Browsing by Author "Ermakova, Anna"

Now showing 1 - 9 of 9
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    Corrosion-fatigue crack growth behaviour of wire arc additively manufactured ER100S-1 steel specimens
    (Elsevier, 2022-05-19) Ermakova, Anna; Ganguly, Supriyo; Razavi, Javad; Berto, Filippo; Mehmanparast, Ali
    The wire arc additive manufacturing (WAAM) technology is a promising fabrication technique which has been proven to have many advantages for producing large structures; however, the fatigue and corrosion-fatigue performance of WAAM steel components for application in the marine environments is still unexplored. In this study, the WAAM technique was employed to fabricate four specimens made of ER100S-1 steel, which were then tested under cyclic loading conditions in seawater to assess the corrosion-fatigue crack growth (CFCG) behaviour and hence suitability of this fabrication technology for offshore renewable energy applications. The test duration, cracking mechanisms and CFCG rate were investigated for each specimen and the material’s behaviour was investigated by considering the microstructural examinations. Furthermore, the obtained results were compared with the BS7910 standard recommended trends and experimental data available in the literature for conventionally built weldments made of different grades of steel which are commonly used for offshore applications.
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    Corrosion-fatigue crack growth behaviour of wire arc additively manufactured ER70S-6 steel parts in marine environments
    (Elsevier, 2022-07-17) Ermakova, Anna; Ganguly, Supriyo; Razavi, Javad; Berto, Filippo; Mehmanparast, Ali
    A crucial part of the structural integrity assessment of marine structures is the analysis of the fatigue crack growth behaviour of the welded joints in seawater environments, where the cracks often initiate and propagate under corrosion-fatigue loading conditions. In recent years, technological developments have facilitated the fabrication of steel components and structures using additive manufacturing technologies. Among the existing technologies, the Wire Arc Additive Manufacturing (WAAM) technique has proven to offer great potentials for fabrication of large-scale structures. The present study investigates the corrosion-fatigue crack growth (CFCG) behaviour of the WAAM parts fabricated using ER70S-6 low carbon steel wire to assess the suitability of this technology for future marine structures. In this experimental study, the cracking behaviour and test duration in corrosion-fatigue tests were investigated and analysed in conjunction with the microstructural examination of the tested specimens. Moreover, the obtained results were compared with the recommended trends available in BS7910 standard for conventional welded joints and the data available in the literature on widely used offshore structural steel weldments. The CFCG results obtained from this study contribute to the overall knowledge and design requirements for the new optimised functionally graded structures made with WAAM technology for marine applications.
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    The effect of surface treatment and orientation on fatigue crack growth rate and residual stress distribution of wire arc additively manufactured low carbon steel components
    (Elsevier, 2023-04-10) Ermakova, Anna; Razavi, Javad; Cabeza, Sandra; Gadalinska, Elzbieta; Reid, Mark; Paradowska, Anna; Ganguly, Supriyo; Berto, Filippo; Mehmanparast, Ali
    The directed energy deposition (DED) processes, such as laser metal deposition or Wire Arc Additive Manufacturing (WAAM), are gradually becoming the preferred method for fabrication of large-scale components using metal additive manufacturing (AM) technology. In this work, the possibility of fatigue life enhancement in WAAM built low carbon steel components, by means of rolling and laser shock peening surface treatment techniques, was investigated. A series of fatigue crack propagation tests were performed on surface treated ER70S-6 and ER100S-1 WAAM built specimens, and the results were analysed and compared with the untreated materials tested under the same loading conditions. The obtained results were interpreted in terms of the sensitivity of the cracking behaviour to the specimen orientation and extraction location. Furthermore, the residual stress profiles were measured, before and after applying the surface treatment techniques, and the effects of locked-in residual stresses on the fatigue performance of WAAM built components were discussed. Finally, a detailed texture analysis was performed on the surface treated and untreated regions of both WAAM built materials considered in this work. The obtained results from this study provide an insight into the advantages and disadvantages of various surface treatment techniques for fatigue life enhancement of WAAM built components with the view to extend the application of this advanced manufacturing technology to a wider range of industrial applications.
