A Comparative Study of Three Different Approaches of FE Analysis for Prediction of Welding Distortion of Orthogonally Stiffened Plate Panels

2009 ◽  
Vol 25 (04) ◽  
pp. 191-197
Author(s):  
Pankaj Biswas ◽  
N. R. Mandal
Keyword(s):  
Plate Thickness ◽  
Thermomechanical Analysis ◽  
Fe Analysis ◽  
Computational Time ◽  
Welding Distortion ◽  
Welding Parameters ◽  
Stiffened Plate ◽  
Welding Sequence ◽  
Structural Assembly ◽  
Inherent Strain Method

One of the most disturbing aspects in structural assembly is welding distortion. These deformations adversely affect the subsequent fit-up and alignment of the adjacent panels. The extent of distortion depends on welding parameters, plate thickness, thermophysical properties of plate material, structural restraints, and welding sequence. Because welding is a fully transient phenomenon, its numerical analysis is highly time consuming, and hence analysis of full-size ship structural panels is simply not feasible using conventional finite element (FE) analysis. The computational time depends on number of elements, type of analysis, number of load steps, and computer configuration. Actual simulation of welding, that is, transient elastoplastic thermomechanical analysis is computationally highly time consumable. In the present study, two different modeling approaches for welding distortion prediction are presented that show a drastic reduction in computational time. Finally, comparative studies are made among the transient elastoplastic thermomechanical analysis and two different equivalent techniques, that is, inherent strain method and transient cooling phase analysis for prediction of welding distortions of a stiffened plate panel.

A Method to Define the Best Weld Sequence Using a Limited Number of Welding Simulation Analysis

2015 ◽  
Author(s):  
Mahyar Asadi ◽  
Ghazi Alsoruji
Keyword(s):  
Simulation Model ◽  
Surrogate Model ◽  
Simulation Analysis ◽  
Combinatorial Problem ◽  
Fem Analysis ◽  
Simulation Models ◽  
Computational Time ◽  
Optimal Sequence ◽  
Welded Structure ◽  
Welding Sequence

Weld sequence optimization, which is determining the best (and worst) welding sequence for welding work pieces, is a very common problem in welding design. The solution for such a combinatorial problem is limited by available resources. Although there are fast simulation models that support sequencing design, still it takes long because of many possible combinations, e.g. millions in a welded structure involving 10 passes. It is not feasible to choose the optimal sequence by evaluating all possible combinations, therefore this paper employs surrogate modeling that partially explores the design space and constructs an approximation model from some combinations of solutions of the expensive simulation model to mimic the behavior of the simulation model as closely as possible but at a much lower computational time and cost. This surrogate model, then, could be used to approximate the behavior of the other combinations and to find the best (and worst) sequence in terms of distortion. The technique is developed and tested on a simple panel structure with 4 weld passes, but essentially can be generalized to many weld passes. A comparison between the results of the surrogate model and the full transient FEM analysis all possible combinations shows the accuracy of the algorithm/model.

Cutting of a Longitudinally Stiffened Plate by a Wedge

1994 ◽  
Vol 38 (04) ◽  
pp. 340-348 ◽  
Author(s):  
Jeom Kee Paik
Keyword(s):  
Plate Thickness ◽  
Wedge Angle ◽  
Steel Plates ◽  
Test Results ◽  
Stiffened Plate ◽  
Absorbed Energy ◽  
Dimensionless Analysis ◽  
Cutting Length ◽  
Plate Aspect Ratio ◽  
Stiffened Steel

The aim of this study is to obtain test data for longitudinally stiffened steel plates which are quasistatically cut by a rigid wedge, idealizing the deck or bottom platings in ship collision or grounding, and also to derive an empirical formula relating the absorbed energy and cutting length. A series of tests for longitudinally stiffened high-tensile steel plates is conducted, varying several factors, namely plate thickness, plate aspect ratio, angle/shape of wedge tip and property of stiffeners. A total of 50 specimens with thicknesses in the range of 3.4 to 7.8 mm and wedge angles of 15, 30, 45, and 60 deg, including one unstiffened and two horizontally stiffened plate specimens, were tested. The importance of each parameter and its effect on the cutting response are investigated. By dimensionless analysis of the test results obtained here, the energy absorbed while a longitudinally stiffened plate is cut by a wedge is expressed as a function of cutting length, yield stress, equivalent plate thickness, and wedge angle. Incorporation of dynamic effects into the static formula is suggested. A comparison of the proposed solutions with the previous formulas or drop-hammer test results is made.

