Papers by Author: Liang Rong Zhu

Abstract: In engine compartment, it is difficult to eliminate the effect of interfering signals on vehicle AFM signal by the traditional processing method. According to the characteristic of AFM signal, this paper decomposed the noise signal for 4 layers by selecting Daubechies (db5) wavelet in Matlab based on wavelet theory. After decomposing, and then employed the soft-threshold de-noising method to eliminate noise. At last this paper used the inverse wavelet transform to reconstruct signals for signal de-noising and rebuilding. The test results show that this method can eliminate the noises of AFM signal effectively.

Abstract: Mechanical strength and service life of the coatings manufactured by plasma spray forming are significantly reduced by residual stresses. A 2D finite element model constructed for temperature and residual stress simulation of a single stainless steel splat solidifying and cooling on the carbon steel substrate is presented in this paper. Simulated results show that the temperature of the splat rim is higher than that of the central part during the initial stage of solidification, and the temperature difference between the two parts reverse thereafter. The minimum residual stress locates at the rim of the top surface of the splat, and the maximum residual stress, which decreases when the substrate is preheated to a higher temperature, situates at the rim of the interface. Stresses appear as tensile stresses within the splat and compressive stresses within the substrate. The research can provide quantitative understanding of the temperature and residual stress states at the splat level.

Abstract: During plasma spray forming, the forming quality is directly influenced by the flattening behavior of the droplet impacted onto the substrate, which is determined by the flattening configuration and solidification state of the droplet. In this study, according to the rule of Reynolds number and Peclet number, the flattening behavior of big-size molten droplet impacted onto the substrate with low-speed were experimentally simulated during flattening. The droplets of Sn30Pb70, Zn and ZA12 impacting onto the stainless steel substrate with different velocity were investigated. Splashing degree was introduced to evaluate the flattening profiles of the splats. The relationships between the splashing degree and the impact velocity, Reynolds number and Weber number of the droplet were established. Experimental results show that the flattening and diffusion are impeded by the dynamic viscosity and surface tension of the droplets, and the impeding effects are more remarkable when the impact velocity is lower. The research has a significant ap