The Sheet Billet Stress-Strain State Modeling at the Elastic-Plastic Bending and Curvature Evaluation While Its Elastic Unloading

Aeronautical and Space-Rocket Engineering


Аuthors

Feoktistov S. I.1*, Mar’in S. B.1**, Lozovsky I. V.2***, Kravchenko A. K.1****

1. Komsomolsk-on-Amur State University (KnASU), 27, Lenin str., Komsomolsk-on-Amur, 681013, Russia
2. Komsomolsk-na-Amure State University, 27, Lenina str., Komsomolsk-on-Amur, 681013, Russia

*e-mail: serg_feo@mail.ru
**e-mail: maryinsb@mail.ru
***e-mail: Lozovcky@yandex.ru
****e-mail: ek74@list.ru

Abstract

The processes of the sheet blanks curtailing in an elasto-loose medium to obtain single-seam thin-walled tubular blanks of non-standard cross section for the aircraft hydro-gas systems is of great interest while aircraft hydro-gas systems elements manufacturing. When solving technological problems, one of the urgent problems consists in geometry determining of the deforming rigging with regard to the blank springing-back and obtaining the part of the required shape. To solve this problem, it is necessary to determine the blank stress-strain state while bending, which will allow determining the final geometry of the part after the load removing.
When analyzing the deformed state of a sheet blank while bending with radial compression, the flat section hypothesis was used, according to which the original flat sections of the blank are being sustained flat during deformation. Based on this hypothesis, the law of relative tangential deformations distribution along the height of the billet section was determined.
Equations that link main deformations with the main stresses in the cylindrical coordinate system were obtained by the hypotheses of the deformation theory of plasticity.
The article presents the relationship between relative displacement of the neutral layer and radial compression value at different internal bending radii. It was found on their basis that the value of the neutral layer displacement increased and varies proportionally with the increase of the radial compression value. Moreover, the bigger the bending radius the greater the relative displacement, which can reach significant values.
The authors considered the bending moment variation dependence on the radial compression value, on which basis an inference may be drawn that the value of the blank sprinback decreased with the radial compression value increase.
Thus, the equations, allowing determine the stress-strain state of the blank at bending by the moment with radial compression, were obtained.
 The empirical equation, which allows unambiguously link the bending moment, acting at the bending with radial compression and the curvature change of the neutral layer at the elastic unloading. This allowed dedermining the residual curvature of the blank. The dependence of error of the unloading bending moment determining herewith on the radial compression value at various internal radii was hundredth of a percent independently from the radial compression forcing. This error at that tends to zero with the radius increase.
Thus, it can be concluded that the deformation (bending) of the blank is caused by creating a bending moment under the impact of the deformation force on the tooling. An extra compressive load is being created herewith from the side of the tooling. When the blank is compressed, extra normal stresses arise, which change the position of the neutral layer of normal bending stresses, changing thereby the overall picture of the stress-strain state. The distributed compressive load is being regarded constant along the bending length. This can be achieved with elastic or elasto-loose tooling.
To simulate the stress-strain state during elastic-plastic bending of the sheet blank and evaluate the curvature during its elastic unloading, a program, fixed by a certificate of State registration, was elaborated. The program is intended for determining the blank radius and normal bending stresses distribution after the deformation force removing.

Keywords:

The Sheet Billet Stress-Strain State Modeling at the Elastic-Plastic Bending and Curvature Evaluation While Its Elastic Unloading

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