Theoretical investigation of the stress state and calculation of residual stresses during bending of the profiles with open sections
DOI:
https://doi.org/10.37142/2076-2151/2019-2(49)61Keywords:
bending; stresses; strains; residual stresses; cold-formed shapes; hardening; sheet blanks; spring-back.Abstract
Kukhar V. V., Nahnibeda M. M. Theoretical investigation of the stress state and calculation of residual stresses during bending of the profiles with open sections // Material working by pressure. – 2019. – № 2 (49). - P. 61-70.
The character of the stress-strain state of sheet blanks bended by different ways is considered in the paper. The review of research methods of residual stresses and deformations and determination of the spring-back at bending of sheet blanks is carried out. The nature of the formation of a heterogeneous stressed state on the external and internal radius of bended workpiece is shown. The theoretical consideration of bending process for profiles with determination of residual stresses is presented. Development of the mathematical model of the stress-strain state of the sheet blank during bending operations and the calculation of residual stresses in the material at bending of profiles with an open cross-section. The basis of the research is grounded on mathematical models derived on the mechanics of continuous method, a technique for determining of the stress and strain state according to the geometric dimensions of the workpiece, data from the approximation of the stress-strain curves of various materials hardening, including obtained from the results of own research. As a result of the performed analysis of the studies of bending processes, has been established that the receiving and delivery characteristics of the bending profiles essentially depend on the properties of their material, shape of the die-calibers. The methods of theoretical studies of the stress-strain state of the workpiece at bending are developed. The expediency of using of methods of direct measurements of geometrical blanks sizes after bending on different angles with regard to thickness and width of the blank is shown. It is substantiated that for take into account the spring-back at the multistage bending is necessary to calculate the residual stresses on the preformed workpiece. As a result of the research of the bending process of the shapes at the roll-forming dies have been established the characteristics of the stress and strain fields, which depend on the material of the blank, the die-tool shape configuration and the number of stage.
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