Applied Mechanics and Materials Vols. 34-35

Abstract: In order to indicate the aging process and evaluate the aging resistance of warm mix asphalt, thin film oven tests of original asphalts and warm mix asphalts were conducted, and the softening points of different asphalts in aging process were compared. Then, using softening point as a parameter, the aging kinetics model was established and the kinetics parameters were also calculated to reflect the aging performance of different asphalts. It is indicated that warm mix asphalt has larger activation energies and lower reaction rate constant than those of original asphalt, and the aging performance of warm mix asphalt after are better. The aging behavior of warm mix asphalt could be well evaluated by the aging kinetics model.

Abstract: The gearing transmission equation was deduced by the principle of the engagement characteristics between plastic helical gear and steel worm. This paper makes an analysis on the law which is the deformation process of tooth profile and potential contact in different kinds of load by means of Hertz contact theory. The paper also uses MSC.Nastran to simulate the stress-strain status, the deformation process and arrives at the law of gearing changing, which was verified the correctness of the analysis above.

Abstract: In order to assure the security of Wuhan–Guangzhou railway passenger dedicated line, the experiment study of dynamic response was developed in the construction finished roadbed. The longitudinal wave velocity and the transversal wave velocity of stress wave in the roadbed were obtained. The weaken rule of stress wave in roadbed was analyzed during its dissemination and the dominant frequency was gained in the vibration structure. The dynamic modulus of elasticity and the poisson's ratio of roadbed material were defined. Furthermore, the experiment simulated the process of train instant load during transmitting in the roadbed. The influence of roadbed material, structural property to locomotive safe, steady movement was researched. These conclusions provide uses for reference importantly to guarantee the quality of slab track on railway passenger special line under construction.

Abstract: To replace full penetration weld with twin fillet weld for the design and construction of joint of beam to CFST (concrete-filled steel tube) column with interior strengthening ring, six specimens were tested by incremental loading and cyclic loading. The finite element package ANSYS was used to study the nonlinear behavior of such specimens. The finite element model was validated by comparing the computed values with experimental results. The failure mode was local buckling in the flange edge between beam flange and steel tube because of local stress concentration. When the joint was damaged, the stress of weld (including full penetration, partial penetration, and twin fillet weld) between steel tube and interior strengthening ring is smaller than yield strength. The twin fillet weld was proposed for design and construction of the joint instead of full penetration weld.

Abstract: Mathematical models of saw angle adjustment system were presented. The errors of each constraint function were calculated using the software MATLAB. Considering error, computational complexity and production efficiency of the machine, a linear function was selected. According to experiments, 0° and 35° angles of saw were selected as the trial cut angle. The results show that its error is smaller than least square fitting and it can assure machining accuracy when there are assembling errors.

Abstract: In order to improve characteristics of booster valve, one kind of pneumatic boost valve was proposed, which makes use of the expansion power, firstly, aiming to the process of pneumatic boosting valves, non-linear differential equations of pneumatic booster valves were set up, using the software MATLAB/simulink for modeling simulation, and variations of flow and pressure of air in boosting chambers and driving chambers were obtained. Secondly, According to the principle of simulation, input pressure-reduced pneumatic booster valve was studied experimentally; curves of exhaust flow and pressure of air in tank were got. As a conclusion, it is clear that simulation and experimental results have a good consistency; flow of air exported by expansion energy-used pneumatic booster valve is larger than that by input pressure-reduced pneumatic booster valve, and the maximum flow is 2.5 times of the flow of air exported by input pressure-reduced booster valve. Because of its compact structure, small size, no external power supply etc., pneumatic booster valve was widely used in locally pressure-boosting occasions of pneumatic system [1-2]. Most of the booster valves were called input pressure-reduced pneumatic booster valve (short for input pressure-reduced booster valve), output pressure of which was set by adjusting input pressure of the driving-champ, such as VBA series of booster valve of SMC Corporation [3]. With the development of energy-saving technologies of pneumatic system, importance of booster valve has become more and more obvious [4]. However this type of booster valve has its own shortages, for example its life is too short and output flow is too small, when boosting-rate is higher, these shortages become more distinct [5-7]. In this paper, firstly, one new type of booster valve (called expansion energy-used pneumatic booster valve, short for quantitative booster valve) was proposed. On the basis of analysis of working principle and structure of both booster valves, mathematic models of the quantitative booster valves were set up, using the software MATLAB/simulink for modeling simulation to research the working processes. Last, According to the principle of simulation, input pressure-reduced booster valve was studied experimentally.

Abstract: No quantitative data were reported in the literature regarding the effects of the ACL reconstruction tunnel(s) on patellofemoral contact .In this study the patellofemoral joint was built from MRI data of a normal knee. Based on this, the patellofemoral contact models in which there were ACL reconstruction tunnel(s) were also built. Then different contact statues of patellofemoral joint were simulated by orthogonal test and finite element method to analyze the effects of the ACL reconstruction tunnel(s) on patellofemoral contact. Results show that: 1. Stress on the cartilages is not sensitive to the parameters of position and orientation relatively, but the single-bundle and double-bundle reconstruction tunnel(s) significantly change the extent of the sensitivity to the motion parameters, especially the stress on the femoral cartilage. 2. The stress on the surface of cartilages also will be obviously changed by single-bundle/double-bundle tunnel(s) and they will significantly increase under some contact status, but for the contact pressure, it is inconspicuous. 3. For single-bundle tunnel, contact areas between cartilages change little while only about one-fifth of the total contact locations have changed by 20%. Besides, the effects of double-bundle are smaller than single-bundle tunnel. This study not only provides technical data to improve the reconstruction quality, but also supplys a method for the assessment of ACL reconstruction.

Abstract: Adaptive multiple impedance control based on passivity is studied about two robot manipulators cooperating an object which interacts with external environment actively. The dynamic model is derived by Newton-Euler equation and the relations between the forces are analyzed. The relations between stiffness coefficient and convergence are explained by solving the differential equation when the stiffness coefficient is known. The adaptive impedance controller based on passivity is designed combining adaptive control and generalized impedance control when the stiffness coefficient is unknown. The impedance control based on internal force is adopted for the cooperative system. The simulation results prove the validity of the method.

Abstract: Three basic sub-problems of screw theory are acceptable for some particular configuration manipulators’ inverse kinematics, which can not solve the inverse kinematics of all configuration manipulators. A new sub-problem is presented and the inverse kinematics thereof is solved in this paper. Based on the extended sub-problem, a manipulator, the inverse kinematics of which can not be solved by the three sub-problems without the participation of the new sub-problem, is constructed. The inverse kinematics of the manipulator is solved with the help of the extended sub-problem。Therefore a close solution is gained. The sub-problem herein can be applied directly in the inverse kinematics of a manipulator, providing a new approach for the inverse kinematics of a general configuration manipulator.

Abstract: Considering the nonlinear characteristic of suspension stiffness and the effect of road input, a dynamic model of tread’s lateral vibration is established based on lateral-vertical force coupling, and the complex dynamic behavior of the system is analyzed. The results show that: the lateral self-excited vibration of tread is a kind of complex quasi-periodic motion caused by Hopf bifurcation of system, which oscillating range increases at first, then decreases with vehicle speed; the quasi-periodic motion occurs only at specific speed range, while not happen when speed is too low or high.