Finite Element Model based Optimization of Pulsed Eddy Current Excitation Rise Time

Transcription

1 Finite Eleent Model based Optiization of Pulsed Eddy Current Excitation Rise Tie N. N. Bharadwaj, V. Arjun, B. Purnachandra Rao Indira Gandhi Centre for Atoic Research, Kalpakka, India

2 Eddy Current Testing Sinusoidal excitation Single frequency content Liited depth of investigation For deep penetration High excitation current Low frequency Excitation coil Eddy current Priary agnetic field Eddy current field J x = J 0 e x/δ Jx - eddy current density at depth x J 0 - eddy current density at surface δ - skin depth = 1/(πμσf) 1/2 Conductive specien Pulsed excitation Rich in frequency content Wide depth of investigation short duration high aplitude Reduced heating

3 Optiisation of pulsed eddy current probe for detection of sub-surface defects in stainless steel plates V. Arjun, B. Sasi, B. Purna Chandra Rao, C.K. Mukhopadhyay, T. Jayakuar Current (A) Highlights For effective detection of deeper defects, probe design plays a ajor role. FEM based approach for optiizing probe configuration and diensions. Send-receive type ferrite cored probe of 19 outer diaeter shows better detection sensitivity. Experiental study also confirs its detection sensitivity for sub-surface defects. For defect detection, Excitation characteristics of the probe also play a crucial role. Rise tie Pulse aplitude Pulse width Tie (s)

4 Current (A) Objective I: FEM of PEC Optiization of rise tie for enhanceent in detection of defects in a SS plate of 5,8,10 and 12 thickness. II: Analysis using Frequency spectru. III: Study of different conductivity speciens. Rise tie Specien thickness Defect depth below surface Pulse aplitude Pulse width Tie (s) Defect detection Exciter Signal

5 Modelling Study Geoetry Height() Width() Ferrite-1 Receiver Ferrite-2 Ferrite Receiver 10 3 Ferrite Exciter DEFECT Exciter 15 3 Specien Variable(5,8,10,12) 50 PROBE Defect Variable(1-11) 5 Lift-off Material μ r ε r Ferrite Copper 1 1 6e7 Stainless steel e6 SPECIMEN Air h

6 Typical Model Nuber of eshes: Axi syetry Magnetic insulation COMSOL Software Magnetic Field doain Transient tie solving tool Maxwell s Equation: 2 A A t V J s

7 Current (A) Induced Voltage (V) Siulation Results Exciter signal Receiver signal Rise tie Pulse aplitude Peak aplitude Pulse width Tie to peak Tie (s) Tie (s)

8 Induced Voltage,V d e f e c t f r e e h h h h h h 3.5x x x x x x x x E E E tie,s A defectfree Detection Paraeters 1. Peak aplitude(pa) 2. Tie to peak(ttp) Paraeter to be optiised Rise tie Receiver Signal Exciter Signal As defect depth increases, peak aplitude decreases, tie to peak increases and the difference (in pa & ttp) between successive defects also decreases. So, the effect of rise tie on the difference(in pa & ttp) is studied for enhanced defect detection.

9 Rise Tie Study SS plate (2.23 % IACS) In this study, pulse aplitude is fixed at 0.5 A. Pulse width is fixed at 150 % of rise tie. Rise tie is varied to exaine the sensitivity paraeters. Rise ties considered: 5 plate: 100 μs, 200 μs, 400 μs, 800 μs, 900 μs. 8 plate: 200 μs, 400 μs, 800 μs, 900 μs, 1000 μs. 10 plate: 800 μs, 900 μs, 1000 μs, 1200 μs, 1500 μs. 12 plate: 1250 μs, 1500 μs, 1750 μs, 2000 μs, 2250 μs.

10 Peak aplitude,v tie to peak,s 5 thick plate Peak aplitude and tie to peak variation with defect depth at different rise ties 2.2x x x x x x x x x x x x x x x x defectfree depth below surface, defectfree depth below surface, Peak aplitude reduces with increase in rise tie. Tie to peak increases with increase in rise tie.

11 Difference,V Difference,s Difference variation with rise tie (Defect at 4 and defect-free plate) 4.0x x x x10-7 defect=4 & defectfree 4 1.0x x x x x x x x x x x10-7 defect=4 & defectfree risetie,s Defect-free risetie,s Good difference is obtained in peak aplitude and tie to peak at rise tie of 400 μs.

