Abstract
In friction stir welding (FSW), many defects (such as kissing bond, incomplete penetration, and weak connection) easily occur at the root of the welded joint. Based on the Levy–Mises yield criterion of the Zener–Hollomon thermoplastic constitutive equation, a 3D thermal–mechanical coupled finite element model was established. The material flow behavior and the stress field at the root area of a 6 mm thick 2024-T3 aluminum alloy FSW joint were studied. The influence of pin length on the root flaw was investigated, and the formation mechanism of the “S line” defects and non-penetration defects were revealed. The research results showed that the “S line” defect forms near the bottom surface of the pin owing to the insufficiently mixed material from the advancing side (AS) and retreating side (RS) near the weld center. The non-penetration defect forms near the bottom surface of the workpiece owing to the insufficient driving force to make the material flow through the weld center. With the continual increase of pin length, the size of the “S line” defect and non-penetration defect reduces, and finally, the defect-free welded joint can be obtained with an optimized suitable length of the pin in this case.
Highlights
Friction stir welding (FSW) is a novel solid phase bonding technique developed by The WeldingInstitute (TWI) in 1991 [1]
Weak connection and non-penetration defects at the root of the weld have seriously affected the by the the root of the weld and the formation mechanism of weak connection defects were studied quality of the weld, but the existing studies have not revealed the formation mechanism of defects numerical simulation method, the influence of different tool pin lengths on the plastic metal flow at the root of the weld from the flow mechanism, and there is no in-depth study on the mechanism behavior of at eliminating the root ofdefects the weld was thepin
In thisreduce model, the workpieceamount grid is divided into twothe types of grid: accuracy, free quadrilateral order to further the calculation while ensuring calculation only thegrids grid used for welding plates, and free triangular grids used for the area around the stirring tool
Summary
Friction stir welding (FSW) is a novel solid phase bonding technique developed by The Welding. Weak connection and non-penetration defects at the root of the weld have seriously affected the by the the root of the weld and the formation mechanism of weak connection defects were studied quality of the weld, but the existing studies have not revealed the formation mechanism of defects numerical simulation method, the influence of different tool pin lengths on the plastic metal flow at the root of the weld from the flow mechanism, and there is no in-depth study on the mechanism behavior of at eliminating the root ofdefects the weld was thepin. At the root ofjoint the weld the formation mechanism of weak connection defects were studied by the numerical simulation method, the influence of different tool pin lengths on the plastic metal flow. Modelsbehavior at the root of the weld was investigated, and the optimized suitable length of the pin with a non-defects welded joint was identified
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