Technikatörténeti szemle 10. (1978)
A MÉRÉS ÉS A MÉRTÉKEK AZ EMBER MŰVELŐDÉSÉBEN című konferencián Budapesten, 1976. április 27–30-án elhangzott előadások II. - Tálos Gy.: A reológiai mérési módszerek fejlődésének története Newtontól napjainkig
Boltzmann's activities had brought a decisive change in the development of the rheology. They were the pioneers of the viscoelastic theory, described the elastic aftereffect, the stress-relaxation. They dealt with not only fluids, but with gases and solids too and so they were the first, who began to proclaim the principles, according to which the structure of the materials they connected with flow their behaviours. Amongst the rheologists of the second part of the century St. Venant was the first about the plastic flow and Reynolds dealt with the theory of lubrication, Reynolds number —which determines the stability criterion of the steady laminar flow — is called after him. I have to mention here, that Taylor dealt with the term of turbulence for Newtonian fluids in rotational viscometers. At the beginning of the 20. century, the research of the rheology of colloid systems began with such materials (e.g. gelatin and gum arabic, pitch and asphalts), which were non-Newtonian and for which steady laminar flow could have been achieved in convenient instruments constructed or redesigned for them. In this field, Schwedoff's and Hatschek's works were the most important. At the same time to characterize such materials, the researchers began to set up ,,flow model"-s consisting of mechanical elements, in 1902 Poynting and Thompson ereated the first one at studying the elastic after-effect in glass fibres. Many activities aimed at corrections or modifications of the recognized laws according to the boundary conditions of the measuring devices. In 1912 Searle made a viscometer for high viscosity liquids. In 1913 Ostwald stated that studying colloid state, the viscosity is of great significance. Ostwald designed the simple U-tube capillary viscometer, which was named after him and was the origin of all the present capillary viscometers. From the middle of the 10-s at about to the middle of the 20-s Bingham and his coworkers (Green, Young and Buckingham) declared the laws of plastic flow, disclosed the term for yield value and defined the plastic flow in different types of viscometers. From the beginning of the 20-s the activity of Freundlich and his coworkers gave a great impetus to the researches of the colloids (disperse systems, gels and sols.) From the years of the 30-s, hundreds of laboratory and industrial instruments were designed, manufactured and tested. At the same time it was a decisive discovery : to separate the activity of calibration, testing of the viscometers, i.e. the determination of the constants of instruments from the viscosity measurements of any other certifying laboratories and that of the industry. It led to the establishments of Viscometric Laboratories at the State Organs for Measures in the greater western countries in the second, third decades of the 20. century and later all over the world. (Hungary's Viscometric Laboratory started in 1952.) This stimulated the viscosity measurements of the pure, distilled water, — because the viscosity measurements were based on a single point: the absolute viscosity value of the water at 20 °C — and the tests in connection with the standard liquids and the standard master viscometers. As for the viscosity measurements of the water, at the beginning of this century Bingham's and White's, in the 30-s Erk's and after World War II Coe's, Swindell's and Godfrey's and Maliarov's and Stepanov's activity became well-known and in connection with the viscosity standards; Hardy's and Cottington's, Ubbelodhe's, Weber's and Schmidt's and Kawata's, Ito's and Isozaki's works were important.
