Papers by Author: Peng Wang

Abstract: It is the hotpot to study the application of stochastic resonance (SR) in the field of mechanical fault diagnosis. The fault diagnosis system based on SR was developed, using “ARM+DSP” dual-core structure as hardware and embedded system as software, implemented signal acquisition, data storage, data analysis, waveform display and so on. The SR was adopted as characteristic quantity to analyze vibration signals for fault diagnosis. The experiment results showed that the function of portable fault diagnosis instrument is stable. It has veracity and validity.

Abstract: A stream turbine bowed and twisted blade has been taken as an example for complex parts. Firstly, a simplified computing method for the blade with centrifugal effect is put forward. Then the finite element model of complex parts with centrifugal effect is established. Simulation results show that errors between calculation and simulation results are less than 15%, the simplified computing method has good application value. In addition, the impacts of centrifugal and heat on blade radial deformation are discussed by thermal structural coupling analysis. Numerical simulation results show that heat is the major factor that affects blade radial deformation.

Abstract: Soil moisture plays an important role in agricultural drought predicting. Hydrological models can be employed to forecast soil moisture. In order to get better predicted soil moisture information, we use two basin hydrological models, i.e. XXT and TOPMODEL, to forecast the soil moisture for Huaihe River watershed. The performance of both the two models was tested in the Linyi watershed with a drainage area of 10040 km², a tributary of the Huaihe river, China. The results show that the soil moisture simulated by the XXT is more agree with the observed ones than that simulated by TOPMODE compared to the filed observed soil moisture at 10 cm or the mean ones of 10 cm, 20 com, and 40 cm from surface, and that the predicted soil moisture by both the models has the similar trend and temporal change pattern with the observed one. However, both the models need to be improved in soil moisture forecasting in the future work.

Abstract: On the basis of previous work, this paper aims to build several proper drought indices based on the basic computation for the band information of passive microwave remote sensing AMSR-E data in Huaihe river basin. Compared with measured soil moisture, optimal drought indices have been selected to explore the spatio-temporal variation laws of drought conditions and its impact factors. The results indicate that there are satisfactory negative correlations between MPDIs (Microwave Polarization Difference Index) and observed soil moisture on the whole, which means the more negative the index is, the more serious the drought will be. Besides, MPDIs at frequency 69GHz and 187GHz calculated by AMSR-E brightness temperature data are much closer to the variation trend of soil moisture than those obtained from other bands.

Abstract: Taking MATLAB as the experimental platform, the detection and recongnition method of steel ball surface defect is put forward. With the method, we could determine whether there are surface defects or not, and identify the types of defects. The process of detection and recognition is as follows: Firstly, two-time wavelet de-noising treatment of the steel ball image is achieved by means of ecomposition, quantization of threshold and recongnition of Sym4 wavelet function, afterward, many collected noise of the steel ball image is reduced effectively. Secondly, the de-noised image is preprocessed and then we can calibrate the boundary of the defects accurately, which is used to extract the characteristic parameters of defects. Thirdly, the types of defects of steel ball are judged, and the process of pattern recognition is reasonablely designed by putting forward the shape parameter F, combined with the characteristic parameters of the defects. Lastly, the feasibility and validity of the detection and recongnition algorithm are verified by lots of analysis about experimental results especially the analysis on the experimental results comparing with the given data.

Abstract: Experiment of hard cutting GCr15 with PCBN cutting tools, the influence of tool’s inclination angle and cutting parameters (cutting speed and feed speed) on cutting forces and cutting temperature are studied. A three-dimensional finite elements model using the commercial software Deform 3D 5.03 is developed. The friction between the tool and the chip is assumed to follow a modified Coulomb friction law and the adaptive remeshing technique is using for the formation of chip. The workpiece material property is a function of temperature, strain, and strain rate in the primary and secondary shear zones. Finite element method is used to simulate three-dimensional precision cutting, including orthogonal cutting and oblique cutting. The cutting forces and back forces are slightly changed by tool’s inclination angle. However, in high cutting speed, the cutting force decrease as the tool’s inclination angle increase, while the cutting temperature increase as the tool’s inclination angle increase. The simulation results are compared with experimentally measured data and found to be in good agreement to some extent.

Abstract: Aiming at different grinding surfaces of hardened bearing steel GCr15, this paper made experimental research on detection method of surface roughness based on image technique. Adopting cold light source and five kinds of LED light sources, such as low-angle light, collimated light and coaxial light, we analyzed image characteristics of grinding surface under different processing conditions and found that there was a good correlation between standard deviation of gray variance and roughness of grinding surface. In comparison with the results from traditional surface roughness measuring instrument, we gained the corresponding relation between different grinding surface roughness and standard deviation of image gray variance. It was proved by calculating that they have a good correlativity.

Abstract: Carbonaceous fillers have been widely applied in electrically conductive coatings due to their cheaper, steady electrically conductive capability and other excellent performances. Electrically conductive coatings were synthesized by using graphite and carbon black as fillers in the alkyd resin matrices. Influences of various fillers on electrical conductivity of coatings have been investigated in detail.

Abstract: Aiming at the problem of image recognition in the process of defected chip generation of automatic machining, fuzzy category methods of RBF net and eight neighborhood Euler numbers are researched in this paper. They are based on fuzzy theory and neural net. The gradient steepest descent of optimization theory is used and aberration is minimized by step between required output and actual output. By modifying studying algorithm, recognized capacity is increased. This method is tested in Matlab platform. It can be concluded that fraction of chip image under sophisticated surrounding may be recognized accurately through this net.

Abstract: A series of test for the fatigue crack growth rate da/dN and the threshold ΔKth values were performed with CT specimens on a ship-condenser material titanium alloy plate and rolled ring. Base metal, welded joint and HAZ (heat affected zone) materials were used to make different test specimens. Specimens made from the titanium plate were cut along L-T direction, those made from rolled ring were obtained along C-R and L-R direction respectively. Results show that the fatigue crack growth rate value of welded joint is much higher than those of base metal and HAZ material. The da/dN values of C-R direction specimens are much higher than those of L-R direction specimens, whereas the ΔKth values are lower. It means that welding process may lead to a great reduction in the fatigue property for titanium alloy and the effect of crack orientation on fatigue property is not negligible for titanium alloy. To select a proper orientation of titanium material is therefore very important in engineering practice. Results also indicate that a simplified method can be used to calculate the ΔKth values for titanium material, that is, ΔKth values may be calculated directly from the da/dN expression in a zone near the threshold and the laborious measurements of ΔKth may therefore be saved.