This part of IEC 60068 demonstrates the adequacy of specimens to resist dynamic loads without unacceptable degradation of its functional and/or structural integrity when subjected to the specified vibration test requirements as defined by a time history (Long Time History Replication). These can either be recorded in measurement exercises or generated artificially. In both cases, this method allows for generating a test tailored to very specific application. Typical applications are tests in which very specific deterministic transient, periodical or random excitation is necessary and the characteristics of the motion are not covered by other test standards. This includes time histories not sufficiently represented by the standard shock tests of IEC 60068-2-27 or a general description by a shock response spectrum as in IEC 60068-2-81; periodical vibration that is not covered by a sinusoidal waveform as in IEC 60068-2-6; random vibration that is not covered by the description of Gaussian broad-band random vibration of IEC 60068-2-64. However, the user shall be aware that long time history replication uses a deterministic time history. Simulation of random vibration of any kind is approximated by quasi-random. In addition, additional mixed mode tests are possible with this test method by generating time histories that are representations of the required test signals. This includes tests of high complexity. The purpose of this test is different from IEC 60068-2-57. The purpose of IEC 60068-2-57 is an evaluation for a transient vibration using mainly a synthesized time history. A long time history test is mainly used for a durability and functionality test using an actual time history measured in a real field environment. It may also be used as a method to apply a simulated non-gaussian time history.
Long time history replication vibration may be used to identify accumulated stress effects and the resulting mechanical weakness and degradation in the specified performance. This information, in conjunction with the relevant specification, may be used to assess the acceptability of specimens. This standard is applicable to specimens which may be subjected to vibration of a very specific nature resulting from transportation or operational environments, for example in aircraft, space vehicles and land vehicles. It is primarily intended for unpackaged specimens, and for items in their transportation container when the latter may be considered as part of the specimen itself. However, if the item is packaged, then the item itself is referred to as a product and the item and its packaging together are referred to as a test specimen. This standard may be used in conjunction with IEC 60068-2-47:2005, for testing packaged products. If the specimens are subjected to vibration of a deterministic transient or periodic nature resulting from transportation or real life environments that are covered by other test methods, these shall generally be preferred. See IEC 60068-3-8:2003 for estimating the dynamic vibration environment of the specimen and based on that, selecting the appropriate test method
Antal sider: 30
EN IEC 60068-2-85:2019 IDTIEC 60068-2-85:2019 IDT