Citation
Magnetically induced velocity change to measure residual stress

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Title:
Magnetically induced velocity change to measure residual stress
Creator:
Woodham, David B
Publication Date:
Language:
English
Physical Description:
83 leaves : illustrations ; 29 cm

Subjects

Subjects / Keywords:
Iron and steel bridges ( lcsh )
Steel, Structural -- Fatigue ( lcsh )
Iron and steel bridges ( fast )
Steel, Structural -- Fatigue ( fast )
Genre:
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Includes bibliographical references.
General Note:
Submitted in partial fulfillment of the requirements for the degree, Master of Science, Civil Engineering.
General Note:
Department of Civil Engineering
Statement of Responsibility:
by David B. Woodham.

Record Information

Source Institution:
|University of Colorado Denver
Holding Location:
|Auraria Library
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
28691453 ( OCLC )
ocm28691453
Classification:
LD1190.E53 1993m .W66 ( lcc )

Full Text
MAGNETICALLY INDUCED VELOCITY CHANGE
TO MEASURE RESIDUAL STRESS
by
David B. Woodham
B.S., University of Colorado, 1985
A thesis submitted to the
Faculty of the Graduate School of the
University of Colorado at Denver
in partial fulfillment
of the requirements for the degree of
Master of Science
Civil Engineering
1993
n
y


This thesis for the Master of Science
degree by
David B. Woodham
has been approved for the
Department of
Civil Engineering
by
Alcu, 5. m3


Woodham, David B. (M.S., Civil Engineering)
Magnetically Induced Velocity Change to Measure Residual Stress
Thesis directed by Assistant Professor Andreas S. Vlahinos
ABSTRACT
The Magnetically Induced Velocity Change (MIVC) method is currently under
study by the Federal Highway Administration as a nondestructive technique to
measure residual stress in steel bridge components. The MIVC method exploits
the magnetoelastic effect in ferrous materials to determine the magnitude and
sign of stress in typical bridge steel. The magnetoelastic effect says that the
presence of an internal stress in a ferromagnetic material, in any direction other
than that of an applied magnetic field, will change the direction of magnetization.
The rotations of the magnetic domains to align with an applied magnetic field
affect the velocity of ultrasonic waves. The velocity change of ultrasonic waves
in stress-relieved steel specimens was measured under known uniaxial stress
conditions in typical bridge steels (ASTM A36, A588 and A572). The velocity
of the ultrasonic waves varied with the applied magnetic field and with the stress
in the steel. Reference curves of the change in velocity plotted against the
applied magnetic field are unique for a given stress. Reference curves were
taken with the magnetic field parallel and perpendicular to the applied stress.
m


Unknown stress can be identified by changing the orientation of the applied field
so that the MIVC is maximum and measuring the MIVC at this and a
perpendicular orientation. The measured responses are then compared to
reference curves of the same type steel. With the current instrumentation, the
accuracy of the MIVC method is approximately 10 ksi.
This abstract accurately represents the content of the candidates thesis.
I recommend its publication.
Signed
Andreas S. Vlahinos
IV


CONTENTS
Chapter
1. Introduction....................................................1
1.1 Physical Background............................................1
2. Experimental Procedure..........................................5
2.1 Instrumentation................................................5
2.1.1 Measuring the Magnetically Induced Velocity Change........... 5
2.1.2 Measuring the Magnetic Field.................................8
2.1.3 The Computer Controller......................................9
2.2 Specimen Preparation...........................................9
2.3 Testing Method................................................ 15
3. Results.........................................................22
4. Discussion......................................................24
5. Future Study....................................................25
Appendix
A. Graphs of the Collected Data...................................26
B. Listings of the Computer Programs Used.........................77
References.........................................................84
v


