﻿ 大开口载人潜水器球扇型有机玻璃观察窗有限元分析及试验验证
 舰船科学技术  2020, Vol. 42 Issue (10): 78-82    DOI: 10.3404/j.issn.1672-7649.2020.10.016 PDF

Finite element analysis and test verification of spherical sector acrylic windows of manned submersible with large opening
YU Wen-tao, HU Zhen
China Ship Scientific Research Center, Wuxi 214082, China
Abstract: Manned spherical pressure hull is the key technique for design and manufacture of manned submersible. The strength and sealing of viewport window are always difficulties in the design of manned spherical pressure hull. The dispersion of the material parameter of PMMA is large, the material properties differ in different working environment due to the effect of temperature and stress level. To solve this problem, material parameters were selected in accordance with the test environment by the means of material parameterization analysis, and then on this basis, the viscoelastic model of the material was established by using Prony series fitting when the mechanical behavior of large-opening PMMA observation window is predicted by finite element analysis in this paper. The conventional finite element static analysis for quasi-static loading process was transformed into dynamic analysis and the accuracy of the finite element results was improved effectively under the consideration of the time effect. The relevant calculation results and methods can provide reference experience for the finite element design and calculation of PMMA observation window.
Key words: large opening     window     PMMA     material parameter     viscoelasticity
0 引　言

1 有机玻璃的力学特性

 图 1 室温下有机玻璃压缩应力-应变曲线 Fig. 1 Compression stress - strain curve of PMMA at room temperature

2 观察窗及耐压试验的设计

 图 2 观察窗结构与应变片粘贴位置 Fig. 2 Viewport structure and pasting position of strain gauges
3 大开口球扇型观察窗有限元模型 3.1 建立有限元模型

 图 3 观察窗与球壳的有限元模型 Fig. 3 The finite element model of the viewport and hull
3.2 定义单元类型和材料属性

3.3 划分网格和定义接触对及边界条件

 图 4 有限元网格划分结果 Fig. 4 The finite element meshing result

 图 5 边界条件 Fig. 5 The boundary conditions
3.4 有限元模型验证

 图 6 计算应变值与试验数据对比 Fig. 6 The calculated strain value compared with the test data

 图 7 观察窗的应力云图 Fig. 7 The stress contour plot of the viewport
4 有限元计算结果与试验数据对比 4.1 有机玻璃材料参数化分析

 图 8 不同弹性模量和泊松比下有限元计算结果 Fig. 8 The finite element calculation results under different elastic modulus and poisson’s ratio

 图 9 材料参数（0.35，3700）下的计算值与试验值的对比 Fig. 9 The calculated value under the material parameters（0.35, 3700） compared to the test value
4.2 有机玻璃线性粘弹性模型

 $E\left( t \right) = {E_0}\left[ {1 - \sum\nolimits_i {{a_i}} \left( {1 - {{\rm{e}}^{ - \frac{t}{{{\tau _i}}}}}} \right)} \right]\text{。}$ (1)

 图 10 Prony级数拟合曲线与蠕变实验数据的比对 Fig. 10 Prony series fitted curve compared to the creep test data

 图 11 粘弹性模型的有限元计算结果 Fig. 11 The finite element calculation results of viscoelastic model
5 结　语

1）线性粘弹性模型相较于线弹性模型，能够获得更精确的有限元计算结果。但是由于线性粘弹性模型的局限性，本文忽略了不同应力水平对材料粘弹性和泊松比的影响，后续需要进一步研究探讨。

2）由于有机玻璃属于粘弹性材料，其材料力学性能参数受温度和应力水平影响很大，因此在用有限元计算其响应时，注意到耐压结构的不同工作环境（温度及压力）下材料参数的不同，适当变化材料参数能有效提高计算结果的准确度。

3）有机玻璃本身的力学性能离散性较大，在结构耐压试验之前，通过试件的拉压等其他试验取得材料对应的力学性能参数，对于提高有限元计算精度有重要意义。

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