Abstract
The paper presents the results of an analysis of the effect of welding parameters on the load capacity of joints obtained by the refill friction stir spot welding (RFSSW) method. This technology has a prospective application in aerospace and automotive industries, especially for aluminium alloys. The research was conducted for the overlapping joints made of two 7075-T6 aluminium alloy sheets with thicknesses 1.6 mm and 0.8 mm. Strength tests were conducted for two variants of loading the joint. The experiments were conducted according to statistical Hartley’s plan PS/DS-P:Ha3. The welding times t was varied in the range of 1.5 ÷ 3.5 s, the tool plunge depth g in the range of 1.5 ÷ 1.9 mm, and the tool rotational speed n in the range of 2000 ÷ 2800 rpm. For these parameters the analysis of experiment reproducibility, impact significance and adequacy of equations were made. The results of analysis according to the design of the experiment (DOE) indicate that all analyzed parameters have significant influence on the load capacity of joints. The biggest load capacity of joints in the case of the first variant was gained at the maximum spindle speed of 2800 rpm, the minimum tool plunge depth of 1.5 mm and welding time of 1.5 s. For the second variant, the maximum load capacity of joints was gained at the spindle speed of 2400 rpm, tool plunge depth of 1.5 mm and welding time of 2.5 s.
Highlights
Refill friction stir spot welding and using refill friction stir spot welding (RFSSW) to fill craters is becoming one of the most commonly used methods of spot welding in the automotive [1, 2] and aviation [1, 3] industries
The joints that were tested for pure shear through the use of a special device show a 8-20% higher load carrying capacity compared to samples that underwent a simple shear strength test (Fig. 3)
In the second case the welds were torn out of the thinner sheet metal, (Fig. 6a, 9a, 10a) and (Figs. 4b-9b, Figs. 12b-14b). This demonstrates the essential value of one the parameters, tool plunge depth g = 1.7 mm, which affect this type of joint
Summary
Refill friction stir spot welding and using RFSSW to fill craters is becoming one of the most commonly used methods of spot welding in the automotive [1, 2] and aviation [1, 3] industries. An example of using this technology could be welding the fuselage covering of an aircraft The attractiveness of this joining method results from technological-economical benefits like high production output and welding process stability that ensures high repeatability simplifying the automation of the process. Another benefit would be the ability of joining materials with different properties and better safety conditions in the workplace, when compared to traditional welding methods [4, 8, 9, 10]. This technique can be used to joint different types of materials like composites [11, 12], thermoplastics [13, 14] and non-weld-able alloys [4, 5]
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