Contact Laser Ultrasonic Evaluation (CLUE) of Aerospace Materials and Parts

Transcription

1 More International Laser Center of M.V. Lomonosov Moscow State University LASER OPTOACOUSTIC LABORATORY Contact Laser Ultrasonic Evaluation (CLUE) of Aerospace Materials and Parts Authors: Alexander A. Karabutov International Laser Center of M.V. Lomonosov Moscow State University /11/2013

2 Team Alexander Karabutov (jr.) Dmitry Ksenofontov Igor Kudinov Elena Savateeva Varvara Simonova Sergey Solomatin Alexey Zharinov scientist scientist engineer senior scientist senior scientist engineer engineer 2

3 OUTLINE - Basics of CLUE - CLUE systems - Resolution and sensitivity of CLUE - CLUE of CFRC and structures - CLUE of heat-exchange parts - Measurement of local mechanical modulii - CLUE of residual stress - CLUE of surface profile and density 3

4 BASICS of CLUE 4

5 Basics of CLUE DPSS Q-switched laser pulse is delivered with optical fiber to laser-ultrasonic transducer and is absorbed in optoacoustic generator. Exited wideband probe ultrasonic pulse propagates to investigated sample. Probe pulse is scattered at the sample inner structures. Wideband piezotransducer detects backscattered ultrasound waves. Backscattered signals deliver the information about the sample, namely, on the acoustic properties of different inner structures of the sample. 5

6 Comparison of Piezo and Laser UT 1 0, s 0.58 s 0-0,5-1 z piezo >(6-7) z CLUE Laser UT Piezo UT 0 0,5 1 1,5 2 2,5 3 3,5 4 Time, s In-depth resolution of UT is determined by probe pulse duration. CLUE pulse duration is 6-7 times shorter then that for conventional UT at the same central frequency. 6

7 Advantages of CLUE Short duration of a probe ultrasonic pulse enhanced in-depth resolution for limited frequency band Smooth temporal shape of a probe ultrasonic pulse no dead-zone, discrimination of soft and rigid impurities Small diameter of a probe ultrasonic beam enhanced sensitivity of small defect detection Smooth phase front of an ultrasonic beam no dead zone, no side lobs 7

8 CLUE SYSTEMS 8

9 Contact Laser-Ultrasonic Defectoscope Specific features Short ultrasonic pulses are excited in a course of laser pulse absorption in a Laser-Ultrasonic transducer. Back-scattered ultrasonic signals are detected with ultra wide-band piezo-receiver. It makes it possible to enhance spatial resolution of testing and to reduce dead-zone. Probe ultrasonic pulse 1 Spectral sensitivity of detection Amplitude, rel. un Sensitivity, rel. un. 0,8 0,6 0,4 0,2 4,2 4,4 4,6 4,8 5 5,2 5,4 я ( ) Time, s Ч ( ц) Frequency, MHz Contact Laser-Ultrasonic Defectoscope UDL-2M consists of opto-electronic unit with DPSS laser and ADC, laser-ultrasonic transducer connecting to the former with fiber optical and electric cables, and PC on line with the unit to process, monitor and storage measurement results. 9

10 Automation of measurements Transducer traverse range Positional accuracy Transducer Defectoscope Frequency range (1/2 level) 300 mm 30 m PLU-6P-02/01 UDL-2M 0,1-6 MHz 1-D and 2-D automated scanning systems for industrial applications provides enhanced sensitivity and resolution. 10

11 5-D Automated CLUE 5-D scanning system keeps constant ultrasonic beam velocity across the surface, the distance from the transducer to the object surface and transducer axis normal to the surface of the object. 11

12 RESOLUTION and SENSITIVITY of CLUE 12

13 Scan of CFRC across the surface Front surface Front surface 1,4 mm Brass foil 19 mm Brass foil Plies of composite Rear surface Laser-Ultrasonic Transducer PLU-6P-01 has frequency band MHz and provides in-depth resolution of 0.1 mm. Bright lines are image of carbon plies, black lines show matrix content. Bright line at a depth of 1.4 mm is a reflection from brass foil imposed between 10-th and 11-th plies. 13