1. Introduction
This study investigated the accuracy and repeatability of the
Magnetically Induced Velocity Change (MIVC) method to measure uniaxial
stresses in three types of steel. The equipment and procedures used were
developed under contract with FHWA by Southwest Research Institute
(SwRI). The work done at SwRI demonstrated that the MIVC method was
capable of measuring residual stresses in steel components of highway bridges.
However, further testing was needed before FHWA could proceed with
implementing this technology. The MIVC method measures the change in
velocity of ultrasonic waves in ferromagnetic materials due to an applied
magnetic field.
1.1 Physical Background
How does a magnetic field effect the velocity of sound waves in steel?
In ferromagnetic materials, the orbit and spin of the electrons give rise to a
magnetic moment in the atom. The magnetic moments are parallel in regions
known as magnetic domains. A single crystal (grain) of iron may contain a
few or many domains. The magnetic domains will tend to align in the axes of
easy magnetization (these are the 6 <100> directions in body-centered cubic
iron crystals). As a result, there will be no net magnetization in the absence
of a magnetic field because all easy directions will be equally used. However,
1


due to the application of a magnetic field, the domains will rotate to align with
the external field which increases the magnetization in the material. In the
process of rotating to align with the magnetic field, strain is produced in the
crystalline lattice. This is known as the Joule effect or magnetostriction. This
effect also occurs in reverse in that a strain applied to the crystal will rotate
the domains to a new position which will minimize the total energy of the
crystal. When an acoustic wave is propagated through a ferromagnetic
material, there are two types of strain produced in the material. The first
strain term is due to the elastic vibrations of the atoms. The second strain
term is that produced by the rotations of the domains in response to the
applied stress wave. These two strain terms will combine to change the
velocity of waves in a ferromagnetic materials.
The velocity of sound in a material is approximately:
where E is the elastic modulus and p is the mass density of the material
using the substitution,
e
where a and e are the internal stress and the resulting strain,
2


the equation becomes,
V-
o

pe
As discussed above, there are two contributing strain terms so that the velocity
is now:
V-.
The velocity change in structural steels due to the magnetostrictive
strain term is on the order of 103 to 10'4. The MIVC is dependant on the
relative orientations of the residual strains, the applied strains, and the applied
magnetic field. This effect can be seen in Figure 1.
o
P(e+eJ
3


Orientation of Stress and Magnetic Field on the Rotation of the Domains.
In the left half of Figure 1, the applied stress and magnetic field are
perpendicular (ct _l H). A compressive stress will tend to reduce the domain
rotations (shown by the smaller angle between the small arrows) and a tensile
stress will tend to increase domain rotations due to the elastic wave. Reduced
domain rotations reduce the magnetostrictive strain term which increases the
velocity of the acoustic wave and conversely larger domain rotations reduce
the velocity of the acoustic wave. In the right half of Figure 1, the stress and
magnetic field are parallel (a || H) and the effects of compressive and tensile
stresses on the velocity of the acoustic wave are opposite.
4


2. Experimental Procedure
2.1 Instrumentation
The MIVC instrumentation consists mainly of the Matec MBS 8000
ultrasonic testing system, its support components, and a Gaussmeter (RFL
Industries Model 912). An oscilloscope is used for system monitoring and
calibration and a power supply and electromagnet are needed to produce the
magnetic field. The Matec unit is used to measuring the velocity change of the
ultrasonic waves by measuring the phase difference between a reference signal
supplied by the frequency synthesizer (Hewlett Packard Model 3325) and the
received pulse from the transducer (Figure 2).
2.1.1 Measuring the Magnetically Induced Velocity Change
The Matec unit consists of several boards each of which is designed to
perform one or more functions. Each board fits into the main power frame
and can communicate over the IEEE-488 bus to a controlling computer
(Figure 3).
An amplifier is used to generate high voltage "tone bursts" for output to
the sending ultrasonic transducer. The duration of the burst is controlled by
the gate width generator which turns on the amplifier for the duration of the
gate. The frequency of the bursts are synchronized to the reference signal
supplied by the frequency synthesizer.
5


Figure 2. MIVC Equipment and Computer.
6




Figure 3. Instrumentation for MIVC
Measurements.
7


A broadband receiver amplifies the pulse from the receiving transducer
and then filters the pulse to remove the reference signal. A peak detector
provides an output which matches the most positive signal present during the
sampling gate. The sample gate can be controlled by the user as to width and
delay (relative to the sent tone burst).
The quadrature phase detector reads the peak detector and outputs a
signal proportional to sin(<£) where (j> is the phase between the received signal
and the reference signal.
The last board in the unit reads the output of the phase detector during
the time that the sample gate is open and digitizes this voltage for output to
the controlling computer.
2.1.2 Measuring the Magnetic Field
The magnetic field is produced by an electromagnetic coil held in
contact with the specimen. The voltage to the coil is controlled by a
programmable power supply (Kepco Model BOP72). A signal generator is
used to supply a triangular waveform to the power supply so that the magnetic
field is swept from zero to a positive maximum, through zero to a negative
maximum, and back to zero. The Gaussmeter reads the magnetic field in
Oersteds from a Hall-effect probe held on the specimen. The Gaussmeter is
able to communicate the field reading to the controlling computer over the
IEEE-488 bus.
8


