Читать книгу The Rheology Handbook - Thomas Mezger - Страница 47

When performing CSR tests, the rotational speed or shear rate, respectively, is preset and controlled by the rheometer (see Table 3.1). This test method is called a “controlled shear rate test”, or briefly, “CSR test” or “CR test”.

The test method with controlled shear rate is usually selected if the liquid to be investigated shows self-leveling behavior (i. e. no yield point), and if viscosity should be measured at a desired flow velocity or shear rate, respectively. This is the case, if certain process conditions have to be simulated, for example, occurring with pipe flow, or when painting and spraying. Shear rates which are occurring in industrial practice are listed in Table 2.1 (see Chapter 2.2.2).

Table 3.1: Raw data and rheological parameters of rotational tests with controlled shear rate (CSR)
Rotation CSR	Test preset	Results
raw data	rotational speed n [min -1]	torque M [mNm]
rheological parameters	shear stress γ ̇ [s-1]	shear stress τ [Pa]
viscosity calculation		η = τ / γ ̇ [Pas]

Table 3.2: Raw data and rheological parameters of rotational tests with controlled shear stress (CSS)
Rotation CSS	Test preset	Results
raw data	torque M [mNm]	rotational speed n [min -1]
rheological parameters	shear stress τ [Pa]	shear stress γ ̇ [s-1]
viscosity calculation		η = τ / γ ̇ [Pas]

ISO 3219 standard of 1993 recommended to measure and to compare viscosity values preferably at defined shear rate values (i. e., no longer using specifications of rotational speeds, e. g. in rpm). For this purpose, the following two alternative series are specified. Dividing or multiplying these values by 100 provides further γ ̇ -values.

1) 1.00/2.50/6.30/16.0/40.0/100/250 s-1. This geometric series shows a multiplier of 2.5

2) 1.00/2.50/5.00/10.0/25.0/50.0/100 s-1