Penetration depth
The penetration depth is used as a measure of the ability of an object, substances or waves to penetrate an object or matter, or as a property of the object to offer resistance to penetration. It is usually based on a standardized penetration process and determined using a comparative measurement method.
ballistics
In ballistics , the penetration depth of a weapon projectile is determined with a fire test on a block of standardized material (e.g. ballistic gelatine ). This measurement method is mainly used in forensics to determine the shooting distance.
Electromagnetic waves
In the case of electromagnetic waves , the penetration depth is the point at which an electromagnetic wave when penetrating a medium corresponds to only one -th (approx. 37%) of the output amplitude.
The term is used, among other things, as London penetration depth ( London equation ), penetration depth of an evanescent wave (see ATR spectroscopy ). The skin effect is the depth at which the current density has dropped to 1% of the value on the conductor surface.
geophysics
With various geophysical measurement methods, the penetration depth is a limiting factor for the investigation of structures inside the earth's body . These are processes in which the interior of the earth is irradiated with excited waves.
In addition to electromagnetic methods such as georadar or magnetotellurics , the term is also used in geoelectrics and in relation to seismic waves in seismology and active seismics . The depth of penetration depends on the frequency of the wave, but is also limited by the distance between the source and the measuring instrument and the associated beam path .
Materials
In the case of materials , the penetration depth is a measure of the ability of a liquid to penetrate a material. It can be calculated using the Washburn equation .
During the impregnation, it is desirable that the impregnating agent has the greatest possible penetration depth, which is not the case with layer-forming paints and varnishes that are commercially available today because of the increased consumption. The high penetration depth of pure linseed oil and pure linseed oil paint is a prerequisite for their preservative properties.
Material testing
In the testing of materials , various measuring methods are used in which the penetrability by way of comparison in the body material whose hardness is determined. The deeper the penetration, the softer the fabric. However, only values that have been determined using the same measuring method may be compared.
The following measurement methods are common, which work with the measure of the penetration depth:
- Brinell hardness test
- Vickers hardness test (hard metals)
- Knoop hardness test (hard metals)
- Rockwell hardness test (various test pieces)
- Shore hardness test (partly also suitable for non-metals, such as elastomers and GRP )
Individual evidence
- ↑ Telefunken laboratory book. Volume 1. 7th edition 1965, p. 104.