Influence of Phase Transformations on Residual Stresses in Welded Structures

2013 ◽  
Author(s):  
R. J. Dennis ◽  
R. Kulka ◽  
O. Muransky ◽  
M. C. Smith
Keyword(s):  
Phase Transformation ◽  
Residual Stresses ◽  
Phase Transformations ◽  
Numerical Models ◽  
Material Model ◽  
Transformation Model ◽  
Austenitic Steels ◽  
Beam Specimen ◽  
Welded Structures ◽  
The Impact

A key aspect of any numerical simulation to predict welding induced residual stresses is the development and application of an appropriate material model. Often significant effort is expended characterising the thermal, physical and hardening properties including complex phenomena such as high temperature annealing. Consideration of these aspects is sufficient to produce a realistic prediction for austenitic steels, however ferritic steels are susceptible to solid state phase transformations when heated to high temperatures. On cooling a reverse transformation occurs, with an associated volume change at the isothermal transformation temperature. Although numerical models exist (e.g. Leblond) to predict the evolution of the metallurgical phases, accounting for volumetric changes, it remains a matter of debate as to the magnitude of the impact of phase transformations on residual stresses. Often phase transformations are neglected entirely. In this work a simple phase transformation model is applied to a range of welded structures with the specific aim of assessing the impact, or otherwise, of phase transformations on the magnitude and distribution of predicted residual stresses. The welded structures considered account for a range of geometries from a simple ferritic beam specimen to a thick section multi-pass weld. The outcome of this work is an improved understanding of the role of phase transformation on residual stresses and an appreciation of the circumstances in which it should be considered.

Finite Element Modelling and Measurements of Residual Stress and Phase Composition in Ferritic Welds

2010 ◽  
Author(s):  
Benjamin M. E. Pellereau ◽  
Christopher M. Gill ◽  
Matthew Dawson ◽  
Paul R. Hurrell ◽  
John Francis ◽  
...  
Keyword(s):  
Finite Element ◽  
Phase Transformation ◽  
Residual Stresses ◽  
Cyclic Hardening ◽  
Tig Welding ◽  
Transformation Model ◽  
Welding Parameters ◽  
Isotropic Hardening ◽  
Low Carbon ◽  
Fe Modelling

This paper describes finite element (FE) modelling and neutron diffraction (ND) measurements to investigate the development of residual stresses in two different geometries of ferritic weld. All specimens were produced using SA508 Grade 3 steel plates, depositing a low carbon SD3 weld filler by mechanised TIG welding. The FE analyses were carried out using Abaqus/VFT and the behaviour of the SA508 steel was modelled using a simplified (Leblond) phase transformation model with isotropic hardening using VFT’s UMAT-WELD subroutine, which includes the change in volume due to phase transformation. Single bead-on-plate specimens were manufactured using a range of mechanised TIG welding parameters. One pass and three pass groove welds were also produced, in order to investigate the cyclic hardening behaviour of the materials, as well as phase transformation effects in a multi-pass weld. FE analyses were then performed to determine how accurately these effects could be modelled. During manufacture, a number of thermocouples were attached to each of the specimens in order to calibrate the heat input to the FE models. The residual stresses in each of the bead on plate welds, as well as the groove weld after the first and the third passes, were then measured using ND at the middle of the plate. The ND measurements for the three pass weld showed no significant cyclic hardening behaviour although some was predicted by the FE analysis. Another key finding of the FE modelling that was seen in all of the models was that the phase transformation acts to reduce the stress levels in the deposited weld metal leaving the largest tensile stresses in a ring at the outer edge of the full heat affected zone (HAZ). There are plans to refine the FE studies using improved material properties when material testing of SA508 and SD3 are completed in the near future.

Simple Benchmark Problems for Finite Element Weld Residual Stress Simulation

2013 ◽  
Author(s):  
Mike C. Smith ◽  
Steve Bate ◽  
P. John Bouchard
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Phase Transformation ◽  
Solid State ◽  
Residual Stresses ◽  
Benchmark Problems ◽  
Transient Temperature ◽  
Beam Specimen ◽  
Weld Residual Stress ◽  
Solid State Phase Transformation

Finite element methods are used increasingly to predict weld residual stresses. This is a relatively complex use of the finite element method, and it is important that its practitioners are able to demonstrate their ability to produce accurate predictions. Extensively characterised benchmark problems are a vital tool in achieving this. However, existing benchmarks are relatively complex and not suitable for analysis by novice weld modellers. This paper describes two benchmarks based upon a simple beam specimen with a single autogenous weld bead laid along its top edge. This geometry may be analysed using either 3D or 2D FE models and employing either block-dumped or moving heat source techniques. The first, simpler, benchmark is manufactured from AISI 316 steel, which does not undergo solid state phase transformation, while the second, more complex, benchmark is manufactured from SA508 Cl 3 steel, which undergoes solid state phase transformation during welding. A number of such beams were manufactured using an automated TIG process, and instrumented with thermocouples and strain gauges to record the transient temperature and strain response during welding. The resulting residual stresses were measured using diverse techniques, and showed markedly different distributions in the austenitic and ferritic beams. The paper presents the information necessary to perform and validate finite element weld residual stress simulations in both the simple austenitic beam and the more complex ferritic beam, and provides performance measures for the austenitic beam problem.

