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Mouthwashes are widely utilised for their affordability, ease of use and oral hygiene benefits. However, indiscriminate use of these over-the-counter mouthwashes can cause morphological changes in enamel and cementum, compromising tooth structure. This study evaluates the change in the surface roughness, surface hardness and colour of enamel and cementum after the use of various mouthwashes using surface profilometry, Vickers hardness tester and spectrophotometry, respectively, for 7 and 15 days. Five common mouthwashes, namely, Colgate Plax, Listerine, Himalaya, Chlorhexidine and warm saline water were tested on 10 extracted permanent teeth in each group. Teeth were sectioned longitudinally from crown to root, embedded in acrylic and examined for defects. Baseline values for colour, hardness and roughness were recorded before immersing the samples in mouthwash as per the manufacturers' instructions. Postimmersion measurements were taken at specified intervals. A significant decrease in enamel hardness after 7 days with chlorhexidine (108.28 ± 85.17), Himalaya (104.02 ± 94.22), warm saline (85.42 ± 70.9) and Listerine (55.32 ± 83.68) was observed, but not with Colgate Plax. Cementum hardness decreased over 15 days but was not statistically significant. The greatest increase in surface roughness was seen in saline followed by Himalaya whereas the decrease was seen in chlorhexidine and Colgate Plax at the end of 7 days. Listerine caused the highest colour change in enamel. Since trends towards decreased hardness and increased roughness were noted, long-term usage could pose clinical concerns. Warm saline showed subtle yet significant changes, indicating the need for further investigation. These findings underscore the importance of regulating mouthwash use and recommending it only when the benefits outweigh the risks.

Knight, J. and Burningham, H., 2020. What controls bedrock shore platform hardness? A field study from South Africa. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 537-541. Coconut Creek (Florida), ISSN 0749-0208. Bedrock shore platforms are common features along the Indian Ocean coast of South Africa but their properties and controls have not been well reported. This study presents high-resolution evidence for rock surface properties and hardness values from a sandstone platform at Morgan's Bay (Eastern Cape, South Africa) where the relative roles of environmental versus lithological factors on bedrock surface hardness can be evaluated. Results show that there is very little correspondence between rock hardness and either absolute platform elevation or distance from low water position of sea level. Two contrasting conceptual models are proposed to explain these results. One model proposes that a uniform geological control dominates, despite variations in environmental forcing. The alternative model considers that environmental controls such as waves and subaerial weathering do not significantly vary over the platform, despite any differences in platform relief and microenvironment. These different models can be used as testable hypotheses to evaluate the relative controls on, and thus interpretations of, measurements of rock surface hardness on shore platforms.

Interest in the construction of prefabricated ice rink for international competition has increased in recent years, where the ice sheet is directly supported by soft thermal insulation materials. However, bending failure in the ice sheets for these rinks is highly possible because of different compression and tension behaviors. Moreover, the mechanical behaviors of the artificial ice produced layer-by-layer in rinks remain unclear. Therefore, microstructure observations, hardness tests, and three-point bending tests were conducted in this study to better understand artificial ice. First, the crystal structures were obtained through observations in both the vertical and horizontal directions. Then, the hardness of the ice surface at different temperatures, water qualities, ice-making methods, and surrounding environmental conditions was measured using the Shore hardness apparatus. Finally, systematic three-point bending tests on 80 effective ice specimens under a wide range of loading and ice-making parameters were performed. The results show that artificial ice is a typical kind of columnar ice with smaller grain sizes at lower surfaces. The ice surface hardness, roughly normally distributed, was mainly affected by temperature and ice-making mode. Moreover, it was found that all the test ice beam exhibited brittle fracture, and the flexural strength ranged from 0.84 to 2.47 MPa, with the maximum average at a strain rate of 1 × 10 –4  s –1 . Based on these test results, empirical functions for the effects of the investigated parameters on the flexural strength and effective modulus were developed. Also, the relationships between flexural and tensile strength for artificial ice were established using Weibull law and the coupled criterion. In addition, the linear regression model was established and verified using different prediction methods to predict the ice flexural behavior in practical rinks based on the measured hardness in a simple, reliable, and nondestructive way. The current experiment and analysis are beneficial for the design, operation and maintenance of prefabricated ice rinks.

