Applied Mechanics and Materials Vols. 275-277

Abstract: Transfer function (TF) for linear time invariant system and optical transfer function (OTF) for linear space shaft invariant system are compared and contrasted. TF is the unilateral Laplace transform of system’s one-dimensional unit impulse response, dimensions of the input and output may be same or different, TF can be used to describe a variety of filter or to express solution of linear differential equations accurately. But OTF is the Fourier transform of system’s two-dimensional impulse response, dimensions of the input and output must be same, OTF can be used only to describe a low-pass filter or to express solution of the linear univariate partial differential equations approximately. Their eigenfunctions are similar complex exponential functions. OTF has stricter requirements and application conditions than TF. It is helpful to the readers’ understanding of TF and OTF.

Abstract: Modeling structures response to external blast loads is studied in this paper. A new model is developed based on the experimental data in literature UFC (unified facilities criteria) 3-340-2. The new model differs from the model which is available in LS-DYNA as take into account new abacuses for reflecting coefficients, leading to more precise load especially at great incidence.

Abstract: In this paper, the double pendulum model of the pantograph was developed, in which a square angular velocity damping torque was used to describe the nonlinear damping torque of the hydraulic vibration damper, and the catenary was described as a variable stiffness spring. Considering the nonlinear factors caused by hydraulic damping and the interaction between the catenary and the pantograph, the motion differential equations based on the double pendulum model were established in Lagrange equation, and then were simplified. The dynamic characteristics were analyzed through numerical simulation. The result of numerical simulation shows that there are quasi-periodic motion and chaos in the system, which are both affected by the pendulum length ratio. The results are helpful to research the dynamic characteristics of the pantograph of high-speed train.

Abstract: A shear magnetic rheometer with a dual MRF shear region has been designed. The effect of magnetic rheometer gap MRF magneto-rheological on the torque measurement has been took full account, so the measurement accuracy improved. The design process using the Equivalent Magnetic Circuit Method to calculate the reluctance of each local area of magnetic rheometer, and use magnetic potential equation calculate the number of coils required for magnetic rheometer. Finally, used ANSYS software simulation analysis of the magnetic field of the magnetic rheometer, proposed fractional differential equations to describe the relationship between the MRF shear stress, shear rate and time, and using nonlinear least-squares method to fit the coefficients of fractional differential equations. The results show that the magnetic field of the two MRF regions is evenly distributed and the difference in the magnetic flux density of the two MRF regions within the ideal range; Coefficients and orders of fractional differential equations affected by the magneto-rheological fluid nature and speed.

Abstract: This paper studies the spacecraft attitude maneuver optimization problem. The maneuver aim is to avoid fuel cost by only using CMGs in the maneuver course. The nonlinear dynamic equations of the attitude system are established, the attitude maneuver optimization is depicted into a two point boundary value problem (TPBVP). The adjoint method is used to convert the TPBVP into the initial value problem. Numerical results indicate that the adjoint method is efficiently capable for attitude maneuver optimization.

Abstract: In order to explore earth penetrator’s effective destruction to the runway, using numerical simulation as the main means, and combined with some experimental data, a study on the intrinsic connection between series of charge weight, different depth of the burst point and damage area of the runway (blasting crater area) is carried out. The results shows that: for the same charge weight of earth penetrator, there is an optimum depth of the burst point (best penetration detonation depth), and the law which is got from numerical simulation is consistent with the experimental one, which indicates that the material model and calculation parameters of numerical simulation are reasonable, the numerical simulation can replace some research experiment and accelerate research progress.

Abstract: Such as the canonical equation of force method’s free terms and coefficients are different from the primary structures, can obtain by the internal forces of the primary structure. This paper demonstrates the correctness and rationality, as well as the applicable range from theory.And the creation of a new method to solve statically indeterminate structure, said this method is the multiple primary structure of force method.

Abstract: Thin-walled tubes are generally used as impact energy absorber in various application due to their ease of fabrication and installation, high energy absorption capacity and long stroke. However, the main drawback of plain tube is the high initial peak force. A concentric plunger in the form of tapered block is proposed to overcome this shortcoming while at the same time, improving the impact performance. Static and dynamic axial crushing were performed to determine the initial peak force (IPF), crush force efficiency (CFE) and specific energy absorption (SEA) for the concentric plunger with various taper angles. It was found that the concentric plunger affected the tube impact response. Comparison with plain circular tube was carried out and it was found that the concentric plunger improved the impact response of the tube especially in term of initial peak force.

Abstract: Wheelchairs with posture change functions are required by clinicians to assist activities of daily living for handicapped people. In this paper, the mechanism of a wheelchair with self-actuated seating functions was designed and its degree of freedom was introduced. Link length was determined based on ergonomics and anthropometry to meet national standards. Kinematics simulation was carried out in MATLAB to investigate the working characteristics of the wheelchair and prove the feasibility of the scheme. Humanized design was explored which was based on ergonomics to satisfy the safety, comfort and efficiency.

Abstract: The fore-angle and the lateral-rotation angle of PDC core bits, which are two main geometric parameters, have an important influence on the cutting efficiency and performance. Previous studies determined the ranges of two angles mainly depending on the effect of broken rock rather than its mechanical strength to examine the issue. Based on the strength factors, the paper uses finite element program ANSYS to optimize the fore-angle and the lateral-rotation angle of PDC cutters. The main geometric parameters are optimized and the optimal values are obtained under different circumstances, which provides a theoretical basis for reasonable design of the PDC core bits.