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Glossary of Used Terms and Nomenclature

Used Terms

This is a temporary solution until I will find a more appropriate and interactive one. There are terms within this site, which deserve a more precise explanation, but its useless to repeat it throughout the rest of the text. I am planning to save this glossary to the database, where a click on a chosen term would start a small popup window with a text input from this database. This Glossary page will be then redundant. If you know a good solution for this problem, please let me know.

Before I prepare the new solution, these links will open one new specific Glossary window. Note that if you minimize it or set behind another window, any click to other unknown term will show you new text there, but this necessarily does not mean that the glossary window will get foreground.

Jan Papuga


Anonymous User

The anonymous user has to fill in the same parameters as the privileged user. Nevertheless, no information, except for his username, will be published or given to other users. He can read data in the database, but he cannot manipulate them within it nor he can add anything new. He does not have access to the user forum. Currently, the only difference to the unknown user (a non-logged visitor) is in availability of PragTic software.


The correspondent is a person who in some way identifies with the ideas of projects reported on or simply is interested in an interaction with the community of people gathered around it. On the other hand, he neither expects to use PragTic and have no need to download it, nor is interested in active participation in the creation of the fatigue databases system. His sole extra authorities in the system of are: 1) reporting on new on-coming conferences; 2) reporting short news in the News section.
Because he gets an opportunity to input data to the system and should in some way guarantee it, he has to disclose his identity in the similar way as privileged users.

Editing of database items

Currently, the manager of the database item is the only user, who can edit it. The expected final state is a bit different and is described in the text further and by revisions:
Privileged users are allowed to edit or add data saved in the databases, but they do not have any option to delete any item. They can directly edit only the data, that they manage. If the data are subject to another manager, the concept of revisions is applied.


The forum should allow the user of PragTic and the databases here to interact and help one another in search for the right solution. The forum is also intended to give me some overview of desires and problems of the user. You can start it by a click on the Forum button on the right panel, but you are invited in only if you are logged into the system as a privileged user.


The manager of any item is the user (usually a privileged one), who created the item in the database. He is responsible for its validity and next development. Until I introduce the idea sketched in the section Concept, if you do not agree with data provided by its manager, you have to write about it to the Forum. The manager is the only person (except for administrator Jan Papuga), who can edit the item that he manages. This is not the final state, see the terms Edit and Revision, where its final idea is sketched.

Notification System

In order to enhance the usability and efficiency of the data system presented on this website, the notification system was established. The users can be informed on selected actions (input of new data, their editing, etc.) occuring on the website by an email automatically generated and sent to his e-mail box. The setup of personal preferences can be done after the login either completely in the second part of the User Profile or on individual webpages concerning any such item (Conferences, Bugs, etc.).
The system will be subsequently introduced to the rest of the website. Within the completion of the system, I hope, I will be able to enable caching of the notifications, so that they could be sent together in one e-mail per a period defined by each user.

Privileged User

This category of a user has a permission to add data into the databases. He can ask to get information about changes in the database. He can use the user Forum to communicate with the other privileged users. He can add reports on new on-coming conferences or simply anything related to the subject of this website (News section). On the other hand, he is asked to disclose a bit more his identity, so that the other users could interact with him. The data, which the privileged user inputs while creating his user account, is shown on his card in the section Users, except for the e-mail, which is kept secret. The privileged users show by such an openness their will to guarantee the data they input.

Revision of database items

This is the last part of the safety measures, which I still have not implemented. The only option today is the direct edit of data, to which you are appointed as the manager.
Except for the common edition of data, to which you have the managerial competence, you could be tempted to revise also data of others. Any change from the originally set values is submitted to approval of its manager. Your proposal does not rewrite the original data automatically. It is marked as a revision and from its definition a 30-day period starts, in which the manager has to assume some attitude to it. He gots an automatically generated e-mail with the information about your revision. In the case the manager does not either reject or approve the change within 30 days, the change is applied and the managing right and duty descend to the editor.If the manager and the editor cannot unite their opinions, they should describe the problem to the Forum.


In order to increase credibility of published data, some items in the database can be signed by any privileged users. Please, sign the items only in the case, that you personally checked it to the original paper where the data are given or you personally made the computation confirming the results in database.


&Delta FI

Common calculation methods oriented on evaluation of the loading towards the fatigue limit can be rewritten to a general formula:

Damage parameter definition,

where the damage parameter Dp is a function of shear C and normal N stress on some particular plane or on more specific planes. The indics a and m are there for amplitude and mean value, while the variable f-1 stands for fatigue limit in a fully reversed axial loading. The inequality mark says that the cases, where the damage parameter is less than the fatigue limit, mark loading, which generates load less than the fatigue limit and thus corresponds to an infinite fatigue life lying behind the fatigue limit.

The right hand side of the inequality above was chosen in order to ensure that it has some physical meaning. Other authors sometimes use other right hand sides, but the clear physics behind this chosen term should be acceptable.

FatLim provides a comparison of validity of calculation methods. All the experimental results gathered correspond to either fatigue limit or some fatigue strength at a definite number of cycles equal or higher to 10^6 cycles. The inequality should become an equality in such a case, but this happens really only rarely. The deviation from the equality shows for the inequality form specified above, how big is the relative deviation from the ideally set multiaxial fatigue limit:

DFI definition,

and is called the fatigue index error here. As regards the quality of the examined calculation method, the smaller Dp parameter than the fatigue limit means that the loading was analysed non-conservatively - the best available criterion should give results close to zero. A negative number thus marks a non-conservative prediction, a positive number relates to a conservative prediction.

Fatigue Data Repository


Weld Data

Bike in-service record

Fatigue Strength estimation via Machine Learning methods



FABER Project



pyLife workshop 2023


Events, Lectures

Workshops on Computational Fatigue Analysis

Workshops on Computational Fatigue Analysis 2023 - FKM Guideline Non-Linear

1st Workshop on Thermodynamics of Fatigue Process

Recorded Lectures

D&DT for Aircraft Engineers

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Development in 2011-2014 supported by:
Alfa programme