The action point of the Coulomb active earth pressure used to be determined at the one-third place of the wall height, and the analysis in this paper shows that this practice is not reasonable. In order to solve this problem, considering the forces on the sliding soil wedge behind the wall, based on the balance of three converging forces, the relations between the earth pressure distribution of the wall back and the distribution of the soil wedge pressure on a stable soil behind, and the geometric relationship, the expression of the position of the action point of the active earth pressure is obtained; the sensitivity of the height of the action point to the impact factors is analyzed, which shows that the sensitivity sequence from big to small is the inclination of the wall back, the angle of the internal friction, the angle of the external friction, and the angle of the fill slope.
The ear is the important organ for hearing with a typical structure for transmiting vibrations from the sound exicitation and change them into the impulses of the acoustic fibers. The establishment of a complete and effective biomechanical model of the human ear and the study of its biodynamics behavior may help us understand and analyze the sound transmission mechanism. The study of the change in the sound transmission mechanism at a pathological state and after a surgery may provide a theoretical basis for studying the mechanical mechanism of relevant clinical diseases. The present paper reviews the progress of biomechanical models of the human ear as a hearing system and their clinical applications and prospects in the future.
The crane is a key equipment for an ocean drilling platform. To ensure the safe operation of the entire system, it is necessary to study the structural mechanical property of the truss boom in the hoisting plane. With consideration of such uncertain factors as the structural features of the truss boom and the component performance degradation, a three-dimensional numerical model of the boom is built using the finite element method, in which, the stresses of the main load-bearing member bars are taken as the key indicators and the relevant design parameters as the input updating objects. Numerical simulations and experiments on the whole hoisting process are carried out. It is indicated that the method can simulate the hoisting process and the structural mechanical property, the failure shape and the dangerous position can be obtained. This method provides some insight for the lifting task and the security operation of the jib structure, and is suitable for engineering applications.
The concept of stiffness ratio is defined to study the strengthening of a fuselage with large opening, in order to meet the design requirements of stiffness and deformation. The relationships among the opening angle, the fuselage radius, the skin thickness, the beam area and the stiffness ratio are formulated through a theoretical analysis. The principle and the method to strengthen the fuselage with large opening are successfully applied on the aircraft in the preliminary design stage and can be used to guide the structure design.
The reverse K-joints are widely used on offshore platforms, therefore, their strength is a very important issue for the safety evaluation of the platforms. Using ANSYS software, an FEM model of the reverse K-joint with welding seams is built. It is divided into several zones and each zone is meshed separately. The distribution of the hot-spot stress around the welding seams of the joints subjected to axial loads, in-plane bending (IPB) moments and out-of-plane bending (OPB) moments is analyzed. Based on the results of 105 reverse K-joints models, the stress concentration factor (SCF) around the wedling seams under these three basic loads is obtained. By analyzing the chord and the brace separately, the effects of geometrical parameters on the SCF and the hot-spot locations are studied.
In order to study the acoustic emission and the fractal characteristics of coal samples under triaxial compression, experiments were carried out by using the RMT-150C rock mechanics test system and the CDAE-1 acoustic emission instrument under different confining pressure(5MPa, 10MPa, 15MPa), and the acoustic emission count, the cumulative count and the acoustic emission sequence fractal characteristics of coal sample were obtained. It is shown that the coal has different acoustic emission characteristics under different confining pressures, the higher the confining pressure is, the more precursor information will be obtained. The coal samples show the fractal characteristics under different confining pressures, and the fractal characteristics will strength with the increase of the confining pressure. The acoustic emission sequence fractal dimension value will experience a process of volatility-rise-drop during the process of coal sample failure, which can be regarded as the precursor information to predict the collapse of the coal rock masses.
The kinematics and dynamics of the underwater bubble is always one of important research issues. The high-speed imaging and the load test technologies provide excellent tools for studying the bubble's behavior. The development and the applications of the high-speed imaging and the load test technologies for bubble dynamics are reviewed in this paper. Firstly, the origin and the classification of bubbles are briefly summarized; secondly, the high-speed imaging on capturing the bubble's deformation is reviewed and analyzed; thirdly, the bubble load test equipment and technologies are discussed; lastly, the problems needed to be studied further are suggested.
A completely new meshless method for the numerical simulation of the shock-induced combustion is developed in this paper. The two-dimensional Euler equations are employed. The spatial derivatives are approximated by using a local least-squares curve fitting based on clouds. The inviscid flux is calculated by a multi-component HLLC scheme. The four-stage Runge-Kutta algorithm is used to advance the integration in time. The chemical kinetics is modeled using a finite rate reaction model. The flow fields of the shock-induced combustion in different mixtures are simulated for validation. The results agree well with the numerical results of mesh-based methods, which indicates that the method is reliable in the numerical simulation of flow fields of shock-induced combustion.
A lattice Boltzmann method with the use of an interaction potential between neighboring lattice particles is applied to simulate the fluid flow in a 2-D wall-patterned pipe. The simulation results indicate that the surface wettability, the surface roughness, the pressure and the fluid viscosity are the factors dominating the liquid-solid slip. The friction is reduced in the wall-patterned pipe under a low pressure. The simulation results can explain the existence of a threshold pressure gradient in mining underground reservoirs as well.
A reliability analysis model is established to analyze the stability of a tank based on the tank-roof stability checking formulae and the reliability theory. A new method for calculating and analyzing the reliability and the stability of the tank-roof by the minimum distance and finite difference methods is proposed. The analysis results of the tank as an engineering example by the proposed methods show that the self-supporting role of the roof-plates and the strengthened role of stiffened ribs would affect the reliability index of the tank-roof under different external loads. The curve fitting method is applied for expressing the numerical relationships between the reliability index and affecting factors. A reliability assessment is also performed to show the feasibility of analyzing the stability reliability of the dome roof for storage tanks in service.
The rotor system(H858 compressor) is studied. The natural frequencies are obtained for the bending vibrations using the software "MSC.Patran & Nastran". The frequency reliability mode is defined and the equations for the frequency reliability sensitivity are mathematically expressed by using the random perturbation technique, the reliability theory and the sensitivity approach. The frequency reliability sensitivity of the rotor system is obtained by the above mentioned theory, and it is shown that the proposed method is accurate by comparing the results with the finite element results obtained by software "Nessus".
For a twin-cell box girder, from the difference of the shear lag warping between different cantilever plates, and combined with the axial force equilibrium condition of the whole section, a new shear-lag warping displacement function is defined for each cantilever plate of the box girder. The governing differential equations of equilibrium for the shear lag for the twin-cell box girder are established on the basis of the variational principle. For a typical simply supported beam with a twin-cell box girder, using three dimensional numerical methods of the plate-shell element and the analytical solution method proposed in this paper, respectively, the shear lag distributions under the uniform load and the concentrated force are obtained. It is shown that the new displacement pattern of the shear lag warping can reflect the difference of the shear lag warping between different cantilever plates and the new analytical solutions are in good agreement with the finite Element results. The shear lag effect on the top and bottom plates near the middle webs is different from that near the side webs on the twin-cell box girders. For an example girder, the stresses near the middle webs are larger than those near the side webs.