12 Difference,V Difference,s 8 thick plate Difference variation with rise tie (Defect at 7 and defect-free plate) 4.0x x x x x x x x defect=7 & defectfree 7 4.0x x x x defect=7 & defectfree risetie,s Defect-free rise tie,s Good difference is obtained in peak aplitude and tie to peak at rise tie of 800 μs.

13 Difference,V Difference,s 10 thick plate Difference variation with rise tie (Defect at 9 and defect-free plate) 3.0x x x x10-10 defect=9 & defectfree 9 1.8x x x x x x10-7 defect=9 & defectfree 5.0x x10-7 Defect-free risetie,s risetie,s Good difference is obtained in peak aplitude and tie to peak at rise tie of 1200 μs.

14 Difference,V Difference,s 12 thick plate Difference variation with rise tie (Defect at 11 and defect-free plate) 2.0x x x x x10-11 defect=11 & defectfree x x10-8 defect=11 & defectfree 1.2x x x x10-8 risetie,s Defect-free risetie,s Good difference is obtained in peak aplitude and tie to peak at rise tie of 2000 μs.

15 Optiised risetie, s Optiised Risetie variation with specien thickness Specien thickness, As specien thickness increases, optiised risetie also increases.

16 Fax,Hz Eax,J Tax, s Tie Frequency Analysis Rise tie(µs) Fax(Hz) Eax(J) Tax(µs) Used to find doinant frequency, tie of occurrence of doinant frequency and its energy e e e Fax 2.6x x x10-4 Eax Tax e e Rise tie(µs) Fax(Hz) Eax(J) Tax(µs) e e-4 ` e rise tie, s 2.0x x x x x x rise tie, s rise tie, s Energ y e e Rise tie(µs) Fax(Hz) Eax(J) Tax(µs) e e e e e µs 800 µs 1200 µs 12:-2000 µs hz,2.4002e- 4J,.0011s.

17 Correlation of rise tie with specien thickness Thickness Rise tie Doinant frequency Skin depth 1/(πμσf) 1/ µs Hz *thickness µs 673 Hz *thickness µs Hz *thickness µs 279 Hz *thickness For any specien thickness, the optiised rise tie has doinant frequency that has skin depth at twice the specien thickness.

18 Difference,s Difference,s Difference,s Hastelloy Plate (1.5 % IACS) Difference variation with rise tie x x x x x x x10-7 defect=4 & defectfree 1.8x10-7 defect=7 & defectfree 1.0x10-7 defect=9 & defectfree 4.5x x x x x x10-8 risetie,s risetie,s risetie,s Optiu rise ties obtained are 200 µs, 500 µs and 1000 µs for 5, 8 and 10 plates respectively.

19 Difference,s Difference,s Difference,s Aluiniu plate (30 % IACS) Difference variation with rise tie x x x x x x x10-5 defect=4 & defectfree 3.6x x10-6 defect=7 & defectfree 1.8x x10-6 defect=9 & defectfree 1.1x x x x x x risetie,s risetie,s risetie,s Optiu rise ties obtained are 7 s, 10 s and 13 s for 5, 8 and 10 plates respectively.

20 Epirical Relation Optiu rise tie = p 00 + p 10 * T + p 01 * C + p 20 * T 2 +p 11 *T*C + p 02 *C 2 (T Thickness; C Conductivity) p 00 = ; p 10 = 202.3; p 01 = 29.47; p 20 = ; p 11 = 37.44; p 02 = Specien Conductivity(% IACS) Hastelloy 1.5 Stainless Steel 2.23 Aluiniu 30 Thickness () Actual Rise tie (µs) Epirical Rise tie(µs) Error(%)

21 Suary Pulsed eddy current rise tie has been optiized for enhanced sub-surface defect detection in SS plate, Hastelloy plate and Aluiniu plate of thickness 5, 8, 10 and 12. An epirical relation is given for optiu pulse rise tie as a function of specien thickness and conductivity. Further, tie-frequency analysis of the excitation signals revealed that the optiized rise tie has doinant frequency that has skin depth at twice the specien thickness.

22 THANKYOU