154
P. Sarkar et al.
is the possible reason for this [52]. Co-relation of the process forces with the channel
processing parameters and channel quality was also studied, and it was concluded
that positioning of the total force applied on the tool decides the formation of channel
in the NZ [53]. It was seen that for a good quality channel that forms at the nugget,
the net resultant force acting upon the pin is positioned between the RS and trailing
side of the tool. Again, from a developed mechanistic model for spindle torque and
specific energy as a function of ω, v and PD, it was found that the decrease in ω and
increase in v both reduce the plastic flow of the material. This is the reason for the
increase in the resistance, thus, the specific energy of the material increases [54].
Similarly, the increment in PD increases the contact area of the pin with the material
thus increases the resistance which ultimately increases the specific energy.
The material flow study during FSC was done on a 6 mm thick Al6061-T6 plate
with the breaking tool technique [55]. The channel cross-section along with the
embedded broken pin is studied with the X-ray Computed Tomography. The authors
have reported that five distinct regions of material flow that are contributed to the
formation of the four walls on the cross-section of the channel. It was observed that
the roof of the channel got formed due to the combined effect of the pin influenced
and the shoulder-influenced regions; whereas, the channel walls formed at the RS,
AS, and the bottom of the channel got formed by the pin influenced-region only.
Later, from the thermo-hydraulic studies by passing de-ionized water through the
channels, it was found that due to the axial wall conduction along the length of
the plate, non-uniform distribution of temperature was recorded [56]. However, in
this study, the experimental value of heat transfer characteristics was found to be
higher as compared to the theoretical values. The presence of surface roughness
inside the channel wall justifies this deviation. The stability of the FSC process
by comparing through force control and position-control modes proved that during
position-control mode the FSC process underwent severe vibrations, and hence was
lesser stable during its traverse [57].
4.6.2 New FSC (NFSC)
A new concept of FSC process was developed in 2011 and is shown in Fig. 4.9. The
main features of this technique are:
• No plunging of the shoulder takes place.
• Tool having threaded pin and special featured shoulder containing striates is used.
• The shoulder touches the workpiece surface. Thus, no initial C is given.
• Due to the presence of features in the shoulder, the material flowing upward is
flown away from the tool and is removed as a self-detachable flash.
In new FSC, the material taken out by the threaded pin from the base of the
workpiece is directly detached as flash. Specially designed shoulder helps to detach
the flashes rather than depositing it under the shoulder. This helps to maintain the
workpiece surface at the pre-processed level that reduces the use of any surface
P. Sarkar et al.
is the possible reason for this [52]. Co-relation of the process forces with the channel
processing parameters and channel quality was also studied, and it was concluded
that positioning of the total force applied on the tool decides the formation of channel
in the NZ [53]. It was seen that for a good quality channel that forms at the nugget,
the net resultant force acting upon the pin is positioned between the RS and trailing
side of the tool. Again, from a developed mechanistic model for spindle torque and
specific energy as a function of ω, v and PD, it was found that the decrease in ω and
increase in v both reduce the plastic flow of the material. This is the reason for the
increase in the resistance, thus, the specific energy of the material increases [54].
Similarly, the increment in PD increases the contact area of the pin with the material
thus increases the resistance which ultimately increases the specific energy.
The material flow study during FSC was done on a 6 mm thick Al6061-T6 plate
with the breaking tool technique [55]. The channel cross-section along with the
embedded broken pin is studied with the X-ray Computed Tomography. The authors
have reported that five distinct regions of material flow that are contributed to the
formation of the four walls on the cross-section of the channel. It was observed that
the roof of the channel got formed due to the combined effect of the pin influenced
and the shoulder-influenced regions; whereas, the channel walls formed at the RS,
AS, and the bottom of the channel got formed by the pin influenced-region only.
Later, from the thermo-hydraulic studies by passing de-ionized water through the
channels, it was found that due to the axial wall conduction along the length of
the plate, non-uniform distribution of temperature was recorded [56]. However, in
this study, the experimental value of heat transfer characteristics was found to be
higher as compared to the theoretical values. The presence of surface roughness
inside the channel wall justifies this deviation. The stability of the FSC process
by comparing through force control and position-control modes proved that during
position-control mode the FSC process underwent severe vibrations, and hence was
lesser stable during its traverse [57].
4.6.2 New FSC (NFSC)
A new concept of FSC process was developed in 2011 and is shown in Fig. 4.9. The
main features of this technique are:
• No plunging of the shoulder takes place.
• Tool having threaded pin and special featured shoulder containing striates is used.
• The shoulder touches the workpiece surface. Thus, no initial C is given.
• Due to the presence of features in the shoulder, the material flowing upward is
flown away from the tool and is removed as a self-detachable flash.
In new FSC, the material taken out by the threaded pin from the base of the
workpiece is directly detached as flash. Specially designed shoulder helps to detach
the flashes rather than depositing it under the shoulder. This helps to maintain the
workpiece surface at the pre-processed level that reduces the use of any surface