Benchmark on Residual Stress Modeling in Fracture Mechanics Assessment

2013 ◽  
Author(s):  
S. Marie ◽  
H. Deschanels ◽  
S. Chapuliot ◽  
P. Le Delliou
Keyword(s):  
Crack Initiation ◽  
Residual Stresses ◽  
Best Practice ◽  
Numerical Models ◽  
Good Practice ◽  
Steel Pipes ◽  
Defect Assessment ◽  
Good Practice Guideline ◽  
Treatment Procedures ◽  
The Impact

In the frame of development in analytical defect assessment methods for the RSE-M and RCC-MRx codes, new work on the consideration of residual stresses is initiated by AREVA, CEA and EDF. The first step of this work is the realization of a database of F.E. reference cases. To validate assumptions and develop a good practice guideline for the consideration of residual stresses in finite element calculations, a benchmark between AREVA, CEA and EDF is going-on. A first application presented in this paper focuses on the analysis of the crack initiation of aged duplex stainless steel pipes submitted to an increasing pressure loading. Residual stresses are related to pipe fabrication process and act as shell bending condition. Two tests were performed: the first with an internal longitudinal semi-elliptical crack and the second with an external crack. The analysis first focuses on the ability to accurately estimate the measured pressure at the crack initiation of the two tests. For that purpose, the comparison of results obtained with different methods of taking into account the residual stresses (i.e. thermal fields or initial strain field). It then validates post-treatment procedures for J or G determination, and finally compares of the results obtained by the different partners. It is then shown that the numerical models can integrate properly the impact of residual stresses on the crack initiation pressure. Then, an excellent agreement is obtained between the different numerical evaluations of G provided by the participants to the benchmark so that best practice and reference F.E. solutions for residual stresses consideration can be provided based on that work.

scholarly journals Dynamic Response of a Single-Layer Reticulated Dome during Aircraft Impact Based on S-J Modeling Method

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Li Lin ◽  
Bo Huang ◽  
Yunhui Sun ◽  
Yu Zhu ◽  
Duozhi Wang
Keyword(s):  
Numerical Model ◽  
Temperature Effect ◽  
Failure Modes ◽  
Numerical Models ◽  
Material Model ◽  
Modeling Method ◽  
Dynamic Responses ◽  
Shell Structures ◽  
Large Strains ◽  
The Impact

In previous numerical models developed for the impact dynamic responses of reticulated domes, mostly BEAM 161 elements and piecewise linear plastic material model have been employed and spherical joints have been simplified as intersection points of beams, which is called the B-P method. The B-P method can be employed in studying the dynamic responses of reticulated shells under low- to moderate-speed impacts with no obvious temperature effect. However, the analysis of the dynamic responses of reticulated shells under moderate- and high-speed impacts of missiles and other aircraft using this method had errors because it could not take into account the temperature effect. To accurately describe the mechanical responses of reticulated shells under aircraft impacts, the Johnson–Cook material model considering temperature effect with corresponding SHELL 163 element was selected for determining the members of the numerical model and the shell element was used to establish the spherical joints of reticulated shells; the whole process was called the S-J modeling method. This modeling method was capable of considering the effects of high strain rates, high temperatures, large strains, stress state change, and loading history. S-J and B-P methods were used to model the reticulated shell structures. Comparing the numerical analysis results of the drop hammer impact of the two developed methods with experimental results verified the accuracy of the S-J modeling method. In addition, based on the results obtained from the S-J modeling method and LS-DYNA finite element analysis software, a numerical model was established for small aircraft impact reticulated shells and the failure modes and dynamic responses of reticulated shell structures under aircraft impacts were studied. In terms of energy analysis, it was found that the effects of roof plates, spherical joints, and temperature softening could not be ignored in such studies.

Numerical Simulation of Projectile Material Phase Transformation during Penetration

2014 ◽  
Vol 881-883 ◽  
pp. 1836-1841
Author(s):  
Jiang Bo Wang ◽  
Qing Ming Zhang ◽  
Gui Ying Xu ◽  
Cheng Liang Feng
Keyword(s):  
Numerical Simulation ◽  
Phase Transformation ◽  
High Temperature ◽  
Impact Velocity ◽  
Austenite Phase ◽  
Transformation Model ◽  
Transformation Zone ◽  
Head Surface ◽  
Critical Impact Velocity ◽  
The Impact

It was found from the experiment that the high temperature caused by target impact led to projectile austenite phase transformation. Based on this finding, a phase transformation model was established and verified by experiments, which proved the model had a relatively high calculation precision. Then, the model was used for numerical simulation. The result showed that the phase transformation zone was at the projectile head surface and the area increased as the impact velocity increased. The critical impact velocity which would cause phase transformation and affect projectile performance was around 700m/s.

