Strengthening of wide-flange columns under load

1990 ◽  
Vol 17 (5) ◽  
pp. 835-843 ◽  
Author(s):  
H. Marzouk ◽  
S. Mohan
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Critical Load ◽  
Closed Form Solution ◽  
Welding Process ◽  
Form Solution ◽  
Element Analysis ◽  
Welding Stress ◽  
Existing Structures ◽  
Welding Sequence

The present work deals with formulation of theoretical and analytical methods leading to the development of column strength curves. The formulations were developed for both elastic and inelastic behaviour. Two types of reinforcement have been developed for strengthening the W-shape columns under load. Since the column strength curves are based in part on the magnitude and distribution of residual stresses, it is extremely important to consider the new pattern of residual stresses due to welding process. Also, the welding sequence will affect the magnitude and distribution of residual stresses. Theoretical formulations leading to a closed-form solution for the prediction of critical load were developed for two types of strengthening using the superposition of original residual, new welding, and initial loading stresses. A nonlinear finite element analysis based on the large deformation theory of stability was used to predict the strengthened column critical load. It takes into consideration the effect of cooling residual stresses and new welding residual stresses. The formulations were incorporated with gradual penetration of yielding, the spreading of inelastic zones along the member length, the presence of residual stresses, and strain hardening of the material. Experiments were carried out to determine the actual capacity of strengthened columns. Seven specimens were tested using two and four strengthening plates. The welding stresses were measured through a series of experiments, and it was found that the parabolic distribution is a very close approximation to the actual new welding stress distribution. Key words: reinforcement of steel columns, welding stresses, welding sequence, strengthening of existing structures, buckling, steel plating, finite element.

Analytical and Numerical Studies of a Thick Anisotropic Multilayered Fiber-Reinforced Composite Pressure Vessel

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Isaiah Ramos ◽  
Young Ho Park ◽  
Jordan Ulibarri-Sanchez
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Structural Damage ◽  
Three Dimensional ◽  
Closed Form Solution ◽  
Form Solution ◽  
Fiber Reinforced ◽  
Element Analysis ◽  
Analytical Results ◽  
Composite Pressure Vessel

In this paper, we developed an exact analytical 3D elasticity solution to investigate mechanical behavior of a thick multilayered anisotropic fiber-reinforced pressure vessel subjected to multiple mechanical loadings. This closed-form solution was implemented in a computer program, and analytical results were compared to finite element analysis (FEA) calculations. In order to predict through-thickness stresses accurately, three-dimensional finite element meshes were used in the FEA since shell meshes can only be used to predict in-plane strength. Three-dimensional FEA results are in excellent agreement with the analytical results. Finally, using the proposed analytical approach, we evaluated structural damage and failure conditions of the composite pressure vessel using the Tsai–Wu failure criteria and predicted a maximum burst pressure.

Validation of Nitinol SMA Characteristics Using Finite Element Analysis and Closed Form Solutions

2013 ◽  
Vol 856 ◽  
pp. 147-152
Author(s):  
S.H. Adarsh ◽  
U.S. Mallikarjun
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Closed Form ◽  
Closed Form Solution ◽  
Form Solution ◽  
Fe Analysis ◽  
Element Analysis ◽  
Complex Behaviour ◽  
Closed Form Solutions

Shape Memory Alloys (SMA) are promising materials for actuation in space applications, because of the relatively large deformations and forces that they offer. However, their complex behaviour and interaction of several physical domains (electrical, thermal and mechanical), the study of SMA behaviour is a challenging field. Present work aims at correlating the Finite Element (FE) analysis of SMA with closed form solutions and experimental data. Though sufficient literature is available on closed form solution of SMA, not much detail is available on the Finite element Analysis. In the present work an attempt is made for characterization of SMA through solving the governing equations by established closed form solution, and finally correlating FE results with these data. Extensive experiments were conducted on 0.3mm diameter NiTinol SMA wire at various temperatures and stress conditions and these results were compared with FE analysis conducted using MSC.Marc. A comparison of results from finite element analysis with the experimental data exhibits fairly good agreement.

Estimation of Residual Stresses in Steel Welded Joints Using Three Dimensional Finite Element Analysis

2018 ◽  
Author(s):  
Shivdayal Patel ◽  
B. P. Patel ◽  
Suhail Ahmad
Keyword(s):  
Residual Stress ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Residual Stresses ◽  
Boundary Conditions ◽  
Welding Speed ◽  
Welded Joints ◽  
Plate Thickness ◽  
Welding Process ◽  
Element Analysis

