Applied Mechanics and Materials Vols. 300-301

Abstract: A tube furnace is a heat treatment device in which a specimen is heated in the presence of an inert gas using electric heating coils embedded in a thermally insulating matrix. Heat flux and temperature gradients of sample during heat treatment in a tube furnace depend on the gas and wire velocities. These parameters were used in this paper for a 2-D axisymmetric numerical study to determine an optimized relationship between the temperature and the sample wire motion. The results show that wire velocity considerably affected the wire temperature distribution and increased the gas temperature to some extent. The phenomenon resulted in the shifting of the heating zone on the wire surface and occurrence of an inner convection heat transfer.

Abstract: Least-squares fitting was employed to interpolate the reflect point, ghost body-cell method (GBCM) was applied to quadtree-based adaptively refined Cartesian grid approach, and finite volume method was employed to solve Euler equations. Shape of cut cell kept in accordance with that in the flow field which efficiently relieved the time step restriction of small cut cells. Flows around a circular cylinder and the double NACA0012 airfoils are simulated and compared with published structured grid results, which show flow field around complex geometries is adequately resolved resort to GBCM approach on adaptively refined Cartesian grid in computational fluid dynamics (CFD).

Abstract: In this present paper, laminar cavity flow is analysed at Re = 5.12 x 10⁴ based on cavity length. The experiments were conducted in an open subsonic wind tunnel using Particle Image Velocimetry (PIV). A rectangular cavity with constant depth of 4 cm with length-to-depth ratio of 4 was used. Several types of blockage had been located at the leading edge of cavity and each experiment was performed by acquiring 700 image pairs to filter out the velocity vectors. The results are given in terms of mean velocity profile accordingly and compared thoroughly by dividing cavity into 4 sections. The result had been shown in mean velocity profile in u and v velocity component.

Abstract: A mathematic model of ball screw was constructed which was based on the elastic contact deformation theory. The helix angle was considered and the formula of axial elastic deformation was deduced in this study. Furthermore, a finite element model of ball screw was established and its elastic deformation results were also acquired. And the effect of contact angle on axial elastic deformation was analyzed by theoretic method and FEA. The study shows that the axial elastic deformation of ball screw changes with the contact angle. The deformation will decrease by the contact angle increasing, and the positional accuracy of the ball screw is improved.

Abstract: Mechanical behavior of solid propellant material under multi-axial loads has attracted much attention in engineering application. According to the properties of solid propellant material, a kind of triaxial compressive device for solid propellant material was designed by utilizing the operating principle of the soil triaxial compressive device. The structural features and operating principle were expounded, and some notes should be paid attention during tests, and mechanical properties of a kind of double-base propellant material under hydrostatic loading were investigated, and some very meaningful data and conclusions were obtained. The results show that the yield strength and compressive strength of double-base propellant material under hydrostatic loading have obtained more remarkable enhancement than those without the hydrostatic pressure effect. The experimental device and the test results may lay the foundation for further research into a viscoelastic-plastic constitutive model of solid propellant material.

Abstract: A constant temperature range of the heating system plays an important role in the thermosonic bonding process. Heating block will provide enough heat for the heating system. In the paper, the thermal model of heating block and heating system were calculated by finite element method, and then some important conclusions were obtained. The change of temperature and thermal stress of block with the reference value of x and y was obtained. And an optimal structure of block for right temperature was built. The temperature distribution, thermal displacement and thermal stress distribution of the heating block and heating system were disclosed. The relevant change trends of temperature and thermal stress under the different load of temperature were investigated. These results can help improve the reliability of the heating system used in the thermosonic bonding process.

Abstract: Rail failure and track composite irregularity is the source of violent harassment of the wheel-rail system. Track irregularity has significant impact on the driving security and stability of the train. At present, the focus of the Chinese railway development is high speed, heavy haul and shortcut transportation, thus the influences of rail failure and track composite irregularity will be more remarkable, which has become a primary factor that limits the running speed. This paper analyzes the characters of rail failure and formation mechanism of the track irregularity, forecasts the trend of track irregularity development and explores the hidden risks that might occur and influence the safety of railway traffic.

Abstract: By the theory of complex functions, symmetrical dynamic propagation problems of mode Ⅲ interface crack were investigated. The problems considered can be very easily translated into Riemann-Hilbert problem by the methods of self-similar functions, and the universal expressions of analytical solutions for the surfaces of symmetrical mode Ⅲ interface crack subjected to moving alterable loadings Pt3/x3 and Px4/t3 were obtained, respectively. After those solutions were utilized by superposition theorem, the solutions of arbitrary complex problems could be acquired.

Abstract: The SEA model of hypersonic aircraft is established based on statistical energy analysis (SEA) theory. Three parameters of the SEA model are established by the theory and experiential formula. According to damping loss factors of model subsystem and acoustic absorptivity of cavity, sensitivity analysis of vibro-acoustic response is discussed. The effect that division way of plate subsystem and material structure cause to vibro-acoustic response is analyzed. The analysis results show that the material structure, damping loss factors and material type have the great effect on the characteristics of vibro-acoustic response. The division way of plate subsystem can affect computational accuracy greatly. The influencing factors should be synthetically considered in the design of acoustics structure.

Abstract: Based on finite proximate method (FPM) with 5 points scheme, two-dimensional shallow water equations are discretized. The mathematical model of 2-D flows is developed for modeling flood propagation in complicated river channel and flood detention area, and the hydrodynamic boundary is resolved through the introduction of the fictitious water depth concept. According to predicting the instantaneous and partial dam-break in a frictionless, horizontal channel, the comparison proved that this method can reflect the dynamic process of flow and can well capture the discontinuity of the shallow water wave equations. The flood propagation in complicated river channel and flood detention area is stimulated numerically to reveal the complicated flow characteristics of flood waves. It is seen that FPM is one of the effective methods to solve problem of flood propagation, having good shock capturing capability.