Computed Radiography and Microtomography of Riveted Lap Joints of Glare Subjected to Constant Amplitude Loading (CAL) Fatigue

摘要

Riveted lap joints made of two sheets of Glare are known to develop cracks at the faying surfaces of aluminum sheets when subjected to cyclic axial constant amplitude loading (CAL). The purpose of this work was to conduct high-resolution digital radiographic inspections of cracks generated by the CAL in the aeronautical grade Glare riveted hybrid composite lap joints and to show that misinterpretations of crack position by computed radiography (CR) of one projection can be solved by computed microtomography (μCT). Glare joints with two aligned rivets were studied after a number of CAL fatigue cycles. Cracks have propagated from the rivet holes towards the lateral boundaries of the test specimen in the inner aluminum layers. High definition CR showed a similar quality and details of conventional X-ray radiography using (nondestructive technique) NDT film. However, when multiple cracks are detected, it is quite difficult to determine from which aluminum plate layer they have been propagated, because depth resolution is impossible with just one radiographic projection. In this case, by using computed microtomography this drawback has been overcome so that details of multiple fracture patterns are revealed and the ambiguity is solved, proving to be a more elucidative methodology towards inspecting assembled components and complex shaped materials and structures.