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Conception of Fatigue DatabasesAcknowledgementDevelopment of this internet database proceed with financial help from Czech Science Foundation (Project GACR 101/07/P350). I would like to thank for this help. Origin - Why FatLim Was Formed?The conception was born in my mind, when I wrote my PhD thesis. I had a serious problem then - I calculated fatigue prediction for more than ten multiaxial fatigue methods on 129 experimental results. This formed a huge heap of data, which I had to process. But, first, I doubted if all the experimental data are correct. I used secondary sources and was unable to find e.g. the original papers by Nishihara & Kawamoto. I had to believe, that the secondary references are right and that there are no reproduction errors. As I found later, there are many of them. Second, I had to process the data as regards statistic properties of different formed group of experiments with similar loadings. I used to save the results to Excel and subsequently formed a relatively efficient procedure how to add new experimental results to the present data group. But now I get near to 400 experimental results and Excel is giving it up. This is the right time to switch to another way of data manipulation. Third, although I would like, it is nearly impossible to report in detail on achieved prediction results. I believe, that the scientist should analyse his results and give some conclusion to his analysis. But he also should allow to others to check his detailed results or even browse over them in a search for their own goals. Under current circumstances, I am not able to reproduce full details of my work to any scientific paper. But I can't stand those papers which show only overall sums of results. Fourth at last: It is fairly traditional that each author develops his own criterion for fatigue life prediction and verifies it by his own experimental data. Then some other author's data are not satisfied by that criterion, and a new one is suggested. Thus too many proposed criteria have been accumulated, and this testifies, in fact, against the approach of reduction. Many criteria have remained isolated each from other, without comparison or competition. reproduced from S. Stefanov, Int J Fatigue 1996 Well, if I have a tool in my hands, which allows me to do fast computations over many different load regimes and experiments, should not I try to overcome this fractionalism? And if I got some results, should not I allow anybody to see it?
I have to agree with Stefan Stefanov. There are still newer and newer multiaxial methods, but the experimental results on which they are tested are very mild. We should begin to map the current situation as regards existing computational methods - and the databases here are the very start of this process. I think, there are still other experimental results, which can broaden these databases.
Recent State (But Heavily Reconstructed Meanwhile)Exactly, there are several dependant databases, which altogether serve to show you your desired data. These are:
I tried to finish all of them to the final state before the Fatigue 2007 conference, but it is already clear now, that I have failed. Well, I currently spent all the time I promised to the Czech Science Foundation, which so honorably gave some money for it, to invest into their creation. It looks now, that any further changes will take some time, but I will try to keep a steady, although slower pace. Nevertheless, it is very well possible, that you will find some buttons non-functional, but I think that malfunction causing to give you inadequate data should not happen. It is much more probable, that you will get nothing :-) Because the final state of desired functionality is far ahead, I will try to describe you at least my plans in the next chapter. Last DevelopmentAs I noted in the header of the last paragraph, very many changes were implemented meanwhile. Thanks to my experience with FatLim, I continued in my reflections about the current situation in fatigue research. I do not know about any such a broad analysis of this problem and the results are apparently quite worse than those usually reported in research papers. It seems that the activity of researchers is too often impeded by two facts: (1) unavailability of some fatigue solver that would allow fast implementation of new methods and their efficient and quick testing (PragTic solves this problem nicely); (2) unavailability of experimental data for testing of new proposals. From now on (March 2009), the most important database is not the one covering fatigue limits only. The most basic item now is a fatigue curve (currently only of the S-N type, but an extension to Manson-Coffin curves is planned to follow soon), while the fatigue limit is only a specific point on it. Each fatigue curve is composed of individual experimental points with possibility to link the S-N curve parameters derived from the data points. A specific specimen type is related to each fatigue curve. Individual load channels are linked to the fatigue curve independently and the loads induced on them need not to be harmonic or constant only. The two fatigue database interface representations are built around the same core with the information, i.e. the database set is only one. The representation of data is wholly dependant on the point, from which it is called - i.e. either FatLim or FinLiv. The problem started to be a bit too huge for me and thus I have to take a rest for a while, before I continue with it, rearrange the structure a bit again and fill in the respective data. Meanwhile, I welcome any your suggestions. Full FunctionalityI will use bullets so that it would be more clear:
ConclusionWell, I have to sum it up. I wanted to offer you a fully integrated interface to a set of accessible databases which would allow you to estimate, which multiaxial fatigue method is suitable for your use. Although I currently failed to built it in its planned scope (as regards the interactivity above all), I think there are still data which are very useful. So, test it and write me whatever you think over it!!! And if you become a privileged user, you can join our forum and discuss your opinion there. |
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