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[Display omitted] Contact angle and sliding angle measurements are widely used to characterize superhydrophobic surfaces because of the simplicity and accessibility of the technique. We hypothesize that dynamic friction measurements, with increasing pre-loads, between a water drop and a superhydrophobic surface is more accurate because this technique is less influenced by local surface inhomogeneities and temporal surface changes. A water drop, held by a ring probe which is connected to a dual-axis force sensor, is sheared against a superhydrophobic surface while maintaining a constant preload. From this force-based technique, static and kinetic friction forces measurements are used to characterize the wetting properties of the superhydrophobic surfaces. Furthermore, by applying increased pre-loads to the water drop while shearing, the critical load at which the drop transitions from the Cassie-Baxter to Wenzel state is also measured. The force-based technique predicts sliding angles with reduced standard deviations (between 56 and 64%) compared to conventional optical-based measurements. Kinetic friction force measurements show a higher accuracy (between 35 and 80%) compared to static friction force measurements in characterizing the wetting properties of superhydrophobic surfaces. The critical loads for the Cassie-Baxter to Wenzel state transition allows for stability characterization between seemingly similar superhydrophobic surfaces. [ABSTRACT FROM AUTHOR]

Mechanical products are becoming more diversified with the continuous development of precision processing and materials technologies. The friction force generated by the O-ring seal in a hydraulic cylinder was once considered redundant. However, its utilization has recently been proposed. The hardness of the O-ring and the inner diameter of its groove directly affect the normal pressure between the O-ring and the inner wall of the cylinder, thereby affecting the friction behavior. In order to explore this friction behavior, a strain-based friction force measurement system is developed in this study, and the steady-state and dynamic friction values under different working conditions are studied and discussed in depth. This research on the friction behavior in the cylinder provides a theoretical basis for more convenient design and utilization of the friction force generated between the O-ring and the inner wall of the cylinder. [ABSTRACT FROM AUTHOR]

Double-plane grinding plays an important role in the processing of high-precision flat parts. A double-side autonomous grinding (DSAG) method was proposed and investigated to improve the uniformity of the abrasive grains of the grinding disc on the surface of the workpiece by releasing the constraints on the workpiece. In DSAG, the main driving force of workpiece movement comes from the friction force generated by the relative movement of the upper and lower grinding pads. Experiment of dynamic friction coefficient measurement between workpiece and grinding plates is carried out to take into account the differences of dynamic friction factor under different speed and force conditions. A mathematical model of the relative motion trajectory between the particles on the upper and lower plate and the workpiece is established based on kinematics and dynamics theories. Then, the effects of the linkage mode of the lower plate, grinding pressure, and speed ratio of the upper and lower plates on the frequency and direction uniformity of the grinding trajectory of the abrasive particles on the workpiece surface are simulated and analyzed. Aiming at the trajectory uniformity, the grinding parameters are optimized through orthogonal experiment and verified on the independently developed experimental platform. The flatness and roughness of the workpiece are detected. The results show that the DSAG performs well in obtaining the better roughness and flatness of the workpiece surface than that of planetary grinding. [ABSTRACT FROM AUTHOR]

