Flow Fields in the Vicinity of FSW Pin Tools

1
Flow Fields in the Vicinity of FSW Pin Tools

• By
• Mike Langerman
• Edvin Kvalvik
• Greg Buck
• South Dakota School of Mines Technology

2
Outline

• Introduction
• Objectives
• Models
• Results
• Summary
• Conclusions

3
Introduction

• FSW- understanding the process
• Analytical compliment experimental
• Process optimization
• Lack of consensus of participants

4
Objectives

• Investigate fluid mechanics modeling approach to
  FSW plastic metal deformation process for
  2195-T87 aluminum alloy.
• Investigate potential flow regimes.
• Investigate heat generation due to viscous heat
  dissipation.

5
Models/domain
6
Models/tool
7
Models/Thermal BCs

• Surface temperatures along top and tool supplied
  from HT calculations that assumed a 1KW energy
  source located
• Shoulder
• Tip
• Bottom surface insulated
• Side surfaces maintained at 90ºC

8
Models/fluid

• Non-newtonian fluid

9
Models/fluid

• Non-newtonian fluid

10
Models/Calculations
11
Models/Results
Profiles of viscosity through center of
work-piece
12
Models/Results
Profiles of viscosity along the weld line
13
Models/Results
Velocity vectors in center of work-piece
14
Models/Results
Velocity vectors transverse to weld line
15
Models/Results
Temperature profiles along weld line
16
Models/Results
Temperature profiles transverse to weld line
17
Models/Results
Temperature profiles in center of work-piece
18
Models/Results
Temperature transverse
Profiles of viscosity
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Models/Results/Summary

• 215 rmp/11.3 cm/min
• Supplied temperature BCs accounted for
  approximately 600 watts of heat generation to
  work-piece.
• With viscous heat generation included, it
  accounted for 30 of the total energy generated.
• With adiabatic surfaces specified along the tool
  and top surface, viscous dissipation accounts for
  about 400 watts of heat generation

20
Models/Results/Summary, cont

• 215 rmp/11.3 cm/min
• Flow regime in the vicinity of the tool is
  strongly dependent upon subtle changes in
  material properties.
• The location of the heat generation is of
  comparable importance to the magnitude of the
  heat generated

21
Models/Results/Summary, cont

• 1200 rmp/25.4 cm/min
• With viscous dissipation included, results show
  temperature supplied BCs unrealistic.
• With supplied surface temperature BCs, viscous
  heat generation rate reaches 1.7 Kw resulting in
  reversed heat flow into the pin and shoulder.
• With adiabatic tool surfaces and work-piece top
  surface, viscous heat generation rate reaches
  1.85 Kw.

22
Conclusions

• CFD models of FSW can be used to estimate process
  phenomena.
• Thermal BCs obtained from uncoupled conduction
  calculations are not appropriate and produce
  unrealistic results in applications where viscous
  heat generation dominates.
• Better constitutive relationships are needed.
• It appears that both viscous and frictional
  heating are important, with frictional heating
  dominating at low rotational speeds and viscous
  heat at high rotational speeds.