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دانشگاه آزادواحداهواز دانشکده فنی ومهندسی Visual Liquid Penetrant Magnetic Ultrasonic Eddy Current X-ray.

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Presentation on theme: "دانشگاه آزادواحداهواز دانشکده فنی ومهندسی Visual Liquid Penetrant Magnetic Ultrasonic Eddy Current X-ray."— Presentation transcript:

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2 دانشگاه آزادواحداهواز دانشکده فنی ومهندسی

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4 Visual Liquid Penetrant Magnetic Ultrasonic Eddy Current X-ray

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6 آزمونهاي فرا صوتي كاربرد بسيار گستردهاي در تعيين نقصهاي دروني مواد دارند. از اين روش ميتوان براي تعيين تركهاي زير سطحي نيز استفاده كرد. آزمونهاي فرا صوتي علاوه بر بازرسي قطعات تكميل شده براي بازرسي كنترل كيفيت مراحل مختلف توليد قطعاتي همچون ورقهاي نورد شده نيز بكار ميروند. مباني آزمون فرا صوتي از ايجاد موجهاي صوتي توسط يك ضربان سنج استخراج شده است. روش مدرن بكار گرفته شده امروزي، التراسونيك ناميده ميشود كه علت اين نامگذاري كلمه Sona ميباشد كه در لاتين به معني صوت است.

7 در حالت كلي هر چه محيط مادي فشردهتر باشد، سرعت حركت موج صوتي در آن بيشتر است. بنابراين سرعت حركت امواج صوتي در جامدات بيشتر از سيالات ميباشد.

8 Wavelength : The distance required to complete a cycle Measured in Meter or mm Frequency : The number of cycles per unit time Measured in Hertz (Hz) or Cycles per second (cps) Velocity : How quick the sound travels Distance per unit time Measured in meter / second (m / sec)

9 Velocity Frequency Wavelength

10 Sound waves are the vibration of particles in solids liquids or gases Particles vibrate about a mean position Particles vibrate about a mean position In order to vibrate they require mass and resistance to change In order to vibrate they require mass and resistance to change One cycle Sound Waves

11 Sound cannot travel in vacuum Sound energy to be transmitted / transferred from one particle to another SOLID LIQUID GAS

12 The velocity of sound in a particular material is CONSTANT It is the product of DENSITY and ELASTICITY of the material It will NOT change if frequency changes Only the wavelength changes Examples: V Compression in steel : 5960 m/s V Compression in water : 1470 m/s V Compression in air: 330 m/s STEELWATERAIR 5 M Hz

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14 چندين نوع پروب فرستنده وجود دارد، اما همه انواع آنها داراي كريستالي است كه مستقيماً يا از طريق پوشش محافظ با ماده مورد آزمايش در تماس است. جنس بلور معمولاً از كوارتز طبيعي، تيتانات باريم، نيوبات سرب و سولفات ليتيم ميباشد. ولتاژ پلهاي كوتاه مدتي به كريستال اعمال ميشود. پروبها ممكن است قائم يا زاويهدار باشند.

15 پروبهاي زاويهدار براي فرستادن موجهاي برشي يا موجهاي ريلي به درون قطعه تحت بازرسي طراحي شدهاند. ساختمان كلي پروب زاويهاي همانند پروب عمودي است با اين تفاوت كه بلور در قطعه پرسپكسي جاسازي شده است. موج طولي بازگشتي كه در فصل مشترك پرسپكسي - فلز توليد ميشود، ممكن است به كريستال برگردد و علائم گمراه كنندهاي به وجود آورد. براي جلوگيري از اين كار ماده جذب كنندهاي همچون لاستيك در پروب جاسازي ميشود. روش ديگر اين است كه قطعه پرسپكس به گونهاي شكل داده شود كه موج برگشتي چندين بار بازتاب شود و انرژي خود را از دست بدهد و از آنجا كه ضريب جذب پرسپكس بالا است، اين امكان وجود خواهد داشت.

