Velocity
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Velocity
General information
The term velocity (or synonym also speed) is one of the most frequently used terms in scientific and technical literature. In materials testing and plastics testing and the related literature on testing technology, there is an inconsistent and sometimes not clearly defined variety of terms used to describe the velocity of experimental tests. The terms are often used without further definition and sometimes with contradictory units of measurement for different test methods.
Mechanical polymer testing
The following terms are explained in more detail in the WIKI-Lexicon of Polymer Testing and Diagnostics for the field of mechanical polymer testing:
- Deformation rate
- Deformation speed
- Test speed
- Strain speed or strain rate
- Basic principles
- Applications
- Crosshead speed
In addition, the terms not explained separately
- Pendulum hammer velocity
- Impact velocity
are frequently used.
Terms related to manufacturing technology are also not explained separately, such as
- the twisting speed
or
- the take-off speed (pull-off speed),
which are used in the plastics industry and textile technology in the production of fibres, threads, films and sheets and have a significant influence on the mechanical properties. The term pull-off speed is also used synonymously in the literature for crosshead speed.
Fracture mechanical testing
In the fracture mechanics testing of plastics and in the testing of composite materials, the following terms are also used
- Crack opening displacement velocity
- Crack velocity (see crack propagation) and
- Crack propagation velocity (see, among other things, fracture mechanical testing, fracture types, fatigue crack propagation elastomers and crack propagation stress corrosion cracking).
Non-destructive polymer testing
In non-destructive polymer testing, the speed of propagation of different types of waves is used to interpret acoustic phenomena, see e.g. refraction of sound waves or ultrasonic birefringence.
The term ultrasound velocity is also used relatively frequently in the literature, e.g. when explaining the terms acoustic properties, modulus of elasticity ultrasonic measurements, air ultrasound, crack propagation, ultrasonic birefringence, transmission of sound waves or ultrasonic weld inspection.
The ultrasound velocity is usually specified as the phase velocity. If wave packets with different frequencies occur due to the generation of sound, the wave packets contain waves with different wavelengths. The so-called group velocity is then specified as the average propagation speed of the ultrasound.
See also
References
- Grellmann, W., Seidler, S. (Eds.): Polymer Testing Carl Hanser Munich (2022) 3rd. Edition, (ISBN 978-1-56990-806-8; E-Book ISBN 978-156990-807-5; see AMK-Library under A 22)