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Research Papers

Empirical Dynamic Modeling of Friction Stir Welding Processes

[+] Author and Article Information
Xin Zhao

HHP Diesel Electronic Controls, Cummins Inc., 2851 State Street, Columbus, IN 47201

Prabhanjana Kalya

Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, 1870 Miner Circle, Rolla, MO 65409-0050pk34b@mst.edu

Robert G. Landers

Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, 1870 Miner Circle, Rolla, MO 65409-0050landersr@mst.edu

K. Krishnamurthy

Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, 1870 Miner Circle, Rolla, MO 65409-0050kkrishna@mst.edu

J. Manuf. Sci. Eng 131(2), 021001 (Feb 24, 2009) (9 pages) doi:10.1115/1.3075872 History: Received August 27, 2007; Revised December 11, 2008; Published February 24, 2009

Current friction stir welding (FSW) process modeling research is mainly concerned with the detailed analysis of local effects such as material flow, heat generation, etc. These detailed thermomechanical models are typically solved using finite element or finite difference schemes and require substantial computational effort to determine temperature, forces, etc., at a single point in time, or for a very short time range. Dynamic models describing the total forces acting on the tool throughout the entire welding process are required for the design of feedback control strategies and improved process planning and analysis. In this paper, empirical models relating the process parameters (i.e., plunge depth, travel speed, and rotation speed) to the process variables (i.e., axial, path, and normal forces) are developed to understand their dynamic relationships. First, the steady-state relationships between the process parameters and the process variables are constructed, and the relative importance of each process parameter on each process variable is determined. Next, the dynamic characteristics of the process variables are determined using recursive least-squares. The results indicate the steady-state relationship between the process parameters and the process variables is well characterized by a nonlinear power relationship, and the dynamic responses are well characterized by low-order linear equations. Experiments are conducted that validate the developed FSW dynamic models.

Copyright © 2009 by American Society of Mechanical Engineers
Topics: Force , Welding , Rotation
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References

Figures

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Figure 1

Friction stir welding operation schematics for lap welding

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Figure 2

IRB 940 Tricept manipulator (a) and S4cPlus controller (b)

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Figure 3

FSW Head with tool (a) and FSW head control housing (b)

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Figure 4

Comparison of filtered and original measured axial force signals during steady-state portion of a FSW operation (v=2.6 mm/s, ω=1600 rpm, and d=4.191 mm)

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Figure 5

Nugget cross sections with slight hooking defects: (a) ω=1600 rpm, v=2.6 mm/s, and d=4.445 mm, and (b) ω=2100 rpm, v=2.6 mm/s, and d=4.445 mm

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Figure 6

Axial force responses for step changes in process parameters: (a) experiment 6 from Group 1, (b) experiment 5 from Group 2, and (c) experiment 4 from Group 3

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Figure 7

Modeled versus measured steady-state axial force

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Figure 8

Axial force responses to travel speed step changes: (a) experiment 3 from Group 2, and (b) experiment 7 from Group 2

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Figure 9

Axial force responses to rotation speed step changes: (a) experiment 3 from Group 3, and (b) experiment 5 from Group 3.

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Figure 10

Modeled versus measured steady-state path force

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Figure 11

Path force transient responses to step changes in process parameters: (a) experiment 5 from Group 1, (b) experiment 5 from Group 2, and (c) experiment 8 from Group 3

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Figure 12

Path force transient responses. Top: travel speed changed from 2.6 mm/s to 2.0 mm/s. Bottom: rotation speed changed from 1900 rpm to 2100 rpm.

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Figure 13

Modeled versus measured steady-state normal force

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Figure 14

Normal force responses to plunge depth step changes: (a) experiment 3 from Group 1, and (b) experiment 4 from Group 1

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Figure 15

Normal force response to travel speed step change (experiment 9, Group 2).

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Figure 16

Measured and modeled axial forces for step changes in plunge depth (experiment 5, Group 1, ω=1600 rpm, v=2.6 mm/s)

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Figure 17

Measured and modeled axial forces for sinusoidal change in plunge depth (ω=1600 rpm, v=2.6 mm/s)

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Figure 18

Path force model validation experimental results (d=4.445 mm)

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Figure 19

Normal force model validation experiments (d=4.445 mm)

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