Annotation: The paper proposes a method for investigating structural strength and determining structural failure loads by computer-aided simulation and nondestructive testing. The methodology is grounded on general ratios of elastoplasticity in increments based on the Lagrangian approach and the principle of virtual translations, taking into account the geometrically nonlinear nature of structural deformation under intense loading. The baseline technique for numerical simulation was the fi nite element method. The methodology for structural strength investigation includes three steps. The fi rst step involves studying the structure in the form of a spatially two-dimensional shell-like model. An analysis of the calculated values of the model’s stress and strain is performed based on the results of the computational experiment, and the critical regions within the structure are determined, where these parameters reach their peak values. The second step yields detailed three-dimensional models of those critical regions within the structure. These models incorporate the geometrical (including the actual thicknesses of the elements) and physical specifi cs of the structure. The results of numerical experiments are applied in an analysis of the refi ned stress and strain values of the three-dimensional models, and the minimum structural failure load is determined. In the third step, strain gauges are installed in the determined critical regions, and the structure’s strength is tested using a nondestructive load. A predicted structural failure load is found by comparing the strain and translation values obtained from the test results with the outputs of computational experiments. The development of the mentioned methodology encompassed an investigation of stress and strain at diff erent internal pressures for an oxidizer tank of a launch vehicle’s fi rst stage, a quantitative estimation of the tank’s strength, and the determination of the structural failure load and regions where a structural failure is likely to start. This paper demonstrates that the results of a tank strength analysis using a criterion of a maximum stress are closest to experimental data.

Annotation: This paper describes the effective approach for the technology of the rocket airframe development testing, based on the method of numerical modelling, which enables the virtual experimental runs prior to the beginning of the development testing to check the performance of the standard airframes and predict issues of concern. The method is realized based on the computer models developed in the ANSYS Workbench environment. Based on the offered method the complex mechanical system, which attaches the cluster projectiles in the conditions of the temperature exposure and heat cycling, underwent the virtual tests. Computational models, criteria and test procedures necessary for the analysis of the mechanical condition and prediction of the performance of the actual airframe of the warhead were developed. Moreover, computational models consider all the design and technological features of the airframe: layout of the projectiles attachments, initial stress-strain state of the system after the tightening of the threaded connections, friction between the components of the system and their mutual displacement, temperature dependence of the physical and mechanical characteristics and ultimate stress of materials. For the specified loading conditions during the ground operations with the warhead, the most dangerous computational cases are determined which have been implemented during the virtual tests. Test results were used to conduct the static analysis of the mechanical condition, strength and conditions for performance of the actual structure of the attachment under the impact of the operating levels of temperature exposure and heat cycling. Results of the virtual tests confirm the performance of the projectiles attachment system and are introduced into production in the phase of engineering development.

Annotation: The basic results of the design calculations and mathematical modelling of the control processes in the precision high-speed servo drive are presented, as well as results of experimental studies of the functional mock-up of this servo drive’s movable gears of the throttle and fuel flow regulator of the ILV main engine. Major task of the studies was theoretical and experimental verification of the required static and dynamic accuracy of the servo drive in the process of try-out of the command signals reception from the main engine’s controller. In the phase of development, theoretical study of the linearized servo drive with application of transformations and theorems of Laplace passages to the limit is conducted. Analytical dependences between servo drive circuit parametres, its elements and characteristics of the control signals are obtained. Instrument errors and servostatic elasticity of the servo drive are calculated. Calculation model including the basic nonlinearities of this servo drive is prepared. Mathematical modelling of the control processes is conducted according to the computational model, varying the circuit and design parameters of the electric drive. Results of the theoretical studies were taken as input data for the requirements specification document to develop the executive unit with the electromotor, reduction gear and output shaft position sensor, and the control box. Functional mockups of the executive unit, control box, as well as the computer-controlled technological test console were manufactured on the basis of the requirements specification documents. The required scope of the laboratory-development tests of the functional mock-up of the servo drive was conducted. Results of the conducted activities confirm the achievement of the required accuracies of the servo drive in the laboratory environment.