Material Functions for Steady-State Elongational Flow

3 Material Functions for Steady-State Elongational Flow 

For uniaxial elongational flow, the elongational viscosity jjg may be defined by the ratio of tensile stress T li and elongation rate e  

Note that Eq. (2.15) defines the rate-of-strain tensor d in steady-state uniaxial elongational flow. If the surfaces transverse to the direction of principal elongation (i.e., the direction of stretching) are unconstrained, we have 

we present some representative expressions for yjg based on the constitutive equations presented in the preceding sections. 

Let us consider the upper convected Maxwell model given by Eq. (3.4). For steady-state uniaxial elongation flow, for which the rate-of-strain tensor d is defined by Eq. (2.15), we have (see Appendix 3E) 

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