The model underpredicts extensional viscosity when compared with experimental data for the [150 rpm, 5 min] blends, although it shows reasonable agreement with data insofar as predicting the onset of
strain hardening at higher stretch rates.
Due to continuous loading the plastic deformations of the metal increases and hence
strain hardening was developed.
where [sigma] is flow stress, A is the yield stress at reference temperature and strain rate, B is the coefficient of
strain hardening, n is the exponent of
strain hardening, [epsilon] is the true strain, [??]* = [??]/[[??].sub.ref] is the dimensionless strain rate with [??] being the strain rate ([s.sup.-1]), [[??].sub.ref] the reference strain rat ([s.sup.-1]), and T* is homologous temperature, expressed as:
Li, "Introduction of
strain hardening engineered cementitious composites in design of reinforced concrete flexural members for improved durability," ACI Structural Journal, vol.
where [[sigma].sub.s] is the Von Mises equivalent flow stress (MPa), A is the yield stress at a given reference temperature and a given reference strain rate, B is the coefficient of
strain hardening, C is the coefficient of strain rate hardening, n is the
strain hardening exponent, [[epsilon].sup.p] is the equivalent plastic strain, and [mathematical expression not reproducible] is the dimensionless strain rate with [??] being the strain rate and [[??].sub.0] the reference strain rate.
For a given value of 0 < n < 1, the stress-strain curve defined by (1) can result in a rapid increase in the yield stress for small strains or
strain hardening. However, it can be the opposite for values of n > 1, for which large strains produce small stress or softening.
Obtained results can contribute to analyze deformation behavior during repeated loading for several cycles and strain path changes, when twin-twin junctions can form, and they have been shown to play a crucial role in increasing
strain hardening and controlling microstructure evolution.
Calculation of the
strain hardening behaviour of steel structures based on mill tests, Journal of Constructional Steel Research 61(2): 133-150.