ASTM F2791-14
(Guide)Standard Guide for Assessment of Surface Texture of Non-Porous Biomaterials in Two Dimensions
Standard Guide for Assessment of Surface Texture of Non-Porous Biomaterials in Two Dimensions
SIGNIFICANCE AND USE
4.1 The term “surface texture” is used to describe the local deviations of a surface from an ideal shape. Surface texture usually consists of long wavelength repetitive features that occur as results of chatter, vibration, or heat treatments during the manufacture of implants. Short wavelength features superimposed on the long wavelength features of the surface, which arise from polishing or etching of the implant, are referred to as roughness.
4.2 This guide provides an overview of techniques that are available for measuring the surface in terms of Cartesian coordinates and the parameters used to describe surface texture. It is important to appreciate that it is not possible to measure surface texture per se, but to derive values for parameters that can be used to describe it.
SCOPE
1.1 This guide describes some of the more common methods that are available for measuring the topographical features of a surface and provides an overview of the parameters that are used to quantify them. Being able to reliably derive a set of parameters that describe the texture of biomaterial surfaces is a key aspect in the manufacture of safe and effective implantable medical devices that have the potential to trigger an adverse biological reaction in situ.
1.2 This guide is not intended to apply to porous structures with average pore dimensions in excess of approximately 50 nm (0.05 μm).
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Buy Standard
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:F2791 −14
StandardGuide for
Assessment of Surface Texture of Non-Porous Biomaterials
in Two Dimensions
This standard is issued under the fixed designation F2791; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 Other Standards:
ISO 3274 Geometrical Product Specifications (GPS)—
1.1 This guide describes some of the more common meth-
Surface Texture: Profile Method—Nominal Characteris-
ods that are available for measuring the topographical features
tics of Contact (Stylus) Instruments
of a surface and provides an overview of the parameters that
ISO 4287 Geometrical Product Specifications (GPS)—
are used to quantify them. Being able to reliably derive a set of
Surface Texture: Profile Method—Terms, Definitions and
parameters that describe the texture of biomaterial surfaces is
Surface Texture Parameters
a key aspect in the manufacture of safe and effective implant-
ISO 4288 Geometrical Product Specifications (GPS)—
able medical devices that have the potential to trigger an
Surface Texture: Profile Method—Rules and Procedures
adverse biological reaction in situ.
for the Assessment of Surface Texture
1.2 This guide is not intended to apply to porous structures
ISO 13565–1 Geometrical Product Specifications (GPS)—
with average pore dimensions in excess of approximately 50
SurfaceTexture: Profile Method—Surfaces Having Strati-
nm (0.05 µm).
fiedFunctionalProperties;FilteringandGeneralMeasure-
ment Conditions
1.3 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3. Terminology
standard.
3.1 Definitions of Terms Specific to This Standard:
1.4 This standard does not purport to address all of the
3.1.1 biomaterial, n—any substance (other than a drug),
safety concerns, if any, associated with its use. It is the
synthetic or natural, that can be used as a system or part of a
responsibility of the user of this standard to establish appro-
system that treats, augments, or replaces any tissue, organ, or
priate safety and health practices and determine the applica-
function of the body. F2664
bility of regulatory limitations prior to use.
3.1.2 evaluation length, ln, n—length in the direction of the
2. Referenced Documents x-axis used to assess the profile under evaluation.
3.1.2.1 Discussion—The evaluation length may contain one
2.1 ASTM Standards:
or more sampling lengths. ISO 4287
C813 Test Method for Hydrophobic Contamination on Glass
by Contact Angle Measurement 3.1.3 hydrophilic, adj—having a strong affinity for water;
wettable.
F2312 Terminology Relating to Tissue Engineered Medical
Products 3.1.3.1 Discussion—Hydrophilic surfaces exhibit zero con-
F2450 Guide for Assessing Microstructure of Polymeric tact angles. C813
Scaffolds for Use in Tissue-Engineered Medical Products
3.1.4 hydrophobic, adj—having little affinity for water;
F2664 Guide for Assessing the Attachment of Cells to
nonwettable.
