Abstract: Rheological behaviour of bentonite film between grains of molding sand were tested with a self-designed apparatus. Test results show that rheological character of the bentonite film can be expressed as Bingham-Kelvin model or B-K model. Furthers thixotropy and stress-relaxation were observed during deformation of bentonite filmand the degree of their effect on the compaction of molding sand were estimated.

Key words: Bentonite film, character, Molding sand, Rheological, Bionic design, Egg shape function, Eggshell, Keywords: Pressure hull