dept. of mechanical engineering, iisc me-255 : principles of tribology surface properties -...
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Dept. of Mechanical Engineering, IISc
ME-255 : PRINCIPLES OF TRIBOLOGY
Surface Properties - Measurement Techniques
Profilometer
Presented by
Balasenthil D
Sr.No. 08993
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CONTENTS
• Introduction• Types of Profilometer
Contact Non - Contact
• Working Principle Optical Principle Basics Modes of Operation
• System Performances Range , Resolution & Accuracy
• Surface Parameters Surface Topography & Amplitude Parameters
• Profilometers @ IISc• Measurement Examples
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INTRODUCTION
• Definition.
- A profilometer is a device used to measure the roughness of a surface.
- Gives difference between the high and low point of a surface in nanometres.
• Types of Profilometers.
Non - Contact ProfilometersContact Profilometers
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• Optical Methods Vertical Scanning Interferometry Phase - Shifting Interferometry Differential Interference Contrast Microscopy
• Focus Detection Methods Intensity Detection Focus Variation Differential Detection Critical Angle Astigmatic Method Focault Method Confocal Microscopy
Contd…
Non - Contact Profilometer
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• Pattern Projection Methods Fringe Projection Fourier Profilometry Moire
Non - Contact Profilometer
Contact & Pseudo – Contact Profilometer
• Stylus Profilometer• Atomic Force Microscopy• Scanning Tunneling Microscopy
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Contact Profilometer
• Height from 10 nanometres to 1 millimetre• Radius of diamond stylus from 20 nm to 25 μm• Horizontal resolution is controlled by the scan speed
and data signal sampling rate.
Contd ...
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Contact Profilometer
• Advantages & Disadvantages
Acceptance & Easy to UseSurface IndependenceResolution : The stylus tip radius can be as small
as 20 nanometres Direct Technique : No modelling required. Not suitable for very soft (or even liquid) and
easily damageable surface Very hard and damage surface can damage the
stylus Only 2D
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Non - Contact Profilometer
• Uses beams of light to read a surface• They shoot a beam out and measure the time it takes to
return. • no wear since none of its parts touch anything
Contd …
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• Advantages of optical profilometers
Good Resolution: Vertical resolution is usually in the nm level
High Speed
Reliability : cannot be damaged by surface wear or careless operators
Spot size or lateral resolution ranges from a few micrometres down to sub micrometre.
Contd …
Non - Contact Profilometer
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Non - Contact Profilometer
• Limitations:
Limited by very high slopes, where the light is reflected away from the objective, unless the slope has enough texture to provide the light.
Surface Modelling is required to convert the digital code to human usable data.
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Working Principle of Profilometer(Non - Contact Optical Profilometer)
Contd …
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• A light beam is split, reflecting from reference (known/flat) & test material.
• Constructive and destructive interference occurs
• Forms the light and dark bands known as interference fringes.
• The optical path differences are due to height
variances in the test surface.
Contd …
Working Principle of Profilometer(Non - Contact Optical Profilometer)
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Working Principle of Profilometer(Non - Contact Optical Profilometer)
• Constructive interference areas as lighter and the destructive interference areas as darker.
• Light to dark fringes above represents one-half a wavelength of difference between the reference path and the test path.
Contd …
Interference Image
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Working Principle of Profilometer(Non - Contact Optical Profilometer)
• From the above Interference Image:
Lower portion is out of focus means less interference.
Greatest contrast means best focus.
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• Phase Shifting Interferometry (PSI) Mode• Vertical Scanning Interferometry (VSI) Mode
Contd …
Modes of Operation(Non - Contact Optical Profilometer)
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Modes of Operation(Non - Contact Optical Profilometer)
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• Range: Highest vertical distance the profiler can measure.
• Resolution: Smallest distance the profiler can accurately measure.
Lateral Resolution Vertical Resolution
• Accuracy: How closely a measured value matches the true value & can be obtained by frequent calibration.
System Performances
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• Surface Topography: 3D representation of geometric surface irregularities.
Contd …
Surface Parameters
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• Roughness : Closely spaced irregularities
• Waviness : More widely spaced irregularities
• Error of Form : Long period & non cyclic deviations
• Flaws : Discrete & infrequent irregularities
• Roughness & Waviness comprise the Surface Texture
Contd …
Surface Parameters
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• Amplitude Parameters:
Contd …
Surface Parameters
Term Definition Use
Ra The roughness average (mean height)
Gives roughness of the machine surface
Rq RMS roughness Describes the finish of optical surface
Rp & Rv Max profile peak & max profile valley depth
Ra - info of friction & wearRv - retaining of lubricant
Rt Max height of surface
Gives overall roughness of the surface
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Surface Parameters
• Amplitude Parameters:
Term Definition Use
Rz Average max height of the profile
Evaluating surface texture on limited access surfaces
Rsk Skewness - measure of asymmetry of the profile about the mean line.
Gives load carrying capacity, porosity & characteristic of non-conventional machining processes.
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• Optical surface profilometer
Make – Veeco NT1100 Type – Non Contact type Principle of Operation
• VSI g interferometry (VSI)• Phase-shifting interferometry (PSI).
Range • VSI – 2mm• PSI – 160nm
Resolution• Vertical Resolution : PSI – 3Å & VSI – 3nm
Lateral Resolution -- Function of magnification objective and the detector array size you choose
Profilometers @ IISc
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• Nanoscience Profilometer
Film thickness measurement from 5 microns down to 300 nm or less
4 million pixel camera for high resolution Auto-range and auto-fringe-find for ease of use of
Single mode of operation over all scan ranges.
Profilometers @ IISc
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Measurement Examples
• Some of the profiles obtained are shown below:
600 GRIT SIZE:
UPD (in 2D): UPD (in 3D)
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• Surface of steel Block Reflection Intensity
• 3D Image
Measurement Examples
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• Pit on a thin iron plate 2D image
• Plate thickness 0.7mm• (Depth 0.14494mm)
Measurement Examples
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• 3D image
Measurement Examples
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• Research Papers :
T.V.Vorburger, J.Raja.
Surface Finish Metrology Tutorial
June 1990 WYKO Surface Profilers Technical Reference manual
September 1999, Version 2.2.1
• Webpage
Profilometer, Wikipedia
http://en.wikipedia.org/wiki/Profilometer
References
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THANK YOU