Estimation of Residual Stresses in Hydraulically Expanded Tube-to-Tubesheet Joints

1998 ◽  
Vol 120 (2) ◽  
pp. 129-137 ◽  
Author(s):  
M. Allam ◽  
A. Chaaban ◽  
A. Bazergui
Keyword(s):  
Residual Stresses ◽  
Heat Exchangers ◽  
Structural Integrity ◽  
Theoretical Method ◽  
Pressure Level ◽  
The Finite Element Method ◽  
Material Parameters ◽  
Deviation Analysis ◽  
Upper Limit ◽  
Expansion Pressure

The knowledge of residual stresses introduced in the tubes of heat exchangers during their expansion in the tubesheet holes is important because of their effect on the structural integrity of components. This paper presents a simplified theoretical method to calculate the maximum residual stresses introduced in the transition zone of expanded tube-to-tubesheet joint. The higher positive values of tensile residual stresses and their corresponding axial locations are determined by using a standard deviation analysis. The validation of the proposed equations was accomplished by comparing their results to those obtained by the finite element method for some arbitrary cases. An upper limit has been imposed on the expansion pressure level, depending on the combination of the geometrical and material parameters that are involved in the design of the tube-to-tubesheet joints.

Evaluation of the residual stress in stainless steel 304L hydraulically expanded joints

2020 ◽  
pp. 095440892096401
Author(s):  
Ying Hong ◽  
Xuesheng Wang ◽  
Yan Wang ◽  
Zhao Zhang ◽  
Yong Han
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Yield Strength ◽  
Residual Stresses ◽  
Heat Exchangers ◽  
Nuclear Power ◽  
The Finite Element Method ◽  
Power Stations ◽  
Stainless Steel 304 ◽  
Initial Clearance

Stainless steel 304 L tubes are commonly used in the fabrication of heat exchangers for nuclear power stations. The stress corrosion cracking (SCC) of 304 L tubes in hydraulically expanded tube-to-tubesheet joints is the main reason for the failure of heat exchangers. In this study, 304 L hydraulically expanded joint specimens were prepared and the residual stresses of a tube were evaluated with both an experimental method and the finite element method (FEM). The residual stresses in the outer and inner surfaces of the tube were measured by strain gauges. The expanding and unloading processes of the tube-to-tubesheet joints were simulated by the FEM. Furthermore, an SCC test was carried out to verify the results of the experimental measurement and the FEM. There was good agreement between the FEM and the experimental results. The distribution of the residual stress of the tube in the expanded joint was revealed by the FEM. The effects of the expansion pressure, initial tube-to-hole clearance, and yield strength of the tube on the residual stress in the transition zone that lay between the expanded and unexpanded region of the tube were investigated. The results showed that the residual stress of the expanded joint reached the maximum value when the initial clearance was eliminated. The residual stress level decreased with the decrease of the initial tube-to-hole clearance and yield strength. Finally, an effective method that would reduce the residual stress without losing tightness was proposed.

OPTIMUM EXPANSION AND RESIDUAL CONTACT PRESSURE LEVELS OF HYDRAULICALLY EXPANDED TUBE-TO-TUBESHEET JOINTS

1997 ◽  
Vol 21 (4) ◽  
pp. 415-434 ◽  
Author(s):  
M. Allam ◽  
A. Chaaban ◽  
A. Bazergui
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Contact Pressure ◽  
Heat Exchangers ◽  
Statistical Technique ◽  
Triangular Array ◽  
Finite Element Models ◽  
Steam Generators ◽  
Expansion Process ◽  
Expansion Pressure

Tube-to-tubesheet joints in steam generators and other heat exchangers are now often assembled by means of a hydraulic expansion process that plastically deforms the tubes against the tubesheet and thus creates an interference residual contact pressure between the tube and the tubesheet as well as tensile residual stresses in the tube. A good understanding of both the residual contact pressure and the residual stresses is important for establishing the integrity of the expanded joint. The propose of this paper is to investigate the effect of the level of the expansion pressure on both the residual contact pressure an the maximum tensile residual stresses. A comparison between the 3-D and the axisymmetric Finite Element models for a triangular array tube patterns is presented. An analytical equation is proposed for determining the optimum expansion pressure that provides an acceptable level of residual contact pressure and maximum tensile residual stresses. A statistical technique is also carried out to confirm the validity of the proposed approach.

