Dear Eyob Messele

There are several ways to get approximate value of axial force during both friction stir welding and friction stir spot welding such as using:

1. Linear variable differential transformer (LVDT) sensor as indicated in

Evaluation of depth controller for friction stir welding of copper canisters http://www.skb.com/publication/2492081/Posiva+SKB+Report-08.pdf

2. Load cells such as in https://www.researchgate.net/publication/320164919_Studying_the_Possibility_to_Weld_AA1100_Aluminum_Alloy_by_Friction_Stir_Spot_Welding

and

https://patents.google.com/patent/US20110079339

also there is several machines can supply indicator or table can be used to calculate the axial load

Regards

If the machine is loaded hydraulically then measuring the fluid force acting upon the hydraulic cylinder that applies the load to the tool is simple. If you are using a milling machine then a small load cell placed under the tool with the head locked in Z-axis and applying a load with the table axis until you get the desired load. Then you can easily repeat this with the tool registering with your workpiece. Otherwise you will need to outfit your machine with a sensor such as that described above by Mr. Al-Sabur.

I agree with Dan Rybicki

Dear scholars, thank you very much for your suggestions ! Is anyone suggest me the analytical formula of Axial force in friction stir welding?

I left out one other aspect: If the tool is a "purpose built" friction stir welding machine the forging force axis should have a load sensor built into it to feed load data back to the DAQ regardless if it's hydraulically loaded or electrically loaded (like with a motor driven ball screw type mechanism). Accurate forging load control (real time) is paramount to controlling the process, especially for long duration welds. The load cell method discussed above should only be used for laboratory welds of limited length.

Many years ago I worked on a FSW project using a large, high end 5-axis CNC machining center. It did NOT have "load control" per se (in force) so we decided to "think outside the box" and found we could use the feature in the software that allowed us to monitor the AMPERAGE DRAW on the Z-axis motor. The Z-axis was of course the axis used to apply the load to the FSW tool. It worked quite well - the more load we applied, the higher the amperage draw at the motor. When the load was lowered, the amperage draw went lower. This was our "back door" way to control the forge load. In other words, there was no direct way (or easy way) to translate amperage draw on the motor to axial forging force (load) but the amperage draw VALUE allowed us to control that axis within a range that worked for our application. Improvising proved to be the key to our success!

Good luck!

May be this paper can help you to calculate the axial force in FSW.

Dear Dan Rybicki, thank you very much for your kindness! But in our institute it doesn't have a force measuring device, CNC and FSW machines. So, am using a vertical milling machine as a friction stir welding machine. This machine is a conventional type, it doesn't measure either axial or transversal motion of the tool. Therefore, the only option to measure the axial force is using analytical formula. I have searched the axial force analytical formulas in many FSW books but I couldn't get it. I request kindly, If anyone have knowing this formula, please suggest me.

Have you considered of using Dynamometer? So that the Merchant's circle will help you to determine the two-component forces.

Good Luck!

Dear Getachew Gebreamlak

Thank you very much for sharing your knowledge. A merchant circle diagram is also an option, but we need to measure the axial forces in a device and used a compression type load cell beneath the backing plate.

Thank you once again for your valuable information!