ME 472 Engineering Metrology

Transcription

1 ME 472 Engineering Metrology and Quality Control Chp 6 - Advanced Measurement Systems Mechanical Engineering University of Gaziantep Dr. A. Tolga Bozdana Assistant Professor

2 Coordinate Measuring Machines (CMMs) provide precise and accurate measurements of 3D coordinates of components using small- head touching probes via movable axes. Coordinate Measuring Machine (CMM) Coordinate Measuring Machine 1

3 5-Axis Scanning Applications using CMM Helix Scan Gasket Scan Blade Sharp-Edge Sweep Scan Sweep Scan Rapid Head Touches Round the Blade Scan 2

4 Use of Light Electromagnetic radiation (EMR) consists of self-propagating electromagnetic waves (such as light), which can travel through vacuum, and sometimes matter as well. EMR has electrical and magnetic field components, which oscillate in phases perpendicular to each other and also to the direction of propagation of the wave. EMR behaves as both wave and particle. The particles are photons. As waves,emr has both frequency and wavelength. Electromagnetic spectrum is the range of all electromagnetic frequencies. Frequencies can be grouped by their use (such as radio waves, visible light, x-rays rays, microwaves, etc.) Chart shows the range of electromagnetic spectrum and common uses for different parts of the spectrum. Frequency is shown on the left, and wavelength is on the right.

5 Introduction to Interferometry Interferometry is the technique of superimposing (i.e. interfering) two or more waves in order to detect differences between them. It is applied in a wide variety of fields including astronomy, fiber optics, optical metrology, seismology, oceanography, quantum mechanics, and plasma physics. From metrology viewpoint, it is a series of non-contact techniques using the interference of light waves to determine surface shape and transmission properties. Principle of Interferometry Whenever two waves comes together at the same time and place, interference occurs. If both waves are in phase (i.e. their crests coincide) they will add together to form a single wave with higher crest (i.e. larger amplitude). This is called constructive interference. Destructive ti interference occurs when the waves are out of phase (i.e. the crest of one wave coincides with the through of other wave). Therefore, the amount of interference depends on both the amplitudes of those waves and their frequencies (the degree to which their respective crests are in phase with each other). 4

6 Principle of Interferometry Simple interferometry t setup includes the use of parallel l beam of monochromatic light. For this purpose, an optical flat (a disc of stress-free glass or quartz with a highly polished surface) is placed on top of the surface to be measured at a very small angle of θ. The light beam from source (S) is projected onto the optical flat. Two reflected components of light wave (partially reflected from a and b) are collected, and hence the combined view is obtained. Further along the surface at a distance of half-wavelength (λ/2) and due to the angle θ, the ray (light beam) leaving source S will again split into two components whose path lengths are different. Therefore, the surface will be crossed by apattern of dark bands (fringes), i which h are straight for the case of a flat surface. interference fringes (red bands) intensity t ( λ ) t sinθ = 2 time 5

7 Straight Fringe Pattern: Such pattern indicates a very flat surface. Suppose that the wavelength (λ) is µm. Thus, the flatness is µm. Curved Fringe Pattern: In such cases, two red lines tangent to the center of two adjacent fringes are drawn. The blue line indicates the center of a single fringe. If the distance between red lines (a) is5.02µm and the distance between red and blue lines (b) is 1.24 µm, then the flatness is µm. b Fringe Analysis a Flatness = ( λ 2) Flat Surface Flatter Spherical µ, µ Flatness = ( λ 2 ) ( b a ) Circular Fringe Pattern: This pattern is obtained when the surface to be measured is convex or concave. So, the total distance between the peak and the deepest point (i.e. height) can be calculated. Since there are 5fringes, then the height is found to be µm. Height = λ Optical Flat Spherical ( 2) ( # of fringes) 6

8 Fringe Analysis Software In most cases, the fringe patterns are quite sophisticated. So, special-purpose purpose software/programs with advanced techniques may be required for accurate fringe analysis. 7

9 Common Types of Interferometers Various systems are available for different type of measurements based on the application area. Michelson Interferometer Mach-Zehnder Interferometer Sagnac Interferometer Fabry-Perot Interferometer 8

10 Digital (Light) Microscopy Nikon Eclipse ME-600 Digital Microscope (1.3 megapixel color resolution imaging at a rate of 15 fps) 9