Welding is one of the most used joining methods in the ship industry. However, residual stresses are induced in the welded joints due to the rapid heating and cooling leading to inhomogenously distributed dimensional changes and non-uniform plastic and thermal strains. A number of factors, such as welding speed, boundary conditions, weld geometry, weld thickness, welding current/voltage, number of weld passes, pre-/post-heating etc, influence the residual stress distribution. The main aim of this work is to estimate the residual stresses in welded joints through finite element analysis and to investigate the effects of boundary conditions, welding speed and plate thickness on through the thickness/surface distributions of residual stresses. The welding process is simulated using 3D Finite element model in ABAQUS FE software in two steps: 1. Transient thermal analysis and 2. Quasi-static thermo-elasto-plastic analysis. The normal residual stresses along and across the weld in the weld tow region are found to be significant with nonlinear distribution. The residual stresses increase with the increase in the thickness of the plates being welded. The nature of the normal residual stress along the weld is found to be tensile-compressive-tensile and the nature of normal residual stress across the weld is found to be tensile along the thickness direction.

Using Isochronous Method to Calculate Creep Damage in Pressure Vessel Components: Part 2

2017 ◽  
Author(s):  
Chithranjan Nadarajah ◽  
Benjamin F. Hantz ◽  
Sujay Krishnamurthy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pressure Vessel ◽  
Closed Form Solution ◽  
Creep Damage ◽  
Form Solution ◽  
Creep Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Good Agreement

This paper is Part 2 of two papers illustrating how isochronous stress strain curves can be used to calculate creep stresses and damage for pressure vessel components. Part 1 [1], illustrated the use of isochronous stress strain curves to obtain creep stresses and damages on two simple example problems which were solved using closed form solution. In Part 2, the isochronous method is implemented in finite element analysis to determine creep stresses and damages on pressure vessel components. Various different pressure vessel components are studied using this method and the results obtained using this method is compared time explicit Omega creep model. The results obtained from the isochronous method is found to be in good agreement with the time explicit Omega creep model.

Finite Element Analysis Used to Optimize Welding Patterns for Marine Structure

1998 ◽  
Author(s):  
Dmitry Ischenko ◽  
Raafat Ibrahim
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Welding Process ◽  
Element Analysis ◽  
Gusset Plate ◽  
Transient Problem ◽  
Element Simulation ◽  
Marine Structure ◽  
Solid Plate ◽  
Nonlinear Transient

Abstract The development of optimum welding patterns which can reduce the adverse effects of welding is important for industry, and particularly, for shipbuilding. In this investigation, a finite element simulation was employed in order to optimize the design of the weldment and reduce residual stresses and distortions. A gusset plate, which was used to increase the stiffness of marine structures, was subjected to thermal loads to simulate the effect of the welding process. Temperature distributions were obtained as a solution of the nonlinear transient problem of thermal conductivity. These distributions were then used to calculate residual stresses and distortion by solving thermo-elastic-plastic problems. The results indicated a significant reduction in the distortion when a plate with circular slots and interrupted welding was used instead of a continuously welded solid plate.

Prediction of Welding Residual Stresses, Crack Initiation and Creep Crack Driving Forces C(t) Within a Continuous Finite Element Solution

2010 ◽  
Author(s):  
D. P. Bray ◽  
R. J. Dennis ◽  
M. C. Smith
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Driving Forces ◽  
Welding Process ◽  
Creep Damage ◽  
Operating Conditions ◽  
Finite Element Solution ◽  
Element Solution ◽  
Element Analysis ◽  
Creep Crack

The work reported in this paper investigates the manufacture, through-life operation and cracked behaviour of an attachment weld in a UK AGR boiler. A structural assessment of the attachment weld was performed to demonstrate its integrity. This assessment made use of complex finite element analysis of both the welding process and postulated defects. A simulation of the welding process was performed in order to predict the residual stresses and hardened material state throughout the attachment weld. The welding simulation was performed in two stages since a butter weld was deposited prior to the attachment weld itself. The accumulation of creep damage was predicted during steady normal operating conditions for the lifetime of the component. A contour map of creep damage was used to postulate the location and size of hypothetical single and double edge surface cracks within the weld. These postulated cracks were then explicitly introduced into the finite element model. The crack tip stress parameter C(t) was evaluated in order to predict the creep crack driving forces. The results from a cracked body simulation suggested that the creep crack driving force C(t) reduces as the crack grows, due to relief of the dominant welding residual stresses. The residual stress, creep damage and cracked body simulations have been brought together into a novel continuous finite element solution. The results can be used to support a safety case for continued operation of existing plant.

scholarly journals Effect of applied load on welding stress at different time periods

2018 ◽  
Vol 224 ◽  
pp. 01069
Author(s):  
Yanhu Wang ◽  
Sergey Konovalov ◽  
Xizhang Chen ◽  
Irina Komissarova
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Applied Load ◽  
Welding Process ◽  
High Strength ◽  
Specific Pressure ◽  
Welding Stress ◽  
Time Periods ◽  
Simulation Results

In this study, pressure finite element welding simulations has been carried out. The welding model is a butt filled weld. The objective is to study the effect of pressure on welding stress of high strength steel at different time periods. From the study we can find that no matter at the first half of welding or and the last half welding or at the cooling time apply the load have little effect to improve the stress. Only under the entire welding process that the distribution of residual stress can be greatly improved. The results show that the residual stresses of the welding workpiece under specific pressure throughout the welding process decreased by 16.2% when compared with weld group without load applied. The maximum residual stresses of weld group without load applied are more than with the specific pressure load plates 120 MPa. But under other times putting the load cannot be improved. This paper just presents a simulation results that have a certain guiding significance.

