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The paper presents the investigation of the grain structure of initial homogeneous aluminum alloy AA8090 and welded specimen using friction stir welding. An optical microscopic study reveals four zones in the welding seam. In order to evaluate deformation and fracture behavior, Charpy V-notch impact tests were performed with the recording of emitted acoustic signals (acoustic emission) and capturing of loading diagrams by the instrumented striker. The formation of a large area of grain boundaries in welded specimen leads to a significant increase in the energy required for the initiation and propagation of a crack under impact loading, while initial alloy demonstrates low impact toughness. Registered acoustic signal was further analyzed by means of wavelet spectrum. [ABSTRACT FROM AUTHOR]

The analysis of the deformation and fracture peculiarities of two kinds of aluminum alloys with different deformation behavior types using AE method was carried out. It is shown that an effective description of deformation mechanisms with the use of AE method can be made by sorting and identification of AE signal sources. Strain stages identified through the strain hardening diagrams are consistent with AE activity graphs for different types of AE sources at these stages. AE activity at the stage of strain hardening substantially depends on heterogeneous structure characteristics of materials under loading. [ABSTRACT FROM AUTHOR]

A combined method to investigation of localized deformation processes in notched aluminum alloy as well as carbon fiber reinforced composite specimens is applied in order to reveal characteristic stages of strain and fracture. Stress concentrators have the shape of a circular hole and edge crack of various sizes. Carbon fiber reinforced composites (CFRC) with notches of different size were also tested in order to illustrate the difference in deformation behavior between metal and reinforced polymeric composites specimens. Use of simultaneous strain data registration has allowed us to register and compare parameters under analysis during entire time of the experiments. The reasons of similarity and difference of the results are shown and discussed. It is offered to apply the obtained results for the aims of non-destructive testing of structural materials being based on revealing characteristic stages of strain development and a particularly prefracture stage. [ABSTRACT FROM PUBLISHER]