GB/T 4074.3-2024 Test methods of winding wires - Part 3: Mechanical properties
1 Scope
This document specifies the following test methods for winding wires:
——Test 6: Elongation;
——Test 7: Springiness;
——Test 8: Flexibility and adherence;
——Test 11 : Resistance to abrasion;
——Test 18: Heat bonding.
For definitions, general notes on test methods and the complete series of test methods for
winding wires, IEC 60851-1 applies. This document also provides recommended friction test methods in Annex B.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 4074.2-2024 Test methods of winding wires - Part 2: Determination of dimensions (IEC 60851-2:2019, IDT)
Note: There is no technical difference between the cited contents of GB/T 4074.2-2024 and the cited contents of IEC 60851-2:1996.
ISO 178:2019 Plastics - Determination of flexural properties
3 Terms and definitions
No terms and definitions are listed in this document.
4 Test 6: Elongation
4.1 Elongation at fracture
Elongation is the increase in length expressed as a percentage of the original length.
A straight piece of wire shall be elongated to the point of fracture of the conductor at a rate of (5 ± 1) mm/s with an elongation tester or with tensile testing equipment with a free measuring length of between 200 mm and 250 mm. The linear increase at fracture shall be calculated as a percentage of the free measuring length.
Three specimens shall be tested. The three single values shall be reported. The mean value represents elongation at fracture.
4.2 Tensile strength
Tensile strength is the ratio of the force at fracture to initial cross-section.
A straight piece of wire shall be elongated to the point of fracture of the conductor at a rate of (5 ± 1) mm/s with tensile testing equipment with a free measuring length of between 200 mm and 250 mm and which records the force at fracture.
Three specimens shall be tested. The initial cross-section and the three single values of the force at fracture shall be reported. The mean value of the ratio of the force at fracture and the initial cross-section represents the tensile strength.
5 Test 7: Springiness
5.1 General
Springiness is the recoil measured in degrees after the wire is wound in the form of a helical coil or bent through an angle.
5.2 Round wire with a nominal conductor diameter from 0.080 mm up to and including 1.600 mm
5.2.1 Principle
A straight piece of wire is wound five times around a mandrel with a diameter and under a
tension applied to the wire as specified in the relevant standard. The reading of the angle by which the end of the five turns recoils is the measure of springiness.
5.2.2 Equipment
Figure 1 shows an example of the test equipment with details of the mandrel given in Figure 2 and Table 1. Figure 2 indicates a helical groove, which may be used to facilitate winding. The provision of this groove, however, is not mandatory. The dial is marked with 72 equally spaced divisions so that with five turns of the wire the reading corresponds to the number of degrees that each turn springs back.
5.2.3 Procedure
The specified mandrel shall be mounted and locked in position with its axis horizontal and with the slot or hole for fastening the wire corresponding with the zero of the dial. The mandrel shall be dusted with powdered talc (French chalk) to prevent the wire clinging to the mandrel.
A tension shall be applied to a straight piece of wire of about 1 m in length by attaching the
specified load to one end of the wire. The handle to rotate the mandrel shall be unlatched. The other end of the wire shall be inserted into the slot or hole so that sufficient wire projects on the other side of the mandrel and the wire is in firm contact with the mandrel. The weight shall be slowly lowered with the wire suspended vertically below the mandrel and with the dial zero and the slot or hole pointing downwards.
With the free end of the wire being held securely, the mandrel shall be rotated for five complete turns counterclockwise (looking at the face of the dial) and further until the zero on the dial is vertically upwards. The handle shall then be latched in this position. The load shall be removed while the wire is held in position, and the wire shall then be cut about 25 mm beyond the end of the fifth turn. This end of the wire shall be bent into a vertical position in line with the dial zero to act as a pointer.
A pencil or similar tool shall be placed to the left of this end of the wire to prevent any sudden springback. The coil shall then be allowed to unwind slowly and without jerking.
Note: If the wire springs back suddenly, it is possible to obtain erroneous results.
The mandrel and the dial shall then be unlatched and rotated clockwise to bring the pointer back into a vertical position. The springback angle is equal to the reading on the dial in line with the pointer. With very springy wires, the pointer may recoil more than one complete revolution. If this is the case, 72 shall be added to the dial reading for each complete revolution of recoil.
Three specimens shall be tested. The three single values shall be reported. The mean value represents springiness.
