The vibration analysis tools known as Maximum Response Spectra (MRS) and Fatigue Damage Spectra (FDS) were originally developed within the French Atomic Energy Authority. Over the years the CEEES TABME has acted as a forum for dissemination of techniques and applications associated with MRS & FDS.
Two papers are included here;
The first paper uses MRS and FDS to compare the damage effects of different test severities for transportation. Although the original intent was a comparison between different severities with the UK Defence Standard Def Stan 00-35, it includes a number of other test severities from other standards.
The second paper sets out an exercise involving the acquisition of automotive vibration data and the conversion of this, using MRS and FDS, into a test severity for automotive applications.
The original purpose was as a means of comparing the affects of different vibration environments on equipment. The different vibration environments were compared in terms of their damage potential effects on notional components within the equipment. The normal damage effects addressed were peak acceleration response relating to internal loadings, (by means of Maximum Response Spectra) and fatigue (by means of Fatigue Damage Spectra). However, consideration of absolute and relative displacement is also possible to ensure motions do not exceed the available dynamic spatial envelope.
The French Atomic Energy Authority published their work on MRS and FDS in the mid 1970’s and papers on the subject were published in France, the UK and the US. Unfortunately, because the method required a lot of computing and specialist computer programming, it was not extensively taken up at that time. To alleviate the computational problems the originator of the method produced solutions specific to random vibration and sine sweeps. By making a number assumptions very significant improvements in computing time could be made. However, the necessary assumptions for random vibration and sine sweeps are different. In consequence, there was always a doubt that any differences may originate from the different assumptions rather than the environment. To encourage wider use of MDS and FDS the originator also produced public domain computer programs, such as DEGAT, able to run on PC’s.
In recent years the capabilities, have become readily available, to undertake the extensive computing required by MRS and FDS. In addition the use of MRD and FDS as a quantitative basis for setting test severities has been shown to be practicable. The advantage of using MRD and FDS as a quantitative basis for setting vibration test severities is that they can be used to set a traceable severity in terms of both vibration amplitude and test duration. This has been taken up by the French MOD who have embedded the procedure into GAM EG 13. Moreover, the process has received substantial EU research funds and is now a commercially available product.