surface texture - profile parameters.pdf

8/10/2019 Surface Texture - Profile parameters.pdf

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Rp, maximum profile peak height: height of the highest peak from the

mean line, defined on the sampling length.

Rv, maximum profile valley depth: depth of the deepest valley from the

mean line, defined on the sampling length.

Rz, maximum height of the profile: defined on the sampling length: this

parameter is frequently used to check whether the profile has protruding

peaks that might affect static or sliding contact function.

Ra, arithmetic mean deviation of the assessed profile: defined on the

sampling length. Ra is used as a global evaluation of the roughness

amplitude on a profile. It does not say anything on the spatial frequency

of the irregularities or the shape of the profile. Ra is meaningful for

random surface roughness (stochastic) machined with tools that do not

leave marks on the surface, such as sand blasting, milling, polishing

Rq, root mean square deviation of the assessed profile : corresponds to the

standard deviation of the height distribution, defined on the sampling

length. Rq provides the same information as Ra.

Rsk, skewness of the assessed profile: asymmetry of the height

distribution, defined on the sampling length. This parameter is important

as it gives information on the morphology of the surface texture.

Negative values correspond to high peaks spread on a regular surface

while positive values are found on surfaces with pores and scratches. It

is therefore interesting when contact or lubrication functions are

required. This parameter does not give any information on the absolute

height of the profile, contrary to Ra.

Rku, kurtosis of the assessed profile: sharpness of the height distribution,

defined on the sampling length.

Rc, mean height of profile elements: defined on the evaluation length.

This parameter can be calculated on surfaces having texture cells or

grains. It is similar to the motif parameter R found in ISO 12085 and, in

that sense, it should be considered as a feature parameter (see ISO

25178).

Hybrid parameters

Rdq, root mean square slope of the assessed profile, defined on the

evaluation length. Rdq is a first approach to surface complexity. A low

value is found on smooth surfaces while higher values can be found on

rough surfaces having microroughness.

RPc, peak count number. Was introduced in Amendment 1. Provides the

density of peaks per unit of length.

Functional parameters

Rmr, material ratio at a given depth. This parameter gives the percentage

of material cut at a given depth from the top of the profile. The reference

may also be taken from the center line or another reference height (c0).

Rdc, profile section height between two material ratios. A stable value of

roughness height can be evaluated using Rdc(2%-98%) if outliers are

present on the surface. This calculation excludes the highest peaks that

will be worn out and the deepest valleys that will be filled in. In the

automotive industry, the material height removed during running-in can

be assessed with Rdc(1%-33%) and the void volume used for lubricant

pockets can be assessed with Rdc(25%-99%).

Material ratio calculated on the Abbott-Firestone curve.

Rmr at 2 µm below the highest peak is 10%.

Section height between 5% and 95% of material ratio is 6,5 µm.

ISO 12085 - Profile method - Motifs parameters

This standard is the international version of a French standard

established by CNOMO, a consortium involving PSA Peugeot Citroen and

Renault, during the 80s and 90s. The method is based upon a graphical

segmentation of the profile into motifs that are then quantified in height

and width. The originality and advantage of this method is the

correlation that was established between parameter values and

Roughness parameters

R, mean depth of roughness motifs

AR, mean spacing of roughness motifs

ce Texture - Profile parameters http://www.digitalsurf.fr/en/guideprofileparam

10/15/2014



functional requirements, due to a vast measurement campaign that

characterized more than 40 000 components. It is commonly called the

French motifs method or R&W parameters.

Today, these parameters are less used but the conclusions regarding the

relationship between function and specification remain important and

can be used with other parameters.

Roughness motifs

Motifs are defined on a profile as a peak-valley-peak trio and are

detected by a special segmentation method. The main part of the

algorithm is a combination procedure based upon four conditions and

controlled by a limit A. The combinations merge small and insignificant

motifs into larger ones. At the end of the procedure, significant motifs

are quantified with parameters.

Rx, maximum depth of roughness motifs

Then an upper envelope is calculated by joining roughness motifs peaks

by line segments, and the segmentation procedure is repeated on this

envelope using two limits A and B. Then waviness parameters are

calculated.

