Title page for ETD etd-05062002-100056


Type of Document Master's Thesis
Author Francis, Justin David
Author's Email Address francisj@gdls.com
URN etd-05062002-100056
Title Welding Simulations of Aluminum Alloy Joints by Finite Element Analysis
Degree Master of Science
Department Aerospace and Ocean Engineering
Advisory Committee
Advisor Name Title
Johnson, Eric R. Committee Chair
Gürdal, Zafer Committee Member
Kapania, Rabesh K. Committee Member
Stoumbos, Thomas Committee Member
Keywords
  • GMAW
  • weld simulation
  • aluminum
  • finite element analysis
Date of Defense 2001-07-20
Availability unrestricted
Abstract
(ABSTRACT)

Simulations of the welding process for butt and tee joints using finite element analyses are

presented. The base metal is aluminum alloy 2519-T87 and the filler material is alloy 2319. The

simulations are performed with the commercial software SYSWELD+®, which includes moving

heat sources, material deposit, metallurgy of binary aluminum, temperature dependent material

properties, metal plasticity and elasticity, transient heat transfer and mechanical analyses. One-way

thermo-mechanical coupling is assumed, which means that the thermal analysis is completed first,

followed by a separate mechanical analysis based on the thermal history.

The residual stress state from a three-dimensional analysis of the butt joint is compared to

previously published results. For the quasi-steady state analysis the maximum residual longitudinal

normal stress was within 3.6% of published data, and for a fully transient analysis this maximum

stress was within 13% of the published result. The tee section requires two weld passes, and both a

fully three-dimensional (3-D) and a 3-D to 2-D solid-shell finite elements model were employed.

Using the quasi-steady state procedure for the tee, the maximum residual stresses were found to be

90-100% of the room-temperature yield strength. However, the longitudinal normal stress in the first

weld bead was compressive, while the stress component was tensile in the second weld bead. To

investigate this effect a fully transient analysis of the tee joint was attempted, but the excessive

computer times prevented a resolution of the longitudinal residual stress discrepancy found in the

quasi-steady state analysis. To reduce computer times for the tee, a model containing both solid and

shell elements was attempted. Unfortunately, the mechanical analysis did not converge, which

appears to be due to the transition elements used in this coupled solid-shell model.

Welding simulations to predict residual stress states require three-dimensional analysis in the

vicinity of the joint and these analyses are computationally intensive and difficult. Although the

state of the art in welding simulations using finite elements has advanced, it does not appear at this

time that such simulations are effective for parametric studies, much less to include in an

optimization algorithm.

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