Wear performance/rates

From the standpoint of use in textiles, cotton is rated excellent for hand (general feel, softness, drape), pilling resistance, and stability to repeated launderings. Cotton is rated good for abrasion resistance, strength, wash and wear performance, and wrinkle resistance. Resisiance to sunlight is rated only fair. Pressed-erease retention is rated poor. Safe-ironing temperature for most coiton fabrics is 425°F (2I9°C>. 

Xue et al. (16) observed that the wear rate of the UHMWPE/HDPE blend can be significantly reduced by adding CNTs, which can be correlated with an increase of the Young s modulus. The addition of 0.5 wt% CNTs to the UHMWPE/HDPE blend caused about 50% reduction of the wear rate, which is shown in Table 5.7. Besides, the composites reinforced with untreated CNTs had a better wear performance than the composites with pre-treated CNTs and the graphical... 

Chamley and coworkers first developed radiographic techniques for evaluating the wear rate of UHMWPE acetabular components in patients. In 1973, Chamley and Cupic reported on the long-term wear performance in the first cohort of patients to receive a UHMWPE component between November 1962 and December 1963. During this time period, 170 patients received a cemented LFA with an UHMWPE component a total of 185 acetabular cups were implanted. Because of the elderly population originally implanted with the components, many had died or were too infirm to travel to the clinic for followup examination (more than two-thirds of the patients were older than 60 years of age at the time of implantation). Thus, only 106 out of the original 185 UHMWPE cups could still be evaluated after 9 or 10 years of implantation. The complications for this series included a 4-6% rate of infection, 1-2% rate of mechanical loosening, and a 2% incidence of late dislocation. 

Artificial disc replacemenfs have also been developed that do not incorporate UHMWPE components. These have a MOM bearing system, which presumably is to reduce the amoimt of wear produced. This once again shows the trend of borrowing concepfs from fhe TJR world and applying them to TDRs. In addition, for TDR designs, fhe wear performance of CoCr has been evaluated and was shown to have less wear rate in comparison with titanium alloy designs (Hellier, Hedman, and Kostuik 1992). 

The performance rate is defined as the actual output divided with the theoretical output. It is important that the theoretical output is frequently updated as modifications are being done. If the same value for theoretical output is used year after year, the performance rate will exceed 100%. Another important aspect is never to reduce the theoretical output as a result of wear and aging. The costs of removing effects from wear of aging are usually lower than the costs of lost production (Koch 2007). 

The degree of wear/friction improvement depends on the particular plastic to which the PTFE is being added [41], As examples, the above referenced study showed that the addition of 15% low MW PTFE to a 6/6 polyamide, a polyacetal resin, and a polycarbonate reduced the specific wear rates by 97%, 46%, and 97%, respectively. The dynamic friction coefficients were reduced by 76%, 48% and 97%, respectively. Although these are reasonable comparisons, wear and friction performance can depend on the exact contact conditions such as velocity, pressure, and countersurface composition. Commercial compounds of thermoplastics with PIFE will vary depending on the application requirements but an addition level of 15-20% is usually considered optimum for the best wear performance. 

The most studied anti-wear material modified by whiskers is PEEK. Wang et al." compared the performances of PEEK before and after modification with potassium titanate whiskers. The friction and wear performances of the latter showed obvious improvement over the former. Under 300 N, the wear resistance of the latter increases 2.64 and 2.11 times than the former, respectively. In addition, calcium carbonate whiskers have an excellent anti-friction effect on PEEK composite material. When the whisker content is less than 15%, the wear rate of the material decreases dramatically. The wear rate of the... 

Figures 12 and 13 depict the wear performance of nanocomposites filled with AljOj (13 nm) and TiOj (300 nm), respectively. The nanoparticle content was varied between 0 and 10 vol.%. The results were obtained from unlubricated sliding wear experiments conducted on a block-on-ring apparatus. In this case, the specimens run against a carbon steel ring at constant pressure and rotating speed (e.g., 1 MPa, 1 m/s). From the sample weight loss one can calculate the specific wear rate as follows...

In this study, the application of the electrostatic sensing technique has been applied to detect wear of hybrid contacts under lubricated pure sliding conditions. The main objective was to seek correlation between the specific wear rates of the contact materials and the electrostatic charge levels. The other objective was to compare the wear performance of a range of advanced bearing steels against silicon nitride under lubricated sliding tests on the laboratory pin-on-disc tribometer. 

ZDDP) acts to protect the bare surface against wear. The effectiveness of ZDDP as an anti-wear additive is strongly dependant on the test conditions. As shown by So et al. [2], under low loads the wear performance was improved by ZDDP. However, at higher loads, for steel on steel contacts, the wear rate can actually be increased through ZDDP additives [3]. 

Poljmier composites, especially those which are hybrid in nature, have good wear performance and such a class of materials is very suited for both low fidction (bearings, gears) and high friction (footwear, tires, brakes, and fidction drives) applications whilst keeping the wear rate to a minimum. Finally, polymer composites often do not work well in lubricated or water environments due to the problem of the weakening of the interface between the fillers and the matrix and removal of the transfer layer in the presence of a fluid. 

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