Feasibility Study of Infrared Detection of Defects in ...
Transcript of Feasibility Study of Infrared Detection of Defects in ...
Feasibility Study of InfraredDetection of Defects in Green-State
and Sintered PM Compacts
Souheil Benzerrouk
Worcester Polytechnic InstituteNovember 15th, 2006
Particulate Material Research Center
Reinhold Ludwig
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Objectives
Development of a thermo-electric testingapparatus capable of detecting surface and sub-surface flaws in green-state compacts with twooptions:
On-line, relying on natural convection for surface andmajor subsurface defects (passive)
Off-line using a pulsed thermography scheme throughinduction heating for small subsurface flaws and forelaborate analysis (active)
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Summary of accomplishments Developed a complete theoretical formulation and several models
were devised:
DC step heating
Inductive heating
Defect Parameters
Established a comprehensive finite elements model which includes:
3-D DC heating
Axis-symmetric transient
3D inductive heating
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Summary of accomplishments Constructed a test system capable of:
Inducing current through the part (DC & AC)
Acquiring thermal data
Real time defect detection
Designed a factory friendly software with the following features:
Camera control and operation
Real time data collection and processing
Friendly user interface
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Summary of accomplishments Conducted extensive testing in:
Lab setting with a DC and an AC current source
Manufacturing setting:
Simple compacts
Complex gear made at high rate
Defective parts
Aluminum components
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IR Imaging Technology requires heat source Special camera to record thermal signature Elaborate signal acquisition and processing steps to form
image Additional image analysis post-processing
SUT
Heat source
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IR Imaging- Pros and Cons
Pros: Remote sensing capability Fast response High spatial resolution High temperature range Cameras have built-in image processing capability
Cons: Need for straight viewing corridor with the target Background calibration Cost is primarily determined by camera
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Simple Subsurface Defect Model
Sig n a tu re d u e to
a su b su rfa ce fla w
T im e
T e m p e ra tu re
!
2z
t "
3
1
zc !
These defects will appearwith a reduced contrast
t observation time, z depthof the defect , α thermaldiffusivity, c loss of contrast
Subsurface defects willappear at a later time
PM Pa rt
D e fe cts
Su rfa ce T e m p e ra tu re
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FEM Formulation
Static modeling in 2D - Sensitivity study Surface and Subsurface defects Combination of flaws (various sizes and orientations)
Dynamic modeling in 2D - sensitivity study Extend the 2D model to include the dynamic effects
Dynamic modeling in 2D – Induction heating Electromagnetic model with heat transfer
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FEM Formulation (Combined Static)
1mm x 1mmDefect
20µm x 100µmDefects
Defects’ signature
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Transient Model
Currentstep
t =0.2 sec
t =1 sec
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Transient Modelt =10 sec
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FEM Modeling (Induction)
Modeling
Space
P/M SampleDefect
Induction coil
Model parameters: Green state cylinder
with: 7.25 g/cm3 r=1.5 cm, z=6 cm
Copper inductioncoil with watercooling
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Experimental Testing
Static imaging Green state parts Surface flows, with various shapes,
sizes and orientations Apply simple thresholding algorithm
Dynamic imaging Simple green state and sintered
parts Complex gears
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Test Arrangement
DC Power supply
Motorized presssystem
An IR camera at0.3m away from thesample under test
A computer forprocessing andcamera controls
Contacts
Sample
under test
IR camera
Firewire
Signal processing computer
DC power supply
GPIB
Switch
Function
generator
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Test Arrangement
A switching circuit,for pulse shapingand synchronousoperation
Presssystem
Painted P/Mpart
IR camera
Switchingcircuit
Controlcomputer
DCPowersupply
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Static Measurements
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Test Arrangement
RS 232
c onne c tion
Timing a nd
sync hroniz a tion unit
Pow e r ge ne ra tor
Compute r Syste m
D a ta stora ge unit
Exte rna l ha rd drive
PM pa rt
Induc tion c oil
IR ima ging Softw a re
Fire w ire
c onne c tion
U SB c onne c tion
RS 232
c onne c tion
RS 232
c onne c tion
IR Ca me ra
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Test Arrangement (Induction Heating)
A switching circuit for pulse shaping and synchronous operation
FunctionGenerator
InductionCoil
P/M part
IR cameraInductionHeating Supply
Control and DataProcessingComputer
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Experimental Results: Induction Heating
Part parameters: Green state part
with: 1.0% Cu 0.2% C 0.8% wax
Density range:6.8g/cm3 to7.1g/cm3
Experimental Results
System Settings: F = 50KHz ton= 5sec Ptotal=2kW
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1 cm
Active Testing
Temperature recording when the part is subjected to stepinductive heating of a good part and a defective part
Crack
1 cm
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Distance along profile
Pixel intensity
0 10 20 30 40 50 60160
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Distance along profile
Pixel intensity
Crack signature
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On-Line Testing
Parts courtesy of Nichols Portland
Experimental Results
Manufacturing rate perpress: 900parts/hour
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On-Line Testing: Processing
Experimental Results
0 20 40 60 80 100 120 140 160 180120
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Distance along profile
Pixel Intensity
Setup courtesy of Nichols PortlandProfile along the dotted line
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On-Line Testing: Processing
Experimental Results
Monitoring the temperature of a spot in the production line
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Time (sec)
Te
mp
era
ture
(K
)
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On-Line Testing: Processing
Experimental Results
First derivative in the spatial domain
-4000000
-3000000
-2000000
-1000000
0
1000000
2000000
3000000
4000000
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Series1
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On-Line Testing: Processing
Experimental Results
Second derivative in the spatial domain
-4E+12
-3E+12
-2E+12
-1E+12
0
1E+12
2E+12
3E+12
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Series1
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On-Line Passive TestingSetup courtesy of Metal Powder Products
Camera is setup at 50cm from the press system
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Complete Interactive System
Camera control console
Loading options for the reference frame
Temperature display options
Alarm setup
Display camera info
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Automatic Defect Detection Algorithm
Algorithm implemented in software
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Center of the defect
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Summary
Completed a thermo-electric inspection system Allows on-line and off-line green-state P/M part testing
with high resolution and speed Features our own calibration and synchronization
methodology Developed an extensive software interface for data
processing and evaluation Have applied for patent protection
Are in the process of commercializing the system Registered a business (S. Benzerrouk, CEO)