Its tear on the top portion when the tool rotates and only the another base metal underwent the load

In FSW of thin sheet there are some points that you have to consider.

1. balance between rotational speed and travel speed of the tool.

it means that you have to control the process temperature. there is interaction effect between these two parameters. in your project there is not enough material to flow(as Mostafa Saboktakin said)

2. material: you want to FSW dissimilar material such as aluminum to steel.

solidus temperature of steel and aluminum is different. consider that.

it seems in your welding process the temperature for Al alloy is high.

it seem its better to increase the travel speed, decrease the warm up time(in the start of FSW) and for rotational speed you have to try because you have to control temperature for steel and Aluminum.

3. Tool. shape of the tool is important

4.load. try not to running the process with high load

What will the load that i should give and suggest any tool shape exactly

For tool, never use threaded pin in thin sheet lap joint, i tried that, it did not work

Tilt angle on different degrees may give some solutions for this problem

Venu Jaiganesh, there is a significant interactions between all these parameters like rotational and travel speed, tilt angle and ..., , we must understand the process

I have to test mechanical proprety with a FEM software after the induction welding, but I don't understand how I can calculate the new allowable stress, I know that there is a change about interlaminar shear strenght, but I don't know how I can estimate this change and if there is also a change of propreties in Others directions.. The material is PPS/carbon fiber.

Venu Jaiganesh, we did some investigations on Al/ Cu joints with a thickness of 0,8mm. The limit we figured out was 0,5mm, but it depends on the welding system. We use a position controlled milling maschine. With force control you may weld 0,3mm thick sheets. Furthermore we weld Al / Steel sheets with 0,8mm with a displacement of 0,1mm into aluminium.

We some work in FSW of thin plates. Plates distortion may be bigger problem. But it is not difficult producing similar welds (Al, Cu, Zn...) or even dissimilar aluminium welds.

Many researchers have reported successful friction stir welding on sheets less than 2 mm. You are requested to consult those articles. For sheets of thickness 2 mm, what is most crucial is the selection of feasible tool pin dimensions, specially the tool pin length. As the thickness is 2 mm, surely the pin length must be less than that or at most 2 mm. Sheets with this thickness can be tried to join using pin less tool which are available. And regarding your question that top plates come out when attempted lap joint. This might be due to improper clamping of the work pieces or improper selection of weld line. Moreover, dissimilar alloy joint using FSW is challenging due to many factors and beyond the scope of this blog. Recent articles are available which can be refered.

FSW of thin sheets (going up to 0.3 to 0.5mm) are quite commonplace. The problem you are referring to of the Al sheet coming out while welding steel in an overlap joint would be due to lack of penetration of the pin and insufficient heat generation which is causing this issue. Please ensure that the pin penetrates sufficiently. Also, if there is a thick oxide layer on the steel or a Ni coating, you will not be able to get a bond. 

We did managed to weld 1.5mm thick aluminium sheet in butt joint configuration but for some welding parameters. We had limited selection of welding parameters as we ran on conventional milling machine. We will try for some other welding parameters in future and utilizing cnc milling machine. We had a proper jig and tool for this task. 

Hi everyone, can you put some light on the topic that, that if i wish to do friction stir welding on thin aluminium plates without tool pin , then what would be your reaction. If any one tried this before kindly share your experience with me so that we do some better output. 

I've seen the paper presented by Dulce Rodrigues (she was the first to respond to this question thread) on Overlap joining of very thin sheets presented at the 10th International FSW symposium - I think people who want more practical experience on thin sheet FSW joining can write to her.

Personally, I've worked over the last four years with Juergen Silvanus (FSW specialist & expert from Airbus Group) & through projects we've done for several customers, can conclude that FSW of thin sheet metal is possible but is best done on machines (or robots) that have a force control mode of operation and not just the typical program a CNC machine runs. It is possible to add a macro to your existing machine to ensure it works in a force control mechanism (i.e. ensures constant downward force) to ensure good consolidation. If anyone needs more information on how to do this, feel free to contact me individually.

If you are trying out thin sheet metals for the first time, you should not try to weld very fast in overlap (meaning speeds should be restricted to under 0.5m/min). 

Another key point to note is the direction of rotation of the tool and the direction of travel. Selecting the wrong combination for a dissimilar material overlap joint can lead to a hook effect in the weld (which you will see in your weld micrographs). This obviously reduces the strength of the joint. Unfortunate it can never be completely eliminated & it is desirable to reduce it as much as possible.

According to me, if friction stir welding is to done by means off robots that it may lead to costly process. So in order to make it cost-effective process there may be some method which should be applied  n daily practice FSW for similar as well as dissimilar process of FSW. I just wanted to know that if some type of coating may apply on to the workpiece then whether this problem may rectified or not. Kindly give some suggestions on this. 

Hi Tanvir, for thin sheet FSW it is always advisable to position your fixtures & clamps on the workpieces as close to the joint line as possible (this would take partly take care of the tearing effect on sheet thicknesses below 1mm). The backing plate should have a thick oxide layer so that the sheets being Friction stir welded don't stick to the backing plate. Maintain a welding speed of less than 0.5m/min (but this may vary depending on the grade of steel or aluminium being welded) and ensure that your penetration depth is set perfectly (for both butt & overlap joints) - generally in the labs during a first time set up, this is where most of your time should be spent. Finally for pin choice, the shoulder diameter should be as minimal as possible and you can also use a cylindrical pin (with no threading or at most very minimal threading) - The pin diameter also doesn't need to be taper down. 

As I've mentioned earlier, for overlap joints of dissimilar materials (e.g. Al joined to Steel below), then make sure that the steel has no coating of any sort and has no oxide layer (any coating like Zinc will prevent a good joint).

I hope this helps.

Yes very difficult the gap between the tool and work piece was very less and also the adjustment with the machine table with fixture was less. The computer assisted machine will make it but the conventional machine with manual adjustments need more time. Taking the above issues it is difficult to weld. 

Actually no, thanks to recent development in Micro Friction Stir Welding process which helps to Friction Stir Weld very thin sections upto 1mm thickness. I have attached a research paper for your reference.