14 CLUE of delaminations in CFRC Front surface 10 ply CFRC with delaminations Plies Matrix Delaminations Rear surface High in-depth resolution of CLUE makes it possible to distinguish delamination between each layer of 10 ply CFRC. The delaminations manifest between the bright lines in a black, according to high negative reflection of ultrasonic wave. The transducer PLU-6P-01 is explored. 14

15 Detection of scatter 0,06 0, Depth, mm 3.57 mm Aluminum Sample 0,02 Drill 1 mm 0-0,02-0,04 1 mm Rear Surface -0, , , ,5 21 Time, s The ultrasonic trace of PLU-6P-01 shows the scattered signal from cone drill at rear surface of 50 mm thick slab. It demonstrates high sensitivity of CLUE 15

16 CLUE of CFRC and structures 16

17 CLUE of honeycomb structure Surface of coating Detection of delamination in a coating of a honeycomb structure. Interface between coating and honeycombs Honeycomb structure Delamination in a coating at a depth of 1.0 mm Reverberation inside delaminated layer 17

18 CLUE of honeycomb structure Disbonding of coating from honeycomb structure Multiple reflections in a coating disbonded 18

19 CLUE of the honeycomb bonding quality Cell size 4 mm Image of a rear surface of CFRC cover in a honeycomb structure Regular region Disbonding Wicking 19

20 Laser ultrasonic image of adhesive layer of the honeycomb structure profile Rear surface of filler in honeycomb structure, mm 20

21 CLUE of Impact Test of CFRC Front surface of CFRC Impact E=30 J Lateral position, mm 6 mm Rear surface of CFRC Texture failure Impact damage 21

22 CLUE of impact test Thickness of CFRC 6 mm Applied energy - 30 J Damage spreads along fibers in each layer 22

23 CLUE of stringers part Scheme of part Part surface (1) Rear surface of cover (2) T-connection filling (5) Stiffener (3) Rear surface of part (4) Fiber layers (6) Laser-ultrasonic image Part surface (1) Stiffener (3) Rear surface of cover (2) Rear surface of part (4) T-connection filling (5) 23

24 CLUE of T-bond Scheme of part Failure of T-connection filling Delamination of T-connection 50 mm Stiffener Stiffener 6 mm Stiffener Laser-ultrasonic image Stiffener Stiffener 24

25 CLUE of impact test Impact test damage before loading Impact test damage after loading 40 mm 3 mm 9 mm 70 mm After loading damage area becomes 2 times wider and 3 times deeper 25

26 CLUE of CFRC POROSITY 26

27 CT of CFRC CT of porosity of CFRC Resolution 40 Porosity = 10.4% Distribution of pores 27

28 CLUE of CFRC porosity X, mm Z, mm Porosity = 10.4% Y, mm X, mm Z Z, mm Zones of pores concentration Z, mm CLUE provides an image of texture and porosity distribution 28

29 CT of CFRC Z X Color image of pores of different size. Sample103. Porosity=3.3% X Resolution 20 µm Image area - 20Х20 mm Pores are concentrated in cross-sections of plies Y Conglomerate of pores 29

30 Distribution of pores vs. size, CT По и о ь, % Porosity, % 3,4 3,2 3,0 2,8 2,6 2,4 2,2 2,0 1,8 1,6 1,4 1,2 1,0 0,8 0,6 0,4 0,2 0, sample 105 Áîëåå >120 µm 120 ìêì (80-120) ìêì µm (40-80) ìêì µm (20-40) ìêì µm Conglomerates of pores with the effective diameter greater, then 120 µm make a contribution about 50% to total porosity 30

31 Spatial distribution of pores, CLUE Distribution of pores with the effective diameter >120 µm Depth, mm Y, mm X, mm CLUE provides the investigation of 3-D distribution of pores with one side access to a part 31

32 CLUE of HEAT-EXCHANGE PARTS 32

33 No side lobs, narrow ulttrasonic beam Disbonding in ribs panel 0.8 mm Scheme of ribs panel 1.5 mm Reverberations in cover plate B-scan of CLUE transducer across the ribs Disbonding Laser-ultrasonic beam has no side lobs, that provides clear image of ribs failure 33

34 CLUE of Ni superalloy bucket Zones of scanning A B Model defects Test sample has model defects several mm long in a rib B. Rib A has no defects. Two grains are evidently seen. 34

