ISO 7438-2020 pdf free.Metallic materials- Bend test.
This document specifies a method for determining the ability of metallic materials to undergo plastic deformation in bending.
This document applies to test pieces taken from metallic products, as specified in the relevant product standard. It is not applicable to certain materials or products, for example tubes in full section or welded joints, for which other standards exist.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at
— ISO Online browsing platform: available at
4 Symbols, designations and units
Symbols and designations used in the bend test are shown in Figures 1 and 2 and specified in Table 1.
5 Principle
The bend test consists of submitting a test piece of round, square, rectangular or polygonal cross- section to plastic deformation by bending, without changing the direction of loading, until a specified angle of bend is reached.
The axes of two legs of the test piece remain in a plane perpendicular to the axis of bending. In the case of a 1800 bend, the two lateral surfaces may, depending on the requirements of the product standard, lie flat against each other or can he parallel at a specified distance, an insert being used to control this distance.
6 Test equipment
6.1 General
The bend test shall be carried out in testing machines or presses equipped with the following devices:
a) bending device with two supports and a former as shown in Figure 1
b) bending device with a V-block and a former as shown in Figure 2
c) bending device with a clamp as shown in Figure 3.
6.2 Bending device with supports and a former
6.2.1 The length of the supports and the width of the former shall be greater than the width or diameter of the test piece. The diameter of the former is determined by the product standard (see Figure 1]. The test piece supports and the former shall be of sufficient hardness.
6.2.2 Unless otherwise specified, the distance between the supports, 1, shall be as given in Formula (1), and shall not change during the bend test.
6.3 Bending device with a V-block
The tapered surfaces of the V-block shall form an angle of 180° — a (see Figure 2). The angle a is specified in the relevant standard.
The edges of the V-block shall have a radius between I and 10 times the thickness of the test piece and shall be of sufficient hardness.
6.4 Bending device with a clamp
The device consists of a clamp and a former of sufficient hardness. It may be equipped with a lever for applying force to the test piece (see Figure 3).
Because the position of the left face of the clamp can influence the test results, the left face of the clamp (as shown in Figure 3) should not reach up to or beyond the vertical line through the centre of the circular former shape.
7 Test piece
7.1 General
Round, square, rectangular or polygonal cross-section test pieces shall be used in the test. Any areas of the material affected by shearing or flame cutting and similar operations during the sampling of test pieces shall be removed. However, testing a test piece, the affected parts of which have not been removed, is acceptable, provided that the result is satisfactory.
7.2 Edges of rectangular test pieces
The edges of rectangular test pieces shall be rounded to a radius not exceeding the following values:
— 3 mm, when the thickness of the test pieces is 50 mm or greater;
— 1,5 mm, when the thickness of the test pieces is less than 50 mm and more than or equal to 10 mm;
— 1 mm when the thickness is less than 10 mm.
The rounding shall be made so that no transverse burrs, scratches or marks are formed which can adversely affect the test results. However, testing a test piece, the edges of which have not been rounded, is acceptable, provided that the result is satisfactory.ISO 7438 pdf free download.