Friction and Wear Pattern of Silica-Reinforced Styrene-Butadiene Rubber (SBR) in Sliding Contact with a Blade Indenter

This study investigated the friction and wear pattern of silica-reinforced Styrene-Butadiene Rubber (SBR) in sliding friction with a steel blade indenter. The experiments were conducted using a pin-on-disc tribometer at various applied loads and examined under dry and wet contact conditions. Analysis was focused on investigating the coefficient of friction and length of wear pattern spacing. Related to coefficient of friction identification, the abrasion theory was applied here. In addition, the stick-slip theory to identify the wear pattern spacing was also applied. Results of the experiments show that the overall coefficient of friction (COF) decreases along with the increasing applied loads. The COF in wet conditions is much lower at the beginning of sliding time than the COF in dry conditions. The wear pattern spacing increases with increasing loads. However, it seems that there is no significant difference in pattern spacing between the dry and wet contact condition. In general, the experimental results agree qualitatively with the analytical results.

Dry Machining of Inconel 825 Superalloys

The present work investigates application feasibility of PVD TiN/TiCN/TiN coated cermet and CVD Al2O3/TiCN coated SiAlON for dry machining of Inconel 825 superalloy. Machining performance is interpreted through cutting force magnitude, tool-tip temperature, and mechanisms of tool wear. Results are compared to that of CVD multi-layer TiN/TiCN/Al2O3/TiN coated WC-Co tool. It is evidenced that SiAlON tool generates lower cutting force but experiences higher tool-tip temperature than other two counterparts. Apart from abrasion and adhesion, carbide tool witnesses coating peeling and ploughing. In contrast, SiAlON tool suffers from inexorable chipping and notching. Wear pattern of cermet tool seems less severe than carbide and SiAlON. Chip's underside surface morphology appears relatively better in case of cermet tool.

Catastrophic failure of the Accolade I hip arthroplasty stem: a retrieval analysis study

Purpose: Modular Morse tapered femoral arthroplasty stems have been used for many years with great success and minimal complications. 1 stem, the Accolade by Stryker is noted to have increased failure when used in combination with LFIT V40 CoCr or the MITCH CoCr femoral heads. The failure has been in the form of corrosion, metallosis, fretting and trunnion fracture. This paper explores 10 cases with trunnion failure. Methods: A retrospective retrieval analysis of ten femoral stems retrieved at four different centres across Western Australia over a 3-year time frame. Inclusion criteria for this analysis included the use of Accolade 1 TMZF femoral stem plus either a MITCH or LFIT modular head. Results: 10 Accolade I (Stryker) stems were retrieved as part of the analysis, 6 with the LFIT V40 36-mm femoral head and 4 with a MITCH TRH femoral head. Average in situ time was 8.9 years. The hips were revised for either trunnion dislocation (6 cases) or trunnion fracture (4 cases). A characteristic destructive wear pattern of the femoral taper (trunnion) a “bird beak” appearance was present in all stems. This wear pattern created excessive movement and loosening resulting in a trunnion/head dislocation or brittle fracture of the trunnion. Conclusions: Catastrophic femoral neck fracture was likely due to a combination of material composition mismatch and mechanically assisted fretting corrosion at the head-neck junction leading to gross metallosis and failure. We suggest a recall on patients with an Accolade 1 stems in combination with a 36-mm or above LFIT or MITCH head, and for these patients to have clinical and radiological review.