The robotization of the FSW process is facing two challenges which are to support the amplitude of the tool / workpiece mechanical interaction generated by welding and to apply the process parameters and in particular the axial force. To design the control laws of the robot it is necessary to model the mechanical interaction between the tool and the workpiece as function of the fsw process parameters

ABBA, Gabriel

ALLAM, Zakaria

BIGOT, Régis

LANGLOIS, Laurent

ZIMMER-CHEVRET, Sandra

English

SAM : Science Arts et Métiers

Science Arts & Métiers (SAM)is an open access repository that collects the work of Arts et Métiers ParisTechresearchers and makes it freely available over the web where possible.This is an author-deposited version published in: http://sam.ensam.euHandle ID: .http://hdl.handle.net/10985/8932To cite this version :Zakaria ALLAM, Sandra ZIMMER-CHEVRET, Laurent LANGLOIS, Gabriel ABBA, Régis BIGOT -Statistical model of the tool/workpiece mechanical interactions in FSW - In: 2nd InternationalConference on Friction Stir Welding and Processing FSWP'2012, France, 2012-01-26 -Proceedings of 2nd International Conference on Friction Stir Welding and Processing FSWP'2012- 2012Any correspondence concerning this service should be sent to the repositoryAdministrator : archiveouverte@ensam.eu Statistical model of the tool/workpiece mechanical interactions in FSW Zakaria Allam(1), Chevret Sandra(2), Laurent Langlois(1), Gabriel Abba(1), Régis Bigot(1)  (1) LCFC, ARTS ET METIERS ParisTech Metz, 4 rue Augustin Fresnel, 57078 Metz cedex 1 (2) Institut de Soudure, Centre FSW, 2-4 Rue Pilâtre de Rozier, 57420 GOIN   Abstract The robotization of the FSW process is facing two challenges which are to support the amplitude of the tool / workpiece mechanical interaction generated by welding and to apply the process parameters and in particular the axial force. To design the control laws of the robot it is necessary to model the mechanical interaction between the tool and the workpiece as function of the fsw process parameters.   Keywords : Tool / workpiece interaction, FSW, Statistical laws   1 Introduction The prediction of the mechanical efforts between the tool and the material is essential for the implementation of a robotized FSW means of production. Indeed, due to the compliance of this type of structure the trajectories of the robot should be corrected to allow the tool to follow the weld joint. Furthermore, robots are generally position controlled while the FSW tool should be force controlled along its axis. The identification of the mechanical interaction behavior between the tool and the work-piece is necessary to design the control of a robotized FSW means of production. In this article, the evolution laws giving the tool/workpiece mechanical interaction are established statistically [1] in the case of a butt weld of two aluminium 6082 T651, 6 mm thick sheets. An experimental plan is conducted with as input parameters the three main process parameters [2]: the travel speed, the spindle speed and the axial force. For each test, three mechanical interaction components are measured: the spindle torque, the travel force and the transverse force.   2 Results Two types of statistical models are studied. The first one corresponds to power laws. The results obtained with this type of law well fit the evolution of the spindle torque and, to a lesser extent, the one of the travel force. However, the transverse force is not well fitted, the quadratic mean squared error being important.  The analyze of the two first power law shows that the spindle torque is a function of the spindle rotation speed and the axial force. The coefficient of intercorrelation between the spindle rotation speed and the travel speed is weak. The travel force is a function depending on the travel speed and the axial force. The statistical analyze shows that the transverse force seems not to be correlated to any process parameters if considered separately.  For a constant axial force, the evolution of the transverse force versus the ratio rotation speed on travel speed is convex as illustrated on the figure 1.  10.60.50.80.90.70.61.600.511.522.50 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5R = N / v a [tr/mm]F y [kN]Fy=f(Va); Soudure OK Fy=f(N)  Soudure OK Fy=f(Va) Soudure NOK Fy=f(N) Soudure NOK  Figure 1 : Evolution de the transverse force versus rotation speed on travel speed ratio A simplified model of the distribution of the stress around the tool is proposed in order to explain the evolution of the transverse force as function of the process parameters. This model is based on a temperature distribution corresponding to simplified results extracted from the litterature [3]. The parameters of the model are identified from the experimental result concerning the spindle torque and the travel force. These parameters are then kept in order to calculate the transverse force. This last one is then compared to the experimental one.    3 Conclusions The results of the study show that the evolution of spindle torque and the travel force can be modeled by power laws of the FSW process parameters. On the other side, power law doesn’t fit well the transverse force. The evolution of this force probably comes from two phenomena:  - for high spindle speed and low travel speed, the decrease of the ductility of the material at the back of the tool due to heating excess, the temperature reached can rise the semi solid state. This is supported by the observation of scales on the surface of the weld bead for high axial force. This causes an imbalance between the front and the back of the tool shoulder causing an increase in the transverse component of the tool workpiece effort. - for the low value of spindle rotation speed and high value of travel speed, an imbalance of the distribution of stress distribution around the pin of the tool between the advancing and the retreating side. This is supported by the appearance of the tunnel default for value of the process parameters closed to the considered ones.    References [1] X. Zhao, P. Kalya, R.G. Landers, K. Krishnamurthy, Design and implementation of non-linear force controllers for friction stir welding, Proceeding of the 2007 American Control Conference, July 2007, New-York. [2] S. Zimmer, Contribution à l’industrialisation du soudage par friction malaxage, Mémoire de Thèse, (2009) [3] A. Bastier, M.H. Maitournam, F. Roger, K. Dang Van, Modelling of the residual state of friction stir welded plates, Journal of material processing technology, Volume 200, Issues 1-3, pp25-37, (2008) 

