Numerical
calculations and simulations based on finite method, are integrated parts of
engineering design tasks. There are numerous finite software available in the
market, having nearly similar basic features, but the key difference is, that
what kind of opportunities they offer for more complex, non-linear tasks. The
first commercial version of ABAQUS finite software was released at the end of
the 70s. It is extraordinarily popular among researchers, as it gives an
opportunity to replace the built-in procedures with user-coded subroutines
including self-developed material models too. It is also worth emphasizing,
that the software is widespread in industrial usage for non-linear
calculations. A number of major companies simulate car crash tests with ABAQUS
for instance.
The
Department of Applied Mechanics purchased education, research and industrial
licences, offering opportunities in a wide range of projects.
Photron FastCam SA5 high-speed camera
High-speed
camera recordings give an opportunity to observe certain phenomena, invisible
to the naked eye, due to the processing speed. There are several Youtube
channels, where various physical phenomena are shown with the help of
slow-motion recordings. Nowadays, even smartphones can record a 1000 FPS (frame
per second) video. This camera helps to observe and analyze high-speed motions,
which we could not be able to with a simple video recording equipment.
The
Department of Applied Mechanics purchased such a high-performance high-speed camera,
which can record even 750 000 frames per second. The camera has been being used
for machine tool vibrations at cutting processes, but several theses and
publications were written thanks to the camera’s recordings.
Optitrack motion tracking system
Motion
capturing (mocap) is a unique process, which helps to record motion tracks of
various solids (objects, humans). This technology is widespread in the field of
film and entertainment industry and is also used in biomechanical, medicine and
sports researches. Furthermore, the technique is often utiliezed in traditional
industrial environment, e.g., in robotics. The application of the resulting
motion tracks is very broad. The measurement can be the basis of a spectacular
animation or an essential part of academic research. The Optitrack system is
able to record motions, basically with passive markers.
The
system available at the Department of Applied Mechanics has 12 pieces of Prime
13 cameras (4 of them have wide-angle lens). The system follows the spatial
location of the markers fixed on a solid body. We prepare the recorded data
series for a procession or analysis with a certain software (Motive). Our
camera system can be set both outside and inside. In case of the cameras cannot
emit the proper amount of infrared light, then we can use active light-emitting
markers instead of passive ones. With these active markers, the system can be synchronised
with other measuring systems.
Our
system can be used in various poblems. First of all, it is the base device of
the research of the department in the field of human balancing. Furthermore,
the system has been used in several BSc, Master and PhD thesesand TDK
(Students’ Scientific Conference) works, and in many industrial projects.
The
CNC milling machine at the Department of Applied Mechanics boosted the
Department’s research. With this machine, we can validate the mechanical and
mathematical models nearly in a realistic industrial environment.
The
important phenomena in machine tool vibrations can be investigated and directly
measured with a much higher degree of precision. We have identified effects
that were not modelled before, providing new research directions, for instance,
identifying the stochastic features of cutting force, measuring shear plane
used in the force model, and predicting and avoiding undesired vibrations
during machining processes. We also utilize self-developed experimental devices
for measurement, such as a high-precision optical displacement sensor, or a
shooting machine calibrated for in-operational spindle excitation. The
measurements are supported by a high-speed camera system that can be mounted inside
the machine, and dynamometers, which provide a high-precision measurement of
cutting forces during machining of a workpiece.
The
milling machine contributes to our educational goals as well. During the course
’Machine-tool vibrations’ students can get to know the mathematical model of
the cutting process, calculation of the surface errors done during cutting, the
temperature dependency of the cutting process, but what is more important,
we can show these phenomena on-site in the lab.
In
the course ’Non-linear vibrations’ we examine the non-linear phenomena that can
arise during the machining process. Moreover, we have also used the milling
machine in project studies, theses and students’ articles (TDK). During the
projects, our students have performed modal measurements, cooperated in the
calibration of dynamometer cells, but also have digitalised spatial bodies with
3D laser surface-scanning processes. The machine and the belonging instruments
promote our practice experiences, and they are excellent both for research
purposes and educational uses.
László Benesóczky
Photos: BME Department of Applied Mechanics
Photos: BME Department of Applied Mechanics
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