scholarly journals Material model for simulating domain reorientation and phase transformation in triaxial loaded PZT95/5

2021 ◽  
Author(s):  
Wen Dong
Keyword(s):  
Phase Transformation ◽  
Material Model ◽  
Domain Reorientation

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.

scholarly journals Constitutive Modelling and Identification of Parameters of 316L Stainless Steel at Cryogenic Temperatures

2014 ◽  
Vol 8 (3) ◽  
pp. 136-140 ◽  
Author(s):  
Maciej Ryś
Keyword(s):  
Phase Transformation ◽  
Nonlinear Response ◽  
316L Stainless Steel ◽  
Parent Phase ◽  
Secondary Phase ◽  
Material Model ◽  
Transformation Process ◽  
Constitutive Modelling ◽  
Model Parameters ◽  
Two Phase

Abstract In this work, a macroscopic material model for simulation two distinct dissipative phenomena taking place in FCC metals and alloys at low temperatures: plasticity and phase transformation, is presented. Plastic yielding is the main phenomenon occurring when the yield stress is reached, resulting in nonlinear response of the material during loading. The phase transformation process leads to creation of two-phase continuum, where the parent phase coexists with the inclusions of secondary phase. An identification of the model parameters, based on uniaxial tension test at very low temperature, is also proposed.

scholarly journals A Phenomenological Mechanical Material Model for Precipitation Hardening Aluminium Alloys

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1165 ◽  
Author(s):  
Hannes Fröck ◽  
Lukas Vincent Kappis ◽  
Michael Reich ◽  
Olaf Kessler
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Finite Element ◽  
Phase Transformation ◽  
Aluminium Alloys ◽  
Material Model ◽  
Heat Treatments ◽  
Maximum Temperature ◽  
Finite Element Software ◽  
Welding Processes

Age hardening aluminium alloys obtain their strength by forming precipitates. This precipitation-hardened state is often the initial condition for short-term heat treatments, like welding processes or local laser heat treatment to produce tailored heat-treated profiles (THTP). During these heat treatments, the strength-increasing precipitates are dissolved depending on the maximum temperature and the material is softened in these areas. Depending on the temperature path, the mechanical properties differ between heating and cooling at the same temperature. To model this behavior, a phenomenological material model was developed based on the dissolution characteristics and experimental flow curves were developed depending on the current temperature and the maximum temperature. The dissolution characteristics were analyzed by calorimetry. The mechanical properties at different temperatures and peak temperatures were recorded by thermomechanical analysis. The usual phase transformation equations in the Finite Element Method (FEM) code, which were developed for phase transformation in steels, were used to develop a phenomenological model for the mechanical properties as a function of the relevant heat treatment parameters. This material model was implemented for aluminium alloy 6060 T4 in the finite element software LS-DYNA (Livermore Software Technology Corporation).

Residual Stress Modelling in a Thick-Sectioned Electron Beam Weld

2013 ◽  
Author(s):  
Ben Pellereau ◽  
Chris Gill ◽  
Paul Hurrell ◽  
Ed Kingston
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Electron Beam ◽  
Heat Source ◽  
Material Model ◽  
Hole Drilling ◽  
Electron Beam Weld ◽  
Element Analysis ◽  
Stress Measurements ◽  
Mesh Density

Previous work presented residual stress measurements in an electron beam weld in a thick section ferritic forging [1]; this weld was also modelled using finite element analysis. Due to the tool used to model the heat source, the mesh density in the region of the weld was limited. This work improves on the previous work by using a DFLUX subroutine to provide a mesh-independent heat source input, allowing a better mesh in the region of the weld. The modelling was carried out in Abaqus[2] using the VFT[3] user material model to allow phase transformation effects to be included. This however does not include creep properties and so the as-welded stresses were seeded on to a model that used Abaqus built-in material properties in order to model the heat treatment. The results of this analysis have been compared with analyses run using just the VFT material model (with no creep) and using just the Abaqus properties (with no phase transformation) in order to investigate the sensitivity of the stresses predicted to the material model used. The results of all three analyses have also been compared to the results of the original analysis and with the deep hole drilling residual stress measurements.

Projectile Material Model Included Phase Transformation Erosion

2014 ◽  
Vol 532 ◽  
pp. 510-514
Author(s):  
Jiang Bo Wang ◽  
Qing Ming Zhang ◽  
Gui Ying Xu ◽  
Wen Chen ◽  
Cheng Liang Feng
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Model Simulation ◽  
Material Model ◽  
Penetration Resistance ◽  
Austenite Phase

High temperature generated by target impact causes projectile austenite phase transformation. At high temperature, the austenite strength decreases rapidly and undergoes phase transformation erosion because of target impact. On this basis, a projectile material model which took phase transformation erosion into consideration was established and then the model was verified. Model simulation showed that after phase transformation erosion the projectile was subjective to tensile and compression instability. Dual-arc head design would significantly reduce projectile penetration resistance and decrease phase transformation influence on projectile stability.

