Papers by Author: Jian She Zhao

Abstract: In order to investigate the mechanical effects during pulsed laser and metal target in neutral solution, a measuring part of stainless cantilever was developed. The vibration of the stainless cantilever was tested and analyzed based on the test mechanism of piezoelectric accelerometer. The impact pressure of the target in NaNO3 solution by pulsed lasers at wavelength of 532nm and 1064nm with millisecond pulse duration were obtained by the test with the measuring part. The results show that mechanical effect during pulsed laser and stainless target interaction in neutral solution is more than three times higher than in air. The pressure of the target with infrared laser is decreased with the distance of laser propagation in neutral solution. However, the effect with green laser is stable in the laser transmission range of 20mm. The green laser is more suitable for processing under neutral solution.

Abstract: Laser beam machining is often associated with the metallurgical defects related with spatter, recast layer and heat-affected zone. In order to overcome the defects, this paper presents a process of jet electrochemical machining and guided laser beam machining (JECM-GLBM). On the explain of experimental principle and apparatus, jet electrochemical machining and laser beam machining(JECM-LBM) and JECM-GLBM experiments have been performed on 0.5mm thick 321S20 stainless steel under the same experimental condition respectively. The experimental results show that the entry circularity, repeatability and the surface quality of JECM-GLBM are significantly better than JECM-LBM, and the spatter and the recast layer of hole-wall has been mostly removed in JECM-GLBM. In addition, increasing the IEG leads that the taper and overcut are decreased in JECM-GLBM. By analyzing the experimental results, the best IEG is 10mm, which is unusually beneficial for the design of equipment in engineering application.

Abstract: For the difficulties of machining small hole on difficult-to-cut materials, a study of hole-making technology by pulsed electrolyte jet machining is carried out. Main effects of DC power and pulse power on the hole conicity, surface quality and drilling efficiency are studied in this paper. The experiment results show that: hole with high surface quality can be available and the hole conicity is effectively reduced by using pulsed electrolyte jet machining; DC is suitable for improving efficiency when the ECM voltage is less than 300V, while pulse power supply shall be adopted to achieve good surface quality and high drilling efficiency when the ECM voltage is more than 300V.

Abstract: Jet Electrolytic Drilling (JED) is a micro-hole drilling process, which employs a jet of electrolyte for anodic dissolution of workpiece material and does not require entry of a nozzle into the machined hole. JED has been used for drilling small holes in aerospace, electronic, and micro-mechanics. One of the most significant problems on JED is the precise control and parameters optimization of the process. This paper established a two-dimension mathematical model for JED to describe the shape of the drilled hole. The model was validated by comparison of simulation and experimental result. JED experiments were performed on 0.6mm thickness stainless steel sheets with different parameters including nozzle diameter and operating voltage. It is found that JED is suitable for drilling micro-holes with diameter less than 1mm and the operating voltage should better be more than 120V.

Abstract: In order to predicate machined shape of electrochemical machining (ECM), a machined shape prediction method by using numerical simulation is presented in this paper. For the simulation, the mathematical model based on electric field and flow field theories firstly is built. Then the time discretization method and the finite element method (FEM) are employed to solve the mathematical model. The simulation software is developed to perform the simulation of the ECM process and predict the machined shape. Finally the method is applied in the ECM processes of the blade and the cavity. The application results show that the machined surface with high accuracy can be achieved and less test times is needed by the simulation.

Abstract: Recast layer is an inherent defect commonly associated with holes produced with laser drilling. The defect is likely to limit the extent of aero industrial application. In order to solve the problem, a new processing of laser drilling assisted with neutral salt solution (SALD) has been developed to improve the overall quality of laser-drilled holes. The process bases on the application of a fluid neutral salt solution, which is being on the workpiece surface with the focused laser beam at the same time. The effects of the neutral salt solution during the process mostly consist of thermal chemical reaction and continuing cooling effect of materials. Because of green laser being weakly absorbed underwater, the experiments of SALD have been performed on 0.5mm thickness 321 stainless steel with pulsed Nd:YAG laser at second harmonic wavelength. The optical microscope is used to detect the experimental results. It is found that the recast layer has been effectively removed during the SALD compared with laser drilling in ambient atmosphere conditions. It is confirmed that the principle of SALD is right and the new process can obtain good hole quality without recast layer.

Abstract: At present, the rimed integral impeller is machined mainly by NC-electro-discharge machining (NC-EDM). To raise the efficiency of EDM process, the pre-channel is machined by NC-ECM to replace NC-EDM in rough machining process. The experimental results indicate that the whole process efficiency can be improved by not less than 20%, but the design of cathode and its feeding path in NC-ECM is a skilled and costly work. To improve machining accuracy and simplify design process, a new design approach based on simulating the shaping process of NC-ECM was put forward to design the cathode and its feeding path.