The steel bending test procedure is carried out with test pieces with rectangular, circular or polygonal sections, unchanged on the length of the sample.
Steel bending test is carried out according to ISO 7438 -2005 standard, used to determine the plastic deformation ability of metal materials by bending test method. This standard applies to samples taken from a part of the product, not to products or materials such as: raw (un-cut) pipes, welded tubes, thin sheets, … These tubes are used Use individual standards.
Note when selecting a sample:
– Sample shape and size depends on the material:
- If the material is steel plate, shaped steel, belt steel has a width equal to or greater than 100mm (rectangular cross-section), the thickness of the test piece is equal to the thickness of the material, the width of the test piece is about 25 -50 mm. , with an error of ± 5mm
- If the material is a steel belt with a width less than 100mm, a steel bar (circle, square), the cross-section of the test piece is the cross-section of the material, the length of the test piece is based on the size of the bending bearings.
- If the steel and rolled steel plates have a thickness greater than 25 mm, the thickness of the test piece is 25mm. When cutting, only one-sided machining, the other side is not machined is the face of the sample when tested, width 25 -50 mm.
- In case of ingot steel (circular cross-section) with a diameter not exceeding 50mm, if the object has a larger size than the above, it is necessary to make it easier to have a diameter of 25-50mm.
- For semi-finished or forged samples, if there is no specific regulation, the specimen thickness shall be 20mm, error of ± 5mm.
You can use any method to get the material for the test sample, but make sure that 1/3 of the length of the test piece in the middle is not allowed to touch, punch, and hammer indentation. If the curvature of the specimen is straightened at normal temperature, the force exerted on it should be static.
Steel bending test method is divided into 3 types:– The bending angle reaches the specified angle ∝
– Bend until the two edges of the sample are parallel
– Bending until the two edges of the sample touch each other
Based on the technical requirements of the product, choose one of the above methods.
The flex test specimen is placed on 2 supports, thanks to the middle bending pillow, the specimen is bent in the middle. The distance between the support pillow and the diameter of the bending pillow is specified according to specific technical conditions. The width of the support and the bending pillow must be greater than the width of the test piece.
Allows bending on V-shaped grooves with the angle of the groove plane is 60 ° ± 10º, the width of the groove is not less than 125mm. The width of the groove needs to be greater than the width of the sample.
If, when bending the knees or on the bending angle has not reached the specified angle, it is possible to bend directly on the two ends of the test piece. If you want the radius of the corner to reach a certain position, you can use a cushion between the two edges of the sample.
If the specimen needs to be bent until two edges touch each other, there is no need to use the middle pad, but continue to bend until the two sides touch each other.
Results after testing
After the bending angle has reached the specified angle, carry out the inspection on the outside (tensile side). If there is no cracking or flaking, the test sample is satisfactory. If the sample is cracked before reaching the specified angle, the sample does not meet the requirements and the crimp angle of the cracked specimen should be recorded.
Bending test is carried out on universal compression tractor series, material strength testing machine.
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