抄録
In many cases, the viscosity of lubricating oil between friction surfaces is increased by the pressure. Its characteristics are defined with viscosity-pressure coefficient. The viscosity-pressure coefficient is estimated by measuring the density variation in the high-pressure vessel to determine the bulk modulus of elasticity. On the other hand, being similar to the high pressure condition, the oil viscosity under low temperature state is increased because the molecular motion of lubricating oil is restrained and the degree of freedom is lost. Therefore, packing state of the molecules at low temperature can be considered to be similar to the state of the lubricating oil under high pressure condition. This paper derived the bulk modulus of elasticity at low temperature from measuring the sonic velocity using a sing-around method.
