Papers by Author: Zong De Fang

Abstract: The assembly misalignment is the key factor that influences the meshing performance of gear, the meshing performance worked on no-load or light load conditions is more completely expressed by contact pattern and transmission error. According to the contact pattern and transmission error, the influence of assembly misalignment to the meshing performance of hypoid gear is studied, this method break the limitations relying on experience to adjust the installation. Based on the machining principle and method of Gleason hypoid gears which machined by the HGT method, the mathematical model of machining was established, and the theoretical tooth surface equations were derived, on this basis, the hypoid gear as an example, the tooth contact analysis (TCA) was carried out considering assembly misalignment, the conclusion was drew that the influence to the position of tooth surface contact area and the magnitude of transmission errors are different when the Assembly misalignment affecting alone. This can offer certain reference for the installation and adjustment of hypoid gear pair in engineering practice.

Abstract: Tractor SX4187NT361K, which is manufactured by the Shaanxi Automobile Group Limited Corporation, is regarded as a prototype vehicle. This paper investigates an 1/4 car model with air springs for the tractor and a working model of air spring. A height PID control method for ECAS is designed, and its digital simulation is conducted. An ECAS test-bed is designed, and hardware of a measurement and control system for the test-bed is designed with DSPACE system, its softwares are also designed with Simulink and ControlDesk. Finally, active and passive tests of the ECAS are conducted through changing frequencies and desired heights, simulation and test results show that the PID height control method for ECAS is feasible.

Abstract: Considering the gap of the contact line of modified involute cylindrical gears influencing on loads, oil film thickness, the friction coefficient was determined on the basis theory of TCA、 LTCA and EHL. so oil film thickness and friction coefficient corresponded with loads on contact line were dispersed, which was used to computed discrete temperature according to the Blok flash temperature formula. and an approach of modified tooth surface optimum design based on the minimum flash temperature was proposed: the modified tooth surfaces was defined as a sum of theoretical tooth and cubic B-spline fit surface based on the uniform grid points created by double parabolas and a straight line and whose normal vector was deduced, besides, used genetic algorithm to optimize the parameter of curve, and get the best modified gear tooth surfaces. the results shows that oil film is thicker in engaging-out, coefficient of friction is contrary, which is responsible for lower flash temperature in engaging-in, besides the flash temperature has little changes in the single tooth meshing zone, and helical gear has a lower flash temperature than spur gear due to higher overlap ratio.

Abstract: Usually the gear modification is a main measure to reduce the vibration and noise of the gears, but in view of the complexity of the gear modification, topology optimization method was used to optimize the structure of the gear. The minimum volume was set as the direct optimization goal. To achieve the target of reducing contact stress, tooth root bending stress and improving flexibility, the upper bound of the stress and lower bound of the flexibility were set appropriately, thus realizing multi-objective optimization indirectly. A method for converting topology result into parametric CAD model which can be modified was presented, by fitting the topology result with simple straight lines and arcs, the model can be smoothed automatically, after further regulating, the geometry reconstruction was finished. After topology optimization, the resulting structure and properties of the gear are consistent with cavity gear. While reducing the weight of the gear, the noise can be reduced and its life would be extended through increasing flexibility and reducing tooth root stress.

Abstract: In order to further reduce sensitivity to misalignments not only double crowned pinion but also profile and longitudinal geometry modified face gear have been studied. The profile geometry modification were realized by application of rack cutters, and applied parabolic motion of the center of grinding disk for the pinion and face gear longitudinal crowning. Tooth contact analysis (TAC) and Load Tooth contact analysis (LTCA) have been performed to simulate the meshing and contact of double-crowned face gear driver. The further avoidance of edge contact in presence of big magnitude misalignment was illustrated with numerical examples.

Abstract: Comprehensive meshing stiffness and single tooth meshing stiffness are calculated by tooth contact analysis and load tooth contact analysis program. The corner meshing impact model is proposed. Nonlinear dynamic model of helical gear transmission system is established in this paper considering time-varying meshing stiffness excitation, transmission error excitation, corner meshing impact excitation, and the backlash excitation. Take the ship’s helical gear transmission system as an example, the mesh impact force is derived and the primary factors that produce noises are discussed. The effects which the mesh impact brings to vibration characteristics of the gear dynamic system are concluded. Meshing impact has an inevitable effect on the vibration of the dynamic system. Impact excitation costs 8.5% in maximum of vibration acceleration response, 31% in maximum of instantaneous acceleration, and 4.9% in maximum of spectral component amplitude.

Abstract: Spherical gears with helix tooth traces are proposed to enhance loaded capacity and improve the sensitivity to assembly errors. The hobbing process for spherical gears is illustrated, and then developed the mathematical model of imaginary rack cutter. The tooth surface mode of spherical gears was developed by coordinate translation and gearing theory. Finally, the paper presents a numerical example to validate the proposed new spherical gears drive

Abstract: Obstacle negotiation capability is important to a mobile robot. A wheel-legged robot with symmetrical structure was presented It has four independent wheel-legged articulations which can generate a series of conFigureurations to improve its trafficability. The obstacle negotiation capability of the robot was studied. Its step-climbing process was described, and the geometrical and dynamic model for the process was built. Based on comprehensively considering geometrical and dynamic constraints, the method to work out the maximal step height that the robot can get across was brought forward. Then the method to work out the maximal slope angle was also provided. Finally the experiment to verify the above methods was done. The research mentioned above would provide a theoretical foundation to improve the robot’s adaptability in complicated environments.

Abstract: Taking the composite rubber suspension of a 6×4 heavy vehicle as research object, an accurate finite element model for the composite suspension at loading states is firstly built with consideration of nonlinear contact between spring leaves, and then a new finite element approach for calculating and analyzing static mechanical properties of the composite rubber suspension. Finally, the stress distribution and deformation is analyzed under different loads by using Hypermesh software and the results can be applied to its strength design. And moreover, some primary principles of the composite rubber suspension stiffness and displacement changing with different loads are obtained, which provides reference basis for virtual design and lightweight design of the vehicle composite rubber suspension.

Abstract: Based on non-smooth impact theory, the dynamic model of spiral bevel gear is constructed by considering of input shaft angle excitation. The Maximal Lyapunov Exponents (MLEs) curves for backlash 0.10mm and 0.14mm caused by exciting amplitude are given. The simulation results indicate that gear backlash, excited amplitude and retard torque have influence on the dynamics behavior of spiral bevel gear system. The experiments show that the vibration noise is deduced after ultrasonic gear lapping.