The presentation shows how to present a research article using a PPT. The presented work can be beneficial to students pursuing post-graduation and Ph.D.

1. Lab assignment
Presented by Sahil Dhiman, Post Graduation student of Mechnical Engineering
For partial fulfilment of the course PPI 201: Advanced Manufacturing Processes
Research article presentation

2. Selection of suitable research article
Journal
• The journal’s impact factor is the
deciding criteria of the quality of
published work and its novelty.
• For the same, many articles were
searched on sciencedirect to find a
suitable research article in regard to
coursework.
• The aim was to find the conjunction of
two manufacturing techniques used in an
article for the current assignment.
• Thus, the research article as shown in
Figure at the right was chosen which was
published in the mentioned journal in
2019.
Selected research article title: Repair of
ultrasonic machining induced
surface/subsurface cracks by laser irradiation
Author: Jingsi Wang
Publishing year: 2019
Link to see full article: Click here
2021/6/16 Presenter: Sahil Dhiman 2

3. Problem formulation
Figure 1. (a,b) Micro-cracks
in USM machined surface [5]
• Micro-cracks on the machined surface (Figure 1) of brittle material during
USM is an issue which limits its application in precision engineering.
• Crack formation during this process is unavoidable, and micro-cracks left
on the machined surface cannot be completely removed by merely
decreasing the abrasive particle size.
• Therefore, a new method to repair the cracks by some secondary method
is a requirement.
[5] J. Wang et al.“Effects of abrasive material and particle shape on machining performance in micro ultrasonic
machining,” Precis. Eng., vol. 51, pp. 373–387, 2018.
Note: References order and
numbering are as per the citations
in the original article.
(a)
(b)
Abbreviations
USM: Ultrasonic Machining
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4. Proposed methodology
Fine abrasive particles are
first applied to minimize
the crack size during
USM.
A new method to repair
the cracks by laser
irradiation is proposed.
01
02
USM Laser irradiation
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5. Proposed methodology
Figure 2. Schematic and photograph
of USM experiments: (a) schematic
view, (b) experimental setup
• Machining process: Blind-hole drilling using USM (Parameters are
shown in Table 1, and process shown in Figure 2)
• Workpiece material: Glass plates
• Abrasive particles: Spherical Al2O3 abrasive particles with diameters of
2, 4, and 6 μm (Showa Denko Corporation, Japan).
• Analysis method: Field emission SEM (model: SM-71010, JEOL
Corporation).
• Etchant: Buffered oxide etch (BOE) solution [hydrofluoric acid (50%
concentration) ammonium fluoride (40% concentration)=9/100].
Table 1. Experimental conditions for blind-hole drilling experiments using spherical
Al2O3 abrasive particles with different diameters.
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6. Proposed methodology
• The two linear axes were controlled with a maximum travel range of 600mm
in the X direction and 440mm in the Y direction as shown in Figure 3.
• The beam scanning speed was programmable over 0.1–10,000 mm/min.
• The effective focal beam diameter at the work surface was 2–5 mm, which
was determined by the distance between the focusing lens and the work
surface.
• The absorbed CO2 laser irradiation will result in rapid temperature rise that
softens the thin surface layer and then decreases the material viscosity.
• Healing cracks and improving surface quality are based on this thermally
induced viscosity reduction and the flow of a thin surface layer under the
pressure generated by surface tension forces.
• To verify the results, simulations were performed and the used laser
parameters are shown in Table 2.
Table 2. Simulation parameters for
the laser irradiation model.
Figure 3. Schematic of the
laser irradiation system.
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7. Results (Preliminary)
Figure 5. Maximum feed depth under
different feed rates with spherical Al2O3
abrasives that have different mean
diameters.
Machining efficiency and surface
quality of USM
• The irregular machined surface after
USM machining are shown in Figure 4.
• The rate has the lowest value of 3 μm/s
by using 2 μm diameter abrasive
particles as can be observed in Figure 5.
• The material removal efficiency
