Generally, polymeric materials exhibit strong time-temperature dependence and viscoelastic behavior, and the time-temperature superposition principle is typically used to estimate their long-term viscoelastic behavior.In addition,Mises and Tresca criteria have been proposed to estimate the yield and failure of isotropic materials exposed to multiaxial stress. The Christensen failure criterion,on the other hand,can be applied for isotropic materials with different tensile and compressive

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... s. In this study, using a molecular dynamics method, uniaxial and multidirectional tensile and compression test simulations were performed for polypropylene using various strain rates ( 2.16×10 , 2.16×10 , and 2.16×10 s ) and temperatures (200, 250, and 300K) . The resulting stress-strain curves showed non-linear behavior,and thecompressivestresses werehigher than the tensile stresses.In addition,the fracture stress was increased at a low temperature or high strain rate, and these failure stresses are in good agreement with the Christensen failure criterion curves. Furthermore, time-temperature superposition principle was applied for the relationship between failure stress and failure time. Consequently, long-term viscoelastic behavior could be estimated from the short-term viscoelastic behavior at different temperatures.