Contribution à l’industrialisation du soudage par friction malaxage, Mémoire de Thèse,

Design and implementation of non-linear force controllers for friction stir welding,

Modelling of the residual state of friction stir welded plates,

Statistical model of the tool/workpiece mechanical interactions in FSW

SAM;  the Arts et Métiers ParisTech open access repository

Science Arts & Métiers (SAM)
is an open access repository that collects the work of Arts et Métiers ParisTech
researchers and makes it freely available over the web where possible.
This is an author-deposited version published in: https://sam.ensam.eu
Handle ID: .http://hdl.handle.net/10985/8932
To cite this version :
Zakaria ALLAM, Sandra ZIMMER-CHEVRET, Laurent LANGLOIS, Gabriel ABBA, Régis BIGOT -
Statistical model of the tool/workpiece mechanical interactions in FSW - In: 2nd International
Conference on Friction Stir Welding and Processing FSWP'2012, France, 2012-01-26 -
Proceedings of 2nd International Conference on Friction Stir Welding and Processing FSWP'2012
- 2012
Any correspondence concerning this service should be sent to the repository
Administrator : archiveouverte@ensam.eu
 Statistical model of the tool/workpiece 
mechanical interactions in FSW 
Zakaria Allam(1), Chevret Sandra(2), Laurent Langlois(1), Gabriel Abba(1), 
Régis Bigot(1) 
 
(1) LCFC, ARTS ET METIERS ParisTech Metz, 4 rue Augustin Fresnel, 57078 
Metz cedex 1 
(2) Institut de Soudure, Centre FSW, 2-4 Rue Pilâtre de Rozier, 57420 GOIN 
 
 
Abstract 
The robotization of the FSW process is facing two challenges 
which are to support the amplitude of the tool / workpiece 
mechanical interaction generated by welding and to apply the 
process parameters and in particular the axial force. To design the 
control laws of the robot it is necessary to model the mechanical 
interaction between the tool and the workpiece as function of the 
fsw process parameters.  
 
