Study of the stress-strain state in concentration zones of die elements under low-cycle loading

1983 ◽  
Vol 15 (7) ◽  
pp. 920-925
Author(s):  
V. I. Dobrovol'skii
Keyword(s):  
Strain State ◽  
Stress Strain ◽  
Stress Strain State ◽  
Cycle Loading

ANALYSIS OF THE KINETICS AND DIRECTIONALITY OF ELASTOPLASTIC DEFORMATION AND FRACTURE

2019 ◽  
Vol 85 (6) ◽  
pp. 47-52
Author(s):  
N. A. Makhutov ◽  
I. V. Makarenko ◽  
L. V. Makarenko
Keyword(s):  
Numerical Methods ◽  
Fracture Mechanics ◽  
Fracture Surface ◽  
Elastoplastic Deformation ◽  
Strain State ◽  
Stress Strain ◽  
Nonlinear Fracture Mechanics ◽  
Stress Strain State ◽  
Nonlinear Fracture ◽  
Cycle Loading

Safety, survivability, and serviceability of the equipment are governed by the strength characteristics of the separate units and elements which can contain initial or operational defects such as superficial differently oriented semi-elliptical cracks. Numerical methods of calculation provide a large bulk of information about the stress-strain state (SSS) of those elements proceeding from the given algorithms for calculating the corresponding fracture models. Change in the type of the SSS near the crack contour when going from the bulk to the surface depends on the constraint of deformations along their front, i.e., on the 3D character of the SSS. Diagnostics of the form change of the defects (surface differently oriented semi-elliptic low-cycle cracks) is carried out on the basis of experimental results and numerical solutions. The data of the finite element modeling are implemented on the basis of macros of the ANSYS program complex. The regularity of the directionality of developing the elastoplastic fracture under low-cycle loading is studied. The proposed methodology is proved by the parametric equations of the kinetics of forming changes of the cracks under study in the fractographic analysis of the surfaces of their development. The results of testing samples with semi-elliptic cracks under low-cycle loading are used in analysis of the parameters of the morphology of the surfaces of the developed defects. The results of measuring fields of elastoplastic deformation intensity in the crack tip and geometrical characteristics of the fracture surface development are presented. Analysis of the dynamics of the local stress-strain state near the contour of multi-oriented defects in parts and structural units of the equipment showed a good agreement between the experimental parameters of the geometry of developing cracks and characteristics obtained by numerical methods. The presented parametric equations specify the characteristics of nonlinear fracture mechanics thus providing reliable estimation and forecasting of survivability, and safety of serviceability of the critical equipment. The deformation criteria of nonlinear fracture mechanics are used to demonstrate the dependence of fracture development on the 3D character of the stress-strain state indicating to the directionality of the geometric development of the fracture surface form.

The Method of Estimating the Durability of Structural Materials from the Effects of Cyclic Loads

2020 ◽  
Vol 992 ◽  
pp. 178-183
Author(s):  
E.A. Kuznetsov ◽  
O.E. Sysoev ◽  
Phone Htet Kyaw
Keyword(s):  
Strain State ◽  
Cyclic Creep ◽  
Structural Materials ◽  
Intensity Change ◽  
Stress Strain ◽  
Stress Strain State ◽  
Cycle Loading ◽  
Tooth Form ◽  
Minimum Intensity

The article deals with the technique of predicting the durability of structural materials under the influence of low-cycle loads at different loading trajectories in a two-dimensional stress space at a flat stress-strain state. The use of this technique significantly reduces the number of time-consuming and expensive experiments while maintaining the quality of the results. The technique is based on the method of processing acoustic emission signals when the acoustic signals are allocated with a fractal dimension of the attractor 1≤ D2att ≤6 on a steady-state cyclic creep that reflects the accumulation of hazardous defects in the structural material. To predict the durability at a certain type of stress-strain state, but at any form of a cycle of low-cycle loading by the proposed method, it is enough to have the results of experiments at the maximum intensity of stresses, the minimum intensity of stresses and the saw-tooth form of the cycle of stress intensity change.

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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