4 An Application from a Defect—A Friction …
147
2018–26 [39]. With the advent of automation in the welding processes for better weld
quality, precision, increased productivity and decreased labor cost also add to the gain
in popularity of FSW. This is going to play a significant role in the acceptance of the
process in many industries. Moreover, for the various lean initiatives like reduced
bottlenecks and enhanced productivity of the process, the competitors are motivated
to develop the new technology to gain more benefits.
Fixed product types mainly dominate the FSW market. However, due to its
feasibility to join dissimilar material and materials with different thicknesses, the
adjustable product type (where different products can be fabricated) FSW market
will grow soon to a large extent. Again, with the rising demand for high speed and
light-weightiness with higher fuel economy, the automotive sectors are replacing
many steel parts with lightweight options like aluminium, magnesium, (Al, Mg),
etc. by joining them with steel using FSW. Though in 2017, it was seen that the automotive sectors dominated the FSW market share, but it is predicted that the aerospace
sector will grow at a faster rate in the forecast year of 2018–2026 [40]. The reduction
in weight by replacing thousands of rivets with FSW joints in wing and fuselage
components and the process-capability to weld large tanks are the possible reasons
for the growth.
The Asia Pacific Region, being home to large automotive and fabrication industries, generates the highest revenue and has the maximum unit shipment as per the
report in 2017. The region itself generated a 35.1% revenue share of the total FSW
market worldwide [40]. This trend shall prolong in the forecast year also. China
represented the largest individual FSW market in the Asia Pacific, followed by Japan
and India. On the other hand, after the economic recession in North America and
Europe, the automotive, marine, and aerospace industries in these developed countries showed signs of recovery and are adopting state of the art FSW equipment for
more benefits.
4.4 Wormhole Defect—Invention of Friction Stir
Channeling
To make a joint successful by FSW process, there must be adequate heat generation
and appropriate mixing of the softened material. The heat generation in FSW depends
mainly on the process parameters like ω, v and PD. The geometry of the tool also
contributes to the generation of heat and primarily on the deformation and mixing
of the material. It was seen that to avoid flow-related defects the parameters must be
such selected that the temperature creates the stick-slip wiping flow of the material.
Moreover, the flow must ensure that the material flowing from the leading edge of
the pin is exactly balanced with the material deposited at the trailing edge of the pin
[41]. If process parameters are not optimum, heat generation becomes insufficient
or there is inappropriate mixing during the process. This leads to the formation of
a defect called the “tunnel defect” or “the wormhole defect”. It has already been
147
2018–26 [39]. With the advent of automation in the welding processes for better weld
quality, precision, increased productivity and decreased labor cost also add to the gain
in popularity of FSW. This is going to play a significant role in the acceptance of the
process in many industries. Moreover, for the various lean initiatives like reduced
bottlenecks and enhanced productivity of the process, the competitors are motivated
to develop the new technology to gain more benefits.
Fixed product types mainly dominate the FSW market. However, due to its
feasibility to join dissimilar material and materials with different thicknesses, the
adjustable product type (where different products can be fabricated) FSW market
will grow soon to a large extent. Again, with the rising demand for high speed and
light-weightiness with higher fuel economy, the automotive sectors are replacing
many steel parts with lightweight options like aluminium, magnesium, (Al, Mg),
etc. by joining them with steel using FSW. Though in 2017, it was seen that the automotive sectors dominated the FSW market share, but it is predicted that the aerospace
sector will grow at a faster rate in the forecast year of 2018–2026 [40]. The reduction
in weight by replacing thousands of rivets with FSW joints in wing and fuselage
components and the process-capability to weld large tanks are the possible reasons
for the growth.
The Asia Pacific Region, being home to large automotive and fabrication industries, generates the highest revenue and has the maximum unit shipment as per the
report in 2017. The region itself generated a 35.1% revenue share of the total FSW
market worldwide [40]. This trend shall prolong in the forecast year also. China
represented the largest individual FSW market in the Asia Pacific, followed by Japan
and India. On the other hand, after the economic recession in North America and
Europe, the automotive, marine, and aerospace industries in these developed countries showed signs of recovery and are adopting state of the art FSW equipment for
more benefits.
4.4 Wormhole Defect—Invention of Friction Stir
Channeling
To make a joint successful by FSW process, there must be adequate heat generation
and appropriate mixing of the softened material. The heat generation in FSW depends
mainly on the process parameters like ω, v and PD. The geometry of the tool also
contributes to the generation of heat and primarily on the deformation and mixing
of the material. It was seen that to avoid flow-related defects the parameters must be
such selected that the temperature creates the stick-slip wiping flow of the material.
Moreover, the flow must ensure that the material flowing from the leading edge of
the pin is exactly balanced with the material deposited at the trailing edge of the pin
[41]. If process parameters are not optimum, heat generation becomes insufficient
or there is inappropriate mixing during the process. This leads to the formation of
a defect called the “tunnel defect” or “the wormhole defect”. It has already been