This standard is a part of the series of test methods for bare wires, specifically designed for the unidirectional bending performance testing of bare wires (such as copper, aluminum, and their alloy wires). It specifies the use of a specialized bending test apparatus to bend the sample 90 or 180 degrees around a cylindrical mandrel of a specified diameter, and then inspect the surface for cracks or other defects to evaluate the material's ductility and processing quality. The standard details the specifications of the test apparatus (such as the cylindrical mandrel and clamping tools), sample preparation, specific test procedures, and criteria for result evaluation. When implementing this standard, it must be used in conjunction with the first part of the series, "General Principles." This test is primarily used to assess the ability of wires to withstand bending deformation during subsequent processing or use.