ISO 7438 pdf free download
ISO 7438-2020 pdf free download.Metallic materials – Bend test.
6.3 Bending device with a V-block
The tapered surfaces of the V-block shall form an angle of 1800_ a (see Figure 2). The angle a is specified in the relevant standard.
The edges of the V-block shall have a radius between 1 and 10 times the thickness o[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.
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ISO 7438:2020(E)
7.3 Width of the test piece
Unless otherwise specified in the relevant standard, the width of the test piece shall be as follows:
a) the same as the product width, if the latter is equal to or less than 20 mm;
b) when the width of a product is more than 20 mm:
1) (20 ± 5) mm for products of thickness less than 3 mm;
2) between 20 mm and 50 mm for products of thickness equal to or greater than 3 mm.
If it is agreed between the parties that plane strain conditions (plane strain definition is explained in Annex B) shall be maintained for test pieces greater than 3 mm thick, then the bend test shall be carried out in accordance with Annex B.
7.4 Thickness of the test piece
7.4.1 The thickness of test pieces from sheets, strips and sections shall be equal to the thickness of the product to be tested. If the thickness of the product is greater than 25 mm, it may be reduced by machining one surface to attain a thickness not less than 25 mm. During bending, the unmachined side shall be on the tension-side surface of the test piece.
7.4.2 Test pieces of round or polygonal cross-section shall have a cross-section equal to that of the product, if the diameter (for a round cross-section) or inscribed circle diameter (for a polygonal crosssection) does not exceed 30 mm. When the diameter or the inscribed circle diameter of the test piece exceeds 30 mm up to and including 50 mm, it may be reduced to not less than 25 mm. When the diameter or inscribed circle diameter exceeds 50 mm, it shall be reduced to not less than 25 mm (see Figure 4). During bending. the unmachined side shall be on the tension-side surface of the test piece.ISO 7438 pdf download.