2.1.3 The Computer Controller
An IBM AT computer was used to control the MIVC system. The
controlling program was written in HP-BASIC and ran on an HP-Basic
Language Processor board. This board contained its own processor as well as
an IEEE interface (HPIB). A listing of the main program, as well as the
setup program can be found in Appendix B.
2.2 Specimen Preparation
Samples of various types and thicknesses of steel used in highway
bridges were prepared for testing. The specimen numbers and ASTM steel
type are shown in Table 1. The specimens were torch cut from steel plates
allowing a minimum of one times the plate thickness margin away from the
finished dimension. The specimens were saw-cut to rough dimensions (3
inches by 18 inches) and the cut edges were finished on a milling machine
(Figure 4). All specimens are oriented with the long dimension in the rolling
direction. Specimens were stress-relieved in a oven for 4 hours at 1200F and
allowed to cool slowly in the oven. Prior to testing, the dimensions of the
specimens were taken using micrometer. Five measures each of the width and
thickness of the specimen were averaged to determine the cross sectional area
of each bar. An electronic spreadsheet was used to calculate the loads
required to induce uniaxial stresses of 10, 20, and 30 ksi.
9


Specimen Dimensions ASTM
Number Thickness (in.) Length (in.) Width (in.) Designation
B1,B2,B3 1.00 18 3.00 A588
E1,E2,E3 1.00 18 3.00 A572
F1,F2,F3 0.5625 18 3.00 A36
K1,K2,K3 1.00 18 3.00 A588
Ml,M2,M3 1.00 18 3.00 A3 6
Table 1. Specimen Dimensions and ASTM Steel Type.
10


Figure 4. Typical Steel Specimens.
11


12


Figure 6. Closeup of Test Setup in a||H
Configuration
13


Figure 7. Test Setup for axH Configuration.
14


Figure 8. Closeup of Test Setup for a_lH
Configuration.
2.3 Testing Method
Each specimen was mounted in the MTS testing machine which was
capable of producing compressive or tensile forces of 100 kips. The upper and
lower grips of the testing machine were hydraulically locked to prevent any
rotations and reduce the introduction of bending moments into the specimen
15


during compressive loads. When the specimen had been mounted in the
testing machine, the electromagnet was brought in contact with the specimen
and oriented either parallel or perpendicular to the long axis of the specimen
(the stress axis). If the magnet was oriented perpendicular to the axis of the
specimen, additional steel blocks were put in place to increase the strength of
the magnetic field in the specimen.
A Hall-effect probe was mounted against the specimen, midway
between the magnet poles. Acoustic transducers were mounted on the
opposite side of the specimen (Figure 6). The orientation of the transducers
was such that the direction of wave propagation was always parallel to the
magnetic field (Figures 6 & 8). Prior to testing, the gaussmeter and the pulse
velocity measurement system were calibrated. The zero and calibration of the
RFL gaussmeter was adjusted with the Hall-effect probe at least 4 feet away
from any metallic or magnetic materials. The Matec MBS 800 unit was
adjusted by observing the pulse and gate on the oscilloscope. The
amplification of the received pulse was adjusted to provide a pulse amplitude
of approximately 700 mV. The sample-and-hold gate delay was also adjusted
so that the received pulse was centered in the gate (Figure 9).
16


