Numerical Modeling and Initial Fatigue Life Estimations of Welded Structural Components

2014 ◽  
Vol 1029 ◽  
pp. 124-129
Author(s):  
Ivana Vasovic ◽  
Marko Ristic ◽  
Slavica Ristic ◽  
Mirko Maksimovic ◽  
Dragi Stamenkovic
Keyword(s):  
Finite Element ◽  
Temperature Distribution ◽  
Residual Stresses ◽  
Numerical Simulations ◽  
Axial Direction ◽  
Element Model ◽  
Mechanical Analysis ◽  
Welding Simulation ◽  
Critical Areas ◽  
Good Agreement

Numerical simulations are powerful tool for analyzing and research in domain of mechanical constructions. In welded joints is very important to determine residual stresses and temperature distribution in sample, apropos, element of construction. In some cases doing the experiment is not possible, so numerical simulations can give the required results and overview of stress state, residual stresses, critical areas, displacement, temperature distribution and other data is needed for analyzing and improvement of constructions or parts of constructions. This analysis includes finite element model for the thermal and mechanical welding simulation. Welding simulation was considered as a sequential coupled thermo-mechanical analysis. The residual stress distribution and magnitude in axial direction was obtained. The paper also shows the results obtained in a simultaneously test of a butt welded thin steel sheet specimen by conventional methods and thermography. Numerical methods are also used in order to predict the crack of specimen. The obtained results confirm that it is very useful to use thermography and Finite Element Method (FEM) for early diagnostics of the complex structures in the exploitation conditions. In this paper is obtained good agreement of results between experiment and Numerical simulations.

An assessment of the Sachs method for measuring residual stresses in cold worked fastener holes

1998 ◽  
Vol 33 (4) ◽  
pp. 263-274 ◽  
Author(s):  
D J Smith ◽  
C G C Poussard ◽  
M J Pavier
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Cold Working ◽  
Element Model ◽  
Fe Model ◽  
Working Process ◽  
Element Analysis ◽  
Near Surface ◽  
Cold Worked ◽  
Good Agreement

Measurements of residual stresses in 6 mm thick aluminium alloy 2024 plates containing 4 per cent cold worked fastener are made using the Sachs method. The measurements are made on discs extracted from the plates. The measured tangential residual stress distribution adjacent to the hole edge are found to be affected by the disc diameter. The measured residual stresses are also in good agreement with averaged through-thickness predictions of residual stresses from an axisymmetric finite element (FE) model of the cold working process. A finite element analysis is also conducted to simulate disc extraction and then the Sachs method. The measured FE residual stresses from the Sachs simulation are found to be in good agreement with the averaged through-thickness predicted residual stresses. The Sachs simulation was not able to reproduce the detailed near-surface residual stresses found from the finite element model of the cold working process.

scholarly journals Evaluation of Load-Bearing Performance of Existing Cast Steel Node

2017 ◽  
Vol 3 (2) ◽  
pp. 88-94
Author(s):  
Yusheng Su ◽  
Xinkui Li ◽  
Xiaoping Wu
Keyword(s):  
Finite Element ◽  
Numerical Simulations ◽  
Cast Steel ◽  
Field Tests ◽  
Element Model ◽  
Preliminary Evaluation ◽  
Stress Distributions ◽  
Load Bearing ◽  
Non Destructive ◽  
Good Agreement

This paper presents a preliminary evaluation of the load-bearing performance of an existing cast steel node in a constructed tennis stadium using numerical simulations and non-destructive field tests. Given the absolute stress values of the existing cast steel node were immeasurable, the accuracy of the numerical simulations were verified by comparing the stress increments derived from numerical simulations and non-destructive field tests. During the experiment, the existing cast steel node was loaded indirectly by moving the retractable roof to three different positions (i.e. closed, semi-opened and fully-opened configurations); thus, only the stress increments were recorded. Three simplified truss models and one solid finite-element model were developed to simulate the stress distributions with the corresponding roof positions. A comparison suggests that the stress increments simulated with the developed finite-element models were in good agreement with experimental results. Therefore, the simulated stress distributions can be used to judge the load-bearing performance of the existing cast steel node.

