Wear-related failures

In 1996, Chmell et al. [57] published a retrospective review of 143 patients implanted with Hylamer acetabular inserts after a follow-up period of at least 2 years. The index surgeries were performed between 1991 and 1992, and thus all of the Hylamer components in this study were gamma irradiated in air. Seventeen patients in the series were implanted with matched femoral components from the same manufacturer as the liner the remaining patients were implanted with mismatched femoral components from a different manufacturer. Overall, the revision rate due to excessive wear was 4.8%, with all six of the revisions occurring within the group of 126 patients with mismatched components. The authors judged the wear-related failure rate to be unacceptable and discontinued use of Hylamer acetabular inserts. 

Once the wear of the drillstring and a better control of stress concentration are achieved, it is possible to reduce corrosion-related failure of the drillstem. 

The scale models must be carefully designed. Failure to match the important dimensionless parameters will lead to erroneous simulation results. Modeling can be extended to particle convective heat transfer. Wear or erosion of in-bed surfaces can be qualitatively studied, although quantitative assessment requires the identification and simulation of additional wear-related parameters. 

Like other plastics, PP is not free from product failure during service. In a recent study [34], the main reasons for failure in plastics, in general, are stated in decreasing order of failures as environmental stress cracking, dynamic fatigue, static notch failure, creep related failure, chemical attack, UV attack, heat degradation and wear/abrasion. 

Maintenance costs can be minimized by, and are directly related to, good operation likewise, better operating results can be obtained when the equipment is under the control of a planned maintenance program. Improper operation of mechanical equipment can be as much or more the cause of its deterioration and failure as is actual, normal mechanical wear. Thus, operation and maintenance go together. 

Oil-related analysis encompasses a variety of physical and chemical tests such as viscosity, total acid number and particulate contamination. This is often extended to include the identification of wear debris, as an early warning of component failure, by either spectrographic... 

This crude distinction between adhesive and cohesive wear mechanisms is probably oversimplified in the sense that it neglects many aspects of the interactions between bulk deformation modes and interface rheology. It has, however, the merit of making a clear distinction between wear processes which can, to some extent, be related to known bulk failure properties and... 

Wear. Measurements of wear rates on the rollers and dies were attempted but due to frequent changes of dies and rolls, related to changes in production plans or equipment failures, there are no statistically verifiable data. One set of rollers, which was used with several dies, lasted 500 Mg. One die, which had been ground twice during use and used with several sets of new rolls (which might promote the wearing of both), had a life of about 1000 Mg. Removal of inorganic particles would decrease wear. 

Implant loosening invariably leads to clinical failure for a variety of reasons, which includes peri-prosthetic fracture of the implant or the bone adjacent to the implant. Numerous failure mechanisms limit the long-term success of endo-prosthetic implants including aseptic osteolysis, aseptic loosening, infection and implant instability (Holt et al., 2007). The key molecules of the host response at the protein level are chemokines, cytokines, nitric oxide metabolites and metallo-proteinases (Gallo et al., 2014). Aseptic osteolysis and subsequent implant failure occur because of a chronic inflammatory response to implant-derived wear particles. Despite many advances related to materials selection, and operation tool and techniques, aseptic osteolysis continues to limit implant longevity. 

Another approach to the detection of fluid film failure is the study of wear in relation to lubricant film thickness. Figure 6-18 shows observations by E. M. Landen [25] of the wear of two disks rubbing with velocities in the ratio 1 1.25. The film thicknesses were calculated from the operating parameters of the apparatus and elastohydrodynamic theory. As shown by curve D, for an oil film 65 nm thick wear ceases after a break-in period of one hour. When the oil film is only 20 nm... 

Device Failure. Every physical system has a finite life span or can be physically compromised. Mechanical or other failures of high-speed disk drives, memory, tape nnits, processors or other system components can arise from long-term wear or physical assault (fire, accident, flood, contamination, and so on). The probability of these events increases with time. Some of them (e.g., fire) are not directly related to continued operability, but others (e.g., component wear) are. 

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