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    Experimental investigation of the fatigue crack growth behavior in wire arc additively manufactured ER100S-1 steel specimens
    (Wiley, 2021-10-26) Ermakova, Anna; Ganguly, Supriyo; Razavi, Javad; Berto, Filippo; Mehmanparast, Ali
    Wire arc additive manufacturing (WAAM) is an advanced fabrication technology for the rapid and efficient production of large-scale engineering structures. In order to design WAAM components for a given loading condition, it is essential to characterize the mechanical and failure behavior of the parts. In this study, the performance of ER100S-1 low carbon steel has been investigated by performing fatigue crack growth tests on compact tension specimens extracted from a WAAM built wall. The experimental results have been compared with the recommended trends in the BS7910 standard and with data available in the literature. Metallurgical investigations have been carried out to explore the microstructural effects on the fatigue behavior of the WAAM built components. The specimen location and orientation effects were comprehensively examined, and the results are discussed in terms of the influence of macroscopic and microscopic deformation on the overall response of the WAAM built components under fatigue loading conditions.
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    Fatigue crack growth behaviour of wire and arc additively manufactured ER70S-6 low carbon steel components
    (Springer, 2021-05-24) Ermakova, Anna; Mehmanparast, Ali; Ganguly, Supriyo; Razavi, Javad; Berto, Filippo
    The new emerging Wire and Arc Additive Manufacturing (WAAM) technology has significant potential to improve material design and efficiency for structural components as well as reducing manufacturing costs. Due to repeated and periodic melting, solidification and reheating of the layers, the WAAM deposition technique results in some elastic, plastic and viscous deformations that can affect material degradation and crack propagation behaviour in additively manufactured components. Therefore, it is crucial to characterise the cracking behaviour in WAAM built components for structural design and integrity assessment purposes. In this work, fatigue crack growth tests have been conducted on compact tension specimens extracted from ER70S-6 steel WAAM built components. The crack propagation behaviour of the specimens extracted with different orientations (i.e. horizontal and vertical with respect to the deposition direction) has been characterised under two different cyclic load levels. The obtained fatigue crack growth rate data have been correlated with the linear elastic fracture mechanics parameter ΔK and the results are compared with the literature data available for corresponding wrought structural steels and the recommended fatigue crack growth trends in the BS7910 standard. The obtained results have been found to fall below the recommended trends in the BS7910 standard and above the data points obtained from S355 wrought material. The obtained fatigue growth trends and Paris law constants from this study contribute to the overall understanding of the design requirements for the new optimised functionally graded structures fabricated using the WAAM technique.
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    The influence of laser shock peening on corrosion-fatigue behaviour of wire arc additively manufactured components
    (Elsevier, 2023-01-26) Ermakova, Anna; Braithwaite, Jarryd; Razavi, Javad; Ganguly, Supriyo; Berto, Filippo; Mehmanparast, Ali
    The need for increased manufacturing efficiency of large engineering structures has led to development of wire arc additive manufacturing (WAAM), which is also known as direct energy deposition (DED) method. One of the main barriers for rapid adoption of the WAAM technology in wider range of industrial applications is the lack of sufficient performance data on the WAAM components for various materials and operational conditions. The present study addresses this essential need by exploring the effects of laser shock peening surface treatment on corrosion-fatigue crack growth (CFCG) life enhancement of WAAM components made of ER70S-6 and ER100S-1 steel wires. The experimental results obtained from this study were compared with the CFCG trends from nominally identical specimens without surface treatment and prove the efficiency of the examined surface treatment method for corrosion-fatigue life enhancement and crack growth retardation of WAAM built steel components, regardless of the material type and specimen orientation. Furthermore, the residual stresses in the WAAM built specimens with and without surface treatment were measured to validate the influence of beneficial residual stresses, arising from surface treatment, on subsequent CFCG behaviour of the material. The residual stress profiles show the beneficial compressive stress fields in the surface treated areas which result in CFCG life enhancement. The results from this study make significant contribution to knowledge by evaluating the suitability of WAAM built steel components for application in offshore environments.
