Meshfree simulation of friction stir welding process
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The document discusses modeling friction stir welding and processing using smoothed particle hydrodynamics (SPH). SPH is a Lagrangian meshfree method that can simulate the large plastic deformation and material mixing of friction stir processes. Prior research has used SPH to study temperature distribution, grain size evolution, microhardness, and texture development during welding. The document outlines the governing equations of SPH and highlights several studies that have modeled friction stir welding and processing using this approach.
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Buffa et al. [3–5] used FEM to develop a hybrid model ca
pable of determining the residual
stresses in the resulting weld. They split the FSW proces
s simulation into two phases. In the
first phase, they model the plunge, dwell, and advance u
sing a rigid viscoplastic model (fluidbased)
that does not provide elastic stresses. Then, they switch
to an elastic-plastic model to
approximately calculate the resulting residual stresses d
uring weld cooldown. They are able
to obtain good correlation for the residual stresses. On th
e downside, their model does not
allow for tracking defects since the welding phase is bas
ed on a fluid model](https://image.slidesharecdn.com/sph-230405075542-637d18a2/85/Meshfree-simulation-of-friction-stir-welding-process-6-320.jpg)
Meshfree simulation of friction stir welding process
- 1. The Meshfree Simulation of Friction Stir Welding/Processing Abhishek Kumar Singh
- 2. 2 I. Introduction Background Although the advantages such as low density and high st J. Singh et al., J. Alloys Compd. 778 (2019) 124-133. J. Singh et al., J. Alloys Compd. 708 (2017) 694-705. * W. He et al., MSEA (2016) * J.C.Baird et al., Scripta (2012)
- 3. 3 As the tool rotates and traverses, severely plasticized material migrates from ret reating, to advancing side, and deposits in the wake of the tool. nge phase, ell or stabilization phase, ding or advancing phase, l removal or retraction phase. I. Friction Stir Processing Introduction Ansari et al., Modelling Simul. Mater. Sci. Eng (2019)
- 4. 4 The physical principle of FSW has also been used to improve the microstructure of the workpieces. In this technique, called friction stir processing (FSP), an FSW tool is used to modify the microstructure of the material. The principal improvements ma de by FSP are as follows: • Creation of very fine microstructures to obtain super plasticity (nanograins can be produced); • Homogenization of the microstructure to reduce segregation, eliminate porosity, a nd increase mechanical properties, ductility, and corrosion resistance; • Introduction of particles to develop composite surface (metal matrix composite (M MC)) and modify the elasticity, wear resistance, thermal and electrical conductivity, or internal damping of the material. The local modifications performed by FSP to the microstructure can be very benefic ial in a zone of high stress, where a good ductility is needed, or where the fatigue lif e should be increased.
- 5. 5 large plastic deformation and material mixing common to FSW are well captured by the mesh-free method. I. SPH Capabilities This simulation approach allows the determination of temperature evolution, elastic and plastic deformation, defect formation, residual stresses, and material flow all wi thin the same model.
- 6. 6 Buffa et al. [3–5] used FEM to develop a hybrid model ca pable of determining the residual stresses in the resulting weld. They split the FSW proces s simulation into two phases. In the first phase, they model the plunge, dwell, and advance u sing a rigid viscoplastic model (fluidbased) that does not provide elastic stresses. Then, they switch to an elastic-plastic model to approximately calculate the resulting residual stresses d uring weld cooldown. They are able to obtain good correlation for the residual stresses. On th e downside, their model does not allow for tracking defects since the welding phase is bas ed on a fluid model
- 7. 7 I. Incompressible Navier-Stokes equation
- 8. 8
- 9. 9 Vi= velocity of the particle g- gravity 𝛻𝑷 − 𝒗𝒆𝒍𝒐𝒄𝒊𝒕𝒚 𝒈𝒓𝒂𝒅𝒊𝒆𝒏𝒕 Smooth particle hydrodynamics is how to solve incompressible N-S equation for single particle Convective acceleration term
- 10. 10
- 11. 11 SPH uses an evolving interpolation scheme to approximate a field variable at any p oint in a domain. The value of a variable at a particle of interest n be approximated by summing the contributions from a set of neighboring particles, denoted by subsc ript j, for which the “kernel” function, W, is not zero The smoothing length, h, determines how many part icles influence the interpolation for a particular point W- Kernel (Smoothing) function, In SPH, the material is discretized with separate sets of points or particle s and a continuous field f(xi) is approximated at the discretization points
- 12. 12 The implementation is based on the classical smoothed particle hydrodynamic the ory as outlined in the references below. You also have the option of using a mean flow correction configuration upd ate, commonly referred to in the literature as the XSPH method (see Monaghan, 1992), as well as the correcte d kernel of Randles and Libersky, 1997, also referred to as the normalized SPH (NSPH) method. The characteristic length is half the length of the cube side.
