Abstract
This work focuses on the influence of the rotational and travel speed on the strength of AA 2024 T3 friction stir welded lap joints. Tensile tests were carried out on minispecimens extracted from different welding zones. A central composite design was applied to identify the relative importance of the variable factors’ effects and their interaction on yield/ultimate strength and elongation for both the heat affected-zone (HAZ) and nugget zone. Surface methods and gradient algorithms were used to optimize the yield strength of the joints. Shear and microhardness tests were executed to achieve a more complete mechanical characterization.
Highlights
Many studies of experimental strategies prove that the correct experimental strategy for problems involving more than one factor and data points affected by experimental errors must be taken from design of experiments (DOE) techniques if the aim is to remove objective results from experimental data [14]. ese techniques allow maximum conclusive information to be drawn from minimum work, time, energy, money, or other limited resources
Neither curvature could be considered significant. e weighted ANOVA related to the experimental data of yield strength is shown in Table 4. e regression model has been reduced by removing the interaction effect since a previous analysis proved its negligibility; the value of F related to the interaction effect is 0.09 corresponding to a p value of 0.782
A procedure to optimize the mechanical behaviour of friction stir welded joints was developed. e yield strength was chosen as a factor of interest, and its response was optimized by using a response surface method
Summary
Is specific parameter is the one that mostly influences the process response while keeping fixed the level of the other parameters [10] Such an approach has at least two disadvantages: it lacks objectivity in determining mathematical relations between process inputs and response variables and it lacks efficiency and accuracy in optimizing the surface response through trials [11]. Another experimental strategy is the “one factor per time approach,” wherein the researcher subsequently varies the levels of each factor within its range while keeping fixed at the base level the other factors [12]. Aiming to test separately the tensile strength of HAZ and nugget zone, minispecimens from both these zones were subjected to shear and microhardness tests. e process parameters optimization issue was approached using central factorial design, response surface methods, and gradient algorithms
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