Читать книгу The Rheology Handbook - Thomas Mezger - Страница 52

Sometimes in industry, test programs are used showing besides shear rate ramps also other intervals without ramps, for example

1 Rest intervals, presetting constantly γ ̇ = 0 either after a pre-shear interval, or at the start of the test to enable relaxation of the sample after gap setting of the measuring system which may cause a high internal stress particularly when testing highly viscous and viscoelastic samples. Simultaneously, this period is suited to enable temperature equalibration.

2 Pre-shear intervals, presetting a constant low shear rate to distribute the sample in the shear gap homogeneously, and to equalize or even to reduce possibly still existing pre-stresses deriving from the preparation of the sample.