The nondestructive assessment of the damage that occurs in components during service plays a key role for condition monitoring and residual life estimation of in-service components/structures. Ultrasound has been widely utilized for this; however most of these conventional methods using ultrasonic characteristics in the linear elastic region are only sensitive to gross defects but much less sensitive to micro-damage. Recently, the nonlinear ultrasonic technique, which uses nonlinear ultrasonic behavior such as higher-harmonic generation, subharmonic generation, nonlinear resonance, or mixed frequency response, has been studied as a positive method for overcoming this limitation. In this paper, overall progress in this technique is reviewed with the brief introduction of basic principle in the application of each nonlinear ultrasonic phenomenon.

Nonlinear ultrasonic techniques for nondestructive assessment of micro damage in material: A review

https://bura.brunel.ac.uk/bitstream/2438/13101/1/FullText.pdf

Cold spraying - A materials perspective

Cold gas dynamic spray or simply cold spray (CS) is a process in which solid powders are accelerated in a de Laval nozzle toward a substrate. If the impact velocity exceeds a threshold value, particles endure plastic deformation and adhere to the surface. Different materials such as metals, ceramics, composites and polymers can be deposited using CS, creating a wealth of interesting opportunities towards harvesting particular properties. CS is a novel and promising technology to obtain surface coating, offering several technological advantages over thermal spray since it utilizes kinetic rather than thermal energy for deposition. As a result, tensile residual stresses, oxidation and undesired chemical reactions can be avoided. Development of new material systems with enhanced properties covering a wide range of required functionalities of surfaces and interfaces, from internal combustion engines to biotechnology, brought forth new opportunities to the cold spraying with a rich variety of material ...

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Cold spray coating: review of material systems and future perspectives

Review of progress, QNDE

Finite-amplitude waves in isotropic elastic plates

The nonlinear acoustic applications for material characterization are reviewed. The general theoretical analysis of the effects of nonlinearity, dissipation, dispersion, and diffraction on intense ...

Review / Sythèse Nonlinear acoustic applications for material characterization: A review

This article discusses a number of modern techniques used for the analysis of works of art. The most widely used approaches as well as lesser known ones are outlined in terms of their applications and the kind of information on the condition of artworks that can be extracted. Special attention is paid to the method of thermographic analysis of works of pictorial art. The principles of the technique, various computational approaches, and safety concerns are discussed. A set of examples is provided for the demonstration of the capabilities of thermographic assessment, including a range of real canvas and panel paintings exhibited in museums and in private collections.

A review of imaging methods in analysis of works of art: Thermographic imaging method in art analysis

In the present study, a novel TiO 2 -based coating containing nanosized hydroxyapatite (n-HA) has been formed on commercially available Ti–6Al–4V (Grade 5) alloy substrates by the Plasma Electrolytic Oxidation (PEO) technique. The TiO 2 :n-HA coating deposition was provided in an aqueous solution of disodium hydrogen phosphate containing suspended hydroxyapatite nanoparticles under a pulsed bipolar current mode. The surface morphology of the formed coatings has been examined by Scanning Electron Microscopy (SEM), while the element composition of the coatings has been determined by Energy Dispersive X-ray analysis (EDS). The presence of HA nanoparticles within the formed coatings has been analyzed by Fourier Transform Infrared Spectroscopy (FTIR). The corrosion resistance of the TiO 2 :n-HA coatings has been studied by electrochemical methods, including open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy, and compared to the corrosion behavior of bare titanium. The results indicate that the formed PEO coatings exhibit a porous network structure with embedded n-HA particles uniformly distributed over the entire surface of the coatings. The PEO coated samples showed substantially higher corrosion resistance compared to the bare Ti–6Al–4V substrate material. The PEO-formed TiO 2 :n-HA layers reduce the corrosion of titanium alloy implant materials and can be used as a bioactive biomimetic coating to enhance implant surface bioactivity and osseointegration.

Characterization and corrosion evaluation of TiO2:n-HA coatings on titanium alloy formed by plasma electrolytic oxidation

Corrosion attack of aluminum- based alloys is a major issue worldwide. This study provides a report on the electrochemical behavior of several types of protective metal coatings obtained by low pressure cold spray and describes the performance of the latter’s corrosion resistance properties. In this manner several metal feedstock compositions were cold sprayed on AA2024-T3 Alclad substrate. Electrochemical methods, such as OCP and DC polarization, were used in combination with materials characterization techniques to assess the performance of protective coating layers. All sprayed samples were tested in the accelerated corrosion chamber for a time period of up to 500 hours to obtain corrosion kinetics data, and with specific attention being focused on the characterization of the coating’s properties. The overall conclusion of this study is that the LPCS process could be utilized to deposit corrosion protection coatings and as to repair aluminum structures during overhaul maintenance schedule in an industry.

Corrosion Protection of Light Alloys Using Low Pressure Cold Spray

The radial injection gas dynamic spray (RIGDS) technology of powder coatings deposition was considered for this work. A coating was created by injecting powders with variable compositions into a supersonic air jet and depositing powder on the substrate. This study describes the preliminary analysis of an air gas dynamic spray method realized by a portable RIGDS apparatus with a radial injection of powder. Attention was given to shock compaction processes during the coating structure formation and examples of powder mixtures utilization in RIGDS. It was shown that the operational parameters of supersonic powder-gas jet have a significant influence on the coating's microstructure, thus defining the high performance of the coating. Compaction and bonding of particles were analyzed.

R. Gr. Maev

Papers

Review / Sythèse Nonlinear acoustic applications for material characterization: A review

A review of imaging methods in analysis of works of art: Thermographic imaging method in art analysis

Characterization and corrosion evaluation of TiO2:n-HA coatings on titanium alloy formed by plasma electrolytic oxidation

Corrosion Protection of Light Alloys Using Low Pressure Cold Spray

Air gas dynamic spraying of powder mixtures: Theory and application