Rajdip Roy; Lu Qi BTH-AMT-EX--2009/D-02--SE, pp. 56. TEK/avd. för maskinteknik, 2009.
In this master degree thesis the time dependent deformation of packaging material is studied. Mechanical experimental tests were carried out to monitor the stress decreasing rate on paper. Several viscoelastic models were constructed using various theories and compared with the obtained experimental stress relaxation. The results showed that the modified two-unit Maxwell model suits the best to describe the relaxation behavior of the material in discussion. MATLAB was used to derive the stress relaxation equations which indicate the time dependent stress relaxation behavior of the materials for constant elongation. FE models were created by ABAQUS for analyzing the stress relaxation behavior of the paperboard and the laminate. The simulation results were then compared with the experimental results and the theoretical viscoelastic model. Additionally, specimens with a side crack were also studied.
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