Optimization of FS Welding Parameters for Improving Mechanical Behavior of AA2024-T351 Joints Based on Taguchi Method
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JMEPEG (2013) 22:2261–2270 DOI: 10.1007/s11665-013-0499-x
Optimization of FS Welding Parameters for Improving Mechanical Behavior of AA2024-T351 Joints Based on Taguchi Method C. Vidal and V. Infante (Submitted October 8, 2012; in revised form January 14, 2013; published online February 20, 2013) In the present study, the design of an experiment technique, the Taguchi method, has been used to optimize the friction stir welding (FSW) parameters for improving mechanical behavior of AA2024-T351 joints. The parameters considered were vertical downward forging force, tool travel speed, and probe length. An orthogonal array of L9 (34) was used; ANOVA analyses were carried out to identify the significant factors affecting tensile strength (Global Efficiency to Tensile Strength—GETS), bending strength (Global Efficiency to Bending—GEB), and hardness field. The percentage contribution of each parameter was also determined. As a result of the Taguchi analysis in this study, the probe length is the most significant parameter on GETS, and the tool travel speed is the most important parameter affecting both the GEB and the hardness field. An algebraic model for predicting the best mechanical performance, namely fatigue resistance, was developed and the optimal FSW combination was determined using this model. The results obtained were validated by conducting confirmation tests, the results of which verify the adequacy and effectiveness of this approach.
Keywords
ANOVA, friction stir welding, Taguchi method
1. Introduction Significant interest has been shown in the use of advanced welding techniques for aircraft structures, particularly given the design and manufacturing benefits they afford over the established mechanical joining methods. While a variety of welding methods have been identified for airframe structures, friction stir welding (FSW) is an important candidate technique that is distinctive in being a low energy, solid-state process (Ref 1). Although the FSW joints have a better quality compared with the fusion techniques, there are still some defects that may arise and which are very sensitive to small variations in process parameters. Typical defects that may arise in FSW joints result from imperfect stir of the materials during the processing, inadequate surface preparation, lack of penetration of the probe, and non-uniform vertical forging forces along the material thickness. Some characteristic FSW defects are lack of penetration (typically addressed as kissing-bond), root flaw (concerning weak or intermittent linking), voids on the advancing side, and second-phased particles and oxidesÕ alignment under the shoulder (Ref 2). Advanced aerospace aluminum alloys have been required to enable high fracture toughness, higher fatigue performance, high formability, and
super plasticity to meet the needs for lower structural weight, higher damage tolerance, and durability (Ref 3). There have been numerous efforts to understand the effect of FSW parameters on material flow behavior (Ref 4, 5), microstructure formation, and mechani
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