STRUCTURAL STRESS METHOD FOR FATIGUE DESIGN OF CONCRETE FILLED STEEL TUBULAR T-JOINTS UNDER AXIAL LOADING

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Idris A. Musa
Keyword(s):  
Fatigue Life ◽  
Three Dimensional ◽  
Axial Loading ◽  
Fe Model ◽  
Structural Stress ◽  
Stress Concentrations ◽  
Engineering Structures ◽  
T Joints ◽  
Tubular Joints ◽  
Concrete Filling

Steel tubular structural members are being widely used in various engineering structures. The steel tubular joints will have fatigue problem when subjected to repetitive loading. Fatigue strength is one of the key factors that control the design of steel tubular joints in structures subjected to frequent loading. Research has shown that concrete filling of the steel tubes can effectively reduce stress concentrations at the joint. In this study, the structural stress method which involves the through-thickness stress distribution, has been employed to estimate the fatigue life of concrete filled steel tubular (CFST) T-joints under axial loading in the brace. A Finite Element (FE) model has been developed using ABAQUS. The three-dimensional 8-node hexahedral element has been employed in the FE model. The structural stresses have been extracted and the fatigue life of the joint has been estimated. The results have been verified using experimental results reported in the literature. The current study showed that the structural stress method can effectively predict reliable fatigue life in concrete filled steel tubular (CFST) T-joints.

Finite Element Analysis of Elliptical Chord

2013 ◽  
Vol 3 (4) ◽  
pp. 44-61
Author(s):  
K. S. Narayana ◽  
R. T. Naik ◽  
R. C. Mouli ◽  
L. V. V. Gopala Rao ◽  
R. T. Babu Naik
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Three Dimensional ◽  
Compressive Load ◽  
Dynamic Strength ◽  
Element Analysis ◽  
T Joints ◽  
Shell Elements ◽  
Tubular Joints ◽  
Plane Bending

The work presents the Finite element study of the effect of elliptical chords on the static and dynamic strength of tubular T-joints using ANSYS. Two different geometry configurations of the T-joints have been used, namely Type-1 and Type-2. An elastic analysis has been considered. The Static loading conditions used are: axial load, compressive load, In-plane bending (IPB) and Out-plane bending (OPB). The natural frequencies analysis (dynamic loading condition) has also been carried out. The geometry configurations of the T-joints have been used, vertical tubes are called brace and horizontal tubes are called chords. The joint consists of brace joined perpendicular to the circular chord. In this case the ends of the chord are held fixed. The material used is mild steel. Using ANSYS, finite element modeling and analysis of T-joint has been done under the aforementioned loading cases. It is one of the most powerful methods in use but in many cases it is an expensive analysis especially due to elastic–plastic and creep problems. Usually, three dimensional solid elements or shell elements or the combination of two types of elements are used for generating the tubular joints mesh. In tubular joints, usually the fluid induced vibrations cause the joint to fail under resonance. Therefore the natural frequencies analysis is also an important issue here. Generally the empirical results are required as guide or comparison tool for finite element investigation. It is an effective way to obtain confidence in the results derived. Shell elements have been used to model the assembled geometry. Finite element ANSYS results have been validated with the LUSAS FEA and experimental results, that is within the experimentation error limit of ten percentage.

scholarly journals Fatigue life assessment of welded joints in a crane boom using different structural stress approaches

2019 ◽  
Vol 13 (2) ◽  
pp. 5048-5073
Author(s):  
Brahami Riad ◽  
Hamri Okba ◽  
Sfarni Samir
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Industrial Structure ◽  
Life Assessment ◽  
Structural Stress ◽  
Element Analysis ◽  
Tubular Joints ◽  
Fatigue Life Assessment

