Research Papers

On Crack Control Strategy in Near-Field Microwave Drilling of Soda Lime Glass Using Precursors

[+] Author and Article Information
Nitin Kumar Lautre

Department of Mechanical
and Industrial Engineering,
Indian Institute of Technology Roorkee,
Roorkee, Uttarakhand 247 667, India
e-mail: nfl_123@rediffmail.com

Apurbba Kumar Sharma

Department of Mechanical
and Industrial Engineering,
Indian Institute of Technology Roorkee,
Roorkee, Uttarakhand 247 667, India
e-mail: akshafme@gmail.com

Shantanu Das

Reactor Control Division,
Bhabha Atomic Research Center,
Mumbai 400 085, India
e-mail: shantanu@barc.gov.in

Pradeep Kumar

Office of the Vice Chancellor,
Delhi Technical University,
Bawana Road,
Rohini, Delhi 110 042, India
e-mail: kumarfme@gmail.com

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received January 9, 2015; final manuscript received April 19, 2015; published online June 2, 2015. Assoc. Editor: Bengt Sunden.

J. Thermal Sci. Eng. Appl 7(4), 041001 (Dec 01, 2015) (15 pages) Paper No: TSEA-15-1017; doi: 10.1115/1.4030478 History: Received January 09, 2015; Revised April 19, 2015; Online June 02, 2015

Processing of glass is indeed challenging owing to its chemical passivity; it is prone to cracking while processing through mechanical and thermal modes without appropriate strategies. Near-field microwave drilling is a thermal-ablation based material removal technique of generating high heat flux in the targeted area. Glasses tend to fail quite frequently during this processing owing to thermal stresses (shock). It was therefore important to develop suitable strategies to minimize cracking during this potentially pragmatic process for microdrilling. Accordingly, in the present work, an attempt was made to change the medium of the interface at the target drilling zone through application of seven different surface precursors to influence the local heat-flow characteristics. The cracking behavior of the soda lime glass during microwave drilling in a customized applicator under controlled power input (90–900 W) at 2.45 GHz was investigated. The heat was generated inside the applicator by creating a plasma sphere in the drilling zone through a metallic concentrator. The thermal shock on the glass specimen was found reduced by the combination of a good dielectric precursor and microwave concentration for hotspot formation, which in turn, reduces the cracking/crazing tendency. Trials were carried out while drilling holes on 1.2 mm thick glass plates at various duty cycles (DCs) to study the crack intensity and pattern. The near-field microwave drilling condition was also simulated to obtain the contours of the induced stresses. The results so obtained were compared with the cracking signatures of the experimental outputs; a good correlation could be obtained. It was found that both solid and liquid fluxes as precursor could be effective to control cracking during microwave drilling.

Copyright © 2015 by ASME
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Fig. 1

A schematic of the customized setup used for microwave drilling; insets: (a) epoxy precursor and (b) engine oil precursor on x–y plane

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Fig. 2

Plasma formation and heat generation at the drill tool tip during microwave drilling

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Fig. 3

Meshing pattern of the tool–workpiece interaction zone: (a) without precursor and (b) with precursor

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Fig. 4

Major heat transfer modes in microwave drilling

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Fig. 5

An image of a microwave drilled hole and the cracks developed

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Fig. 6

Typical simulated result of the critically stressed area in the plasma zone on the surface of glass workpiece

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Fig. 7

Copper tool tip: (a) before, (b) after (DC = 0.20) microwave drilling with liquid precursors at low power (90 W), and (c) copper tool tip melted at DC = 1 (900 W) during microwave drilling with precursor

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Fig. 8

Copper tool covered and trapped in microwave drilled cavity (nailing)

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Fig. 9

Microwave cutting of hole through nailing: (a) without precursor and (b) with oil precursor

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Fig. 10

(a) Random crack developed in glass specimen without precursor and (b) critically stressed zone as observed through simulation

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Fig. 11

Simulation of heat distribution on glass surface during microwave drilling; inset: stress distribution in HAZ

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Fig. 12

von Mises stress distribution on glass specimen due to the influence of the microwave plasma in: (a) top view without tool and (b) side view with tool

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Fig. 13

Plasma ball temperature distribution

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Fig. 14

Convergence of simulation iterations

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Fig. 15

Spreading of wax over glass during drilling at: (a) DC = 0.20, (b) DC = 0.50, and (c) cross crack at DC = 0.75 (600 W) with wax precursor

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Fig. 16

Microwave hole drilled with engine oil precursor at: (a) DC = 0.75, (b) DC = 1, and (c) crack developed with engine oil precursor at 600–900 W, 30 s

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Fig. 17

Microwave hole with olive oil precursor: (a) burnt blind hole and (b) crack formation

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Fig. 18

Holes with etched surface with resin at: (a) DC = 0.20, 180 s and (b) DC = 0.25, 180 s

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Fig. 19

A hole with bromide based flux (DC = 1, 20 s)

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Fig. 20

(a) Holes drilled with glycerin at DC = 0.20, 35 s; (b) burnt specimen at DC = 1, 40 s; (c) hole failure around the nailed region at DC = 0.20, 45 s; and (d) random cracking under nonuniform precursor distribution at DC = 0.20, 20 s

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Fig. 21

(a) A typical hole drilled with blue perspex precursor at DC = 1, 20 s; (b) exit side image of the eroded perspex burn at DC = 1, 40 s; and (c) an SEM image of the thermally eroded zone of the perspex

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Fig. 22

Distribution of von Mises stresses on precursor and glass specimen: (a) top view and (b) side view

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Fig. 23

Typical temperature distribution in the interaction zone over the glass specimen




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