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Unlicensed use of the contents of this lecture outside MECH 213 Unlicensed use of the contents of this lecture outside MECH 213 is illegalis illegal..

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Fax: 613-533-6489jeswiet@me.queensu.ca

The fine printThe fine print

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MANUFACTURING ENGINEERING

MECH 213

Queen’s University, Mechanical Engineering

© J. Jeswiet

GG’’dayday everyone.everyone.

Lecture 6

Topics:Topics:•• Surface Roughness IISurface Roughness II

•• A brief overview of current trends in metrologyA brief overview of current trends in metrology

Surface Metrology

surface creation(manufacture)

surface behavior(performance)

surface measurement and analysissurface measurement and analysis(for functional correlations)(for functional correlations)

surface texturesurface texture

summarysummary

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Vertical height between max/minRt

ISO 4287, DIN 4768SkewnessSsk

DIN 4762Maximum peak heightRp

ISO 4287, DIN 4768RMS of roughness averageRq

DIN 4786Mean peak-to-valley heightRz (DIN)

KurtosisKku

ISO 4287, BS 1134, DIN 4768Maximum roughness depthRy

DIN 4768Maximum peak-to-valley heightRmax

ISO 4287, BS 1134, DIN 4768Ten point heightRz (ISO)

ISO 4287, BS 1134, ANSI B46.1, DIN 4768

Roughness averageRa

STANDARDPARAMETER DESCRIPTION

Vertical height between max/minRt

ISO 4287, DIN 4768SkewnessSsk

DIN 4762Maximum peak heightRp

ISO 4287, DIN 4768RMS of roughness averageRq

DIN 4786Mean peak-to-valley heightRz (DIN)

KurtosisKku

ISO 4287, BS 1134, DIN 4768Maximum roughness depthRy

DIN 4768Maximum peak-to-valley heightRmax

ISO 4287, BS 1134, DIN 4768Ten point heightRz (ISO)

ISO 4287, BS 1134, ANSI B46.1, DIN 4768

Roughness averageRa

STANDARDPARAMETER DESCRIPTION

3rd order surfaceRmaxRt

Ra, Rt, Rmax, Ry

1000

X

100X

RRyy

Ra

Rudimentary statistics:

0 10 20 30 40 50 60 70 80 90 100

freq

uenc

y

%

Histogram

Amplitude Density Function, ADF , p(y):

For Surface Roughness we look at amplitudes of peaks, so we call the PDF an Amplitude Density Function, ADF

ie: n

o. o

f stu

dent

s

Mark achieved

Probability Density Function, PDF

Interpretation: a probability density function can be seen as a "smoothed out" version of a histogram.

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Rq: Root Mean Square AverageRRqq is calculated by taking the root mean square the series of measurements of deviations from the centreline.

Rq is the standard deviation, σ, of Ra

Reference: page 19 of ISO 4287

Advantage?Advantage?

• standard deviation

• surfaces (a) & (b)

• Rq of (a) > Rq of (b)

(a)

(b)

RRqq is more sensitive to high and lowmore sensitive to high and low peaks, and gives more weight to higher peaks.

For a Gaussian distribution of heights, Rq = 1.25 Ra.

Amplitude Density Function, ADF , p(y):

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( ) ( )5

1064297531 RRRRRRRRRRz+++−++++

=

TenTen--point height, point height, RRzz:

the average of the five highest and the five deepest valleys within the sampling length, measured from a line parallel to the mean line.

l, sampling length

R1

R2

R3 R4

R5

R6

R7

R8

R9

R10

ISO 4287, DIN 4768

Rz: another surface parameter

Compare Compare RRzz to Rto Rtt..

RRzz: average of maximum values. : average of maximum values.

can be used for a surface that has subsequent metal removal operations such as lapping and honing,shows how much material can be removed before the part size reaches a limit,can be affected by dirt or imperfections.

RRtt and and RRzz::

( ) ( )5

1064297531 RRRRRRRRRRz+++−++++

=

TenTen--point height, point height, RRzz: l, sampling length

R1

R2

R3 R4

R5

R6

R7

R8

R9

R10

Rt

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The R parameters do not give any information about surface irregularity shapes or spacing.

For that we can use SKEWNESS SKEWNESS and KURTOSISKURTOSISwhich are statistics functions.

Skewness: DESIGN:ok as a

Bearing Surface

SkewnessSkewness of data; measure of asymmetry of data. ISO 4287, page 23..

Negative Skewness: A concentration of the material near the top of the profile signifying a plateau like surface

negative skewness

negative

positive skewness

positive

Skewness is described by: ∫∞

∞−= p(y)dyy

R1S 3

3q

k

Sk = 0; Gaussian distribution

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Kurtosis:

KurtosisKurtosis; measure of sharpness of peak distribution (Greek for hump);or a measure of the sharpness of the probability function.

orKurtosis:

“the degree of peakedness of a probability function near the mode”

∫∞

∞−= p(y)dyy

R1K 4

4q

Coefficient of Kurtosis, K:Coefficient of Kurtosis, K:

A sharp amplitude distribution curve indicates large, sharp peaks and large, sharp peaks and valleysvalleys; kurtosis > 3.

KURTOSISKURTOSIS

A broad, flat amplitude distribution indicates many small, rounded many small, rounded peaks and peaks and valleysvalleys in the profile; kurtosis < 3.

Gaussian Distribution: K = 3

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Bearing ratio curve: Abbot - Firestone curve.

(a) 25% of surface is carrying, bearing the load.

(a)

(b) 50% of the surface is bearing the load.

(b)

Bearing ratio0 25 50 100, %

DETAILS OF THE MEASUREMENTS IN LAB 201.