Objective: Drawing parallels from rheotribology can be used to develop a robust instrumental protocol for non‐subjective characterization, product development and design of topical dosage forms with desired sensory attributes. However, instrumental characterization of cosmetic products can be influenced by the measurement protocol, thixotropy, flow anomalies like shear banding or wall slip and nature of the film formed on the skin surface. In this study, we evaluated the influence of above parameters on the instrumental sensory evaluation of 12 topical formulations of different galenic forms. Methods: Oscillatory strain sweep measurements (SAOS and LAOS) were performed to investigate the influence of frequency and wall slip on the material parameters. The textural attributes at different consumer touchpoints were evaluated by accounting time‐dependent simulation of viscoelastic flow. Further, the influence of film thickness and sample drying on the tactile properties of the topical formulations were studied on a non‐biological skin model using a sliding probe tribometer. Results: The study shows that the flow properties of the semi‐solid formulations depend on the timescale of the problem. A few formulations exhibited wall slip to varying degrees in the linear viscoelastic regime where the behaviour was found not to be characteristic of a particular topical dosage form. The material functions obtained from the Lissajous plots suggest that the non‐linear flow behaviour of different galenic forms is least influenced by the boundary conditions imposed by the measurement geometry. The results were statistically analysed using principal component analysis where the attributes used for discriminating skin creams during pick up and rub out are found to be closely associated with non‐linear rheology. The friction coefficient exhibited speed dependence where it formed different parametric group with rheological data depending on the lubrication regime. Conclusion: The study highlights that correlations are possible amongst rheological, tribological and instrumental textural analysis data, which can act an impetus for the development of models to predict attributes that drive perception at different consumer touchpoints. However, the choice of instrumental settings, anomalies associated with rheological measurements and friction dependence on a number of parameters can influence the model prediction. [ABSTRACT FROM AUTHOR]

Measuring friction on the human body is challenging on areas where the surface of the skin is curved. Handheld devices for measuring friction may make it easier to rapidly measure from hard-to-reach areas, however, the orientation of the probe relative to the surface is often sub-optimal to reliably measure the normal force. Here, the friction on the surfaces of a mannequin and a human body are measured and corrected using a curvature correction technique. This is accomplished by accounting for the shape of the measurement surface and the orientation of the measurement device relative to that surface. Two strategies for constructing the surface shape of the measurement surface are compared. [Display omitted] • Implement a curved surface correction method in 3D with a linear sliding handheld tribometer. • Test methods for capturing the 3D curved surface shape for the surface correction method. • Measure sliding friction on a human body. [ABSTRACT FROM AUTHOR]

This study conducted friction experiments of three elastomer block materials on ice (low pressure injection of polyurethane (PU), injection moulding of a thermoplastic polyurethane (TPU) and vulcanization of rubber (RU)), with a linear tribometer operating under four different ambient air temperatures (−10 to 0 °C) and six different sliding velocities (0.3–5 m/s). At low temperatures (−10 °C and −5 °C), the RU material showed the highest dynamic and static friction. However, at high temperatures (−2 °C and 0 °C) the PU revealed the highest dynamic friction and highest static friction at 0 °C. We discuss the physical phenomena's of elastomer friction on ice and in relation to the application of footwear slipping on ice. • Slipping accidents simulated by biofidelic friction testing of elastomers on ice. • PU outsole material on warm ice provides higher static friction coefficient compared to TPU and RU materials. • RU outsole material revealed higher dynamic friction coefficient on cold (−10 to 5 °C) ice compared to TPU and PU materials. • Hybrid outsole constructions combining materials, composites and design solutions may be able to accommodate slip resistance. [ABSTRACT FROM AUTHOR]

Frictional characteristics of an iron-based mixture were studied using a specifically designed friction test bench allowing (after prior compaction) the measurement of the friction coefficient during the sliding of a compact on a slab simulating the die surface. Temperature and sliding velocity were controlled. An experimental campaign was conducted with four high-performance lubricants and a conventional EBS wax, based on a single FL-4400 mix formulation. The experimental parameters included: mix temperatures from 40 to 80 °C; density of 7.20 g ⋅ cm−3; normal pressure of 244 MPa; sliding distance 80 mm; sliding velocity 20 mm ⋅ s−1. The analyses focused on the evolution of the friction coefficient and the compact's surface degradation. Two methods were compared: single testing with slab cleaning between each test, and repeated testing. After multiple repetitions, a steady state was established with a sliding distance beyond which degradation became critical. The degradation depended on the lubricant and experimental conditions. The difference between lubricants became more obvious, some of them proving an enhanced ability to create long-range lubrication. This study aims at better understanding how the friction coefficient evolves during the ejection of a production part. [Display omitted] • High-performance lubricants increase the sliding distance before surface degradation. • The maximum sliding distance before degradation was estimated using a friction test. • Repeated testing improves the quality and repeatability of friction measurements. • Lubrication properties evolve with the number of compaction cycles. [ABSTRACT FROM AUTHOR]

