Modeling and Experimental Verification of Transient/Residual Stresses and Microstructure Formation in Multi-Layer Laser Aided DMD Process

2005 ◽  
Vol 128 (7) ◽  
pp. 662-679 ◽  
Author(s):  
S. Ghosh ◽  
J. Choi
Keyword(s):  
Phase Transformation ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Steel Substrate ◽  
High Energy ◽  
Solidification Microstructure ◽  
Heat Transfer Analysis ◽  
Mushy Region ◽  
Element Analysis ◽  
Energy Beam

Despite enormous progress in laser aided direct metal/material deposition (LADMD) process many issues concerning the adverse effects of process parameters on the stability of variety of properties and the integrity of microstructure have been reported. Comprehensive understanding of the transport phenomena and heat transfer analysis is essential to predict the thermally induced residual stresses and solidification microstructure in the deposited materials. Traditional solidification theories as they apply to castings or related processes, assume either no mass diffusion in the solid (Gulliver-Scheil) or complete diffusion in the solid (equilibrium lever rule) in a fixed arm space. These are inappropriate in high energy beam processes involving significantly high cooling rates. The focus of this paper is the solute transport in multi-pass LADMD process, especially the coupling of the process scale transport with the transport at the local scale of the solid-liquid interface. This requires modeling of solute redistribution at the scale of the secondary arm spacing in the dendritic mushy region. This paper is an attempt toward a methodology of finite element analysis for the prediction of solidification microstructure and macroscopic as well as microscopic thermal stresses. The computer simulation is based on the metallo-thermo-mechanical theory for uncoupled temperature, solidification, phase transformation, and stress/strain fields. The importance of considering phase transformation effects is also verified through the comparison of the magnitudes of residual stresses with and without the inclusion of phase transformation kinetics. The simulation has been carried out for H13 tool steel deposited on a mild steel substrate.

Three Dimensional Transient Finite Element Analysis for Microstructure Formation and Residual Stresses in Double-Pass Laser Aided DMD Process

2004 ◽  
Author(s):  
S. Ghosh ◽  
J. Choi
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Heat Flow ◽  
Thermal Stresses ◽  
High Energy ◽  
Mass Diffusion ◽  
Mushy Region ◽  
Element Analysis ◽  
Energy Beam ◽  
Solid Liquid

Despite immense advances in Laser Aided Direct Metal/Material Deposition (LADMD) process many issues concerning the effects of process parameters on the stability of variety of properties and the integrity of microstructure have been reported. Modeling of heat flow seems to be a standard practice to couple heat flow calculations to related macroscopic phenomena such as fluid flow in the melt and solid-liquid mushy region, macrosegregation and thermal stresses. A key component in these models is the coupling between thermal and solute fields. Like macrostructural phenomena even microstructural features such as phase appearance, morphology, grain size or spacing are certainly no less important. The focus of this paper is the solute transport, in particular the manner in which process scale transport is coupled to transport at the local scale of the solid-liquid interface which requires a modeling of the redistribution of solutes at the scale of the secondary arm spaces in the dendritic mushy region. Basic microsegregation models which assume either no mass diffusion in the solid (Gulliver-Scheil) or complete diffusion in the solid (equilibrium lever rule) in a fixed arm space are inappropriate in high energy beam processes involving significantly high cooling rates. This paper aims at incorporating a model that accounts for finite mass diffusion and coarsening of the arm space. Due to the complexity and nonlinearity of LADMD process, analytical solutions can rarely address the practical manufacturing process. Consequently, this is an attempt towards a methodology of finite element analysis to predict solidification microstructure and thermal stresses. The simulation has been carried out for H13 tool steel deposited on a mild steel substrate. However, the program can easily be extended to a wide variety of steels.

Three-Dimensional Transient Finite Element Analysis for Microstructure Formation and Residual Stresses in Laser-Aided DMD Process

Volume 3 ◽  
2004 ◽  
Author(s):  
S. Ghosh ◽  
J. Choi
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Residual Stresses ◽  
Process Parameters ◽  
Deposition Process ◽  
High Energy ◽  
Material Behavior ◽  
Process Conditions ◽  
Element Analysis ◽  
Energy Beam

