Fracture Toughness of Explosively Welded Al/Ti Layered Material in Cryogenic Conditions

Abstract

In the paper results of comparative analysis of the fracture toughness of explosively welded Al/Ti composite determined for the ambient temperature and for the cryogenic conditions were presented. Testing of mechanical properties of inhomogeneous materials very often presents a lot of difficulties connected with the experimental procedures as well as with the interpretation of study results. It is also in the case of layered Al/Ti material, for which cracking history has different nature for both layers: aluminium and titanium alloy. However, from the viewpoint of practical application, the knowledge of ‘global’ material properties is important. Due to differences of properties of both materials constituting the Al/Ti bimetal, it is hard to talk about determination of material property, which is plane strain fracture toughness K1C. In such case more adequate is fracture toughness KQ value, which can refers to the system of two materials. In investigations compact tension (CT) specimens were used. For specimens used in the tests the ratio of width to thickness W/B was 4. The initial pre-cracks were made by cyclic axial loading of specimens. The experimental tests were made with the use of the axial servohydraulic test system equipped with an original cryogenic chamber. During the tests all parts including specimen, clevis grips, extensometer were immersed in liquid nitrogen. The influence of cryogenic temperature on the fracture toughness was observed as a result of the tests.