Prediction of Welding Deformation and Residual Stress in a Multiply-Stiffened Plate

2016 ◽  
Author(s):  
Min Guo ◽  
Zhen Chen ◽  
Yu Luo
Keyword(s):  
Residual Stress ◽  
Base Plate ◽  
Welding Parameters ◽  
Fe Model ◽  
Stiffened Plate ◽  
Local Distortion ◽  
Model Combining ◽  
Single Side ◽  
Welding Sequences ◽  
Welding Processes

In this paper, welding induced deformation and residual stress of a multiply-stiffened plate is studied by means of sequentially coupled thermal elasto-plastic finite element method. For the purpose of enhancing calculation efficiency, the FE model combining shell and solid elements is employed in the analysis. A transient moving heat source is used in the numerical analysis to consider important welding parameters such as heat input, welding speed and welding sequences. The welding processes of three stiffeners being attached to a base plate by single-side welds are simulated according to assembly configurations. The influence of three welding sequences and the position of weld foot on distortions and residual stress are discussed. The results demonstrate the different characteristics of residual distortion and stress in the multiply-stiffened plate by different welding sequences. The position of weld foot affects the local distortion of panel between two adjacent stiffeners.

RELIABILITY OF CORRODED STIFFENED PLATE SUBJECTED TO UNIAXIAL COMPRESSIVE LOADING

2021 ◽  
Vol 162 (A4) ◽  
Author(s):  
K Woloszyk ◽  
Y Garbatov
Keyword(s):  
Mechanical Properties ◽  
Reliability Index ◽  
Structural Reliability ◽  
Limit State ◽  
Plate Thickness ◽  
Thickness Reduction ◽  
Stiffened Plates ◽  
Stiffened Plate ◽  
Initial Imperfections ◽  
Subsequent Decrease

The work is focused on the reliability of corroded stiffened plates subjected to compressive uniaxial load based on the progressive collapse approach as stipulated by the Common Structural Rules for Bulk Carriers and Oil Tankers, employing the limit state design. Two different cases have been investigated. In the first model, the corrosion degradation led to uniform thickness loss, whereas the mechanical properties were unchanged, as given in the Rules. In the second model, the plate thickness degradation was followed by mechanical properties reduction. The uncertainties related to the mechanical properties, thicknesses, and initial imperfections of the corroded stiffened plate were taken into account. Several initial design solutions of stiffened plates, as well as different severity levels of corrosion degradation were investigated. The results show that structural reliability significantly decreases with corrosion development, especially when in addition to the initial imperfections and corrosion plate thickness reduction, corroded plate surface roughness and the changes in the mechanical properties were considered. The uncertainties, their origins and confidence levels are discussed. It was found that non-linear time-dependent corrosion degradation accounting not only for the thickness reduction due to corrosion wastage but also the subsequent decrease of mechanical properties lead to a significant reduction in the reliability index. Additionally, it was defined that the reliability estimate is very sensitive to the uncertainties related to the initial thickness and the spread of corrosion degradation as a function of the time. Incorporating the probability of corrosion detection into the original reliability model introduces additional information about the validity of structural degradation that may lead to a higher beta reliability index estimate compared to the original model.

Full-Scale Measurements of Welding-Induced Initial Deflections and Residual Stresses in Steel-Stiffened Plate Structures

2018 ◽  
Vol Vol 160 (A4) ◽  
Author(s):  
M S Yi ◽  
C M Hyun ◽  
J K Paik
Keyword(s):  
Residual Stresses ◽  
Ultimate Strength ◽  
Computational Models ◽  
Plate Thickness ◽  
Offshore Structures ◽  
Full Scale ◽  
Stiffened Plate ◽  
Plate Structures ◽  
Initial Imperfections ◽  
Numerical Predictions

Plated structures such as ships and offshore structures are constructed using welding techniques that attach support members (or stiffeners) to the plating. During this process, initial imperfections develop in the form of initial deformations (deflections or distortions) and residual stresses. These initial imperfections significantly affect the buckling and ultimate strength of these structures. Therefore, to assess the strength of welded plate structures, it is very important to predict the magnitude and pattern of welding-induced initial imperfections and their effects on buckling and ultimate strength. To determine the reliability of the prediction methods, it is desirable to validate the theoretical or numerical predictions of welding-induced initial imperfections through comparison with full-scale actual measurements. However, full-scale measurement databases are lacking, as they are costly to obtain. This study contributes to the development of a full-scale measurement database of welding-induced initial imperfections in steel-stiffened plate structures. The target structures are parts of real (full-scale) deckhouses in very large crude oil carrier class floating, production, storage and offloading unit structures. For parametric study purposes, four test structures by varying plate thickness are measured while the stiffener types and weld bead length are fixed. Modern technologies for measuring initial deformations and residual stresses are applied. The details of the measurement methods are documented for the use of other researchers and practicing engineers who want to validate their computational models for predicting welding-induced initial imperfections.

scholarly journals Modified Equivalent Load Method for Welding Distortion Analysis

2020 ◽  
Vol 8 (10) ◽  
pp. 794
Author(s):  
Jaemin Lee ◽  
Hyun Chung
Keyword(s):  
Shell Element ◽  
Angular Distortion ◽  
Computational Time ◽  
Welding Distortion ◽  
Distortion Analysis ◽  
Equivalent Load Method ◽  
Inherent Deformation ◽  
Longitudinal Bending ◽  
Equivalent Load ◽  
Improved Accuracy

In this study, modified equivalent load method for welding distortion analysis is suggested to improve its accuracy. To avoid the excessive computational time for welding distortion analysis of large welded structures, shell element-based elastic analysis methods are widely used, applying the inherent deformation approach. Equivalent nodal forces are commonly used in common FE (Finite Element) codes to enter these inherent deformation values. However, the conventional method cannot estimate precise longitudinal bending following the conventional equation. In this study, the problem of the existing equivalent load method is analyzed by a case study, and the modified equivalent load method that can estimate angular distortion, transverse shrinkage, and longitudinal bending is presented based on the FEM principle. The results show that by applying the proposed method, the shell element-based elastic FE approach for the welding distortion analysis can be achieved with improved accuracy.

