Dear readers, For a Biomedical Engineering project I have to develop a model for the respiratory system of a neonate. This will be done by using pressure/volume data of the lungs. To model these, I would like to use a rubber balloon. However the calculation are more difficult than I thought.. (Especially because rubber behaves non-linear and with a hysteresis effect, I will ignore these effects) As assumptions I used the fact that the balloon is perfectly spherical, behaves linearly and the strain is dependent on the radius relative to the original radius (R0). Could anyone help me? Thanks!