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    Investigation of mechanical and fracture properties of wire and arc additively manufactured low carbon steel components
    (Elsevier, 2020-06-20) Ermakova, Anna; Mehmanparast, Ali; Ganguly, Supriyo; Razavi, Javad; Berto, Filippo
    Wire and Arc Additive Manufacturing (WAAM) technology offers efficient fabrication of large scale products and is currently being implemented across various industries. In this study, an experimental investigation has been carried out to characterise the mechanical and fracture properties of WAAM components made of ER70S-6 and ER100S-1 metal wires. Microhardness, tensile and fracture toughness tests have been performed on the specimens extracted from the WAAM built walls which were fabricated using an oscillating pattern. The specimens were extracted from different locations, at the top and bottom of the WAAM walls, in two different orientations with respect to the deposition direction. The results show that the material hardness and yield strength of ER100S-1 built wall are higher than ER70S-6 by 62% and 42%, respectively. Moreover, in the walls made with both materials, the yield and ultimate tensile strength values were found to be slightly higher in specimens extracted in deposition (horizontal) direction when compared to specimens extracted in the built (vertical) direction. The average value of fracture toughness parameter for ER70S-6 has been found to be 88% higher than ER100S-1 material. Furthermore, the results show that the specimen extraction location in ER100S-1 wall significantly influences the fracture toughness values obtained from experiments. The results from this study have been compared with those available in the literature and discussed in terms of the mechanical and fracture properties effects on structural integrity assessment of WAAM components.
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    A review of life extension strategies for offshore wind farms using techno-economic assessments
    (MDPI, 2021-03-31) Pakenham, Benjamin; Ermakova, Anna; Mehmanparast, Ali
    The aim of this study is to look into the current information surrounding decommissioning and life extension strategies in the offshore wind sector and critically assess them to make informed decisions upon completion of the initial design life in offshore wind farms. This was done through a two-pronged approach by looking into the technical aspects through comprehensive discussions with industrial specialists in the field and also looking into similar but more mature industries such as the Offshore Oil and Gas sector. For the financial side of the assessment, a financial model was constructed to help portray a possible outcome to extend the life for a current offshore wind farm, using the existing data. By employing a techno-economic approach for critical assessment of life extension strategies, this study demonstrates the advantages and disadvantages of each strategy and looks to inform the offshore wind industry the best course of action for current wind farms, depending on their size and age.
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    Shape optimisation of composite corrugated morphing skins
    (Elsevier, 2016-10-15) Ermakova, Anna; Dayyani, Iman
    One of the challenging parts of the morphing wing is the anisotropic skin, which must be flexible enough to allow the wing to change its shape and at the same time being stiff enough to withstand the aerodynamic loads. Composite corrugated skins have exceedingly anisotropic behaviour as they are stiff along the corrugation direction but flexible in transverse direction. Hence, elastomeric coated composite corrugated panels have been proposed as a candidate for application in morphing wings. This paper presents the shape optimisation of the corrugation with respect to better performance of the morphing skin and manufacturing constraints. The shape of the skin is optimised by minimising the in-plane stiffness and weight of the skin and maximising its flexural out-of-plane stiffness. The objective functions were obtained from homogenised model that depends on geometric and mechanical properties of the coated corrugated panel by means of finite element method for thin beams. A few methods of optimisation were considered: aggregated and genetic algorithm methods as representative of two major categories of multi-objective solving methods. A number of different approaches are proposed in order to solve the problem, such as corrugated skin with and without elastomer coating. The advantages of the new optimised shape of the corrugated skin over the typical shapes are discussed.