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Item type:Publication, Access status: with files , Increasing residual lifetime of steel structures through use of nanometallic multilayer treatmentSteel bridges are experiencing premature aging due to fatigue with structural connections particularly affected. According to the International Institute of Welding (IIW), welded connections deteriorate because of inherent geometric notches as well as material changes that occur during the welding and cooling process. Researchers at Hamburg University of Technology have developed a novel post-weld treatment known as nanometallic multilayer (NMM) treatment. This method applies a nanolaminate coating using electrodeposition, covering the entire connection area. Upon solidification, the NMM induces compressive residual stresses in the steel substrate adjacent to the surface, further, acting as a high-strength and ductile layer on the welded area, effectively delaying crack initiation. Recent findings demonstrate a significant increase in fatigue strength of the butt-welded double-V weld from FAT class 80 to FAT class 225, which corresponds to a more than tenfold extension in service life. This study for the first time investigates the potential of NMM technology as maintenance method for existing steel structures. Local fatigue-critical welded joints, which limit the service life of the overall structure, are treated with NMM and significantly increase the residual lifetime of the overall structure. This study presents a quantitative assessment of this residual lifetime increase and underlines the potential in regard to sustainability goals, economic viability and readiness of steel infrastructure.Publicationtype: Journal Article4 10 - 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 10 - Some of the metrics are blocked by yourconsent settings
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 Article38 19 - 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 Article10 27 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Fatigue assessment of welded joints using extreme value statistics and laser-based weld toe geometry analysisThis paper presents a novel approach for fatigue assessment of welded joints by employing extreme value statistics to predict the most critical weld toe geometry in welded structures. The methodology integrates advanced laser line sensor technology for precise weld geometry measurements, allowing the identification of geometrical features that are most likely to contribute to fatigue failure. By applying extreme value statistical techniques, the approach emphasizes the criticality of localized weld toe imperfections, providing a more accurate prediction of fatigue life compared to traditional methods. This technique offers improved reliability in fatigue life estimation for large welded structures, particularly in high-stress applications, and enhances the safety and durability of engineering designs.Publicationtype: Conference Paper26 19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Effect of geometric imperfections on CO₂ transport pipelines under fatigue loading(Elsevier, 2025-10); ; ; ; Ganendra, BenCatastrophic failures of CO₂ transport pipelines can result in severe economic losses and even casualties. During operation, pipelines are subjected to cyclic loading, which may lead to fatigue failure. The presence of geometric imperfections (GI) arising from installation processes introduces uncertainty that can affect the pipe’s strength under these conditions. This study assesses the impact of dent-type GI on the fatigue resistance of CO₂ transport pipelines using a validated finite element method (FEM). Fatigue analysis was conducted using the hot-spot stress approach on the straight tubular pipe with dent-type GI ranging from 0% to 20%. The pipe material is ASTM A36 steel, and the boundary conditions represent an onshore buried pipeline. The results show that the higher the percentage of dent-type GI, the lower the fatigue life due to the stress concentration effect. Further experimental tests and fluid–structure interaction studies are recommended to extend these findings.Publicationtype: Conference Paper47 9 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Grounding damage of stiffened hull panels: a numerical study on orientation effects and seabed-shape-driven energy dissipation(Elsevier, 2025-10); This study integrates experimental and numerical insights from stiffened-plate penetration tests with analytical seabed geometry to interrogate grounding damage. Using a canonical indenter–plate configuration for stiffened panels, hull penetration resistance is assessed against seabed conditions represented by binormal and polynomial rock geometries. Real multibeam bathymetry is interpolated into continuous surfaces and introduced as rigid indenters, enabling direct comparison between simplified plate-level fracture mechanics and complex grounding loads. Finite element analysis (FEA) with ANSYS LS-DYNA examines three orientations: horizontal (lateral seabed intrusion), vertical (local stranding), and 45° (combined penetration/raking). Results show fracture initiation is governed by local stiffener–plate interactions. Damage evolution and absorbed energy depend strongly on seabed roughness and the projected contact area, thereby linking the fidelity of analytical rock models to penetration resistance.Publicationtype: Conference Paper38 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Mechanical behavior assessment of dynamic ice forces using FE method: Interaction with an idealized offshore structure(Elsevier, 2025-10); ; ; Dynamic interaction between sea ice and offshore structures is a critical factor in design for operations in cold regions. This study investigates ice impact through numerical simulation to provide information relevant to offshore structural design. A finite element model was developed to simulate the collision between an ice sheet and a conical structure, with ice velocity as the primary parameter. The calculations were carried out using an explicit dynamics approach, which enables the simulation of time-varying impact forces. The results indicate that higher ice velocities result in greater stress within the ice sheet, generating larger reaction forces on the structure, with the increase following a nonlinear trend. These findings provide quantitative insight into the magnitude of loads that may be transmitted to offshore structures, underscoring the importance of accounting for dynamic ice forces in structural design.Publicationtype: Conference Paper24 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A review of composite materials for marine purposes: Historical perspective and current state(Elsevier, 2025); ; ; This study offers a concise review of the application of composite materials in marine environments, encompassing both historical perspectives and current conditions. Composite materials, which are both lightweight and robust, have been widely used in maritime structures, such as ships and offshore platforms, to enhance resistance to structural failure. The main focus of this study encompasses three aspects: the historical development of composites, failure theories of composite materials with an emphasis on damage caused by external loads, and recent advances in failure criteria for durability optimization. In this study, several failure theories, including the maximum stress-strain, Hashin, Tsai-Hill, Tsai-Wu, and Puck theories, are presented and reviewed, along with recent research results presented in tabular form. The expected results of this study can provide essential guidance for future research directions aimed at enhancing the reliability of composite materials in the maritime sector.Publicationtype: Conference Paper14 13