Development of Induction Thermography

Transcription

1 Development of Induction Thermography Marc Genest, Gang Li 16 June, 2015, NDT in Canada 2015 NRC Aerospace Structures, Materials and Manufacturing Laboratory

2 Induction Thermography Outline Setup Results Outline Challenges Conclusions

3 Induction Thermography Method for the detection of flaws in electrically conductive materials Coil excited with an alternating current of high frequency, create alternating magnetic field If a conductive part is located within the magnetic field, an electric current will be induced in that part Image Source:

4 Induction Thermography Current lines are directed around disturbances, such as cracks Joules Heating: heat produced by electrical current passed through a conductor Additional heat is produced within magnetic parts through hysteresis the alternating magnetic flux field causes the magnetic dipoles of the material to oscillate as the magnetic poles change their polar orientation every cycle Current redirection around cracks leads to increased current density at crack tips and decreased current density at its flank Resulting local temperature change can be made visible with an appropriate thermographic camera Thermal Image Schematic of current disturbance caused by a flaw

5 Induction Thermography - Setup Induction coil IR Camera Test Object X: 290 Y: 310 Index: RGB: 0.625, 0, t emperat ure (C) time (s)

6 Experimental results Heat Generation Aluminum 200A Before heating Early heating After 4s induction heating 8s after induction off 27.7 Max: C Min: C Avr: C Point Trend - A T e m p e ra tu re C Frame Index 6

7 Experimental results Heat Generation Aluminum 200A Coil Orientation Before heating After 4s induction heating Before heating After 4s induction heating 7

8 Example of Results Aluminum, 100A, Heating time 10s Temperature Increase (C) Distance Temperature (mm) Increase (C) Aluminum, 400A, Heating time 10s Aluminum, 400A, Heating time 10s Distance (mm) Temperature Increase (C) Datenreihen Expon. (Datenreihen1) Distance (mm) 8

9 Experimental Results Composite, 150A, 10mm Heat Generation CFRP reached over 130 C, in 14s In comparison with same settings Aluminum plate increase by only 2 C 9

10 Modelling Heat Generation 2D Heat transfer in the aluminum alloy panel was created by electromagnetic field Good agreement between experimental & FE results Mesh influence is limited 43 Panel point temperature ( o C) Experimental 2D FE_Mesh1 2D FE_Mesh2 Jump in temperature due to IR camera autocalibration Induction heating time (s) 10 G. Li, M. Genest, Tw o-dimensional Finite Element Simulation of Induction Heating of An Aluminum Alloy Panel, 23 rd CASI Aerospace Structures & Materials Symposium, CASI

11 Parametric Study 2D Temperature inversely proportional to Loop spacing More uniform temperature field created by larger loop spacing Temperature inversely proportional to the distance High distance (here: >10 mm) should be avoided for a practical application 45 Panel point temperature ( o C) Lsp=1.6mm_dist=2mm Lsp=3.18mm_dist=2mm Lsp=4.8mm_dist=2mm Lsp=6.4mm_dist=2mm Lsp=11.1mm_dist=2mm Lsp=12.7mm_dist=2mm Lsp=15.9mm_dist=2mm Lsp=20.6mm_dist=2mm Panel point temperature ( o C) dist =2mm dist=5mm dist=10mm dist=15mm dist=20mm Induction heating time (second) Induction heating time (second) 11 G. Li, M. Genest, Tw o-dimensional Finite Element Simulation of Induction Heating of An Aluminum Alloy Panel, 23 rd CASI Aerospace Structures & Materials Symposium, CASI

12 Effect of distance between coil and Al alloy A, 5mm A, 10mm G. Li, M. Genest, Tw o-dimensional Finite Element Simulation of Induction Heating of An Aluminum Alloy Panel, 23 rd CASI Aerospace Structures & Materials Symposium, CASI

13 Numerical Assessment & NDE Application A fast and efficient way: each 2D job took approximately 10 minutes in a laptop More sophisticated setup, skills, and significant time needed in a 3D analysis for flaw detection Given an electric source, adjustment in the coil loop spacing, coil position, loop number, and panel size will affect the generated temperature profile in the test pieces. For instance, the coil distance should be less than 20 mm, and the heating improvement is notable using a coil from 1- to 3-turn within a loop spacing range 13 G. Li, M. Genest, Tw o-dimensional Finite Element Simulation of Induction Heating of An Aluminum Alloy Panel, 23 rd CASI Aerospace Structures & Materials Symposium, CASI

14 Honeycomb - Structure Two thin but stiff skins bonded to a lightweight but thick core. Overall sandwich composite high bending stiffness with low density. High strength/weight ratios Flaws Disbond Crushed core Dent Delamination (Composite Skin) Cracks (Metallic Skin) 14

15 Setup Setup Video 15

16 Crack in aluminum skin Setup Bare metal Cover with electrical tape 22 Video Rectangular Coil Video 6-Inch Diameter Coil 16

17 Disbond in aluminum skin Simulated disbond Not detected in infrared images 17

18 Carbon Fiber Skin Al Honeycomb Core 18

19 Disbond Between Carbon Skin and Aluminum Core Ultrasounds Pulsed Thermography Induction Thermography Carbon fiber Al honeycomb Video 6-Inch Diameter Coil 19

20 Engine Disk Normal lens Close up lens Setup 130A 20 Close up lens Side 2

21 Engine - Spacer Liquid Penetrant Induction Thermography Setup 21

22 Engine - Spacer location #2 (bore 0.104, flange ). - 40A Distance along profile location #5 (bore 0.085, flange ) A Distance along profile 22

23 Engine Turbine Blade 65 Setup 130A Temperature ( C) Temperature Time Time (s) 23

24 Engine Turbine Blade IR Images of engine blade # Engine blade IR Images of engine blade #

25 Inspection of Complex Shape IR Image obtained during induction thermography corner crack Nozzle Guided Vane IR Image obtained during induction thermography middle crack IR Video obtained during induction thermography (200ms excitation) 25

26 Aluminum Crack fatigue crack Not detected! Modelling help better understand? A planar crack through the panel thickness 26

27 Aluminum 6061 Crack Model Crack width 0.02mm Crack width 0.05mm 27

28 Challenges Images analysis, to represent in a single image if multiple flaw instead of movie Getting proper induction heating at flaw location Coil shape, frequency Hot spot real flaw or part internal features Crack width, and depth 28 Example of different coils IR Images - internal feature or flaw?

29 Conclusions Induction thermography can be used to detect cracks, disbond, impact damage, delamination Still several questions unanswered Modelling is needed to better understand the capabilities and limitations Need to understand the part being inspected and internal structures. 29

30 Thank you Marc Genest Research Officer Tel: (613)