Numerical and experimental study on the safety of viewport window in a deep sea manned submersible
TL;DR: In this article, the viewport window in pressure hull is susceptible to high stress and can experience cracks at its corner, and a numerical analysis is carried out on the observed viewport behavior.
Abstract: Viewport window in pressure hull is susceptible to high stress and can experience cracks at its corner. For studying the viewport behaviour at its corner a numerical analysis is carried out on the ...
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TL;DR: In this article, a viscoelastic model of viewport windows under constant seawater pressure was developed to evaluate the creep and damage behaviors of viewports. But the authors did not consider the impact of the damage on the viewport window lifetime.
7 citations
TL;DR: In this paper, a three-element spring-dashpot viscoelasticity/damage model is used to predict the viscoeling behaviors of PMMA viewport windows at 1-7 km water depths during the dive stage, the creep behaviors during the operation stage, and the creep recovery behaviors during a rise stage.
3 citations
TL;DR: Wang et al. as discussed by the authors proposed a method based on polarization imaging to evaluate the stress accumulation and recovery in the conical frustum window, which can characterize the stress transfer process and the elastic-plastic transformation process of the window under different pressurization pressures.
Abstract: Stress detection of the conical frustum window is a very important issue to ensure the safety of deep manned submersibles. In this paper, we propose a method based on polarization imaging to evaluate the stress accumulation and recovery in the conical frustum window. An experimental setup of Mueller matrix polarimetry is built, and the samples are made by referring to the typical conical frustum windows in submersibles. By pressurizing different pressures on the samples, we can find the changes of their Mueller matrix images and further derived polarization parameters. The results show that the polarization parameters can characterize the stress transfer process and the elastic–plastic transformation process of the window under different pressurization pressures. We also use a two-layered wave plate model to simulate the stress distribution in the window, which reveals different performances of the former and latter layers of the window under pressurization. Finally, we use a finite element model to simulate and understand some of the above experimental results. This proposed method is expected to provide new possibilities for monitoring the window stress and further ensure the safety of deep manned submersibles.
2 citations
TL;DR: In this article , the authors developed a method for determining the stress-strain behavior of the conical translucent elements of portholes made of organic glass under the action of a uniform hydrostatic pressure.
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.
1 citations
TL;DR: In this paper, the effects of compression rate, sealing gap, working medium pressure, and rubber hardness on the O-ring sealing performance of manned submersible viewports were studied. But the authors focused on the large deformation contact analysis between the viewport and the seat under water depth 100-500m.
Abstract: This paper studies the effects of compression rate, sealing gap, working medium pressure, and rubber hardness on the O-ring sealing performance of manned submersible viewports. Large-deformation contact analysis between the viewport and the seat under water depth 100–500 m is performed using implicit finite element analysis (FEA), after introducing the Mooney–Rivlin hyperelastic constitutive model for the nitrile rubber O-ring. The influence laws of various parameters above on the O-ring sealing performance of viewport are obtained by studying the distributions of the von Mises stress and contact stress as well as the contact width. This work provides numerical approach for design and analysis of the O-ring sealing of viewports.
1 citations
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TL;DR: In this paper, a new method was developed which allows the reduction of localized notch stresses in two-dimensional and three-dimensional elastic structures in a very effective way, with only a commercial finite-element code (the authors used ABAQUS) required.
256 citations
TL;DR: In this article, the authors show how 15 years after the CAO-method drastic simplifications are available, and how notch shape optimization in many cases can be done without the FEM-codes, with a pocket calculator or even simpler with a graphic method.
56 citations
TL;DR: In this paper, the contact finite element (FE) model is provided for the conical window and validated accordingly based on the presented FE model, the stress and deformation characteristics have been accomplished for the thick conical windows and then the failure reasons and design criterion of acrylic plastics viewports are thoroughly investigated by comparing with the experiment data and those from some existed windows.
Abstract: For new manned submersibles to dive deep sea, the conical frustum windows need to be designed under external uniform pressure, not only based on the rule design method but also verified by numerical or experimental methods. In this paper, the contact finite element (FE) model is provided for the conical window and validated accordingly. Based on the presented FE model, the stress and deformation characteristics have been accomplished for the thick conical window and then the failure reasons and design criterion of acrylic plastics viewports are thoroughly investigated by comparing with the experiment data and those from some existed windows. Meanwhile, the structural characteristics especially for stress concentration have been exposed by numerical calculation. Finally, the failure of conical frustum viewport has been discussed totally referring to the existing design criteria and some principles for its optimal design have been proposed.
19 citations
TL;DR: In this paper, the basic dimensions of the viewport window and its flange were determined using ASME PVHO-1, and the use of the biological growth method for structural shape modification reduced the stress acting on the acrylic viewport by 71%.
Abstract: Manned submersibles are important platforms for exploration and research under the oceans. One of the most important components of the manned submersible is the viewport, which develops high stresses due to the nature of its design. The basic dimensions of the viewport window and its flange are determined using ASME PVHO-1. Analysis of the viewport for given basic dimensions, shows that the corners of the low-pressure face of the viewport window and the notch regions of the flange are subjected to high stresses. Using the fillet radius method at the notch region results in stress reduction by 64%. The biological growth method helps in getting the naturally optimised shape at the corner. The use of the biological growth method for structural shape modification reduces the stress acting on the acrylic viewport by 71%. The same method applied to the flange notch region reduces its sharpness and the stress there by a considerable amount. This also helps in increasing the number of cycles of operation.
14 citations
01 Jan 2014
TL;DR: Wang et al. as discussed by the authors used a piecewise function combined Gumbel and Weibull distributions for data fitting, which integrates both the divefrequency of each depth range and the duration that maximum stress acts.
Abstract: Acrylic plastic, polymethylmethacrylate (PMMA), are widely employed as the material for the viewports of human occupied vehicle (HOV) which usually dives into deep sea. The service life of viewport is critical to the reliability and safety of HOV. In order to predict life of viewport in design stage, mathematical statistics method is applied to establish the load spectrum for viewport. It is found that ALVIN (America) HOV’s dive-depth data is in a skewed distribution, and a piecewise function combined Gumbel and Weibull distributions is proposed for data fitting. HOV undertakes long-term and cyclic load in service, which will cause damage on viewport, so a creep-fatigue load spectrum is established and applied for JIAOLONG (China) HOV’s viewport, which integrates both the divefrequency of each depth range and the duration that maximum stress acts. The proposed method for determination of creep-fatigue load spectrum could thus be considered to be employed for failure analysis and life prediction of modern HOV’s viewport.
6 citations