Optimum Design of Compound Cylinders Used for Storing Pressurized Fluids

2005 ◽  
Author(s):  
Sunil A. Patil
Keyword(s):  
Internal Pressure ◽  
Optimum Design ◽  
Fluid Pressure ◽  
Element Analysis ◽  
Internal Fluid ◽  
Maximum Hoop Stress ◽  
Trial And Error Method ◽  
Pressurized Fluids ◽  
Hoop Stresses ◽  
Shrink Fit

In the classical design of thick cylinders, if the internal fluid pressure approaches the safe working stress limit of the material, the thickness of the cylinder approaches infinite value. To overcome this difficulty, compound cylinders are used, where another cylinder is shrinkfitted on the inner cylinder. Designing a shrink fit assembly is tricky because the stress developed in the cylinders is a function of internal fluid pressure, shrinkage pressure and the dimensions of the cylinders. Also the shrinkage pressure is a function of the amount of interference and dimensions of the cylinders. That is, unless the shrinkage pressure is known, stresses developed cannot be computed and to compute shrinkage pressure, dimensions of both the cylinders must be known. Hence a cumbersome trial and error method is to be used. In the optimum design of compound cylinders, the thickness of both the cylinders should be just sufficient to withstand the hoop stresses developed. That means the maximum hoop stress produced in both cylinders should be equal. In this, shrinkage (contact) pressure plays an important role. The shrinkage pressure can be such that the limiting compressive stress is produced in inner cylinder. But when subjected to internal pressure, causes unequal stresses in both cylinders. That is, in one of the cylinders, the stress level can be maximum allowable and in other, less than maximum allowable. This paper describes the method of determining the optimum dimensions of both the cylinders made of specified material and to withstand a specified internal pressure so that the volume (and weight) is minimum. The results obtained are verified by using COSMOS and ANSYS finite element analysis packages.

Buckling of Risers in Tension due to Internal Pressure: Nonmovable Boundaries

1983 ◽  
Vol 105 (3) ◽  
pp. 277-281 ◽  
Author(s):  
M. M. Bernitsas ◽  
T. Kokkinis
Keyword(s):  
Internal Pressure ◽  
Fluid Pressure ◽  
Critical Length ◽  
Entire Length ◽  
Tubular Columns ◽  
Internal Fluid ◽  
Static Instability

Open-ended tubular columns may buckle globally as Euler columns due to the action of internal fluid pressure even while they are in tension along their entire length. Hydraulic columns, marine drilling and production risers are, therefore, prone to such static instability. This paper explains this phenomenon, defines the critical riser length for which this instability may occur and provides graphs with values of the critical length which can readily be used for design purposes. Risers with nonmovable boundaries are considered; namely, hinged-hinged, clamped-hinged, hinged-clamped and clamped-clamped risers.

scholarly journals Numerical Study of The Effect of Wall Thickness and Internal Pressure on Von Mises Stress and Safety Factor of Thin-Walled Cylinder for Rocket Motor Case

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Lasinta Ari Nendra Wibawa
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Wall Thickness ◽  
Axial Stress ◽  
Rocket Motor ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Maximum Hoop Stress ◽  
Von Mises

The rocket motor is an important part of rockets. The rocket motor works using the pressure vessel principle because it works in an environment with high pressure and temperature. This paper investigates the von Mises stress that occurs in thin-walled cylinders and safety factors for rocket motor cases due to the influence of the wall thickness and internal pressure. Dimensions of the cylinder length are 500 mm, outer diameter is 200 mm, and cap thickness is 30 mm. The wall thickness is varied 6, 7, 8, and 9 mm, while the internal pressure is varied 8, 9, and 10 MPa. Stress analysis is performed using the finite element method with Ansys Workbench 2019 R3 software. The simulation results show that the maximum von Mises stress decreases with increasing wall thickness. The maximum von Mises stress increases with increasing internal pressure. The material has a safety factor higher than 1.25 for all variations in wall thickness and internal pressure. It means that the material can withstand static loads. The verification process is done by comparing the results of finite element analysis with analytical calculations for maximum hoop stress and maximum axial stress with a fixed boundary condition. The results of maximum hoop stress and maximum axial stress using finite element analysis and analytical calculations are not significantly different. The percentage of errors between analytical calculations and finite element analysis is less than 6 percent.

