Objective: to investigate the issue of enhancing the service life and reliability of locomotives’ traction electric motors (TEM). To evaluate the effect of thermomechanical stress on lifespan of their insulation materials. Methods: the main methods of studying and calculating temperature fields are the theory of heat transfer in multilayer materials and the finite element method, implemented in the SolidWorks software package. Results: the research results have demonstrated that thermal-mechanical stresses play a significant role in the dynamic thermal aging of the TEM winding insulation system. A methodology for numerical investigation of the stress-strain state of the TEM insulation material at various stages of static and cyclic loading has been developed. The study has established that the main factor determining the intensity of insulation aging is the influence of alternating cyclic thermomechanical stresses, rather than thermochemical degradation of the impregnation composition. Analytical expressions have been obtained to assess the stress-strain state of TEM insulation. These expressions vary in that they require comparatively less initial data and enable strength calculations that account for specific features of the electric drive system. An approximate predictive model has been developed to assess interfacial thermal stresses in the assembly of TEM slot-winding materials. The insulating material is assumed to behave as a linear-elastic medium at strain levels below the yield point. From a structural-analysis perspective, the bonded components can be modelled as elongated rectangular plates subjected to linear elastic deformations. Practical significance: the results of the analysis can be used to evaluate thermomechanical stresses in impregnation materials of traction motors and analogous systems. The developed techniques for assessing the stress state of TEM insulation can be recommended for practical application.