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A review of numerical analysis of friction stir welding

Friction stir welding (FSW), a highly efficient solid-state joining technique, has been termed as “green” technology due to its energy efficiency and environment friendliness. It is an enabling technology for joining metallic materials, in particular lightweight high-strength aluminum and magnesium alloys which were classified as unweldable by traditional fusion welding. It is thus considered to be the most significant development in the area of material joining over the past two decades. Friction stir processing (FSP) was later developed based on the basic principles of FSW. FSP has been proven to be an effective and versatile metal-working technique for modifying and fabricating metallic materials. FSW/FSP of aluminum alloys has prompted considerable scientific and technological interest since it has a potential for revolutionizing the manufacturing process in the aerospace, defense, marine, automotive, and railway industries. To promote widespread applications of FSW/FSP technology and ensure t...

Recent Advances in Friction Stir Welding/Processing of Aluminum Alloys: Microstructural Evolution and Mechanical Properties

Thermo-mechanical simulation of friction stir welding can predict the transient temperature field, active stresses developed, forces in all the three dimensions and may be extended to determine the residual stress. The thermal stresses constitute a major portion of the total stress developed during the process. Boundary conditions in the thermal modeling of process play a vital role in the final temperature profile. The heating and cooling rates with the peak temperature attained by the workpiece determine the thermal stress. Also, predicting realistic peak temperature becomes important as the operating temperature at the interface of tool-workpiece is very close to the solidus temperature of the aluminum workpiece. The convection heat-transfer coefficients of the surfaces exposed to air can be theoretically determined using Newton's law of cooling. Contact conductance depends on the pressure at the interface and has a non-uniform variation. The actual pressure distribution along the interface is dependent on the thermal stress from local temperature and non-linear stress–strain state. Therefore, applying an adaptive contact conductance can make the model more robust for process parameter variations. A finite element thermo-mechanical model with mechanical tool loading was developed considering a uniform value for contact conductance and used for predicting the stress at the workpiece and backplate interface. This pressure distribution contours are used for defining the non-uniform adaptive contact conductance used in the thermal model for predicting the thermal history in the workpiece. The thermo-mechanical model was then used in predict stress development in friction stir welding.

https://www.smu.edu/~/media/Site/Lyle/RCAM/Publications/Thermo-mechanical%20model%20with%20adaptive%20boundary%20conditions%20for%20friction%20stir%20welding%20of%20Al6061.ashx

Thermo-mechanical model with adaptive boundary conditions for friction stir welding of Al 6061

Application of ultrasonic vibrations in welding and metal processing: A status review

Friction stir processing – State of the art

Friction stir welding (FSW), a new solid-state welding technology invited in the early 1990s, enables us weld aluminum alloys and titanium alloys etc. The processing of FSW, the microstructure in FSW alloys and the factors influencing weld quality are introduced. The complex factors affecting the properties are researched.

Friction stir welding of aluminum alloys

Ultrasonic-assisted friction-stir welding is a new solid-state metal welding technology, based on friction-stir welding, in which weld performance is improved through application of ultrasound during welding. In this study, a model for the temperature field in 1.8 mm 2024 aluminum alloy is built based on computational fluid dynamics and elastic-plastic mechanics theory. Result show the impact of the ultrasound’s vibrations on the temperature field is less obvious at lower welding speeds. However, at higher welding speeds, it can provide the additional heat to keep sufficient welding temperature. The numerical results are compared with optical micrographs in order to validate the numerical models. Good agreement is obtained.

A study of the temperature field during ultrasonic-assisted friction-stir welding

Friction stir welding(FSW)of aluminum alloy usually results in a special "funnel shaped" temperature field,which makes obvious difference of microstructure properties in the direction of weld seams.In order to get better properties of welded joints,ultrasonic stir hybrid welding technology has been put forward in this paper,which concentrates the ultrasonic energy in deep weld seams through the stirring pin.Thickness of 2.5 mm 2219 aluminum alloy sheets has been adopted and welded by the two technologies mentioned above in this experiment,microstructure and mechanical properties of weld are analyzed and compared as well.Result shows that the weld joints of 2219 aluminum welded by the two technologies are both with good appearance and defect-free in the inner,and ultrasonic stir hybrid welding obviously has better mechanical properties.

He Diqiu

Papers

Friction stir welding of aluminum alloys

A study of the temperature field during ultrasonic-assisted friction-stir welding

Study on ultrasonic stir hybrid welding of aluminum alloy

Test analysis for ultrasonic assisted friction stir welding of aircraft skin aluminium alloy