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24 Sound travels in different waveforms in different conditions Compression wave Compression wave Shear wave Shear wave Surface wave Surface wave Lamb wave Lamb wave

25 Vibration and propagation in the same direction / parallel Travel in solids, liquids and gases Propagatio n Particle vibration

26 Vibration at right angles / perpendicular to direction of propagation Travel in solids only Velocity 1/2 compression (same material) Propagatio n Particle vibration

27 Frequenc y 0.5MHz 1 MHz 2MHz 4MHz 6MHZ Compression Shear The smaller the wavelength the better the sensitivity

28 Velocity varies according to the material Compression waves Steel5960m/sec Water1470m/sec Air344m/sec Copper4700m/sec Shear waves Steel3245m/sec WaterNA AirNA Copper 2330m/sec

29 Elliptical vibration Velocity 8% less than shear Penetrate one wavelength deep Easily dampened by heavy grease or wet finger Follows curves but reflected by sharp corners or surface cracks

30 Produced by the manipulation of surface waves and others Used mainly to test very thin materials / plates Velocity varies with plate thickness and frequencies SYMETRICASSYMETRIC

31 Sound : mechanical vibration What is Ultrasonic? Very High Frequency sound – above 20 KHz 20,000 cps

32 K 10K 100K 1M 10M 100m Sonic / Audible Human 16Hz - 20kHz Ultrasonic > 20kHz = 20,000Hz Ultrasonic Testing 0.5MHz - 50MHz Ultrasonic : Sound with frequency above 20 KHz

33 Frequency:Number of cycles per second 1 second 1 cycle per 1 second = 1 Hertz 18 cycle per 1 second = 18 Hertz 3 cycle per 1 second = 3 Hertz 1 second THE HIGHER THE FREQUENCY THE SMALLER THE WAVELENGTH

34 1 Hz=1 cycle per second 1 Kilohertz=1 KHz=1000Hz 1 Megahertz=1 MHz= Hz 20 KHz= Hz 5 M Hz = Hz Pg 21

35 Ultrasonic Inspection defect defect echo Back wall echo CRT Display Compression Probe Material Thk initial pulse

36 The distance the sound traveled can be displayed on the Flaw Detector The screen can be calibrated to give accurate readings of the distance Bottom / Backwall Signal from the backwall

37 The presence of a Defect in the material shows up on the screen of the flaw detector with a less distance than the bottom of the material The BWE signal Defect signal Defect

38 The depth of the defect can be read with reference to the marker on the screen mm

39 A A B B C C The THINNER the material the less distance the sound travel The closer the reflector to the surface, the signal will be more to the left of the screen The thickness is read from the screen

40 Ultrasonic Inspection initial pulse defect echo CRT Display sound path Angle Probe defect Surface distance

41 Dead Zone Near Zone or Fresnel Zone Far Zone or Fraunhofer Zone

42 NZ FZ Distance Intensity varies Exponential Decay Main Beam

43 Main Lobe Side Lobes Near Zone Main Beam The main beam or the centre beam has the highest intensity of sound energy Any reflector hit by the main beam will reflect the high amount of energy The side lobes has multi minute main beams Two identical defects may give different amplitudes of signals

44 Near Zone Thickness measurement Detection of defects Sizing of large defects only Far Zone Thickness measurement Defect detection Sizing of all defects Near zone length as small as possible balanced against acceptable minimum detectable defect size

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46 What is the near zone length of a 5MHz compression probe with a crystal diameter of 10mm in steel?

47 The bigger the diameter the bigger the near zone The higher the frequency the bigger the near zone The lower the velocity the bigger the near zone

48 1 M Hz5 M Hz 1 M Hz 5 M Hz Which of the above probes has the longest Near Zone ?

49 In the far zone sound pulses spread out as they move away from the crystal / 2

50 Edge,K= dB,K=1.08 6dB,K=0.56 Beam axis or Main Beam

51 What is the beam spread of a 10mm,5MHz compression wave probe in steel?

52 1 M Hz5 M Hz 1 M Hz 5 M Hz Which of the above probes has the Largest Beam Spread ?

53 The bigger the diameter the smaller the beam spread The higher the frequency the smaller the beam spread Which has the larger beam spread, a compression or a shear wave probe?

54 A short pulse of electricity is applied to a piezo-electric crystal The crystal begins to vibration increases to maximum amplitude and then decays Maximum 10% of Maximum Pulse length

55 Pulse Length

56 The longer the pulse, the more penetrating the sound The shorter the pulse the better the sensitivity and resolution Short pulse, 1 or 2 cycles Long pulse 12 cycles

57 Pulse Length

58 5 cycles for weld testing

59 RESOLUTION in Pulse Echo Testing is the ability to separate echoes from two or more closely spaced reflectors. RESOLUTION is strongly affected by Pulse Length: Short Pulse Length - GOOD RESOLUTION Long Pulse Length - POOR RESOLUTION RESOLUTION is an extremely important property in WELD TESTING because the ability to separate ROOT GEOMETRY echoes from ROOT CRACK or LACK OF ROOT FUSION echoes largely determines the effectiveness of Pulse Echo UT in the testing of single sided welds.