Numerical and Experimental Investigations on Temperature and Stress Distribution in Oxygen Cutting

2009 ◽  
Vol 25 (01) ◽  
pp. 14-20
Author(s):  
Zhou Bo ◽  
Liu Yujun ◽  
Ji Zhuoshang
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Element Model ◽  
Thermomechanical Behavior ◽  
Experimental Investigations ◽  
Interface Temperature ◽  
Element Analysis ◽  
Temperature Method ◽  
Good Agreement

Oxygen cutting is a reliable and efficient process in shipbuilding. This study applies thermal elastoplastic analysis, using finite element techniques, to analyze the thermomechanical behavior and evaluate the residual stresses in oxygen cutting. A model for the temperature distribution during cutting and stress distribution in the workpiece are presented. The presented finite element model is capable of predicting the interface temperature and stress distribution during cutting and their influences in the workpiece. A noncontact temperature method—infrared radiation (IR) was used for surface temperature measurement. The residual stresses at the surface of the workpiece were measured by impact-indentation measurement. The results of finite element analysis were compared with experimental results to confirm the accuracy of the method. The numerical results are in good agreement with the experimental ones.

Residual Stresses in Friction Stir Welded Tube-Tubesheet Joint

2014 ◽  
Author(s):  
Fadi A. Al-Badour ◽  
Nesar Merah ◽  
Abdelrahman Shuaib ◽  
Abdelaziz Bazoune
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Annealing Temperature ◽  
Element Model ◽  
Stress Distributions ◽  
Temperature Dependent ◽  
Friction Stir ◽  
Welded Tube ◽  
Joint Material ◽  
Good Agreement

In this paper, a 3-D thermo-mechanical finite element model (FEM) is developed to simulate the process of friction stir seal welding (FSSealW) of tube-tubesheet joint, using a commercial finite element (FE) package considering temperature dependent material properties. The model is used for the prediction of temperature and stress distributions, as well as the prediction of the residual stresses in the seal welded joint, including the expanded tube and surrounding ligaments. Validation of the model is achieved using experimental temperature measurements. The FEM results are found to be in good agreement with experimental ones. Temperatures of the joint material away from the processed zone are below the annealing temperature. The calculated residual stresses are found to be compressive and help to enhance the contact stress in the tube-tubesheet joint.

Analysis of Temperature Field of Nuclear Canned Pump and Thermal Deformation Calculation of the Shielded Can

2012 ◽  
Vol 588-589 ◽  
pp. 1862-1865
Author(s):  
Yue Jun An ◽  
Chun Ye Guo ◽  
Guo Ming Liu ◽  
Li Ping Xue
Keyword(s):  
Finite Element ◽  
Temperature Field ◽  
Temperature Distribution ◽  
Heat Source ◽  
Theoretical Basis ◽  
Thermal Deformation ◽  
Field Data ◽  
Axial Direction ◽  
Element Model ◽  
Canned Motor

In order to find out the reason for deformation,cracking and leakage of the shielded can of nuclear canned motor and put forward the solution,a finite element model of 2-pole and 8kW canned motor in temperature field was created. Assigned materials and boundary conditions to each component and calculated the temperature distribution of the canned motor by equivalent heat source load method and display the distribution visibly.By combining with the temperature field data,obtained the temperature characteristics of the shielded can and calculated the thermal deformation based on the maximum temperature.The result of analysis show that the temperatures of each component are different,shielded can’s temperature rise is not uniformly distributed along the circumferential direction and the degree of thermal deformation along axial direction is larger than that along radial direction.The conclusion of this paper is conducive to understand the temperature distribution in canned motor and characteristics of thermal deformation in shielded can clearly,and provides an important theoretical basis for the development of new shielded can structure.

scholarly journals Stator Non-Uniform Radial Ventilation Design Methodology for a 15 MW Turbo-Synchronous Generator Based on Single Ventilation Duct Subsystem

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2760
Author(s):  
Ruiye Li ◽  
Peng Cheng ◽  
Hai Lan ◽  
Weili Li ◽  
David Gerada ◽  
...  
Keyword(s):  
Finite Element ◽  
Temperature Distribution ◽  
Design Methodology ◽  
Large Scale ◽  
Synchronous Generator ◽  
Axial Direction ◽  
Scale Model ◽  
Element Analysis ◽  
Axial Temperature ◽  
Ventilation Duct

