Papers by Author: Jian Xin Zheng

Abstract: Orthogonal experiments of ultrasonic deep rolling with Longitudinal-torsional vibration (UDR-LTV) and conventional deep rolling (CDR) Q235 steel were carried out to study the effects of processing parameters on surface roughness. The orthogonal experiments results show that the influence laws of processing parameters on surface roughness are the same, and the values of surface roughness obtained by UDR-LTV are smaller than that of CDR with the same processing parameters. The values of surface roughness obtained by UDR-LTV and CDR increase and then decrease with the increment of the static pressure; and increase with the increment of the feed-rate, and change a little along with the increment of the rolling speed. Meanwhile, the feed-rate has a marked effect on the surface roughness, while the rolling speed has a little effect on the surface roughness. The quadratic regression method is used to construct the mathematic model to predict surface roughness based on the experimental results. The effects of parameter interactions on surface roughness are studied. The research shows that the interaction effects of the rolling speed and the feed-rate, the static pressure and the feed-rate on surface roughness are obvious, but the interaction effect of the static pressure and the rolling speed on surface roughness is not significant. The optimal parameters for the lowest surface roughness are given by the result of orthogonal design and prediction model, which has guiding significance for the application of ultrasonic surface strengthening technology with complex vibration mode.

Abstract: The mechanism of longitudinal-torsional vibration (LTV) realized by using converter with multiple diagonal slits (MDS) was analyzed based on the acoustic wave propagation when acoustic wave enters obliquely from steel to air. The influences of geometrical parameters of the stepped compound horn with multiple diagonal slits on natural frequencies of LTV were studied with finite element analysis (FEA). The design procedure of stepped compound horn with LTV was provided. The vibration characteristics of actual horn were analyzed with simulation and test. The FEA results show that LTV of the output end of the stepped compound horn may be realized when the input end is excited by longitudinal vibration at certain natural frequency if suitable geometrical dimensions are selected, and the amplitude of the horn is periodical; the trajectory of the particle in the output end is helical curve. The test results indicate that LTV may be realized by stepped compound horn under single acoustic excitation, and the vibration frequency is close to the simulation result, and its vibration properties are good. This method may be applied to design the acoustics system of ultrasonic machining with LTV under single acoustic excitation.

Abstract: The kinematics model was built based on the principle of ultrasonic deep rolling (UDR) with longitudinal-torsional vibration (LTV), and the trajectory equations of any particles on edge of the roller involved in the process were given; the influences of vibration parameters including phase angle, frequency of LTV, amplitude of longitudinal vibration, amplitude ratio and the rolling process parameters including roller radius, rolling depth, feed rate, the rotation frequency of roller on the trajectory, acoustic system design and processing quality were discussed. The results can provide theoretical basis for the design of acoustic system and optimization of process parameters.

Abstract: Realization of longitudinal-torsional complex vibration by conical compound horn has more engineering application value with respect to the conventional longitudinal-torsional complex vibration converting devices. The frequency equations of longitudinal vibration and torsional vibration for the conical compound horn made up of cone and circular cylinder were given based on the wave theory of longitudinal vibration and torsional vibration of ultrasonic horn. The mechanism of the realization of longitudinal-torsional complex vibration by conical compound horn under single acoustic excitation was explained. And a numerical example indicated that longitudinal-torsional complex vibration could be realized by conical compound horn when the length and diameter of such horn were well chosen. The results of this study may be used in the field of longitudinal-torsional complex vibration ultrasonic machining.

Abstract: Simulations of the supersonic flow field inside and outside of the Laval nozzle with single hole and nine holes were carried out based on the computational fluid dynamics method. The effects of different standoff distance and particle diameter on impact velocity of Cu particle spraying from single hole and nine holes were investigated firstly. The results show that the particle velocity obtained with the nine holes nozzle is higher than that of the single hole nozzle under the same standoff distance, and the smaller the standoff distance, the higher the particle velocity may be obtained with the nine holes, and the higher particle velocity may be obtained with smaller particle diameter for particles with diameters of 1 ~ 15 μm. Furthermore the effects of different spraying pressure and temperature on particle velocity of Cu particle spraying from the nine holes nozzle were also studied. And the simulations indicate that the higher the spraying pressure and temperature may make the particle spraying with greater velocity.

Abstract: A new-type of dredging equipment for the coal bunker is designed to solve the clogging problem, which avoids the disadvantages of the existing dredging technology used in the collieries. The new dredging method borrows ideas from air cannon dredging technology, and applies dynamic high pressure generation principle. In the process of dredging, the rubber bullet in the launch canister is accelerated by the controlled high pressure air, and impacts the coal in the arch with high speed so as to recover the coal bunker. The dredging mechanism and process are expatiated and the main structures of the dredging equipment are introduced. The structure of the new type dredging equipment for the coal bunker is simple and the equipment is of high adaptability and safety.

Abstract: Research on ultrasonic extrusion under different process parameters for 45 steel shaft based on orthogonal test is carried out. The influences of various process parameters on shaft surface roughness and micro hardness are analyzed. The experimental results show that the influences of tool radius, pre-pressure, feed rate and rotating speed in the ultrasonic extrusion on surface roughness and micro hardness are different, but there are optimal values in the given experimental conditions. Compared with conventional extrusion, it can reduce the part surface roughness and improve surface micro hardness significantly in the process of ultrasonic extrusion.

Abstract: Acoustic system is the core component of power ultrasonic, which is designed by traditional analytic method and modal analysis with finite element analysis method. And component of the step-like horn with rectangular sections and tool head used in two dimension ultrasonic polishing without abrasives are studied, and the calculating results and modal analysis results are consistent on the whole. The harmonic response analysis for the component of horn and tool head is carried out and the three dimensional coordinates of the vibrating node on the tool head with maximal displacement are obtained. The fitting result shows that the moving trajectory of such node is ellipses, which meets the experimental requirement well. So a new way for designing acoustic system of two dimensional ultrasonic vibration through combining theoretical calculation with computer aided design may be applied.

Abstract: Technology of NC-contour evolution ultrasonic assisted creep feed grinding (NC-CEUACFG) blade surface was put forward to solve the difficult problem of machining ceramic blade surface. The static load on the grinding wheel and the influence of the rigidity of the grinding wheel on the surface precision were studied combined with the movement analysis between the blade and grinding wheel in the process of NC-CEUACFG ceramic blade surface, and the physical model of static load may explain the decrease of grinding force and increase of the relative rigidity of the grinding wheel in NC-CEUACFG in theory. The primary experiment of NC-CEUACFG blade surface was carried out according to the experimental results of previous optimized process parameters, and the integral impeller was machined directly in the blank material of Al2O3 ceramic, which indicated the application prospect of such technology.

Abstract: The gas velocity and particle velocity in and out of the nozzle have great influence on the coating effect in the process of cold spray. An axis-symmetric two-dimensional mathematical model was presented to study the flow field in and out of cold spray nozzle, and the effect of different pressure, temperature, spraying distance and particle diameter on gas axial velocity and particle velocity were researched. The simulation results showed that the gas axial velocity and particle velocity increased when the gas pressure and temperature were increased, spray distance had little effect on the flow field in the nozzle, and small diameter particle was more easily accelerated.