关键词: 木橡胶, 减震器, 动态压缩, Johnson-Cook型本构方程, Origin软件

Abstract: [Objective]The main purposes of this paper is to analyze the mechanical properties of wood rubber shock absorber for vehicle, to obtain the Johnson-Cook constitutive equation and to check out whether the equation can exactly describe the relationships of stress and strain for wood rubber shock absorber for vehicle.[Method]We select the small Xing'an mountain Korean pine (Pinus koraiensis) wood with the density of 0.439 g·cm^-3 and moisture content of 12%, chloroprene rubber which has good elasticity, high bonding strength, flexible layer, resistant to impact and vibration is also used as experimental materials. Micrometer-level fiber forging machine is applied to process the dried red pine wood into wood fiber, then put these wood fiber into the kneading machine, and obtain the micro wood fiber with width of 1-2 mm, length of 15-30 mm. The specimens of wood rubber shock absorber for vehicle were prepared by several processes including the preparation, weighing, mixing, molding, holding pressure, unloading, and so on. Dynamic compression tests on the specimens of wood rubber shock absorber for vehicle are performed by using Split Hopkinson pressure bar, and get the curves at the strain rate of 1250 s^-1, 1500 s^-1 and 1750 s^-1, respectively. Finally, using the experimental data and Origin software to ascertain the parameters of Johnson-Cook constitutive equation, then the Johnson-Cook constitutive equation, and the experimental curve and the curve fitted by the Johnson-Cook constitutive equation is established and compared, respectively.[Result]The φ10 mm×10 mm specimens of wood rubber shock absorber for vehicle were made, the stress and strain curves at the strain rate of 1250 s^-1, 1500 s^-1 and 1750 s^-1 were obtained by dynamic compression tests, and the Johnson-Cook constitutive equation (σ=[21+0.329(ε)^1.16]×[1+0.148ln(ε·^*)]) of wood rubber shock absorber for vehicle are successfully established.[Conclusion] By analyzing the stress and strain curves of wood rubber shock absorber for vehicle, we can see that the wood rubber shock absorber is sensitive to the strain rate, it can realize a large deformation, the maximums flow stress are higher than 12 MPa under the three strain rates in this study, this is far more than the maximum allowable stress of cellular rubber and neoprene which are widely used as shock absorbing in the present. Furthermore, the toughness and energy absorption properties of wood rubber are also better than chloroprene rubber and cellular rubber. After dynamic compression tests, the specimen of wood rubber shock absorber for vehicle showed 45°splitting damage on surface when the strain rate is 1500 s^-1, and the destruction is mainly occurred on gum. The fitting degree of the experimental curve and the curve fitted by the Johnson-Cook constitutive equation is good when the strain is smaller, especially at the strain rate of 1250 s^-1 and a strain of less than 0.056, the fitted value is almost completely coincide with the experimental value.

Key words: wood rubber, shock absorber, dynamic compression, constitutive equation of Johnson-Cook, Origin software