Structural Reinforcement of Viewports in Spherical Pressure Hull for Manned Submersibles

2014 ◽  
Vol 48 (3) ◽  
pp. 17-24 ◽  
Author(s):  
Bhaskaran Pranesh ◽  
Dharmaraj Sathianarayanan ◽  
Sethuraman Ramesh ◽  
Gidugu Ananda Ramadass
Keyword(s):  
Atmospheric Pressure ◽  
Hoop Stress ◽  
Sea Water ◽  
External Pressure ◽  
Element Analysis ◽  
Structural Reinforcement ◽  
Replacement Method ◽  
Axis Of Symmetry ◽  
Spherical Pressure ◽  
Design Pressure

AbstractManned submersibles are underwater vehicles. These vehicles are equipped with an atmospheric pressure casing called a spherical pressure hull, which can accommodate up to three people. The spherical pressure hull facilitates safe passage to high-pressure environments. It has circular openings that serve as viewports to enable underwater viewing and intervention. The regions near the openings are the weakest in the pressure hull and must be reinforced. Reinforcement of the viewports is performed using the area replacement method. The amount of material removed from the viewport opening must be replaced along the axis of symmetry of the opening. This is the minimum amount of material that must be placed along the circumference of the viewports. Reinforced viewports in the pressure hull are analyzed using finite element analysis, and the stresses are classified into primary and secondary stresses. The reinforcements of the viewports are carried out in such a way that the calculated primary and secondary stresses are below the permissible limits.Abbreviations:P ‐ External pressure (design pressure)Dm ‐ Mean diameter of the pressure hullRm ‐ Mean radius of the pressure hullt ‐ Thickness of the pressure hullσ ‐ Hoop stressPy ‐ Pressure at yield strength of the materialPb ‐ Buckling pressureE ‐ Young’s modulus of the materialγ ‐ Poisson’s ratioMSW ‐ Meters of sea water

Research of Reinforce Stress on the Pressure Structure of Submersible Vehicle

2014 ◽  
Vol 496-500 ◽  
pp. 590-593
Author(s):  
Guan Nan Chu ◽  
Qing Yong Zhang ◽  
Guo Chun Lu
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Distribution ◽  
Hoop Stress ◽  
External Pressure ◽  
Finite Element Models ◽  
Cylinder Pressure ◽  
Simulation Experiments ◽  
Element Analysis ◽  
Load Carrying

In order to improve the load-carrying properties of pressure structure, a new method to improve the external bearing limit is put forward and residual stress is used. Based on finite element analysis, finite element models of cylinder pressure structure of submersible vehicle are established to produce hoop residual stress in the process of outward expansion. According to a lot of data of simulation experiments, the result indicates that hoop residual stress is compressive on the outer surface of the pipe and the hoop stress keeps tensile on the inside surface. This kind of stress distribution is helpful to the cylinder structure and can improve its bearing capacity of external pressure. Moreover, the rules of the residual stress are got. The influences of physical dimension, yield strength of material and the expansion rate to the stress distribution are analyzed. The measures to produce the stress distribution are also presented.

Manufacturing Imperfection Sensitivity Analysis of Spherical Pressure Hull for Manned Submersible

2013 ◽  
Vol 47 (6) ◽  
pp. 64-72 ◽  
Author(s):  
Bhaskaran Pranesh ◽  
Dharmaraj Sathianarayanan ◽  
Sethuraman Ramesh ◽  
Gidugu Ananda Ramadass
Keyword(s):  
Numerical Analysis ◽  
Parametric Design ◽  
External Pressure ◽  
Imperfection Sensitivity ◽  
Element Analysis ◽  
Allowable Deviation ◽  
Buckling Behavior ◽  
Manufacturing Procedure ◽  
Manned Submersible ◽  
Spherical Pressure

