The use of mathematical modeling of viscoelasticity combined with computerized methods of predicting viscoelastic processes in synthetic materials increases the accuracy of calculating deformation processes, including deformation-recovery and reverse-relaxation processes, close to the conditions of use of the articles. Computerization of methods of separating the mechanical work of deformation into elastic and scattering components will allow solving problems of calculating the resistance of synthetic materials to impact loads. A computer-integral criterion of the reliability of the prediction is suggested for increasing the reliability of calculating deformation processes in synthetic materials in selecting a variant of normalized relaxation and lag functions.