The amplitude of the received pulse was greatly influenced by several
factors: the distance between the acoustic probes, the orientation of the
probes, the amount of shear-wave fluid on the transducers, and the force
applied to hold the probes onto the specimen.
After the measurement devices had been calibrated, testing could
proceed. The magnetic field was swept from zero to a maximum value (200 or
300 Oe), back through zero to the reversed-polarity maximum (-200 or -300
Oe), and then back to zero. This was accomplished by using a signal
generator to control the bipolar power supply. The maximum value for the
magnetic field was determined by the thickness of the specimen. With one-
inch specimens, the electromagnet would only produce a field of 200-250 Oe
when the field was perpendicular to the stress.
The measurement of the velocity change due to the change in magnetic
field strength was done under computer control. The computer constantly
monitored the output of the gaussmeter over the IEEE buss and at
predetermined values retrieved the digital output of the phase detector from
the data buss. The computer program displayed a graph of the magnetic field
strength versus the relative velocity change on the computers screen to aid in
verifying the data as it was being collected (Figure 10). The computer
program also wrote the collected data pairs to an ASCII file for further
processing.
17


Figure 9. Oscilloscope Display Showing Sample and Hold Gate (top)
and Received Pulse (bottom).
18
HUWUHMl


19


Following each test on the specimen, values of the frequency change
between zero and the maximum value of the magnetic field were taken
manually. The frequency which nulled the phased detector at zero magnetic
field was recorded. The field was increased to the maximum field (200 or 300
Oe) and the frequency of the signal generator was changed to null the output
of the phase detector. This frequency was also recorded.
Tests were done at increments of 10 ksi and in orientations where the
magnetic field was parallel and perpendicular to the applied stress in the
specimen. A complete data set for one specimen is shown in Table 2.
Stress Orientation
Zero Stress Parallel and Perpendicular
10 ksi Tension Parallel and Perpendicular
20 ksi Tension Parallel and Perpendicular
30 ksi Tension Parallel and Perpendicular
10 ksi Compression Parallel and Perpendicular
20 ksi Compression Parallel and Perpendicular
30 ksi Compression Parallel and Perpendicular
Table 2. Listing of Tests Performed.
20


The testing of one specimen could be accomplished in approximately
3-4 hours including installing the specimen in the testing machine and setup
time for the instrumentation.
21


3. Results
Data from each test were imported into a computer spreadsheet for
reduction and graphing. Several corrections were made to the original data if
required. If the data showed a missing point due to a lockup of the data buss,
this was replaced with a linear interpolation based on the points just before
and after the missing data. If the curves showed excessive drift between the
starting and ending zeroes, then this was corrected by adding a small
increment to each of the velocity values. A spreadsheet macro was developed
which then would average the four collected curves contained in each
test-ascending and descending magnetic field with both positive and negative
polarities-into a single curve and force the curve through zero. At this point,
the curve shape showed the proper response of the velocity change due to the
change in the magnetic field but the magnitude of the curve needed to be
scaled by the relative frequency change between zero magnetic field and the
maximum magnetic field.
22


Each curve was scaled by the following factor G.
f o ^max
G~£T
where: f0 = the frequency of the signal generator at zero magnetic field
which nulls the phase detector
fmax = the frequency of the signal generator at the maximum magnetic
field which nulls the phase detector
23


4. Discussion
Graphs of the results of all the tests performed are contained in
Appendix A. There is obvious scatter in the data and in some cases, there is a
great deal of overlap of the 10 ksi stress contours. This overlap means that
stress differences of 10 ksi can not be resolved. In some of the worst cases,
stresses with a difference of 30 ksi can not be distinguished. However, in the
majority of the graphs, stress differences of 5-10 ksi can be resolved with
confidence.
The operator of the system has a large influence on the accuracy of the
results. The PI for this study noticed an increased accuracy of the results with
more experience with the equipment. In addition, the quantity of electronic
measurement instruments provided multiple sources of small, but cumulative,
errors. The MATEC unit was returned to the factory during the study but the
unit was found to be functioning properly. The acoustic probes, and their
coupling to the specimen, were most likely the largest source of error.
24


5. Future Study
Future study should be directed at improving the instrumentation with
the aim of increasing the accuracy and ease of use. Suggested improvements
include:
1) More experimental work to develop the system for use in characterizing
biaxial stress.
2) Increasing the accuracy and repeatability of the measurements by
redesigning the system to take advantage of the advances in electronics made
since the system was built in 1980.
3) Reducing the size and increasing the ease of use of the instrument by
utilizing a personal computer (PC) with appropriate internal cards.
4) Developing improved software which self-calibrates the instrument,
automatically collects data, and compares the collected data with stored
reference data to provide the user with a direct readout of stress.
5) Development of a sensor head which contains various acoustic probes, a
magnetic field sensor and can be easily attached to a steel structure. The head
could also rotate under computer control to seek out a maximum/minimum
velocity axis.
25


