Ya Dong Gong

Preparation of Porous Multi-Channeled Chitosan Conduits for Nerve Tissue Engineering

A new method to fabricate porous chitosan nerve conduits with multi-channels was described. A uniquely designed mold was composed of 7-50 stainless steel needles and a set of plastic pedestals. Porous or imperforate chitosan tubes with 2-5mm inner diameter and 0.2-1.0 mm wall thickness were made firstly. The chitosan tubes were injected with 3% chitosan gel. The stainless steel needles longitudinally perforated through the chitosan tubes filled with chitosan gel, and the plastic pedestals were used to fix the needles. Lyophilization was used to finish fabrication. The diameter of channels was 0.2-0.4mm. Swelling property and biodegradability of Multi-channeled chitosan conduits were investigated. Wright’s staining and scanning electron microscope (SEM) were used to observe spread and proliferation of Neuroblastoma cells (N2A, mouse) on the conduits. It is promising that the porous chitosan nerve conduits with multi-channels are used as nerve tissue engineering scaffolds in repair of peripheral nerve and spinal cord injuries.

A Micro Milling Model Considering Metal Phases and Minimum Chip Thickness

In this paper, a micro milling model is brought forward. The influences of different metal phases and the minimum chip thickness are considered in the model. The cutting forces and the surface generation in the micro milling process are predicted. Through the experiment validation, the results correlate to the model very well.

A Study on Airflow Field of Super-High Speed Pectination Grinding Wheel Based on PIV

Adopting the method of PIV, systematical theory analysis and experiment research were made on the airflow field distribution of super-high speed pectination grinding wheel, as well as experiment design and data acquisition, the data processing was carried out through the software of FlowMap, Tecplot, and Matlab. By analysis and discussion focused on experiment results, the general rules of airflow field distribution in super-high speed pectination grinding wheel were preliminary drawn, which provides the research foundation with a view to find a new method for the effective supply of super-high speed grinding coolant.

Study on Micro Mill-Grinding Technology

Micro mechanical processing is the effective method for machining micro scale parts. Micro mill-grinding technology is presented based on micro milling and micro grinding processes. The machining principle of micro mill-grinding is studied, and compound tools for micro mill-grinding are fabricated based on spraying technology. Experiments are performed on Al 6061-T6 with the three-dimensional micro machining system. The results show that submicron surface roughness can be obtained by micro mill-grinding. Abrasive grains of mill-grinding tools fabricated by spraying method shed easily. Smaller abrasive particle size improves the surface quality and increases the tool life.

Study on the Effect of Coarse Grinding Area Slope Angle on Surface Quality in Point Grinding

There is a vitrified bond CBN point grinding wheel with coarse grinding area slope angle θ. This new grinding wheel has higher removing rate and better machining accuracy than conventional wheels. The design and manufacture principle of the new grinding wheels are studied in this paper. These wheels with different coarse grinding area slope angle θ are used to grind the stepped shaft of QT700 with a series of grinding parameters.VHX-1000E microscopic system and Micromeasure system are used to measure the surface quality of workpiece. In the same group of grinding parameters, compare the effect of these different wheels on surface roughness. The effect of deflection angle α on surface roughness is generalized.

The Grinding Mechanism on Quick-Point Grinding Wheel Wear and Effects on Surface Quality

A study on the wear of Quick-point grinding wheel was carried on. The wheel wear was found having great influence on grinding performance and grinding quality. After analyzed the wear process and mechanism in Quick-point grinding, it was found the wear rate was directly related to some factors such as wheel width, workpiece speed, feed rate and Quick-point grinding angle, and it was indirectly affected by wheel speed and cutting depth. By means of some wear criteria, the wheel wear was able to be predicted. Furthermore, a wear model in wheel’s accurate area has been built up.

A Micromilling Experimental Study on AISI 4340 Steel

A micromilling experimental study on AISI 4340 steel is conducted to understand the micromilling principle deeply. The experimental results, especially on the surface roughness and cutting force, are discussed in detail. It has been found the minimum chip thickness influences the surface roughness and cutting force greatly. Meanwhile, the material elastic recover induces the increase of the axial micromilling force. The average cutting force and its spectrum analysis validate the minimum chip thickness approximation of AISI 4340 is about 0.35μm.

Theoretical Analysis and Simulation of Airflow of Super High-Speed Grinding Wheel

The airflow field of super-high speed grinding was analyzed in the paper and the method of computing and analyzing the distribution of the field has been brought forward by applying boundary layer theory. Adopting the method of finite element, the model of airflow field in the 3-D grinding zone has been built up by using software; the solving strategy and the boundary conditions has been defined, where artificial viscosity coefficient in the repetitive and continuous analysis and the method by applying inertia relaxation have been discussed, which helped to revolve stability. The results of simulation was given and analyzed, which can be validated with experiment by using the equipment of PIV (particle image of velocity).

Experiment Research on Grinding Temperature of Micro-Grinding H62

The thermocouple temperature measurement method was adopted to measure the surface temperature in micro-grinding experiment. According to the different grinding depth, the appropriate processing parameters were chosen to find out the temperature field distribution on the surface and in different depth of subsurface. It provided a reference basis in order to prevent the grinding burn. It proves that the method combining the finite element theory with experiment method is correct and feasible. It is a basis of the factors of the grinding temperature and surface integrity of the parts. Further more, it is of great significance that grinding mechanism and surface quality improving of the parts be discussed thoroughly.

The Design and Manufacture of Quick-Point Grinding Wheel

It is important that preparing high quality grinding wheel to match Quick-point grinding processing. Using brazed CBN grinding wheel, grains can be combined with wheel matrix in high bonding strength, which is helpful to minimize wheel wear and to gain a good grinding ability. By establishing the connection between stress and its increment, the mechanical properties of wheel under different conditions is described. The wheel speed has effect on wheel matrix displacement and stress. Applying finite element method to optimize wheel structure, a final grinding wheel for Quick-point grinding is obtained.