Li Jun Yang

Finite-Element Analysis and Optimization for Gradient Porous Structure of Artificial Bone

The loading force of the artificial bone implanted into the human body and the flowing, growth and deposition of cells were influenced by the gradient porous structure. The software of ANSYS Workbench was used in the paper for the stress and strain analysis of the gradient porous structure of the established 3D artificial bone. The variation of the maximum equivalent stress and maximum equivalent strain and elastic modulus changed through the changing of the loading force and porosity. Basis on meeting the mechanical properties, the porosity was used as the index for the optimization of the porous structure of the artificial bone. And it also laid the foundation for the subsequent laser sintering.

Design and Optimization of Technology and Structure Parameters for Sheet Metal Drawing by Orthogonal Experiment

The deformability of sheet metal drawing is influenced by many technology and die structure parameters. By orthogonal experiment, the main four factors effected the deformability of sheet metal drawing have been studied in the two-stage drawing respectively. The results have shown the influencing order and optimum parameters of key factors were varied in different multi-stage sheet metal drawing. The influencing order of the four factors in the first drawing was the blank-holder force > dies radius>the lubricants>the punch-nose radius. The second drawing was dies radius>the lubricants>the punch-nose radius >blank-holder force. The optimum technology and structure parameters have been also determined by the experiments in the paper.

Analysis of the Corner Error in WEDM

This paper introduced some current researches on the corner error in WEDM and put forward the factors that have an influence on the corner error. The deflection of the wire-electrode that has been caused by discharge force, feeding directions of the wire-electrode and radial flops of the guide pulley was analyzed in detail. To minimize corner errors, the energy control strategy and the trace control strategy are presented. Especially in WEDM-HS processing, the methods improving the processing precision are given as follows: Using the over-cutting and retract program, controlling the wire-electrode tension and improving the guiding and allocation parts.

Properties of TiAl/TiAlN/TiAlCN Films Deposited by Arc Ion Plating on GCr15 Rings

Ring is one of the major textile spinning machine consumable part, it has an important influence on yarn quality and cost. Ring of domestic cotton spinning enterprises generally has poor hardness, bad accuracy, not durable and difficult to guarantee the quality of the yarn, foreign ring has excellent performance, but it is too expensive, so it is difficult to widely used in China[1]. Vacuum arc ion plating technology has a wide range of applications in the aerospace, automobile, mold, tool, electronics and other fields [2-3]. TiN film which is prepared by arc ion plating technology has been widely used because of the TiN film has poor oxidation resistance and wear resistance at high temperatures, so the ternary films are developed on TiN film, such as TiAlN [4], TiCN etc. Traveller circle in the ring on the slide to produce large amounts of heat, it makes the ring surface temperature reach 400°C. When higher than 400°C, the TiCN film failure, therefore, ring should not be plated on the TiCN films. While TiAlN film oxidation temperature reaches 800°C. In HSS twist drill, depositing of TiAlN film can improve the service life more than four times [5]. Studies [6-8] have found that using pulsed laser deposition and chemical vapor deposition technique to prepare TiAlCN film, its wear resistance, high temperature stability is better. Pulsed laser deposition is mainly used in laboratory research. It is difficult to deposit a large area uniform film. Chemical vapor deposition of deposition rate is less than the arc ion plating, and produces lots of waste gas, leading to the environment is polluted. Arc ion plating technology can deposit the uniform films of large area with high deposition rate and deposition with no environmental pollution, therefore, this study, by means of vacuum arc ion plating technology to prepare high-precision, long-life and low-cost domestic cotton spinning ring. In order to obtain the best film process parameters, the performance of film is investigated at different bias and arc current.

