Abstract: The traditional linear elastic model demonstrates large limitation to simulate the creep deformation of the polymethyl methacrylate(PMMA) observation window on human occupied deep-sea vehicle. A linear viscoelastic constitutive model was built based on Prony series form. The mass scaling method together with the equivalent duration method was introduced to accelerate FEM analysis. The numerical-simulation results showed much stability and fitted well with test data. It was concluded that PMMA window showed viscoelastic behavior when loaded gradually to a high level at room temperature. So the viscoelasticity must be considered during a whole loading-holding process. Under quasi-static condition, traditional static FEM was replaced by dynamic explicit FEM which is adaptive to the time-varying property of PMMA viscoelasticity. It was also found that a fillet could help prevent local stress concentration and improve grid convergence.

Key words: deep-sea manned submersible, polymethyl methacrylate (PMMA), observation window, creep, viscoelasticity