4. Surface & Metrology

Transcription

1 4.

2 Index Surface roughness Friction, wear Surface treatment & Coating Metrology

3 Surface Structure ( 표면구조 ) Contaminant ( 불순물 ) Oxide ( 산화물 ) Fe 2 O 3, Al 2 O 3, Cu 2 O, CrO Surface structure( 표면구조 ): work hardened layer( 가공경화층 ), residual stress( 잔류응력 ) Metal substrate( 모재 ) nm Contaminant nm Oxide μm Surface structure stress Metal substrate

4 Surface Roughness ( 표면거칠기 ) Ra : Arithmetic average ( 산술평균 ) Rq : Root mean square average ( 제곱평균 ) Rt : Maximum peak-to-valley ( 최대높이 ) Ra Rt 1 n n i 1 z i z p z v Rq 1 n n i 1 2 z i Rz : Five highest peaks - lowest valleys [JIS] (5 점평균 ) Rz 5 1 z pi 5 i 1 z vi z 1 z 2 profile z p center line stylus z v z n = =

5 Surface Roughness Professor Christopher Brown at IMTS 2012 What is roughness? : Measuring roughness : Calculating roughness :

6 Stylus Profiling Line Profiling: Senses Z(X), Contact Stylus Scanning Stylus Instrument: Surface -> Stylus tip -> Transducer -> Electric signal ortable Surface Roughness Tester :

7 Gaussian filter σ Primary profile Low pass filter Waviness profile transmission wavelength Roughness profile 7

8 Cut off transmission The cut-off wavelength is transmitted at 50%. Cut-off values are, 0.08, 0.25, 0.8, 2.5 mm, [ISO 4228] for profiles and, 0.1, 0.2, 0.25, 0.5, 0.8, 1.0 mm, [ISO ] for surfaces. Cut-off Waviness Roughness 0.2 mm 0.4 mm 0.8 mm 8

9 Surface roughness symbols Surface texture symbol ISO Roughness Without removal Casting, Forging 50 Roughness, Ra 0.8 μm Machining (removal) required 0.8 Old style 50 μm 25~12 μm 6~1.5 μm 0.8~0.2 μm

10 White Light Interferometric Microscope Coherence Scanning Interferometry = Vertical Scanning Interferometry = Scanning White Light Interferometry Full image section obtained at camera frame rate Height data compute from interference information Objective Lens Intensity vs. Z Reference Surface Beamsplitter Test Surface Z-scan Range ~ 1 mm

11 Confocal Microscopy Raster scan XY with laser for each image section Scan optics (sample) vertically to build 3D Confocal Microscopy : (26 min)

12 Friction ( 마찰 ) Friction is defined as the resistance to relative sliding between two contact bodies under load. Adhesion( 융착 ) theory of friction: Two clean surfaces contact at only small area. N F Friction force, F A r <<A A r <A A r ~A Forging Sheet forming Drawing Bending Metal cutting Real area of contact, A r Sliding Microscopic friction Normal force, N

13 Wear( 마멸 ) Adhesive ( 융착 ) Abrasive ( 연삭 ) Corrosive ( 부식 ) Fatigue ( 피로 )

14 Lubricant ( 윤활 ) Oil, Graphite, Grease If Film thickness > 3 x Roughness Hydrodynamic Else Boundary lubrication Velocity x Viscosity / Load Film thickness / Roughness How lubricant

15 Surface treatment ( 표면처리 ) Shot peening Impact with high speed metal ball Compressive residual stress Roller burnishing Roller Compressive residual stress Burnishing

16 Surface Coating Wheel is coated by Cu (copper) Ni (nickel) Cr(chromium)

17 Surface Coating ( 표면코팅 ) Physical vapor deposition(pvd, 물리증착 ): deposit vaporized material onto workpiece surface in vacuum and at high temperature. PVD Lab. PVD Tools

18 Surface Coating Electroplating( 전기도금 ): Metal ions(+) in a solution are moved by an electric field to coat an cathode( ) electrode. (+) (-) Zn Zn ++ SiO -- 4 Zn ++ SiO -- 4 H + Electroplating

19 Surface Coating Anodizing( 양극처리 ): an electrolytic oxidation process used to increase the thickness of the natural oxide layer on the surface of metal parts connected to anode(+). Aluminum alloy are anodized to increase corrosion resistance, surface hardness, and to allow coloring. (-) (+) O 2 - Al O 2 - Air bubble Anodizing

20 Surface Coating Phosphate conversion coating ( 인산염피막 ) are used on steel parts for corrosion resistance, lubricity, painting foundation. Phosphoric acid( 인산 ) chemically react with the surface of the part being coated to form a layer of insoluble, crystalline phosphates. Manganese phosphates( 인산망간 ) are used both for corrosion resistance and lubricity. Iron phosphates( 인산철 ) are typically used as a base for further coatings or painting. Zinc phosphates( 인산아연 ) are used for rust proofing (P&O), a lubricant base layer, and as a paint/coating base.

21 Metrology ( 측정 ) Accuracy( 정확도 ): agreement between the measured and true value Precision( 정밀도 ): repeated measurements under unchanged conditions show same value Resolution( 해상도 ): smallest dimension read Sensitivity( 감도 ): smallest difference in dimensions distinguished

22 Measuring instruments ( 측정기 ) Vernier calipers 25μm Micrometer 2.5μm Dial indicator 1μm

23 Measuring instruments go gage & no-go gage Combination square( 조합직각자 ) Telescopic gage( 신축형게이지 ) Gage block

24 CMM Coordinate measuring machine (CMM, 3 차원측정기 ) 0.01μm CMM

25 Laser interferometer ( 레이저간섭계 ) He Ne Laser wave λ=0.633μm 0.001μm Position accuracy is measured by laser interferometer. Reference mirror + Laser beam 1. Wave is divided 2. Returning wave is recombine Bright λ/4 Moving mirror 3. Measures the superposition of the two waves traveled different paths Laser Interferometer + Dark

26 3D Scanner 3D Scanner 100μm Calculate 3D coordinate of point by principle of triangulation. Collect point data of real parts to construct 3D model. 3D scanner

27 Statistical quality control ( 통계적품질관리 ) Data is represented by the histogram and normal distribution curve. Control charts represent the variations of a process over a period of time. m σ SPC

28 Reference CMM: Duckin 3D Scanner: 3dSystems