Waviness parameters

W, mean depth of waviness motifs

AW, mean spacing of waviness motifs

Wx, maximum depth of waviness motifs

Wte, Amplitude of the upper envelope

Upper envelope and Waviness motifs

Recommended motifs parameters in specification,

for each type of function

The drawback of this method is its instability as it is based on conditions

instead of mathematical basis. There is a work in progress to adapt the

watershed segmentation to profiles and replace the combination rules by

a Wolf pruning. This new motifs method should be described in ISO

16610, probably in part 43. The correlation between the two methods is

discussed in [BLATEYRON 2004]

ISO 13565-2 and ISO 13565-3 - Profile method - Surfaces having stratified functional properties


10/15/2014



This series of standards are specially aimed at characterizing stratified

surfaces produced by a two-step manufacturing process such as honing-

polishing machining. The first part of this standard series, ISO 13565-1,

defines a special double-pass filter that provides a sort of robustness

against deep holes that are common in stratified surfaces. This filter is

now superceded by the Gaussian Regression filter defined in ISO

16610-31. Part 2 defines a set of parameters called Rk-parameters that

are derived from a graphical construction on the Abbott-FirestoneAbbott-FirestoneAbbott-FirestoneAbbott-Firestone

curvecurvecurvecurve. Rk parameters should be calculated only if the Abbott curve has a

S-shape, otherwise the graphical construction may fail and parameter

values will be meaningless.

Parameters of ISO 13565-2

Rk, core roughness depth

Rpk, reduced peak height. This parameter is used to characterize

protruding peaks that might be eliminated during function.

Rvk, reduced valley depth. This parameters is used to characterize valleys

that will retain lubricant or worn-out materials.

MR1 and MR2: material ratio delimiting the core area.

Other parameters such as A1 and A2, Rpk* or Rvk* can also be

calculated for specific use.

Graphical construction of Rk parameters

Parameters of ISO 13565-3

This standard is specilized in the characterisation of stratified vertical

random components such as a valley texture with a fine plateau texture

superimposed. Here again, these parameters should be calculated only

on surfaces that comply with this description.

Rpq, Plateau Root Mean Square roughness of the profile

Rvq, Valley Root Mean Square roughness of the profile

Rmq, Material ratio at plateau-to-valley transition of the profile

These parameters can be also calculated on the primary profile, as Ppq,

Pvq and Pmq.

Other standards

ASME B46.1

This standard today is more in line with ISO standards than the previous

versions, except for some differences. The main difference is about

sampling length and averaged parameters. In ASME, all profile

parameters are defined and calculated on the evaluation length.

VDA 2006

This standard from the German automotive industry collects parameters

defined in ISO 4287 and ISO 13565 and introduces several rules that

differ from ISO. The main difference concerns the use of microroughness

filter λs that is prohibited here. It also reintroduces the parameter RmaxRmaxRmaxRmax

that was once part of ISO 4287 and is a good complement to Rz.

VDA 2007

This standard defines special parameters for the evaluation of periodic

surfaces, especially in the field of mating surfaces. It is usually referred to

as Dominant wavinessDominant wavinessDominant wavinessDominant waviness

MountainsMapMountainsMapMountainsMapMountainsMap offers several options to comply to these standards.

ISO parameters are all available but sometimes as an option (such as

the Automotive Module). ASME B46.1 is offered as a family in the

Parameter study. VDA 2006 can be implemented by disabling the

microroughness option in the Preferences.

See MountainsMap Profile and 2D Advanced Surface Texture or 2D

Automotive optional modules.

Towards a complete revision of profile standards


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New structure

In fall 2012, the WG16 group of ISO TC 213 decided to start revising

profile standards in order to align them with the ISO 25178 structure and

concepts. Basically, the new structure will consist of at least three parts:

Part 1 - Drawing indications. Will incorporate the content of ISO

1302, plus new symbols.

Part 2 - Definitions and parameters. Will include definitions of allparameters, from ISO 4287, ISO 12085 and ISO 13565, plus

several new parameters.

Part 3 - Specification operators. Will define default values, and

units of parameters.

At this stage, there is no plan to describe instruments characteristics or

calibration as this was included in ISO 25178 parts 60x and 70x, as well

as parts 7x for material measures and softgauges.

Time frame

Principles have been discussed in 2013 at the Helsinki meeting and a

first draft of Part 2 was established by a task force within the group.

Discussions will continue probably until mid-2015 when the first official

New Work Item Proposal will be issued to Geneva Central Secretariat.

Publication is not expected before 2017-2018.

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