KopoSYS – The Fatigue Monitoring System

«KopoSYS» is the Greek word for fatigue. In the engineering world, KopoSYS® is a computer system that has been developed by Dr.-Ing. Dimitrios G. Karalis in 2005-2013. The basic concept was to develop a reliable and computationally efficient system that can provide in-situ and on-board the amount of the accumulated fatigue of a welded metallic structure that is equipped with a stress monitoring system.


KopoSYS® operates on the basis of the total stress history of the metallic structure. Periodically and/or upon the owner’s request or after extreme loading, the recorded stress history of the structure is transferred from the strain logger on a different computer. The total stress history is then further processed in situ using KopoSYS® in order to calculate the cumulative fatigue damage ratio of the structure. In-situ fatigue analysis allows for decisions on board, regarding the maintenance and load-bearing capacity of the structure after extreme or severe dynamic loads.

Standards and Rules

Cycle Counting in KopoSYS® is performed on the basis of the standardized Rainflow Cycle Counting Method (according to ASTM, Designation: E1049-85, Reapproved 2005, §5.4.4). For the calculation of the incremental fatigue, each part of unwelded plate or welded joint, which could act as a site for fatigue cracking is placed into one of nine classes, designated A, B, C, D, E, F, F2, G and W according to the guides of the classification societies (ABS, DNV, GL and Lloyd’s). Thus, the material behavior is modeled in the form of S-N curves. On the basis of the aforementioned rules, the mean stress, the plate thickness and the corrosion effects on fatigue damage can also be taken into account upon owner’s request.


A typical fatigue analysis for a given record of nineteen billion (19E+9) stress measurements takes a few hours to complete using a typical desktop computer.


A hardened steel plate is our demo specimen. It is located at the Marine Materials Laboratory in the Hellenic Naval Academy. The plate is equipped with a stress monitoring system and is subjected to random vibration. At the end of every week or after «extreme» loads, the accumulated fatigue of the plate is calculated real time. The access to the demo specimen is free to anyone who wishes to share his ideas with the staff of the laboratory.


Do not hesitate to send us your stress records and discuss the possibility of performing a fatigue analysis. For further details or information please contact directly to: Dr.-Ing. Dimitrios G. Karalis, Hellenic Navy, Hellenic Naval Academy, Mechanics and Materials Division, Marine Materials Laboratory, Hazjikyriakou Avenue, Piraeus 18539, Greece. Email: KaralisDimitris @ TEEmail.gr


Shipbuilding Technology Laboratory, NTUA, http://stl.naval.ntua.gr/

ALS Marine Ltd., http://www.alsmarine.gr/

Glafcos Marine Ltd., http://www.glafcos-marine.com