This article presents a study of the fatigue strength of welded parts in a crane boom. First, a finite element analysis was carried out over the whole structure. Two critical welded zones were identified and a detailed analysis was carried on them, in the form of sub-models. Three different approaches for estimating the structural stress in welded zones, were presented and applied to each sub-model. Results were compared and discussed. The evaluation of fatigue resistance by the use of appropriate S-N curves for each method was also carried out and discussed. The use of these approaches on a complex industrial structure, and on tubular joints with hollow sections required to perform many adaptations and to solve several difficulties presented hereafter.

scholarly journals Effect of geometric parameters and combined loading on stress distribution of tubular T-joints

Mechanika ◽  
2019 ◽  
Vol 25 (5) ◽  
pp. 350-356
Author(s):  
Samira Belhour ◽  
Hafida Kahoul ◽  
Ahmed Bellaouar ◽  
Sébastien Murer
Keyword(s):  
Axial Loading ◽  
Computation Time ◽  
Geometric Parameters ◽  
Combined Loading ◽  
Offshore Platforms ◽  
Tubular Structures ◽  
Stress Concentrations ◽  
Standard Samples ◽  
T Joints ◽  
Modeling And Analysis

Steel tubular structures are widely used in the construction of offshore platforms and T-type junctions are extensively used in this domain. The tubular members are welded, which generates significant stress concentrations at the edges. The stress levels reached in these critical places are used to assess lifetimes based on fatigue curves from tests conducted on standard samples. This study is devoted to the modeling and analysis of T-type welded tubular structures for the determination of hot spots stresses (HSS) at the chord/brace intersection, A numerical analysis was carried out to study the effect of a combined loading composed of an axial loading and a continuation of rational bending, that best assimilate real conditions, as well as the effect of normalized geometric parameters α, β, g on the distribution of stress concentration (area and values) of T-joints. The mechanical behaviour has been modeled in 2D using quadrangular and triangular thin-shell elements by the finite element method (FEM). It is the most appropriate approach because it considers all geometric complexities and singularities of the structure, while the efforts as well as the computation time are considerably reduced compared to an experimental study or to complex FE models implementing solid elements. In this study, we use the COMSOL-MULTIPHYSICS® software...

Fatigue of Tubular Joints: Hot Spot Stress Method Revisited

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Pingsha Dong ◽  
Jeong K. Hong
Keyword(s):  
Hot Spot ◽  
Life Assessment ◽  
Structural Stress ◽  
T Joints ◽  
Hot Spot Stress ◽  
Tubular Joints ◽  
Fatigue Design ◽  
Fatigue Data ◽  
Section Viii ◽  
Remaining Life Assessment

A series of well-known tubular joints tested in UKSORP II have been re-evaluated using the mesh-insensitive structural stress method as a part of the on-going Battelle Structural Stress JIP efforts. In this report, the structural stress based analysis procedure is first presented for applications in tubular joints varying from simple T joints, double T Joints, YT joints with overlap, and K joints with various internal stiffening configurations. The structural stress based SCFs are then compared with those obtained using traditional surface extrapolation based hot spot stress methods. Their abilities in effectively correlating the fatigue data collected from these tubular joints are demonstrated. These tests are also compared with the T curve typically used for fatigue design of tubular joints as well as the structural stress based master S-N curve adopted by ASME Section VIII Div 2. Finally, some of the implications on fracture mechanics based remaining life assessment for tubular joints are discussed in light of the results obtained in this investigation.

Fatigue Life Estimation of Pitted Specimens by Means of an Integrated Fracture Mechanics Approach

2016 ◽  
Author(s):  
Nicolas O. Larrosa ◽  
Mirco D. Chapetti ◽  
Robert A. Ainsworth
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Crack Length ◽  
Driving Force ◽  
Hot Spot ◽  
Fatigue Cracks ◽  
Stress Concentrations ◽  
Engineering Structures ◽  
Premature Failure ◽  
Critical Crack Length

