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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: [email protected]
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.