Rock's surface micro-topography and geotechnical properties' limits are expected to be altered on weathering progress to a new form(s) and limits, respectively. The quantification of weathering damage for a given rock is of value e.g. to compute weathering rate, weathering intensity and rock's durability to weathering processes and to take a decision regarding restoration urgency. The current study aims to examine the variation/constancy of micro-topography and geotechnical properties’ limits of the Triassic sandstone constituting well-aged wall, at Aachen city, on weathering progress over short duration (12 years of investigation from 2007 to 2019). The Equotip hardness tester and micro-erosion meter are tools used for micro-topographic and rock's surface hardness investigations on one hand, and the mercury intrusion porosimetry has been used for measuring rock's pore size distribution and salt susceptibility on the other hand. These tools are accurate, numerical, comprehensive, easily applicable and preferable particularly for ancient buildings and archaeological sites where sampling is not recommended or prohibited. The wall side under consideration has been selected as its constructional blocks present a wide spectrum of weathering forms as well as rock's surface micro-topography (over 12 years of investigation) through increasing the weathering forms' dimensions and/or creation of new weathering forms. The net result of the current study indicated a noticeable variation in stone's micro-topography on weathering progress, the rock's stone surface hardness highly controls rock's weathering susceptibility and no clear relation can be noted between stone's surface roughness and its susceptibility. The pore size distribution is the most controlling parameter for rock's weathering susceptibility.

A small series of ring compression tests were performed on BS970:708M40 alloy steel. The samples were tested using a 2-factor temperature variable, and a 4-factor lubricant variable, as the design parameters. Two differing soak temperatures were used, namely 1030 °C and 1300 °C respectively. The lubricants applied at the billet to tooling interface were synthetic water–based, graphite water–based, graphite and molybdenum disulphide viscous grease, and finally, unlubricated samples were tested. The ring compression tests were performed using a traditional drop forging hammer and induction heating to minimise any unintentional process variability. The impact that the two varying process parameters have upon the compression sample was then assessed by measuring each sample’s surface hardness and surface roughness prior to and post forging with fully calibrated equipment. It was demonstrated that the higher soak temperature of 1300 °C yielded a lower surface hardness value and higher surface roughness than the lower soak temperature, 1030 °C. The two water-based lubricants offered negligible change in results compared with the unlubricated forging, strongly suggesting that the lubricants were evaporated off the surface prior to forging. However, the results from the graphite–molybdenum disulphate grease do indicate in particular higher surface roughness than other lubricants, and a non-symmetric distortion pattern.

The present study focuses on revolutionizing SS-304 through microwave-assisted cladding of Ni-SiO2 composite coatings, aiming to enhance wear resistance and surface hardness properties. Meticulous preparation steps ensure effective deposition of a Ni and 15% SiO2 particle mixture onto SS-304 substrates. Thorough cleaning and preheating eliminate contaminants and moisture content, crucial for preventing coating defects. Maintaining material-specific skin depth and utilizing microwave hybrid heating ensure precise and uniform coating formation. Microwave-assisted cladding exhibits a uniform distribution of Ni and SiO2 particles across the substrate surface, crucial for consistent coating thickness and mechanical property enhancement. The surface hardness of SS-304 increases significantly by approximately 36.89% post-cladding, highlighting improved wear resistance. Tribological testing reveals favorable performance, with a wear rate of 0.0026 mm³/m and a coefficient of friction of 0.193. These findings underscore the efficacy of microwave-assisted cladding in enhancing the mechanical properties of SS-304, offering valuable insights for applications requiring enhanced durability and frictional performance.

