Arc dogbone specimen.Publicationtype: Journal Article39 19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Material mechanisms of the nanostructured metallic multilayer post-weld treatment for fatigue strength increase(Elsevier, 2025-12-10); ; ; ; While traditional post weld treatments intend to reduce the fatigue failure potential by changing the weld seam geometry, introduction of compressive residual stresses and shielding off environmental impacts, the novel nanostructured metallic multilayer (NMM) post-weld treatment covers all three mechanisms simultaneously. NMM offer combined high strength and ductility and a significantly enhanced fatigue resistance. In a recent study a strong enhancement in fatigue resistance was detected. Utilizing energy-dispersive X-Ray diffraction techniques at the P61A-beamline at the German Synchrotron (DESY), it was found that residual stresses generated during the deposition process play a crucial role in this enhancement. Specifically, tensile stresses within the nanolaminate induce beneficial compressive stresses in the underlying substrate, effectively inhibiting fatigue crack initiation and resulting in an unprecedented increase in fatigue strength. NMM treatment of the double-V weld increases the fatigue strength from FAT class 80 to 225. This paper investigates which process parameters optimize the compressive stress profile in the steel base material, paving the way for the NMM post-weld treatment to reliably and economically contribute to longevity of cyclically loaded metal infrastructure.Publicationtype: Journal Article20 14 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Enhancing the lifespan of steel structures through a 3D-printed coating device for the application of a nanometallic multilayer on weld seams(Elsevier, 2025-12-10); ; ; ; Given the substantial environmental and economic consequences associated with deteriorating infrastructure, prolonging the service life of steel bridges is essential for advancing sustainability and economic viability. A critical factor in achieving this goal is enhancing the integrity of welded joints, which play a pivotal role in the bridge’s performance under dynamic loading conditions. Research indicates that the fatigue strength of welds can be increased by up to sixfold through the application of a nanometallic multilayer (NMM) composed of nickel and copper. To date, investigations into the fatigue enhancement of welded joints using NMM have predominantly been conducted on a laboratory scale. To enable practical application on existing infrastructure, a coating device is being developed to apply the NMM treatment directly onto surfaces without the need for full immersion in an electrolyte bath, thus supporting its implementation as a post-treatment process for steel bridges.Publicationtype: Journal Article11 27 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Separation and quantification of damage-induced and non-damage-induced vibro-acoustic modulation and the problem of contrary modulationsVibro-acoustic modulation (VAM) has been exploited over the last three decades to assess and monitor the integrity of structures. One major challenge is the separation of damage-induced and non-damage-induced modulation in the measured system response for reliable structural health monitoring (SHM). Most scientific works on VAM imply that the initiation and growth of structural damage is expected to cause modulation that adds up with non-damage-induced modulation increasing the total amount of modulation. This article unfolds why this assumption can be invalid for standard VAM applications: It is explained analytically why two nonlinearities working in opposite directions (one stiffening the structure under loading, one softening it) cause contrary modulations: The two nonlinear contributions can neutralize each other in the system response. Numerical simulations are then presented that investigate separately one damage-induced nonlinearity and two non-damage-induced nonlinearities in the same aluminum plate. The modulation caused by them individually is quantified and the subsequent comparison demonstrates the occurrence of contrary modulations in this representative VAM setup. It has to be concluded that damage-induced modulation does not necessarily increase the total modulation in the system response. This finding has potential to boost VAM-related research regarding its reliability and sensitivity.Publicationtype: Journal Article29 16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Verknüpfung von Nano mit Makro – Chancen für den StahlbauLinking nano with macro – opportunities for steel construction. Nanostructured metallic multilayers have significantly higher strength, fatigue resistance and ductility than monolithic homogeneous metal cross sections. The superior structural properties of these nanostructured cross sections are known, and so it is surprising why no attempt has been made to date to use nanostructured cross sections in macro cross sections in structural engineering to improve the cross section properties. This paper links the advantages of nanostructured multilayers with the needs of homogeneous metallic macro-cross sections and examines the question of the extent to which the high-performance material nanolaminate can compensate for the structural weak points of metallic infrastructure. The following weak points of metallic infrastructure are addressed: 1) the welded connection subjected to fatigue and corrosion, 2) additively printed metallic cross sections exposed to fatigue and corrosion. The article provides food for thought on how nanostructured multilayer can potentially contribute to the future of steel construction. As an example, the design and maintenance of cyclically loaded metallic infrastructure structures, such as bridges and offshore wind turbines, are discussed and it is shown how sustainability, resource conservation, reduction of the CO2 footprint, availability, security of supply and economic viability of steel infrastructure structures can potentially be achieved.Publicationtype: Journal Article16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Physical explanation for vibro-acoustic modulation due to local and global nonlinearities in a structure and its experimental and numerical validation(2022-06-23); ; This article introduces a simple physical explanation that demonstrates why a local or global nonlinearity in a structure causes amplitude modulation and phase modulation in the system response, when employing the vibro-acoustic modulation method for structural health monitoring (SHM) applications. The underlying major assumption and the explanation itself are validated experimentally and numerically. Afterwards, the explanation is used to demonstrate comprehensively why very different types of envelope functions can be observed in the system response, depending on the exciting ultrasonic carrier frequency ω. The beauty of the suggested explanation is that it does not only work for local nonlinearities, such as exhibited by defects, but also for any non-damage induced (local or global) nonlinearity in the system which can cause modulation as well. A physical understanding of cause and effect is of crucial importance here, because the modulation caused by non-damage induced nonlinearities might camouflage the effects of local damage that one is actually interested in during SHM applications.Publicationtype: Journal Article72 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , The total collapse of the Twin Towers: what it would have taken to prevent it once collapse was initiatedIt is generally taken as a given that there is no reasonable design concept that could have prevented the collapse of the Twin Towers, once it was initiated, from progressing all the way down to the ground. This view is rooted in the idea that the force generated during the inevitable impact between what may be called the intact upper section (IUS) and the intact lower section (ILS)—meaning the building sections above and below the initially lost columns, respectively—will exceed by at least one order of magnitude the capacity of the latter. On closer inspection, this turns out to be only partially correct—it is correct with regard to the topmost floor plate of the ILS but not with regard to the columns below this floor plate. This paper shows that if the ILS in the Twin Towers had been topped by a stronger-than-ordinary floor plate allowing the columns below to respond properly, rather than be bypassed, these columns—and with them the ILS—would likely have survived. The paper subsequently proposes a building design concept consisting in the insertion of strengthened floor plates in intervals of 10–20 stories.Publicationtype: Journal ArticleScopus© Citations 4 130 1925 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , 828 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Towards structural health monitoring using vibro-acoustic modulation in the real worldIn this paper we explore the opportunities and challenges of deploying a Wireless Sensor Network to monitor the structural health of civil infrastructure using Vibro-Acoustic Modulation. The fundamentals of the method are explained and the challenges for a sensor network in a practical implementation are investigated. Ideas and requirements for the sensor nodes are analyzed and presented.Publicationtype: Conference Paper925 144