Numerical Study of Welding with Trailing Heat Sink Considering Phase Transformation Effects

2014 ◽  
Vol 875-877 ◽  
pp. 2118-2122
Author(s):  
Shirish R. Kala ◽  
N. Siva Prasad ◽  
G. Phanikumar
Keyword(s):  
Finite Element ◽  
Phase Transformation ◽  
Residual Stresses ◽  
Material Properties ◽  
Heat Sink ◽  
Numerical Study ◽  
Gaussian Model ◽  
Welding Process ◽  
Source Model ◽  
Element Analysis

Welding process with trailing heat sink for 2 mm mild steel plates has been analyzed to estimate distortion and residual stresses using a finite element modeling software Sysweld. The material properties used for the analysis are both temperature dependent and phase dependent. A transient thermal analysis is carried out using Goldak double ellipsoidal heat source model and heat sink as Gaussian model with negative heat flux. The finite element analysis (FEA) is conducted by considering the material properties of all phases of steel as well as without phase transformation i.e. by considering properties of only ferrite phase. Temperature distribution, distortion and residual stresses are calculated and compared for four cases: without phase without cooling, without phase with cooling, with phase without cooling and with phase with cooling. It is found that FEA without phase transformation effects overestimates the residual stresses in the fusion zone (FZ) and heat affected zone (HAZ). It is also found that a trailing heat sink reduces transverse compressive residual stresses thus minimizing the possibilities of buckling.

Influence of Welding Conditions on Residual Stresses of Multi-Pass Tube Sheet Welds

2012 ◽  
Vol 525-526 ◽  
pp. 349-352
Author(s):  
Hong Li ◽  
Yong Zheng ◽  
Li Li
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Tube Sheet ◽  
Element Analysis ◽  
Time Dynamic ◽  
Welding Sequence ◽  
Welding Line

Residual stresses and residual plastic strains of the welded structures are the products of nonlinear behaviors during welding. The residual stresses will cause errors during the assembly of the structure and injure the beauty of appearance of the structure. Based on an elastic-plastic-model, finite element numerical simulation of a representative tube sheet penetration assembly with loop welding line joined by multi-pass welding is carried out and the influence of welding conditions on residual stresses of the tube sheet welds is studied in this paper. Nonlinear three dimensional transient temperature fields and real-time dynamic stresses field are analyzed by FEM. The heat source is modeled as a moving heat flux following a double ellipsoid distribution and the temperature-dependent properties of materials are considered. The method of birth and death of element in finite element analysis is applied to simulate the gradual growth of weld pass metal. It is shown that welding sequence, size of groove welding and weld toes dressing will obviously change the magnitude of the residual stresses of tube sheet welds.

A New Analytical Method for Calculating Maximum Junction Temperature of Packaged Devices Incorporating the Temperature Distribution at the Base of the Substrate

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
J. H. L. Ling ◽  
A. A. O. Tay
Keyword(s):  
Finite Element ◽  
Temperature Distribution ◽  
Analytical Method ◽  
Analytical Methods ◽  
Thermal Analyses ◽  
Closed Form Solution ◽  
Form Solution ◽  
Junction Temperature ◽  
Uniform Temperature ◽  
Element Analysis

All current analytical methods for calculating junction temperature of field effect transistor (FET) and monolithic microwave integrated circuits (MMIC) devices have assumed a constant uniform temperature at the base of the substrate. In a packaged device, however, where the substrate is attached to a carrier, finite element thermal analyses have shown that the temperature distribution along the base of the substrate is not uniform but has a bell-shaped distribution. Consequently, current analytical methods which attempt to predict the junction temperature of a packaged MMIC device by assuming a constant uniform temperature at the base of the substrate have been found to be inaccurate. In this paper, it is found that the temperature distribution along the base of a substrate can be well approximated by a Lorentz distribution which can be determined from a few basic parameters of the device such as the gate length, gate pitch, number of gates, and length of substrate. By incorporating this Lorentz temperature distribution at the base of the substrate with a new closed-form solution for the three-dimensional temperature distribution within the substrate, a new analytical method is developed for accurately calculating the junction temperature of MMIC devices. The accuracy of this new method has been verified with junction temperatures of MMIC devices measured using thermoreflectance thermography (TRT) as well as those calculated using finite element analysis (FEA).

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