Citation: Wang, W.; Xue, W.; Wu, S.;
Mu, Z.; Yi, J.; Tang, A.J. High-Speed
Micro-Particle Motion Monitoring
Based on Continuous Single-Frame
Multi-Exposure Technology. Materials
2022, 15, 3871. https://doi.org/
10.3390/ma15113871
Academic Editors: Arkadiusz Gola,
Izabela Nielsen and Patrik Grznár
Received: 21 March 2022
Accepted: 12 May 2022
Published: 29 May 2022
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Communication
High-Speed Micro-Particle Motion Monitoring Based on
Continuous Single-Frame Multi-Exposure Technology
Wei Wang
1
, Weiwei Xue
2
, Shufan Wu
1
, Zhongcheng Mu
1,
* , Jiyuan Yi
1
and Andrew J. Tang
3
1
School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai 200240, China;
wangwei_up@sjtu.edu.cn (W.W.); shufan.wu@sjtu.edu.cn (S.W.); sjtuyjy@sjtu.edu.cn (J.Y.)
2
CAS Key Laboratory of Mechanical Behavior and Design of Material, Department of Modern Mechanics,
University of Science and Technology of China, Hefei 230027, China; xueww@mail.ustc.edu.cn
3
School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney,
Camperdown, NSW 2006, Australia; andrew.tang@sydney.edu.au
* Correspondence: muzhongcheng@sjtu.edu.cn; Tel.: +86-15000744320
Abstract:
The impact phenomena of solid micro-particles have gathered increasing interest across
a wide range of fields, including space debris protection and cold-spray additive manufacturing
of large, complicated structures. Effective motion monitoring is essential to understanding the
impact behaviors of micro-particles. Consequently, a convenient and efficient micro-particle motion
monitoring solution is proposed based on continuous single-frame multiple-exposure imaging
technology. This method adopts a camera with excellent low-light performance coupled with high-
frequency light-emitting diode (LED) flashes to generate short interval illumination. This technology
can, in theory, achieve 1 million effective frames per second (fps) and monitor particles as small as
10 microns with speeds up to 12 km/s. The capabilities of the proposed method were validated by
a series of micro-particle motion monitoring experiments with different particles sizes and materials
under varying camera configurations. The study provides a feasible and economical solution for the
velocity measurement and motion monitoring of high-speed micro-particles.
Keywords:
micro-particles’ impact; motion monitoring; single-frame multiple-exposure;
high-frequency light-emitting diode flash
1. Introduction
The impact phenomena of solid particles are of interest to researchers across many
fields, including the biomedicine, aerospace, and materials industries, among others. This
phenomena can be divided into several key categories according to the velocity and size
of the particle under observation: particles’ adhesion [
1
,
2
]; shot peening, including tradi-
tional pneumatic shot peening [
3
] (surface-strengthening phenomenon that occurs when
particle diameters range between 0.1 and 1.0
µ
m and have an impact velocity less than
100 m/s) and supersonic shot peening (surface-strengthening phenomenon that occurs
when particle diameters range between 0.1 and 1.0
µ
m and have an impact velocity greater
than that of sound) [
4
–
7
]; particles’ surface erosion (dynamic process of surface material
loss caused by the impact of particles with diameters of about 50–300
µ
m at speeds 10 to
300 m/s from differing impact angles) [
8
–
11
]; high-speed impact (impact phenomenon of
particles with diameters ranging between 1 and 100 mm and velocity ranging between
50 and 3000 m/s) [
12
,
13
]; hypervelocity impact (impact velocity exceeding the speed of
sound propagates in the two impact bodies, creating a temporary high-density and high-
temperature state at the point of impact, leading to 1 TPa of pressure and vaporization
of the associated materials) [
14
,
15
]; particles with super-deep penetration (SDP) (metal
particles accelerated to 1–3 km/s impact the metal surface, resulting in a penetration depth
between 1000 and 10,000 times the particles’ diameters) [
16
,
17
]; and cold spraying (particles’
Materials 2022, 15, 3871. https://doi.org/10.3390/ma15113871 https://www.mdpi.com/journal/materials