Purpose The CL60 steel wheels of subway vehicles operating on specific lines require frequent refurbishment due to rapid wear and tear. Considering this issue, MoS2-based and graphite-based solid lubricants are used to reduce the wear rate of subway wheels and extend their service life. Design/methodology/approach Under laboratory conditions, the effect of MoS2-based and graphite-based solid lubricants on the friction and wear performance of subway wheels and rails was evaluated using a modified GPM-60 wear testing machine. Findings Under laboratory conditions, MoS2-based solid lubricants have the best effect in reducing wheel/rail wear, compared to the control group without lubrication, at 2 × 105 revolutions, the total wheel-rail wear decreased by 95.07%. However, when three types of solid lubricants are used separately, the hardness evolution of the wheel-rail contact surface exhibits different characteristics. Practical implications The research results provide important support for improving the lifespan of wheel and rail, extending the service cycle of wheel and rail, reducing the operating costs of subway systems, improving the safety of subway systems and providing wear reduction maintenance for other high wear mechanical components. Originality/value The experiment was conducted through the design and modification of a GPM-60 testing machine for wear testing. The experiment simulated the wheel-rail contact situation under actual subway operation and evaluated the effects of three different solid lubricants, MoS2-based and graphite-based, on the wear performance and surface hardening evolution of subway wheel-rail.

Recently, the surfaces of concrete structures are impregnated to protect them against the environment in order to increase their durability. It is still not known how the use of these agents affects the near-surface hardness of concrete. This is especially important for experts who use the near-surface hardness of concrete for estimating its compressive strength. The impregnation agents are colorless and, thus, without knowledge of their use, mistakes can be made when testing the surface hardness of concrete. This paper presents the results of investigations concerning the impact of impregnation on the subsurface hardness concrete measured using a Schmidt hammer. For this research, samples of cement paste with a water–cement ratio of 0.4 and 0.5 were used. The samples were impregnated with one, two, and three layers of two different agents. The first agent has been made based on silanes and siloxanes and the second agent has been made based on based on polymers. The obtained research results allow for the conclusion that impregnation affects the near-surface hardness of concrete. This research highlights the fact that a lack of knowledge about the applied impregnation of concrete when testing its near-surface hardness, which is then translated into its compressive strength, can lead to serious mistakes.

This study presents a novel method for estimating the surface integrity of end-milled workpieces. It is well known that the mechanical properties of machined surfaces in cutting affect the quality of the final product. In particular, hardness and residual stress often require strict control; however, nondestructive inspection remains a challenge. This study proposes a method to estimate the hardness and residual stress of end-milled surfaces by analyzing cutting forces and images of the tool during machining to obtain approximate temperature and stress distributions. These state quantities are highly correlated with the dislocation density and its distribution on the machined surface, which in turn is strongly correlated with residual stress and surface hardness. Despite this strong correlation, few research studies have been conducted on the topic. In the proposed method, cutting forces, measured by a dynamometer, are analyzed to estimate the specific cutting forces and edge force coefficients. Simultaneously, the flank wear width is recorded using an image-based on-machine measuring device installed in the machine tool. From this information, the average stresses at the primary and tertiary cutting zones are estimated, while the cutting temperature in the primary cutting zone is roughly estimated by considering the traditional shear-angle prediction theory. Using these estimations, hardness and residual stress are calculated based on a simple linear regression model. Parameter identification for the model is performed based on measured hardness and residual stress in end-milling experiments. The model was validated against experimental measurements, which showed that the proposed method can accurately estimate hardness and residual stress, although it was observed that the selection of explanatory variables has a significant effect on accuracy.

The paper deals with the comparison of surface hardness and porosity of stainless steel 316L (1.4404) produced by additive technology (SLM) and cold rolled steel. The subject of the paper is a comparison of two sets of samples where the first set of samples was made on a Renishaw AM400 with a laser output of 200 W and 400 W. In each set of samples, were the samples without heat-treated and heat-treated by annealing. Measurement of porosity and surface hardness were performed on all samples. The surface hardness of the material was evaluated by a static test according to Brinell CSN EN 10003-1. The porosity measurement was performed by the optical method. The measured values were compared with the reference material, which was cold-rolled steel, in which both the porosity and the hardness of the surface were measured.