Biomaterial Surfaces by Physical Methods
3.1.4.1 Discussion—Hydrophobic surfaces exhibit contact
anglesappreciablygreaterthanzero:generallygreaterthan45°
for the advancing angle. C813
This guide is under the jurisdiction of ASTM Committee F04 on Medical and
3.1.5 implant, n—a substance or object that is put in the
Surgical Materials and Devices and is the direct responsibility of Subcommittee
body as a prosthesis, or for treatment or diagnosis. F2664
F04.42 on Biomaterials and Biomolecules for TEMPs.
Current edition approved Oct. 1, 2014. Published December 2014. Originally
3.1.6 lay, n—the direction of the predominant surface
approved in 2009. Last previous edition approved in 2009 as F2791–09. DOI:
pattern. ISO 13565–1
10.1520/F2791-14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2791−14
NOTE 1—The surface shown in (A) has no directionality or lay, therefore profiles can be oriented at any angle. Profiles (dashed line arrow) are drawn
perpendicular to the lay (solid line arrow) in surfaces that have directionality (B).
FIG. 1Profile Orientation and Surface Features
3.1.7 primary profile, n—the profile after application of the measure surface texture per se, but to derive values for
short wavelength filters. ISO 3274 parameters that can be used to describe it.
3.1.8 profile peak, n—an outwardly directed (from the
5. The Relationship Between Surface Texture, Surface
material to the surrounding medium) portion of the assessed
Chemistry, Surface Energy, and Biocompatibility
profileconnectingtwoadjacentpointsoftheintersectionofthe
profile with the x-axis. ISO 4287 5.1 The biocompatibility of materials is influenced by many
factors such as size, shape, material bulk, and surface chemical
3.1.9 profile valley, n—aninwardlydirected(fromsurround-
composition, surface energy, and surface topography. Chang-
ing medium to material) portion of the assessed profile
ing any one of these related characteristics of a biocompatible
connecting two adjacent points of the intersection of the
material can have a significant effect on cell behavior. The
assessed profile with the x-axis. ISO 4287
response of a cell to a biomaterial can be assessed by
3.1.10 real surface, n—surface limiting the body and sepa-
measuring the adhesive strength between it and the underlying
rating it from the surrounding medium. ISO 4287
surface, monitoring changes in its shape or in the expression of
3.1.11 sampling length, lr, n— length in the direction of the
biomarkers.
x-axis used for identifying the irregularities characterizing the
5.2 The chemical species present on a surface can be
profile under evaluation. ISO 4287
mapped in detail using surface sensitive analysis techniques
3.1.12 scaffold, n—a support, delivery vehicle or metric for
(for example, X-ray photoelectron spectroscopy where the
facilitating the migration, binding, or transport of cells or 4
penetration depth is 10 nm or below (1)). The chemical
bioactive molecules used to replace, repair, or regenerate
species present on the surface together with the surface
tissues. F2450
topography determine how hydrophilic the surface is. Measur-
3.1.13 surface profile, n—profile that results from the inter-
ing the contact angle between the surface and a fluid, usually
section of the real surface by a specified plane.
water,canassessthedegreeofhydrophilicityofasurface.Care
3.1.13.1 Discussion—In practice, it is usual to choose a
should be taken when comparing contact angle measurements
plane with a normal that nominally lies parallel to the real
made on different surfaces, as the relative contributions from
surface and in a suitable direction. ISO 4287
the surface chemistry and texture are unlikely to be the same.
4. Significance and Use
6. Surfaces and Surface Profiles
4.1 The term “surface texture” is used to describe the local
6.1 Conventionally surfaces are described in Cartesian co-
deviations of a surface from an ideal shape. Surface texture
ordinates where the x-axis is defined as being perpendicular to
usually consists of long wavelength repetitive features that
the lay direction. The y-axis is in-plane and is perpendicular to
occur as results of chatter, vibration, or heat treatments during
the x-axis direction. The z-axis is out of plane. The profile of a
the manufacture of implants. Short wavelength features super-
surface that has a uniform, non-directional texture can be
imposed on the long wavelength features of the surface, which
measured at any in-plane orientation (see Fig. 1(A)); however,
arisefrompolishingoretchingoftheimplant,arereferredtoas
several profiles at different orientations should be measured to
roughness.
find the maximum amplitude (see Fig. 1(A)). For patterned
4.2 This guide provides an overview of techniques that are
available for measuring the surface in terms of Cartesian
coordinates and the parameters used to describe surface tex-
The boldface numbers in parentheses refer to a list of references at the end of
ture. It is important to appreciate that it is not possible to this standard.
