TRIBOLOGY ， Its Possibility and Impossibility

Yoshitsugu Kimura KAGAWA UNIVERSITY

・ Heavy industry to IT-related Industry

・ Restructuring in Industry

Recent Changesin Social ConditionsAround TRIBOLOGY

→ Micro-, Nano-scale Tribology

→ Decrease in the Number of Tribologists

What is Expected of TRIBOLOGY and What Can We Doin the Future?

・ Predictability

・ Controllability

・ Profitability

Predictability -Importance of accurate prediction

・ An earthquake M7.0 in greater Tokyo area would cause economic losses of 41×1012 JPYen.

・ Economic losses due to stopping production for 1 day in the area would amount to 0.4×1012 JPYen.

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

Controllability-Changesin the requirement for Tribology

・ Reduction of friction alone

・ Prevention of surface damage

→ Maintaining friction in certain ranges

→ Maintaining wear rates in certain ranges??

Control of Friction-Control of normal load or friction coefficient

Passive control

Active control

・ Selecting Lubricants・ Mechanical Design・ Materials

・ Using active feedback elements or ……

Possibility of Active Control With Liquid Crystal Lubricant

By applying electric field ……

・ Change in apparent viscosity

・ Change in friction in boundary lubrication

→ Control of friction in hydro- dynamic 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

-Tribologists should show profitability of tribology, quantitatively and explicitly.

Profitability

・ How much cost can be cut by lowering friction coefficient by 0.01?

Example : Fuel saving by friction reduction at piston-cylinder wall

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

Statistics (Japan, 1998)

Fuel Energy Consumptionin a Car ： EPA Mode

62% ： Thermal6% ： Air pumping

3% ： Piston-Cylnder4% ： Engine/Others

13% ： Others12% ：Wheels

100

80

60

40

20

0

%

Power Loss Analysis Between Piston and Cylinder Wall

Friction coefficient•0.05 for Piston rings•0.03 for Piston skirt

Distribution of Mechanical loss•60% for Piston rings•40% for Piston skirt

•0.042 between Piston and Cylinder Wall

Possible Friction Reduction

・ 0.01 of Decrease of Friction Coefficient・ 445×103kL of Fuel or $445×106 Cost Saving

30% ： coating on rings20% ： barrel-shaped piston skirts

→26% Reduction of Average Friction Coefficient

Again,What is Expected of TRIBOLOGY and What Can We Do in the Future?

・ Predictability

・ Controllability

・ Profitability

Thank Youfor Your Attention!

Tokyo

Kagawa