Bending test is a test to determine the mechanical properties of seamless pipes and welded pipes under bending load, and it is one of the basic methods for testing the mechanical properties of seamless pipe machines and welded pipes. Bend tests can also be used to check the surface quality of materials. The bending test is carried out on a universal material machine, and there are two loading methods: three-point bending and four-point bending. The cross-section of the sample is circular or rectangular, and the span during the test is generally 10 times the diameter.
For brittle materials, the bending test generally only produces a small amount of plastic deformation to break, while for plastic materials, the bending fracture strength cannot be measured, but its ductility and uniformity can be tested. The bending test of plastic material is called cold bending test. During the test, load the sample to bend it to a certain extent, and observe whether there are cracks on the surface of the sample.
Experimental principle
A full-section metal straight pipe is bent around a specified radius and grooved center until the bending angle reaches the value specified in the relevant product standard.
Test equipment
1. The bending sample equipment should be carried out on the bending test machine, and the testing machine should be able to prevent the elliptical deformation of the cross section of the pipe during the test.
2. The bending center of the pipe bend testing machine should have a groove suitable for the outer contour of the pipe. The radius of the bending center is specified by the relevant product standard.
Note: The deviation of the radius of the bending center, the depth of the groove and the roundness all have an effect on the experimental results.
3. The bending radius is six times the outer diameter of the steel pipe, the bending angle is 90 degrees, and no cracks should appear after the test weld.
Test procedure
1. Take a part of the steel pipe for sample, and can carry out the experiment on the pipe bending machine.
2. The test should generally be carried out in the room temperature range of 10℃-35℃. For tests requiring controlled conditions, the test temperature shall be 23°±5°C.
3. Bend the pipe sample without filler through the pipe bending test machine. During the test, ensure that the bending deformation section of the sample is in close contact with the metal pipe bend until the specified bending angle is reached.
4. When performing the bending test of the welded pipe, the welding seam is located on the outer side of the bending direction, and is at a position of 90°|| ("|" is the neutral line of bending) with the yoke plane.
5. The description of the results of bending test specimens shall be in accordance with the requirements of the relevant product standards. When not specified in the product standard, without the use of a magnifying glass, if there are no visible cracks and cracks at the back weld of the specimen, it shall be rated as qualified.
For brittle materials, the bending test generally only produces a small amount of plastic deformation to break, while for plastic materials, the bending fracture strength cannot be measured, but its ductility and uniformity can be tested. The bending test of plastic material is called cold bending test. During the test, load the sample to bend it to a certain extent, and observe whether there are cracks on the surface of the sample.
Experimental principle
A full-section metal straight pipe is bent around a specified radius and grooved center until the bending angle reaches the value specified in the relevant product standard.
Test equipment
1. The bending sample equipment should be carried out on the bending test machine, and the testing machine should be able to prevent the elliptical deformation of the cross section of the pipe during the test.
2. The bending center of the pipe bend testing machine should have a groove suitable for the outer contour of the pipe. The radius of the bending center is specified by the relevant product standard.
Note: The deviation of the radius of the bending center, the depth of the groove and the roundness all have an effect on the experimental results.
3. The bending radius is six times the outer diameter of the steel pipe, the bending angle is 90 degrees, and no cracks should appear after the test weld.
Test procedure
1. Take a part of the steel pipe for sample, and can carry out the experiment on the pipe bending machine.
2. The test should generally be carried out in the room temperature range of 10℃-35℃. For tests requiring controlled conditions, the test temperature shall be 23°±5°C.
3. Bend the pipe sample without filler through the pipe bending test machine. During the test, ensure that the bending deformation section of the sample is in close contact with the metal pipe bend until the specified bending angle is reached.
4. When performing the bending test of the welded pipe, the welding seam is located on the outer side of the bending direction, and is at a position of 90°|| ("|" is the neutral line of bending) with the yoke plane.
5. The description of the results of bending test specimens shall be in accordance with the requirements of the relevant product standards. When not specified in the product standard, without the use of a magnifying glass, if there are no visible cracks and cracks at the back weld of the specimen, it shall be rated as qualified.
Previous：JCOE pipe forming process
