The scientific and technical task of development and implementation of methods is solved in the dissertation. It provides development and implementation of methods for strength assurance of thin-walled structures that operate in conditions of geometric and physical nonlinearity basing on construction and use of the response functions approximations.
An object of the research: a strength of the thin-walled mechanical engineering structures in the operation with a difficult change of parameters taking into account geometric and physical nonlinearities.
Methods of solid-state three-dimensional modeling and method of generalized parametric modeling of complex and complicated mechanical systems are used for parametric models creation of investigated structures; methods of continuous mechanics – for stress-deformed state analysis of thin-walled engineering structures; finite element method – for investigated structures discretization and for solving analysis tasks of investigated states and process, finite difference method – to calculate the derivative response function during implementation of algorithm for finding a rational constructive parameters combination of investigated objects.
The scientific novelty of obtained results is to develop an approach to providing strength assurance of thin-walled structures that operate in conditions of geometric and physical material nonlinearity by substantiating the parameters with use of response surfaces approximations. New tasks were solved and following regularities were found:
1) new approach to validation of design solutions for thin-walled engineering structures with varying design, technical parameters and operating conditions is developed on the basis of minimization of approximated target function (as opposed to traditional approaches in which the actual response function is used) taking into account geometrically and physically non-linear material behavior of thin-walled structural elements, which makes it possible to more efficiently determine rational parameters of these structure;
2) method of response surface approximation in part of refining its appearance as it approaches the solution is improved, this creates conditions for reduce computation volume of response function values compared with known methods while maintaining an acceptable solution accuracy;
3) character of stress-strain state dependencies of a number of thin-walled mechanical engineering structures on the basis of design parameters is found, which is the basis of formation of response surfaces approximation in synthesis of rational solutions according to different criteria.
The developed approach gives possibility to simultaneously consider different criteria for parameters validation, including characteristics of strength, rigidity, technological and economic factors. These criteria are added into the objective function with weighted coefficients. Constraints on parameters allowable values are taken into account by adding into the objective function of penalty functions. For sensitivity evaluation of individual values to parameters variation, using of finite-difference ratios is proposed. Approximated objective function reflects global trend of decision-changing. This allows, in most cases, to find a sustainable, rational technical solution close to optimal.
The developed specialized program-model complex includes three main components: parametric models, created specially for a concrete investigated object or class of objects; program modules that operate with object data and vary the numerical model; an expert to control all research stages.
The dissertation research results are of interest for implementation in research institutes, design bureaus and directly at enterprises involved in the design, manufacture and operation of thin-walled engineering products (or products containing thin-walled elements), which operate in conditions of complex loading regimes under large displacements and deformations, which significantly exceed elastic ones. These are a rolling stock of rail transport (wagons, tanks, platforms and other), military technics, quarry excavators, dumpers, reloaders etc.
Recommendations of rational design of thin-walled elements of freight cars, hulls of lightly armored vehicles, buses hulls and tractors cabins. The potential value of these developments is for elements of mining equipment, lifting and transport vehicles, military and civilian vehicles, ships, wind power plants, etc.
The program complex created was introduced into the practice of design works at JSC "Science Engineering Center of MC "RailTransHolding" (Mariupol) and the SE "V.O. Malyshev Plant" (Kharkiv).
