Papers by Author: Geng Liu

Abstract: Property of transmission system will directly influence the performance and reliability of helicopters. Information exchange and sharing are difficult in transmission system life-cycle, which has complex product to fabricate and mass information to handle. To solve this problem, we establish a unified product data (UPD) to manage the information of research-development process for transmission system. In distributed collaborative environment, a single enterprise UPD is established by analysing transmission system development process and data flow. The theoretical frame of UPD and several key techniques are studied, including architecture, model, management, consistency, and mapping of data access control. Data integration and data access control model in development process is discussed in this paper. A UPD integration framework based on collaborative agent is presented, which shows the evolvement theory among PUPD, DUPD, SUPD and IUPD. Besides, task-role-based access control model is proposed, and dynamic right control process is given for UPD.

Abstract: Business process and professional simulation process are closely relative and alternate together for complex product simulation. This paper presents a business-task coupled process management method, which can implement integration management of business process and professional simulation process. Business-task coupled process is controlled by a multilayer workflow engine based on workflow technology. When the business process executes a task activity, the responding task process will be driven. The workflow engine controls every simulation activity in the task process. A simulation activity invokes one specified simulation tool and transfers data through a simulation component. The application result shows the validity of the method.

Abstract: Based on the current study of planetary roller screw(PRS), a summary of how to match the main parameters of the PRS is obtained. A mathematic model for contact analysis is developed, where series of equivalent balls are used to replace the rounded profile of the roller. At the same time, the formula of axial contact deformation of the PRS is derived. Then a simplified finite element model of the PRS is established and the contact analysis is conducted by FEA. The FEA results and the theoretical ones agree well with each other, so the accuracy of the calculation method and the validity of the equivalent method are verified.

Abstract: Coupled molecular dynamics simulation and finite element method, a multiscale method is used to model nanoscale sliding contacts problems. According to an experimental sample, 4 textured surfaces with different asperity shapes are designed. Through the friction forces comparisons between smooth surface and textured surfaces, the effects of texture shapes are investigated, and 2 better textured surfaces are discovered to reduce friction forces.

Abstract: Based on the meshing principle of Planetary Roller Screw (PRS), the meshing clearance of screw pair is minimized by taking the half of thread angle, and the pitch diameter tooth thickness, e, as the optimization variables. Optimal structural parameters are obtained by using optimization module of the software Matlab. The 3D model of PRS structures are established with Solidworks and the finite element contact analysis is carried out with Ansys. The contact deformation and stress distribution are calculated among screw, rollers and nut. The results can be used for PRS design.

Abstract: The common definition of vibration influence chart is proposed in this study. A 46 degree-of-freedom time-varying dynamic model with coupled translation-rotation effect is developed to simulate the vibration of an encased differential planetary gear system using lumped mass method. With the dynamic load and the acceleration on gears and bearings as references, the dynamic responses in different load cases are investigated to search the change law of concerned parameters. The parameters considered include mesh stiffness, structure stiffness, gear mass and moment of inertia. The good and poor regions for vibration are evidently presented in figures, which is convenient to conduct the parameters design of planetary gear systems.

Abstract: Based on analyzing the mechanism of load sharing of power-split planetary gear trains, equivalent mesh errors are defined and introduced in this paper to take the deformations and manufacturing and assembling errors into account. The static equilibrium equation of planetary gear trains is established. Then the load sharing coefficients of a power-split planetary gear system are calculated. The results indicate that the load sharing of power input stage is worse than that of the power output stage in the power-split planetary gear system.

Abstract: Planetary gear trains have many advantages in applications. In these advantages, quiet noise and slight vibration may be contribute to low Transmission Error (TE), which can be calculated by Tooth Contact Analysis (TCA). However, to obtain numerical solution of the meshing equations based on TCA for planetary gear trains is very difficult because of a large number of nonlinear equations and unknowns. A simplified method utilizing planet phase angle is investigated and the numerical solution of planetary gear trains TE by TCA can be realized in this paper.

Abstract: A multiscale method coupled molecular dynamics simulation and finite element method is used to investigate two dimensional nanoscale sliding contacts between a rigid cylindrical tip and an elastic face centered cubic copper substrate with textured surface, in which adhesive effects are considered. Two series of nanoscale surface textures with different asperity shape, different asperity heights and different spacing between asperities are designed. Through the friction forces comparisons between smooth surface and textured surfaces, a better shape is advised to indicate that asperity shape plays an important role in friction force reduction. With proper asperity height and proper spacing between asperities, surface textures can reduce friction forces effectively.

Abstract: Planetary gear train (PGT) with herringbone gears is one of typical transmission styles used in marine power transmission. How to effectively design a PGT with lighter structures and lower vibration and noise is a fatal task for heavily loaded marine gearing. An analysis system which was developed in the past decades is introduced in this paper to simulate the performance of planetary herringbone gear trains. The effects of main crucial parameters on the static and dynamic characteristics of planetary herringbone gear trains are studied by using the analysis system. The results are discussed and show that the presented system is effective and can be used in design of planetary herringbone gear trains.