Papers by Author: Jun Pi

Abstract: The technology of composite light trapping film with smooth surface crystalline silicon is presented as an effective measure to enhance the absorptivity of silicon solar cell based on macrostructure at the interface of film.Genetic algorithm,which can be applied for multi-objective optimization,is used to optimize the microstructure of light trapping film.The reflection of smooth surface crystalline silicon is minimized to under 8%,resulting in a remarkable enhancement of initial efficiency for silicon solar cell.

Abstract: The impact of cutter against the materials can be regarded as the rigid ball with certain energy oblique impact against the semi infinite space in the ultrasonic vibration cutting process. The cutter and materials three-dimensional surface stress state was theoretically deduced from building the dynamic shock model in Hertz contact state. Ultrasonic vibration cutting in the tiny cutting depth can be regarded as the contact extrusion process of blunt pressure head oblique impact on materials, the material indentation and crack development trend was given based on the surface stress analysis and test results of rigid ball oblique impact on the glass. The indentation and crack development of spherical pressure head oblique impact on the brittle materials was analyzed, material failure in the back edge with deeper crack is controlled by tensile stress, the tensile stress values depend on the friction coefficient and the normal pressure, material failure crack caused by shear stress on both sides exist on the material surface. Ultrasonic vibration can reduce normal pressure and crack to come into being. Cutting fluid lubricating can reduce the friction coefficient to control with only shallow crack produced in the cutting process.

Abstract: Contactless inductive power transfer system with conventional inductive technology was studied and a design method was presented after applying it to ultrasonic vibration machining systems. The compensation techniques are used for piezoelectricity transducer. Nodal plane support of transducer is researched and models of different structures for nodal plane support are got. Influence of rotary precision for different support due to centrifugal force and displacement vibration of nodal plane support to toolholder are analyzed. The system integrated with ultrasonic-vibration toolholder based on contactless inductive power transfer is designed. Power transfer and dynamic tests show that the design procedures and result based on theoretical analysis are comparative.

Abstract: Rotary ultrasonic machining (RUM) is considered as an effective machining method, which has been utilized to machine hard and brittle materials such as advanced ceramics. In order to improve the hole wall surface quality during RUM, it is important to wash away swarf in the gap between the tool and the workpiece as fast as possible. In this paper, a new machine process – intermittent rotary ultrasonic machining (IRUM) – is introduced for the first time. The cutting force, surface roughness and coolant flow rate in conventional rotary ultrasonic machining (CRUM) process and IRUM process are compared. It is found that compared with CRUM, the output coolant flow rate could be increased significantly by using the IRUM method. It is also found that the surface roughness of workpiece can be improved significantly in IRUM.