THE INVESTIGATION OF DYNAMIC EFFECTS UNDER MICROSCALE PULSE LOAD

2021 ◽  
Vol 4 ◽  
pp. 61-68
Author(s):  
Nina Yakovenko ◽  
◽  
Andrey Bondarchuk ◽  
Oksana Kovalchuk ◽  
◽  
...  
Keyword(s):  
Phase Composition ◽  
Strain State ◽  
Equations Of Motion ◽  
Iteration Process ◽  
Pulse Load ◽  
System Of Nonlinear Equations ◽  
Time Step ◽  
Stress Strain ◽  
Stress Strain State ◽  
Inelastic Material

Axisymmetric problem of heat pulse irradiation of a cylindrical solid is considered. Nonlinear behavior of the material is described by the generalized Bodner-Partom model of flow. The nature of generalization lies in applying the rule of mixtures for the determination of parameters of the model responsible for yield point and ultimate strength. The considered model enables one to estimate the residual stress-strain state more exactly. During subsequent in-service loading of cylindrical solids, this state strongly affects the fatigue resistance of elements. The problem is solved by the time step integration method, iterative method, and finite element method. In each time step, we realize a double iteration process. The first is connected with the integration of the system of nonlinear equations of flow, the second with the solution of equations of motion and heat conduction. The calculations are performed on a grid FEM, especially in the region of irradiation, for the correct modeling of thermomechanical behavior of the material. The grid parameters are chosen with the help of the criterion of practical convergence of the solutions. The investigation of the stress-strain state of an inelastic material with regard for the dependence of parameters of the flow model on the phase composition of a material is carried out by using of numerical simulation. The main result is the following: qualitative and quantitative effects of phase composition influence on inelastic characteristics are established, namely change of tensile residual stresses on compression. The results obtained in the work can be used in calculations of parameters of surface hardening technologies.

NUMERICAL INVESTIGATION OF THERMOMECHANICAL PROCESSES UNDER SHORT-PULSED LASER IRRADIATION OF A HALF-SPACE

2021 ◽  
Vol 6 ◽  
pp. 55-65
Author(s):  
Kamila Storchak ◽  
◽  
Nina Yakovenko ◽  
Olga Polonevych ◽  
Irina Sribna ◽  
...  
Keyword(s):  
Residual Stress ◽  
Laser Irradiation ◽  
Half Space ◽  
Strain State ◽  
Thermal Stresses ◽  
Equations Of Motion ◽  
Thermomechanical Loading ◽  
Stress Strain ◽  
Stress Strain State ◽  
Residual Strains

The laser irradiation of metallic surfaces by intense heat sources is used for the generation of short probing pulses, which propagate into thin specimens and enable one to estimate their structure and mechanical properties within the framework of the classical acoustic approach. High thermal stresses and residual strains occur during the short-term irradiation of the surface of a construction by an energy source of high density. In the present work, we solve the axially symmetric problem of a half-space under thermomechanical loading. We take into account the influence of volume and inelastic characteristics of separate phases on the residual stress-strain state of the half-space. The statement of the problem includes: Cauchy relations, equations of motion, heat conduction equation, initial conditions, thermal and mechanical boundary conditions. The thermomechanical behavior of an isotropic material is described by the Bodner-Partom unified model of flow. The problem is solved with using the finite element technique. The numerical realization of our problem is performed with the help of step-by-step time integration. The equations of motion are integrated by the Newmark method. The residual stress-strain state is described using the method of numerical solution of the axisymmetric dynamic problem for a half-space under thermomechanical loading and the flow model. We established that microstructural transformations, which are taken into account due to the thermophase volume strain and dependence of inelastic characteristics of the material on the phase composition, significantly reduce residual inelastic strain and promote the appearance of compressive stresses. The three-zone region of residual stresses field formation is obtained.

scholarly journals Stress-strain state of a three-layer cylindrical shell under internal axisymmetric pulse load

2020 ◽  
pp. 145-151
Author(s):  
Viktor Gaidaichuk ◽  
Kostiantyn Kotenko
Keyword(s):  
Finite Element ◽  
Cylindrical Shell ◽  
Strain State ◽  
Layer Structure ◽  
Three Dimensional ◽  
Pulse Load ◽  
Geometrical Parameters ◽  
Time Interval ◽  
Stress Strain ◽  
Stress Strain State

