Experimental and numerical investigation on friction drilling of difficult-to-machine materials
Friction drilling is a non-conventional hole-making process that utilizes a rotating conical drilling tool to penetrate workpiece and create a hole by forming a bushing without generating chip. In metallurgy, difficult-to-machine materials are defined as materials which have great toughness, high...
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| Format: | Thesis |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/77687/1/FK%202019%2047%20ir.pdf |
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| Summary: | Friction drilling is a non-conventional hole-making process that utilizes a rotating
conical drilling tool to penetrate workpiece and create a hole by forming a
bushing without generating chip. In metallurgy, difficult-to-machine materials are
defined as materials which have great toughness, high work-hardening and low
thermal conductivity. Since the difficult-to-machine materials are receiving
increasing attention in extreme applications, friction drilling offers a great
potential for product fabrication. However, the major challenge of friction drilling
on difficult-to-machine materials is the difficulty of machining that leads to poor
friction drilling performance and short tool life. In this study, the friction drilling on
difficult-to-machine materials of stainless steel AISI304, titanium alloy Ti-6Al-4V
and nickel-based alloy Inconel718 using drilling tool of tungsten carbide was
experimentally and numerically investigated. Experimental results revealed that
the thermal and mechanical properties of work-materials, spindle speed and feed
rate have great influence on the formation of bushing and tool life. To achieve
maximum number of acceptable drilled-holes, the optimum process parameters
for AISI304 are spindle speed 1000 rpm and feed rate 105 mm/min, for Ti-6Al-
4V are spindle speed 1000 rpm and feed rate 145 mm/min, and for Inconel718
are spindle speed 1500 rpm and feed rate 145 mm/min. The maximum frictional
heating is generated at bushing completion stage, where the conical region of
drilling tool is contacted to drilled hole-wall. The higher thrust force was occurred
in initial contact between drilling tool and workpiece, and consequently the
circular grooves and work-material adhesion have proven that abrasive and
adhesive wear occurred on center and conical regions of drilling tool,
respectively. The maximum abrasive wear, adhesive wear and oxidative wear
are occurred on drilling tools which drilled AISI304, Ti-6Al-4V and Inconel718,
respectively. The developed numerical model can well represent the real
process of friction drilling, and stress and temperature distributions on workpiece
and drilling tool. It also can effectively demonstrate the heating distribution on workpiece, material softening and bushing formation. The numerical results
indicated that severe stress occurs at the tool contact surface and adjacent
region in the initial penetration. The inverse relationship between stress and
temperature demonstrate the phenomenon of frictional heating and softening of
the work-material in friction drilling which forms the bushing. Furthermore, the
high plastic strain occurs on the hole-wall, which is the contact surface between
drilling tool and work-material and it depends on the tool movement along the
drilling path. The main contribution of this study is determining the effect of
process parameters on drilling tool performance, bushing formation quality,
thrust force and tool wear for friction drilling of difficult-to-machine materials with
approach to improve friction drilling performance and reduce tool wear. Moreover
the developed finite element modeling can provide a prediction for friction drilling
process. In overall, this work demonstrated the behaviors of chip-less friction
drilling on difficult-to-machine materials that can offer a great potential for a new
product design and manufacturing. |
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