Applied Mechanics and Materials Vols. 101-102

Abstract: In this paper, discrete wavelet transform (DWT) is used to analyze the acceleration signals near to the loose bolt, in order to study the characteristics of bolted joint condition. Firstly, an experimental system is built based on the NI data acquisition equipment. Secondly, based on qualitative analysis of the loose process of the bolted joints and spectrum analysis of response signals, an appropriate wavelet function is chosen and decomposed levels are determined. Lastly, according to the amplitude of each level, the contour diagrams are drawn and the Root Mean Square (RMS) of detailed coefficients at the sensitive level is calculated. Experimental result shows that both DWT contour diagrams and RMS at sensitive level have significant difference when preload changes.

Abstract: The equations of damage evolution of cross-section and the deflection deformation of concrete beam were established. Through the plain concrete beam bending test, the formula for calculating the deflection was verified. It is proved that the formula established in this paper is more accurate than the equation that doesn’t consider the damage effect. The concrete beam was modelled and analyzed by means of finite element analysis software, and comparison was carried out between the numerical simulation result and the experimental data. On the basis, new methods and ideas about concrete-damage were proposed.

Abstract: The influence on coupling vibrations among shaft-torsion and blade-bending coupling vibrations of a rotor system with grouped blades was investigated analytically. The natural frequencies and the mode shapes of the system were solved with five- and six-blade cases used as examples. First, numerical results showed how the natural frequencies varied with the wire stiffness and the lacing wire mistuned. The diagrams of the coupling mode shapes were drawn. From the results, it was found that lacing wire did not affect the SB (shaft-blades) coupling modes, but the BB (inter-blades) modes were indeed affected by the lacing wire. At wire stiffness k*=10, the repeated BB modes split into more distinct modes. The BB modes were of (N-1) / 2 and N / 2 multiplicity for odd and even numbered blades. When the system has a mistuned lacing wire, it splits the BB modes and will once more have (N-1) frequencies. In the rotation effect, whatever tuned or mistuned, the lacing wires did not affect the instability. That means the instability preexisted due to rotation and was not induced by lacing wires.

Abstract: The paper deals with a numerical modeling of a three-dimensional linear hyperbolic problem. The modeling is carried out using the meshless element free Galerkin (EFG) method. In the mathematical formulation, the variational method is employed to derive the discrete equations and the essential boundary conditions are enforced by the penalty method. The effectiveness of EFG for three-dimensional hyperbolic problems is investigated by numerical example in this paper.

Abstract: The reproducing kernel particle method (RKPM) is used in this paper to find the numerical solution of modified equal width wave (MEW) equation. A variational method is used to obtain the discrete equations, and the essential boundary conditions are enforced by the penalty method. The effectiveness of the RKPM for the modified equal width equation is investigated by two numerical examples in this paper.

Abstract: Based on the principle of digital speckle correlation method (DSCM), a distance measuring DSCM system has been developed and realized. With the application of the system, the inverted camber of a pre-stressed beam of beam-slab transfer cadre was traced and analyzed in this paper. Compared with other experimental technique such as dial indicator test method, it shows that DSCM is a powerful optical deformation measurement tool with the required precision and on-site inspection ability.

Abstract: To meet the requirements of measurement and control system for common servo-cylinder and considering the characteristics of electro-hydraulic stepping cylinder, a computer measurement and control system is designed. In this paper, the working principle of hydraulic system, the structure of electrical system, the process of measurements and the functions of testing software based on LabVIEW are introduced.

Abstract: Expandable polystyrene and expandable polyethylene foams are frequently used in packaging of products. The study on their cushioning properties is important for the design of the transport package. The effect of compression speed and multiple reloading on the cushioning properties of HDEPS, LDEPS and HDEPE was studied in this paper. The results indicate that the cushioning properties of HDEPS and LDEPS are affected obviously by the compression speed, but the change of the cushioning properties for LDEPE was unconspicuous with the compression speed. LDEPE appeared obvious fatigue after twice reloads.

Abstract: The basic flat compression cushioning performance of corrugated board was studied according to the measured data from static and dynamic flat compression tests. Based on the experimental data, the nonlinear visco-elastic-plastic model of the cushion was established. The establishment of the model and successful identification of its parameters solve the problem of flat compression dynamic calculation of corrugated board, make it possible to optimize the design of cushion packaging and avoid the great amount of measuring work.

Abstract: Based on the vibration mechanics theory and system’s state equation, the state-space model of the flange bolted-joints structure is established. According to the dynamic characteristics of bolted connection, the parameters of the state-space model, such as rigidity and damping, can be identified. The accuracy of simulation model is validated, by comparing the simulation analysis results with the vibration test results, and an efficient method of recognition or fault diagnosis of bolted joints in vibratory environment is proposed.