11 Electron Microscopy Recently have emerged as an advanced technology in 1 cm 1 mm 100 µm 10 µm 1 µm 100 nm 10 nm nm 1 nm 1 Å) 0.1 (1 many engineering fields, electron microscopy allows Light Microscopy Electron Microscopy to visualize objects that are as small as 0.1 nm (1Å). Unlike light microscopy, the object is not illuminated with light, instead bombarded by electrons. Transmission Electron Microscopy (TEM) is used to analyse the inner structure of objects (such as tissues, cells, viruses) while Scanning Electron Microscopy (SEM) is used to visualize the surface of tissues, macro-molecular aggregates and materials. Both TEM and SEM use asource(an electron gun), lenses (electro-magnetic lenses that deflect electrons), a condenser (to concentrate beam), and an objective (to focus on the thing to be measured). 10

12 Examples of Electron Microscopy pollen escherichia hi (coli basili) nylon stocking fibres Micro-scale circuiting uranium waste bacteria witherite (barium carbonate crystal)

13 Use of Laser The term LASER is an acronym for Light Amplification by Stimulated Emission of Radiation. It is a device that emits light (electromagnetic radiation) through a process of optical amplification based on the stimulated emission of photons. Different types of laser are used for research and industrial purposes (such as metal cutting, welding, dynamic alignment or positioning, dimensional measurements, nondestructive testing, lithography, medical treatments, military applications, and so on). For more information on type of lasers and their specific use: 12

14 Laser Displacement Sensors with CCD Detectors laser scanner laser pointer Laser-triangular sensor uses a high-speed, noncontact line-range laser probe to perform complex-part profile measurements. Laser beam is spread out into a plane that forms a line of light on the part surface. CCD (Charge Coupled Device) sensor mounted in the probe takes range measurements over the entire line of laser light at the same time (instead of measuring just one point), which dramatically decreases scan time. 13

15 Laser Interferometers Compared with common interferometers, laser interferometry provides precise and accurate optical measurements as well as positioning and movement systems. Laser Interferometer for Vision Laser Interferometer System for Precise Positioning and Accurate Measurement 14

16 Use of Sound Sound is a sequence of waves of pressure propagating through a compressible media (such as air, water or solids). During propagation, waves are reflected, refracted or attenuated by the medium. Sound waves are classified into specific ranges according to their frequencies. Acoustic is the range of human hearing. Frequency (Hz) Infrasound has the frequency of less than Elephant ( ) 20 Hz, which is the limit of human hearing. Ultrasound has frequencies of greater than 20 khz, which is not audible by humans. Mach number (M =V/C) is used to define speed of a matter (V) travelling in a medium in relation with speed of sound (C). From metrology viewpoint, sounds waves with certain frequencies and amplitudes are used in many applications (e.g. underwater, seismology, medical, NDT, infrasound, and ultrasonic inspection). Human ( ) Cat ( ) Dog ( ) Mouse ( ) Dolphin ( ) Bat ( ) Mach Numbers for Various Regimes Subsonic Transonic Sonic Supersonic Hypersonic High-hypersonic < >

17 SONAR SONAR stands for SOund NAvigation and Ranging. It is a technique using underwater sound propagation to navigate, communicate with or detect the objects. It directs a beam of sound waves downward. After the sound wave hits bottom of ocean or an object, it will bounce off and return back causing an echo. This is recorded on a depth recorder on the ship. There are two SONAR systems: Active (deploys and recevies its ownsignal) & Passive (just listening) i 16

18 Ultrasonic Testing Ultrasonic Testing (UT) uses high frequency sound energy to conduct flaw detection, dimensional inspection, material characterization, and more. UT system consists of: a pulser/receiver, a transducer, and a display software/device. Pulser/receiver produces high voltage electrical pulses. Driven by the pulser, the transducer generates high frequency ultrasonic energy, which propagates through the part in form of waves. When there is discontinuity (such as crack/flaw) in the wave path, some part of energy is reflected back from the flaw surface. Based on voltage signals of reflecting energy, loaction and size of flaws are displayed. pulser/receiver ultrasonic trasducer flaw part Typical schemes of UT a) one axis through testing b) angle testing c) one surface testing d) curve surface testing 17