Practical Ultrasonic Phased Array High Temperature Technique Development

Robert Ginzel 1, Mohammad H. Marvasti 2 and

Anthony N. Sinclair 2

1 Eclipse Scientific2 Department of Mechanical and Industrial

Engineering, University of Toronto

Introduction

Enhanced failure mechanisms

� Economic damages

� Life loss

Regular non-destructive testing (NDT) is required

� On-line inspection

� Phased array ultrasound

Industrial systems operating at high temperatures

� Power plants

� Petrochemical plants

Phased Array Inspection – Scan Plan

Plastic wedgePA probe

Weld section

Test pieceUltrasonic

waves

� Select wedge-array system

� Select optimum beam angles

� Ensure full coverage

� Ray tracing software

� Focal law (elements delay times)

� Plane waves and focused beam

High Temperature Inspection Challenges

1. Operation (Assembly)

2. Beam formation inaccuracy

� Wedge (high temp resistant material)

� Protecting the array (local cooling )

� Velocity/Angle changes

� Beam skew

Significant thermal gradient

inside the wedge

Cooling

Jacket

5L64-A12

Array

High Temperature

Wedge

� Non valid focal laws

Temperature Distribution Model (FEM)

Boundary conditions (steady state)

1. Temperature (piece surface)

2,3,4. Convective cooling

Natural convection ( surrounding Air)

5. Temperature (cooling jacket effect)1

5

3

2

4

Temperature-Velocity Changes

@ 5MHZ

Beam Skew Modeling

Ray Theory Tracking a Single Point on the Wave Front

V(x,y): local wave speed

φ: local angle with respect to x-axis

Focal Law Calculation Algorithm-Plane Wave

Element time delays

� Calculate the relative time delays for

excitation of each element

� Use a few sample points on the wave front

for calculations

� Obtain the wave paths, calculate the length of

the paths and use sound velocity in the block

and the wedge

� Interpolate the travel times along the array-

line points to obtain travel times associated

with each element

� Calculate travel time of the waves emitted

from each element to the wave front

Model Results

� Non-linear time delay Pattern

for HT inspection

� Incorrect time delays on array

elements of up to 100 ns

WA12-HT55S-IH-G

5L64-A12

� Phase error of up to 50% of the

wave period

� destructive interference, significant

distortion of the desired beam profile,

and poor imaging resolution.

� φs=60o , Using elements

1-16 of the array

� Pulse central frequency of 5 MHz

(period of 200 ns)

100 ns

Algorithm Validation-Experimental Concept

Transmission

Delays

Reception

Delays=

Φs

Algorithm Validation – Experiment Set Up

Hot Plate

WA12-HT55S-IH-G5L64-A12

InsulationAngled

block

Focus LT and Tomoview

� Enter calculated delays

manually for each element

(transmission)

� Collect the received signal by

each element (reception)

� Comparing the reception

and transmission delays

Algorithm Validation – Experimental Results

� Results of 15 repeated

experiments

� Random errors of up to

±13 ns

� Bias errors of up to 10 ns

WA12-HT55S-IH-G

5L64-A12

� φs=60o , using elements

1-16 of the array

� Received delays on

elements 8 and 16� Our experimental results and theoretical

results agree within the expected error

limits

� Pulse central frequency of

5 MHz (period of 200 ns)

Focal Law Calculation Algorithm-Focused Beam

Element Time Delays

� Calculate the relative time delays for

excitation of each element

� Use a few sample points on the wedge-piece

interface for calculations

� Obtain the wave paths, calculate the length

of the paths and use sound velocity in the

block and the wedge

� Interpolate the travel times along the array-

line points to obtain travel times associated

with each element

� Calculate travel time of the waves emitted

from each element to the focal point

Model Results

WA12-HT55S-IH-G

5L64-A12Elements 1-16

180 ns

174 ns

147 ns

Algorithm Validation-Experimental Concept

� Sweep focused beam

(40o-70o in 1o increments)

� Using elements 1-16

Algorithm Validation – Experimental Results

� Four holes are resolved

(Local amplitude peaks)

� Amplitude peaks at 44o, 49o, 56o

and 66o refraction angles

� Application of conventional delays at

150oC led to non-optimal focusing

� Correct high temperature delays led

to peak shifts toward the expected

locations

ConclusionConclusion

Future WorksFuture Works

3. Implement the new algorithm in automated scanning system

1. Test up to 350oC

2. Develop standards for high temperature inspections

� Application of conventional array

focal law at elevated temperaturesIncorrect time delays,

distortion of the beam profile

Elevated Temperature Inspection System Overview

1. Select the high temperature wedge-array system

4. Calculate focal laws

5. Perform the scan via application of the calculated focal laws

6. Time adjust the scan results for correct flaw positioning

2. Build a scan plan for the inspection

3. Calculate temperature profile in inspection system

Acknowledgement

This work was sponsored by Eclipse Scientific and theCanadian Natural Sciences and Engineering ResearchCouncil (NSERC).