Abstract

Nowadays, the manufacturing research efforts have to be conceived in such a way that the product performance criteria are achieved in a lightweighting design concept. Taking these extensions to their extreme, the material properties and the manufacturing solutions have to be considered together in a revolutionary body concept, which should result in an ideal sight to the use of the most performing material in the right place depending on the product requirements. Polymer matrix composites (PMCs) belong to this new material category. The development of joining techniques available to connect PMCs and lightweight alloys has been considered as a key enabling solution in making innovative and sustainable products. The goal of obtaining high joint efficiency must face two main problems, i.e. to deal with the polymeric matrices to get mechanical, physical and chemical compatibilities and to attain or preserve the integrity of reinforcements across the joints customizing the fiber distribution in the joining area. The understanding of current and emerging joining technologies, e.g. the friction stir based techniques, with an optimization of the process parameters needs performant numerical tools to be employed, efficiently. In the work herein proposed, a polymeric base plate was joined to an aluminum alloy part simulating the friction lap joint sequences. Numerical tests have been set by a commercial FE code (DEFORM 2DTM) and a DoE, generated using hypercube sampling, was defined to perform a sensitivity analysis of specific investigated variables on some process outputs.

Abstract

The theoretical model of bobbin tool friction stir welding (BT-FSW) structure and dynamic process is established. Because of the great differences in properties of different materials, the mathematical relationship between material stress and deformation will be expressed based on 3D transient heat conduction equation and J-C constitutive model. The BT-FSW process of 7075 and AZ31B was analyzed by finite element method, and the field distribution, thermal cycle curve and stress distribution characteristics of different welding areas of the welded material were simulated. To predict and control the non-equilibrium distribution of welding temperature and stress field, the influences of different Rotating speed, welding speed, offset and other variables on the BT-FSW process of 7075/AZ31B aluminum magnesium dissimilar alloy were studied comprehensively. Finally, the reliability of the model is proved by fitting the experimental and numerical analysis results. The research results show that the temperature of BT-FSW presents an “hourglass” symmetrical distribution, and the stress distribution on both sides of the plate is uniform when the aluminum alloy is placed on the advancing side, the stirring tool is offset to the aluminum alloy by 2mm, and the rotating speed and welding speed are 700r/min and 180mm/min, respectively.