Presentation on theme: "Dept. of Mechanical Engineering, IISc"— Presentation transcript:
1 Dept. of Mechanical Engineering, IISc ME-255 : PRINCIPLES OF TRIBOLOGYSurface Properties - Measurement TechniquesProfilometerPresented byBalasenthil DSr.No
2 CONTENTS Introduction Types of Profilometer Working Principle ContactNon - ContactWorking PrincipleOptical Principle BasicsModes of OperationSystem PerformancesRange , Resolution & AccuracySurface ParametersSurface Topography & Amplitude ParametersIIScMeasurement Examples
3 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
5 Non - Contact Profilometer Pattern Projection MethodsFringe ProjectionFourier ProfilometryMoireContact & Pseudo – Contact ProfilometerStylus ProfilometerAtomic Force MicroscopyScanning Tunneling Microscopy
6 Contact Profilometer Height from 10 nanometres to 1 millimetre Radius of diamond stylus from 20 nm to 25 μmHorizontal resolution is controlled by the scan speed and data signal sampling rate.Contd ...
7 Contact Profilometer Advantages & Disadvantages Acceptance & Easy to UseSurface IndependenceResolution : The stylus tip radius can be as small as 20 nanometresDirect Technique : No modelling required.Not suitable for very soft (or even liquid) and easily damageable surfaceVery hard and damage surface can damage the stylusOnly 2D
8 Non - Contact Profilometer Uses beams of light to read a surfaceThey shoot a beam out and measure the time it takes to return.no wear since none of its parts touch anythingContd …
9 Non - Contact Profilometer Advantages of optical profilometersGood Resolution: Vertical resolution is usually in the nm levelHigh SpeedReliability : cannot be damaged by surface wear or careless operatorsSpot size or lateral resolution ranges from a few micrometres down to sub micrometre.Contd …
10 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.
11 Working Principle of Profilometer (Non - Contact Optical Profilometer) Contd …
12 Working Principle of Profilometer (Non - Contact Optical Profilometer) A light beam is split, reflecting from reference (known/flat) & test material.Constructive and destructive interference occursForms the light and dark bands known as interference fringes.The optical path differences are due to height variances in the test surface.Contd …
13 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
14 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.
16 Modes of Operation (Non - Contact Optical Profilometer)
17 System PerformancesRange: Highest vertical distance the profiler can measure.Resolution: Smallest distance the profiler can accurately measure.Lateral ResolutionVertical ResolutionAccuracy: How closely a measured value matches the true value & can be obtained by frequent calibration.
18 Surface ParametersSurface Topography: 3D representation of geometric surface irregularities.Contd …
19 Surface Parameters Roughness : Closely spaced irregularities Waviness : More widely spaced irregularitiesError of Form : Long period & non cyclic deviationsFlaws : Discrete & infrequent irregularitiesRoughness & Waviness comprise the Surface TextureContd …
20 Surface Parameters Amplitude Parameters: Contd … Term Definition Use The roughness average (mean height)Gives roughness of the machine surfaceRqRMS roughnessDescribes the finish of optical surfaceRp & RvMax profile peak & max profile valley depthRa - info of friction & wearRv - retaining of lubricantRtMax height of surfaceGives overall roughness of the surface
21 Surface Parameters Amplitude Parameters: Term Definition Use Rz Average max height of the profileEvaluating surface texture on limited access surfacesRskSkewness - measure of asymmetry of the profile about the mean line.Gives load carrying capacity, porosity & characteristic of non-conventional machining processes.
22 Profilometers @ IISc Optical surface profilometer Make – Veeco NT1100 Type – Non Contact typePrinciple of OperationVSI g interferometry (VSI)Phase-shifting interferometry (PSI).RangeVSI – 2mmPSI – 160nmResolutionVertical Resolution : PSI – 3Å & VSI – 3nmLateral Resolution -- Function of magnification objective and the detector array size you choose
23 Profilometers @ IISc Nanoscience Profilometer Film thickness measurement from 5 microns down to 300 nm or less4 million pixel camera for high resolutionAuto-range and auto-fringe-find for ease of use of Single mode of operation over all scan ranges.
24 Measurement Examples Some of the profiles obtained are shown below: 600 GRIT SIZE:UPD (in 2D): UPD (in 3D)
25 Measurement Examples Surface of steel Block Reflection Intensity 3D Image
26 Measurement Examples Pit on a thin iron plate 2D image Plate thickness 0.7mm(Depth mm)