**7. Conclusion**

356 Viscoelasticity – From Theory to Biological Applications

1 0

2

A, B, k, l: parameters depending on the initial density

**Figure 24.** One of realized projects in France

Given the approximation of 4

becomes:

t: time, t0: initial time, dp: density of plastic d0: initial density

0

1 1 K ln

*p k l*

33 4

*<sup>t</sup> ff dd d d <sup>t</sup>*

0 0 0

 <sup>3</sup> <sup>4</sup> 2

,

*f K*

*d d t*

2 33 3

1 1 . ; 2

*f K f f*

*<sup>t</sup> d d*

*f* , we can neglect

*f*

1 1 . ln

3 3 12 1 0

 

*p k l*

*<sup>t</sup> f dd d d <sup>t</sup>*

0 0 0

1 1 ln

*p k l*

<sup>1</sup> and 

 

0 0 0

<sup>3</sup> by comparison to (1) and 4

*f*

The development of mono axial and biaxial testing, the design and implementation of an appropriate apparatus helped us to perform many tests. Therefore, the characteristic functions of the material were determined satisfactorily. This allowed us to identify the essential parameters to the theoretical models developed.

In a particular field of stress up to 200 kPa, the simplified model gives good satisfaction. The results are acceptable and the difference between theoretical and experimental ones does not overstep the bounds of uncertainty both in physical measurement and caracteristics variability due to the material anisotropy.

However, in several cases of application, the model in its many forms helps us to conceive and design structures by using this technique. Indeed, many projects were conceived and realized in France (fig.24).