F2791−14
surfacesthathaveperiodicfeatures,alay,theorientationofthe valleys that is in essence a form of filtering. This topic is
profile is at right angles to it (see Fig. 1(B)). further discussed in Section 11.
6.2 Themeasuredsurfaceiscomposedofthreecomponents:
7.2 Filtersusedinsurfacetexturemeasurementsdonothave
form, waviness and roughness. The form corresponds to the
a sharp cut-off in spatial frequency above or below which
underlying shape and tilt of the surface with respect to the
information is rejected.This gradual attenuation of high or low
measuring platform. The software packages used for surface
spatial frequency data helps avoid distortion of the measure-
texture analysis all have a methodology for removing the form
ments that can occur when strong features are close to the
from the surface. The “corrected” surface can then be used to
filtration limits. The point on the transmission curve at which
obtain a 2-D profile that describes the surface texture. This
the transmitted signal is reduced to 50 % is referred to as the
profile after removal of form is defined according to ISO 3274
cut-off wavelength,λc, of the filter (Fig. 3). For measurements
as the primary profile. The stages involved in the analysis of
made using a stylus instrument (Section 11), the choice of λc
the measured profile through primary profile to the roughness
depends on the sampling frequency and the speed at which the
profile are shown in Fig. 2.
stylus moves over the surface. For example, measurements
–1
madeatintervalsof0.01mmfromadevicemovingat1mms
7. Filtering and the Cut-Off Wavelength
will generate data at a frequency of 100 Hz. Increasing the
7.1 Surfacedatacanbefilteredtoremoveunwantednoiseor
samplingintervalto0.1mmwillreducethefrequencyatwhich
to remove texture information at unwanted wavelengths. Fil-
dataareobtainedto10Hz.Ahigh-passfilterthatsuppressesall
ters are classified according to the spatial periodicity that they
frequencies below 10 Hz effectively removes any surface
allow to pass through; low-pass filters admit long wavelengths
irregularities larger than 0.1 mm spacing from the data. Hence,
and reject short ones; high-pass filters do the opposite. Band-
filters can be used to bias the experimental data towards
pass filters, as the name implies, allow a limited range of
detecting profile (surface texture after applying a low-pass to
wavelengths to pass. In practice, using filters can create
filterthedata),waviness(afterapplyingaband-passfilter),and
problems in deciding how much of the noise in the measure-
roughness (after applying a high-pass filter). Measurement
ments is “real” and how much can be attributed to the surface.
conditions are set for filters according to the respective values
It should be noted that some aspects of the surface are not
faithfully reproduced due to limitations of the measurement of the sampling interval, measurement speed, and filtration
method, for example, an inability to track the sides of steep limits, according to ISO 3274.
FIG. 2Summary of Stages Involved in Analysis of Measured Profile to Obtain a Roughness Profile
F2791−14
FIG. 350% Reduction in Transmission Curve
7.3 ISO 4287 specifies that 2-D roughness parameters need 8.1.2 Spatial parameters, which describe in-plane variations
to be determined over five sequential sampling lengths, lr, of surface texture; and
unless otherwise specified. This grouping of five serial sam- 8.1.3 Hybrid parameters, which combine both amplitude
pling lengths is referred to as the evaluation length, ln. The and spatial information (for example, mean slope).
sampling length varies according to the length scale of the
8.2 Ra—The most widely used parameter to quantify sur-
texture being assessed; larger features require a long sampling
face texture is the arithmetical mean deviation of the absolute
length.Guidanceastowhichsamplinglengthtouseforagiven
ordinate values, Z(x), of the profile from a center line (see
range of feature sizes is shown in Table 1. It may be necessary
Table 2 and Fig. 5). Despite its common usage, Ra does not
to perform one or more iterations to identify the best value for
provideatrulyaccuraterepresentationofasurfaceprofilesince
lr. This can be achieved by calculating the mean width of a
any information regarding peak heights or valley depths can be
profile element, RSm (see Fig. 4), from a measured profile
lost in its derivation. This insensitivity to surface texture is
where the value for lr is based on a best guess. This initial
apparent in Fig. 6, which shows that quite different profiles can
iteration will enable a new value for RSm to be determined and
have the same Ra value. The statistical significance of Ra is
that leads to a potential revision of lr according to Table 1.
improved by averaging the values obtained for each of the five
sampling lengths.