AbstractAny pressure hull invariably has imperfections as a result of the manufacturing procedure. Imperfections in a spherical pressure hull are the basis for localized buckling and deformation behavior. Numerical analysis and analytical calculations are carried out to predict the buckling behavior and strength of a pressure hull made of titanium alloy (Ti-6Al-4V) for both perfect and imperfect pressure hulls. Finite element analysis is carried out for different imperfection angles to see the effect on strength and buckling. Results of numerical analysis show that there is considerable reduction in both buckling pressure and strength as a result of imperfections. Hence, allowable deviation due to imperfection for a spherical pressure hull has to be considered for thickness calculations.Abbreviations:P  external pressure (Design pressure)Dm  mean diameter of the pressure hullRm  mean radius of the pressure hullRi  imperfect radius of the pressure hullt  thickness of the pressure hullΔR  imperfect deviationδ  imperfection angleσ  hoop stressPy  pressure at yield strength of the materialPb  buckling pressureE  Young’s modulus of the materialμ  Poisson’s ratioMSW  meters of sea waterAPDL  ANSYS Parametric Design Language

scholarly journals Failure Analysis on a Collapsed Flat Cover of an Adjustable Ballast Tank Used in Deep-Sea Submersibles

2019 ◽  
Vol 9 (23) ◽  
pp. 5258
Author(s):  
Fang Wang ◽  
Mian Wu ◽  
Genqi Tian ◽  
Zhe Jiang ◽  
Shun Zhang ◽  
...  
Keyword(s):  
Deep Sea ◽  
Material Selection ◽  
High Strength ◽  
External Pressure ◽  
Element Analysis ◽  
Ballast Tank ◽  
Material Inhomogeneity ◽  
Comprehensive Properties ◽  
Ultimate Cause ◽  
Flat Cover

A flat cover of an adjustable ballast tank made of high-strength maraging steel used in deep-sea submersibles collapsed during the loading process of external pressure in the high-pressure chamber. The pressure was high, which was the trigger of the collapse, but still considerably below the design limit of the adjustable ballast tank. The failure may have been caused by material properties that may be defective, the possible stress concentration resulting from design/processing, or inappropriate installation method. The present paper focuses on the visual inspections of the material inhomogeneity, ultimate cause of the collapse of the flat cover in pressure testing, and finite element analysis. Special attention is paid to the toughness characteristics of the material. The present study demonstrates the importance of material selection for engineering components based on the comprehensive properties of the materials.

Fitness for Service Assessments of Bulging and Out-of-Round Structures

2004 ◽  
Author(s):  
Peter Carter ◽  
D. L. Marriott ◽  
M. J. Swindeman
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Structural Model ◽  
External Pressure ◽  
Element Analysis ◽  
Structural Imperfection ◽  
Level 2

This paper examines techniques for the evaluation of two kinds of structural imperfection, namely bulging subject to internal pressure, and out-of-round imperfections subject to external pressure, with and without creep. Comparisons between comprehensive finite element analysis and API 579 Level 2 techniques are made. It is recommended that structural, as opposed to material, failures such as these should be assessed with a structural model that explicitly represents the defect.

scholarly journals Viscoelastic analysis of Calving Glaciers

1980 ◽  
Vol 1 ◽  
pp. 37-41 ◽  
Author(s):  
D. V. Reddy ◽  
W. Bobby ◽  
M. Arockiasamy ◽  
R. T. Dempster
Keyword(s):  
Finite Element ◽  
Sea Water ◽  
Water Pressure ◽  
Computer Code ◽  
Ice Shelf ◽  
Element Analysis ◽  
Ice Shelves ◽  
Shear Moduli ◽  
Relaxation Functions ◽  
Spring Force

