Practical application of an improved methodology for the double torsion load relaxation method

摘要

The finite-element analysis performed by Ciccotti (5) shows that Evans' analytical approximation is inadequate to describe the double torsion loading configuration except in a very narrow region of very thin specimens. The calculated corrective coefficients allow one to use a wider region of the specimen and to account for the influence of some geometrical features like the depth and width of the side groove, the length of the initial notch and the inclination of the curved crack front.The application of this method to relaxation tests on lava rocks from the Vulcano volcano in the Aeolian Islands, and quartz-feldspar sandstones from Castel distress-corrosion index are larger than the ones obtained through the classical analytical approximation by about 10 percent. moreover, an estimate of the error introduced in the placement of the curves by an inaccurate knowledge of the crack front curvature was evaluated using the improved factors proposed by Pollet (8).