Use of piezoelectric techniques monitoring continuum damage of structures
Nhassengo, Sikhulile Khululeka
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The objective of the present study was to investigate if piezoelectric techniques or sensors can be used in monitoring structural degradation. The study considers experimental results and analytical modelling of a ductile structure under tensile and cyclic loading. Throughout the project the emphasis was placed on the effectiveness of strain measuring sensors. Conventional tensile testing was conducted using a Lloyds testing machine. The testing machine was calibrated to have a lateral movement of 2mm/min (tension force). Rectangular plates were pulled in tension until failure. From that experimental data was produced for a uni-axial loading system. Cyclic testing was carried out using an in-house designed and manufactured fatigue machine. It produced a reciprocating load (force) of 25rad/s on a rectangular plate. Two different sensor measuring instruments (strain gauge and piezoelectric) were used. The strain gauge sensor was attached to a specimen and connected to a Wheatstone bridge. The piezoelectric sensor was attached to the specimen and then linked directly to the capturing system. From these two sensors experimental results were obtained and compared. The mathematical relationships for the rectangular plates were formulated using effective stress-strain behaviour based on the elastic and plastic behaviour of the plates. The analytical and experimental results were compared. Results from this investigation show that piezoelectric sensors can be useful for measuring fatigue failure on a ductile material.