Appendix A
Graphs of the Collected Data


Relative Velocity Change (I0e6)
MIVC Data, Specimen E1
1' ASTM A572 Steel, (a II H)
0 50 100 150 200
Magnetic Field Strength (Oe)
--A--- -10 ksi '<> -20 ksi ~"D ' -30 ksi A- - + 10 ksi
+20 ksi U +30 ksi O


Relative Velocity Change (I0e6)
MIVC Data, Specimen E2
1' ASTM A572 Steel, (o II H)
Magnetic Field Strength (Oe)
A -10 ksi " 0 -20 ksi 0 -30 ksi A- - + io ksi
- +20 ksi +30 ksi O


Relative Velocity Change (I0e6)
MIVC Data, Specimen E3
1 ASTM A572 Steel, (o II H)
Magnetic Field Strength (Oe)
A 10 ksi ' 0 -20 ksi B -30 ksi A- +10 ksi
+20 ksi +30 ksi O


Relative Velocity Change (I0e6)
MIVC Data, Specimen E1
ASTM A572 Steel, (o 1 H)
Magnetic Field Strength (Oe)
--A--- -10 ksi <>' -20 ksi Q -30 ksi A- - + 10 ksi
+20 ksi +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, Specimen E2
ASTM A572 Steel, (a 1 H)
Magnetic Field Strength (Oe)
--A 10 ksi 1 0 -20 ksi B -30 ksi A- -MO ksi
+20 ksi -- +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, Specimen E3
ASTM A572 Steel, (a 1 H)
Magnetic Field Strength (Oe)
A -10 ksi -0 -20 ksi B -30 ksi - A- +10 ksi
+20 ksi +30 ksi @ O


Relative Velocity Change (10e6)
MIVC Data, E Specimens
1' A572 Steel, (o II H)
e1 O ksi
e2 O ksi
e3 O ksi
e1 + 10 ksi
e2 +10 ksi
e3 +10 ksi
e 1 +20 ksi
e2 +20 ksi
e3 +20 ksi
e1 +30 ksi
e2 +30 ksi
o
50
100
150
200....Q...
e3 +30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (I0e6)
e1 10 ksi
MIVC Data, E Specimens
1' A572 Steel, (o II H)
0 50 100 150 200
B
--A--

0-
A
O
0
e2 -10 ksi
e3 10 ksi
e 1 20 ksi
e2 -20 ksi
e3 20 ksi
e1 -30 ksi
e2 -30 ksi
e3 30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
e 1 O ksi
MIVC Data, E Specimens
1 A572 Steel, (o 1 H)
e
b
--A--
- -0- -
A
O

A'
O'
0 50 100 150 200...q...
e2 O ksi
e3 O ksi
e1 + 10 ksi
e2 +10 ksi
e3 +10 ksi
e1 +20 ksi
e2 +20 ksi
e3 +20 ksi
e 1 +30 ksi
e2 +30 ksi
e3 +30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
e1 10 ksi
MIVC Data, E Specimens
1" A572 Steel, (o X H)
e2 10 ksi
e3 10 ksi
e 1 -20 ksi
e2 -20 ksi
e3 20 ksi
el -30 ksi
e2 30 ksi
e3 30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
MIVC Data, Specimen F1
9/16' A36 Steel, (o II H)
A -10 ksi
+20 ksi
Magnetic Field Strength (Oe)
0 -20 ksi -30 ksi A- - +10 ksi
+30 ksi O ksi


Relative Velocity Change (10e6)
MIVC Data, Specimen F2
9/16' A36 Steel, (a II H)
O 50 100 150 200 250 300
--A--- 10 ksi
- - - +20 ksi
Magnetic Field Strength (Oe)
' o -20 ksi B -30 ksi A- +10 ksi
+30 ksi O ksi


