Surface Review and Letters

Over recent decades, considerable effort has been made to discover new and efficient corrosion inhibitors for reinforced concrete in corrosive media. Organic, inorganic, and green corrosion inhibitors have been used to inhibit the corrosion of reinforcing bars in contaminated concrete structures. Despite the efficacy of corrosion inhibitors, an evaluation of the effect of inhibitors on other concrete properties plays a prominent role in assessing the industrial use of these effective materials. A comprehensive study of improvements in concrete properties such as workability, setting time, air content, fresh density, compressive strength, tensile strength, flexural strength, consistency, elasticity, water absorption, and water permeability after the addition of a corrosion inhibitor allows for effective reduction of reinforcement steel corrosion. Hence, this study summarizes all corrosion inhibitors used for concrete reinforcement during the last decade (2010–2020), as well as their effects on the properties of contaminated concrete.

The staircase/stair-stepping effect causes wrapping, shrinkage, and surface roughness in additively manufactured (AM) parts. Consequently, abrasive flow finishing (AFF) or abrasive flow machining (AFM) may be employed to improve the AM part surface finish. This study developed an environmentally friendly AFM media using rice husk ash as base material, waste vegetable oil as a liquid synthesizer, and natural additives, i.e. glycerin. The new newly developed rice husk ash-based AFM media (HSAFM) characterization was done using Fourier Transform Infrared (FTIR) spectroscopic method and thermogravimetric analysis (TGA). AFM medium viscosity was optimized using a Taguchi design ($L_9$). These FDM-printed extrusions die inserts were finished using optimized AFM media in a one-way AFM system. A new AFM fixture with a mandrel guide was developed to direct media flow inside the die cavity to ensure uniform finishing. Experimental research has been done on finishing the FDM-printed extrusion die insert pattern using the Box–Behnken Design (BBD)-based experimental design of the response surface methodology (RSM) technique. The surface roughness Ra $\mathrm{\Delta }$28.16 $\mu$m was improved by 96% with the following process parameters: media viscosity of 60 Pa/s, the layer thickness of 0.3, and 90 min of finishing time.

Studies reveal that the most prominent cause of bearing failure is a crack on any of its mating surfaces. When the crack is initiated, the bearing can still be used for some duration, but this is majorly depending upon the loading conditions. This work primarily focuses on the effects of different levels of static loading on the crack propagation after crack initiation. To analyze the effect of static loading, an axial groove defect was seeded on the outer race of a taper roller bearing randomly and bearing run continuously under five different static loading conditions. Initially, the bearing was made to run under loading conditions to initiate the crack naturally but the crack was not initiated even after 800 h of running. Therefore, crack was initiated artificially for the purpose of studying crack propagation. It was observed from the experimentation that in the case of maximum static load of 20 kg, the crack propagates rapidly in terms of area after 109 h of continuous running, whereas in the case of no load, it started propagating quickly after 267.5 h of running. Statistical analysis was also carried out for the recorded signals at different intervals of times, and it was observed that the Shannon entropy value was showing a sudden rise with the edge breakage (visually verified) while the crack was propagating. However, in the statistical analysis, none of the parameters showed a correlation with crack propagation. To develop the correlation of crack propagation, Shannon entropy of high, medium and low frequency bands of continuous wavelet-based (CWT) was carried out using different wavelets. Shannon entropy for high frequency band of CWT using Daubechies 10 as mother wavelet has responded well to the crack propagation as the value showed a sudden rise and an overall increase for edge breakage and crack propagation, respectively. A high frequency band of CWT using Daubechies 10 was found suitable for detecting edge breakage and crack growth at the same time because of its capability to respond to transient characteristics for a large duration of time.

In order to continuously update the prediction model based on the ever-expanding data set solely, this study established a continual learning model, i.e. the elastic weight consolidation (EWC)-based artificial neural network (ANN) model to predict the hardness of Ni–Cu–CrBN coating that could be used in tribology field. The results showed that after being trained by the ever-expanding dataset, the determination coefficient $R^2$ of the normal ANN model on old data decreased to 0.8421 while that of the EWC-based ANN model was still 0.9836. It was indicated that the EWC-based ANN model presented good performance on both new and old data after being trained by the ever-expanding dataset solely, which saved time and was more in line with practical application.

This study was carried out to improve the surface of the AA7075 alloy, which does not resist wear. Therefore Al–SiC composite layer on the surface of AA 7075 material was coated with Al+5vol.%SiC powders under 600°C and 100, 120, 140 MPa pressure by the hot pressing sintering method. The microstructure of the transition zone between the coating and the substrate material was analyzed by using optical microscopy (OM), energy dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM) techniques. In addition, XRD measurement and microhardness of the coating layer were obtained. Coating surface was also subject to linear reciprocating wear test and coefficient of friction (COF), wear volume, and mass loss were detected. The results have shown that micro-pores between Al and SiC powders reduced by increasing the pressing pressure. However, although there was a reduction in wear volume and mass loss, microhardness values dramatically increased. Wear test was modeled in ANSYS 2021 R2 package program depending on Archard’s law and numerical analysis was conducted. As a result of the experimental results and numerical analysis, the volume loss values occurring in the coating area were found to be compatible with each other.

