| Summary: | 碩士 === 國立聯合大學 === 機械工程學系碩士班 === 104 === This study measured the viscoelastic coefficients of acrylic material and creep strains of the acrylic under a long loading time. Use acrylic as the material for the shell structure of the large detectors has been the current trend for most of neutrino experiments. A great neutrino experiment may take many years; hence, the creep deformation due to viscoelastic effect of the acrylic must be considered. In this study acrylic specimens were immersed in liquid scintillator (LAB) and tested by ASTM D790 bending test of constant loading conditions. The acrylic samples were tested with various loading and temperature levels. The creep compliances of the acrylic specimen tested under various temperatures and stress levels were investigated. The experimental data were analyzed by time-temperature superposition principle (TTSP) to construct a master curve and predict the creep behavior of the acrylic in room temperature. A three components linear viscoelastic model was used in this experiment to simulate the creep behavior of the acrylic and the parameters,E1 , E2andη2, of the model were calculated. The difference between the parameters of the raw specimen and annealed specimen were compared.
The result shown the creep compliance of the acrylic increased as the temperature and applied stress increased. At constant loading condition, a master curve combined with the data of four temperature levels can predict the creep compliance as long as 22 years. The viscoelastic parameters of this condition areE1=3771.26(MPa), E2=4535.97 (MPa), η2=5.44 (MPa．s).The elastic modului and viscosity coefficient decreased with increasing stress level.
This phenomenon represents that the creep deformation of the acrylic in high stress level is larger than that of the condition in low stress level. The elastic modului and viscosity coefficient of the annealed specimen were larger than that of raw acrylic specimen. Hence, the strength and the creep behavior of the annealed acrylic may be better than that of the raw acrylic.
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