The hollow structure of Ni12P5@C/GNS shortens ion transport paths and provides ample room to accommodate volume expansion, indicating its overwhelming superiority in applications.
The Ni2P/NPC composite effectively buffers volume expansion and improves electrochemical performances by creating more defects on the surface, indicating overwhelming superiority in energy storage applications.
The nonlinear wave motion equation is solved by the perturbation method. The nonlinear ultrasonic coefficientsβandδare related to the fundamental and harmonic amplitudes. The nonlinear ultrasonic testing system is used to detect received signals during tensile testing and bending fatigue testing of GH4169 superalloy. The results show that the curves of nonlinear ultrasonic parameters as a function of tensile stress or fatigue life are approximately saddle. There are two stages in relationship curves of relative nonlinear coefficientsβ′ andδ′ versus stress and fatigue life. The relative nonlinear coefficientsβ′ andδ′ increase with tensile stress when tensile stress is lower than 65.8% of the yield strength, and they decrease with tensile stress when tensile stress is higher than 65.8% of the yield strength. The nonlinear coefficients have the extreme values at 53.3% of fatigue life. For the second order relative nonlinear coefficientβ′, there is good agreement between the experimental data and the comprehensive model. For the third order relative nonlinear coefficientδ′, however, the experiment data does not accord with the theoretical model.
When detecting the ultrasonic flaw of thick-walled pipe, the flaw echo signals are often interrupted by scanning system frequency and background noise. In particular when the thick-walled pipe defect is small, echo signal amplitude is often drowned in noise signal and affects the extraction of defect signal and the position determination accuracy. This paper presents the modified S-transform domain singular value decomposition method for the analysis of ultrasonic flaw echo signals. By changing the scale rule of Gaussian window functions with S-transform to improve the time-frequency resolution. And the paper tries to decompose the singular value decomposition of time-frequency matrix after the S-transform to determine the singular entropy of effective echo signal and realize the adaptive filter. Experiments show that, using this method can not only remove high frequency noise but also remove the low frequency noise and improve the signal-to-noise ratio of echo signal.
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