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Abstract：The piecewise linear model of friction draft gear is modified by the additional sticking friction force and the additional damping force based on vehicle impact data; train air brake characteristic multi-parameter mathematic method is used to study heavy haul train brake characteristic; on the basis of draft gear dynamic modification model and air brake multi-parameter mathematic method, the heavy haul train longitudinal impulse dynamics of different line conditions and brake operation is analyzed . The results show that the draft gear piecewise linear dynamic modification model can actually reflect the hysteresis characteristic of draft gear, nonlinear peak and smooth transition between loading curve and unloading curve; the results of air brake multi-parameter mathematic method agrees well with the test in the emergency and service braking operation; longitudinal train dynamic model can simulate Daqin heavy haul train longitudinal impulse problems, which agrees well with the test of train running.Key words：heavy haul train；longitudinal impulse；draft gear dynamics；air brake 0 前言 *

An omnidirectional inertial switch with rectangular spring is proposed in this paper, and the prototype has been fabricated by surface micromachining technology. To evaluate the threshold consistency and stability of omnidirectional inertia switch, the stiffness of rectangular suspension springs is analyzed. The simulation result shows that the coupling stiffness of the rectangular spring suspension system in the non-sensitive direction is a little more than that in the sensitive direction, which indicated that the omnidirectional switching system’s stability is reinforced, attributed to the design of rectangular springs. The dynamic response simulation shows that the threshold of the omnidirectional inertial switch using the rectangular suspension spring has high consistency in the horizontal direction. The prototype of an inertial switch is fabricated and tested successfully. The testing results indicate even threshold distribution in the horizontal direction. The threshold acceleration of the designed inertial switch is about 58 g in the X direction and 37 g in the Z direction; the contact time is about 18 μs.

Based on the invariant theory of continuum mechanics by Spencer, the strain energy depends on deformation, fiber direction, and the gradients of the fiber direction in the deformed configuration. The resulting extended theory is very complicated and brings a nonsymmetric stress and couple stress. By introducing the gradient of fiber vector in the current configuration, the strain energy function can be decomposed into volumetric, isochoric, anisotropic, and bending deformation energy. Due to the particularity of bending deformation, the reinforced material has tensile deformation and compression deformation. The bending stiffness should be taken into consideration, and it is further verified by the bending simulation.

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