Statistical investigations into automated spray‐applied stripe coats to complex geometries of floating offshore wind foundations
Materials and Corrosion
The automation of coating processes allows consistent, economical, and ecological applications. I... more The automation of coating processes allows consistent, economical, and ecological applications. In this study, the effects of various surface geometries—steel plates, plates with weld seams, plates with bolts, and plates with welded fillets—on the uniformity of dry film thickness (DFT) after robotic stripe coating applications with an electrostatic spray device are investigated and analyzed with statistical methods. Robot traverse rate, pump pressure, and voltage. Based on analysis of variance studies, the robot traverse rate was identified to be the most influential factor. For plates with weld seams, an optimization study was conducted, resulting in a multiresponse prediction model. The model achieved a DFT within the target range across all measuring points within a 95% confidence interval. At an optimized factor combination (117 mm/s, 0.3 MPa, 61.4 kV), the DFT values ranged between 100 and 142 µm. The findings of this study provide fundamentals for achieving uniform coating dis...
The determination of fractal dimensions of blast-cleaned steel substrates by means of comparative cross-section image analysis and contact stylus instrument measurements
Journal of Adhesion Science and Technology
Korrosionsschutz von Offshore-Turmsegmenten
adhäsion KLEBEN & DICHTEN
Effects of adhesive type on the mechanical properties of adhesive joints between polyurethane top coats and polyurethane-based adhesives after accelerated atmospheric ageing
Marine Structures
Abstract The performance of a sealed stainless steel bracket system, adhesively bonded with two p... more Abstract The performance of a sealed stainless steel bracket system, adhesively bonded with two polyurethane-based adhesives (flexible adhesive, stiff adhesive) onto a marine polyurethane top coat, is investigated. The investigated joint connections on the coatings exhibited a high mechanical stability even after accelerated ageing (salt spray exposure, cyclic temperature variations, high relative humidity). The aged joints retained up to 81% of their tensile strength and up to 92% of their lap-shear strength. The torsional rigidity of the adhesive joint exceeded the required clamping torque of the designed bolt. A cyclical lifetime of >9·106 load cycles was estimated. Effects of cyclic ageing on the creep performance of the adhesive joint were found to be insignificant. Under tensile loads, the joints with stiff adhesive material exhibited a linear-elastic performance without the capability to deform prior to failure. The joints with the flexible adhesive material, in contrast, exhibited a behavior typically for ductile materials featuring a pronounced yield plateau prior to failure. Failure loads were higher, and displacement was notably lower, for the joints with stiff adhesive material. All joint connections met the requirements for a safety factor for the design for marine applications (11.6 for the flexible adhesive; 14.3 for the stiff adhesive). When the flexible adhesive is applied, the cohesive strength of the adhesive material is the limiting design factor. When the stiff adhesive is utilized, the load carrying capacity is higher, and the interface between priming coat and steel substrate is the limiting design area of the joints. The strength utilization of the adhesive materials depended on the particular structure of the entire joint configuration, particularly on the interface between steel substrate and the coating material. A number of assessment factors, namely stress limit factor, coating adhesion factor and safety factor, are introduced and discussed for tensile and shear loads.
Fractal dimensions of blast-cleaned steel surfaces and their effects on the adhesion of polymeric foil systems with integrated pressure-sensitive adhesives
International Journal of Adhesion and Adhesives
Subsequent Mounting of Brackets to Coated and Uncoated Surfaces Using Adhesives
Corrosion, Apr 19, 2021
Impact damages to organic coating systems of offshore wind turbines - corrosion progress and repair strategies
The selection and adjustment of an effective abrasive mass flow rate is one of the most important... more The selection and adjustment of an effective abrasive mass flow rate is one of the most important requirements for efficient blast-cleaning processes. Steel grit is one of the most widely used abrasive materials in the industry, and the adjustment of effective steel grit mass flow rates can improve efficiency and decrease costs. Systematic investigations into the metering behavior of steel grit have not been performed yet. The paper deals with a systematic investigation into the flow of high-carbon cast-steel grit particles through a metering valve. The investigation involves abrasive mass flow rate measurements, and the results are statistically interpreted based on design of experiments and analysis of variance. Four process parameters are varied, namely static air pressure, nozzle diameter, valve opening, and particle size range. Abrasive mass flow rate increases if air pressure, nozzle diameter, or valve opening increases, and it decreases if particle size becomes smaller. Only ...
For the first time, effects of polymer hardness on the abrasive wear resistance of organic coatin... more For the first time, effects of polymer hardness on the abrasive wear resistance of organic coatings, designed for the corrosion protection of offshore wind power structures, are investigated at varying normal forces. The tests are performed with a specially designed Taber abrasion machine. The results reveal statistically significant effects of the polymer material Vickers hardness on the coating resistance against abrasive wear. With respect to the generic polymer type, the following ranking of the abrasive wear resistance is estimated: epoxy > polysiloxane > polyurethane. Thus, the most frequently applied top coat material (polyurethane) exhibits the lowest abrasive wear resistance and may not be capable to protect the underlaying epoxy-based intermediate coats. Polysiloxane would provide a longer protection against abrasive wear. The dominant material removal modes in all polymers are microcutting and microfracturing, whereby the former mode is dominant at lower normal forces, and the latter mode is dominant at higher normal forces. The power exponent of the classical power relationship V H A P n depends on the mixture of the associated removal modes. The authors introduce a new transition parameter in order to rank the associated individual material removal processes. Based on an empirical-mathematical model, a two-parameter Weibull distribution function is derived, which links the transition parameter to the applied normal force. A two-dimensional graph (nomogram) is designed, where the different material removal modes are situated as functions of normal force and transition parameter.