- 13. 13 For these methods you do not define nodes and elements as you would nor mally define in a finite element analysis; instead, only a collection of points a re necessary to represent a given body. In smoothed particle hydrodynamics these nodes are commonly referred to as particles or pseudo-particles. Smoothed particle hydrodynamics is a fully Lagrangian modeling scheme permitting the scretization of a prescribed set of continuum equations by interpolating the properties di ctly at a discrete set of points distributed over the solution domain without the need to d ne a spatial mesh
- 14. 14 Mixing flow during FSW Pan et al. / International Journal of Plasticity (2013)
- 15. 15 Literature W. Pan et al. / International Journal of Plasticity 48 (2013) The retreating side (RS) shows finer grain size than the advancing side (AS) high-translational and low-rotational tool speeds are ideal to cause effective grain refinement and higher hardness of the material Pan et al. studied the friction stir welding (FSW) using smoothed particle hydrodynamics (SPH) model and studied the temperature history and distribution, grain size, microhardness as well as the texture evolution Mixing flow during FSW
- 16. 16 • Pan et al. (2013) considered each SPH particle to represent a polycrystalline re presentative volume element (RVE), and we assume a weak coupling between the SPH simulations and crystal plasticity modeling. • Particle velocities obtained from the SPH solution at each time step are used t o calculate the plastic velocity gradient for the polycrystalline deformation beh avior. Texture evolution is then computed using crystal plasticity modeling Conti.. TMAZ particle pole Fig. W. Pan et al. / International Journal of Plasticity 48 (2013) Simulation of texture evolution
- 17. 17 Literature Ansari et al. (2019) studied the plunging phase friction stir welding of Al 6082 all oy using SPH modeling with different rotational speed and plunging phase and s tudied the stress and strain distribution near tool pin The force and tarque from simulation were compared with experimental and the results were in close agreement. They studied the effect of tool rotational speed on the force field, stress, and eq uivalent plastic strain at different tool depth in the plunging stage. Increasing the plunge depth, the stress, strain, and force field is increased. Furthermore, increasing rotational speed from 600 to 1200 rpm, stress, and equi valent plastic strain increased by about 3% and 19%, respectively, while the force decreased by 22%.
- 18. 18 Xiao et al. (2016) studied the heat transfer during friction stir welding using a modified SPH model heat source model based on sticking friction is implemented to describe the heat generation of FSW
- 19. 19 Coupled Eulerian Lagrangian Method
- 20. 20 Simulation of FSP Tool Backing Plate Locking Strips A, B, n, C and m are the five material constants JC Parameter A (MPa) B (MPa) C n m 324 114 0.002 0.42 1.34 Shear Modulus (GPa) Density (Kg/m3) (Al-6061T6) Cut-off Pressure (MPa) 27.6 2700 1200 Johnson-Cook material model Constitutive Equation Al Plate Gruneisen EOS Units 0 2700 Kg/m3 C 5328 m/s 0 1.97 - S1 1.4 - a 0.48 - Al-6061T6 Thermal Parameters Cv k Values 875 175 Units J/KgK W/mK
- 21. 21
- 22. 22 Distribution of state variables Plunging stage
- 24. 24 3 4 5 RS AS RS AS RS AS RS AS RS AS 1 2 Mixing of particles and Nodal Tracking
- 25. 25 Advancing/Welding Phase Plunge phase Dwell phase Tool Force
- 27. Scope of novelty Limited research is available on modeling FSW of Ti alloy Very limited (4-5) study is available on SPH modeling of FSP and nil on Ti alloy Modification of more stable Kernal function (for SPH modeling )using su broutine The combined study of SPH and VPSC simulation to study texture predi ction
- 28. 28 Future Work • SPH model benchmarking • Selection and Implementation of a proper smoothing (Kernal) fu- nction • SHP simulation and analysis for FSP of CP Ti • Texture analysis (ODF) of FSP CP Ti material • Texture Simulation using VPSC • Manuscript writing
Editor's Notes
- #2: Good afternoon, ladies and gentleman My name is min-seong kim in sunchon national university. Today, my presentation topic is the effect of anisotropy in Mg alloys on bendability under the mini-V-bending test
- #4: Plunge- insertion of pin Dwell- Tool rotate at the same place to achieve sufficient temperature for welding
- #6: Joining Technologies : Chapter 3
- #12: The method is less accurate in general than Lagrangian finite element analyses when the deformation is not too severe and than coupled Eulerian-Lagrangian analyses in higher deformation regimes
- #16: lower temperature and higher strain rate are more favorable to grain refinement They used the Zener–Hollomon parameter and Hall–Petch relationship to predict variations in grain size and microhardness resulting