Simulating a Transmit Receive Longitudinal (TRL) Inspection

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In this tutorial we will learn how to simulate a full 3D model of a TRL (Transmit Receive Longitudinal) inspection of a steel pipe with water. We will use CAD importation for the model geometry.

We will learn:

  • How to import CAD
  • How to apply mechanical load to a surface
  • How to solve the model to calculate the acoustic pressure received

Problem Definition

model.png

Characteristics of the model

Model: TRL inspection with Block Angle = 15 degrees and Wedge Angle = 162 degrees
Mesh Size: 16 Elements / Wavelength
Analysis Time: 0.1 ms
Output Results:

- Time History of Acoustic Pressure at Receiver (0.025,0.02,0.035) m

- Maximum Acoustic Pressure Field

Material Data

Name

Code Name

Density 

Bulk Velocity 

Shear Velocity

Rexolite

rxlt

1060 kg.m-3

2340 ms-1

1100 ms-1

Stainless Steel, Generic 

stst

7890 kg.m-3

5790 ms-1

3100 ms-1

Vacuum

vacm

0 ms-1

0 ms-1

0 ms-1

Water watr

1000 ms-1

1496 ms-1

0 ms-1

Why This Simulation?

There are many issues associated with inspection, including accessibility and critical defect sizes, but the most important issue regards the accurate positioning, sizing and characterisation of flaws. TRL is a popular method for near-surface inspection and simulating the inspection design is necessary for optimization.

In this simulation we will transmit from one probe on the wedge into the pipe and receive on the other probe.

The Simulation Process

Step 1 - Creating a New Project

Before we begin we must create a new project.

  1. Click New Project to open the New Project window
  2. Enter Model Name
  3. Click ... to choose a directory to save the project
  4. Click OK to create the project
new_prjct.png

Step 2 - Set the Frequency of Interest

First we will specify the frequency of interest.

  1. Select Project Settings in the Model Tree
  2. Expand the Frequency of Interest property
  3. Tick the box
  4. Enter a value of 150,000
project_settings.png

Step 3 - Adding the Materials

First we will add the materials needed from the material database.

Stainless Steel

We need stainless steel for the pipe.

  1. Click Project Materials to open the Material Database
  2. Expand the Metal material tab
  3. Double click 'Stainless Steel, generic - stst' to add this to Project Materials
ststs.png

Rexolite & Vacuum

We require rexolite for the wedge and vacuum for the probes.

  1. Expand the Misc material tab
  2. Double click 'Rexolite - rxlt' to add this to Project Materials
  3. Double click 'Vacuum- vacm' to add this to Project Materials
rxlt-vacm.png

Water

  1. Expand the Fluid material tab
  2. Double click 'Water at 25C- watr' to add this to Project Materials
  3. Select Done to close the Project Material Database
water.png

Step 4 - Import Geometry

We will make use of this BDF File containing a model of a 3D TRL Inspection.

Download: TRL STEP File

  1. Select Import button
  2. Select ... and locate 'TRL.step'
  3. Select Import
import.png

Step 5 - Assign Materials to Parts

We must now assign each model part a material.

Wedge

  1. Expand Geometry in the Model Tree
  2. Right click part_1 > Assign Material > rxlt
part1.png

Probes

  1. Right click part_2 > Assign Material > vacm
part2.png
  1. Right click part_3 > Assign Material > vacm
part3.png

Pipe

  1. Right click part_4 > Assign Material > stst
part4.png

Water

  1. Right click part_5 > Assign Material > watr
part5.png

Step 6 - Setting up the Mesh

We will now change the mesh settings to use 16 elements per wavelength

  1. Expand Model in Model Tree
  2. Expand Mesh
  3. Select Configuration
  4. Set Definitions to Advanced
  5. Set Elements Per Wavelength to 16
  6. Expand Mesh Velocity and set to Defined
  7. Set Mesh Velocity Value to 1100
mesh.png

Step 7 - Creating a New Load

Adding a Time Function

We need to assign a pressure load to the transmit probe so we require a drive function. For this model we will use with a Sinusoidal drive function.

