### Mathematical Description of the Change in Properties of *Casuarina* Wood Upon Exposure to Gamma Radiation. 1. Changes in the Compressive and Tensile Strength

#### Abstract

*Casuarina cunninghamiana* specimens were exposed to gamma-radiation doses ranging from 10^{4} to 10^{8} rad and tested in compression and tension parallel to grain. The percentage values of the irradiated specimens relative to that of the matched control (Y) were determined. The relationship between (Y) and log gamma radiation dose (X) was represented mathematically by the equation: Y = aX^{b}c^{x}. This equation described the change in compressive and tensile strength very well as was detected from the high correlation coefficients. Generally these properties increased slightly at low levels of radiation, reached a maximum, then decreased gradually thereafter. The reduction in tensile strength was more pronounced than in compressive strength.

The threshold dose, i.e., the dose beyond which the properties began to decrease, was calculated. This dose ranged from 3.69 x 10^{6} to 3.76 x 10^{6} rad for compressive strength properties and from 1.51 x 10^{6} to 1.70 x 10^{6} rad for tensile strength properties. This indicated that irradiated casuarina wood had a greater resistance to compression than to tension.

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