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λc , the filter cut-off length is used to differentiate between the roughness and waviness.

The cut-off length should be at least 2.5 times the peak-to-peak spacing of the profile roughness.

This means that at least two peaks and valleys are found in each cut-off length.

If a profile is assessed over a length equal to 6 times the cut-off length, as shown, an adequate number of peaks & valleys is included in the data.

stylus Some details about surface Some details about surface roughness measurements:roughness measurements:

Standards organizations have set up a number of preferred traversing lengths.

λc = 0.8mm (0.030 inches) is the most commonly used cut-off length for engineered surfaces

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An example of output from the equipment in a laboratorySo what will you see in laboratory 201?

INFORMATION ABOUT THE “LAY” ON DRAWINGS –

“direction” of surface roughness.

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More Surface Roughness More Surface Roughness TolerancingTolerancing for drawingsfor drawings

For ISO - metricFor ISO - metric

“lay” symbols:

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The latest in Surface Metrology

Scanning Laser Microscope

25 μm Spatial Resolution (X & Y)12 μm Vertical Resolution (Z)

Triangulation Laser Sensor

X/Y Positioning Tables

Anti-Vibration Table

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Techniques now exist which allow the observation of very small variations.

For instance, optical methods have been successfully applied to soft materials such as paper:

scanning conoscope probe [SCP] of paper with two crossed grooves left by a ballpoint pen

10x

5x

1x

St 37 - 2 K X 5 CrNiMo 18/10 42 CrMoS 4 100 Cr 6

Measured textures (UBM)

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Visual & Statistical InspectionInspections Performed using Surfrax and Matlab

Thank you for your attentionThank you for your attention

On to the next lecture

MANUFACTURINGOn to the next lectureOn to the next lecture

MANUFACTURINGMANUFACTURING

Questions?Questions?

The End for Surface Roughness LecturesThe End for Surface Roughness Lectures

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Filtering: waviness, roughness

Trace – leveled with the mean set to zero

Waviness –“Roughness removed”

Roughness –“Waviness removed”

As-Measured Profile turned surface

Stylus moves back and forth

Laboratory 201 Laboratory 201 –– Metrology:Metrology:

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MetrologyMetrology is now significance to the

Electronics, Optoelectronics & BiomedicalElectronics, Optoelectronics & Biomedical Industries.

Advances in Metrology have occurred with the evolution of Manufacturing Technology in:

new production techniquesnew production techniques and

new measurement techniquesnew measurement techniques.

Master CD with sinusoidal profiles

In Nanotechnology, the overall dimensionsdimensions of an object decrease dramaticallydecrease dramatically and the importance of the surfacesurfacerelative torelative to that of the volume increasesvolume increases.

ie: in a nanocrystal, a 1000 atom cluster has roughly 25% of its atoms at the surface, therefore the properties of the solid are strongly influenced by the properties of the near surface.

Size matters:

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and in the theand in the theBiomedical IndustryBiomedical Industry

Characterizing a surface in terms of depth regimes:

WPI’s SLM measuring an experimental runway pavement at NASA Wallops Space Flight Facility

Courtesy Chris Brown WPI

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Texture measurement (UBM)

measurement range: 500 x500 µmsampling interval: 2 µmstylus: 5 µm radius.

Supplementary information

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where l is the sampling length and y is the ordinate of the profile

Average Roughness Ra, AA or CLA is

l

ln

nwhere Ym = mean Y

Quick Review Quick Review

The shape and relative size ot the stylus can have an effect upon the readings:

The stylus can also become dull and have an effect upon the readings:

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Effect of Tip Radius

Numerical 5 um radius

As Measured (2 um radius)

Ruler Length (um)

Rel

ativ

e L

engt

h

1.002

1.004

1.006

1.008

1.010

1.012

1.014

1.000

from Mark Malburg/ Chris Brown, WPI

Thermal spray coatingsEMPA - Thun, Switz.

Surface measurement conditions

scanned region 500 x 500 µmstylus radius 5 µmsampling interval 2 µmmaximum range for z-axis ± 50 µmnominal resolution for z-axis 50 nm

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Conventionalprofile measurement

stylusnormal (1.4mN)force

conic section(90 degree)

spherical tip(5μm)

workpieceSampling internal:Vertical resolution:Tracing length:Filtering?

(88nm)(1nm)(0.56mm)

profile:

100μm

10μm

Some comments about design and surface roughness:

or why should designers worry about itwhy should designers worry about it?

friction and wear between two unlubricated surfaces increases with surface roughness.

smooth surfaces reduce the danger of seizure between unlubricated surfaces.

if a surface is too smooth it may not sustain an oil film.

if a surface is too rough the sharp peaks will break through the lubricating layer.

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Instruments – used for full profiling

Type I - profiling (mostly z=z(x)), contactcontact, stylus: (e.g., Mahr/Federal - Perthometer, Taylor Hobson - Talysurf)

Type II - profiling nonnon--contactcontact (mostly z=z(x,y)) scanning laser: • horizontal: triangulation, focus (e.g., UBM) • vertical: confocal (e.g., UBM, Olympus, Zeiss), • interferometric (e.g., Zygo, Wyko, Phase Shift)• gray scale, structured light.

Type III - scanned probe microscopy AFM, STM (e.g., Veeco (Digital Instruments - Nanoscope),

German car industryCummins; American engine manufacturer

It turns out that not all industries use the same parameter

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Parameters used by French car industry

With the drive to produce 3 D surfaces for specific functions there is now an interest in developing standards for 3 D roughness profiles.

FractalsFractals are an example of a technique that can be used to quantify 3 D surfaces.