Papers by Author: Xiao Ming Zhao

Abstract: Spindle thermal deformation is the main error source of many precision profile grinders. In this paper, the relationship between spindle temperature and either radial or axial thermal deformation is studied based on experiments. The placement and amount of temperature sensors are optimized. Then a kind of thermal error modeling method based on support vector machine is presented and applied in the modeling of thermal error of profile grinding. The result shows the model is robust and the on-line accurate prediction of grinding thermal error is realized based on monitoring of temperature rise of spindle. Finally, the error compensation strategy is discussed for further application of thermal error modeling.

Abstract: Laser rapid forming (LRF) is introduced as a novel fabrication process for Ni-based superalloy Rene88DT. The effect of heat treatment parameters of quenching rate and aging time on size and distribution of γ′ precipitation was investigated. The heat treatment parameters were first determined by DSC, and then optimized based on the examination of the microstructure and mechanical properties of heat treated LRF Rene88DT. The experimental results show that, the precipitation of γ′ is inhomogeneously distributed as a result of uneven heat-cycle during LRF in as-deposited Rene88DT, resulting in low mechanical properties. After being heat treated at 1165°C, 2h/AC + 760°C,28h/AC, γ ′ precipitation are homogeneously distributed with the size of 40~60nm, and the tensile strength of heat treated sample shows an increase of 400MPa as compared to that for as-deposited. The yield strength is close to that of the PM+HIP standard.

Abstract: Laser rapid forming (LRF) is a new manufacturing technology, which has been developed on the basis of multi-layer laser cladding. In the LRF process, the microstructure has important effects on the mechanical properties of the parts
but the control of microstructure is a problem. In this study, the influences of crystallography orientations of substrate and profile of solid/liquid interface on microstructure were discussed. Further, with the combining of the columnar to equiaxed transition (CET) model during alloy solidification, the growth law of microstructure of Rene88DT alloy was established. It has been found that the temperature gradient was lowest and the solidification velocity was greatest at the solid/liquid interface of the tail of molten pool, and hence the CET occurs easily at this position. The temperature measurement system of molten pool was developed by using a two-color infrared thermometer in this study. With the measurement of temperature gradient of the tail of molten pool by using a two-color infrared thermometer, the process parameters of laser multi-layer cladding were optimized. Finally, directional solidification even single crystal was achieved in laser multi-layer cladding.