Stress Predictions at Elbow Ends Under Internal Pressure and System Moments

2010 ◽  
Author(s):  
Jinhua Shi ◽  
Granson Lee ◽  
David Blythe ◽  
John Buckland ◽  
Yuebao Lei ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Hoop Stress ◽  
Stress Distributions ◽  
Finite Element Analyses ◽  
Central Section ◽  
Element Analysis ◽  
3D Finite Element ◽  
Hoop Stresses

In order to assess postulated defects in the butt weld joining a 90 degree elbow to a seamless straight pipe, both axial and hoop stress components at this position are required. ASME III NB-3685 provides a method of calculating elbow stresses. However, this gives the maximum stress values in the elbow and applies to the central section of the bend. If these values are directly used in the defect assessments of welds at the ends of the elbow, the assessment results will be overly conservative. In order to obtain appropriate defect assessment results, more accurate axial and hoop stress distributions at the elbow ends are desirable. In this paper, the axial and hoop stress distributions at the elbow ends are predicted by deriving generalized stress relationships between the elbow end and the central section of the elbow, based on detailed finite element analyses and ASME III NB-3685 calculations. In order to do so, a series of small displacement elastic 3D finite element analyses have been performed. The finite element results were then compared with the ASME III NB-3685 stress predictions. Finally, the axial and hoop stress relationships between the elbow end and the central section of the elbow for internal pressure, in-plane moment and out-of-plane moment were derived. A comparison of the calculated stress values using the derived equations, the finite element analysis results and the ASME III NB-3685 stress calculations confirms that the derived stress relationships are appropriate to predict the axial and hoop stresses at the elbow ends. The objective of this paper is to show: 1) the ASME III NB-3685 stress calculations agree well with the 3D finite element analysis results at the central section of the elbow and 2) the derived stress relationships are appropriate to predict the axial and hoop stresses at the elbow ends.

scholarly journals On Hydromechanical Interaction during Propagation of Localized Damage in Rocks

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 162
Author(s):  
A.A. Jameei ◽  
S. Pietruszczak
Keyword(s):  
Numerical Study ◽  
Fluid Pressure ◽  
Implicit Time ◽  
Integration Scheme ◽  
Internal Length ◽  
Element Analysis ◽  
Equivalent Permeability ◽  
Mechanical Coupling ◽  
Splitting Test ◽  
Localized Damage

This paper provides a mathematical description of hydromechanical coupling associated with propagation of localized damage. The framework incorporates an embedded discontinuity approach and addresses the assessment of both hydraulic and mechanical properties in the region intercepted by a fracture. Within this approach, an internal length scale parameter is explicitly employed in the definition of equivalent permeability as well as the tangential stiffness operators. The effect of the progressive evolution of damage on the hydro-mechanical coupling is examined and an evolution law is derived governing the variation of equivalent permeability with the continuing deformation. The framework is verified by a numerical study involving 3D simulation of an axial splitting test carried out on a saturated sample under displacement and fluid pressure-controlled conditions. The finite element analysis incorporates the Polynomial-Pressure-Projection (PPP) stabilization technique and a fully implicit time integration scheme.

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 Performance Testing and Strength Prediction of Ceramic-to-Metal Joints

1993 ◽  
Author(s):  
J. H. Selverian ◽  
Dave A. ONeil ◽  
Shinhoo Kang
Keyword(s):  
Room Temperature ◽  
Performance Testing ◽  
Strength Prediction ◽  
High Temperature Strength ◽  
Torsional Loading ◽  
Element Analysis ◽  
Failure Theory ◽  
Brazed Joints ◽  
Temperature Shear ◽  
Shrink Fit

Brazed joints were made between silicon nitride and Ni-based and Fe-based super alloys. Room temperature shear (torsion) strengths ranged from 75–242 MPa for Si3N4-to-Incoloy 909 joints and from 30–127 MPa for the Si3N4-to-Inconel 718 joints. At 500 °C the joint strength was 120 MPa while at 650°C and 950°C the joints strengths were less than 20 MPa. These low strengths at 650°C and 950°C were attributed to a reduction in the shrink-fit and to low braze strength at these high temperatures. Finite element analysis (FEA) and a probabilistic failure theory (CARES) were used to predict the joint strengths. The predicted joint strengths agreed well with measured joint strengths in torsional loading at 20°C. Torsion tests were also performed at 650°C. Aspects of the material systems, residual stresses, mechanical behavior, and strength predictions are presented. Two new braze alloys based on the Au-Ni-Cr-Fe system were used to overcome the poor high temperature strength. Joints made with these brazes had good strength (85 MPa and 35 N-m) at 650°C.

