Multistage planetary gear transmission system has been widely utilized in engineering practice due to the salient characteristics, such as high bearing load and large speed ratio. This paper addresses a two-stage planetary gearbox and establishes a system coupling torsional dynamical model which considers the time-varying mesh stiffness, friction forces, and interstage coupling factors. Meanwhile, the friction and lubrication states are classified to comprehensively analyze the calculation of friction coefficients under different conditions. Considering the time-varying influence of friction on the tooth surface under the condition of fluid lubrication, the vibration response under parametric excitation is solved by a numerical method. A multistage planetary transmission test bench is built in the back-to-back form so as to test the vibration of the two-stage planetary gearbox. It shows that the simulation results of the dynamical model are consistent with the test data. Consideration of the calculation of friction on the tooth surface and the friction coefficients is helpful for the establishment of the more accurate dynamical model and lays the foundation for the structural design, fault diagnosis, and dynamic optimization of the multistage planetary gear transmission system.
AIM:To determine the activities of polysaccharide extracts from Flammulina velutipes (Curt. ex Fr.) Sing (FV), Lentinus edodes (LE)and Agaricus bispo-rus Sing (AB) on the proliferation of human hepatoma SMMC-7721 cells in vitro and on mouse implanted S-180 tumors in vivo.METHODS:The polysaccharide extracts were isolated from the fruit bodies of FV, LE and AB by the methods of hot-water extraction,Sevag's removal of proteins, ethanol precipitation, trypsin digestion and ethanol fractional precipitation. Human hepatoma SMMC-7721 cells were treated with 50mg/L polysaccharide extracts, and the mitosis index, mitochondria activity and cell proliferation were detected at different times in both control and experimental groups. The mice with S-180 implanted tumors were injected with the polysaccharide extracts at 24mg/kg body weight for 9d and the tumor weight was measured on the 15th day.RESULTS:The mitosis index of hepatoma cells in vitro could be significantly decreased by treatment with the polysaccharide extracts from the three kinds of edible fungi (P< 0.005). The cell numbers and mitochondria activity of SMMC-7721 cells treated with polysaccharide extracts were lower than those in control groups (P<0.005). The inhibition rates of polysaccharide extracts against implanted S-180 tumors in mice were 52.8%, 56.6% and 51.9% respectively compared with that in control groups.CONCLUSION:The polysaccharide extracts from the three kinds of edible fungi could inhibit not only the cultured malignant cells in vitro but also implanted S-180 tumor in vivo.
Four finite element models of a slewing bearing with different supporting structures are established by the finite element software ANSYS. In these models, the ball–race contact is simplified by the spring element with the same contact stiffness. The nut and bolt head are simplified and coupled with the surface of other connected component. The preload is applied on the bolt by a few pretension elements. The ball–race contact forces, fatigue lives, and carrying capacities of the slewing bearing in the four models are calculated. The effects of supporting stiffness, bolt number, and bolt preload on the contact force and fatigue life of the slewing bearing are studied. Moreover, the effects of supporting stiffness, bolt number, bolt preload, ball–race contact truncation, and bolt–hole backlash on the carrying capacities of the slewing bearing are analyzed. Results show that the fatigue life and carrying capacity of the slewing bearing can be enhanced by appropriately decreasing the supporting stiffness. Optimal values of bolt preload and number for the fatigue life and carrying capacity of a specific slewing bearing are obtained.
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