8. Quantification of Surface Profiles
8.3 Rq—The root-mean-square value of all distances of the
8.1 Parameters that are used to characterize 2-D surface
measured profile away from the center line, Rq, although
profiles are grouped as:
similar in terms of its derivation to Ra, has a subtle but
8.1.1 Amplitude parameters, which are measures of varia-
significant difference. The deviations of the peak heights and
tions in profile height. These parameters are split into two
valley depths from the midline appear as a squared term in Rq.
subclasses: averaging parameters, and peak and valley param-
Thatincreasesitssensitivitytohighpeaksordeepvalleys.This
eters;
sensitivity can be useful, but it should be noted that the
presenceofaforeignbody,forexample,hairorascratchinthe
surface can have a significant influence on the value of Rq.
TABLE 1 Guide to Choosing Sampling Lengths for the
A
Measurement of Periodic Profiles 8.4 Rsk—Skewness, the distribution of peak heights and
Mean profile element Sampling length,
valley depths provides valuable information about surface
width, RSm (µm) lr (µm)
texture. A surface that has a range of peak heights and valley
13 < RSm# 40 80
depths will have a bell-shaped probability distributi
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F2791 − 09 F2791 − 14
Standard Guide for
Assessment of Surface Texture of Non-Porous Biomaterials
in Two Dimensions
This standard is issued under the fixed designation F2791; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This guide describes some of the more common methods that are available for measuring the topographical features of a
surface and provides an overview of the parameters that are used to quantify them. Being able to reliably derive a set of parameters
that describe the texture of biomaterial surfaces is a key aspect in the manufacture of safe and effective implantable medical devices
that have the potential to trigger an adverse biological reaction in situ.
1.2 This guide is not intended to apply to porous structures with average pore dimensions in excess of approximately 50 nm
(0.05 μm).
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
C813 Test Method for Hydrophobic Contamination on Glass by Contact Angle Measurement
F2312 Terminology Relating to Tissue Engineered Medical Products
F2450 Guide for Assessing Microstructure of Polymeric Scaffolds for Use in Tissue-Engineered Medical Products
F2664 Guide for Assessing the Attachment of Cells to Biomaterial Surfaces by Physical Methods
2.2 Other Standards:
ISO 3274 Geometrical Product Specifications (GPS)—Surface Texture: Profile Method—Nominal Characteristics of Contact
(Stylus) Instruments
ISO 4287 Geometrical Product Specifications (GPS)—Surface Texture: Profile Method—Terms, Definitions and Surface
Texture Parameters
ISO 4288 Geometrical Product Specifications (GPS)—Surface Texture: Profile Method—Rules and Procedures for the
Assessment of Surface Texture
ISO 13565–1 Geometrical Product Specifications (GPS)—Surface Texture: Profile Method—Surfaces Having Stratified
Functional Properties; Filtering and General Measurement Conditions
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 biocompatible, adj—a material may be considered biocompatible if the materials perform with an appropriate host
response in a specific application. F2312
3.1.1 biomaterial, n—any substance (other than a drug), synthetic or natural, that can be used as a system or part of a system
that treats, augments, or replaces any tissue, organ, or function of the body. F2664
This guide is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee F04.42
on Biomaterials and Biomolecules for TEMPs.
Current edition approved Aug. 1, 2009Oct. 1, 2014. Published September 2009December 2014. Originally approved in 2009. Last previous edition approved in 2009 as
F2791–09. DOI: 10.1520/F2791-09.10.1520/F2791-14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2791 − 14
3.1.2 evaluation length, ln, n—length in the direction of the x-axis used to assess the profile under evaluation.
3.1.2.1 Discussion—
The evaluation length may contain one or more sampling lengths. ISO 4287
3.1.3 hydrophilic, adj—having a strong affinity for water; wettable.
3.1.3.1 Discussion—
Hydrophilic surfaces exhibit zero contact angles. C813
3.1.4 hydrophobic, adj—having little affinity for water; nonwettable.
3.1.4.1 Discussion—
Hydrophobic surfaces exhibit contact angles appreciably greater than zero: generally greater than 45° for the advancing angle.