Despite immense advances in Laser-Aided Direct Material Deposition process, many issues concerning the adverse effects of process parameters on the stability of variety of properties and the integrity of microstructure have been reported. Macroscopic aspects are important in predicting macroscopic defects or optimizing process conditions, while microstructural features such as phase appearance, morphology, grain size, spacing, or micro-defects are certainly no less important in determining the ultimate properties of the solidified product. Traditional solidification theories as applied to castings or related processes are inappropriate in describing solidification in high-energy beam processes involving significantly greater cooling rates. Due to the complexity and nonlinearity of this process, analytical solutions can rarely address the practical manufacturing process. This paper is an attempt towards a methodology of finite element analysis for the prediction of solidification microstructure and macroscopic as well as microscopic thermal residual stresses in this process. The computer simulation which is based on metallo-thermomechanical theory and finite element analysis for coupled temperature, solidification, phase transformation and stress/strain fields can prove to be a very useful tool in predicting the material behavior and optimizing the process parameters to obtain the best material properties. This model would reduce long and cumbersome experimental routes to predict the material behavior under similar loading conditions.

Three-Dimensional Transient Residual Stress Finite Element Analysis for a Laser Clad Surface

2003 ◽  
Author(s):  
S. Ghosh ◽  
J. Choi
Keyword(s):  
Residual Stress ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Phase Transformation ◽  
Residual Stresses ◽  
Material Behavior ◽  
Heat Transfer Analysis ◽  
Transformation Kinetics ◽  
Element Analysis ◽  
Phase Transformation Kinetics

Laser aided manufacturing process inherently includes many nonlinear and non-equilibrium transport phenomena due to non-uniform and rapid heat flow caused by the laser and the material interaction. Comprehensive understanding of the transport phenomenon and heat transfer analysis including phase transformation is essential to predict the effects of thermally induced residual stresses and distortions in deposited materials. It not only helps to improve the process but also reduces the long and cumbersome experimental route to compile sufficient data to predict the material behavior under similar loading conditions. This paper is an attempt towards a methodology of finite element analysis for the prediction of quenching related macroscopic as well as microscopic residual stress in a laser cladding process. A finite element program has been written to account for the micro-residual stress effects. The program is essentially a coupling between a preliminary estimation of temperature history of the system and the final prediction of residual stresses which also include the phase transformation kinetics of the material during its cooling. The importance of considering phase transformation effects during quenching is also verified through the comparison of the magnitudes of residual stresses with and without the inclusion of phase transformation kinetics. The FEA program for this model is a very useful tool for designing and optimizing Laseraided Direct Metal Deposition (DMD) process conditions so that products with the best internal quality and dimensional accuracy can be built.

Residual Stresses in Multilayer Welds with Different Martensitic Transformation Temperatures Analyzed by High-Energy Synchrotron Diffraction

2011 ◽  
Vol 681 ◽  
pp. 37-42 ◽  
Author(s):  
Arne Kromm ◽  
Thomas Kannengiesser ◽  
Jens Altenkirch ◽  
Jens Gibmeier
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Residual Stresses ◽  
Weld Metal ◽  
High Energy ◽  
X Ray Diffraction ◽  
Surface Areas ◽  
Transformation Mechanisms ◽  
Positive Effect ◽  
Compressive Residual Stresses

Low Transformation Temperature (LTT) alloys were developed in order to control the residual stress development by the martensitic phase transformation already during cooling of the weld metal. The positive effect of such LTT alloys on the mitigation of detrimental tensile residual stresses during welding has already been confirmed on the basis of individual laboratory tests. Within the current project it was experimentally investigated whether the phase transformation mechanisms are effective under increased restraint due to multi-pass welding of thicker specimens. The local residual stress depth distribution was analyzed non-destructively for V-type welds processed by arc welding using energy dispersive synchrotron X-ray diffraction (EDXRD). The use of high energy (20 keV to 150 keV) EDXRD allowed for the evaluation of diffraction spectra containing information of all contributing phases. As the investigated LTT alloy contains retained austenite after welding, this phase was also considered for stress analysis. The results show in particular how the constraining effect of increased thickness of the welded plates and additional deposited weld metal influences the level of the residual stresses in near weld surface areas. While the longitudinal residual stresses were reduced in general, in the transition zone from the weld to the heat-affected zone (HAZ) compressive residual stresses were found.

