Synergetic Design of Transparent Topcoats on ITO-Coated Plastic Substrate to Boost Surface Erosion Performance

Transparent conductive films (TCFs) have received much research attention in the area of aeronautical canopies. However, bad wear, corrosion resistance and weak erosion performance of TCFs dramatically limit their scalable application in the next-generation aeronautical and optoelectronic devices. To address these drawbacks, three types of optically transparent coatings, including acrylic, silicone and polyurethane (PU) coatings were developed and comparatively investigated ex situ in terms of Taber abrasion, nanoindentation and sand erosion tests to improve the wear-resistance and sand erosion abilities of ITO-coated PMMA substrates. To elucidate the sand erosion failure of the coatings, the nanoindentation technique was employed for quantitative assessment of the shape recovery abilities under probe indentation. Results show that the PU topcoats can greatly enhance the sand erosion properties, which were superior to those of acrylic and silicone topcoats. This result can be attributed to the good toughness and self-healing properties of PU topcoats. Additionally, high hardness and good Taber abrasion properties of the ITO films and silicone topcoats did not have an obvious or affirmatory effect on the sand erosion abilities, based on their brittleness and irreparable properties under sand erosion.

Friction Stir Processing on the Tribological, Corrosion, and Erosion Properties of Steel: A Review

The eventual material degradation of steel components in bio-implant, marine, and high-temperature applications is a critical issue that can have widespread negative ramifications from a safety and economic point of view. Stemming from their tribological, corrosion, and erosion-based properties, there is an increasing need to address these issues effectively. As one solution, surface processing techniques have been proposed to improve these properties. However, common techniques tend to suffer from issues spanning from their practicality to their high costs and negative environmental impacts. To address these issues, friction-stir-processing (FSP) has been one technique that has been increasingly utilized due to its cost effective, non-polluting nature. By inducing large amounts of strain and plastic deformation, dynamic recrystallization occurs which can largely influence the tribological, corrosion, and erosion properties via surface hardening, grain refinement, and improvement to passive layer formation. This review aims to accumulate the current knowledge of steel FSP and to breakdown the key factors which enable its metallurgical improvement. Having this understanding, a thorough analysis of these processing variables in relation to their tribological, corrosion, and erosion properties is presented. We finally then prospect future directions for this research with suggestions on how this research can continue to expand.

Experience in Selection of Cavitation-Resistant Steels for Inducers of Centrifugal Pumps of JSC "VNIIAEN" Specialization

To formulate the problems of increasing the resistance to cavitation erosion of the hydraulic parts of centrifugal pumps by selecting the most suitable steel grades and to review the experience of using cavitation-resistant steels for inducers of centrifugal pumps of JSC “VNIIAEN” specialization. Analytical and statistical analyses were carried out using research and experimental development data of cavitation-resistant steels for inducers of centrifugal pumps at JSC "VNIIAEN", as well as using data from open access publications. The article deals with the problem of centrifugal pump hydraulic part failure caused by cavitation. It has been actually demonstrated that the most effective way to improve the cavitation performance of centrifugal pumps is to use an inducer upstream of the first stage impeller. Therefore, the study of cavitation-resistant steels was carried out on inducers which are most exposed to cavitation when operating under condition of developed cavitation. The results of tests carried out on experimental model test rig and full – scale pumps are presented. The selection of steels resistant to cavitation has been optimized. The relationship between the chemical and mechanical properties of steels and resistance to cavitation is shown. In addition, the essential role of structural properties of steel is shown in terms of heat of steel 08Х15Н4ДМЛ. The article provides a rationale for the fact that the potential for improving the cavitation-erosion properties of the hydraulic parts of centrifugal pumps solely by improving their hydrodynamic characteristics is practically exhausted; therefore, more attention should be paid to the search for cavitation-resistant steels used for the manufacture of hydraulic parts. It is shown that in order to achieve the best cavitation-erosion properties, it is necessary to provide a certain interaction of the selected chemical and mechanical properties of materials. The possibility of achieving better resistance to cavitation erosion by modifying the melting process is shown in terms of steel 08Х15Н4ДМЛ.

Characteristic of Erosion Properties and Relationship With Geotechnical Properties for Red Riverbank Soil in Hanoi, Vietnam

Soil erosion properties are the main factors affecting riverbank and river channel stability. In this paper, a modified water flume in the laboratory was conducted to evaluate the characteristic of erosion properties including the critical shear stress, the slope of the erosion curve, and erosion rate. The relationships between erosion properties and geotechnical properties as dry density, grain size distribution, shear strength, and soil suction were built. Results obtained from laboratory tests indicate (i) the clay content, cohesion force, residual suction has a great effect and linear correlation in the relationships with the critical shear stress and erosion rate. While the change in clay content leads to a markedly change in the erosion rate. The difference of 5 % clay content enough to build great effects on the erosion rate curve for the Silt soil group; (ii) the sand content has the greatest influence on the slope of the erosion curve (the initial slope and the erosion slope); (iii) the density also has a close relationship with the critical shear stress and the erosion slope, but not for a fine–sand mixture with clay content less than 10%. Based on obtained results and relationships found in this paper, the cohesion force and residual suction should be considered in process of soil riverbank improvement and riverbank undercutting erosion protections.

Experimental Investigation on the cavitation erosion properties of concrete with different damage degrees under ultrasonic cavitation

<p>Cavitation erosion, widely existing in many flood discharge structures of concrete dams, has a direct impact on the performance of concrete. Understanding the cavitation erosion properties of concrete with different damage degrees is vital to the long-term operation safety of concrete dams. In this study, the cavitation erosion properties of concrete with different damage degrees under ultrasonic cavitation are systematically investigated in the laboratory, including three damage degrees and three ultrasonic cavitation intensities. Based on the stress-strain curve of concrete under uniaxial compression, the damage variable is defined and the corresponding concrete specimens are pre-treated. The experimental results reveal the influence of the damage degrees on the cavitation erosion properties of concrete, regarding the mass erosion characteristics, the predominant failure behaviour, and the coupling effect mechanism. Image analysis of the specimens shows some level of deterioration at the surface and inside the specimens. Under higher damage degree or cavitation intensity, the concrete is characterized by higher mass erosion rate, higher cumulative cavitation damage and worse surface smoothness. Furthermore, the micro-cracks caused by concrete damage aggravate the aggregate liberation of concrete under ultrasonic cavitation, and the crack propagation under coupling effect of damage and cavitation is most likely driven by the combination of fatigue-like crack growth and deformation, thereby reducing the service life of concrete.</p>