Abstract
The paper deals with the investigation of Lamb waves ultrasonic testing technique applied for evaluation of different stress-strain and damaged state of aluminum specimens at static and fatigue loading in order to develop a Structural Health Monitoring (SHM) approach. The experimental results of tensile testing of AA2024T3 specimens with welded joints are presented. Piezoelectric transducers used as actuators and sensors were adhesively bonded to the specimen's surface using two component epoxy. The set of static and cyclic tensile tests with two frequencies of acoustic testing (50 kHz and 335 kHz) were performed. The recorded signals were processed to calculate the maximum envelope in order to evaluate the changes of the stress-strain state of the specimen and its microstructure during static tension. The registered data are analyzed and discussed in terms of signal attenuation due to the formation of fatigue defects during cyclic loading. Understanding the relations between acoustic signal features and fatigue damages will provide us the ability to determine the damage state of the structure and its residual lifetime in order to design a robust SHM system.
Highlights
Non-destructive testing (NDT) plays a significant role in development of generation industry from small watch to huge spacecraft
To ensure the safe operation of the structure and simultaneously reduce financial losses during NDT scientific and engineering NDT community few years ago focused on research and development of the Structural Health Monitoring (SHM) systems [1,2]
The signal sensed by the 4th piezoelectric transducer (PZT) is almost the same with the 3rd except the reverse sign of the instantaneous sensed signal magnitude due to the propagation of A0 Lamb wave mode
Summary
Non-destructive testing (NDT) plays a significant role in development of generation industry from small watch to huge spacecraft. The most widespread NDT practice of different structures that is used today utilizes defined time intervals of inspection, but the statistics of testing shows that the damages occur in small amount of tested objects while time and funds for diagnostics of the rest were wasted. SHM is a non-destructive in-situ sensing and evaluation method that uses a variety of sensors attached to, or embedded in, a structure to monitor the structural response, to analyze the structural characteristics for the purpose of estimating the severity of damage/deterioration and evaluating the consequences thereof on the structure in terms of load bearing capacity and residual lifetime. The data can be used to identify damage at its onset, to assess strength and integrity, and the performance and safety
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