The tribological interaction between patterned running surfaces and an ice track was investigated. The friction coefficient was analyzed according to the patterned running surface type, ambient temperature, and rotational track velocity. The results were analyzed based on the structural characteristics of the patterned running surface in terms of average height and skewness. Generation of the water layer was visualized using transparent replicas of the patterned running surfaces. The water layer ratio was then calculated and compared with the friction coefficient. We found that the water layer either functioned as a lubricant or offered frictional resistance depending on the water layer ratio and the type of patterned running surfaces as the lubricating friction regime changed. • The friction force between the commercially available patterned running surfaces of jumping ski and ice is measured. • The water layer is visualized to elucidate the effect of the surface patterns on ice friction coefficient. • The lubricating friction regime varies by surface patterns , resulting either increases or decreases frictional drag. [ABSTRACT FROM AUTHOR]

In situ measurement of frictional properties, particularly of human skin, is challenging. A major challenge is that the measured surface may be curved and oriented arbitrarily relative to the measurement device, making it difficult to obtain accurate and reliable friction estimates. Here we propose a method to simultaneously estimate the orientation of the surface during friction measurements, using a custom-made hand-held tribometer. The method accounts for the position and orientation of the tribometer relative to the shape of the measured surface. Our simple calibration method allows lightweight tribometers to be built with cheaper materials like plastic, without sacrificing accuracy. [Display omitted] • Propose a general method to measure force data on curved surfaces for sliding contacts and friction analysis. • Implement this curve correction method with a linear sliding handheld tribometer. • Describe the importance of carefully testing and calibrating the outputs of lightweight devices that may have low flexural rigidity. [ABSTRACT FROM AUTHOR]

Low-speed marine diesel engines are widely used as propulsion power equipment on ocean-going merchant ships. There are three important sliding friction pairs in the engine: piston assembly-cylinder liner, piston rod-stuffing box, and crosshead slipper-guide. They greatly influence the mechanical efficiency and stability of the engine. However, there is no effective method to measure the friction of the three friction pairs so far, which limits the improvement of tribological performance and the reduction of fuel consumption in low-speed marine diesel engines. In the current study, an indirect measurement method is presented and the measurement of the friction force under fired conditions is realized for the first time. By comparing the experimental results of friction force with the model-based numerical results, it is found that they are in good agreement. The difference between the numerical and experimental maximum friction force is less than 5%. Both theory and experiments show that the friction force reaches the maximum after the top dead center, which is about one-tenth of the gas force. The work of this paper is expected to provide an effective tool for evaluating the tribological performance of marine diesel engines. [Display omitted] [ABSTRACT FROM AUTHOR]

Finger pad friction varies significantly between individuals due to personal differences and environmental effects. For this reason, comparison of the absolute friction values becomes non-informative and is rarely reported in literature. This work investigates whether friction data can be normalised to correlate between individuals. A set of textured samples were tested by 10 volunteers in dry sliding conditions with a range of normal loads up to 4 N. A reference smooth sample was used for each participant to normalise the dataset. The proposed approach allows to eliminate one of the unknown parameters, e.g., finger pad ridge contact area function, and discuss the data with respect to other variables. • Friction measurements from 10 volunteers, 4 samples and 9 normal loads were analysed to propose a normalisation method. • Normalisation reduces one of the personal variables and allows friction comparison between individuals. • Friction measurements normalised by a reference represent a change of contact area fraction with normal load. • Volunteers showed similar fractions of real contact area despite differences in skin properties and friction. [ABSTRACT FROM AUTHOR]