Applied Mechanics and Materials Vol. 577

Abstract: To find out the influence factors to the force situation of the coring pipe in the drilling process, the discrete element method is employed to build the lunar regolith model and simulate the interaction between soil and the drill. A viscoelastic contact model is introduced to represent the impact between particles. To make sure the validity of the model, a biaxial-test is conducted to optimize the micro-parameters of the model. The drilling process is simplified to an inserted process and the model after calibration is in use. From the computational simulation results, conclusions can be made: to reduce the drilling speed or to drill aslant may be good to decrease the force loaded on the inside wall. Enlargement of the diameter and thickness can improve the sampling efficiency and prevent the soil sample from being destroyed, and drilling aslant may be harmful to the sample.

Abstract: Laterally interconnected air suspension can further improve air suspension performance. This paper presents the mathematical model of full vehicle and the test bench for laterally interconnected air suspension is established. Simulation and experimental results indicate that acceleration of sprung mass is reduced by laterally interconnecting the left and right air springs, and the larger pneumatic pipe diameter is, the better damping performance of the suspension will be. Compared with the conventional air suspension, laterally interconnected air suspension brings better ride comfort and driving stability for vehicles on uneven road.

Abstract: This paper presents a parameter matching method for the vehicle equipped with air suspension with adjustable auxiliary chamber, which is intended to improve riding comfort of vehicles. A bus model with eight degrees of freedom was established, which also includes air suspension with adjustable auxiliary chamber models and four road input models. The matching values of auxiliary chamber volume under different loads are obtained by analyzing the relationship with natural frequency of air suspension. The damping coefficients of front and rear shock absorbers are optimized by genetic algorithm under various driving conditions. The integrated performance of vehicle is improved to a certain extent after suspension parameters matching.

Abstract: A study about the structure load identification was made in this paper, based on the SEA power flow method. An inversion formula was firstly developed for the case that the load position is known. Using the formula, an algorithm was proposed to locate the source when the load position is unknown. A reference source must be chosen to utilize the algorithm. To make full use of the surplus data and to further improve the identification accuracy, the least square method was applied. Experiments about both cases were taken to validate the approach obtained above and it was shown that the approach is correct and effective. It is proved that the power flow inversion approach has some practical value in engineering.

Abstract: According to the design parameter of practical engineering, shell and tube sewage heat exchanger is chosen as heat exchanger of secondary sewage-source heat pump system. This paper commences from the design calculation of shell and tube sewage heat exchanger, followed by the analysis of dynamic characteristics influencing rule based on the chosen size. The influence of inlet temperature and outlet temperature on tube temperature and the influence of signal curve of different inlet temperature on outlet temperature are all included.

Abstract: Ultrathin gas film lubrication has been widely used in recent years, such as dry gas seal face gas lubrication, gas lubrication in the hard disk drive, etc. The rarefied gas effect must be considered when the gas film thickness is very thin. In order to analyze, compare, and select the appropriate rarefied effect model on gas lubrication, a comparative analysis has been carried out on the influence laws of the Poiseuille flow rate and the ratio of the effective viscosity coefficients and the dynamic viscosity, μ_eff/μ, with inverse Knudsen number, D ,or Knudsen number, K_n, as to different models. The results show that when inverse Knudsen number increases or Knudsen number decreases, the Poiseuille flow rate and the ratio of the effective viscosity coefficients and the dynamic viscosity,μ_eff/μ, of different models approach to each other. However, there are significant differences as to different models when the Knudsen number is large, and only several models from Hwang, Veijola, Peng etc agree with Fukui’s model.

Abstract: This paper studies the variation of speed and pressure to achieve accurate control of the die pressure for screw extruder based on high viscosity PVC production. SolidWorks was used to establish the model of screw extruder, and then imported SolidWorks models into the ANSYS to analysis the relationship of speed and die pressure at the speed of 2rpm to 7rpm.It laid the foundation of establishing extruder pressure control system.

Abstract: The wheel/rail profiles in different wear stages are measured using the apparatus of wheel-rail profile. The 3D elastic-plastic FEM contact models are established for the straight line and curves, in which attack angle is considered. Contact problems between the wheels in different wear stages and the worn rail are studied. Contact area, normal contact force, and equivalent Von Mises stress of different cases are analyzed. The obtained results show that the maximum equivalent Von Mises stress reduces and tends to be steady with the independent wheel wearing. Widening the track gauge can have an influence on the variation of wheel wear positions and the wear rules between wheel and rail. When the wheel with a certain attack angle contacts with rail, the maximum equivalent Von Mises stress appears at the contact region between the flange and rail side. The influence of attack angle on the wear between the wheel and rail is quite serious. It is very important to do the research for the further optimization and design of the wheel/rail profiles.

Abstract: In this paper, an efficient simulation program (FCG-System) is proposed to simulate 2D fatigue crack growth under mixed-mode loading conditions. The simulation is basically an incremental crack extension procedure. An object-oriented modeling frame is proposed for simulating fatigue crack growth of complex structures. The modeling frame is developed in the context of the commercial FE code ABAQUS, utilizing Python language and ABAQUS Scripting Interface (ASI). The highly automatic finite element simulation method is not only used for a single crack tip, but also has been extended to the system of interactive multiple cracks. The robustness and the accuracy of the new simulation code will be shown by two examples, including single crack growth and multiple cracks growth. Those applications indicate that the implementation of the FCG-System, as proposed herein, can be a useful tool for this class of fatigue crack growth.

Abstract: This paper conducts a comprehensive study on the optimization design for luffing mechanism of portal slewing crane. First, displacement formulae are derived of crampon hinge point of the luffing mechanism. Secondly, mathematical model is established for luffing mechanism optimization design of portal slewing crane, according to the mechanism characteristics, and, with an aim of making crampon hinge end point to move horizontally, and of satisfying the value of maximum and minimum amplitude, and of saving material, etc. Finally, program of optimization design is compiled for the luffing mechanism of portal slewing crane. The luffing mechanism of M4022 portal slewing crane is optimized, and the optimization result is satisfactory. This paper makes it possible to obtain not only each rod length and cross-section area, but also obtain the counterbalance weight and the each rod maximum force of the luffing mechanism.