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Denkmalgeschützte Bauwerke im Clouth Quartier

DIN ISO 25178
Bereich	Geometrische Produktspezifikation (GPS)
Titel	Surface texture : areal
Kurzbeschreibung:	Geometrische Produktspezifikation, flächenhafte Oberflächenparameter
Letzte Ausgabe	2007
Übernahme von	ISO 25178

Die Norm ISO 25178 mit dem vollständigen Titel „Geometric Product Specifications (GPS) – Surface texture : areal“ (deutsch: „Geometrische Produktspezifikation (GPS) – Oberflächenbeschaffenheit: Flächenhaft“) ist eine Sammlung internationaler Normen zur Analyse von 3D-Oberflächentexturen.

Diese Norm wurde vom Technischen Komitee TC213 der Arbeitsgruppe WG16 der ISO (Internationale Organisation für Normung) erarbeitet.

Es ist die erste internationale Norm die Messung und Spezifikation von 3D-Oberflächentexturen berücksichtigt. Im Einzelnen definiert die Norm 3D Texturparameter und die zugehörigen Operatoren zu deren Bestimmung. Sie beschreibt auch die anwendbare Messtechnik, Kalibriermethoden und physikalische Kalibrierstandards, sowie die dafür nötige Kalibriersoftware.

Eine grundlegend neuer Bestandteil der Norm ist die Abdeckung der Berührungslosen Messmethoden, die zwar schon weit in der Industrie verbreitet sind, denen aber bisher eine Norm fehlte um Qualitätsaudits nach ISO 9000 durchzuführen. Die Norm führt zum ersten mal 3D Oberflächencharakterisierung in Bereiche ein, in denen die 2D-Profilometer seit über 30 Jahren durch Normen standardisiert wurde. Das gleiche gilt für die damit verbundene Oberflächenmesstechnik, die nicht auf mechanisch abtastende Verfahren beschränkt ist, sondern auch Konfokalmikroskope oder Interferometer umfasst.

Aufbau der Norm

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Documents constituting the standard

• Part 1: surface texture indications
• Part 2: terms, definitions and surface texture parameters
• Part 3: specification operators
• Part 6: classification of methods for measuring surface texture
• Part 601: nominal characteristics of contact (stylus) instruments
• Part 602: nominal characteristics of non-contact (confocal chromatic probe) instruments
• Part 603: nominal characteristics of non-contact (wavefront interferometric microscope) instruments
• Part 701: calibration and measurement standards for contact (stylus) instruments

Other documents are in draft or being drafted and will been published in the next few years. A number of documents that are in draft concern, in particular, other optical measurement technologies (3D confocal microscope, white light interferometric microscope, digital holographic microscope).

New definitions

The ISO 25178 standard is considered by TC213 as first and foremost providing a redefinition of the foundations of surface texture, based upon the principle that nature is intrinsically 3D. It is anticipated that future work will extend these new concepts into the domain of 2D profilometric surface texture analysis, requiring a total revision of all current surface texture standards (ISO 4287, ISO 4288, ISO 1302, ISO 11562, ISO 12085, ISO 13565, etc.)

A new vocabulary is imposed:

• S filter: filter eliminating the smallest scale elements from the surface (or of the shortest wavelength for a linear filter)
• L filter: filter eliminating the largest scale elements from the surface (or of the longest wavelength for a linear filter)
• F operator: operator suppressing nominal form.
• S-L surface: surface obtained after S and L filtering. Equivalent to a roughness or waviness surface.
• S-F surface: surface obtained after S filtering and application of the F operator.
• Primary surface: surface obtained after S filtering.
• Nesting index: index corresponding to the cut-off wavelength of a linear filter, or to the scale of the structuring element of a morphological filter.

The new authorized filters are described in the series of technical specifications included in ISO/TS 16610. These filters include: the Gaussian filter, the spline filter, robust filters, morphological filters, wavelet filters, cascading filters, etc.

3D areal surface texture parameters

Generalities

3D parameters are written with the capital letter S (or V) followed by a suffix of one or two small letters. They are calculated on the entire surface and no more by averaging estimations calculated on a number of base lengths, as is the case for 2D parameters. In contrast with 2D naming conventions, the name of a 3D parameter does not reflect the filtering context. For example, Sa always appears regardless of the surface, whereas in 2D there is Pa, Ra or Wa depending on whether the profile is a primary, roughness or waviness profile.

Height parameters

These parameters quantify the z axis perpendicular to the surface only.

Parameter	Description
Sq	Root mean square height of the surface
Ssk	Skewness of height distribution
Sku	Kurtosis of height distribution
Sp	Maximum height of peaks
Sv	Maximum height of valleys
Sz	Maximum height of the surface
Sa	Arithmetical mean height of the surface

Spatial parameters

These parameters quantify the lateral information present on the x and y axes of the surface.

Parameter	Description
Sal	Fastest decay auto-correlation rate
Str	Texture aspect ratio of the surface
Std	Texture direction of the surface

Hybrid parameters

These parameters combine the information present on the x, y and z axes of the surface.

Parameter	Description
Sdq	Root mean square gradient of the surface
Sdr	Developed area ratio

Functional parameters

These parameters are calculated from the Abbott-Firestone curve obtained by the integration of the height distribution on the whole surface.

Parameter	Description
Smr	Surface bearing area ratio
Smc	Height of surface bearing area ratio
Sxp	Peak extreme height
Vm	Material volume at a given height
Vv	Void volume at a given height
Vmp	Material volume of peaks
Vmc	Material volume of the core
Vvc	Void volume of the core
Vvv	Void volume of the valleys

Parameters related to segmentation

These parameters are derived from a segmentation of the surface into motifs (dales and hills). Segmentation is carried out using the watersheds method.

Paramètre	Description
Spd	Density of peaks
Spc	Arithmetic mean peak curvature
S10z	10 point height
S5p	5 point peak height
S5v	5 point valley height
Sda	Closed dales area
Sha	Closed hills area
Sdv	Closed dales volume
Shv	Closed hills volume

3D surface texture measurement instruments

Part 6 of the standard divides the usable technologies into three families:

1. Topographical instruments: contact and non-contact 3D profilometers, interferential and confocal microscopes, structured light projectors, stereoscopic microscopes, etc.
2. Profilometric instruments: contact and non-contact 2D profilometers, line triangulation lasers, etc.
3. Instruments functioning by integration: pneumatic measurement, capacitive, by optical diffusion, etc.

and defines each of these technologies.

Next, the standard explores a number of these technologies in detail and dedicates two documents to each of them:

• Part 6xx: nominal characteristics of the instrument
• Part 7xx: calibration of the instrument

Contact profilometer

Parts 601 and 701 describe the contact profilometer, using a diamond point to measure the surface with the assistance of a lateral scanning device.

Chromatic confocal gauge

Part 602 describes this type of non-contact profilometer, incorporating a single point white light chromatic confocal sensor. The operating principle is based upon the chromatic dispersion of the white light source along the optical axis, via a confocal device, and the detection of the wavelength that is focused on the surface by a spectrometer.

References

• ISO 25178 on the ISO Web site
• New 3D parameters and filtration techniques for surface metrology, François Blateyron, Quality Magazine White Paper
• ISO 25178 – new family of 3D feature parameters characterises topographical surface features, François Blateyron, Surface Newsletter
• ISO/TS 16610-1 : Geometric Product Specifications (GPS): Filtration – Part 1: Overview and basic concepts
• ISO/TS 14406 : Geometric Product Specifications (GPS): Extraction

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