The synergistic nature of corrosion and fatigue is one of the main reasons for the premature failure of engineering structures and components. The decrease in fatigue life of specimens subjected to aggressive environments is likely to be attributed to local, pit-induced, stress concentrations that cause premature initiation of fatigue cracks. In this work, we have developed a predictive approach to assess the life of specimens containing pits assuming the pit both as a crack and as a smooth notch. The proposed approach assumes that even though the critical place for crack initiation seems to be the pit mouth, once the crack initiates, during propagation, the location of the hot spot shifts according to the location of the crack tip and due to the redistribution of stresses and strains. An integrated fracture mechanics approach that compares the driving force of the crack emanating from the pit and the evolution of the material threshold to crack propagation with crack length is proposed. The material threshold is estimated from the plain fatigue endurance limit, the position d of the strongest microstructural barrier and the SIF threshold for long cracks. The effective driving force is assessed by means of parametric FEA. This approach considers the influence of the pit geometry on the stress field surrounding the crack providing a more realistic estimate of the applied driving force. The maximum applied stress range as a function of number of cycles (S-N curves) have been estimated for different configurations (stress level, initial crack length, location at the crack front) assuming that failure of the component will be given when the critical crack length is reached. The procedure has been first developed and used to assess deep pits, as these are the most detrimental and common configuration encountered in real Oil and Gas applications.

Numerical Modeling of the Failure of Magnesium Tubes Under Compressive Loading

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Jonathan Rossiter ◽  
Kaan Inal ◽  
Raja Mishra
Keyword(s):  
Wall Thickness ◽  
Failure Criterion ◽  
Failure Modes ◽  
Compressive Loading ◽  
Three Dimensional ◽  
Material Model ◽  
Fe Model ◽  
Macroscopic Strain ◽  
Compression Tests ◽  
Stress Concentrations

A new finite element (FE) specific failure criterion utilizing hardening rates to quantify bending stress is implemented into the MAT_124 material model in the commercial software LS-DYNA to simulate fracture of extruded AZ31 and cast AM60 magnesium alloy tubes. The simulations are performed by requiring element erosion of hexahedral solid elements in a three-dimensional (3D) FE model when the failure criterion is satisfied at any point in the simulation. Experimental stress–strain curves from tensile and compression tests of the materials are used as inputs in the model. The simulations reproduce the measured load displacement data as well as general features of the experimental failure modes of round and rectangular tubes undergoing axial crush tests. The model is applied to investigate the effects of a variety of design features, such as varying tube wall thickness, preformed bulges, alternate bands of Al and Mg alloys, and cladding Al on magnesium, on the macroscopic strain to failure. The results show that adding multiple preformed bulges to the tubes can increase the strain to failure and reduce the force required to cause deformation. Adding a single bulge concentrates the strain causing reduced macroscopic strain to failure. Placing sections of reduced wall thickness or brazing in sections of aluminum causes stress concentrations which reduce the macroscopic strain to failure. Cladding aluminum onto the outside of the magnesium tube is shown to improve strain to failure.

3D Numerical Simulation and Fatigue Life Prediction of High Strength Threaded Bolt

2009 ◽  
Vol 417-418 ◽  
pp. 885-888 ◽  
Author(s):  
Li Bin Zhao ◽  
Feng Rui Liu ◽  
Jian Yu Zhang
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Three Dimensional ◽  
High Strength ◽  
General Purpose ◽  
Fatigue Life Prediction ◽  
Fe Model ◽  
3D Numerical Simulation ◽  
Threaded Connection ◽  
Bolt Connection

An three-dimensional FE model of threaded connection is proposed by means of the general purpose program ANSYS. The model is accurately constructed according to the helical thread profiles. The mechanical behavior of each bolt subjected to eccentrically loading is investigated and the stress distribution is discussed detailedly. Based on the stress level, the fatigue life of threaded connection is predicted by the cumulative damage method. This work can provide a deeply understanding on the mechanics behavior of bolt connection in engineering, especially for its application on the appending equipments of airplane.

