The monitoring of structural integrity for pipes is one potential structural health monitoring (SHM) application using piezoelectric sensor networks. A dynamic cooperative identification method (DCIM) for pipe SHM with lead zirconate titanate (PZT) is proposed based on synergetics in this paper. A cooperative identification model with a cooperation–competition–update process was developed and its cooperative identification kinetic equation was established. With the governing principle, the order parameter equation and its potential function were acquired. On the basis of the synergetic effect principle, the adjoint vector was obtained from the regional vectors. By using the self-organization principle, the evolution of each order parameter was obtained through strict mathematical ratiocination. By implementing the iterative update principle, an online structural condition update feature was realized. Subsequently, the assessment indices were confirmed. Finally, the performance of the proposed methodology for damage identification for a pipe structural model with various connector damage scenarios created by loosening connectors was investigated. The experiments were conducted in a noisy environment, a disturbance rich environment, and a noisy and disturbance rich environment, separately. The results show that the proposed methodology can identify the healthy condition and various damage conditions within an acceptable monitoring range for metal pipes. Furthermore, the DCIM demonstrates a strong ability to reject disturbances and noise in SHM applications. This proposed approach provides an alternative way to carry out damage and fault identification for pipe engineering structures.
The finite deformation of rubber under multiaxial stress will finally result in its fatigue failure. The ability to predict the effects of complex strain histories on fatigue life is a critical need. The cracking energy density (CED) distribution characteristics in the finite deformation and rubber fatigue life estimated by the CED criterion are investigated. Then the influences of the crack orientation angle u and the principal stretch ratio k on the relationship between CED and strain energy density (SED) are obtained. Finally, the results are used for predicting the fatigue life of rubber material and are compared to experimental values. The results indicate that the ratios of the predicted lives based on the CED damage parameter and measured lives are within two times scatter factor and that of the predicted lives based on the SED damage parameter and measured lives are greatly influenced by the crack orientation angle u. The rubber fatigue life has great relationship with the angle of the crack plane normal vector and the first principal stretch direction.
Direct Current (DC) electrical resistivity is a material property that is sensitive to temperature changes. In this paper, the relationship between resistivity and local temperature inside steel shell battery cells (two commercial 10 Ah and 4.5 Ah lithium-ion cells) is innovatively studied by Electrical Resistance Tomography (ERT). The Schlumberger configuration in ERT is applied to divide the cell body into several blocks distributed in different levels, where the apparent resistivities are measured by multi-electrode surface probes. The investigated temperature ranges from −20 to 80 °C . Experimental results have shown that the resistivities mainly depend on temperature changes in each block of the two cells used and the function of the resistivity and temperature can be fitted to the ERT-measurement results in the logistical-plot. Subsequently, the dependence of resistivity on the state of charge (SOC) is investigated, and the SOC range of 70%-100% has a remarkable impact on the resistivity at low temperatures. The proposed approach under a thermal cool down regime is demonstrated to monitor the local transient temperature.
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