RU2475321C2 - Method of section blank bending - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metal forming, particularly, to defining parameters of bending sections, e.g. rolled stock, welded beams. Bending and contracting forces are applied to section wall. In allowing for section wall axial contraction, relative bending force and resilience curvature are decreased to three times compared with simple flexure. In applying bending force to section flange displacing neutral stress and strain axis from section flange, relative bending force and resilience curvature are increased to 2.5 times compared with simple flexure without allowance fro contact strains. In applying bending force to section flange displacing neutral stress and strain axis toward section flange, relative bending force and resilience curvature are increased by 15% compared with simple flexure without allowance fro contact strains.

EFFECT: higher quality of bending.

1 dwg

Description

The invention relates to the processing of metals by pressure, namely, to determine the parameters of bending profiles in the form of rolled products, welded beams and extruded panels.

The value of the criteria for the boundary conditions is usually determined based on the geometry and mechanical properties of the bent profile or panel, but they do not take into account the variously applied schemes of deformation and the application of force to the elements of the profiles (shelf and wall), which significantly change the basic parameters of bending.

A known method of bending profiles takes into account the constraining forces exerted on the wall of the profile (AS USSR No. 662200), which can be used as the closest analogue.

The specified method relates mainly to sheet blanks, the formation of which an important factor is the thinning of the blank after bending. When bending profiles, thinning of the workpiece compared to its dimensions is negligible and in this case the boundary conditions of deformation should be determined from other conditions compared to the so-called pure bending.

The objective of the present invention is to determine the boundary conditions when bending profiles used as stiffeners in the designs of various products.

The technical result, which is provided by the invention and due to which this problem is solved, is to expand the areas of use of analytical methods for determining the boundary conditions of deformation, suitable not only for sheet blanks, but also for blanks from profiles and panels. In addition, compared with the known bending methods, the proposed method can be used for bending profiles and welded T-beams both with the wall inward and the wall outward, which also expands the scope of this method. In this case, the technical result consists in determining criteria for the boundary conditions of deformation, based on the methods (schemes) of applying deforming forces to profile elements (wall and shelf), which were previously practically not taken into account when determining bending parameters. The proposed solution became possible after the authors' research in their dissertations, as well as fundamental and applied research conducted in recent years as part of targeted federal programs.

The specified technical result is achieved due to the fact that when bending the blanks of the profiles, bending forces and constraining forces are applied to the wall of the profile, while bending forces are applied to the wall or to the shelf, or to the wall and shelf of the profile.

Given the tightness of the profile wall in the axial direction, the relative bending force and spring curvature are reduced to 3 times compared to pure bending.

When a bending force is applied to the profile wall, which biases the neutral axis of stresses and strains in the direction from the profile shelf, the relative bending force and spring curvature are increased up to 2.5 times compared to pure bending without taking into account the effect of contact stresses.

When a bending force is applied to the profile flange, which biases the neutral axis of stresses towards the profile flange, the relative bending force and spring curvature are increased to 15% compared to pure bending.

The method of bending blanks from profiles with various bending forces is illustrated by schemes for their deformation with tightness of the wall. Figure 1: a - to the wall, b - to the shelf, c - to the wall and shelf.

A profile in the form of a rolled asymmetrical half-bulb 6 of height h, wall thickness b _C and the dimensions of the bulb (shelf) b _p × t is subjected to a bending force k _s σ _t , where σ _t is the yield strength of the profile material, ak _c is the coefficient of excess of elastic bending. The profile wall is loaded with a constraining force also in fractions of the yield strength k _st σ _t (Fig. 1a), while the diagrams of the effective and residual stresses are shown to the right of the bending diagram: 1 - σ for pure bending without taking into account the action of contact stresses; 2 - σ _{x is the} approximate value of normal stresses in the cross section of the profile along the x axis along the profile; 2 '- σ _x the same as in position 2, but adjusted from the account of the contact stress action scheme; 3 - σ _y - normal stresses along the y axis along its height h; 4 - σ _z - normal stresses across the profile along the z axis; 5 - σ _ost - residual stresses along the x axis. On figb - the same designation as on figa, but for the scheme of application of the bending force k _p σ _t to the profile shelf. On figv - the same, but for the scheme of application of bending forces to the profile on the wall and on the shelf k _p σ _t

As follows from the above illustrations, the tightness of the profile wall and the inclusion of load application circuits significantly changes the nature and magnitude of stresses and strains in the bent profile. In this case, the tightness of the profile wall in the axial direction shifts the neutral axis of stresses away from the profile shelf (Fig. 1a) and thereby reduces the relative bending force and spring curvature up to 3 times. The application and accounting of bending forces on the profile flange (Fig.1b) shifts the neutral axis of deformation in the direction from the profile flange, and the relative bending force and spring curvature are increased up to 2.5 times compared to pure bending (see Ox according to claim 1 on Fig.1b). The application of bending forces to the profile shelf shifts the neutral axis of stresses (Fig. 1c) towards the profile shelf, and the relative bending force and spring curvature increase up to 15% compared to pure bending (diagram 1). The relative bending moment is a general indicator for determining the parameters of the bend and is determined by the integral of the normal stresses arising during bending (the diagram σ _x in Fig. 1a, b, c). The value of the relative bending moment can be taken from the table in the brochure: Kuklin OS "Means of technological equipment of case-processing workshops" Part 1. L .: TsNII "Rumb", 1985, p.116.

The proposed method allows to determine the boundary conditions of bending of billets from profiles and panels, which ensures the operational reliability of products with a minimum of heat treatment, due to a more accurate account of the resulting stresses and deformations.

Based on the foregoing, it can be seen that the proposed method has significant advantages over the prototype, as it is more versatile and less laborious to perform the necessary experimental work to establish the boundary conditions for the bending of workpieces from profiles and panels.

Claims (1)

A method of bending blanks of profiles, characterized by the application of constraining forces on the wall of the blank of the profile with the application of bending forces to the wall, or to the shelf, or to the wall and shelf of the profile.