A Parametric Approach for the Stress Analysis of Orthogonally Stiffened Rectangular Plates

1983 ◽  
Vol 105 (4) ◽  
pp. 363-368 ◽  
Author(s):  
R. J. Dohrmann ◽  
J. N. Wu ◽  
R. E. Beckett
Keyword(s):  
Stress Analysis ◽  
Orthotropic Plate ◽  
Plate Thickness ◽  
Normal Pressure ◽  
Rectangular Plates ◽  
Maximum Deflection ◽  
Stiffened Plate ◽  
Parametric Approach ◽  
Simply Supported ◽  
Plate Geometry

This report describes a parametric approach for the stress analysis of orthogonally stiffened rectangular plates. The analysis assumes that the deflection of an orthogonally stiffened plate is approximated by a homogeneous orthotropic plate of a uniform thickness. Polynomial expressions for maximum deflection for two sets of boundary conditions (all edges clamped and two edges clamped–two edges simply supported) are presented in terms of plate geometry and loading (normal pressure and in-plane forces). A method for computing the stress is presented that permits stresses in the actual orthogonally stiffened plate (that generally does not have a uniform plate thickness) to be determined.

scholarly journals The Effect of Welding-Pass Grouping on the Prediction Accuracy of Residual Stress in Multipass Butt Welding

2017 ◽  
Vol 2017 ◽  
pp. 1-13
Author(s):  
Jeongung Park ◽  
Gyubaek An ◽  
Sunghoon Kim
Keyword(s):  
Residual Stress ◽  
Diffraction Method ◽  
Fe Analysis ◽  
Computer Memory ◽  
Butt Weld ◽  
Butt Welding ◽  
Welded Structure ◽  
Welding Sequence ◽  
Grouping Method ◽  
Neutron Diffraction Method

The residual stress analysis of a thick welded structure requires a lot of time and computer memory, which are different from those in thin welded structure analysis. This study investigated the effect of residual stress due to welding-pass grouping as a way to reduce the analysis time in multipass thick butt welding joint. For this purpose, the parametric analysis which changes the number of grouping passes was conducted in the multipass butt weld of a structure with a thickness of 25 mm and 70 mm. In addition, the residual stress by thermal elastoplastic FE analysis is compared with the results by the neutron diffraction method for verifying the reliability of the FE analysis. The welding sequence is considered in order to predict the residual stress more accurately when using welding-pass grouping method. The results of the welding-pass grouping model and half model occurred between the results of the left/right of the full model. If the total number of welding-pass grouping is less than half of that of welding pass, a large difference with real residual stress is found. Therefore, the total number of the welding-pass grouping should not be reduced to more than half.

Effect of Welding Sequence on the Residual Stress Distribution in a Stiffened Plate

2016 ◽  
Author(s):  
Bai-Qiao Chen ◽  
C. Guedes Soares
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Lower Layer ◽  
Plate Thickness ◽  
Three Dimensional ◽  
Welding Process ◽  
Residual Stress Distribution ◽  
Steel Plates ◽  
Tension Zone ◽  
Welding Sequence

This work investigates the temperature distribution, deformation and residual stress in steel plates as a result of different sequences of welding. The single-pass gas tungsten arc welding process is simulated by a three dimensional nonlinear thermo-elasto-plastic approach. It is observed that the distribution of residual stress varies through the direction of plate thickness. It is concluded that the welding sequence affects not only the welding deformation but also the residual stress mainly in the lower layer of the plates. An in-depth discussion on the pattern of residual stress distribution is presented, especially on the width of the tension zone. Smaller residual tension zone and slightly lower compressive stress are found in thicker plate.

scholarly journals Computing Welding Distortion: Comparison of Different Industrially Applicable Methods

2005 ◽  
Vol 6-8 ◽  
pp. 195-202 ◽  
Author(s):  
D. Tikhomirov ◽  
Bert Rietman ◽  
K. Kose ◽  
M. Makkink
Keyword(s):  
Numerical Simulation ◽  
Development Stage ◽  
Welding Distortion ◽  
Welding Parameters ◽  
Automotive Part ◽  
Virtual Product

Welding distortion is one of the major concerns of the industrial joining practice. In order to obtain optimal welding parameters many experiments have to be carried out. Numerical simulation enables a virtual examination of the welding distortion without performing expensive experiments. In this contribution some industrially applicable methods of weld modeling are discussed. They enable the fast distortion assessment in the pre-development stage. The application of these methods on a complex automotive part is conducted followed by a comparison of computed distortion with measured values. Furthermore, aspects of integration of weld modeling into the virtual product chain are addressed.

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