- Annealing Test Definition: The annealing test is performed to ensure the durability and flexibility of wires and conductors during twisting and bending.
- Specimen Preparation: A specific gauge length of the conductor is used for the test, ensuring accurate results.
- Testing Equipment: A tensile testing machine, micrometer, and measuring scale are essential for conducting the annealing test.
- Elongation Measurement: The test measures the elongation percentage of the specimen after it fractures.
- Result Reporting: The results indicate if the specimen meets the specified elongation requirements.
The annealing test measures elongation at break of annealed copper wires, aluminium welding-cable wires and solid conductors of electric power cables. A current-carrying core of a power cable is twisted and bent during laying, so the metal must stretch without cracking. IS 10810-1 pulls a marked length to fracture and IS 8130 requires that elongation to be at least the tabulated minimum for those wires and conductors.
Process of annealing test for wires and conductors
Take one conductor specimen. IS 10810-1 uses a 250 mm gauge length plus extra at each end for the grips. Straighten the piece by hand if needed and mark the gauge length lightly.
Use a tensile machine that can hold the specimen firmly. A plane-faced micrometer reading to 0.01 mm and a scale reading to 1 mm are enough for diameter and length. IS 10810-1 calls for one specimen and no special pre-conditioning. Grip the wire and separate the heads gradually until it breaks. The usual reading of that method is that the rate of separation shall not be greater than 100 mm per minute.
Fit the broken ends together and measure the gauge length again. Report elongation as a percentage of the original gauge length. The annealing test for wires and conductors passes only when that percentage is at least the IS 8130 minimum for the diameter or the solidal size, not a maximum. Measure the specimen diameter with a plane-faced micrometer reading to 0.01 mm.
If L is the original gauge length and L’ is the length after the broken ends are fitted together, L’ is the sum of the two parts. The percentage elongation is:
Tabulation of Observations of Annealing Test
| Diameter of Circular Wire in mm | Size of Shaped Solidal Conductor in mm2 | Original Gauge Length, L in mm | Length After Fracture, L’ in mm | Elongation (L’ – L) in mm |
| – | – | – | – | – |
| – | – | – | – | – |
Calculation
Where L = original gauge length of the specimen
and L’ = length after the broken ends are fitted together
Report
| Sample No | Diameter of Circular Wire | Size of Shaped Solidal Conductor | Elongation, percent | |
| Observed | Specified | |||
| – | – | – | – | – |
Conclusion :
Specimen meets or does not meet the specified minimum elongation.
