The effect of external grit particle size on friction coefficients and grit embedment of brake friction material

Changes in friction and contact surfaces characteristics of a brake friction material during drag and stop mode test were investigated using a brake model tribo-tester. Scanning Electron Microscopy (SEM) was utilized to reveal the surface topography characteristics and analyze the external particle size effects on friction coefficients and grit embedment. Silica sand with three different particle sizes of 50-180 µm, 180-355 µm and 355-500 µm was used in this work. At higher disc sliding speed, results showed that small grit particles cause higher friction due to greater frequency of particles mixing and modifying the effective contact compared to bigger particles. Good friction stability was attributed to smaller particles size providing more stable contact by actively involved in building up and reducing the rate of changes of the effective contact area. Through SEM analysis, signs of formation and disintegration of contact plateaus correlated well with particle size and hence, suggesting the significant role of particle size as wearing mechanism. Grit embedment (GE) was greatly dependent on presence of compacted wear debris as most particles were found embedded into compacted wear debris. Total GE of 2.7% was observed for silica sand of 50-180 µm, 4.5% for 180-355 µm and 3.0% for 355-500 µm

Physical activity patterns and function 3 months after arthroscopic partial meniscectomy

Objectives: To compare physical activity levels, subject-reported function, and knee strength in 21 arthroscopic partial meniscectomy (APM) patients (age 45.7 (6.06) years, BMI 27.3 (5.96) female 60%) 3 months post-surgery with 21 healthy controls (age 43.6 (5.71) years, BMI 24.5(4.2) female 60%) matched at the cohort level for age, gender and BMI. Design: Case control study. Methods: Physical activity intensity, number of steps, and minutes spent in activity were objectively quantified using an accelerometer-based activity monitor worn for 7 days. The Knee Injury and Osteoarthritis Outcome Score (KOOS) and concentric quadriceps strength were used to evaluate function post-surgery. Differences in activity levels and functional outcomes between the APM and control participants were assessed using t-tests, while multiple linear regression was used to quantify the best predictors of physical activity. Results: APM patients engaged in a similar duration of activity to controls (469.0 (128.39) min vs. 497.1 (109.9) min), and take a similar number of steps per day (9227 (2977) vs. 10,383 (3501), but performed their activity at lower levels of intensity than controls. Time spent in moderate (r 2 = 0.19) and hard (r 2 = 0.145) intensity physical activity was best predicted by the Symptoms sub-scale of the KOOS for both controls and APM patients. Conclusions: APM patients participate in similar levels of activity at lower intensities, but with reduced activity at higher intensities which is related to the presence of symptoms of knee osteoarthritis

Effects of material and test parameters on the wear behavior of particulate filled composites Part 1: SiC-epoxy and 13; Gr-epoxy composites

Studies were carried out on a (RT) cure epoxy (LY556xFE;HY951) composite system13; comprising of silicon carbide (SiC) and graphite (Gr) particulates. Results showed that13; the wear resistance and coefficient of friction of both the composites increased with sliding13; distance and contact load (contact pressure) for the range of filler contents (5x2013;40% wt) considered.13; The Gr-composite exhibited its distinct (superior) tribological feature compared to the13; SiC-composite. A wear endurance index has been identified from the experimental data, to serve13; as a parameter to assess the long term wear life (residual wear life) of these composites

Nanosheets of MoS2-Oleylamine as Hybrid Filler for Self-Lubricating Polymer Composites: Thermal, Tribological, and Mechanical Properties

Polystyrene (PS)/MoS2@oleylamine composites were prepared by solvent blending method. Thermal, mechanical, and tribological properties of the resulting materials were analyzed as function of the filler concentration. SEM characterization for sample morphology as well as infrared spectroscopy and contact angle measurements were carried out in order to characterize the surface properties and the polymer-filler interactions. It was found that despite the poor compatibility between the MoS2@oleylamine nanosheets and the PS matrix, the resulting films present an almost homogeneous dispersion. The PS/MoS2@oleylamine composites showed enhanced thermal stability in comparison with neat PS. In addition, the introduction of MoS2@oleylamine strongly affects the mechanical properties of the PS matrix, reducing both the glass transition temperature and the elastic modulus. Finally, it was found that the MoS2@oleylamine was effective in both reducing friction and increasing wear of PS

Trabecular bone texture detected by plain radiography and variance orientation transform method is different between knees with and without cartilage defects

The objective of this work is to evaluate differences in trabecular bone (TB) texture between subjects with and without tibiofemoral cartilage defects using a variance orientation transform (VOT) method. A case-control study was performed in subjects without radiographic knee osteoarthritis (OA) (K&L grade 0.05) were found