Calving of floating ice shelves is studied by a viscoelastic finite-element analysis. The fan-shaped breaking-up of glaciers due to forces that cause bending on creeping ice is assumed to be axisymmetric. Bending may be due to geometry of the bcdrock, action of tides and waves, and imbalance (at the ice front) between the stress in the ice and the sea-water pressure.The bulk and shear moduli of the ice are represented by relaxation functions of the Prony series, which is a discrete relaxation spectrum composed of a constant and a summation of exponential terms. These properties are also functions of temperature, that varies over the thickness of the ice shelf. The temperature distribution across the thickness of the ice is obtained from calculations based on a linear dependence of thermal conductivity on the temperature. Numerical results are presented for various calving mechanisms. A computer code, VISIC1, is developed by modifying a finite-element viscoelastic code, VISICE, for floating ice islands. The buoyancy of the water is taken into account by a Winkler spring model, with the spring force determined from displaced volume. Locations of crack initiation obtained from the analysis are used to predict the iceberg size immediately after calving.

Thermal Hydraulic Analysis of Severe Accident in PFBR

2010 ◽  
Author(s):  
K. Velusamy ◽  
P. Chellapandi ◽  
G. R. Raviprasan ◽  
P. Selvaraj ◽  
S. C. Chetal
Keyword(s):  
Atmospheric Pressure ◽  
Fluid Dynamic ◽  
Hydraulic Modeling ◽  
Severe Accident ◽  
Maximum Temperature ◽  
Maximum Pressure ◽  
Dynamic Calculation ◽  
Thermal Hydraulic Modeling ◽  
Thermal Hydraulic Analysis ◽  
Design Pressure

During a core disruptive accident (CDA), the amount of primary sodium that can be released to Reactor Containment Building (RCB) in Prototype Fast Breeder Reactor (PFBR) is estimated to be 350 kg/s, by a transient fluid dynamic calculation. The pressure and temperature evolutions inside RCB, due to consequent sodium fire have been estimated by a constant burning rate model, accounting for heat absorption by RCB wall, assuming RCB isolation based on area gamma monitors. The maximum pressure developed is 7000 Pa. In case RCB isolation is delayed, then the final pressure inside RCB reduces below atmospheric pressure due to cooling of RCB air. The negative pressure that can be developed is estimated by dynamic thermal hydraulic modeling of RCB air / wall to be −3500 Pa. These investigations were useful to arrive at the RCB design pressure. Following CDA, RCB is isolated for 40 days. During this period, the heat added to RCB is dissipated to atmosphere only by natural convection. Considering all the possible routes of heat addition to RCB, evolution of RCB wall temperature has been predicted using HEATING5 code. It is established that the maximum temperature in RCB wall is less than the permissible value.

scholarly journals Prediction of Bone Damage Formation in Resurfacing Hip Arthroplasty

2019 ◽  
Vol 9 (1) ◽  
pp. 5879-5885
Keyword(s):  
Hip Arthroplasty ◽  
Hip Replacement ◽  
Femoral Bone ◽  
Cobalt Chromium ◽  
Element Analysis ◽  
Left Femur ◽  
Bone Model ◽  
Replacement Method ◽  
Physiological Loading ◽  
Resurfacing Hip Arthroplasty

Resurfacing Hip Arthroplasty (RHA) is a hip replacement method that is widely known nowadays. However, the complication on femoral bone fracture often happens in this hip replacement method which associated with the implant positioning. The objective of this study is to predict the damage formation on the bone which resulting from the RHA pin malposition. Finite element analysis was conducted in order to predict the damage formation on the bone model based on the computed tomography (CT) image of a patient. A 3D inhomogeneous bone model was developed from a 47 year old patient with an osteoarthritis disease located on the left femur. The material used for the RHA implant model is cobalt chromium and the implant is then being inserted into the femoral bone. Straight implant position with angle 130° was selected as a reference in the analysis while another three position of varus (> 130°) and valgus (<130°) were selected and known as the pin malposition. The simulation was conducted on each of the selected angles in order to predict the damage formation towards the bone model. The damage formation obtained was from the results of elements failure which occurred after applying the load. Physiological loading of a human which focusing on the normal walking condition was selected as the loading and boundary condition in this study. The femoral bone model experienced the highest damage formation when the implant located at the varus position while reduced significantly when the implant placed at the valgus position.