C813
3.1.5 implant, n—a substance or object that is put in the body as a prosthesis, or for treatment or diagnosis. F2664
3.1.6 lay, n—the direction of the predominant surface pattern. ISO 13565–1
3.1.7 primary profile, n—the profile after application of the short wavelength filters. ISO 3274
3.1.8 profile peak, n—an outwardly directed (from the material to the surrounding medium) portion of the assessed profile
connecting two adjacent points of the intersection of the profile with the x-axis. ISO 4287
3.1.9 profile valley, n—an inwardly directed (from surrounding medium to material) portion of the assessed profile connecting
two adjacent points of the intersection of the assessed profile with the x-axis. ISO 4287
3.1.10 real surface, n—surface limiting the body and separating it from the surrounding medium. ISO 4287
3.1.11 sampling length, lr, n— length in the direction of the x-axis used for identifying the irregularities characterizing the profile
under evaluation. ISO 4287
3.1.12 scaffold, n—a support, delivery vehicle or metric for facilitating the migration, binding, or transport of cells or bioactive
molecules used to replace, repair, or regenerate tissues. F2450
3.1.13 surface profile, n—profile that results from the intersection of the real surface by a specified plane.
3.1.13.1 Discussion—
In practice, it is usual to choose a plane with a normal that nominally lies parallel to the real surface and in a suitable direction.
ISO 4287
NOTE 1—The surface shown in (A) has no directionality or lay, therefore profiles can be oriented at any angle. Profiles (dashed line arrow) are drawn
perpendicular to the lay (solid line arrow) in surfaces that have directionality (B).
FIG. 1 Profile Orientation and Surface Features
F2791 − 14
4. Significance and Use
4.1 The term “surface texture” is used to describe the local deviations of a surface from an ideal shape. Surface texture usually
consists of long wavelength repetitive features that occur as results of chatter, vibration, or heat treatments during the manufacture
of implants. Short wavelength features superimposed on the long wavelength features of the surface, which arise from polishing
or etching of the implant, are referred to as roughness.
4.2 This guide provides an overview of techniques that are available for measuring the surface in terms of Cartesian coordinates
and the parameters used to describe surface texture. It is important to appreciate that it is not possible to measure surface texture
per se, but to derive values for parameters that can be used to describe it.
5. The Relationship Between Surface Texture, Surface Chemistry, Surface Energy, and Biocompatibility
5.1 The biocompatibility of materials is influenced by many factors such as size, shape, material bulk, and surface chemical
composition, surface energy, and surface topography. Changing any one of these related characteristics of a biocompatible material
can have a significant effect on cell behavior. The response of a cell to a biomaterial can be assessed by measuring the adhesive
strength between it and the underlying surface, monitoring changes in its shape or in the expression of biomarkers.
5.2 The chemical species present on a surface can be mapped in detail using surface sensitive analysis techniques (for example,
X-ray photoelectron spectroscopy where the penetration depth is 10 nm or below (1)). The chemical species present on the surface
together with the surface topography determine how hydrophilic the surface is. Measuring the contact angle between the surface
and a fluid, usually water, can assess the degree of hydrophilicity of a surface. Care should be taken when comparing contact angle
measurements made on different surfaces, as the relative contributions from the surface chemistry and texture are unlikely to be
the same.
6. Surfaces and Surface Profiles
6.1 Conventionally surfaces are described in Cartesian coordinates where the x-axis is defined as being perpendicular to the lay
direction. The y-axis is in plane in-plane and is perpendicular to the x-axis direction. The z-axis is out of plane. The profile of a
surface that has a uniform, non-directional texture can be measured at any in plane in-plane orientation (see Fig. 1(A)); however,
several profiles at different orientations should be measured to find the maximum amplitude (see Fig. 1(A)). For patterned surfaces
that have periodic features, a lay, the orientation of the profile is at right angles to it (see Fig. 1(B)).
6.2 The measured surface is composed of three components: form, waviness and roughness. The form corresponds to the
underlying shape and tilt of the surface with respect to the measuring platform. The software packages used for surface texture
analysis all have a methodology for removing the form from the surface. The “corrected” surface can then be used to obtain a 2-D
profile that describes the surface texture. This profile after removal of form is defined according to ISO 3274 as the primary profile.
The stages involved in the analysis of the measured profile through primary profile to the roughness profile are shown in Fig. 2.
