Advanced Materials Research Vols. 538-541

Abstract: According to the characteristics of laser melt injection, a numerical model for a simplified 3D transient temperature field in molten pool was established using FLUENT software in this paper. In the model, many factors were considered such as liquid metal turbulence, latent heat of phase transformation and material thermo physical properties depending on temperature. The results show that the model can be developed well by FLUENT software. And the results also show that the driving force of the liquid metal flow mechanism.

Abstract: Die-casting plunger often fails due to serious wear on its cylindrical surface. The scrap of plunger used in large die-casting machine results in waste of materials and energy sources, and it is also against environmental protection. Therefore, the laser remanufacturing of die-casting plunger was studied in this paper. Both of the size and the performance of plungers were repaired by laser cladding surface modification using an iron-based self-fluxing alloy. The interface between original failed plunger and laser cladding layer showed a good metallurgical bond. The average thickness of laser cladding layer was 0.845 mm, and the average micro-hardness reached to 750 HV upwards. Microstructure in laser cladding layer was composed by the dendrite primary phase and the ledeburite organization. Iron (Fe), Chromium (Cr) and Molybdenum (Mo) elements were the main chemical compositions measured in laser cladding layer. The service life of laser remanufacturing plunger was nearly the same as the life of new plunger. However, its remanufacturing cost was only 50% of the new plunger’s. The laser remanufacturing technique is worth for extending and applying due to high cost performance.

Abstract: Laser ceramic modification technology is an effective way to improve the surface performance of titanium alloy. This paper summarized the in situ formation mechanism of ceramic phases and the interface structure between ceramic phases and the matrix during the laser ceramic process on the surface of titanium alloy. The future research area was also indicated that theoretical study on composite ceramic coating preparation should be strengthened by combining the laser alloying and in situ formation technology on the surface of titanium alloy.

Abstract: High-power diode lasers based on GaAs semiconductor bars are well established as reliable and highly efficient laser sources. The device structure and stack technology of edge-emitting diode laser were presented briefly as well as the development of electro-optical conversion efficiency ,lifetime , power .The technology of ten-thousand –watt level high power diode laser was introduced as a new generation of laser processing equipment. In order to output high power, we utilized polarization coupling technology to couple two 808nm and 880nm laser diode stack together, and designed the optical system to expand and focus the beam, through the experiment; we realize the overall efficiency more than 90%, power output 1000W.

Abstract: Obtain a prosthesis and carry out maxillofacial repair by rapid prototyping technology on the basis of three dimensional finite element model of maxilla skull and dentition which is obtained through preliminary restoration done on a skull exemplar as modeling material and through spiral CT scanning and three dimensional imaging technologies. Thus, a vivid restored three dimensional biomechanical model and prosthesis of maxilla skull and dentition is obtained, based on which, the form and functions can be restored well after repair. Individual defect model and prosthesis model can be built according to different plans designed for different patients. By which, a complete idea for maxilla and dentition repair can be achieved with pleasing in appearance on patients, low cost and less post-operative complications.

Abstract: In this paper, a temperature field model of 45 steel shafts during the laser quenching was built and simulated by using ANSYS software. Its surface temperature distribution of the shaft during the laser beams scanning was simulated. Their effects of different laser power, laser beams spot size and scan speed on part’s quenching performance were analyzed.

Abstract: The mechanism of healing fatigue damage was investigated by pulsed laser surface irradiation for polycrystalline copper film, X-ray Diffraction(XRD), optical microscopic and scanning electron microscopy(SEM). The results indicate that surface melting and grain refinement were found in the melted surface layer. Tensile residual stresses were introduced in the resolidified surface layer due to laser surface melting which produced deleterious effect on fatigue property. Remelting and grain refinement in the surface layer is mainly responsible for healing fatigue damage and fatigue life improvement. The fatigue damage could be healed completely or partly by laser surface irradiation under the proper parameters of laser treatment for the specimens.

Abstract: There is more difference in the test data of the friction and wear for friction material between the small sample tester and dynamometer, because of the different structure and function. In order to improve the comparability, a kind of new scaling 1:5 for JF122SB dynamometer for the scaling testing based on the parameters of the scaling 1:1 for JF122 dynamometer was developed, according to the similarity principle. In this paper, it is show that the designing principle, the zoom scale, the main parameter and structure of the 1:5 dynamometer. Adopting the same testing standard SAEJ2681, the comparative trial has been done. Analyzing those test data it is proved that there are fine comparability and consistency between the two testers.

Abstract: A 3-dimensional (3D) thermal distribution computational methodology for laser cladding is presented. Based on the developed model, which considers the latent heat and change of conductivity in different phase, the transient temperature fields for the preplaced laser cladding processing are performed. The effect of processing parameters including laser power, scanning speed and laser spot diameter on melt pool temperature filed was extensively discussed and some conclusions were drawn.

Abstract: Laser forming involves heating sheet metal workpiece along a certain path with a defocused laser beam directed irradiate to the surface. During laser forming, a transient temperature fields is caused by the irradiation and travelling of a laser beam. Consequently, thermal expansion and contraction take place, and allows the thermal-mechanical forming of complex shapes. This is a new manufacturing technique that forming metal sheet only by thermal stress. Therefore, the analysis of temperature fields and stress fields are very useful for studying the forming mechanism and controlling the accuracy of laser forming. The non-liner finite element solver, ABAQUS, is employed to solve the thermal-mechanical analysis. Using this model, the temperature and stress distribution of DP980 are analyzed. Numerical results agree well with the experimental results.