The nature of the lubricating regime in total joint replacements is based on the ratio of...

 

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The nature of the lubricating regime in total joint replacements is based on the ratio of the lubricant film thickness and the roughness of the bearing surfaces. This is represented as the "lambda ratio". Lambda ratios from less than 1 to greater than 5 are considered to be descriptive of different lubrication regimes. You are working for a small manufacturer that produces metal, ceramic, and polyethylene bearings for hip joint replacements. Your colleague recently changed the manufacturing process, causing a small reduction (0.2 um) in the clearance between the femoral heads and acetabular liners. The original clearance was 0.3um and the new clearance is 0.1 um. Your boss asks you to consider how this change impacts the lubricant film thickness and the potential friction and wear of bearing couples from these materials. Q3.1. Based on your understanding of lubrication regimes, determine (with calculations) the lubrication regime for each bearing couple with the head/liner materials listed in table below. LABELS Head A1, A2 B1, B2 C1, C2 B3, B4 C3, C4 Ti-alloy ceramic CoCr alloy ceramic CoCr alloy Liner UHMWPE UHMWPE UHMWPE ceramic CoCr alloy Original clearance (0.3 um) Calculation Result Lubrication Regime New clearance (0.1 um) Calculation Result Lubrication Regime Q 3.2. Label the Stribeck curves (axes, main lubrication regimes separated by the dashed lines) and then identify the correct regime for each material pairing (place a label of the material pair on the curve in the proper regime). Stribeck Curve for Original Clearance (0.3 um) Stribeck Curve for New Clearance (0.1 um) HIN Q3.3. The Stribeck curve relates friction coefficient, viscosity, speed and load with lubrication regimes. Answer True or False : True False As sliding speed increases, hydrodynamic lubrication is more likely to develop As lubricant viscosity decreases, the friction coefficient decreases With increasing load, boundary lubrication is more likely to develop True False True False True False Hydrodynamic lubrication regime typically has the lowest coefficient of friction True False Lambda ratio < 1 indicates the surface roughness exceeds the fluid film thickness True False Boundary lubrication regime typically has the lowest coefficient of friction The nature of the lubricating regime in total joint replacements is based on the ratio of the lubricant film thickness and the roughness of the bearing surfaces. This is represented as the "lambda ratio". Lambda ratios from less than 1 to greater than 5 are considered to be descriptive of different lubrication regimes. You are working for a small manufacturer that produces metal, ceramic, and polyethylene bearings for hip joint replacements. Your colleague recently changed the manufacturing process, causing a small reduction (0.2 um) in the clearance between the femoral heads and acetabular liners. The original clearance was 0.3um and the new clearance is 0.1 um. Your boss asks you to consider how this change impacts the lubricant film thickness and the potential friction and wear of bearing couples from these materials. Q3.1. Based on your understanding of lubrication regimes, determine (with calculations) the lubrication regime for each bearing couple with the head/liner materials listed in table below. LABELS Head A1, A2 B1, B2 C1, C2 B3, B4 C3, C4 Ti-alloy ceramic CoCr alloy ceramic CoCr alloy Liner UHMWPE UHMWPE UHMWPE ceramic CoCr alloy Original clearance (0.3 um) Calculation Result Lubrication Regime New clearance (0.1 um) Calculation Result Lubrication Regime Q 3.2. Label the Stribeck curves (axes, main lubrication regimes separated by the dashed lines) and then identify the correct regime for each material pairing (place a label of the material pair on the curve in the proper regime). Stribeck Curve for Original Clearance (0.3 um) Stribeck Curve for New Clearance (0.1 um) HIN Q3.3. The Stribeck curve relates friction coefficient, viscosity, speed and load with lubrication regimes. Answer True or False : True False As sliding speed increases, hydrodynamic lubrication is more likely to develop As lubricant viscosity decreases, the friction coefficient decreases With increasing load, boundary lubrication is more likely to develop True False True False True False Hydrodynamic lubrication regime typically has the lowest coefficient of friction True False Lambda ratio < 1 indicates the surface roughness exceeds the fluid film thickness True False Boundary lubrication regime typically has the lowest coefficient of friction

Answer rating: 100% (QA)

TRUE as sliding Speed increases hydrodynamic lubrication is more likely to develop TRUE as lubri... View the full answer