Papers by Author: Li Li Liu

Abstract: The simulation method for ARB(accumulative roll bonding) and the constitutive model of the ARB specimen were studied. Based on the ZA(Zerilli-Armstrong) model, with MSG(mechanism-based strain gradient) theory and Hall-petch principle, considering its temperature, strain ratio and the effect of the texture variation to the mechanical property, its dynamic constitutive model was established, and verified through the experiment. Moreover, the finite element simulation method for ARB process based on the dynamic constitutive model established was proposed and verified through the experiment. The study in the paper provides analysis method and theory foundation for ARB

Abstract: Study on the effect of the surface manufacturing quality (roughness) to the friction between the surfaces. Based on the plastic theory of mechanism-based strain gradient (MSG) of the micro-plastic-mechanics and the contact theory, the theoretical model of the coefficient of friction between the rough surfaces and the non-linear finite element model between the grinding samples were established. Moreover, the surface stress distribution and the coefficient of friction were obtained through the sub-structure finite element method. The established model of static friction theoretical model and the accuracy of the finite element model were verified through comparing with the result of the static friction experiments between the grinding samples with different surface manufacturing quality. The study in the paper is important to the study on the surface friction mechanism.

Abstract: Idea of functionally gradient material (FGM) theory was used to the design of ceramic nozzle. The purpose was to increase the erosion wear resistance at the entrance of the nozzle in dry sand blasting processes. The SiC/(W,Ti)C gradient ceramic nozzles fabricated by conventional hot pressing. The erosion behavior of the SiC/(W,Ti)C gradient ceramic nozzles were investigated in comparison with the common homologous ceramic nozzles. The experimental results have shown that the ceramic nozzles with a gradient structure have superior erosion wear resistance to that of the common homologous ceramic nozzles under the same test conditions. It was shown that the mechanical properties of the gradient ceramic nozzle materials were greatly improved in comparison with that of the common homologous nozzles. The surface Vickers hardness and indentation fracture toughness of gradient ceramic nozzle were greatly improved compared with that of the common homologous nozzles. Therefore, it is indicated that gradient structures in ceramic nozzles is an effective way to improve the erosion wear resistance of the common homologous nozzles.

Abstract: The stress states of the ceramic nozzle in abrasive jet machining (AJM) process are analyzed. Results shown that the maximum stress appears in entrance area of the nozzle and minimum stress in middle area, while the stress of exit area was lower than entrance area and higher than middle area. It can interprets why the entrance and exit area of the nozzle were worn badly. The idea of functionally gradient material (FGM) theory was used to design of ceramic nozzle. The purpose was to reduce the stresses at the entrance and exit area of the nozzle during AJM processes. The physical, composition distribution, and property parameter models of the FGM nozzle were established.

Abstract: With the advantage of Case-Based Reasoning (CBR), selection method about matching of cutting tools with workpiece materials is presented through establishing the matching knowledge and rules in such respects as mechanical, physical and chemical properties of cutting and workpiece materials. Intelligent matching system of cutting tools with workpiece materials is developed based on CBR. This system has such advantages as higher matching speed and better accuracy, which offers a strong support tool for material selection between the cutter and workpiece.