Session: DA-04-01 Inelastic, Nonlinear, and Limit Load Analysis

Paper Number: 122912

122912 - Auxetic Domes Under External Pressure 

In view of ongoing interest in novel materials exhibiting Negative Poisson Ratio (NPR), the current study examines its influence on buckling strength of externally pressurised torispherical pressure vessel closures. Failure pressures are computed for a fixed value of Poisson’s ratio, υ = -0.9. Shells being made from two layers are investigated. It is assumed that the outer metallic skin is supported on inside by an auxetic layer. Both metallic and auxetic layers are assumed to be isotropic, and exhibit elastic, perfectly plastic behaviour with the following material properties: E = 207.0 GPa, the yield point of 314.0 MPa for both primary and auxetic layers. A reference hemisphere of diameter, D, wall thickness, t_o, and the ratio, D/t_o = 500 is adopted in computations. The weight of torispheres, W_T equals the weight of the reference hemisphere, W_H. Preliminary computations were carried out for the ratio of volume enclosed by torisphere, V_T, to volume enclosed by hemisphere, V_H, being V_T/V_H = 0.85.

Results of this numerical study show that the inclusion of auxetic layer leads to 30% gain in failure pressures above auxetic-free, and weight equivalent, configuration of the dome. Within the same magnitude of the ratio, V_T/V_H = 0.85, calculations also identified the weakest head. As a result, the ratio of the best to the worst performing geometries was 3.90. The contents of the auxetic layer, i.e., its wall thickness was different for both the best and the worst geometries.

In all computations the shells are clamped at the equatorial plane, and axisymmetric collapse as well as asymmetric bifurcation buckling pressures are searched for.

The ongoing study aims at development of the full envelope of admissible configurations illustrating the role of auxetic reinforcement on a like-for-like basis. These results are to be compared with the previous steel only laboratory size heads which were CNC made and then tested.

Presenting Author: Jan Blachut University of Liverpool

Presenting Author Biography: tba

Authors:

Jan Blachut University of Liverpool
Sala Dariusz AGH - University of Science and Technology; Faculty of Management