BS EN IEC 60068-2-86:2024 - Page 2

Environmental testing. Tests. Test Fx: Vibration. Multi-exciter and multi-axis method | Status: Current

1 Scope This document provides a test procedure for use with multi-exciter and multi-axis vibration test systems. The vibration test is intended for general application to components, equipment, and other products, hereinafter referred to as "specimens", subjected to dynamic environments that could arise during an equipment life cycle. Although this document is mainly intended for vibration testing, the procedure is also applied to certain types of shock and transient tests. The test procedure set out in this document is applicable where a specimen is required to demonstrate its adequacy to resist specified vibration, shock and transient conditions, without unacceptable degradation of functional or structural performance. The test procedure has significant similarity to test procedures of other IEC 60068‑2 documents and encompasses the same range of vibration and shock excitation types. This document is applicable to specimens subjected to vibration, shock and transient conditions resulting from transportation and/or operational environments, for example in aircraft, space vehicles and land vehicles. It is primarily intended for unpackaged specimens. It is applicable to specimens in their transportation container when the latter are considered as part of the specimen itself. The test method and associated techniques addressed within this document are primarily intended for use with multiple electrodynamic or servo-hydraulic vibration generators along with an associated computer-based digital control system to control of the specimen excitations. This document encompasses two testing approaches, commonly referred to as multi-exciter single-axis (MESA), and multi-exciter multi-axis (MEMA). These are:

1. a) Utilising fixed base shakers either in a single axis or a selected combination of fixed X, Y, Z configurations, also allowing for rotations dependent upon fixture coupling design.
2. b) Utilising multiple shakers attached directly to the specimen via flexible couplings or similar methods. Here the shakers are attached at any point and in any direction on the specimen. This approach is quite similar to that used for modal testing, but using environmental test severities.

It is emphasised that MESA and MEMA testing currently requires a high degree of engineering judgement and relevant experience, and both test specifier and tester are fully aware of this fact. Generally, MESA and MEMA testing requires greater resources to set up an appropriate test, but potentially provides a more accurate outcome. For the purpose of this document, the creator of the relevant testing specification, the test specifier, is expected to select the procedure and the values of severity appropriate to the specimen and its use. Precursor testing is included within the procedure of this document, as an option, to permit the test specifier to establish the practicality of the test specification and severities with the specimen. A separate specimen is usually provisioned for such precursor testing. The existing single axis, single vibrator test procedures within the IEC 60068‑2 series can be used with a wide range of different excitations, such as broad band random, random on random, sine on random, swept sine, shock, and long-time history replication. Theoretically these different forms of excitations, can also be applied using multi-axis and multi-exciter methods. However, suitable techniques and commercially available test control software, for some of these types of testing, are not necessarily currently commonly available. For this reason, the procedure of this document is currently primarily intended for broad band random and time history replication as facilities to undertake these types of tests are commonly available. With that said, the procedure of this document may be adapted, by the user, for other forms of excitation and advice is provided. Traditionally, vibration, shock and transient test severities are specified using acceleration as the control parameter. However, this is not an essential pre-requisite of the procedure within this document. For the purpose of this document, vibration, shock and transient test severities are specified by the user and may be in the form of acceleration, velocity, displacement, or force. The need to include different control parameters within this document arises because there is a greater likelihood when using multi-exciter testing to specify mixed parameters for control purposes. In which case the vibration, shock and transient waveforms applied to the specimen will be controlled based upon the feedback from transducers measuring the appropriate parameter. Although primarily intended for electrotechnical specimens, this document is not restricted to them and may be used in other fields where desired.