Processing Simulation of Virtual Manufacture in Laser Surface Treatmenthang

Processing simulation is at the bottom of the coral technology of VM and is also difficult due to the complexity of mechanism and diversity of parameters. Previously much research has been mainly carried out on the geometrical simulation or physical simulation respectively. The aim of this paper is to study the processing simulation in laser surface treatment based on the mechanism, put forward the architecture of the whole processing simulation and give the models of the processing. As a result the data structure layers in the whole simulation is presented.

The Intelligent Measuring Sub-System in the Computer Integrated and Flexible Laser Processing System

Based on the computer integrated and flexible laser processing system, develop the intelligent measuring sub-system. A novel model has been built to compensate the deviations of the main frame, a new-developed 3-D laser tracker system is applied to adjust the accuracy of the system. Analyzing the characteristic of all kinds of automobile dies, which is the main processing object of the laser processing system, classify the types of the surface and border needed to be measured and be processed. According to different types of surface and border, develop 2-D adaptive measuring method based on B?zier curve and 3-D adaptive measuring method based on spline curve. During the data processing, a new 3-D probe compensation method has been described in details. Some measuring experiments and laser processing experiments are carried out to testify the methods. All the methods have been applied in the computer integrated and flexible laser processing system invented by the Institute of Mechanics, CAS.

Microstructure Evolution of Laser Pulse processed Ductile Iron Surface

Pulsed laser beam was used to modify surface processing for ductile iron. The microstructures of processed specimen were observed using optical microscope (OM). Nanoindentation and micro-hardness of microstructures were measured from surface to inner of sample. The experimental results show that, modification zone is consisted of light melted zone, phase transformation hardening area and transient area. The light melt area is made up of coarse dendrite crystalline with a thickness less than 20um, phase transformation hardening area mainly of laminal or acicular martensite, retained austenite and graphite, i.e. M+A prime+ G. The cow-eye microstructure around graphite sphere always is formed in phase transformation hardening area zone, which consisting of a variety structure with the distance from the surface. So, it maybe as a obvious sign distinguishing modification zone border. Finally, the microstructures evolution of laser pulse processed ductile iron was analyzed coupling with beam energy distribution in space and laser pulse heating procession characteristics. The analysis shows that energy distribution of laser pulse has an important effect on microstructure during laser pulse modified ductile iron. Multi-scale and interlace arrangement are the important features for laser pulse modified ductile iron. Of microstructure.

Investigation on the Interaction of Laser Beam and Metal Powders Conveyed by Coaxial Powder Feeder

In order to investigate the transient thermal stress field in wall-shape metal part during laser direct forming, a FEM model basing on ANSYS is established, and its algorithm is also dealt with. Calculation results show that while the wall-shape metal part is being deposited, in X direction, the thermal stress in the top layer of the wall-shape metal part is tensile stress and in the inner of the wall-shape metal part is compressive stress. The reason causing above-mentioned thermal stress status in the wall-shape metal part is illustrated, and the influence of the time and the processing parameters on the thermal stress field in wall-shape metal part is also studied. The calculation results are consistent with experimental results in tendency.

Research on Q-Switched Nd : YAG laser engraving

IN this paper, the engraving process with Q-Switched Nd:YAG laser is investigated. High power density is the pre- requisition to vapor materials, and high repetition rate makes the engraving process highly efficient. An acousto- optic Q-Switch is applied in the cavity of CW 200 W Nd:YAG laser to achieve the high peak power density and the high pulse repetition rate. Different shape craters are formed in a patterned structure on the material surface when the laser beam irradiates on it by controlling power density, pulse repetition rate, pulse quantity and pulse interval. In addition, assisting oxygen gas is used for not only improving combustion to deepen the craters but also removing the plasma that generated on the top of craters. Off-focus length classified as negative and positive has a substantial effect on crater diameters. According to the message of rotating angle positions from material to be engraved and the information of graph pixels from computer, a special graph is imparted to the material by integrating the Q- Switched Nd:YAG laser with the computer graph manipulation and the numerically controlled worktable. The crater diameter depends on laser beam divergence and laser focal length. The crater diameter changes from 50 micrometers to 300 micrometers , and the maximum of crater depth reaches one millimeter.

Numerical Study of Heat Transfer Mechanism in Turbulent Supercritical CO2 Channel Flow

Direct numerical simulation (DNS) of supercritical CO2 turbulent channel flow has been performed to investigate the heat transfer mechanism of supercritical fluid. In the present DNS, full compressible Navier-Stokes equations and Peng-Robison state equation are solved. Due to effects of the mean density variation in the wall normal direction, mean velocity in the cooling region becomes high compared with that in the heating region. The mean width between high-and low-speed streaks near the wall decreases in the cooling region, which means that turbulence in the cooling region is enhanced and lots of fine scale eddies are created due to the local high Reynolds number effects. From the turbulent kinetic energy budget, it is found that compressibility effects related with pressure fluctuation and dilatation of velocity fluctuation can be ignored even for supercritical condition. However, the effect of density fluctuation on turbulent kinetic energy cannot be ignored. In the cooling region, low kinematic viscosity and high thermal conductivity in the low speed streaks modify fine scale structure and turbulent transport of temperature, which results in high Nusselt number in the cooling condition of the supercritical CO2.

Combined Fluorescent-Chromogenic In Situ Hybridization for Identification and Laser Microdissection of Interphase Chromosomes

Chromosome territories constitute the most conspicuous feature of nuclear architecture, and they exhibit non-random distribution patterns in the interphase nucleus. We observed that in cell nuclei from humans with Down Syndrome two chromosomes 21 frequently localize proximal to one another and distant from the third chromosome. To systematically investigate whether the proximally positioned chromosomes were always the same in all cells, we developed an approach consisting of sequential FISH and CISH combined with laser-microdissection of chromosomes from the interphase nucleus and followed by subsequent chromosome identification by microsatellite allele genotyping. This approach identified proximally positioned chromosomes from cultured cells, and the analysis showed that the identity of the chromosomes proximally positioned varies. However, the data suggest that there may be a tendency of the same chromosomes to be positioned close to each other in the interphase nucleus of trisomic cells. The protocol described here represents a powerful new method for genome analysis