Patent ID: 7890275

Claim:
A planar elongational viscosity measuring method comprising: a measurement step of pushing a bomb-shell bob having a narrow bottom surface part into a container, in which a fluid to be subjected to viscosity measurement is filled, from the bottom surface part, and measuring counterforce applied to the bomb-shell bob from the fluid at this time; a stress calculation step of calculating force that the fluid pushes up the bomb-shell bob based on an external size of the bomb-shell bob, and calculating planar elongation stress generated in a space between the bomb-shell bob and the container based on the calculated push-up force, the counterforce, and a cross-sectional area of the space; and a viscosity calculation step of calculating a planar elongational viscosity by dividing the planar elongation stress by a fluid speed increment rate in the space calculated based on the external size of the bomb-shell bob and a push-in speed of the bomb-shell bob into the fluid.