Behaviour of Perforated Plates under Plane Stress

Auxetic Perforated Mechanical Metamaterials with Randomly Oriented Cuts

Perforated systems with quasi-disordered arrays of slits are found to exhibit auxetic characteristics almost as much as their traditional ordered "rotating-squares" counterparts. This provides a highly robust methodology for constructing auxetics that may be used for various practical applications such as skin grafting, where a high degree of precision may not always be achievable.

Equivalent Elastic Properties of Perforated Bars and Plates

Experimental methods are described by means of which the equivalent elastic properties of bars and plates perforated on a square, a square-diagonal or a triangular pitch (or otherwise) may be obtained.

Bars of rectangular section of steel, gun metal and perpex perforated on a fixed pitch with circular holes to give a wide range in the ratio (pitch/diameter of holes) on square and triangular patterns were tested in flexure and tension. The transverse aeolotropy of such bars and plates was examined and ratios of (equivalent Young's modulus, drilled/true Young's modulus) and equivalent Poisson's ratios were found.

The experimental results obtained were compared with theoretical curves of Bailey and Hicks for perforated plate of square and square-diagonal pitch and with Horvay's plane-stress theory for perforated plate of triangular pitch.

Results have been presented in graphical form for ready application to the design of heat exchanger tube-plates.