ISO 7438:2016 download free.Metallic materials – Bend test.
The edges of the V-block shall have a radius between ito 10 times the thickness of the test piece and shall be of sufficient hardness.
4.4 Bending device with a clamp
The device consists ala clamp and a former of sufficient hardness: It may be equipped with a lever for applying force to the test piece (see FIgure 3).
Liecause the position of the left Face of the clamp could 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.
5 Test piece
5.1 Gcncr.al
Round, square. rectangular, or polygonal cross-section test pieces shall he used in the test. Any areas of the material affected by shearing or flame cutting and similar operations during sampling of test pieces shall be removed. However, testing a test piece, the affected parts of which have not been removed, is acceptable, provided the result Is satisfactory.
5.2 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 (inclusive):
— 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 might adversely affect the test results. However, testing a test piece, the edges of which have not been rounded, Is acceptable, provided that the result i.s satisfactory.
5.3 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.
5.4 Thickness of the test piece
5.4.1 The thickness of Lest 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.
5.4.2 Test pieces of round or polygonal cross.sectkon shall have a crosssectlon equal to that of the product, If the diameter (for a round cross.sectlon) or Inscribed circle diameter (for a polygonal cross section) does not exceed 30 mm. When the diameter, or the inscribed circle diameter, of the test piece
5.5 Test pieces from Iorgings, castings and semi-finished products
In the case of Iorglngs, castings and seml.tlnlshed products, the dimensions of the test piece and sampling shall be as defined In the general delivery requirements, or by agreement.
5.6 Agreement for test pieces of greater thickness and width
By agreement, test pieces of a greater width and thickness than those specilied in 13 and 5A may be subjected to the bend test
5.7 Length of the test piece
The length of the test piece depends on the thickness of the test piece and the test equipment used.
6 Procedure
WARNING — During the test, adequate safety measures and guarding equipment shall be provided.
6.1 In general, tests are carned out at ambient temperature between 10 C and 35 C. Tests carried out under controlled conditions, where required, shall be made at a temperature of (23 * 5) C.
6.2 The bend test shall be carried out using one of the following methods as specilied in the relevant standard:
a) a specified angle of bend is achieved under an appropriate force and for the given conditions (see Figuresi.,2and3);
b) the legs of the test piece are parallel to each other at a specified distance apart while under an appropriate force (see FIgure 6)
c) the legs of the test piece are in direct contact while under an appropriate force (see Figure 7).
6.3 In the bend test to a specified angle of bend, the test piece shall be placed on the supports (se Figure 1) or on the lock(see Figure 2) and bent in by een supports force. The angle of bend, a, can be calculated from the measurement of the displacement of the former as given in Annexa.
the three methods (Figures 1, 2 and 3). the bending force shall be applied slowly so as to permit free plastic flow of the material.
In case of dispute, a testing rate of(1 0, 2)mm/s shall be used If it is not possible to bend the test piece directly to the specified angle in the manner described above, the bend shall be completed by pressing directly on the ends of the legs of the test piece [ see Figure 5) of a force to obtain parallelism of the legs. The test may be carried out with or without an insert. The thickness of the insert shall be as defined in the relevant standard or by agreement. An alternate method of test is that of bending over a former (see 4.4).
6.4 If specified, the test piece, after its preliminary bending, shall be further bent between the parallel plates of the press, by application of a force, to obtain direct contact between the legs of the test piece (see Figure 7).
7 Interpretation of results
7.1 The interpretation of the bend test shall be carried out according to the requirements of the product standard. When these requirements are not specified, absence of cracks visible without the use of magnifying aids Is considered as evidence that the test piece withstood the bend test.
7.2 The angle of bend, specified in product standards, is always considered as a minimum. If the internal radius of a bend is specified. it is considered as a maximum.
B Test report
The test report shall include the following information:
a) a reference to this International Standard, I.e. ISO 7438;
b) identification olthe test piece (type of material, cast number, direction of the test piece axis rebtive to a product, etc.);
c) shape and dimensions of the test piece;
d) test method;
e) any deviation from this International Standard;
f) test result.