Model of stress-induced phase transformation and prediction of internal stresses of large steel workpieces during quenching

2004 ◽  
Vol 120 ◽  
pp. 473-479
Author(s):  
W. Shi ◽  
X. Zhang ◽  
Z. Liu
Keyword(s):  
Phase Transformation ◽  
Residual Stresses ◽  
Phase Transformations ◽  
Hollow Cylinder ◽  
Turbine Rotor ◽  
Avrami Equation ◽  
Internal Stresses ◽  
Generator Rotor ◽  
Large Steel

Because internal stresses in large steel workpieces are high during quenching, the coupling of stresses and phase transformations should be considered to predict the internal stresses. The influence of stresses on phase transformations was investigated by dilatometer experiments applied uniaxial loads, modified John-Mehl-Avrami equation and Koistinen-Marburger equation were suggested to model the stress-phase transformation coupling during quenching. The model suggested was used in an in-house FEM code NSHT developed by authors. The distribution of residual stresses of a hollow cylinder specimen was calculated to investigate the stress-induced phase transformation. The internal stresses of a generator rotor during different quenching processes and stresses at the groove bottom of a turbine rotor in quenching were analyzed.

Development of Simplified Empirical Phase Transformation Model for Use in Welding Residual Stress Simulations

2014 ◽  
Author(s):  
Nicholas O’Meara ◽  
John A. Francis ◽  
Simon D. Smith ◽  
Philip J. Withers
Keyword(s):  
Thermal Expansion ◽  
Residual Stresses ◽  
Phase Transformations ◽  
Pressure Vessel ◽  
Welding Residual Stress ◽  
Transformation Model ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Fe Simulations ◽  
Wide Range

The level and distribution of residual stresses in welds arises from the complex thermo-mechanical history of heat flow and thermal expansion at very high temperatures. It is not possible to make assessments of these with the methods that are used to determine service stresses. Simulation techniques have been developed over many years making it increasingly possible to predict residual stresses. These models need accurate materials data including, where applicable, the effect of phase transformations. In nuclear reactor pressure vessel welds, it is necessary to consider welding as a metallurgical problem as well as a thermo-mechanical one and FE simulations of these require a wide range of material data in order to create suitable input parameters. It is crucial that models of ferritic steel welds simulate the effects of phase transformations because the different phases have different thermal expansion coefficients. Partly due to differences in thermal expansion coefficient attributed to the different phases, but more significantly because of the associated transformation strain and transformation plasticity. Further to this, predicting the distribution of the phase fractions enables structural simulations to account for the distribution of mechanical properties throughout a weld. In this work, a simplified approach to producing an empirical model to simulate phase transformations in SA-508 Gr3 pressure vessel steel is presented. A commercial finite element package is used to implement the model which calculates the volume fraction of bainite, martensite and austenite and the thermal strains that evolve over the thermal excursions. The results of these FE simulations are compared to experimental data.

scholarly journals EXTENSION OF A PHASE TRANSFORMATION MODEL FOR PARTIAL HARDENING IN HOT STAMPING

2018 ◽  
Vol 18 (3) ◽  
pp. 88-98 ◽  
Author(s):  
Thawin HART-RAWUNG ◽  
Johannes BUHL ◽  
Markus BAMBACH
Keyword(s):  
Phase Transformation ◽  
Hot Stamping ◽  
Material Model ◽  
Transformation Model ◽  
Austenitization Temperature ◽  
Materials Modelling ◽  
Data Points ◽  
Hot Stamping Steel ◽  
Dilatation Behaviour

The quality of predicted microstructural and mechanical properties in hot stamping simulations relies considerably on the material model. Many researchers studied the effect of the plastic deformation on the phase transformation of the most commonly used hot stamping steel 22MnB5, and proved that the deformation applied at high temperature promotes the formation of ferrite, pearlite and bainite. This behaviour has to be integrated into materials modelling. In this study, the effect of pre-strain on the phase transformation of the material is considered. The specimens are heated to austenitization temperature, isothermally deformed at 700 °C, and quenched down to room temperature. The phase fractions and the temperature-dilatation behaviour obtained from the experiments are used to calibrate the material model. By using the experimental data obtained from dilatometer testing, the accuracy of the material model is evaluated. Additionally, an attempt to predict the results between the tested data points by using interpolation was made and compared with the simulation results.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Sign in / Sign up

Export Citation Format

Share Document