Stiffness identification of four-point-elastic-support rigid plate

As the stiffness of the elastic support varies with the physical-chemical erosion and mechanical friction, model catastrophe of a single degree-of-freedom(DOF) isolation system may occur. A 3-DOF four-point-elastic-support rigid plate(FERP) structure is presented to describe the catastrophic isolation system. Based on the newly-established structure, theoretical derivation for stiffness matrix calculation by free response(SMCby FR) and the method of stiffness identification by stiffness matrix disassembly(SIby SMD)are proposed. By integrating the SMCby FR and the SIby SMD and defining the stiffness assurance criterion(SAC), the procedures for stiffness identification of a FERP structure(SIFERP) are summarized. Then, a numerical example is adopted for the SIFERP validation, in which the simulated tested free response data are generated by the numerical methods, and operation for filtering noise is conducted to imitate the practical application. Results in the numerical example demonstrate the feasibility and accuracy of the developed SIFERP for stiffness identification.

风沙流冲击角度对其侵蚀床面能力的影响

以黄土作为风蚀床面材料,通过风洞实验来揭示冲击角度对风沙流侵蚀能力的影响。在净风条件下,无论风速多大,不会产生风蚀;蠕移砂粒对床面的摩擦侵蚀量也很少,在0.27~1.33 g/（min.m2）;跃移砂粒对床面的冲击侵蚀率较大,侵蚀量随风速呈指数增加。冲击角度对风蚀率的影响很大,在风速为10 m/s时,倾角30°样品的风蚀率是0°时的2.66倍,在风速为15 m/s时,倾角30°样品的风蚀率是0°时的6.6倍,风速越大,相差倍数越大。在风速大于12 m/s时,风蚀率随样品放置角度（床面的坡度）的增大而增大,尤其是0°~20°时,风蚀率随角度增加的速率很快。在低风速条件下（〈12 m/s）,存在一个最大侵蚀角度,这个角度在30°左右。