Tension mode

In the tension mode, the exponential softening law is assumed (see fig.(3)). The yield function has the following form

$$f_1(\mbox{\boldmath$\sigma$},\kappa_1) = \sigma-f_t(\kappa_1)$$ (22)

where the yield value $f_t$ is defined as

$$f_t=f_{t0}\exp\left(-\mbox{$\displaystyle\frac{f_{t0}}{G^I_f}$}\kappa_1\right)$$ (23)

Figure 3: Tensile behavior of proposed model ( $f_t=0.2\ \rm{MPa},\ G_f^I=0.018\ \rm{N/mm}$)

The $f_{t0}$ represents tensile strength of joint or interface; and $G^I_f$ is mode-I fracture energy. For the tension mode, the associated flow hypothesis is assumed.