Chaojun Yang

Mechanical Properties and Microstructure of Bionic Non-Smooth Stainless Steel Surface by Laser Multiple Processing

Laser multiple processing, i.e. laser surface texturing and then Laser Shock Processing (LSP), is a new surface processing technology for the preparation of bionic non-smooth surfaces. Based on engineering bionics, samples of bionic non-smooth surfaces of stainless steel 0Cr18Ni9 were manufactured in the form of reseau structure by laser multiple processing. The mechanical properties (including microhardness, residual stress, surface roughness) and microstructure of the samples treated by laser multiple processing were compared with those of the samples without LSP. The results show that the mechanical properties of these samples by laser multiple processing were clearly improved in comparison with those of the samples without LSP. The mechanisms underlying the improved surface microhardness and surface residual stress were analyzed, and the relations between hardness, compressive residual stress and roughness were also presented.

Simulation, analysis and validation of residual stresses on LY2 aluminium alloy by laser shock processing with elliptical spot

Abstract The effects of laser shock processing on the residual stresses of the LY2 aluminium alloy samples with elliptical spot (long axis length, 12 mm; short axis length, 3 mm) were experimentally investigated, and the effects of the overlapping rate on the residual stresses were simulated using the Abaqus software. The simulated residual stresses were basically in agreement with the measured data, and the relationship between the magnitude and uniformity of residual stress and the overlapping rate was also addressed. Results show that the largest stress magnitudes are located on the top surface of the sample, and the greatest uniformity is achieved by the overlapping of elliptical laser spots. The overlapping rate is critical for the uniformity of the residual stress across the surface. Within a certain impact number range of one to four times, increasing the shocked number can increase the magnitude of residual stress near the surface but not effectively increase the plastically affected depth.

The Mechanism and Experimental Study on Laser Peen Forming of Sheet Metal

Laser peen forming of sheet metal is a new plastic forming technique based on laser shock waves, which derives from the combination of laser shock processing and conventional shot peening technique, it uses high-power pulsed laser replacing the tiny balls to peen the surface of sheet metal, when the laser induced peak pressure of shock waves exceeds the dynamic yield strength of the materials, the sheet metal yields, resulting in an inhomogeneous residual stresses distribution in depth. The sheet metal responds to this residual stress by elongating at the peened surface and effectively bending the overall shape. On the basis of analyzing the mechanism of laser peen forming, the line-track-peening experiments of 45 steel sheets with 2 mm thickness were carried out; a curved sheet metal with deep layer of residual compressive stress was obtained. The preliminary experiment result shows that laser peen forming can offer desirable characteristics in shaped metals and is a valuable technique for producing components for a range of industries.

Theoretical Study on the Bending Deformation of Metal Plate Induced by Repetitive Laser Shot Peening

The laser peen forming (LPF) uses high-power pulsed laser beam replacing the tiny medium balls to peen the surface of plate and generate compressive stress near the surface, the metals respond to this residual stresses by elongating at the peened surface and effectively bend the overall shape. In this paper, the deforming process of metal plate induced by repetitive pulsed laser was discussed from theory firstly, and the bending mechanism of LPF was investigated. Then a mathematical model of bending curvature concerning the depth of residual stress was presented, the influence of residual stresses on the deformation of plate was analyzed. Lastly, the line-track-peening experiment for SUS 304 plate was carried out to evaluate the reasonability of the theoretical analysis model.

Non-Traditional Forming Process of Sheet Metal Based on Laser Shock Waves

Traditional forming process of sheet metal is realized with Die and Mould, this technique lacks flexibility and used in the Volume production. The forming process of sheet metal based on laser shock waves is a novel and developing technique. Laser shock forming (LSF) and Laser peen forming (LPF) are two different forming process of sheet metal, both of them are based on a mechanical effect of shock waves induced by laser. In this paper, after introducing the mechanism of laser shock wave generating, these two forming process and technique feature are analyzed and compared, some research progresses are presented. It is indicated that forming technique based on laser shock waves are of high-flexible and great potential application in the fields of plastic forming of sheet metal.

