|
The measurement of stress of concrete structures under impact loading and other strong dynamic loadings is crucial
for the monitoring of health and damage detection. Due to its main advantages including availability, extremely high
rigidity, high natural frequency, wide measuring range, high stability, high reproducibility, high linearity and wide
operating temperature range, piezoelectric (Lead Zirconate Titanate, PZT) ceramic materials has been a widely used
smart material for both sensing and actuation for monitoring and control in engineering structures. In this paper, a kind
of stress sensor based on piezoelectric ceramics for impact stress measuring of concrete structures is developed. Because
the PZT is fragile, in order to employ it for the health monitoring of concrete structures, special handling and treatment
should be taken to protect the PZT and to make it survive and work properly in concrete. The commercially available
PZT patch with lead wires is first applied with an insulation coating to prevent water and moisture damage, and then is
packaged by jacketing it by two small precasted cylinder concrete blocks with enough strength to form a smart aggregate
(SA). The employed PZT patch has a dimension of 10mm x 10mm x 0.3mm. In order to calibrate the PZT based stress
sensor for impact stress measuring, a dropping hammer was designed and calibration test on the sensitivity of the
proposed transducer was carried out with an industry charge amplifier. The voltage output of the stress sensor and the
impact force under different free falling heights and impact mass were recorded with a high sampling rate data
acquisition system. Based on the test measurements, the sensibility of the PZT based stress sensor was determined.
Results show that the output of the PZT based stress sensor is proportional to the stress level and the repeatability of the
measurement is very good. The self-made piezoelectric stress sensor can be easily embedded in concrete and provide
reliable stress sensing under dynamic loadings.
|