Relative Velocity Change (10e6)
MIVC Data, Specimen F3
9/16' A36 Steel, (a II H)
100 150 200 250 300
Magnetic Field Strength (Oe)
0 -20 ksi -30 ksi A +10 ksi
B" +30 ksi O ksi

o
50

-10 ksi
+20 ksi


Relative Velocity Change (I0e6)
MIVC Data, Specimen F1
9/16' A36 Steel, (a X H)
750
500
250
O
-250
O 50 100 150 200 250 300
Magnetic Field Strength (Oe)
A -10 ksi - < -20 ksi - -30 ksi - A- +10 ksi
+20 ksi +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, Specimen F2
9/16' A36 Steel, (o X H)
Magnetic Field Strength (Oe)
A -10 ksi O -20 ksi -30 ksl A- - +10 ksi
+20 ksi +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, Specimen F3
9/16" A36 Steel, (a H)
o
50
100
150
200
250
300
Magnetic Field Strength (Oe)
-A -10 ksi
+20 ksi
-20 ksi
~S -30 ksi A +10 ksi
+30 ksi O


Relative Velocity Change (I0e6)
MIVC Data, F Specimens
9/16' A36 Steel, (o II H)
f2 O ksi
f3 O ksi
f1 +10 ksi
12 +10 ksi
f3 +10 ksi
f 1 +20 ksi
f2 +20 ksi
f3 +20 ksi
f 1 +30 ksi
f2 +30 ksi
f3 +30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
MIVC Data, F Specimens
9/16 A36 Steel, (o II H)
-A-- f1 -10 ksi
-0-- f2 -10 ksi
a f3 10 ksi
--A-- f 1 -20 ksi
f2 -20 ksi
- -B- f3 -20 ksi
A f1 -30 ksi
0 f2 -30 ksi
B f3 -30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
f 1 O ksi
MIVC Data, F Specimens
9/16' A36 Steel, (o 1 H)
f2
f3
M
f2
f3
f 1
f2
f3
f 1
f2
f3
O ksi
O ksi
+ 10 ksi
+ 10 ksi
+ 10 ksi
+20 ksi
+20 ksi
+20 ksi
+30 ksi
+30 ksi
+30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
f1 10 ksi
MIVC Data, F Specimens
9/16 A36 Steel, (o X H)
- 0 f2 -10 ksi
B f3 -10 ksi
- - A- fl -20 ksi
f2 -20 ksi
--B-- f3 -20 ksi
A f 1 -30 ksi
$ f2 -30 ksi
O 50 100 150 200 250 300""B"" f3 -3 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
MIVC Data, Specimen K1
1' ASTM A588 Steel, (a II H)
O 50 100 150 200
Magnetic Field Strength (Oe)
A 10 ksi 1 0 1 -20 ksi 1Q 11 " -30 ksi A- - +10 ksi
+20 ksi H +30 ksi O


Relative Velocity Change (I0e6)
MIVC Data, Specimen K2
1" ASTM A588 Steel, (a II H)
O 50 100 150 200
Magnetic Field Strength (Oe)
' A-- -10 ksi O- -20 ksi 1 -- -30 ksi A- - +10 ksi
+20 ksi +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, Specimen K3
1 ASTM A588 Steel, (o II H)
O 50 100 150 200
Magnetic Field Strength (Oe)
A- -10 ksi ' O'- -20 ksi ---B-- -30 ksi A- - +10 ksi
+20 ksi M +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, Specimen K1
1 ASTM A588 Steel, (a 1 H)
O 50 100 150 200
Magnetic Field Strength (Oe)
--A -lO ksi -O -20 ksi 1 -30 ksi + 10 ksi
+20 ksi - - +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, Specimen K2
1 ASTM A588 Steel, (o 1 H)
Magnetic Field Strength (Oe)
A -10 ksi "O'.. -20 ksi - CD -30 ksi A- - + 10 ksi
+20 ksi +30 ksi -- O


