EFFECT OF THE TEMPERATURE AND ANISOTROPY OF SHEETS FROM Al - Cu - Mg - Li SYSTEM ON THE MECHANICAL PROPERTIES IN THE RANGE OF SMALL PLASTIC STRAINS

The main static design characteristics of sheet semi-finished aircraft materials are obtained from the results of tests for uniaxial tension, compression and bearing. At the same time, the Ramberg - Osgood equation is widely used for the analytical description of strain diagrams under static tension in the region of small plastic deformations. The inverse anisotropy resulted from the crystallographic texture after rolling is characteristic of the sheets of aluminum-lithium alloys. We have studied the mechanical characteristics of 1441RT1 alloy sheets under static loading (tension, compression, bearing) in three rolling directions (longitudinal, long transverse, at 45° angle to the longitudinal direction), with an estimate of the Taylor factor characterizing the texture of the material. Tension tests were carried out at a temperature of-70, +20, + 85, and +125°C, compression and beading tests were carried out at a temperature of 20°C. Test temperatures were chosen proceeding from operating conditions of panel skin materials. The Ramberg - Osgood coefficient was determined from the tensile and compressive strain diagrams. To determine the Taylor factor, the X-ray texture analysis was performed with the construction of inverse pole figures. It is shown that for 1mm- and 3-mm sheets of aluminum-lithium alloy 1441RT1 the test temperature corresponding to the operation temperature has a weak effect on the tensile strength characteristics in the region of small plastic deformations. At the same time, the Ramberg - Osgood coefficient is a characteristic most sensitive to the exposure temperature, rolling direction and sheet thickness. The functional dependence of the Ramberg - Osgood coefficient on the rolling direction and the exposure temperature has been determined for 1-mm and 3-mm sheets of 1441RTlalloy.

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