This paper explores the bioconvective Maxwell fluid flow over a horizontal stretching sheet. The Maxwell fluid flow is considered in the presence of gyrotactic microorganisms. The velocity slips and convection conditions are used in this investigation. Additionally, the Cattaneo–Christov heat and mass flux model, Brownian motion, thermophoresis, and activation energy are employed in the flow problem. The model formulation has been transferred to a dimension-free format using similarity variables and solved by the homotopy analysis approach. Figures have been sketched to depict the HAM convergence. The consequences of this study are that the velocity of Maxwell fluid flow reduces for higher Hartmann number, buoyancy ratio factor, and bioconvective Rayleigh number, whereas the increasing behavior in velocity profile is seen against Deborah number. The thermal characteristics of the Maxwell fluid flow diminish with developing values of the thermal relaxation factor and Prandtl number, while augmenting with the increasing Brownian motion, thermal and concentration Biot numbers and thermophoresis factor. The rate of thermal transmission of the Maxwell fluid flow enhances with the increasing Prandtl number, and mixed convective factor, while diminishing with the increasing buoyancy ratio factor, thermophoresis factor and Brownian motion factor.

Laser cutting is a one of the efficient manufacturing processes in industry to cut the hard materials by vaporizing. Stainless steel (SS347) is the most popular material for many applications due its unique characteristics such as efficiency to retain good strength with no inter-granular corrosion even at elevated temperatures. However, the cutting or machining of this material is very difficult. On the other side, the machining cost of laser process is high when compared with other processes. In this work, GRA and TOPSIS techniques are used to study the laser cutting process parameters of SS347. The obtained results were compared with the data mining approach. The input parameters are power, speed, pressure and stand-off distance (SOD) and the output responses of surface roughness, machining time and HAZ are considered. The set of experiments were constructed by using the Taguchi’s L9 method. The predicted closeness value of TOPSIS is greater than the GRA technique and the predominant factor observed is SOD followed by pressure, speed and power. In this work, C4.5-decision tree algorithm is applied to find the most influential parameter. It also represents the low-level knowledge of data set into high level knowledge (If-Then rules form). This investigation reveals that both TOPSIS and data mining suggested the SOD as predominant factor. This result of the optimized process parameters supports the laser assisted manufacturing industries by providing optimized output. Better results were obtained using the optimized set of parameters with the machining time, HAZ and surface roughness being 7.83 s, 0.09 mm and 0.86 $\mu$m, respectively. The results of this work would be very useful for automobiles and aircrafts industries where SS347 is highly employed.

TiO₂ film is prepared on the surface of Q235A substrate from an acid solution ($\mathrm{\text{pH}}=2$) to research its degradation of methylene blue organic pollutant in wastewater. The titanium oxysulfate is used as the titanium precursor to provide the source of titanium. The preparation of TiO₂ film is mainly a polymerization reaction of titanium oxysulfate, which makes Ti₂${\mathrm{\text{O}}}_5^{2+}$ and OH⁻ combine to produce [Ti₂O₅(OH)₂]_n precipitation deposited on the cathode surface by electrochemical reaction. TiO₂ film is formed after high temperature heating. The nitrate ion which derives from potassium nitrate in the electrolyte is reduced to hydroxide ion during the electrochemical reaction process, resulting in the formation of titanium compounds and titanium hydroxide. The TiO₂ film prepared from solution containing 0.2 mol/L KNO₃ has the best photocatalytic performance which can effectively degrade the methylene blue organic pollutant in wastewater. However, when the KNO₃ in the solution is 0.25 mol/L, excessive hydroxide ions inhibit the hydrolysis of titanium salts and accelerate the oxygen evolution resulting in the decrease of degradation efficiency.

In this paper, A356/B₄C composites were fabricated using the friction stir processing (FSP) method. The process’s input parameters, including rotational and transverse speed, were optimized using the response surface methodology (RSM). Three factors and three levels with nine experimental runs made up the design of the experiments. An analysis of variance (ANOVA) was employed to determine whether the constructed model was adequate at a 95% confidence level. This study found that transverse speed was the most critical variable affecting the composites’ silicon (Si) particle size, UTS, and force. The findings demonstrate that the Si particle size of the parent material and the dispersion quality of B₄C particles in the aluminum matrix are considerably influenced by the FSP factors, such as rotating speed and transverse speed. Second, tests for tensile strength were conducted to examine the composites’ mechanical properties. Then, using a specially designed fixture to measure force during the process, the forces on the tool, which play a decisive role in determining the tool’s life, were measured in different input parameters. The findings demonstrate that FSP transforms the mechanism of the fracture from brittle to extremely ductile in composites from the as-received metal.