Papers by Author: Xia Ji

Abstract: Surface integrity, such as surface roughness and residual stress, is an aspect of surface quality on machined parts. Residual stress in the machined surface and subsurface is affected by materials, machining conditions, and tool geometry. These residual stresses could affect the service qualify and component life significantly. Residual stress can be determined by empirical or numerical experiments for selected configurations, even if both are expensive procedures. This paper presents a hybrid neural network that is trained using Simulated Annealing (SA) and Levenberg-Marquardt Algorithm (LM) in order to predict the values of residual stresses in cutting and radial direction after the MQL face turning process accurately. To verify the performance of the proposed approach, the predicted results are compared with the results obtained by training an ANN using SA and LM separately. The results have shown that the hybrid neural network outperforms SA and LM in predicting machining induced surface integrity that is critical to determine the fatigue life of the components.

Abstract: This paper presents an analytical approach to predict the machining force, temperature and residual stress under minimum quantity lubrication (MQL) condition. Both the lubrication and cooling effects are considered to change the tribological and thermal properties in the modified Oxleys model, which is capable to predict the cutting force and temperature in MQL machining directly from cutting conditions. The machining-induced residual stress is predicted by modified McDowell hybrid algorithm. The predicted cutting forces and residual stresses are verified by orthogonal cutting tests for C45 steel and TC4 alloy steel.

Abstract: The optimization of processing parameters for laser cladding process based on Statistical Analysis System (SAS) software was investigated and the experimental investigation on Ni-based alloy components fabricated by laser cladding was carried out. The influences of the main processing parameters on the surface quality were analyzed, and the Ni-based components with superior surface quality were obtained by employing the optimum set of parameters. The surface morphology and microstructure of the components were analyzed. Results indicate that the surface of the cladding is rather smooth and the claddings have a unique microstructure consisting of primary dendrite. The laser cladding layer with integrated melt interface and without reheat cracking can be obtained by optimizing the process variables. The investigations show that the components fabricated by laser cladding process have better mechanical properties than that of the conventional manufacturing technology.

Abstract: This paper presents an experimental investigation on the metal components fabricated by laser cladding. In the present study, two process of laser cladding were conducted, that is pre-placed powder cladding and coaxial powder-feed cladding. The effect of processing parameters was studied and optimum set of parameters for the superior surface quality was established by employing the orthogonal design. The fabricated components were subjected to metallographic examinations and micro-hardness measurement. Results indicated that the microstructure of coaxial cladding components was finer than pre-placed powder cladding components. The micro-hardness of the fabricated specimen along and vertical the scanning direction were measured using a HVS-1000 micro-hardness tester with a 200 g applied load. Analysis of the physical properties provided further evidence of differences in micro-hardness produced by different process conditions, and the average micro-hardness value of pre-placed power cladding layer was lower than the coaxial powder-feed cladding layer.

Abstract: The laser peen forming (LPF) uses high-power pulsed laser beam replacing the tiny medium balls to peen the surface of plate and generate compressive stress near the surface, the metals respond to this residual stresses by elongating at the peened surface and effectively bend the overall shape. In this paper, the deforming process of metal plate induced by repetitive pulsed laser was discussed from theory firstly, and the bending mechanism of LPF was investigated. Then a mathematical model of bending curvature concerning the depth of residual stress was presented, the influence of residual stresses on the deformation of plate was analyzed. Lastly, the line-track-peening experiment for SUS 304 plate was carried out to evaluate the reasonability of the theoretical analysis model.