50
A. K. Choudhary and R. Jain
Elangovan et al. [16] have compared different tool pin profiles in terms of heat
generation and material flow. Pin profiles including cylindrical, tapered cylindrical
(conical), square, triangle, and threaded cylindrical shapes (as shown in Fig. 2.6)
with shoulder diameter of three different dimensions i.e. 15, 18, and 21 mm have
been studied. It was found that the defect-free stir region after welding is dependent
on the shoulder diameter and tool pin profile.
Pin profile controls the mechanical properties of weld formed after the FSW
process. The joint made from a straight cylindrical pin and conical pin profile with
an 18 mm shoulder diameter resulted in defect-free weld. It has shown better properties as compared to the other two shoulder diameters. Also, welding performed by
the square and triangular pin profile with an 18 and 21 mm shoulder diameter resulted
in the defect-free weld. Square pin profile produced a weld efficiency of about 95%.
Also, the tool with an 18 mm shoulder diameter produced 190 MPa of weld strength
which was higher as compared to the other two. The reason could be because of the
optimum heat generation for 18 mm shoulder. As higher heat generation may lead
to slipping of tool shoulder on the material surface leading to insufficient material
flow. The square and triangular pins have flat faces and that is responsible for generating dynamic pulsating effect. The better material flow was produced by triflute
pin followed by the square and cylindrical pin. Trilflute and cylindrical pin offer
the maximum and minimum dynamic area, respectively among the above three-pin
profiles. So, the highest and lowest plastic deformation was produced by triflute and
cylindrical pin, respectively. Also, the triflute pin has the highest bulk material transportation efficiency along with shearing action. Triflute pin also recorded high peak
hardness [36].
The correlation is associated with the dynamic volume and static volume governs
of the material flow path of the plasticized weld material for different pin profiles.
Material displacement takes place due to the rotating tool from the leading edge to
the trailing edge. The triangular and square pin having flat faces produces a dynamic
pulsating action during the stirring of the material. The pulsating action is absent in
other pin profiles like cylindrical and tapered ones [16]. Pulsating action results in
more homogenous material flow and localized mixing of soft plasticized material in
the stir zone, better material transportation takes place due to which pore, voids, and
tunnel defects are also eliminated [28].
The selection of the shoulder diameter and its profile is another important parameter as it is responsible for the generation of heat and material holding. Three
commonly used shoulder geometries are concave, convex, and flat surface. The
shoulder profile should be able to contain the plasticized material to avoid/reduce
flash formation. The viscous flow capacity of the material depends on the extent of
surface area and shoulder geometry, which is in contact with the workpiece. Flat
shoulders are simple in design and easy to manufacture. The tool shoulder with a
flat surface cannot hold the material efficiently beneath it and leads to the formation
of flash [32]. For efficient welding, the flat shoulder should be accompanied by tilt
angle. Concave shoulder performs better to contain the material as compared with the
flat shoulder. The concavity of the shoulder acts as a reservoir for the material beneath
it and does necessary forging action on the material. While moving forward the tool
A. K. Choudhary and R. Jain
Elangovan et al. [16] have compared different tool pin profiles in terms of heat
generation and material flow. Pin profiles including cylindrical, tapered cylindrical
(conical), square, triangle, and threaded cylindrical shapes (as shown in Fig. 2.6)
with shoulder diameter of three different dimensions i.e. 15, 18, and 21 mm have
been studied. It was found that the defect-free stir region after welding is dependent
on the shoulder diameter and tool pin profile.
Pin profile controls the mechanical properties of weld formed after the FSW
process. The joint made from a straight cylindrical pin and conical pin profile with
an 18 mm shoulder diameter resulted in defect-free weld. It has shown better properties as compared to the other two shoulder diameters. Also, welding performed by
the square and triangular pin profile with an 18 and 21 mm shoulder diameter resulted
in the defect-free weld. Square pin profile produced a weld efficiency of about 95%.
Also, the tool with an 18 mm shoulder diameter produced 190 MPa of weld strength
which was higher as compared to the other two. The reason could be because of the
optimum heat generation for 18 mm shoulder. As higher heat generation may lead
to slipping of tool shoulder on the material surface leading to insufficient material
flow. The square and triangular pins have flat faces and that is responsible for generating dynamic pulsating effect. The better material flow was produced by triflute
pin followed by the square and cylindrical pin. Trilflute and cylindrical pin offer
the maximum and minimum dynamic area, respectively among the above three-pin
profiles. So, the highest and lowest plastic deformation was produced by triflute and
cylindrical pin, respectively. Also, the triflute pin has the highest bulk material transportation efficiency along with shearing action. Triflute pin also recorded high peak
hardness [36].
The correlation is associated with the dynamic volume and static volume governs
of the material flow path of the plasticized weld material for different pin profiles.
Material displacement takes place due to the rotating tool from the leading edge to
the trailing edge. The triangular and square pin having flat faces produces a dynamic
pulsating action during the stirring of the material. The pulsating action is absent in
other pin profiles like cylindrical and tapered ones [16]. Pulsating action results in
more homogenous material flow and localized mixing of soft plasticized material in
the stir zone, better material transportation takes place due to which pore, voids, and
tunnel defects are also eliminated [28].
The selection of the shoulder diameter and its profile is another important parameter as it is responsible for the generation of heat and material holding. Three
commonly used shoulder geometries are concave, convex, and flat surface. The
shoulder profile should be able to contain the plasticized material to avoid/reduce
flash formation. The viscous flow capacity of the material depends on the extent of
surface area and shoulder geometry, which is in contact with the workpiece. Flat
shoulders are simple in design and easy to manufacture. The tool shoulder with a
flat surface cannot hold the material efficiently beneath it and leads to the formation
of flash [32]. For efficient welding, the flat shoulder should be accompanied by tilt
angle. Concave shoulder performs better to contain the material as compared with the
flat shoulder. The concavity of the shoulder acts as a reservoir for the material beneath
it and does necessary forging action on the material. While moving forward the tool