Selecting the Optimum Bolt Assembly Stress: Influence of Flange Type on Flange Load Limit

2008 ◽  
Author(s):  
Warren Brown
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Carbon Steel ◽  
Applied Load ◽  
Hoop Stress ◽  
Elastic Analysis ◽  
Steel Weld ◽  
Element Analysis ◽  
Load Limit ◽  
Stress Influence

In previous papers, practical limits on the maximum applied load for standard ASME B16.5 and B16.47 carbon steel, weld neck pipe flanges were examined. A new code equation for the tangential (hoop) stress at the small end of the hub for a weld neck flange was developed to facilitate calculation of the limits using elastic analysis. The results were verified against elastic-plastic Finite Element Analysis (FEA). In this paper, the work is extended to include other flange configurations, including loose ring flanges, slip-on flanges and flat plate flanges. This paper is a continuation of the papers presented during PVP 2006 and PVP 2007 (Brown [1, 2]) and it extends the scope of the proposed methodology for determining flange stress limits in determining the maximum allowable bolt load for any given flange size and configuration.

Kinematic Synthesis of a D-Drive MEMS Device With Rigid-Body Replacement Method

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Paolo Sanò ◽  
Matteo Verotti ◽  
Paolo Bosetti ◽  
Nicola P. Belfiore
Keyword(s):  
Rigid Body ◽  
Experimental Testing ◽  
Micro Electro Mechanical System ◽  
Element Analysis ◽  
Kinematic Synthesis ◽  
Replacement Method ◽  
Rigid Body Model ◽  
Mems Device ◽  
Conjugate Surfaces ◽  
Line Path

In this paper, a microsystem with prescribed functional capabilities is designed and simulated. In particular, the development of a straight line path generator micro electro mechanical system (MEMS) device is presented. A new procedure is suggested for avoiding branch or circuit problems in the kinematic synthesis problem. Then, Ball's point detection is used to validate the obtained pseudo-rigid body model (PRBM). A compliant MEMS device is obtained from the PRBM through the rigid-body replacement method by making use of conjugate surfaces flexure hinges (CSFHs). Finally, the functional capability of the device is investigated by means of finite element analysis (FEA) simulations and experimental testing at the macroscale.

Applicability of Design Rules for Openings in Shells, ASME B&PV Code, Section VIII, Division 2 - A Case Study

2021 ◽  
Author(s):  
Gurumurthy Kagita ◽  
Krishnakant V. Pudipeddi ◽  
Subramanyam V. R. Sripada
Keyword(s):  
Stress Analysis ◽  
Failure Modes ◽  
Element Analysis ◽  
Design Rules ◽  
Area Method ◽  
Replacement Method ◽  
Local Stresses ◽  
Pressure Area ◽  
Section Viii ◽  
Division 2

Abstract The Pressure-Area method is recently introduced in the ASME Boiler and Pressure Vessel (B&PV) Code, Section VIII, Division 2 to reduce the excessive conservatism of the traditional area-replacement method. The Pressure-Area method is based on ensuring that the resistive internal force provided by the material is greater than or equal to the reactive load from the applied internal pressure. A comparative study is undertaken to study the applicability of design rules for certain nozzles in shells using finite element analysis (FEA). From the results of linear elastic FEA, it is found that in some cases the local stresses at the nozzle to shell junctions exceed the allowable stress limits even though the code requirements of Pressure-Area method are met. It is also found that there is reduction in local stresses when the requirement of nozzle to shell thickness ratio is maintained as per EN 13445 Part 3. The study also suggests that the reinforcement of nozzles satisfy the requirements of elastic-plastic stress analysis procedures even though it fails to satisfy the requirements of elastic stress analysis procedures. However, the reinforcement should be chosen judiciously to reduce the local stresses at the nozzle to shell junction and to satisfy other governing failure modes such as fatigue.

Sign in / Sign up

Export Citation Format

Share Document