Time-temperature equivalent characteristics of creep of PMMA for pressure structures in deep-sea equipment
Based on the WLF equation and aging theory,the creep constitutive equation conforming to time-temperat-ure equivalent relation was derived.Compressive creep tests of specimens were carried out at different temperatures,and the compressive creep constitutive relation of polymethyl methacrylate(PMMA)was fitted.The time-temperature equivalent phenomenon of creep deformation of deep-sea equipments'viewport windows was investigated by finite element method(FEM).The experimental results show that the creep constitutive relation of aging theory,which conforms to the WLF equa-tion,can well describe the compressive creep behavior of PMMA under deep deep-sea conditions.When the applied stress is constant,the creep strain-time curve of PMMA at 4℃ is equivalent to 9.36 times of the creep strain-time curve at 40℃ along the time axis.This equivalent relationship can provide a reference for the accelerated creep test design of PMMA pressure structures under deep-sea service environment.
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