Within large turboalternators, the excessive local temperatures and spatially distributed temperature differences can accelerate the deterioration of electrical insulation as well as lead to deformation of components, which may cause major machine malfunctions. In order to homogenise the stator axial temperature distribution whilst reducing the maximum stator temperature, this paper presents a novel non-uniform radial ventilation ducts design methodology. To reduce the huge computational costs resulting from the large-scale model, the stator is decomposed into several single ventilation duct subsystems (SVDSs) along the axial direction, with each SVDS connected in series with the medium of the air gap flow rate. The calculation of electromagnetic and thermal performances within SVDS are completed by finite element method (FEM) and computational fluid dynamics (CFD), respectively. To improve the optimization efficiency, the radial basis function neural network (RBFNN) model is employed to approximate the finite element analysis, while the novel isometric sampling method (ISM) is designed to trade off the cost and accuracy of the process. It is found that the proposed methodology can provide optimal design schemes of SVDS with uniform axial temperature distribution, and the needed computation cost is markedly reduced. Finally, results based on a 15 MW turboalternator show that the peak temperature can be reduced by 7.3 ∘C (6.4%). The proposed methodology can be applied for the design and optimisation of electromagnetic-thermal coupling of other electrical machines with long axial dimensions.

scholarly journals Numerical aspects for efficient welding computational mechanics

2014 ◽  
Vol 18 (suppl.1) ◽  
pp. 139-148
Author(s):  
Tarek Aburuga ◽  
Aleksandar Sedmak ◽  
Zoran Radakovic
Keyword(s):  
Residual Stresses ◽  
Three Dimensional ◽  
Shell Element ◽  
Element Model ◽  
Mechanical Analysis ◽  
Tensile Test Specimen ◽  
Integrity Assessment ◽  
Mass Scaling ◽  
Three Dimensional Models ◽  
Thermal Mechanical Analysis

The effect of the residual stresses and strains is one of the most important parameter in the structure integrity assessment. A finite element model is constructed in order to simulate the multi passes mismatched submerged arc welding SAW which used in the welded tensile test specimen. Sequentially coupled thermal mechanical analysis is done by using ABAQUS software for calculating the residual stresses and distortion due to welding. In this work, three main issues were studied in order to reduce the time consuming during welding simulation which is the major problem in the computational welding mechanics (CWM). The first issue is dimensionality of the problem. Both two- and three-dimensional models are constructed for the same analysis type, shell element for two dimension simulation shows good performance comparing with brick element. The conventional method to calculate residual stress is by using implicit scheme that because of the welding and cooling time is relatively high. In this work, the author shows that it could use the explicit scheme with the mass scaling technique, and time consuming during the analysis will be reduced very efficiently. By using this new technique, it will be possible to simulate relatively large three dimensional structures.

Physical and Numerical Simulations of the Seismic Response of a 1,100 kV Power Transformer Bushing

2018 ◽  
Vol 34 (3) ◽  
pp. 1515-1541 ◽  
Author(s):  
Guo-Liang Ma ◽  
Qiang Xie ◽  
Andrew S. Whittaker
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Numerical Simulations ◽  
Seismic Vulnerability ◽  
Power Transformer ◽  
Element Model ◽  
Ground Shaking ◽  
Earthquake Simulator ◽  
Physical Experiments ◽  
Seismic Tests

Power transformers and bushings are key pieces of substation equipment and are vulnerable to the effects of earthquake shaking. The seismic performance of a 1,100 kV bushing, used in an ultra-high voltage (UHV) power transformer, is studied using a combination of physical and numerical experiments. The physical experiments utilized an earthquake simulator and included system identification and seismic tests. Modal frequencies and shapes are derived from white noise tests. Acceleration, strain, and displacement responses are obtained from the uniaxial horizontal seismic tests. A finite element model of the 1,100 kV bushing is developed and analyzed, and predicted and measured results are compared. There is reasonably good agreement between predicted and measured responses, enabling the finite element model to be used with confidence for seismic vulnerability studies of transformer-bushing systems. A coupling of the experimental and numerical simulations enabled the vertically installed UHV bushing to be seismically qualified for three-component ground shaking with a horizontal zero-period acceleration of 0.53 g.

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