**4. Future trends**

In a recent study by Ashrafizadeh [49], a more comprehensive material formulation capable of accounting for hyperelastic, elastoplastic, and stress softening of the elastomer was developed using the FE technique. The material model formulation successfully predicted the elastoplastic and stress softening response of the PU as validated by conducting cyclic deformations of a single element and comparing the stress-strain behavior of the element with that of experiments. This research allowed for an in-depth evaluation of the effect of temperature, material softness, final strength, and elastoplastic behavior on the stresses produced as a result of the impact of erodant particles. The model successfully simulated the cutting mechanism caused by the impact of a single erodant particle (see **Figure 9**). Moreover, the impact of ten solid particles was modelled to study the mechanism of material removal by accumulation of residual strains up to the detachment of material. The model provided support for this mechanism and successfully predicted the shape of the formed asperities (see **Figure 10**) similar to those of the

eroded surface of PU as was observed from experiments (see **Figure 8**).

148 Aspects of Polyurethanes

**Figure 9.** Material removal by cutting mechanism as predicted by the FE model [49].

**Figure 10.** The ridges formed on the surface of an eroded PU as predicted by FE model [49].
