Кафедри
Постійне посилання на розділhttps://repository.kpi.kharkov.ua/handle/KhPI-Press/35393
Переглянути
3 результатів
Результати пошуку
Документ Closed-form quaternion representations for rigid body rotation: application to error assessment in orientation algorithms of strapdown inertial navigation systems(2020) Plaksiy, Yu. A.; Breslavsky, D. V.; Homozkova, I. O.; Naumenko, K.Closed-form analytical representations of the rigid body orientation quaternion, angular velocity vector and the external moment vector satisfying kinematic equations and equations of motion are derived. In order to analyze errors of orientation algorithms for strapdown inertial navigation systems, reference models for specific rigid body rotation cases are formulated. Based on solutions, analytical expressions for ideal signals of angular velocity sensors in the form of quasi-coordinates are derived. For several sets of parameters, numerical implementations of the reference models are performed and trajectories in the configuration space of orientation parameters are presented. Numerical analysis of the drift error for the third-order orientation algorithm is performed. The results show that the value of the accumulated drift error using the derived two-frequency models exceeds the value of the accumulated drift error in the conventional case of a regular precession.Документ Cyclic creep damage in thin-walled structures(Mechanical Engineering Publications, Ltd., 2000) Altenbach, H.; Breslavsky, D.; Morachkovsky, O.; Naumenko, K.Thin-walled structural elements are often subjected to cyclic loadings. This paper presents a material model describing creep behaviour under high-cycle loading conditions (N greater than or equal to 5 x 10(4)-10(5)). Assuming that the load can be split into two joint acting parts (a static and a superposed, rapidly varying small cyclic component), the asymptotic expansion of two time-scales has been applied to the governing equations of the initial-boundary value creep problem. The system of equations determine two problems. The first is similar to the creep problem by quasi-static loading. The second is the problem of forced vibrations. Both the problems are coupled by constitutive equations. The model is applied to the simulation of the cyclic creep damage behaviour of thin-walled structural elements. The results are discussed for two special numerical examples (a conical shell and a circular plate). The simulations show that the creep and the damage rates as well as the failure time are strongly sensitive to the redistribution of the stress state cycle asymmetry parameter A(s). The values of A(s) increase during the creep process. For particular cases of the loading frequency, A(s) can exceed the critical value. In this case the material model must be extended in order to consider the creep-fatigue damage interaction.Документ On the accuracy of creep-damage predictions in thinwalled structures using the finite element method(Springer-Verlag, 2000) Altenbach, H.; Kolarow, G.; Morachkovsky, O. K.; Naumenko, K.The constitutive model with a single damage parameter describing creep-damage behaviour of metals with respect to the different sensitivity of the damage process due to tension and compression is incorporated into the ANSYS finite element code by modifying the user defined creep material subroutine. The procedure is verified by comparison with solutions for beams and rectangular plates in bending based on the Ritz method. Various numerical tests show the sensitivity of long-term predictions to the mesh sizes and element types available for the creep analysis of thinwalled structures.