Finite Element Analysis of the Electromagnetic Field of Untouched Permanent Induction Magnetic Coupling

The magnetic coupling can availably solve the leakiness problems of machine equips. But there is a problem currently in the common synchronous magnetic coupling that the inner rotor magnet steel is demagnetized under high temperature. According to reverse design method, a kind of novel permanent induction magnetic coupling is researched. Its inner rotor is similar to that of asynchronous motor, and it does not need permanent magnet material. So it can be used in both normal and high temperature and is free from transporting medium temperature. Because of the variety of magnetic field, it is extremely complicated. Here the software ANSYS FEM is used to analyze it. Its main process can be divided into three steps: solution preprocess, solution process and solution postprocessing, thus the magnetic field strength value of every point of the coupling can be gotten, and it can be shown conspicuously with the sketches or charts. Then the power and torque also can be solved accordingly.

Numerical Analysis of Electromagnetic Field of Solid Rotor Asynchronous Permanent Magnetic Coupling by Finite Element Method

A new-type of solid rotor asynchronous magnetic coupling which works on the principle of electromagnetic induction is researched by ourselves. This kind of asynchronous magnetic coupling can solve the problem effectively that the permanent magnets on its inner rotor is demagnetized if its temperature is too high, because its inner rotor need not the permanent magnets. in order to study the transmission capability of the new-type magnetic coupling, its magnetic field should be analyzed. Because of its magnetic field variety, it is extremely complicated and a precision result is difficult to be got by the analytic method of the magnetic field calculation. Here the software ANSYS FEM is used to analyze its magnetic field. And some formulas were deduced and used to calculate its torque. The experimental and calculational results indicate that this design is practicable.

Electromagnetic Properties Analysis of Field-Modulated Asynchronous Magnetic Couplings

In order to research the working status of the field-modulated asynchronous magnetic coupling under loading condition, the electromagnetism characteristics such as the distributions of induced current, torque and loss were obtained by using the ANSOFT software to carry on the transient analysis. The results show that the induced current in the whole of magnetic coupling is not evenly distributed. The induced current of copper is maximum, followed by the ferromagnetic pole-pieces. The highest induced current density is in the outside boundary of the copper layer so that the skin effect of current is verified. The current density and loss increases with increasing of the workload, while the torque increases firstly and then decreases with increasing of the workload. When the slip ratio exceeds 12%, the coupling appear skid phenomenon because the loads is greater than the maximum load which the coupling can bear.

The Performance Testing System of Force Motor Valve

Hitachi force motor valve has been widely used in the hydraulic automatic gauge control (AGC) system of rolling mill due to the characteristics of fast response, high control accuracy and strong anti-pollution ability. It is an important part to control the steel production cost by detecting the performance index of the FMV effectively and in real time. Traditional Servo valve test system detects its static characteristics through the flow and pressure changes between the traffic cavity, and this principle can solve the three position four way servo valve performance test. However, FMV is a special three-way valve and it is hard to test its static characteristic curve like three position four way servo valve. This paper proposes a FMV testing method and has realized it. The test platform is designed and built according to the hydraulic valve testing performance index for detecting the performance of a force motor valve. Not only were force motor valve (FMV) performance characteristics tested effectively but also the performance curves were drawn. The results show that the FMV performance testing method we have built can be effectively used to detect the static performance index of FMV.

Magnetic-Field Modulation Principle and Transmission Ratio Calculation of Field-Modulated Asynchronous Magnetic Coupling

A field-modulated asynchronous magnetic coupling is a new type of composite magnetic transmission mechanism, which is based on the principles of magnetic field modulation and electromagnetic induction. The rotational velocity and direction of the inner conductor rotor could be changed, since the magnetic field generated by permanent magnet outer rotor is modulated by ferromagnetic pole-pieces. Therefore, the couplings can meet special conditions with special requirements for load and speed. The formula of the modulated magnetic flux density of inner air gap is analyzed through magnetic field analytic approaches, and then the formula of transmission ratio is also deduced by introducing slip ratio in the mean time. Finally, experimental research of the coupling is conducted. The results show that the transmission ratio of the coupling is not only related to the ratio of the number of pole pairs on outer permanent magnet rotor and the number of pole pairs of magnetic field flux density harmonic, but also related to the slip ratio. Besides, the transmission ratio of the coupling increases non-linearly with the slip ratio.