  1. Expand Forcing Functions in the Model Tree
  2. Click '+' to open the Time Function window
  3. Change Drive Frequency to 150,000
  4. Click Insert
time.png
 

Creating a Load

  1. Expand Boundary Conditions in Model Tree
  2. Click '+' to open the Load Definition window
  3. From Model Graphics tab, select Set View Plane > Set Plane XY
  4. Untick part_1 to hide part in view
  5. Rotate axis about x until the base of part_2 is in view
  6. Select the base of part_2 so that it appears in Current Selection in the Load Definition window
  7. Select Create Load
load_def.png

Editing the Load properties

Once the load is created, we have to associate to it the time function we added to our project previously.

  1. Select load_1
  2. Set Forcing Function to timefunc_1
  3. Set Amplitude Scale Factor to 1
load_prop.png

Step 8 - Setting up Boundary Conditions 

We will need to change all boundaries except Ymin to Absorbing conditions because we are only simulating part of the pipe and the waves would continue on and not reflect off of the boundaries. Ymin is free as this is the boundary at our probes.

  1. Click Domain Boundaries 
  2. Expand X Minimum and set Boundary Type to Absorbing
  3. Expand X Maximum and set Boundary Type to Absorbing
  4. Expand Y Minimum and set Boundary Type to Absorbing
  5. Expand Z Minimum and set Boundary Type to Absorbing
  6. Expand X Maximum and set Boundary Type to Absorbing
boun.png

Step 9 - Setting Analysis Time

We will now set the model simulation time to be 0.0001 seconds

  1. Click Analysis 
  2. Set Simulation Run Time to 0.0001
analysis.png

Step 10 - Choosing Output Results

We will now define 2 outputs, a time history of the acoustic pressure at the receiver and the maximum pressure array.

1 - Time History of Acoustic Pressure at Receiver [0.025,0.02,0.035 ]m

  1. Click '+' this will create a new output 
  2. Change Output Type to Time History
  3. Set Location > X to 0.025
  4. Set Location > Y to 0.02
  5. Set Location > Z to 0.035
out1.png

2- Maximum Acoustic Pressure Field

  1. Click '+' this will create a new output 
  2. Change Output Type to Field Data
  3. Change Field Type to Maximum
out2.png

Step 11 - Launch the simulation on the Cloud

At this point the model is completely set up and it can now be run on the cloud.

  1. Click Run on Cloud 
  2. Click Estimate
  3. Click Run
run.png

Step 12 - Post Processing Simulation Results 

Download the results from the cloud

The simulation results will need to be downloaded from the cloud storage in order to analyse the results in the post processor.

  1. Select Storage icon
  2. Locate the job from the dropdown menu
  3. CTRL + select the .flxdato and .flxhst file, right click and select Download Selection
download.png

Choose an appropriate save location when the file explorer pops up and click Select Folder to close the window.

Switch to the Post Processor 

Important: Once you downloaded the results from the cloud, those results will be available on your computer locally. You will then need to open them into the post-processor to visualize them.

  1. Click this icon to access the Post Processor 

Open Results 

  1. Click File Explorer
  2. Expand the job simulation folder
  3. Double click .flxdato file and .flxhst file to open them in Results Manager
file_exp.png

Plot Time History 

  1. Double click 'aprs' in Results Manager to plot acoustic pressure curve
aprs.png

Plot Data Array (Maximum Pressure)

  1. Double click 'apmx' in Results Manager to plot maximum pressure data array
  2. Select Continue
  3. Set Scale Factor to 0.5
  4. Rotate model to view maximum pressure at different parts of the model
apmx.png

Try for yourself 

Now that we have introduced you to the tutorial try have a play around with some of the settings, add some other outputs, or use this model as a starting point for your own.

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