Papers by Author: Ai Xin Feng

Abstract: For the current problem that grate bed can not recover its own waste heat in the course of cycle working, combined with the structure of the chain grate and hot air flow process, a three-section heat recovery unit of grate bed and waste heat recovery hot air flow process are designed. According to the principle of repeated convective heat transfer, the amount of recovering waste heat of heat recovery unit is estimated, and simulation analysis is conducted by using fluent software. The results show: after three heat exchange between the hot exhaust gas at around 100°C and the grate bed, the hot gas at a temperature of around 427 °C can be obtained, and the waste heat recovery rate is above 60%; simulation results are compared with the estimated value so that it can be obtained that the differences between the two values in the temperature of three-section outlet gas are basically consistent, about 8°C, 4°C, 7°C respectively, which verifies the effectiveness of the heat recovery unit design and the accuracy of Fluent simulation.

Abstract: X-ray diffraction analysis methods analyze the residual stress the same location for 50 times of 7050 aluminum alloy. And taking residual stress error for statistical analysis, through hypothesis testing and analysis of the residual stress error Square diagram, obtain X-ray diffraction the residual stress error of the 7050 aluminum alloy approximately obey normal distribution.

Abstract: In the experiment, we use pulsed laser to conduct discrete scratching on Ni-containing stainless steel protective coatings to test residual stress situation after the matrix is scratched; then to analyze the the impact of the impact stress wave on coating - substrate bonding strength according to the test results, finally to infer the laser power density range within which it occurs coating failure. The study shows that: after laser discrete scratching, the residual stress of the center of the laser-loaded point on matrix surface gradually reduces when the pulsed laser power density increases. The matrix produces a corresponding residual compressive stress under the laser power density reaches a certain value. The actual failure threshold values are 12.006 GW/cm2, 11.829GW/cm2 and 12.193GW/cm2 measured by the three-dimensional topography instrument testing the discrete scratch point of three groups of samples and verified by using a microscope

Abstract: Residual stress determination by X-ray diffraction is theoretically analyzed. Using stress of two directions analysis method, the magnitude and direction of the principal stress which is induced by laser shocked wave can be calculated. The results indicate that the calculated value consists with that of the experimental data, which shows that the surface stresses state comprehensively. Meanwhile, the relationship between the principle stress and single stress with different energies are analyzed.

Abstract: Considering the current problems of low temperature of recovered gas, the direct gas emission of the fourth cooling zone in the operation of the annular cooler, thermal airflow process for the annular cooler is improved by analyzing the thermal airflow process and the structure of the annular cooler and using the principle of repeated convective heat transfer. Thus the above-mentioned problem can be solved. Simulation model of its thermal airflow process is established and the simulation results, obtained by using Fluent software, are as follows: the temperature of the gas in the first cooling zone entering the rotary kiln of the improved is about 110°C higher than that of the unimproved, the temperature of the gas in the second cooling zone entering the preheat zone I of the chain grate of the improved is about 150°C higher than that of the unimproved, and the temperature of the gas in the fourth cooling zone entering the downdraft drying zone of the chain grate of the improved is about 50°C higher than that of the unimproved. Pellet heat recovery efficiency is increased significantly.

Abstract: Residual stresses of model S1100 of crankshaft chamfer were measured by the technology of XRD. The distributions of residual stresses under mechanical peening, mechanical rolling and isothermal quenching are measured, and the tests of fatigue life were conducted. The results showed that the distribution of residual stress by machining in the crankshaft chamfer is complicated, which is at the tensile-compressive status, and it is one of the main factors to affect fatigue life of the crankshaft; isothermal quenching improves the distribution of residual stress, and tensile stress of the crankshaft chamfer is changed into the compressive stress, which may satisfy the requests of fatigue testing for 5 × 106 cycles. Although the mechanical rolling improved the residual stress distribution in the chamfer linked with the crank, tensile stresses in the chamfer connected with the linkage also increase, which influences the service life of the crankshaft.