Modified Stoney's Equation for Evaluation of Residual Stresses on Thin Film

2015 ◽  
Vol 789-790 ◽  
pp. 25-32
Author(s):  
Kuen Tsann Chen ◽  
Jui Hsing Chang ◽  
Jiun Yu Wu
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Finite Element Method ◽  
Finite Element ◽  
Residual Stresses ◽  
Present Method ◽  
Neutral Axis ◽  
The Finite Element Method ◽  
Simple Method ◽  
Material Parameters

In the article, a simple method for the modification of the Stoney's equation was presented. The Stoney's equation is proposed from the assumption of equi-biaxial residual stresses in thin films. In this present method, biaxial stresses are different in x-axis and y-axis on thin film. The location of neutral axis depends on the material parameters and the film thickness. The finite element method (FEM) was used to simulate the thermal stress on the thin film. The results of the modified methods are compared with the results of FEM and other literatures. The present method is more accurate than the Stoney's equation in the evaluation of such films.

Uncertainty Quantification of Borehole Thermal Energy Storage Facilities

2020 ◽  
Author(s):  
Philipp Steinbach ◽  
Jens Lang ◽  
Daniel Otto Schulte ◽  
Ingo Sass
Keyword(s):  
Energy Storage ◽  
Uncertainty Quantification ◽  
Thermal Energy ◽  
Heat Exchangers ◽  
Simulation Tool ◽  
The Finite Element Method ◽  
Sources Of Uncertainty ◽  
Material Parameters ◽  
3D Simulation Model ◽  
The Impact

<p>Borehole thermal energy storages (BTES) have become a common implement for extracting and/or storing heat energy from and into the soil. Building these facilities is expensive, especially the drilling of boreholes, into which borehole heat exchangers are inserted. To cut costs, drilling methods, which can produce inaccuracies of varying degree, are utilized. This brings into question how much these inaccuracies could potentially affect the energy storage/extraction performance of a planned facility. To this end, we performed an uncertainty quantification for seasonally operated BTES facilities, where we studied the influence of geometries deviating from the planned layout and other sources of uncertainty, such as varying soil and material parameters.<br>In our research, we make use of a 3D simulation model for BTES facilities in a patch of soil with optional groundwater flow, designed as a system of partial differential equations (PDEs). The system is solved with a simulation toolkit, which was programmed as an extension for the finite element method solver KARDOS. The toolkit builds on previous work for the simulation tool BASIMO and was validated with benchmarks calculated with the commercial software FEFLOW, which specializes in heat transfer in porous media among other things. For the uncertainty quantification, we utilize an adaptive, anisotropic stochastic collocation method, which uses solutions of the PDE system as samples. We present the method and apply it to an illustrative as well as a practical example. Lastly, we discuss the results and assess the impact of deviating borehole paths on the performance of BTES facilities.</p>

Elasto-Plastic Stress Distribution in Triplate Joint Assembly under Bending Moment

2007 ◽  
Vol 345-346 ◽  
pp. 1437-1440
Author(s):  
Tae Hyun Baek ◽  
Seung Kee Koh ◽  
Jie Cheng
Keyword(s):  
Finite Element Method ◽  
Residual Stresses ◽  
Pure Aluminum ◽  
Main Tool ◽  
Bending Moment ◽  
The Finite Element Method ◽  
Shipbuilding Industry ◽  
Structural Parts ◽  
Von Mises

Pre-produced triplate transition joint assemblies are widely used in shipbuilding industry to make welds between aluminum and steel for a number of years now. The straight-shaped transition joint assemblies are bent during shipbuilding. So it is necessary to study the residual stresses created by punch forming, which would have heavy effects on the quality of structural parts. ABAQUS is a suite of powerful engineering simulation programs, based on the finite element method. In this paper, ABAQUS was used as the main tool to simulate the residual stresses in a triplate transition joint after unloading. Punch-pressing was carried to simulate bending moment in ABAQUS. The triplate is consisted of baselayer (steel: Lloyd’s Shipplate Gr. A), interlayer (pure aluminum: Al99.5) and superlayer (Al-Mg alloy: AlMg4.5Mn). Results from the ABAQUS analysis showed that increasing the radius of punch significantly reduced the von Mises residual stresses in steel. Changes of von Mises residual stresses in interlayer (Al99.5) and superlayer (AlMg4.5Mn) were negligible.