35 CLUE control of rib without a defect Scan zone across the rib A Sample surface PLU transducer A US-beam Rib A, 2 mm Bottom of plate 35

36 CLUE of model crack Scan zone across rib B Sample surface B Rib B, 2 mm US-beam Bottom of plate Defect at the depth of ~0.5 mm below the plate 36

37 MEASUREMENT of LOCAL MACHANICAL MODULII 37

38 Ultrasonic wave velocity measurement Amplitude of signals, Volts t t 0.4 Time-delay between echo signals can be measured with high precision. Scatter is less then 0.1% for thickness of a sample greater then 2 mm. 0.2 t = 2h/c , m s 38

39 Multiple reflections of CLUE pulses Probe pulse Ultrasonic trace Time H/C S +H/C L 2H/C L 2H/C L OA-Generator L L L L S Sample Measuring a time delay between the pulses 1,2,3 one can determine the velocity of longitudinal and shear wave. The thickness of a sample is known. 39

40 Laser-ultrasonic measurement of elastic modulus Longitudinal wave Longitudinal wave Shear wave Ratio of longitudinal and shear wave velocity provides the value of Poisson ratio. To determine mechanical modulii one needs to know thickness of a sample and it s density. Accuracy ~2%. 40

41 Pitch and Catch laser-ultrasonic transducer А- OA Generator Longitudinal УЗ- Wave У - UT Detector Range 30 mm Beam width.2-3 mm Accuracy of ultrasonic velocity measurement..1% Frequency band MHz 0,15 0,1 Fused Silica е я е ц CLUE Signal 0,05 0-0,05-0,1 Longitudinal Wave -0,15-0, Time, µs В е я, 41

42 CLUE of elastic modulus Measurement of elastic modulus along the fibers of CFRC with pitch and catch transducer E, GPa 42

43 Longitudinal Wave velocity Velocity, km/s 6 5,5 5 Along and across Z-direction,, я,, я 4,5 4 Ш 1 Ш 2 Ш 3 Ш 4 Ш 5 S1 S2 S3 S4 S5 Failure in a panel of T-connection 43

44 Longitudinal wave velocity in porous medium 1 0,95 0,9 0,85 0,8 Measurement of local ultrasonic wave velocity with high precision gives an estimation of local porosity c 2 l c 2 l 0 1 P 2/ 3 1 c cl This model is valid for spherical pores with the porosity P<20% P l ,001 0,01 0,1 Porosity 44

45 CLUE of RESIDUAL STRESS 45

46 acoustic velocity distribution in homogeneous aluminum sample y Width z x 6,28 Base 2,84 6,275 2,835 6,27 2,83 6,265 2,825 6,26 CLZ, mm/us CRX, mm/us ,82 X, mm Distribution of longitudinal wave velocity and surface wave velocity shows high homogeneity of tested sample 47

47 Residual stresses in the locally hardened aluminum alloy sample y Width z x 6,26 Base 2,86 6,255 2,855 6,25 2,85 6,245 2,845 6,24 2,84 6,235 6,23 2,835 C, mm/ s LZ C, mm/ s RX 2, X, mm Laser treated area is evidently manifested in distribution of longitudinal and surface wave velocity due to residual stress. Acousto-elastic effect has different coefficient for longitudinal and surface wave. 48

48 CLUE of SURFACE PROFILE and DENSITY 49

49 CLUE of composite surface profile height of a surface, Z, mm Z-resolution - 7 µm Lateral resolution 0.5 mm Y, mm Z, mm X, mm Y, mm X, mm Arrival time of acoustic pulse reflected at the surface of a sample provides the profile of the surface. Focused laser-ultrasonic transducer PLU-6F-02 is explored. 50

50 Measurement of local density of composite with CLUE Density, g/cm 3 Y, mm Density, g/cm 3 X, mm X, mm Y, mm Coefficient of acoustic pulse reflection provides the information on the local density of a sample 51

51 Conclusion CLUE is an effective tool of non-destructive testing of materials and parts for aerospace industry. A chain of laser-ultrasonic transducers of different schemes and beam characteristics is explored in wide variety of application with the same laser-electronic unit. Laser-ultrasonic transducer operates both in a single and multychannel system. 52