Phase Transformation Properties Sensitivity Study in a Ferritic Groove Weld

2013 ◽  
Author(s):  
Benjamin Pellereau ◽  
Paul Hurrell ◽  
Christopher Gill ◽  
John Francis ◽  
Steve Bate
Keyword(s):  
Phase Transformation ◽  
Weld Metal ◽  
Material Properties ◽  
Physical And Mechanical Properties ◽  
Material Model ◽  
Sensitivity Study ◽  
Parent Metal ◽  
Grain Sizes ◽  
Austenite Grain ◽  
Complete Set

A previous paper (PVP2010-25649) presented work carried out to model a three pass groove weld in an SA508 plate using Abaqus with the VFT material model. The model used the SA508 physical and mechanical properties for both parent and weld metal, with phase transformation properties for a slightly different material as these were the only properties available at the time. A material properties testing programme has since been completed allowing the analysis to be rerun using a complete set of properties for both the parent metal (SA508) and the weld metal (SD3). Properties to describe the phase transformations on cooling from austenite were derived for a range of austenite grain sizes. This paper presents a sensitivity study comparing the predicted stresses and phase proportions when using the different properties, and the effects of using different properties for the two materials. With the updated material properties and by using separate properties for the parent and weld, the results have been improved significantly. The results show that, while changing the phase properties affected the predicted phase proportions and the stresses in the weld metal, the residual stress distribution in the parent metal, where the peak tensile stresses occur, did not change significantly.

Modelling Kinetics of Phase Transformation for the Indirect Hot Stamping Process

2013 ◽  
Vol 549 ◽  
pp. 108-116 ◽  
Author(s):  
Paul Hippchen ◽  
Marion Merklein ◽  
Arnulf Lipp ◽  
Michael Fleischer ◽  
Hannes Grass ◽  
...  
Keyword(s):  
Finite Element ◽  
Phase Transformation ◽  
Hot Stamping ◽  
Material Model ◽  
Model Parameters ◽  
Transformation Models ◽  
Predictive Quality ◽  
Stamping Process ◽  
Cooling Schedules ◽  
Kinetics Of

To configure the indirect hot stamping process, a finite-element-based prediction of the parts geometry and mechanical properties is required. In case of indirect hot stamping, inhomogeneous cooling schedules cause different phase transformation points and products. The volume expansion caused by phase transformation of fcc into bcc leads to transformation induced stresses that are important for the calculation of overall stresses in press hardened components. To calculate theses stresses correctly, it is necessary to study the kinetics of phase transformation in consideration of the cooling path of an indirect hot stamping process. Dilatometer tests are employed to obtain the kinetics of phase transformation is determined in dilatometer tests. These results are used to identify the parameters for the phase transformation models implemented in the material model *MAT_244 [ that is implemented in the finite-element-code LS-DYNA [. In this context the material model parameters are identified by using evolutionary optimization strategies. Based on the identified parameters the predictive quality of the implemented phase transformation models will be studied in order to improve their prediction accuracy for the indirect hot stamping process.

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.

Phase Transformation In Ti-6al-4v Alloys

1972 ◽  
Vol 30 ◽  
pp. 584-585
Author(s):  
Shiro Fujishiro
Keyword(s):  
Phase Transformation ◽  
Grain Boundary ◽  
Cryogenic Temperature ◽  
Β Phase ◽  
Heat Treated ◽  
Mixed Microstructure ◽  
Ductile Behavior

The Ti-6 wt.% Al-4 wt.% V commercial alloys have exhibited an improved formability at cryogenic temperature when the alloys were heat-treated prior to the tests. The author was interested in further investigating this unusual ductile behavior which may be associated with the strain-induced transformation or twinning of the a phase, enhanced at lower temperatures. The starting materials, supplied by RMI Co., Niles, Ohio were rolled mill products in the form of 40 mil sheets. The microstructure of the as-received materials contained mainly ellipsoidal α grains measuring between 1 and 5μ. The β phase formed an undefined grain boundary around the a grains. The specimens were homogenized at 1050°C for one hour, followed by aging at 500°C for two hours, and then quenched in water to produce the α/β mixed microstructure.

Microstructural and Microchemical Characterization of Nickel Sulfide Inclusions in Plate Glass

1991 ◽  
Vol 49 ◽  
pp. 962-963
Author(s):  
J. Cooper ◽  
O. Popoola ◽  
W. M. Kriven
Keyword(s):  
Thermal Expansion ◽  
Phase Transformation ◽  
Glass Matrix ◽  
Nickel Sulfide ◽  
Plate Glass ◽  
Thermal Expansion Mismatch ◽  
Volume Increase ◽  
Β Phase ◽  
Microchemical Characterization

Nickel sulfide inclusions have been implicated in the spontaneous fracture of large windows of tempered plate glass. Two alternative explanations for the fracture-initiating behaviour of these inclusions have been proposed: (1) the volume increase which accompanies the α to β phase transformation in stoichiometric NiS, and (2) the thermal expansion mismatch between the nickel sulfide phases and the glass matrix. The microstructure and microchemistry of the small inclusions (80 to 250 μm spheres), needed to determine the cause of fracture, have not been well characterized hitherto. The aim of this communication is to report a detailed TEM and EDS study of the inclusions.

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