Research of Porous Ti/HA Bio-Composite Fabricated by Powder Metallurgical Method

The porous Ti-HA bio-composite was fabricated by powder metallurgical method with use of hydroxyapatite powder, Ti-6Al-4V powder and ammonium bicarbonate (NH4HCO3) powder. The experiment was aimed to explore the preparation process and to study the microstructure and mechanical property. As molding pressure increased, the compressive strength of material increased while the porosity decreased. As NH4HCO3 content increased, the compressive strength decreased, but the porosity increased. The results showed that NH4HCO3 content was 20wt%-30wt%, the porosity distribution was 30% to 50%, the compressive strength was higher than 20MPa and the pore size distribution was 100-500μm. This porous composite was suitable for bone repair material of human cancellous bone.

The Technology and Application for 3D Modeling of Bionic Individualized Artificial Bone Outline

Human bone should be individualized modeled and manufactured because of its complex shapes and individual differences. Based on CT tomography images, defect human bone outline was individualized modeled. The technologies of computer image-processing techniques, computer graphics and computer aided geometric design were used in the paper. Also the software of MIMICS was used for medical image-processing. The softwares of Geomagic Studio and UG were used to realize 3D modeling of individualized artificial bone outline and solid modeling in the technology. The results showed that the 3D model met the requests completely, and provided a foundation for the following individualized manufacturing.

Study of the Transmission System of Spreading Powder Device of Direct Metal Sintering Rapid Prototyping Machine

Direct metal sintering rapid prototyping mechanism is complex, including many kinds of transmission systems. Spreading powder device is important to direct metal sintering rapid prototyping mechanism. Based on grasping the working principle of the device, through the study of spreading powder device of direct metal rapid prototyping machine, grasp the process of spreading powder and the main structure of the device, and fabricate the simple model of the transmission system. In order to determine the necessary condition of how the spreading powder device functions, the dynamic parameters of the transmission system must be calculated, and the operation performance of the stepper motor must be checked. Then the precision and the processing quality of the finished part can be improved.

Finite Element Modelling For Internal Bionic Architecture Optimization Of Artificial Human Bones

Clinical medicine shows that the scaffold of artificial human bone must have a certain porosity, good connectivity and adequate mechanical strength. Controlled porosity, pore size, shape and interconnectivity of the scaffold heavily influence the structural strength, transport properties, and the micro-environment for cells and tissue in-growth. In this paper, finite element analysis software was used. A micro-porous unit with mechanical properties similar to the natural bone was produced. Then the interconnected scaffold of tissue with a specific porosity and gradient pore was built according to the optimized micro-porous unit. It was confirmed that the porosity and elastic modulus of the mold were within the bounds of human bone. Analysis using ADINA8.3 ensured that the mold had satisfactory mechanical properties of bone. Finally, STL files were generated by the software and the mold was manufactured using SLS.

A Study on Novel Gas Atomization Device for Preparing Ultra Fine Metal Powder

On the basis of technologies of gas atomization, supersonic gas atomization, surface effect of electric charge and jet, we design a new-style device of two fluids atomization with the combination of solid atomization and electric field utilizing a LAVAL nozzle, a delivery tube of sectional type and the electrical field dispersion technique. The soldering tin of 63 A was atomized with the air, and the powder prepared was analyzed by optical granularity analyzer, nanometer magnetic particles and Zeta potential analyzer. The results show that the particle size with less than 8μm can reach 75%; the average particle size is 1.7612μm, and the first peak in the distribution curve is about 500 nm, which is an order of magnitude smaller than that the existing reported peak. The compound atomization device can refine the particle size of powers effectively, improve uniformity, yielding rate, and the purity of atomized powders and has a significant effect on atomizing, thus provides powerful supports for preparing ultra fine metal powders with high efficiency and low energy consumption and has a good prospect in application.

Design of Vacuum System of Steam Jet Bursting Unit for Chestnut Shell

According to the vacuum bursting process for fresh chestnut shell and requirements for relevant vacuum system, a vacuum system of steam jet pump was designed with a start-up jet pump attached to it. Of which the waste gas from ejector was used for reheating in the bursting process to lead the vacuum bursting unit to run more reliably and stably with efficiency improved and energy consumption reduced. The rate of bursting came up to 95% in the process test.