60 Good resolution

61 Poor resolution

62 The bigger the grain size the worse the problem The higher the frequency of the probe the worse the problem 1 MHz 5 MHz

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65 The sound is refracted due to differences in sound velocity in the 2 materials

66 C Perspex Steel C

67 C Perspex Steel C

68 C Perspex Steel C 20 S

69 C 27.4 S 33 C Compression wave refracted at 90 degrees

70 C S (Surface Wave) 90 C Shear wave refracted at 90 degrees 57 Shear wave becomes a surface wave

71 1st Critical Angle Calculation C Perspex Steel C S 27.2

72 C Perspex Steel C S nd Critical Angle Calculation

73 Sound will be either transmitted across or reflected back Reflected Transmitted Interfac e How much is reflected and transmitted depends upon the relative acoustic impedance of the 2 materials

74 Definition The Resistance to the passage of sound within a material Formula Measured in kg / m 2 x sec Steel46.7 x 10 6 Water1.48 x 10 6 Air x 10 6 Perspex3.2 x 10 6 = Density, V = Velocity

75 % Sound Reflected + % Sound Transmitted = 100% Therefore % Sound Transmitted = 100% - % Sound Reflected

76 Z 1 (Steel) = 46.7 x 10 6 Z 2 (Water) =1.48 x 10 6 reflected%

77 How much sound transmitted? 100 % - the reflected sound Example : Steel to water 100 % - 88 % ( REFLECTED) = 12 % TRANSMITTED The BIGGER the Acoustic Impedance Ratio or Difference between the two materials: More sound REFLECTED than transmitted.

78 Steel Air Steel Air Steel Aluminum Steel Large Acoustic Impedance Ratio No Acoustic Impedance Difference Small Acoustic Impedance Difference

79 Similarly: At an Steel - Air interface 99.96% of the incident sound is reflected At a Steel - Perspex interface 75.99% of the incident sound is reflected

80 2 signals at 20% and 40% FSH. What is the difference between them in dBs?

81 2 signals at 10% and 100% FSH. What is the difference between them in dBs?

82 2 : 1=6bB 4 : 1=12dB 5 : 1=14dB 10 : 1=20dB 100 : 1=40dB

83 There are four main sizing techniques used with 0 o probes: 6 dB drop Maximum Amplitude Equalisation DGS

84 6 dB Drop For sizing large planar reflectors only Signal / echo reduced to half the height Example: 100% to 50% 80% to 40% 70% to 35% 20% to 10% Centre of probe marked representing the edge of defect.

85 BWEDefect The back wall echo reduced as some part of the beam now striking the defect The echo of the defect has NOT yet maximise as the whole beam Not yet striking the defect Plan View

86 Now the whole beam is on the defect Defect Back wall echo is now may be reduced or disappeared

87 BWEDefect Plan View The probe is moved back until the echo is reduced by half of its original height At this point the probe centre beam is directly on the edge of the defect The probe is then removed and the centre is marked, and repeat to size the whole defect

88 Maximum Amplitude Technique For sizing multifaceted defect – eg. crack Not very accurate Small probe movement

89 The whole probe beam is on the defect At this point, multipoint of the defect reflect the sound to the probe The echo (signal) show as a few peaks Multifaceted defect : crack

90 The probe is moved out of the defect, the signal disappeared If the edge of the beam strike the edge of the defect, a very small echo appears If the probe is moved into the defect, the signals height increase At this point the MAIN BEAM is directly at the edge of the defect One of the peak maximised

91 The probe is to be moved to the other end of the defect The signals will flactuate as the beam hits the different faces of the defects The probe is moved back into the defect and to observe a peak of the signal maximises Mark the point under the centre of the probe which indicates the edge of the defect The length of the defect is measured Length Remember: The peak which maximised does not have to be the tallest or the first one

92 At this point the whole beam is on the back wall BWE At this point the whole beam is on the defect The BWE is at it maximum The Defect echo is at it maximum Defect At the edge of the defect, half of the beam is on the defect, and another half is on the back wall The defect echo is at equal height as the back wall The point is marked as the edge of defect The equalization technique can ONLY be used if the defect is halfway the thickness

93 A scan The CRT (Cathode Ray Tube) display The Horizontal axis : Represents time base / beam path length / distance / depth The Vertical axis : Represent the amount of sound energy returned to the crystal