Keywords : Tool / workpiece interaction, FSW, Statistical laws 
 
 
1 Introduction 
The prediction of the mechanical efforts between the tool and the 
material is essential for the implementation of a robotized FSW 
means of production. Indeed, due to the compliance of this type of 
structure the trajectories of the robot should be corrected to allow 
the tool to follow the weld joint. Furthermore, robots are generally 
position controlled while the FSW tool should be force controlled 
along its axis. The identification of the mechanical interaction 
behavior between the tool and the work-piece is necessary to 
design the control of a robotized FSW means of production. 
In this article, the evolution laws giving the tool/workpiece 
mechanical interaction are established statistically [1] in the case 
of a butt weld of two aluminium 6082 T651, 6 mm thick sheets. An 
experimental plan is conducted with as input parameters the three 
main process parameters [2]: the travel speed, the spindle speed 
and the axial force. For each test, three mechanical interaction 
components are measured: the spindle torque, the travel force and 
the transverse force. 
  
2 Results 
Two types of statistical models are studied. The first one 
corresponds to power laws. The results obtained with this type of 
law well fit the evolution of the spindle torque and, to a lesser 
extent, the one of the travel force. However, the transverse force is 
not well fitted, the quadratic mean squared error being important.  
The analyze of the two first power law shows that the spindle 
torque is a function of the spindle rotation speed and the axial 
force. The coefficient of intercorrelation between the spindle 
rotation speed and the travel speed is weak. The travel force is a 
function depending on the travel speed and the axial force. 
The statistical analyze shows that the transverse force seems not to 
be correlated to any process parameters if considered separately.  
For a constant axial force, the evolution of the transverse force 
versus the ratio rotation speed on travel speed is convex as 
illustrated on the figure 1. 
 
1
0.6
0.5
0.8
0.9
0.7
0.6
1.6
0
0.5
1
1.5
2
2.5
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5
R = N / v a [tr/mm]
F y
 
[k
N
]
Fy=f(Va); Soudure OK Fy=f(N)  Soudure OK Fy=f(Va) Soudure NOK Fy=f(N) Soudure NOK
 
 
Figure 1 : Evolution de the transverse force versus rotation speed on travel speed 
ratio 
A simplified model of the distribution of the stress around the tool 
is proposed in order to explain the evolution of the transverse 
force as function of the process parameters. This model is based on 
a temperature distribution corresponding to simplified results 
extracted from the litterature [3]. The parameters of the model are 
identified from the experimental result concerning the spindle 
torque and the travel force. These parameters are then kept in 
order to calculate the transverse force. This last one is then 
compared to the experimental one.  
 
 
3 Conclusions 
The results of the study show that the evolution of spindle torque 
and the travel force can be modeled by power laws of the FSW 
process parameters. On the other side, power law doesn’t fit well 
the transverse force. The evolution of this force probably comes 
from two phenomena:  
- for high spindle speed and low travel speed, the decrease 
of the ductility of the material at the back of the tool due to 
heating excess, the temperature reached can rise the semi 
solid state. This is supported by the observation of scales 
on the surface of the weld bead for high axial force. This 
causes an imbalance between the front and the back of the 
tool shoulder causing an increase in the transverse 
component of the tool workpiece effort. 
- for the low value of spindle rotation speed and high value 
of travel speed, an imbalance of the distribution of stress 
distribution around the pin of the tool between the 
advancing and the retreating side. This is supported by the 
appearance of the tunnel default for value of the process 
parameters closed to the considered ones.  
 
 
References 
[1] X. Zhao, P. Kalya, R.G. Landers, K. Krishnamurthy, Design and 
implementation of non-linear force controllers for friction stir welding, 
Proceeding of the 2007 American Control Conference, July 2007, New-York. 
[2] S. Zimmer, Contribution à l’industrialisation du soudage par friction 
malaxage, Mémoire de Thèse, (2009) 
[3] A. Bastier, M.H. Maitournam, F. Roger, K. Dang Van, Modelling of the 
residual state of friction stir welded plates, Journal of material processing 
technology, Volume 200, Issues 1-3, pp25-37, (2008) 


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Statistical model of the tool/workpiece mechanical interactions in FSW

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