Influence of Geometric Parameters of Conical Acrylic Portholes on Their Stress-Strain Behaviour.

Tetyana Yuresko,Vladimir Kochanov,Pavel Kučera,Václav Píštěk,Andrii Kondratiev

doi:10.3390/polym14051041

Abstract

Translucent elements in the form of truncated cones, which are made of organic glass, are widely used in the structures of portholes, submersible vessels, space vehicles, pressure chambers, teleboxes and other types of technical equipment. The decisive factor in designing portholes is to ensure the strength of their translucent elements. In order to reduce the weight of portholes and, accordingly, to increase the payload, it is necessary to optimise the geometric parameters of the translucent elements, which include the tapering angle and the ratio of thickness to radius of the smaller base. The paper deals with development of the applied (engineering) method for determining the stress–strain behaviour of the conical translucent elements of portholes made of organic glass under the action of a uniform hydrostatic pressure. Finite-element modelling of the translucent element of the conical porthole is performed, with the calculation of its stress–strain behaviour. External hydrostatic pressure of 10 MPa, absence of loads from the inside and continuous sliding of the translucent element with friction along the conical supporting surface of the porthole metal body are the boundary conditions for the computational model. Full-scale tests of translucent elements of portholes made of organic glass were performed under the action of uniform hydrostatic pressure. Analysis of the influence of geometric characteristics of the portholes on stress–strain behaviour showed that the increase in the tapering angle at the constant relative thickness of the translucent element reduced its axial displacement in all cases. Equivalent stresses acquire minimum values when the tapering angle is in the range from 75° to 105° (when the relative thickness increases, the optimal tapering angle becomes smaller). It is shown that the developed method for determination of the stress–strain behaviour of the conical translucent elements of portholes made of organic glass reflects the real picture of deformation and agrees with the results of full-scale tests. Results of the work allow us to choose the rational parameters of the translucent element for increasing the reliability of portholes through the creation of an effective distribution of stresses and strains in the translucent element, and improving its optical characteristics due to a relatively small deflection in operation.

Highlights

There are various designs of portholes adopted in current technology, which can be classified according to the shape and material of the translucent element [1,2]
It is shown that the developed method for determination of the stress–strain behaviour of the conical translucent elements of portholes made of organic glass reflects the real picture of deformation and agrees with the results of full-scale tests
Both both the the geometric thethe translucent element and external surface loads are symmetric around geometricshape shapeofof translucent element and external surface loads are symmetric the central of the porthole, so the stress–strain behaviour behaviour of the translucent element is around theaxis central axis of the porthole, so the stress–strain of the translucent determined by solving the axisymmetric problem of problem the elasticity theory

Summary

Introduction

There are various designs of portholes adopted in current technology, which can be classified according to the shape and material of the translucent element [1,2]. Such diversity is attributed to the differences in operating conditions of the portholes: working pressure; temperature and aggressiveness of the environment; load pattern; image-registration method; and so on [3,4]. The characteristics of strength of translucent elements made of PMMA (the value of pressure at failure) depend primarily on the ratio of thickness h to diameter D of the porthole; and for conical and spherical elements, on the tapering angle α of the supporting surface. Both both the the geometric thethe translucent element and external surface loads are symmetric around geometricshape shapeofof translucent element and external surface loads are symmetric the central of the porthole, so the stress–strain behaviour behaviour of the translucent element is around theaxis central axis of the porthole, so the stress–strain of the translucent determined by solving the axisymmetric problem of problem the elasticity theory.

Methods

Results

Discussion

Conclusion