94 B scan The End View Display B

95 C scan The Plan View Display C

96 D scan The Side View Display D

97 Pulse Echo Through Transmission Transmission with Reflection (pulse echo techniques where the transmitter is separate from the receiver - e.g. tandem testing, time of flight)

98 Single probe sends and receives sound Gives an indication of defect depth and dimensions

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103 No indication from defect A (wrong orientation) A B B

104 Transmitting and receiving probes on opposite sides of the specimen Pulsed or Continuous sound Presence of defect indicated by reduction in transmission signal No indication of defect location Easily automated Commonly integrated into plate rolling mills - lamination testing

105 Transmitting and receiving probes on opposite sides of the specimen Tx Rx Presence of defect indicated by reduction in transmission signal No indication of defect location

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107 R T Also known as: Tandem Technique or Pitch and Catch Technique

108 TR TANDEM TESTING

109 Probe held a fixed distance above the surface (1 or 2mm) Couplant is fed into the gap

110 Component is placed in a water filled tank Item is scanned with a probe at a fixed distance above the surface

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112 Water path distance Front surfaceBack surface Defect

113 PULSE ECHO

114 ULTRASONIC EXAMINATION OF WELDS DOUBLE SIDED T JOINT BACK GOUGE

115 ULTRASONIC EXAMINATION OF WELDS (appro x.) COVERAGE OF FUSION FACES COVERAGE OF WELD VOLUME

116 45 0 COVERAGE OF FUSION FACES COVERAGE OF WELD VOLUME ULTRASONIC EXAMINATION OF WELDS

117 SCANNING FOR TRANSVERSE IMPERFECTIONS 45 0

118 SCANNING FOR TRANSVERSE IMPERFECTIONS

119 THREADLIKE DEFECTS, POINT DEFECTS AND FLAT PLANAR DEFECTS ORIENTATED NEAR- NORMAL TO THE BEAM AXIS ALL PRODUCE AN ECHO RESPONSE WHICH HAS A SINGLE PEAK:

120 THESE DEFECTS CAN BE DIFFERENTIATED BETWEEN BY OBSERVING THE ECHO DYNAMIC BEHAVIOUR IN LENGTH AND DEPTH SCANS: POINT THREADLIKE PLANAR (NEAR NORMAL INCIDENCE) DEPTH SCAN LENGTH SCAN NOTE: THE RESPONSE FROM A PLANAR DEFECT WILL BE STRONGLY AFFECTED BY PROBE ANGLE WHILE THAT FROM A THREADLIKE REFLECTOR WILL REMAIN ALMOST UNCHANGED IF A DIFFERENT PROBE ANGLE IS USED.

121 THE ECHO RESPONSE FROM A LARGE SLAG INCLUSION OR A ROUGH CRACK IS LIKELY TO HAVE MULTIPLE PEAKS:

122 SOMETIMES IT WILL BE POSSIBLE TO DIFFERENTIATE BETWEEN THESE 2 DEFECTS SIMPLY BY PLOTTING THEIR POSITION WITHIN THE WELD ZONE: A. PROBABLE SLAG, POSSIBLE CENTRELINE CRACK B. PROBABLE HAZ CRACK

123 IN CASE A IT WILL BE DIFFICULT TO DETERMINE WHETHER THE DEFECT IS SLAG OR A CRACK. ROTATIONAL OR ORBITAL PROBE MOVEMENTS MAY HELP: ORBITALROTATIONAL

124 CRACK SLAG ORBITA L SCAN ROTATIONA L SCAN TYPICAL ECHO DYNAMIC PATTERNS

125 Calibration Blocks and Their Usage I.I.W (International Institute of Welding) Block / V1 / A2 Block 100mm 300mm 91mm 85mm 200mm 50mm Dia Perspex 5mm 10mm 15mm 35mm1.5mm Dia 15mm 100mm 23mm 25mm USE S Compressi onal Shear

126 A4 / V2 / DIN 54/122 / KIDNEY BLOCK R50 R mm or 20mm PLAN VIEW 1.5 OR 5mm dia. hole USES i.Calibration This block can be purchased having a thickness of either 12.5mm or 20mm. b)Shear Probes a) Compressional Probes i.Calibration When aiming at 25mm radius, signals occur at 25, 100, 175, 250, etc. When aiming at 50mm radius, signals occur at 50, 125, 200, 275, etc. ii.Index Point Aiming at 25mm or 50mm radius, maximise signal and mark index. iii.Probe Angle By maximising echo from either 1.5mm or 5mm diameter hole and reading off engraved on side of test block.

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