In-Plane Parametric Vibrations of Curved Bellows Subjected to Oscillating Internal Fluid Pressure Excitation

2004 ◽  
Author(s):  
Masahiro Watanabe ◽  
Eiji Tachibana ◽  
Nobuyuki Kobayashi
Keyword(s):  
Stability Analysis ◽  
Natural Frequencies ◽  
Parametric Instability ◽  
Fluid Pressure ◽  
Parametric Vibrations ◽  
Internal Fluid ◽  
Mathieu’S Equation ◽  
Stability Maps ◽  
Plane Direction ◽  
Pressure Excitation

This paper deals with the theoretical stability analysis of in-plane parametric vibrations of a curved bellows subjected to periodic internal fluid pressure excitation. The curved bellows studied in this paper are fixed at both ends rigidly, and are excited by the periodic internal fluid pressure. In the theoretical stability analysis, the governing equation of the curved bellows subjected to periodic internal fluid pressure excitation is derived as a Mathieu’s equation by using finite element method (FEM). Natural frequencies of the curved bellows are examined and stability maps are presented for in-plane parametric instability. It is found that the natural frequencies of the curved bellows decrease with increasing the static internal fluid pressure and buckling occurs due to high internal fluid pressure. It is also found that two types of parametric vibrations, longitudinal and transverse vibrations, occur to the curved bellows in-plane direction due to the periodic internal fluid pressure excitation. Moreover, effects of axis curvature on the parametric instability regions are examined theoretically.

Finite Element Analysis of a Gasketed Flange Joint Under Combined Internal Pressure and Thermal Transient Loading

2007 ◽  
Author(s):  
Muhammad Abid ◽  
Javed A. Chattha ◽  
Kamran A. Khan
Keyword(s):  
Finite Element Analysis ◽  
Steady State ◽  
Internal Pressure ◽  
Thermal Loading ◽  
Flange Joint ◽  
Element Analysis ◽  
Transient Loading ◽  
Thermal Transient ◽  
Transient Thermal ◽  
Bolted Flange

Performance of a bolted flange joint is characterized mainly by its ‘strength’ and ‘sealing capability’. A number of analytical and experimental studies have been conducted to study these characteristics only under internal pressure loading. In the available published work, thermal behavior of the pipe flange joints is discussed under steady state loading with and without internal pressure and under transient loading condition without internal pressure. The present design codes also do not address the effects of steady state and thermal transient loading on the structural integrity and sealing ability. It is realized that due to the ignorance of any applied transient thermal loading, the optimized performance of the bolted flange joint can not be achieved. In this paper, in order to investigate gasketed joint’s performance i.e. joint strength and sealing capability under combined internal pressure and transient thermal loading, an extensive nonlinear finite element analysis is carried out and its behavior is discussed.

scholarly journals Tactile Perception for Teleoperated Robotic Exploration within Granular Media

2021 ◽  
Vol 10 (4) ◽  
pp. 1-27
Author(s):  
Shengxin Jia ◽  
Veronica J. Santos
Keyword(s):  
Granular Media ◽  
Fluid Pressure ◽  
Tactile Sensor ◽  
Tactile Perception ◽  
Test Accuracy ◽  
Contact State ◽  
Buried Objects ◽  
Media Type ◽  
Additional Information ◽  
Internal Fluid

The sense of touch is essential for locating buried objects when vision-based approaches are limited. We present an approach for tactile perception when sensorized robot fingertips are used to directly interact with granular media particles in teleoperated systems. We evaluate the effects of linear and nonlinear classifier model architectures and three tactile sensor modalities (vibration, internal fluid pressure, fingerpad deformation) on the accuracy of estimates of fingertip contact state. We propose an architecture called the Sparse-Fusion Recurrent Neural Network (SF-RNN) in which sparse features are autonomously extracted prior to fusing multimodal tactile data in a fully connected RNN input layer. The multimodal SF-RNN model achieved 98.7% test accuracy and was robust to modest variations in granular media type and particle size, fingertip orientation, fingertip speed, and object location. Fingerpad deformation was the most informative modality for haptic exploration within granular media while vibration and internal fluid pressure provided additional information with appropriate signal processing. We introduce a real-time visualization of tactile percepts for remote exploration by constructing a belief map that combines probabilistic contact state estimates and fingertip location. The belief map visualizes the probability of an object being buried in the search region and could be used for planning.

scholarly journals Analysis for Wrinkling Behavior of Girth-Welded Line Pipe

1996 ◽  
Author(s):  
Luiz T. Souza ◽  
David W. Murray
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Finite Element Model ◽  
Internal Pressure ◽  
Experimental Test ◽  
Element Model ◽  
Element Analysis ◽  
Line Pipe ◽  
New Era ◽  
Analytical Tools

The paper presents results for finite element analysis of full-sized girth-welded specimens of line pipe and compares these results with the behavior exhibited by test specimens subjected to constant axial force, internal pressure and monotonically increasing curvatures. Recommendations for the ‘best’ type of analytical finite element model are given. Comparisons between the behavior predicted analytically and the observed behavior of the experimental test specimens are made. The mechanism of wrinkling is explained and the evolution of the deformed configurations for different wrinkling modes is examined. It is concluded that the analytical tools now available are sufficiently reliable to predict the behavior of pipe in a manner that was not previously possible and that this should create a new era for the design and assessment of pipelines if the technology is properly exploited by industry.

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