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

After World War II the researches of the polymer systems gave a decisive change for the speedy development of both the theory and the experimental methods in the rheology. It is rather impossible to enumerate the literature of all the results and hundreds of names belonging to it, in such a short lecture. But I emphasize only two moments to give a comprehensive picture: studies of Reiner and Rivlin, Coleman, Markovitz and Noll created the mathematical basis on which the deformations of the simple memory fluids could be discussed. During World War II, Weissenberg and his coworkers disclosed the normal stress effects shearing liquids, in a study of materials for flame throwers. In the most striking way it appears experimentally in the rotational viscometry of the concentrated solutions and melts of polymers. From that time, the characterization of the rheological parameters of the simple fluids needs—in addition to the determination of viscosity (shear stress function)— to determine the normal stress functions too. But the normal stress functions can only be measured with a suitable change of the rotational viscometers. The usual way is to bore very small holes at the surface of the stationary elements, in which the level of the fluid can be brought into connection with the normal stresses through the geometrical constants of the instrument. I pick up only few researchers of the earlier decades because of their pioneering work, who—partly—can be respected as the creators of ,,modern rheometry". In the field of theories and measuring instruments of the polymer systems Staudinger, Flory and Fox, Philippoff, Porter and Johnson, Markovitz and Brown, Schurz, Tordella, Ferry, Tobolsky and Vinogradov, in the field of the applied industrial rheology Scott Blair and Green, in the field of the rheology of food Shama and Sherman and in the field of the rheology of colloid systems Einstein, Hatschek, Szegvári, De Jongj Rabinowitsch and Derjagin have created new things. From among the splendid constructors and reformers of the instruments I mention Mooney and Ewart, who constructed an instrument for the measurement of rubber and in 1924 gave conic ends to the cylinders of the coaxial cylinder viscometers to eliminate the end-effect. 1944 was a milestone in the history of viscometry: Ubbelohde revealed the principle of suspended level and eliminated the surface tension error in the capillary viscometry. In 1945 Piper and Scott constructed the first cone and plate viscometer. Jobling and Roberts brought the Weissenberg-Rheogoniometer to perfection. Vogel-Ossag, Umstatter, Pinkevitch, Fenske and Manning and from among the Hungarians Freund and Vamos created special capillary viscometers. The names of Marschalkó and Barna also must be mentioned, who planned a special, high shear viscometer for the measurements of clay- and bentonite-suspensions in 1954. There are immense physical principles the viscosity can be measured by. Here, it is enough to point to e.g. the group of the Hoppler's instruments—the falling ball instrument was changed by Künzel for viscosity measurements at high pressures in the recent past—or the ultrasonic membrane viscometers. Let me finish my lecture with a motto of Du Buat, a French hydrodinamic, in 1816, according to which: „La fluidité est une proprieté des liqueurs, que nous avons de la peine á concevoir..." in English: „The fluidity is a property of the fluids, which fills us with the pain to know more about it..."