Applied Mechanics and Materials Vol. 404

Abstract: A lightweight valve is often made of TiAl alloys and its stem can be solid or hollow. Such valves can mate with guides made of cast iron or of phosphor bronze at different conditions in their contact zone valve/quide. The aim of the research was to measure the friction force in the sliding contact between the valve stem made of TiAl alloy and its guide made of phosphor bronze, in the absence of oil. The experiment was conducted at room temperature and in static air under normal pressure. The investigations were conducted with use of the tester, which is presented in this article. The loading of contact zone has varied periodically during series. The displacement and acceleration of valve and the force during its impact into seat insert have been measured during tests. Additionally the sound level has been measured, either. Tests have been provided for different frequency of driving force. Additionally, researches on the tribotester pin-on-disc, presented in the article, have been provided, with the pin made of Ti6Al4V alloy and the disc made of phosphor bronze. The model of research stand has been elaborated for the simulation of dynamics for the material sample rotating plate assembly. The aim of such researches has been to obtain values of coefficient of friction for such tribological pair and to simulate dynamics of the material sample rotating plate assembly, characteristic for used research stand. The obtained courses of coefficient of friction vs. loading, slide velocity, duration of motion of material sample in respect to the rotating plate have been presented in the article. On the base of simulation results the values of damping coefficient have been estimated, which allow to obtain the value for the amplitude of the modeled motion for the material sample in respect to the rotating plate near to the value of the amplitude for the real motion. Such estimation allows forecasting the dynamics of the mentioned assembly for other values of velocity and loading.

Abstract: The principle of fatigue life computation was presented on the basis of local stress-strain method. It was set up that the finite element model of stepped shaft with different radii of round corner and radius ratios. The local stress and strain were computed at shaft shoulder fillet under torsion load. The fatigue crack initiation life was determined by means of local stress-strain method under symmetric cyclic torsion load. The result showed that the fatigue life increased with the values of fillet increase and decreased with the values of radius ratio increase, and the smaller of the transition radius was, the shorter of the life would be.

Abstract: In order to study the performance of steel beam in the cooling process, a series of numerical analysis has been carried out in this paper. The solid model of the beam was established firstly using finite element method, the beam was heated and cooled gradually under the certain uniform load, then the internal forces and deformation of the beam were analyzed in the whole fire process. Based on this, the parameters of the highest temperature, heating rate and the cooling rate were changed, and their affect on the beam performance was studied by comparing.

Abstract: As an important mechanism with special and extensive application, the three degrees of freedom spherical parallel mechanism is always a research hot in the mechanical fields. In this paper, the feature of the 3-RRR spherical parallel mechanism with coaxial input shafts is introduced, and its motion feature is analyzed based on the screw theory. The mobility of the spherical parallel mechanism is calculated by using the Modified Kutzbach-Grübler criterion, and the inverse displacement problem of the mechanism is solved. Then the expression of the Jacobian matrix is deduced based on the kinematics equation and its inverse solution. The contents of this paper should be useful for the further application of the spherical parallel mechanism.

Abstract: By establishing bus simplify coordinate system model and equivalent mechanical model, inertial forces and external forces are analyzed through vehicle lateral movement and vehicle's yaw motion and roll motion. Three degrees of freedom linear motion equation of vehicle is established taking into account lateral motion, yawing movement and rolling motion of vehicle and it can be solved by using method of state space equation. Vehicle dynamic characteristics are analyzed by using this method and programming with Matlab. Vehicle in steering wheel angle step response is analyzed under the conditions of different tire wheel cornering stiffness, moment of inertia, height of center of mass. The results show that increasing rear wheel cornering stiffness, reducing front wheel cornering stiffness and center of mass height, which can effectively improve stability of vehicle. Simulation results provide a theoretical basis and reference for the selection and design of vehicle.

Abstract: Existed consider roll of heavy vehicle's dynamics model have defects and deficiencies. Vehicles lateral-load transfer that will lead to vehicles rollover is not considered; the whole vehicles dynamics model neglect unspring masss roll angle while the unspring masss independent force analysis considered the roll angel, the establishment of the model is not consistent in; the model dont have a united positive direction rule for all the variables. Because of all of these defects the model cant rightly reflect vehicles motion status. This paper takes lateral-load transfer as a dynamic variable; unspring masss roll angle is considered when establishing the whole vehicles dynamics model; all variables positive direction is united. Reasonable, right, applied to evaluate vehicle's rollover stability and quite newly model is established.

Abstract: The crack of kiln shells was seen regularly due to axis deflection and asymmetric load distribution. It will be helpful to improve kiln performance if the remaining life of kiln shells can be kept the same. For this the formulae of stress spectrum and fatigue life of kiln shells are obtained. Taking the aligned values of axis deflections as design variables, equal fatigue life of shells and maximum axis deflection as the objective function, considering the fuzzy factors during axis alignment, the fuzzy optimization model of kiln axis alignment is set up. The results indicate that kiln axis can be aligned as direct as possible, and life expectancy of kiln shells can be optimized to keep near the same. Accordingly, the valuable production time of kiln can be increased greatly by such aligned method.

Abstract: Balance valve is the key component of crane lifting system, its performance determines the hoisting performance. Through in-depth study on the dynamic characteristics of the balance valve, find out the influence of parameters of the stability of the system, and carried on the simulation analysis using AMESim software, and to find the simulation process, put forward the optimization measures.

Abstract: Preconditioning techniques have become established as a useful technique for optimizing accuracy and efficiency of CFD solutions over a range of flow conditions. Specifically, at low Mach numbers, it is well known that the standard physical time derivatives lead to an ill-conditioned system due to the stiffness between the acoustic and particle wave speeds, which in turn results in degraded convergence and inaccurate discretization. With preconditioning, the pseudo-time derivatives scale the acoustic speeds so that they remain well conditioned at all Mach numbers. A low-diffusion preconditioning Roe scheme by using an adjustable parameter in preconditioning Roe scheme to control the numerical dissipation and the adjustable parameter value rules are proposed. Numerical results show the efficiency of the new scheme and the low Mach/Reynolds number steady and unsteady solutions of viscous flow past a circular cylinder are satisfied.

Abstract: Unreasonable road geometric alignment has a negative influence on vehicle handling stability, especially when vehicle drives with a high speed. For horizontal road alignment, radius and banking of circular curve are the most popular and important parameters. To investigate the influence of horizontal road alignment on vehicle handling stability, a 3 degrees-of-freedom vehicle dynamic model is established. Three road horizontal curves with different radius are established in Carsim environment to investigate the influence of curve radius on vehicle handling stability and four different banking curve roads are built to study the impact of road banking on vehicle roll stability. The research achievement will provide theoretical basis and technical support for road geometric alignment design.