G. Laureckienė “Method of yarns long-lasting stress relaxation prediction” doctoral thesis defence

Author, Institution: Ginta Laureckienė, Kaunas University of Technology

Science area, field of science: Technological Sciences, Materials Engineering, 08T

Scientific Supervisor: Prof. Dr. Rimvydas Milašius (Kaunas University of Technology, Technological Sciences, Materials Engineering, 08T).

Dissertation Defence Board of Materials engineering Science Field:
Prof. Dr. Saulius Grigalevičius (Kaunas University of Technology, Technological Sciences, Materials Engineering, 08T) – chairman;
Prof. Dr. Habil. Katarzyna Grabowska, (Lodz University of Technology, Technological Sciences, Materials Engineering, 08T);
Dr. Habil. Małgorzata Matusiak (Lodz University of Technology, Technological Sciences, Materials Engineering, 08T);
Prof. Dr. Jolita Ostrauskaitė (Kaunas University of Technology, Technological Sciences, Materials Engineering, 08T);
Assoc. Prof. Dr. Audronė Ragaišienė (Kaunas University of Technology, Technological Sciences, Materials Engineering, 08T).

The doctoral dissertation is available at the library of Kaunas University of Technology (K. Donelaičio St. 20, Kaunas).

Annotation:

A lot of time is spent on detailed investigations of relaxation processes – from one second to a few days or weeks, and in some cases even more. Different relaxation processes inside the yarns are investigated extensively, however, within a short period of time in comparison, therefore, the behaviour of the product during long-lasting workloads cannot be predicted with reference to them.
The aim of the dissertation – to create a new method for predicting long-lasting stress relaxation of yarns under short-lasting empirical investigations of stress relaxation. While carrying out the investigation, a new method of predicting stress was created according to the break point observed during relaxation. It was found that this break point is common to all the investigated yarns of different constructions and origins, and while having different deformation values. Therefore, such a method can also be applied to other yarns that were not examined in this work. As the experimental investigations of stress relaxation can only be carried out up to a maximum of 1 000 seconds using the created method, the output data can be used to predict the relaxation process for a period of several days. The suggested method allows users to significantly decrease empirical investigations and can assess the relaxation process of the product quite fast, within an hour, in addition to calculating its behaviour for a long period of several days and additionally assist in making a decision about the suitability of the product and/or the values of the load with which the product can be operated.