In the present study, damage evolution in rolled Al-Zn-Mg alloy and its welds is evaluated using the acoustic emission (AE) method and crack initiation is detected using digital imaging during fatigue tests. The AE characteristics and source mechanisms are analysed based on microstructural
and fractographic observations. The experimental results show that AE energies are effective indicators for detecting fatigue crack initiation in Al-Zn-Mg alloys. The results obtained were verified through digital images of the notch tip region of the Al-Zn-Mg alloy samples. For small percentages
of the applied load range close to the peak load, the AE count rates show a reasonable correlation with the crack propagation rates. These correlations can be applied to predict the remaining service life of fatigue-damaged structures. The analyses performed demonstrate that the AE technique
is sensitive to variations in the fracture mode and could be applied to monitor fatigue damage evolution in welded structures.
In this study PM2.5 and other five air pollutants (i.e. SO2, NO2, PM10, CO, and O3) have been analyzed by using statistical methods. Two different regression models were established quantitatively in this paper to find out the factors and causes of PM2.5 and were compared by using the partial data from January 1 to August 26, 2013, which is obtained from Wuhan Environmental Protection Bureau. The results indicate that the correlation coefficients of PM2.5 and other four air pollutants CO, SO2, NO2, and PM10 are all over 0.7, which shows significant linear correlations, and regression models were proved illustrious and accurate by testing and contrast.
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