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P. Sarkar et al.
Shoulder: Shoulder is the part of the tool that is in contact with the workpiece surface.
This part of the tool generates the maximum amount of frictional heat. For a certain
plunge depth (defined later), the shoulder is also responsible for mixing in the top
part of the workpiece material.
Pin: It is a small portion that protrudes from the shoulder. During welding, this part
of the tool is completely inside the materials to be joined. The pin plastically deforms
the material due to its rotation, generating additional heat.
Leading edge: As the name suggests, the leading edge is the edge ahead of the pin
along the traverse direction.
Trailing edge: It is the edge of the parts to be joined which is behind the pin along
the traverse direction.
During welding, the material moves to the trailing edge from the leading edge of
the tool. This material is further compressed by the shoulder and is pushed into the
hole created by the pin. Hence, a perfect joint is achieved.
Advancing side (AS): It is the side of the parts to be welded, where the direction of the
tangential component of the tool rotational speed is similar to that of the traversing
speed.
Retreating side (RS): The side of the parts to be welded, where the direction of the
tangential component of the tool rotational speed is opposite to that of the traversing
speed.
Plunge depth (PD): The depth of the shoulder up to which it is inserted into the
workpiece is called the plunge depth. The plunge depth has different values depending
on the material and thickness of plates to be welded.
Tool tilt angle (α): For better mixing of the material and purposefully generate more
heat on the high melting point material side during dissimilar material welding, the
spindle of the FSW machine is tilted to a particular value. The angle by which the
spindle is tilted from the line normal to the weld line is called the tool tilt angle.
Axial force (F z ): F z is the component of the force generated due to the resistance
offered by the workpiece material, which acts perpendicular to the weld traverse
direction. F z is the maximum during the plunging stage as the resistance offered
by unsoftened material at room temperature is the highest at that stage. F z further
reduces with the softening of the material.
4.1.5 Important Parameters in FSW
The following process parameters have a vital role in controlling weld quality. For
a high-quality weld with good strength, selection of suitable parameters is crucial.
The parameters and their effects can be understood from Fig. 4.4.
P. Sarkar et al.
Shoulder: Shoulder is the part of the tool that is in contact with the workpiece surface.
This part of the tool generates the maximum amount of frictional heat. For a certain
plunge depth (defined later), the shoulder is also responsible for mixing in the top
part of the workpiece material.
Pin: It is a small portion that protrudes from the shoulder. During welding, this part
of the tool is completely inside the materials to be joined. The pin plastically deforms
the material due to its rotation, generating additional heat.
Leading edge: As the name suggests, the leading edge is the edge ahead of the pin
along the traverse direction.
Trailing edge: It is the edge of the parts to be joined which is behind the pin along
the traverse direction.
During welding, the material moves to the trailing edge from the leading edge of
the tool. This material is further compressed by the shoulder and is pushed into the
hole created by the pin. Hence, a perfect joint is achieved.
Advancing side (AS): It is the side of the parts to be welded, where the direction of the
tangential component of the tool rotational speed is similar to that of the traversing
speed.
Retreating side (RS): The side of the parts to be welded, where the direction of the
tangential component of the tool rotational speed is opposite to that of the traversing
speed.
Plunge depth (PD): The depth of the shoulder up to which it is inserted into the
workpiece is called the plunge depth. The plunge depth has different values depending
on the material and thickness of plates to be welded.
Tool tilt angle (α): For better mixing of the material and purposefully generate more
heat on the high melting point material side during dissimilar material welding, the
spindle of the FSW machine is tilted to a particular value. The angle by which the
spindle is tilted from the line normal to the weld line is called the tool tilt angle.
Axial force (F z ): F z is the component of the force generated due to the resistance
offered by the workpiece material, which acts perpendicular to the weld traverse
direction. F z is the maximum during the plunging stage as the resistance offered
by unsoftened material at room temperature is the highest at that stage. F z further
reduces with the softening of the material.
4.1.5 Important Parameters in FSW
The following process parameters have a vital role in controlling weld quality. For
a high-quality weld with good strength, selection of suitable parameters is crucial.
The parameters and their effects can be understood from Fig. 4.4.