Constitutive Model of Friction Stir Weld with Consideration of its Inhomogeneous Mechanical Properties

• Published in: Chinese journal of mechanical engineering Vol. 29; no. 2; pp. 357 - 364
• Main Authors: Zhang, Ling, Min, Junying, Wang, Bin, Lin, Jianping, Li, Fangfang, Liu, Jing
• Format: Journal Article
• Language: English
• Published: Beijing Chinese Mechanical Engineering Society 01-03-2016; Springer Nature B.V; School of Mechanical Engineering, Tongji University, Shanghai 201804, China%Chair of Production Systems, Ruhr-University Bochum, Bochum 44780, Germany
• Edition: English ed.
• Subjects: Accuracy; Advanced Manufacturing Technology; Computer simulation; Constitutive models; Diamond pyramid hardness; Digital imaging; Electrical Machines and Networks; Electronics and Microelectronics; Engineering; Engineering Thermodynamics; Finite element method; Friction stir welding; Heat affected zone; Heat and Mass Transfer; Instrumentation; Machines; Manufacturing; Mathematical models; Mechanical Engineering; Mechanical properties; Model accuracy; Power Electronics; Processes; Stress-strain curves; Stress-strain relationships; Tensile tests; Theoretical and Applied Mechanics; 力学性能; 单轴拉伸试验; 应力-应变曲线; 搅拌摩擦焊接; 数字图像相关; 本构模型; 机械性能; 非均匀; inhomogeneous mechanical property; friction stir welding; constitutive model; tailor welded blanks
• ISSN: 1000-9345; 2192-8258
• DOI: 10.3901/CJME.2016.0105.002

In practical engineering, finite element（FE） modeling for weld seam is commonly simplified by neglecting its inhomogeneous mechanical properties. This will cause a significant loss in accuracy of FE forming analysis, in particular, for friction stir welded（FSW） blanks due to the large width and good formability of its weld seam. The inhomogeneous mechanical properties across weld seam need to be well characterized for an accurate FE analysis. Based on a similar AA5182 FSW blank, the metallographic observation and micro-Vickers hardness analysis upon the weld cross-section are performed to identify the interfaces of different sub-zones, i.e., heat affected zone（HAZ）, thermal-mechanically affected zone（TMAZ） and weld nugget（WN）. Based on the rule of mixture and hardness distribution, a constitutive model is established for each sub-zone to characterize the inhomogeneous mechanical properties across the weld seam. Uniaxial tensile tests of the AA5182 FSW blank are performed with the aid of digital image correlation（DIC） techniques. Experimental local stress-strain curves are obtained for different weld sub-zones. The experimental results show good agreement with those derived from the constitutive models, which demonstrates the feasibility and accuracy of these models. The proposed research gives an accurate characterization of inhomogeneous mechanical properties across the weld seam produced by FSW, which provides solutions for improving the FE simulation accuracy of FSW sheet forming.