Applied Mechanics and Materials Vols. 799-800

Abstract: In conventional charge structure, the shell of charge’s containment is normally closed, with no explosive. When initiating charge, shell expanding to the outward, rupturing and eventually spreading out which was driven by the charge, this don’ have a guiding role to the detonation product flow. To further enhance the control of charge’s detonation product and energy flow, realizing the effective use of detonation products. The thesis put forward a structure design of filling thin-layer explosive in multi-layer shell, by initiating thin-layer explosive to control the deformation of shell, obtaining a approximately function with Laval Nozzle structure which can control the gas product when charge detonation. The thesis put forward a structure that including multi-layer explosive shell, establishing a numerical simulation model. Analysis the difference of shell’ deformation on different initiation method, provides a design references for further engineering application.

Abstract: During the application of approximated methods of estimations for calculating a stress-strain state of the shell an explicit question of accuracy and resource-intensiveness of the method is raised. From that point of view, the method of subsequent parameters perturbation (MSPP), developed by Vladlen V. Petrov in 1975, can be called the most effective one. The result of the application of this method is that the solution of a nonlinear model can be reduced to the sequence of solutions of systems of linear equations. The application of the method of Bubnov-Galerkin for solving linear equations is conjugated with the necessity of building the basis system of functions for every concerned problem. The method of building the basis system of functions for the shell with the boundaries of arbitrary configuration is offered in this paper..

Abstract: In the paper nonlinear vibrations of a drill string’s section in a supersonic gas flow are studied. The drill string is modelled in the form of a circular cylindrical shell under the effect of a longitudinal compressing load and torque. In contrast to the previous research, pressure of an unperturbed gas is defined nonlinearly in the third approximation. The eighth order partial differential equation describing the motion of the shell reduces to a nonlinear system of ordinary differential equations with application of the Bubnov-Galerkin technique. An implicit Runge-Kutta method is applied to construct modes of vibrations.

Abstract: This paper compares the transient thermal performance between counter and parallel cross flow heat exchangers subjected to time varying inlet mass flow rates and inlet temperatures that hasn’t been previously discussed in the available literature. Specifically the transient performance of 2 pass and 3 pass cross flow heat exchangers is discussed in this paper. In the present study the energy balance equations for the hot and cold fluids and the heat exchanger wall were solved using an implicit central finite difference method. Representative values of NTU were considered, and the NTU’s of the heat exchanger were assumed to be uniformly distributed among the heat exchanger passes. Other physically significant parameters such as the capacity rate ratio and the convection heat transfer resistance ratio were systematically varied. A detailed summary based on the observations has been presented.

Abstract: A numerical analysis of an oil-lubricated spiral grooved upstream pumping face seal, accounting for the occurrence of cavitation, have been performed in this paper. The “equivalent flow model”, which is a theoretical scheme for taking the JFO boundary condition into hydrodynamic lubrication theory, was applied to the analyses by a finite difference treatment of the Reynolds equation that dealt with the geometry of logarithmic spiral groove. The calculated results were compared respectively based on Reynolds model and JFO model. The load capacity, cavitation ratio, frictional torque and leakage rate were also theoretically calculated. The difference between the theoretical results based on two boundary conditions for cavitation occurrence is considerable. The JFO boundary condition should be used in theoretical studies on sealing characteristics rather than Reynolds equation, especially in the conditions of less groove depth and high rotary speed.

Abstract: A short split Hopkinson bar system with a total bar length of 3 m (a 2 m input bar plus a 1 m output bar), a striker length of 254 mm, and a diameter of 25.4 mm, is designed. Through numerical experiments, the stress vs. strain curve and the rate vs. strain curve of the specimen are obtained from the bar signals. These measured curves are reasonably consistent with the input stress-strain curve of the specimen for the numerical experiment and the prediction by the recently reported rate equation, respectively, verifying the reliability of the designed SHPB system.

Abstract: In industry, the special kind of trajectory is often designed to fit the desired motion required. In literature, four-bar mechanism is popularly applied and well studied in the trajectory generation. Different types of trajectories are generated by the choose of the ratio of links. The five-bar mechanism is another popular one to generate the desired trajectory and it is more flexible due to it has two degrees of freedom. The geared five-bar mechanism is then commonly used by reducing the degree of freedom of the mechanism into one by implied one pair of gear. In this study, the trajectories generated by a novel cam driven five-bar mechanism proposed by the authors are investigated. It could supply more choices in the application of trajectory generation.

Abstract: The continuation inverse problem for a solution to an elliptic equation in cylindrical layer for a model of stationary diffusion process is considered. Cauchy data are given on the outer boundary of the cylindrical layer; need to recover a field at the inner boundary of the cylinder. The problem is reduced to three different Cauchy problems for a second order ordinary differential equation. On the base of necessary minimization conditions of the residual functional analytical formulas for a regularized quasisolution to the inverse problem are derived.

Abstract: An unsteady, two-dimensional numerical study was conducted to investigate the aerodynamic and flow characteristics of a bio-inspired corrugated airfoil oscillating at 2Hz with an amplitude of 10°. The upstream flow was set such that the chord Re = 14,000. The computational results were validated against experimental results from a 2D particle image velocimetry (PIV) experiment on the same airfoil geometry. Complex flow structures such as the formation and shedding of trailing edge vortices have been revealed to have significant impacts on the lift and drag characteristics of the airfoil in oscillating motion. The shed vortices provide a low pressure region on the top surface of the airfoil throughout the period of oscillation, thus increasing lift of the airfoil. In particular, vortices formed and shed from the rear-most corrugation appear to have the largest effect. The pitch-down motion produces a lower absolute peak lift as compared the pitch-up motion which may be explained by the disruption of the high pressure zone on the top surface of the airfoil by a vortex forming in the corrugations. This results in a relatively lower high pressure region on the advancing side as compared to the pitch-up motion. In addition to the lift calculations, drag calculations indicate that net thrust is being produced during the oscillations and more thrust is produced on the pitch-up than the pitch-down motion.

Abstract: We examine the method to determinate the kinematic characteristics of the RSM, Classification of mechanisms of this class to convert rotational motion into linear motion is introduced. At the same time, we have developed some formulas to determinate the kinematic transfer functions of the RSM of different types depending on the geometrical parameters of this kind of screw mechanism.