GB 4909.4-1985 Test methods for bare wires Torsion test

This test method is applicable to the determination of the torsion characteristics of solid copper, aluminum and their alloy conductors with a nominal size of not less than 0.5 mm. This test is to twist the test piece of specified length around its own axis until it breaks or reaches the specified number of twists. GB 4909.4-1985 Bare wire test method Torsion test GB4909.4-1985 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test methods for bare wires
Torsion test
The provisions of this standard are consistent with those of international standards ISO2627 (1973) and R957 (1969). 1 Scope of application
UDC621.315.14
GB 4909.4--$5
1.1 This test method is applicable to the determination of the torsion characteristics of solid copper, aluminum and their alloy conductors with a nominal size of not less than 0.5mm. 1.2 This test is to twist the test piece of specified length around its own axis until it breaks or reaches the specified number of twists.
2 Test equipment
The torsion testing machine shall meet the following requirements:
Figure 1 Schematic diagram of torsion testing machine
1 Positioning chuck, 2-rotating chuck, 3-test piece, d-nominal diameter of test piece, nominal size of narrow side of test piece, L-gauge length, F-negative joint 2.1 Clamp,
2.1.1 The hardness of the clamp shall not be less than HRC61, the chuck shall be kept on an axis and coincide with the torsion axis of the test piece. 2.1.2 The speed of the rotating spark head shall be adjustable, and the speed shall be uniform and stable. 2.1.3 The positioning chuck can move axially to adjust the distance between the two chucks, and no angle of deflection will be generated when the rotating chuck rotates. A certain load can be applied to the positioning chuck to keep the torsion test piece in a straight state at all times. 2.2 The number of torsion times can be automatically recorded.
3 Specimen preparation
3.1 Sampling Take 5 specimens from the - end of the specimen that has passed the appearance inspection. The length of the specimen is the original gauge length plus twice the clamping length. 3.2 Straightening The specimen is carefully straightened by hand. If necessary, it is allowed to place the specimen on a mat and gently tap it straight with a hammer. 3.3 The original gauge length is 100d, and the maximum is not more than 500mm. National Bureau of Standards 198501-31 Issued
1985-12-01 Implementation
4 Test Procedure
GB 4809.4-85
4.1 According to the size of the specimen, determine the original gauge length of the specimen, and adjust the positioning chuck so that the distance between the two chucks is equal to the original gauge length.
4.2 Hang a weight on the positioning chuck so that the specimen can be straightened. At this time, the tensile force on the specimen should not be greater than 2% of the tensile strength of the specimen. 4.3 Install the specimen, make sure that the axis of the specimen coincides with the axis of the fixture, and then clamp the fixture. 4. Start the testing machine and twist the specimen at the speed specified below. The speed should be uniform and stable, and pay attention to prevent the heat generated by the specimen from affecting the test results.
When the specimen size is <3mm, <60 times/min
When >3mm, <30 times/min
It is allowed to twist the specimen manually.
Every rotation of the specimen by 360° is a twist. www.bzxz.net
The test is carried out until the specified number of twists (N) or complete fracture. 4.5: The twisting method can be unidirectional twisting, forward and reverse twisting, or two specimens placed side by side twisting in the same direction at the same time ("double twisting"), which should be specified in the product standard. 5 Test results and calculations
5.1 The test results shall comply with the provisions of the product standard. 5.2 The test record shall indicate: the size of the test piece, the gauge length, the applied load, the torsion speed, and if an appearance inspection is performed, it shall also be stated.
5.2.1 The uniformity of the torsion crease pitch over the entire length of the test piece. 5.2.2 The fracture shape and defects of the test piece, flat, stepped, oblique, fan-shaped, with cracks, with shrinkage holes, etc. 5.2.4 The crack layer of the test piece: cracks or burrs that destroy the continuity of the metal appear along the torsion crease of the test piece. 5.3 When the number of torsion reaches the specified value, the test is considered valid regardless of the position of the fracture. If the fracture is in the jaws of the chuck or the distance from the jaws is less than 2d, and the number of torsion does not reach the specified value, another sample should be taken and retested. Additional remarks:
This standard is proposed by the Ministry of Machinery Industry of the People's Republic of China. This standard is under the jurisdiction of the Shanghai Cable Research Institute of the Ministry of Machinery Industry. This standard was drafted by Shanghai Cable Research Institute of the Ministry of Machinery Industry, etc. The drafting persons in charge of this standard are Wu Musheng and Shen Jianhua.
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.