Application of non-contact strain measurement based on CCD camera in PMMA material constitutive model

Abstract The Jiangmen Underground Neutrino Observation (JUNO) will build a polymethyl methacrylate (PMMA) spherical vessel of diameter 35.4 meters. constitutive model PMMA is key parameter for the design structure. bulk polymerization bonding area often weak point structure, so it useful to understand areas FEA. However, traditional contact strain measurement methods, such as extensometer and resistance gauge, have an impact on PMMA, lossy measurement. Traditional measuring methods also can’t measure small-sized 3 mm in most structures. non-contact method based CCD camera studied. tensile test result shows that influence environment value less than 0.01%. two extensometer, are compared. curves obtained by highly consistent, maximum difference 8.53 e-4. fracture specimen 4.32% slight plastic deformation has occurred. Zhu-Wang-Tang (ZWT) nonlinear viscoelastic fitting stress-strain data. with equations different when length ratio different. By analyzing relationship between coefficients equation, equation finally obtained. results show coefficient E 0 smaller mother material. 2.60%, lower material, which makes ${\beta }$?> β opposite sign strength about 85.68% become one points