Laplace Transform for Finite Element Analysis of Electromagnetic Interferences in Underground Metallic Structures

A numerical methodology is proposed for the calculation of transient electromagnetic interference induced by overhead high-voltage power lines in metallic structures buried in soil—pipelines for oil or gas transportation. A series of 2D finite element simulations was employed to sample the harmonic response of a given geometry section. The numerical inverse Laplace transform of the results allowed obtaining the time domain evolution of the induced voltages and currents in the buried conductors, for any given condition of the power line.

Dynamic inversion of planar-chiral response of terahertz metasurface based on critical transition of checkerboard structures

Dynamic inversion of the planar-chiral responses of a metasurface is experimentally demonstrated in the terahertz regime. To realize this inversion, the critical transition of the checkerboard-like metallic structures is used. Resonant structures with planar chirality and their complementary enantiomeric patterns are embedded in the checkerboard. Using vanadium dioxide as a variable resistance, the metasurface is implemented in the terahertz regime. The responses of the metasurface to circularly polarized waves are then characterized by terahertz time-domain spectroscopy. Further, the sign of the circular conversion dichroism, which is closely related to the handedness of the planar chirality of the metasurface, is observed to be inverted at 0.64 THz by varying the temperature. Such invertible planar-chiral responses can be applied practically to the handedness-invertible chiral mirrors.

Processing, Properties, and Uses of Lightweight Glass Fiber/Aluminum Hybrid Structures

The replacement of heavy metallic structures by high-performance lightweight composite materials is a prominent solution to fulfill the continuous demand in different industrial sectors. Lightweight structures based on aluminum-glass fiber reinforced plastics (GFRP) sandwich panels have been increasingly utilized in the shipbuilding, automotive, and aerospace industries for their striking mechanical and physical properties. These advantageous properties have resulted from the combination of the high tensile and flexural strengths, increased hardness, and the improved wear-resistance of aluminum laminate with the unique properties of lightweight stiffness and high strength weight ratio of glass fiber-reinforced. In this chapter, the various processing approaches, properties, and applications of these sandwich structures are summarized from a wide range of literature.

Fabrication of Tailor-Made Metallic Structures for Lightweight Applications and Mechanical Behaviour

Tailor-made metallic structures are fabricated by welding, adhesive bonding, and mechanical joining methods. Here the aim is not only to fabricate lightweight structures, but also to develop novel methods of joining. Lightweight structures are advantageous in several ways including reduction of fuel consumption and vehicle emissions. Developing novel methods of joining is advantageous due to the possibility of joining of dissimilar materials, improved mechanical performance, and microstructures. In the chapter, initially, tailor-welded blanks (TWB) are introduced, and after that, fabrication of TWBs by laser welding, friction stir welding, and friction stir additive manufacturing are elaborately discussed. Some critical issues in modeling the deformation during fabrication of TWBs is also discussed. A brief account of mechanical behavior of adhesive bonded sheets and mechanical joining are presented in the later part.

Detection of different chemical binders in coatings using hyperspectral imaging

Organic coatings protect metallic structures of significant commercial value. Regular inspections of coatings are required to ensure their integrity and, therefore, to verify their stated performance. However, for metallic structures located in harsh places, coating inspection can pose significant safety and logistical challenges. Near-infrared (NIR) spectroscopy is a rapid, nondestructive and relatively inexpensive analytical technique. It is currently employed to analyze different chemicals in fields like agriculture, food, and pharmaceuticals. Similarly, hyperspectral imaging (HSI) creates a spatial map of spectral information by measuring light reflected from a material. In this work, hyperspectral imaging in the NIR portion of the electromagnetic spectrum (NIR-HSI) is used to accurately distinguish between the chemically different binders employed in commercial organic coatings. In addition, k-means clustering is explored as a tool to provide diagnostic information about the spatial inhomogeneities in the chemical structure of an applied coating, which, if undetected, can lead to coating defects during service life. The results of this work suggest that the NIR-HSI could be used for remote inspections of organic coatings.

Corrosion Behavior of Cold Sprayed Aluminum Alloys 2024 and 7075 in an Immersed Seawater Environment

This paper describes the polarization and basic pitting behavior of 2024 and 7075 aluminum alloys produced by high pressure cold spray deposition. While cold spray is showing great promise as a solid state repair approach for metallic structures, the corrosion behavior of these materials still needs investigation, particularly in describing the potential galvanic interactions with the repaired substrate. Potentiodynamic testing was performed on cold sprayed (CS) aluminum alloys 2024 and 7075, and corresponding wrought AA2024-T3 and AA7075-T651 alloys for comparison. Testing used ASTM D1141 artificial seawater for potentiodynamic polarization, following the MIL-STD 889C standard for testing with consistent results. Pitting was investigated using 120-hour immersion tests, with subsequent photography, SEM imaging and EDS analysis of the surface. CS-2024 was found to be more active and reactive than wrought, with enhanced anodic kinetics; it experienced more aggressive pitting than the AA2024-T3 during the immersion test. CS-7075 was found to be less active and more reactive than wrought, with enhanced cathodic kinetics; the CS-7075 demonstrated reduced pitting compared to the AA7075-T651. Possible causes for these differences are discussed, including material homogeneity, CS powder intermetallics, and spray parameters. Overall, CS-2024 and CS-7075 should have little galvanic interaction with their corresponding substrates.

Biharmonic submanifolds in metallic Riemannian manifolds

In this paper, we study the biharmonic submanifolds of Riemannian manifolds endowed with metallic and complex metallic structures. In case of both the structures, we obtain the necessary and sufficient conditions for a submanifold to be biharmonic. Particularly, we find the estimates for mean curvature of Lagrangian and complex surfaces.

Investigation of a Relative Weight Ratio of Graphite/Zinc Matrix Composite with a High-Resistance to Corrosion

There has been a significant increase in the use of composite materials to reinforce metallic structures. Such an increase has been especially noted in marine and underground applications, where there is a higher corrosion impact. Whilst there have been several attempts to investigate the mechanical properties of several synthesized composite materials, few of these have analyzed the corrosion of such composite materials at different weight ratios. The aim of this paper is to explore the best weight ratios of a graphite/Zinc composite matrix that would yield the lowest corrosion rate for a variety of applications. The research is validated using experimentation based on six additives of graphite (1wt%, 2.5wt%, 4wt%, 6wt%, 8wt%, and 10wt%), which are used as reinforcements for a range of weight ratios. The additives were prepared using the powder metallurgy method. The corrosion rate for all specimens used was carried out at the room temperature of 27 °C. Analysis results showed that 1wt% of graphite additive has the highest corrosion resistance compared to other weight ratios tested. This has been verified by examining the microstructure of the composite using an optical microscope for 12h, 24h, and 48h of immersion time in a 1M HCl acid solution.

Development of the Protection Coat for Metallic Structures Based on the Intercalated Graphite Compounds

The practicability of introducing a synthesized graphite compound, intercalated with oxygen, into the protection coat is grounded. The composition and the method of manufacturing a protection coat based on the oxidized graphite, which does not require preliminary preparation of the metal structures surface before welding with an open arc, have been developed. The effect of the oxidized graphite content in the composition of the protection coat on its thermal stability and thermal expansion coefficient is analyzed. The main technological characteristics of the developed protection coat have been investigated and their compliance with the basic criteria for constructing protection coats has been confirmed.