Analysis of traction curve in linear region considering volume viscoelasticity

Measurements of the gradient in the linear region of traction curve, where the effects of heat generation and nonlinearity of shear viscosity can be n eglected were made for two kinds of synthetic oils, DOP and 5P4E, using a t raction tester improved to a precision less than 0.01 percent in slip ratio . The measured results were compared with the theoretical results based on a viscoelastic model for shear stress and on an elastic model for compressi bility using primary data of the rheological properties which were obtained not by means of traction test; they were markedly less than the theoretica l results under low speed for both oils and also under high speed for DOP. A new analysis of the traction was performed considering volume viscoelasti city for compressibility which relates shear viscoelasticity under high pre ssure. The theoretical results agree fairly with the measured results.