Coating specifications for offshore wind energy devices (OWEAs) are still based on specifications... more Coating specifications for offshore wind energy devices (OWEAs) are still based on specifications for the offshore oil and gas industry. Recently, two standards, developed for OWEA in the German offshore section (North Sea and Baltic Sea), were issued. This article reviews current offshore standards and commercial specifications used in the German OWEA industry. Stresses are defined for different zones of the structures. Specified coating systems for different stresses, including testing methods, are discussed. A review of 34 commercial coating specifications for OWEA in the North Sea and the Baltic Sea is provided. Evaluation parameters include number of layers, dry film thickness, and binder types for different coats. Special coating requirements are discussed, namely impact resistance, abrasion resistance, icing/ deicing performance, low friction, color and gloss stability, and low-temperature performance. Finally, trends for the utilization of thermal spray metals are reviewed.
The paper deals with a systematic investigation into the flow of copper slag abrasive particles t... more The paper deals with a systematic investigation into the flow of copper slag abrasive particles through a metering valve. The investigation involves abrasive mass flow rate measurements, and the results are statistically interpreted based on DoE (Design of Experiments) and ANOVA (Analysis of Variance). Three process parameters are varied, namely static air pressure, nozzle diameter and valve opening. Abrasive mass flow rate increases if air pressure, nozzle diameter or valve opening increase. All three main factors provide statistically significant effects, whereby the strongest effect occurs due to changes in valve opening. Although a non-standardized quadratic regression model delivers a satisfactory agreement with experimental results, it misjudges the statistical significance of the process parameters. A standardization of the regression function omits multicollinear effects and simplifies the regression function. A standardized quadratic regression model is found to be capable to statistically describe the relationships in the scope of the evaluation effort.
Based on a specially designed accelerated wave chamber ageing tests, the corrosion protection cap... more Based on a specially designed accelerated wave chamber ageing tests, the corrosion protection capability of organic coatings over cut edges is investigated. The edges are rounded with different tools, including CO 2-laser, solid-state laser, plasma beam, grinding and milling tools. Two coating systems for ballast water tank environments and two rounding radii are considered. The samples are placed on four locations in the wave chamber, characterized through different corrosive environments. DOE (Design of Experiments) and ANOVA (Analysis of Variance) are used to rank the parameter effects. It is shown that edge radius has no statistically significant effect on the corrosion protection performance of the coatings. In contrast, rounding process and chamber location are extremely significant. A hypothesis of a hierarchic geometrical edge structure is proposed.
International Journal of Adhesion and Adhesives, 2020
The performance of stainless steel brackets, adhesively mounted with a soft polyurethane-based ac... more The performance of stainless steel brackets, adhesively mounted with a soft polyurethane-based accelerated 1component adhesive onto completely coated steel substrates, is investigated. The investigated joint connections on typical marine top coats, namely polyurethane, polysiloxane and epoxy, exhibited a high mechanical stability even after accelerated ageing (salt spray exposure, cyclic temperature variations, high relative humidity). Tensile strength and shear strength criteria for a designed loading capacity of 50 kg were achieved with a safety factor of >10. All failure strength values were lower than the adhesion strength of the coatings to the steel. The adhesive material maintained its high deformability after ageing. The torsional rigidity of the adhesive joint exceeded the required clamping torque of the designed bolt. A cyclical lifetime of >9⋅10 6 load cycles was estimated. Effects of cyclic ageing on the creep performance of the adhesive joint were found to be insignificant. All adhesive joint connections met the requirements for a safety factor for the design for marine applications. Under sealed conditions, the ingress of moisture and chloride was avoided, and deterioration mechanisms typical for unsealed joints in marine environments (e.g. moisture penetration, adhesive material plastification, interfacial delamination) did not take place. Effects of mechanical and structural parameters as well as surface parameters of the top coat materials on the performance of the joints were statistically insignificant.
This Short Communication refers to the relationship between edge coverage (as a geometrical prote... more This Short Communication refers to the relationship between edge coverage (as a geometrical protection parameter for edges) and the corrosion protection performance of organic coatings over edges. Results recently reported in Progr. Organ. Coat. (Vol. 101, pp. 186-194; Vol. 102, pp. 167-177) are reconsidered and interpreted by means of Pearson's correlation coefficient. It is shown that no linear correlation exists between edge coverage and corrosion protection performance over cut edges.
Classified substrate roughness parameters of blast-cleaned steel substrates and their effects on fractal dimensions
Journal of Adhesion Science and Technology
Schlussbericht zum Projekt: OWSMV - Offshore Wind Solutions Mecklenburg-Vorpommern im Verbundprojekt 3: Transport und Installation; Teilprojekt TP 3.E: "Schutz von OWEA-Beschichtungen vor Transport- und mechanischen Schäden" : im Rahmen des Förderprogramms BMBF-Innovationsoffensive: "Wachstumsker...
Schlussbericht zum Projekt: OWSMV - Offshore Wind Solutions Mecklenburg-Vorpommern im Verbundprojekt 2: Energieübertragungsplattformen; Teilprojekt TP 2.D: "Montage nachträglicher Anbauteile mittels Klebeverbindung" : im Rahmen des Förderprogramms BMBF-Innovationsoffensive: "Wachstumskerne-Untern...
The assessment of fractal dimensions with the direct use of scanning electron microscopy (SEM) images from blast-cleaned steel substrates
Journal of Adhesion Science and Technology, 2021
Nachträgliches klebtechnisches Fügen von Haltern auf bereits beschichtete Stahloberflächen
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Papers by Tom Marquardt