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Finite Element Analysis of Ultrasonic Phased Array

Inspections on Anisotropic Welds

Paul ReynoldsPaul ReynoldsWeidlinger Associates IncWeidlinger Associates Inc

Contents

• IntroductionIntroduction

• Anisotropic Weld StructureAnisotropic Weld Structure

• Finite Element Modelling of InspectionFinite Element Modelling of Inspection

• Application of Total Focusing Method Application of Total Focusing Method

(TFM)(TFM)

• Time Reversal Acoustics (TRA)Time Reversal Acoustics (TRA)

• Results of TRA and TFMResults of TRA and TFM

• ConclusionsConclusions

Introduction

• Weld integrity of the upmost importance in Weld integrity of the upmost importance in

modern industrymodern industry

• Exotic materials used more and more Exotic materials used more and more

frequently due to increasing performance frequently due to increasing performance

demandsdemands

• Anisotropic behavior of these complex Anisotropic behavior of these complex

materials make conventional ultrasonic materials make conventional ultrasonic

inspection methods unreliableinspection methods unreliable

Introduction

• Semi-analytical models cannot adequately Semi-analytical models cannot adequately

deal with extensive material boundaries that deal with extensive material boundaries that

exist in such mediaexist in such media

• FEA offers potential for investigating FEA offers potential for investigating

performance new ultrasonic inspection performance new ultrasonic inspection

methods on these structuresmethods on these structures

• Simulated inspection data can be readily Simulated inspection data can be readily

compared to experimental data if availablecompared to experimental data if available

Anisotropic Weld

• EBSD provides material/color map of weld EBSD provides material/color map of weld

dependent on dominant crystal dependent on dominant crystal

orientation (40 micron resolution)orientation (40 micron resolution)

Inspection Details

• 128 element piezocermic array:128 element piezocermic array:• 0.5mm ceramic elements0.5mm ceramic elements

• 0.5mm polymer kerf = 1mm pitch0.5mm polymer kerf = 1mm pitch

• 1.5MHz centre frequency1.5MHz centre frequency

• Full Matrix Capture data processingFull Matrix Capture data processing• Transmit on 1 element, receive on all othersTransmit on 1 element, receive on all others

• Repeat for all element to give 128x128 tracesRepeat for all element to give 128x128 traces

• 3mm diameter Side Drilled Hole defect3mm diameter Side Drilled Hole defect

• Array positioned directly on top of weldArray positioned directly on top of weld

• Weld represents join in a water filled pipeWeld represents join in a water filled pipe

FE Inspection

• Weld map can be read directly into Weld map can be read directly into

PZFlexPZFlex

• Material properties of orientations Material properties of orientations

calculated in PZFlexcalculated in PZFlex

FE Details

• PZFlex is a transient code that can provide time-PZFlex is a transient code that can provide time-

traces for each element’s response in the FMCtraces for each element’s response in the FMC

• Properties for each orientation calculated from Properties for each orientation calculated from

stiffness matrix and rotational anglesstiffness matrix and rotational angles

• Each element is effectively a unique model Each element is effectively a unique model

therefore can be simulated as 128 separate therefore can be simulated as 128 separate

modelsmodels• If paralleled all 128 models can be ran simultaneouslyIf paralleled all 128 models can be ran simultaneously

• Simulation for each element takes less than Simulation for each element takes less than

1minute on a typical workstation = < 90minutes 1minute on a typical workstation = < 90minutes

totaltotal

FE Inspection - Example

TFM – Isotropic Delays

• TFM focuses on every point in the imageTFM focuses on every point in the image

• Reflections from the grain boundaries can clearly be Reflections from the grain boundaries can clearly be

seenseen

TRA – Delay correction

• Treat defect as a cylindrical source and record delaysTreat defect as a cylindrical source and record delays

• Reverse delays and use as elemental timings to create Reverse delays and use as elemental timings to create

true focus through heterogeneous mediatrue focus through heterogeneous media

Correction Effect on Focus

Correction Effect on Focus

TRA delays

Isotropic delays

TFM with TRA delays

• Correct focal laws generate improved defect Correct focal laws generate improved defect

resolution, amplitude and positioningresolution, amplitude and positioning

• Everything outside the focus remains distortedEverything outside the focus remains distorted

20dB Threshold Comparison• Applying 20dB threshold removes grain boundary reflectionsApplying 20dB threshold removes grain boundary reflections

• TFM with correct TRA produces an image comparable to the TFM with correct TRA produces an image comparable to the

ideal isotropic case at the defectideal isotropic case at the defect

Conclusions

• Paul – thought I’d let you draw your own Paul – thought I’d let you draw your own

conclusions as you’ll be presenting it.conclusions as you’ll be presenting it.