Finite element analysis of the phase transformation effect in residual stresses generated by quenching in notched steel cylinders

2005 ◽  
Vol 40 (2) ◽  
pp. 151-160 ◽  
Author(s):  
E P Silva ◽  
P M C L Pacheco ◽  
M. A Savi
Keyword(s):  
Finite Element ◽  
Phase Transformation ◽  
Residual Stresses ◽  
Induction Hardening ◽  
Martensite Phase ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Thermomechanical Behaviour ◽  
Quenching Process

The determination of residual stresses is an important task in the analysis of the quenching process. Nevertheless, because of the complexity of the phenomenon, many simplifications are usually adopted in the prediction of these stresses for engineering purposes. One of these simplifications is the effect of phase transformation. Many studies analyse residual stresses generated by the quenching process considering a thermoelastoplastic approach, neglecting phase transformation. The present study analyses the effect of austenite-martensite phase transformation during quenching in the determination of residual stresses, comparing two different models: complete (thermoelastoplastic model with austenite-martensite phase transformation) and without phase transformation (thermoelastoplastic model without phase transformation). The finite element method is employed for spatial discretization together with a constitutive model that represents the thermomechanical behaviour of the quenching process. Progressive induction hardening of steel cylinders with semicircular notches is of concern. Numerical simulations show situations where great discrepancies are introduced in the predicted residual stresses if phase transformation is neglected.

Numerical Investigation of Thermal Stresses in Surface Layer of Si3N4 Ceramics in Laser Processing

2015 ◽  
Vol 806 ◽  
pp. 104-108
Author(s):  
Valery V. Kuzin ◽  
Sergey Fedorov ◽  
Predrag Dašić ◽  
Mike Portnoy
Keyword(s):  
Finite Element Method ◽  
Surface Layer ◽  
Laser Processing ◽  
Small Area ◽  
Strain State ◽  
Thermal Stresses ◽  
Ceramic Materials ◽  
High Energy ◽  
Stress Fields ◽  
Energy Beam

The laser processing has the ability for effective machining of ceramic materials because of high energy beam acting on a very small area. The stress-strain state of surface layer of Si3N4 ceramics in laser processing was investigated with the use of finite element method to compute the temperature and stress fields. The effect of heat flow on thermal stresses was discussed in terms of the results of the numerical experiment.

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.

Development of Predicted Stress and Strain during Conventional and after Mitigation of Welded Aluminium-Manganese Alloy

2013 ◽  
Vol 762 ◽  
pp. 596-601
Author(s):  
F. Soul ◽  
M. Ateeg
Keyword(s):  
Heat Transfer ◽  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Stress And Strain ◽  
Manganese Alloy ◽  
Element Analysis ◽  
Longitudinal Residual Stress ◽  
Mitigation Technique

The trend in automotive, aircraft, and marine industries is the increasing use of sheet materials to reduce weight in components and optimize materials performance. Welding is the main fabrication and assembly process in many of these industrial applications. However, in using thin-shell structures in such applications, welding may results in significant residual stresses and out-of-plane distortion. Transient thermal stresses, residual stresses, and distortion sometimes cause cracking and mismatching of joints. High tensile residual stresses are undesirable since they can contribute to fatigue failure. The analysis and measurement of temperature and stresses in component are often too complex to conduct in practise, and thus finite element models provide feasible approach to examine these matters. In this paper, finite element analysis has been performed using the ANSYS package to study the behaviour of longitudinal residual stress and strain in a welded thin aluminium-manganese alloy. The model presented simulates conventional welding and welding with the introduction of welding mitigation technique for enhancement of heat transfer, in which a trailing heat sink was applied. The thermal profiles obtained using the mitigation technique is completely different from those obtained in the conventional cooling. The localized transient residual stress and through-thickness strain after applying a cooling sink are discussed. The transient residual stress behaviour was highly affected by the modified temperature distribution and magnitude due to introducing the heat transfer enhancement.

Residual Stresses in Strength Mismatched Welded Pipes

2017 ◽  
Author(s):  
Ali Mirzaee-Sisan ◽  
Junkan Wang
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Structural Integrity ◽  
Welding Residual Stress ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Element Analysis ◽  
Girth Welds ◽  
Welded Pipe

It is commonly understood that residual stresses can have significant effects on structural integrity. The extent of such influence varies and is affected by material properties, manufacturing methods and thermal history. Welded components such as pipelines are subject to complex transient temperature fields and associated thermal stresses near the welded regions. These thermal stresses are often high in magnitude and could cause localized yielding around the deposited weld metal. Because of differential thermal expansion/contraction episodes, misfits are introduced into the welded regions which in turn generate residual stresses when the structure has cooled to ambient temperature. This paper is based on a recently completed Joint Industry Project (JIP) led by DNV GL. It briefly reviews published experimental and numerical studies on residual stresses and strength-mismatched girth welds in pipelines. Several Finite Element Analysis (FEA) models of a reeling simulation have been developed including mapping an initial axial residual stress (transverse to the weld) profile onto a seamless girth-welded pipe. The initial welding residual stress distribution used for mapping was measured along the circumference of the girth welds. The predicted residual stresses after reeling simulation was subsequently compared with experimental measurements.

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