This part of GB/T 4909 specifies the test equipment, sample preparation, measurement procedures, test results and evaluation of the bare wire bending test. This part is applicable to the determination of the unidirectional bending performance of circular and rectangular cross-section conductors such as copper, aluminum and its alloys, and bimetallic wires with a nominal diameter d of 0.300 mm to 10.00 mm. This part is to bend the test piece into a certain angle along the specified bending radius, and observe the tension surface of the test piece after bending. This section should be used together with GB/T 4909.1-2009.