Fatigue of Tubular Joints: Hot Spot Stress Method Revisited

2008 ◽  
Author(s):  
Pingsha Dong ◽  
Jeong K. Hong
Keyword(s):  
Hot Spot ◽  
Life Assessment ◽  
Structural Stress ◽  
T Joints ◽  
Hot Spot Stress ◽  
Tubular Joints ◽  
Fatigue Design ◽  
Fatigue Data ◽  
Section Viii ◽  
Remaining Life Assessment

A series of well-known tubular joints tested in UKSORP II have been re-evaluated using the mesh-insensitive structural stress method as a part of the on-going Battelle Structural Stress JIP efforts. In this report, the structural stress based analysis procedure is first presented for applications in tubular joints varying from simple T joints, double T Joints, YT joints with overlap and K joints with various internal stiffening configurations. The structural stress based SCFs are then compared with those obtained using traditional surface extrapolation based hot spot stress methods. Their abilities in effectively correlating the fatigue data collected from these tubular joints are demonstrated. These tests are also compared with the T curve typically used for fatigue design of tubular joints as well as the structural stress based master S-N curve adopted by ASME Section VIII Div 2. Finally, some of the implications on fracture mechanics based remaining life assessment for tubular joints are discussed in light of the results obtained in this investigation.

Structural and Thermal Analyses of Pressure Vessel Bottom Head With Penetration Holes

2005 ◽  
Author(s):  
David W. Wu ◽  
Raymond K. Yee
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Thermal Analyses ◽  
Three Dimensional ◽  
Fe Model ◽  
Stress Distributions ◽  
Pressure Loading ◽  
Stress Concentrations ◽  
Control Rod ◽  
Vessel Bottom

The paper presents a three-dimensional (3-D) finite element (FE) model of a nuclear pressure vessel and the analyses results under typical loadings using ANSYS finite element code. Structural analyses of the vessel with internal pressure loading and thermal transient loading are described. The main focus of the analysis is on the bottom head shell with the Control Rod Drive (CRD) penetration holes. The vessel support skirt and selected CRD housing/welds that attached to the bottom head shell are included in the model. The objective of this study is to assess the bottom head stress distributions of a nuclear pressure vessel, especially the stress concentrations due to the CRD penetration openings. The calculated stresses around uphill oblique holes in the vessel are compared with those around the normal facing center penetration hole. The preliminary results and conclusions drawn from the study are presented in the paper.

Effective Convergence Checks for Verifying Finite Element Stresses at Three-Dimensional Stress Concentrations

2018 ◽  
Vol 3 (3) ◽  
Author(s):  
J. R. Beisheim ◽  
G. B. Sinclair ◽  
P. J. Roache
Keyword(s):  
Finite Element ◽  
Error Estimation ◽  
A Posteriori Error Estimates ◽  
Three Dimensional ◽  
Posteriori Error ◽  
Test Problems ◽  
A Posteriori ◽  
Stress Concentrations ◽  
Element Analysis ◽  
A Posteriori Error

Current computational capabilities facilitate the application of finite element analysis (FEA) to three-dimensional geometries to determine peak stresses. The three-dimensional stress concentrations so quantified are useful in practice provided the discretization error attending their determination with finite elements has been sufficiently controlled. Here, we provide some convergence checks and companion a posteriori error estimates that can be used to verify such three-dimensional FEA, and thus enable engineers to control discretization errors. These checks are designed to promote conservative error estimation. They are applied to twelve three-dimensional test problems that have exact solutions for their peak stresses. Error levels in the FEA of these peak stresses are classified in accordance with: 1–5%, satisfactory; 1/5–1%, good; and <1/5%, excellent. The present convergence checks result in 111 error assessments for the test problems. For these 111, errors are assessed as being at the same level as true exact errors on 99 occasions, one level worse for the other 12. Hence, stress error estimation that is largely reasonably accurate (89%), and otherwise modestly conservative (11%).

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