The problem of dynamic deformation of a three-layer cylindrical shell under non-stationary loads in the case of rigid clamping of the shell ends is considered. The article presents the results of assessing the stress-strain state of a three-layer cylindrical shell, taking into account its structural feature, the ratio of the sheathing thickness and the physical and mechanical characteristics of a one-piece polymer filler. Calculations were performed by software complex Nastran. The values of displacements and stresses were calculated by the algorithm of direct transient dynamic process. The step duration of the time interval was 0.0000025 s, and the total number of steps was 200. The choice of the type of three-dimensional finite element was due to obtaining more detailed and accurate calculation results. The finite element model included 19000 three-dimensional finite elements and numbered 20800 nodes. The influence of geometrical parameters of shell layers with different physical and mechanical properties of one-piece filler on the stress-strain state under axisymmetric internal impulse load is investigated. Numerical results on the dynamics of the three-layer structure, obtained by the finite element method, allow to characterize the stress-strain state of the three-layer elastic structure of the cylindrical type at any time in the studied time interval. Optimization of the shell design is recommended. Changing the ratio of the thickness of the internal and external shells of the shell significantly affects the stress-strain state of the shell and its performance. Increasing the thickness of the internal layer of the shell significantly contributes to the increase of the latter. Comparison of the given results with materials of other similar researches and positions, testify to objectivity of the made approach.

scholarly journals Stress-strain state analysis and optimization of rod system under periodic pulse load

2018 ◽  
Vol 143 ◽  
pp. 01003
Author(s):  
Grigory Grebenyuk ◽  
Maxim Veshkin ◽  
Vladislav Maksak ◽  
Olga Nosireva
Keyword(s):  
Strain State ◽  
Equations Of State ◽  
Traditional Approach ◽  
Pulse Load ◽  
Stress Strain ◽  
Stress Strain State ◽  
Periodic Pulse ◽  
Rod System ◽  
Nonlinear Mathematical Programming ◽  
Homogeneous Matrix

The paper considers the problem of analysis and optimization of rod systems subjected to combined static and periodic pulse load. As a result of the study the analysis method was developed based on traditional approach to solving homogeneous matrix equations of state and a special algorithm for developing a particular solution. The influence of pulse parameters variations on stress-strain state of a rod system was analyzed. Algorithms for rod systems optimization were developed basing on strength recalculation and statement and solution of optimization problem as a problem of nonlinear mathematical programming. Recommendations are developed for efficient organization of process for optimization of rod systems under static and periodic pulse load.

scholarly journals Stress-strain state analysis and optimization of rod system under periodic pulse load

2018 ◽  
Vol 143 ◽  
pp. 01003
Author(s):  
Grigory Grebenyuk ◽  
Maxim Veshkin ◽  
Vladislav Maksak ◽  
Olga Nosireva
Keyword(s):  
Strain State ◽  
Pulse Load ◽  
Stress Strain ◽  
Stress Strain State ◽  
Periodic Pulse ◽  
Rod System ◽  
State Analysis

КОНСТРУКТИВНО-ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ ХВОСТО-ВИХ БАЛОК СІТЧАСТОГО ТИПУ З ПОЛІМЕРНИХ КОМПО-ЗИЦІЙНИХ МАТЕРІАЛІВ ВЕРТОЛЬОТІВ ТРАНСПОРТНОЇ КАТЕГОРІЇ

2020 ◽  
pp. 15-30
Author(s):  
А. Г. Гребеников ◽  
И. В. Малков ◽  
В. А. Урбанович ◽  
Н. И. Москаленко ◽  
Д. С. Колодийчик
Keyword(s):  
Finite Element ◽  
Strain State ◽  
Layer Structure ◽  
Metal Structure ◽  
Element Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Mesh Structure ◽  
Stress Strain State ◽  
Mesh Structures

The analysis of the design and technological features of the tail boom (ТB) of a helicopter made of polymer composite materials (PCM) is carried out.Three structural and technological concepts are distinguished - semi-monocoque (reinforced metal structure), monocoque (three-layer structure) and mesh-type structure. The high weight and economic efficiency of mesh structures is shown, which allows them to be used in aerospace engineering. The physicomechanical characteristics of the network structures are estimated and their uniqueness is shown. The use of mesh structures can reduce the weight of the product by a factor of two or more.The stress-strain state (SSS) of the proposed tail boom design is determined. The analysis of methods for calculating the characteristics of the total SSS of conical mesh shells is carried out. The design of the tail boom is presented, the design diagram of the tail boom of the transport category rotorcraft is developed. A finite element model was created using the Siemens NX 7.5 system. The calculation of the stress-strain state (SSS) of the HC of the helicopter was carried out on the basis of the developed structural scheme using the Advanced Simulation module of the Siemens NX 7.5 system. The main zones of probable fatigue failure of tail booms are determined. Finite Element Analysis (FEA) provides a theoretical basis for design decisions.Shown is the effect of the type of technological process selected for the production of the tail boom on the strength of the HB structure. The stability of the characteristics of the PCM tail boom largely depends on the extent to which its design is suitable for the use of mechanized and automated production processes.A method for the manufacture of a helicopter tail boom from PCM by the automated winding method is proposed. A variant of computer modeling of the tail boom of a mesh structure made of PCM is shown.The automated winding technology can be recommended for implementation in the design of the composite tail boom of the Mi-2 and Mi-8 helicopters.

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