Advanced Materials Research Vols. 479-481

Abstract: Computational fluid dynamics (CFD) technique is used to calculate and analyze the hydrodynamic characteristics of underwater gliding UUV. Governing equations and turbulence model applied to the hydrodynamic calculation are proposed. Calculation results show that the underwater gliding UUV has a good hydrodynamic characteristics which are relatively close to engineering estimation results. Research in this paper lays the foundation for further in-depth study.

Abstract: The measurement of residue prestress force is one main issue for condition and performance assessment of prestressed concrete beam bridge. This paper proposes a vibration based parameter estimation technique for this purpose. Under given form external excitation, beam velocity responses at multiple points are collected firstly. The prestress force of the beam is then identified based on the minimization of the least square difference between the measured response and the baseline response. A numerical study on a beam of variant length, subjected to a constant prestress force with variant eccentricity, is conducted to show the effect of prestress force and the effect of bending moment due to eccentricity on fundamental frequency of the beam. The results show that this vibration based method for prestress force identification is both theoretically feasible and practically workable.

Abstract: With effects of drilling pressure, self-excited force, random impacts and contacts of cone bit and rock, the motion and stress distribution of cone bits -drill string is extraordinary complex during oil drilling. Considering the geometry structure and the comprehensive boundary conditions of the full hole drilling-string system, a coupled nonlinear dynamic model of bit-rock-drill-string-well system is set up using Hamilton approach. Then the dynamic simulation is performed and the dynamic characteristics of drill string system are discussed. Computational results reveal numerous interesting characteristics which can be used to forecast the formation of hole trajectory.

Abstract: When discussing the rubbing issue of rotor system, the effect of nonlinear rubbing force is needed to be considered. In this paper, modeling and numerical simulation were carried out by using the nonlinear rubbing force based on Hertz contact theory, and researching the dynamic response of fault rotor system in the conditions of the different rubbing stiffness. Through the analysis we found that, in the case of larger rubbing stiffness the result simulated by using rubbing force model based on Hertz contact theory has stronger nonlinear and more obvious rubbing feature, compared to the rubbing model of linear stiffness. It is beneficial to determine the occurrence of rubbing. Refer to the relevant experimental results, the correctness of the Hertz rubbing model and the feasibility of applying it in the modeling of rubbing rotor system were confirmed.

Abstract: Description of the dynamic characters of the main parts of pistol is necessary. On the basis of analyzing the motions and forces of every part of some Gatling gun, a 63-degree-of-freedom virtual prototype composed by 101 rigid bodies is established by means of Solid Works and ADAMS. The validation is made and the credibility of the virtual prototype is approved by compared to the simulation result and the experimental data of the barrel Angular displacement, velocity and displacement of bolt frame. The dynamic simulation analysis of automata is produced. Moreover, the influence of some structure parameters on the dynamic characters of the main parts is studied by simulation, which has laid the foundation for further simulation and structural optimization

Abstract: A torsional time-varying vibration model of a beveloid gear pair with backlash nonlinearity is formulated. It incorpprates the load-dependant time-varying mesh characteristic vectors and backlash non-linearity. Using the proposed model, the influence of mesh damping and non-linear backlash on beveloid gear dynamics is investigated. Computational results reveal numerous interesting nonlinear characteristics, such as jump discontinuities and chaotic behaviors.

Abstract: Aiming at the oversteer trend of a light-bus prototype in the steady state circular test with full load, a virtual prototype of the vehicle was constructed by using MSC.ADAMS/CAR. The modeling methods for the components such as leaf-spring, absorber and rubber sleeve, whose dynamic characteristics appear nonlinear, are discussed. The simulation results show the vehicle exhibits the oversteer behaviour which is consistent with the subjective sensation. To solve the problem, the chassis parameters affecting steady state handling are discussed. A version regulating the roll rate distribution of front and rear suspension was put forward. After some discussion, the sensitivity analysis of the front and rear stabilizer bar stiffness, leaf spring span, front and rear eyehook location of rear suspension are performed to improve steady state handling. Sensitivity analysis results show that decreasing the leaf spring span, increasing the diameter of front stabilizer bar, decreasing the diameter of rear stabilizer bar and moving front and rear eyehook location of rear suspension can solve oversteer problem. It is expected that the above conclusions can provide good technical solutions for engineering improvement.

Abstract: Traditional silk looms are connected with traditional textile technology, which also represent the development degree of technology and society. This thesis discuss some kinds typical traditional silk looms of Shanxi province, in north of China, and draw a conclusion that standing loom originated in Song dynasty still existed in a few villages until modern China, but other two typical silk looms originated from the Ming dynasty and were used and widespread until 1980s in north of China. This thesis focuses on the key parts and functions of silk looms, explains the operation mechanism, and also compares the similar looms in different regions.

Abstract: Based on the basic principle of load disturbance method to implement equilibrium path transformation, this paper puts forward a new load method to deal with structural bifurcation point instability based on FEM. The unloading step obliterates the disturbance entirely, and the load method can get exact bifurcation point. The simple example demonstrates that the load method is practical and effective.

Abstract: The simulation of shaper kinematics and dynamics rules is conducted with MATLAB. The rules of ram displacement, speed, acceleration and links forces rules are obtained and shown in figures. The research results can be used for the design optimization of shaper contractures. Redundant programming is not necessary any more, since MATLAB is applied into the simulation. The study method is of instructive significance for the kinematics and dynamics analyses of similar mechanism.