dropped dramatically when very small
abrasive particles were used.
• The results indicate that the machined
surface quality can be improved by
using smaller particles, but complete
crack removal cannot be achieved.
Figure 4. Cross-sections of machined
surfaces: (a) using spherical Al2O3
abrasive particles 2 μm in diameter
and (b) using spherical Al2O3
abrasive particles 6 μm in diameter.
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8. Results (Preliminary)
Thermal analysis results
Scanning with a low speed leads to a large rise in
temperature. With the increase in scanning speed, the high
temperature can only last for a short time.
As the maximum temperature is above the transition
temperature Tg (530 °C) of soda-lime glass, the viscosity
of the material drop drastically, thereby enabling crack
healing can be seen in Figure 6.
However, the maximum temperature under the scanning
speed of 100 mm/min is higher than the softening point of
720 °C, which may yield melting and a potential
expansion of the material.
Therefore, to obtain a good healing result, the scanning
speed should be carefully chosen from the range of 100–
500 mm/min.
Figure 6. Temperature evolution at the evaluation point and
its subsurface points of different depths under scanning speeds
of (a) 100, (b) 300, (c) 500 and (d) 700 mm/min.
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9. Results (Preliminary)
Figure 7. Expansion of the material by laser heating (a) scanning speed of 200
mm/min; (b) Fracture of the material by laser heating with scanning speed of
100 mm/min.
Laser irradiation results of raw surfaces • The highest temperature at
100 mm/min is approximately
848 °C, a swelling may occur
under the high temperature,
which may further fracture
due to excessive tensile stress.
• Therefore, based on the
simulation and experimental
results, the scanning speed
should be controlled to be
higher than 100 mm/min for
avoiding thermal damage and
under 500 mm/min for
repairing the micro-cracks and
obtaining a smoothed surface
and can be observed in Figure
7.
(a) (b)
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10. Results (Actual)
Figure 8. Irradiation results of surfaces
machined by 2 μm diameter particles with
a scanning speed of 300 mm/min.
Laser irradiation results of machined surfaces by USM
Figure 9. Irradiation results of surfaces
machined by 2 μm diameter particles with
a scanning speed of 500 mm/min.
• After laser irradiation,
the surface quality was
improved considerably.
• Average surface
roughness, (Ra) of the
laser-irradiated USM
machined surface and
the USM machined
surface were 0.006 and
0.303 μm.
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11. Results (Actual)
Figure 10. Irradiation results of surfaces machined by 4 μm
diameter particles: (a) scanning speed of 300 mm/min and (b)
scanning speed of 500 mm/min.
Laser irradiation results of machined surfaces by USM
Figure 11. Irradiation results of surfaces machined by 6 μm
diameter particles: (a) scanning speed of 300 mm/min and (b)
scanning speed of 500 mm/min.
(b) (b)
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12. Conclusions
In this study, a laser irradiation technology was proposed for repairing micro-cracks generated during
USM. The following conclusions were drawn from the investigations:
• The crack healing was very sensitive to temperature.
• When the temperature increase was drastic, thermal energy-induced damage growth and material
expansion occur, which may degenerate the surface quality and form accuracy.
• However, if the temperature was not increased to the transition temperature of the material, crack
healing cannot be achieved.
• Periodic dimple-like micro-structures were observed on the surfaces after being irradiated by the CO2
laser with 5W power under 500 mm/min scanning speed.
• Scanning speed should be controlled to be higher than 100 mm/min for avoiding thermal damage and
under 500 mm/min for repairing the micro-cracks and obtaining a smoothed surface. [edited by
presenter]
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13. Funding agency
This work was supported by the Fundamental Research Funds for the Central Universities of China [Grant
no. 3132018259] and National Natural Science Foundation of China [Grant no. 51805067].
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14. Acknowledgement
THANK YOU
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