F V Wvol

The thickness of the buffer plate is related to that of the foam simply by b = phbiast/pb.

An example

A charge of 1 kg of TNT in air produces a pressure pulse p = 5 MPa (50 atmospheres), generating an impulse Ji = 600 Ns/m2 at a distance 1m from the charge. A steel buffer plate (pb = 7900 kg/m3) 5 mm thick acquires a velocity v = 15.2m/s and a kinetic energy Ui = 4.6kJ/m2. The structure can support a pressure of 0.3 MPa (3 atmospheres). The selection chart of Figure 11.3 indicates that a Cymat aluminum foam of density 0.155 Mg/m3 has a plateau stress just below this, and absorbs Wvoi = 200kJ/m3. From equation (11.33) the required thickness of foam is 25 mm.

References

Abramowicz, W. and Wierzbicki, T. (1988) Axial crushing of foam-filled columns. Int. J. Mech. Sci. 30(3/4), 263-271.

Andrews, K.R.F., England, G.L. and Ghani, E. (1983) Classification of the axial collapse of cylindrical tubes. Int. J. Mech. Sci. 25, 687-696

Deshpande, V. and Fleck, N.A. (2000) High strain rate compressive behavior of aluminum alloy foams. Int. J. Impact Engng. 24, 277-298.

Hanssen, A.G., Langseth, M. and Hopperstad, O.S. (1999) Static crushing of square aluminum extrusions with aluminum foam filler. Int. J. Mech. Sci. 41, 967-993.

Kenny, L.D. (1996) Mechanical properties of particle stabilised aluminum foams. Materials Science Forum 217-222, 1883-1890.

Lankford, J. and Danneman, K. (1998) in Shwartz, D.S., Shih, D.S., Evans, A.G. and Wadley, H.N.G. (eds), Porous and Cellular Materials for Structural Application, Materials Research Society Proceedings, Vol. 521, MRS, Warrendale, PA, USA.

Mukai, T., Kanahashi, H., Higashi, K., Yamada, Y., Shimojima, K., Mabuchi, M., Miyoshi, T. and Tieh, T.G. (1999) Energy absorption of light-weight metallic foams under dynamic loading. In Banhart, J., Ashby, M.F. and Fleck, N.A. (eds), Metal Foams and Foam Metal Structures, Proc. Int. Conf. Metfoam'99, 14-16 June 1999, MIT Verlag, Bremen, Germany.

Reid, S.R. and Reddy, T.Y. (1983) Int. J. Impact Engng. 1, 85-106.

Santosa, S. and Wierzbicki, T. (1998) Crash behavior of box columns filled with aluminum honeycomb or foam. Computers and Structures 68(4), 343-367.

Santosa, S., Banhart, J. and Wierzbicki, T. (1999) Bending crush behavior of foam-filled sections. In Banhart, J., Ashby, M.F. and Fleck, N.A. (eds), Metal Foams and Foam Metal Structures, Proc. Int. Conf. Metfoam'99, 14-16 June 1999, MIT Verlag, Bremen, Germany.

Seitzberger, M., Rammerstorfer, F.G., Gradinger, R., Degisher, H.P., Blaimschein, M. and Walch, C. (1999) Axial crushing of foam-filled columns. To appear in Int. J. Sol. Struct.

Seitzberger, M., Rammerstorfer, F.G., Degisher, H.P. and Gradinger, R. (1997) Crushing of axially compressed steel tubes filled with aluminum foam. Acta Mechanica 125, 93-105.

Smith, P.D. and Hetherington, J.G. (1994) Blast and Ballistic Loading of Structures, ButterworthHeinemann, Oxford.

Wierzbicki, T. and Abramowicz, W. (1983) On the crushing mechanics of thin-walled structures. Int. J. Solids Structures 29, 3269-3288.

Chapter 12

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