TRIBOLOGY， Its Possibility and Impossibility

TRIBOLOGY， Its Possibility and Impossibility Yoshitsugu Kimura KAGAWA UNIVERSITY

→ Micro-, Nano-scale Tribology → Decrease in the Number of Tribologists Recent Changesin Social ConditionsAround TRIBOLOGY ・Heavy industry to IT-related Industry ・Restructuring in Industry

What is Expected of TRIBOLOGY and What Can We Do in the Future? ・Predictability ・Controllability ・Profitability

Predictability -Importance of accurate prediction ・An earthquake M7.0 in greater Tokyo area would cause economic losses of 41×1012JPYen. ・Economic losses due to stopping production for 1 day in the area would amount to 0.4×1012JPYen.

Accuracy of Prediction in Hydrodynamic Lubrication Depends upon …… • Factors to be included in analyses • Elastic deformation • Temperature / Pressure effects • Transition phenomena, etc. • Limitation on computation • Models expecting increase in • computation speed

Factors Impairing Accuracy of Prediction During Boundary/Dry Sliding ・Form and dimensional errors ・Surface irregularities ・Surface contamination ・Material contamination ・Changes in these with operation

→ Maintaining friction in certain ranges • → Maintaining wear rates • in certain ranges?? Controllability -Changes in the requirement for Tribology ・Reduction of friction alone ・Prevention of surface damage

Control of Friction -Control of normal load or friction coefficient Passive control ・Selecting Lubricants ・Mechanical Design ・Materials Active control ・Using active feedback elements or ……

→ Control of friction in hydro- • dynamic lubrication Possibility of Active Control With Liquid Crystal Lubricant By applying electric field …… ・Change in apparent viscosity ・Change in friction in boundary lubrication

Another Important Issue - Control of Deterioration ・Changes in form and dimension, micro-geometry, surface films, subsurface layers; contamination of lubricant, depletion of additives, additives, etc. ・Sensing and preventing, or compensating for, those changes

Profitability -Tribologists should show profitability of tribology, quantitatively and explicitly. ・How much cost can be cut by lowering friction coefficient by 0.01? Example : Fuel saving by friction reduction at piston-cylinder wall

Statistics (Japan, 1998) • No. of cars in use 71×106 • No. of gas cars in use 57×106 • Gasoline sales 57×106 kl • Total gasoline cost $57×109

Fuel Energy Consumption in a Car： EPAMode % 62%：Thermal 100 6%：Air pumping 80 3%：Piston-Cylnder 4%：Engine/Others 60 13%：Others 40 12%： Wheels 20 0

Power Loss Analysis Between Piston and Cylinder Wall • Friction coefficient • 0.05 for Piston rings • 0.03 for Piston skirt • 0.042 between Piston and • Cylinder Wall • Distribution of Mechanical loss • 60% for Piston rings • 40% for Piston skirt

Possible Friction Reduction 30%：coating on rings 20%：barrel-shaped piston skirts →26% Reduction of Average Friction Coefficient ・0.01 of Decrease of Friction Coefficient ・445×103kL of Fuel or $445×106 Cost Saving

Again, What is Expected of TRIBOLOGY and What Can We Do in the Future? ・Predictability ・Controllability ・Profitability

Thank You for Your Attention! Tokyo Kagawa

TRIBOLOGY， Its Possibility and Impossibility