7. Filtering and the Cut-Off Wavelength
7.1 Surface data can be filtered to remove unwanted noise or to remove texture information at unwanted wavelengths. Filters
are classified according to the spatial periodicity that they allow to pass through; low-pass filters admit long wavelengths and reject
short ones; high-pass filters do the opposite. Band-pass filters, as the name implies, allow a limited range of wavelengths to pass.
In practice, using filters can create problems in deciding how much of the noise in the measurements is “real” and how much can
be attributed to the surface. It should be noted that some aspects of the surface are not faithfully reproduced due to limitations of
the measurement method, for example, an inability to track the sides of steep valleys that is in essence a form of filtering. This
topic is further discussed in Section 11.
7.2 Filters used in surface texture measurements do not have a sharp cut-off in spatial frequency above or below which
information is rejected. This gradual attenuation of high or low spatial frequency data helps avoid distortion of the measurements
that can occur when strong features are close to the filtration limits. The point on the transmission curve at which the transmitted
signal is reduced to 50 % is referred to as the cut-off wavelength, λc, of the filter, filter (Fig. 3.). For measurements made using
a stylus instrument (Section 11), the choice of λc depends on the sampling frequency and the speed at which the stylus moves over
–1
the surface. For example, measurements made at intervals of 0.01 mm from a device moving at 1 mms will generate data at a
frequency of 100 Hz. Increasing the sampling interval to 0.1 mm will reduce the frequency at which data are obtained to 10 Hz.
A high-pass filter that suppresses all frequencies below 10 Hz effectively removes any surface irregularities larger than 0.1 mm
spacing from the data. Hence, filters can be used to bias the experimental data towards detecting profile (surface texture after
applying a low-pass to filter the data), waviness (after applying a band-pass filter), and roughness (after applying a high-pass filter).
Measurement conditions are set for filters according to the respective values of the sampling interval, measurement speed, and
filtration limits, according to ISO 3274.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
F2791 − 14
FIG. 2 Summary of Stages Involved in Analysis of Measured Profile to Obtain a Roughness Profile
FIG. 3 50 % Reduction in Transmission Curve
7.3 ISO 4287 specifies that 2-D roughness parameters need to be determined over five sequential sampling lengths, lr, unless
otherwise specified. This grouping of five serial sampling lengths is referred to as the evaluation length, ln. The sampling length
varies according to the length scale of the texture being assessed; larger features require a long sampling length. Guidance as to
which sampling length to use for a given range of feature sizes is shown in Table 1. It may be necessary to perform one or more
F2791 − 14
TABLE 1 Guide to Choosing Sampling Lengths for the
Measurement of Periodic Profiles
NOTE 1—Based on ISO 4288. The evaluation length is usually taken to
be five times the sampling length.
Mean profile element Sampling length,
width, RSm (μm) lr (μm)
13 < RSm # 40 80
40 < RSm # 130 250
130 < RSm # 400 800
400 < RSm # 1300 2500
1300 < RSm # 4000 8000
TABLE 1 Guide to Choosing Sampling Lengths for the
A
Measurement of Periodic Profiles
Mean profile element Sampling length,
width, RSm (μm) lr (μm)
13 < RSm # 40 80
40 < RSm # 130 250
130 < RSm # 400 800
400 < RSm # 1300 2500
1300 < RSm # 4000 8000
A
Based on ISO 4288. The evaluation length is usually taken to be five times the
sampling length.
iterations to identify the best value for lr. This can be achieved by calculating the mean width of a profile element, RSm (see Fig.
4), from a measured profile where the value for lr is based on a best guess. This initial iteration will enable a new value for RSm
to be determined and that leads to a potential revision of lr according to Table 1.
8. Quantification of Surface Profiles
8.1 Parameters that are used to characterize 2-D surface profiles are grouped as:
8.1.1 Amplitude parameters, which are measures of variations in profile height. These parameters are split into two subclasses:
averaging parameters, and peak and valley parameters;
8.1.2 Spatial parameters, which describe in-plane variations of surface texture; and
8.1.3 Hybrid parameters, which combine both amplitude and spatial information, forinformation (for example, mean
slope.slope).
8.2 Ra—The most widely used parameter to quantify surface texture is the arithmetical mean deviation of the absolute ordinate
values, Z(x),
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.