Abstract: Laser shock processing (LSP) employs high-energy laser pulses from a solid-state laser to create intense shock waves into a material, which can induce compressive residual stresses in the target surface and improve its mechanical property efficiency. Three different ablative, sacrificial coating were chosen to protect the 6061-T651 alloys from surface melting by laser pulse. This paper analyzes the effect of the paint and foil coatings on the shock wave propagation into the 6061-T651 alloys and the resulting change in mechanical properties. The depths of hardening by laser processing of 6061-T651 alloys up to 1 mm, and the surface hardness reach to 138HV. When the laser pulse energy density increase from 2.8 GW/cm2 to 3.6 GW/cm2, the surface hardness of the black paint, aluminum foil and silica acid black paint samples increase to 19
, 27
, 36
respectively.

Abstract: The diesel engine cylinder was processed by laser honing (LH) device, the structure morphology was observed with scanning electric mirror (SEM), and lubricant consumes and wear performances were measured, at the same time the mechanism of LH and effects of laser parameters on LH results were analyzed. The experimental results are shown that LH is a kind of phase transformation treatment by laser, which processes a hardening belt in the certain distributing form on the work-piece surface, and forms the hardness distribution of soft and hard material alternatively; LH may lower the engine oil consumes 30%-60%, and reduce the pollution of the catalyst machine, and lower the grain let of the engine oil 25%-30%. LH intentionally machines the grain cave, which has the certain angle, depth, and width etc.. The surface microcosmic sculpting has the lubricating function for usage process, and storage and transport lubricant, which improves the rubbing condition, then lower the part wear and increase the other performances. The short-wave laser is more applicable to the LH process, which improves the lubrication condition, and increases the service life of the engine and the efficiency, and lowers the engine oil consumes.

Abstract: The theoretical researches on fabrication, measurement and identification of laser marking system of 3D(three-dimension) anti-counterfeiting identifiers have been done in this paper. 3D identifiers were fabricated and 3D identifiers’ modelings were reconstructed, and binary coding of gray images were encoded by programmable control of liquid crystal mask, spatial modulating of laser beam and photolithography fabrication technics. We regarded the depth of 3D identifiers as anti-counterfeiting information, and the original marking data and anti-counterfeiting information are saved in remote database server by database technology and computer network technology，so true produces can be distinguished from fake through network. The basic theory of 3D nondestructive anti-counterfeiting identifiers based on liquid crystal mask was built, and a new technology of creating 3D anti-counterfeiting identifiers by laser shock wave was set up, which differs entirely from marking by laser ablation (or laser thermal effect). A new high-efficiency theory of detecting and identifying on 3D anti-counterfeiting identifiers by 3D identifiers’ reconstruction and binary coding was set up. The study enriches dynamic plastic deformation theory of partial high-strain-rate and anti-counterfeiting design & manufacturing theory which is also a highlight based on advanced manufacturing theory of mechanical effect on laser shock wave.

Abstract: The laser shocking to the Al2O3 ceramics was proceeded, and the fracture microphology that formed from the strong laser shock processing (LSP) was analyzed by the Scanning electron microscopy (SEM). It was discovered that the feature of ceramics responds differently when the laser energy was changed. The brittle fracture that consists of intergranular fracture and cleavage fracture was the main mode under high energy laser shocking (laser pulse enegry: 42J); the macroscopical fracture characteristic was the radial crack. When the laser energy reduced to a fit level (25J), the brittle fracture of ceramics appears to the characteristic of plastic deformation, its fracture microphology appears lots of slippage lines, and the macroscopical feature of radial crack under 42J become subulate crack. While the energy reduced to 15J, the Al2O3 ceramics did not fracture, its micro-hardness ascended, a feature of micro-plastic deformation was existed under the low energy. The reason of the brittle materials appears to the feature of plastic deformation was analyzed.