The Quality Monitoring of Friction Stir Welding

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The Quality Monitoring Of Friction Stir Welding

In recent years, the rapid development of electric vehicles has made the technology of friction stir welding widely spread. This technology is used in aerospace, automobile, machinery, and other fields, and the most undesirable problem is incomplete welding and internal stress. For the problem of force, the parameters of friction stirring and stirring force are one of the most important factors. How can we obtain the most suitable value and maintain good quality?

Introduction

What Is Friction Stir Welding?

Friction stir welding (FSW) is a joining process technology originally invented by the Welding Institute in the United Kingdom in 1991. Different from traditional welding methods, this method can form defect-free high joining quality and obtain good welding quality also mechanical properties.

The welding of FSW is when a cylinder tool or other shape (with a spiral cylinder) is inserted into the joint of the workpiece, and the high-speed rotation of the welding head rubs with the welding material so that the temperature of the material in the joint increases then softens the material, and at the same time, the material is subjected to friction stir welding to complete the welding.

This technology is especially suitable for joining low-melting non-ferrous metals and mixed joints, such as aluminum, magnesium, copper, titanium or steel, and other difficult-to-weld materials.

Applications and Challenges of FSW

In the past, the technology of friction stir welding was little known. It was not well-known until the vigorous development of electric vehicles that it slowly spread in the industry. Generally, such technology is used in the manufacture of large aerospace parts such as rockets and civil aviation aircraft. The purpose is to bond metal plates together, and the battery module in the electric vehicle needs to be well protected, and it needs to be welded to the chassis through the aluminum plate as the battery shell. No matter what kind of workpiece is welded, the problems of incomplete welding and internal stress are not what we expect. Therefore, the parameters and stirring force of friction stirring have to be well controlled.

Monitoring Friction Stir Welding with Different Parameters Using Smart Tool Holder

Through the combination of the smart tool holder and the friction welding stirring rod, it is possible to sense the huge lateral force while stirring, the balance of the axial force, the torsional stability, and the temperature curve that are most relevant to the internal stress. Quickly obtain the optimum parameters for friction stirring and adapt them to every material, thickness, and shape.

There are two sets of parameters in the picture on the right. The vf1000 is very stable under the numerical monitoring of temperature and torque, but the instability of the axial force may cause the problem of uneven stress at the welding point, while the vf800 has a slightly higher temperature and a longer machining time. , but the axial stability is the best, which can meet the stress requirements of barrel workpieces for the aerospace industry and electric vehicle chassis.

Temperature

Axial force

Torque

Monitoring Quality of FSW

The smart tool handle can quickly detect the rigidity of the friction stirring lateral force. We can see the four parameters in the figure below. The larger the force, the more deviated from the center point on the polar coordinate diagram, which means the displacement change of the overall machining rigidity of the machine tool. This displacement change can result in the reduced spindle bearing life, high-temperature rise, loss of accuracy, and ultimately uneven stress on the weld. This experiment can quickly understand the parameters that the whole machine tool can load, and can also immediately evaluate the number and thickness of aluminum sheets that can be welded, so as to achieve the quality monitoring of the overall FSW.

Main image photo by Machsync

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