Keywords: sand, cold box, triaxial test, temperature and rate dependence.

In this paper we present mechanical and thermo-mechanical investigations of an epoxy resin cold box sand, which enables the consideration of the strong influence of the sand mould and sand core during solidification in a sand casting process. To this end uniaxial compression and tension tests were performed, which render a pronounced strength-differential or S-D effect, [1,2,3,4]. Furthermore, the uniaxial tests show a rate dependence in the compression regime, with an increasing strength maximum for increasing loading rate. In future works we will also investigate the rate dependence in the tension regime.

Furthermore, triaxial tests with additional radial pressure (1, 5 and 10 bar) are applied. A linear dependency between the effective shear stress and the total shear stress could be observed.

In addition, the effect of pure thermal loading without regarding the mechanical loading was investigated. To this end different strategies were tested, heating in an oven and heating with an inductor. Since the cold box sand is non-magnetic we use stainless heat exchangers with different ring geometries, which allow the heat transferring from the ring to the sand. An important criterion is, that the temperature in the cold box sand should reach the reference temperature of the oven or ring, respectively, as fast as possible. Comparing all ring geometries and the oven method, one of the ring geometries shows the best results and therefore will be used for future work.

The heating of the specimen and the ensuing mechanical loading is done in two steps. In the first step the cold box sand is heated up to the appropriate temperature, and in a second step the inductor and heat exchanger are removed, such that a pure mechanical loading is applied. This two step method is chosen in order to prevent the heating-up of the testing machine. In the mechanical response of the sand we observe a rapid decrease of maximum strength with increasing thermal loading up to 600°C.

With the experimental data we intend to develop and identify a material model for sand, taking into account the S-D effect, rate and temperature dependence and the effect of hydrostatic stress states.

1

Spitzig W.A., Sober R.J., Richmond O., "Pressure dependence of yielding and associated volume expansion in tempered martensite", Acta Metallurgica, Vol. 23, pp. 885-893, 1975. doi:10.1016/0001-6160(75)90205-9

2

Spitzig W.A., Richmond O., "Effect of hydrostatic pressure on the deformation behavior of polyethylene and polycarbonate in tension and in compression", Polym. Eng. Sci. Vol. 19 (16), 1129-1139, 1979. doi:10.1002/pen.760191602

3

Ehlers W., "A single-surface yield function for geomaterials", Acr. Appl. Mech. Vol. 65, pp. 246-259, 1995. doi:10.1007/s004190050015

4

Mahnken R., "Strength difference in compression and tension and pressure dependence of yielding in elasto-plasticity", Computer Methods Appl. Mech. Engrg. Vol. 190, pp. 5057-5080, 2001. doi:10.1016/S0045-7825(00)00364-9

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