The stress relaxations of HNBR were studied by molecular dynamics (MD) simulation.The structure of hydrogenated nitrile butadiene rubber (HNBR) was constructed and several circles of energy minimization (MM) and MD simulation were applied.The distribution function of gyration radius was calculated under different compression ratios and temperatures.The fitting functions of normal stress with time under different pressures were obtained.Compression stress relaxation experiment of different compression ratios was also conducted.Comparing with the coefficient of stress relaxation from the experiment

it was found that the theoretical stress relaxation curves were similar to the experimental data.The results indicated that the mean-square radius of gyration decreased with the enhancement of pressure and it decreased with the reduction of temperature

which corresponded to the typical viscoelasticity stress relaxation behaviors of polymers.It is confirmed that the variation of mean-square radius can be used to quantitatively describe the stress relaxation of rubber system and a good agreement between the theoretical curves with the experimental data can be obtained from MD simulation.