GB/T 2423 provides a composite test procedure, primarily intended for component type specimens, to determine, in an accelerated manner, the resistance of specimens to the deteriorative effects of high temperature/humidity and cold conditions.
2 Normative References
The following referenced documents are indispensable for the application 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.
IEC 60068-1 Environmental Testing—Part 1: General and Guidance
IEC 60068-2-30 Environmental Testing—Part 2-30: Tests—Test Db: Damp Heat, Cyclic (12 h+12 h Cycle)
IEC 60068-2-78 Environmental Testing—Part 2-78: Tests—Test Cab: Damp Heat, Steady State
3 General
3.1 Description of the Test
Test Z/AD is a cyclic temperature/humidity test which is designed to reveal defects in test specimens caused by "breathing" as distinct from the absorption of moisture.
This test differs from other cyclic damp heat tests in that it derives its increased severity from:
a) a greater number of temperature variations or "pumping" actions in a given time;
b) a greater cyclic temperature range;
c) a higher cyclic rate of change of temperature;
d) the inclusion of a number of excursions to sub-zero temperatures.
The accelerated breathing and the effect of the freezing of trapped water in cracks and fissures are the essential features of this composite test.
It is emphasized, however, that the freezing effect will occur only if the fissure dimensions are large enough to allow the penetration of a coherent mass of water as is normally the case in fissures between seals and metal assemblies, or between seals and wire terminations.
The degree of condensation will depend mainly upon the thermal time constant of the surface of the test specimens and may be negligible for very small specimens but copious for large specimens.
Similarly, the breathing effect will be more apparent on specimens which contain relatively large air-filled or gas-filled voids, but again, the severity of the test will depend to some extent on the thermal characteristics of the specimens.
