Wu Chia-Chin, Chiou Yung-Chuan
Department of Mechanical and Energy Engineering, National Chiayi University, Chiayi 60004, Taiwan.
Department of Biomechatronic Engineering, National Chiayi University, Chiayi 60004, Taiwan.
Materials (Basel). 2019 Jan 16;12(2):282. doi: 10.3390/ma12020282.
The study was devoted to the observation and modeling the mechanical behaviors of a hybrid SBR/NR (Styrene-Butadiene/Natural Rubber) hybrid vulcanized rubber fender under monotonic/cyclic compression. In experimental observations of the monotonic compression tests, it was found that lateral deformation occurred on the tested fender and was more significant with increasing the extent of the compressive strain. The relationship between the transmission stress S c and the compressive strain e c was nonlinear and the absorbed strain-energy-density was increased monotonically with the increment of the compressive strain. Among all cyclic compression tests with strain controlled, the reductions in both the stress range and the absorbed strain-energy-density up to the ten-thousandth cycle were found and then both of the cyclic properties remain approximately constant in the following compression cycles. Two new properties, the softening factor and the energy reduction factor, were introduced to quantify the effect of the strain range on the extent of the reduction in stress range and that on the absorbed strain-energy-density, respectively. It was found that both of the calculated values of the new properties increase with the increment of strain range. In mathematical modeling of the relationship between the transmission stress and the compressive strain, a new approach based on energy-polynomial-function E s ( e c ) was presented and was successfully used to simulate the monotonic curve and the stable hysteresis loop curves of the tested rubber fender in compression. Essentially, the energy-polynomial-function E s ( e c ) was obtained by performing a polynomial regression on a large amount of ( e c , E s ) data. Moreover, the least-square approach was applied to determine the corresponding regression coefficients in E s ( e c ) . Clearly, the stress-polynomial-function in modeling the S c - e c curve could be obtained from the differentiation of the energy-polynomial-function with respect to the compressive strain. In addition, to provide an adequate estimation of the mechanical properties of the cylindrical rubber fender under compression, the named cyclic stress-strain curve and cyclic energy-strain curve were developed and also modeled in this study.
该研究致力于观察和模拟一种丁苯橡胶/天然橡胶（SBR/NR）混合硫化橡胶护舷在单调/循环压缩下的力学行为。在单调压缩试验的实验观察中，发现受试护舷出现横向变形，且随着压缩应变程度的增加而更加显著。传递应力(S_c)与压缩应变(e_c)之间的关系是非线性的，吸收的应变能密度随压缩应变的增加而单调增加。在所有应变控制的循环压缩试验中，发现直至第一万次循环应力范围和吸收的应变能密度均有所降低，且在随后的压缩循环中两者的循环特性均保持近似恒定。引入了两个新特性，即软化因子和能量降低因子，分别用于量化应变范围对应力范围减小程度以及对吸收的应变能密度减小程度的影响。发现这两个新特性的计算值均随应变范围的增加而增加。在传递应力与压缩应变关系的数学建模中，提出了一种基于能量多项式函数(E_s(e_c))的新方法，并成功用于模拟受试橡胶护舷在压缩时的单调曲线和稳定滞后回线曲线。本质上，能量多项式函数(E_s(e_c))是通过对大量((e_c, E_s))数据进行多项式回归得到的。此外，应用最小二乘法确定(E_s(e_c))中的相应回归系数。显然，在模拟(S_c - e_c)曲线时的应力多项式函数可通过能量多项式函数对压缩应变求导得到。此外，为了充分估计圆柱形橡胶护舷在压缩下的力学性能，本研究还开发并模拟了所谓的循环应力 - 应变曲线和循环能量 - 应变曲线。