Design of a Biomimetic Directional Microphone Diaphragm

2000 ◽  
Author(s):  
C. Gibbons ◽  
R. N. Miles
Keyword(s):  
Sound Pressure ◽  
Capacitive Sensor ◽  
Sound Level ◽  
Pressure Level ◽  
The Self ◽  
Mode Shapes ◽  
Directional Hearing ◽  
The Finite Element Method ◽  
Mechanical Coupling ◽  
Directional Microphone

Abstract A miniature silicon condenser microphone diaphragm has been designed that exhibits good predicted directionality, sensitivity, and reliability. The design was based on the structure of a fly’s ear (Ormia ochracea) that has highly directional hearing through mechanical coupling of the eardrums. The diaphragm that is 1mm × 2mm × 20 microns is intended to be fabricated out of polysilicon through microelectromechanical micromachining. It was designed through the finite-element method in ANSYS in order to build the necessary mode shapes and frequencies into the mechanical behavior of the design. Through postprocessing of the ANSYS data, the diaphragm’s response to an arbitrary sound source, sensitivity, robustness, and Articulation Index - Directivity Index (AI-DI) were predicted. The design should yield a sensitivity as high as 100 mV/Pa, an AI-DI of 4.764 with Directivity Index as high as 6 between 1.5 and 5 kHz. The diaphragm structure was predicted be able to withstand a sound pressure level of 151.74 dB. The sound level that would result in collapse of the capacitive sensor is 129.9 dB.. The equivalent sound level due to the self-noise of the microphone is predicted to be 30.8 dBA.

Hydraulic Versus Swage Autofrettage and Implications of the Bauschinger Effect

2003 ◽  
Vol 125 (3) ◽  
pp. 309-314 ◽  
Author(s):  
A. P. Parker ◽  
G. P. O’Hara ◽  
J. H. Underwood
Keyword(s):  
Residual Stresses ◽  
Experimental Evidence ◽  
Hybrid Method ◽  
Bauschinger Effect ◽  
Pressure Level ◽  
Opening Angle ◽  
Fatigue Lifetime ◽  
Analysis Of Results

A hybrid method is presented which permits calculation of residual stresses in a swage autofrettaged tube including Bauschinger effect. The results are generally supported by three types of available experimental evidence by comparing “equivalent” swage and hydraulic autofrettage tubes having the same level of overstrain. Radial slitting of the swaged tube is predicted to show a greater opening angle than its hydraulic equivalent. Fatigue lifetime of the swaged tube is predicted to be significantly higher than the hydraulic case. Re-pressurization of the equivalent tubes is predicted to produce initial re-yielding at the same pressure in both cases. Analysis of results shows that permanent strains in the swaged tube are expected to appear at a pressure level below that for the hydraulic tube.

Evaluation of Residual Stresses in Butt Welded Joint of Dissimilar Material by FEM

2017 ◽  
Vol 754 ◽  
pp. 268-271 ◽  
Author(s):  
Raffaele Sepe ◽  
M. Laiso ◽  
A. de Luca ◽  
Francesco Caputo
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Arc Welding ◽  
Structural Integrity ◽  
Welded Joint ◽  
Dissimilar Material ◽  
Fe Model ◽  
Butt Joints ◽  
Integrity Assessment ◽  
Steel Joints

The study proposed within this paper deals with an application of finite element techniques to the thermo-structural analysis of a dissimilar butt-welded joint. Residual stresses induced by the fusion arc-welding of steel joints in power generation plants are a concern to the industry. Nowadays, the application of finite element method appears to be a very efficient method for the prediction and the investigation of the weld-induced residual stresses, nevertheless the detailed modelling of all phenomena involved in such process is still challenging. The structural integrity assessment of welded structures strongly requires a deep investigation of weld-induced residual stresses in order to be compliant with safety requirement of power plant. The longitudinal and transversal residual stresses in dissimilar material butt joints of 8 mm thick for V-groove shape were studied. The developed thermo-mechanical FE model as well as the simulation procedures are detailed and results are discussed. As a result of such work, it has been found out that residual stresses in the two dissimilar plates are characterized by very different magnitudes and distribution.

Application of the Finite Element Method (FEM) through GFAS Software to the study of a tunnel

2021 ◽  
Vol 4 (2) ◽  
pp. 001
Author(s):  
Maurizio Ponte ◽  
◽  
Filippo Catanzariti ◽  
Gloria Campilongo
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Computational Simulation ◽  
Theoretical Method ◽  
The Finite Element Method ◽  
Tunnel Excavation ◽  
Analysis System ◽  
Quality Of Products ◽  
Element Method

Computational simulation is widely used in companies to perform analysis and improve the quality of products and projects. Most of these analyses are carried out using software that uses the Finite Element Method, which allows to obtain answers to numerous engineering problems. In this study, two examples of application to the study of tunnels of the Finite Element Method using the Geostru Software "GFAS - Geotechnical F.E.M. Analysis System" are proposed. The case of a tunnel excavated inside a granite rock massif was analyzed, first determining the state of stresses in the cavity contour through a theoretical method and comparing these results with those obtained in the software. Then, by means of finite element modeling, the settlements induced by the excavation were determined. Finally, the problem of tunnel excavation in a viscoplastic rock mass is presented and the authors propose a comparison of the analytical and numerical method.

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