Relative Velocity Change (10e6)
MIVC Data, Specimen K3
1' ASTM A588 Steel, (o 1 H)
Magnetic Field Strength (Oe)
--A-- - 10 ksi 0 -20 ksi ~ 1 -30 ksi + 10 ksi
+20 ksi I +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, K Specimens
1* A588 Steel, (a II H)
-Ar
k 1 O ksi
k2 O ksi
k3 O ksi
k1 +10 ksi
k2 +10 ksi
k3 +10 ksi
k 1 +20 ksi
k2 +20 ksi
k3 +20 ksi
k 1 +30 ksi
k2 +30 ksi
k3 +30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
MIVC Data, K Specimens
r A588 Steel, (a II H)
A k 1 -10 ksi
-e-
--A--
A
$
B
k2 10 ksi
k3 -10 ksi
k 1 -20 ksi
k2 -20 ksi
k3 -20 ksi
k 1 -30 ksi
k2 -30 ksi
k3 -30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (I0e6)
MIVC Data, K Specimens
1' A588 Steel, (o 1 H)
k 1 O ksi
-Ar
"0 k2 O ksi
-S k3 O ksi
A-- k1 +10 ksi
>-- k2 + 10 ksi
B-- k3 +10 ksi
-A k 1 -*-20 ksi
---k2 +20 ksi
-B k3 +20 ksi
A k 1 +30 ksi
<> k2 +30 ksi
O
50 100 150
Magnetic Field Strength (Oe)
200....Q... k3 +30
ksi


Relative Velocity Change (10e6)
MIVC Data, K Specimens
1 A588 Steel, (o 1 H)
k 1 10 ksi
-e-
&
- A- -

A

o
50
100
150
200
B
k2 10 ksi
k3 -10 ksi
k 1 -20 ksi
k2 -20 ksi
k3 -20 ksi
k 1 -30 ksi
k2 -30 ksi
k3 -30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
MIVC Data, Specimen B1
1' ASTM A588 Steel, (o II H)
O 50 100 150 200
Magnetic Field Strength (Oe)
--A 10 Ksi -0 - -20 ksi --0--- -30 ksi A- - + 10 ksi
+20 ksi +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, Specimen B2
1 ASTM A588 Steel, (a II H)
O 50 100 150 200
Magnetic Field Strength (Oe)
--fa -10 ksi " 0 - -20 ksi -- -30 ksi +10 ksi
+20 ksi +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, Specimen B3
1" ASTM A588 Steel, (a II H)
1000
750
500
250
O
-250
-500
O 50 100 150 200
Magnetic Field Strength (Oe)
--A-- 10 Ksi 0 -20 ksi -"O -30 ksi A- - + 10 ksi
+20 ksi M +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, Specimen B1
1' ASTM A588 Steel, (a 1 H)
O 50 100 150 200
Magnetic Field Strength (Oe)
--A-- -10 ksi 1 0 -20 ksi 1 -30 ksi --A-- + 10 ksi
+20 ksi +30 ksi O


Relative Velocity Change (10e6)
MIVC Data, Specimen B2
1" ASTM A588 Steel, (a 1 H)
1000
750
500
250
O
-250
O 50 100 150 200
Magnetic Field Strength (Oe)
A 10 ksi 0 -20 ksi ---B -30 ksi - A- +10 ksi
+20 ksi - - +30 ksi O


Relative Velocity Change (I0e6)
MIVC Data, Specimen B3
1' ASTM A588 Steel, (a 1 H)
Magnetic Field Strength (Oe)
30 ksi
O
--A--
10 ksi
+20 ksi
20 ksi
+30 ksi
- A- -
+ 10 ksi


Relative Velocity Change (I0e6)
MIVC Data, B Specimens
1' A588 Steel, (a II H)
b2
b3
b 1
b2
b3
b 1
b2
b3
b 1
b2
b3
O ksi
O ksi
O ksi
-MO ksi
-MO ksi
+ 10 ksi
+20 ksi
+20 ksi
+20 ksi
+30 ksi
+30 ksi
+30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
MIVC Data, B Specimens
1' A588 Steel, (a II H)
A--- b1 -10 ksi
e
B
--A--
A
>
O
50
100
150
200
B--
b2 10 ksi
b3 10 ksi
b 1 -20 ksi
b2 -20 ksi
b3 -20 ksi
b 1 -30 ksi
b2 -30 ksi
b3 -30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
MIVC Data, B Specimens
1' A588 Steel, (o J. H)
b1 O ksi
b2 O ksi
b3 O ksi
b1 +10 ks
b2 +10 ksi
b3 +10 ksi
b 1 +20 ksi
b2 +20 ksi
b3 +20 ksi
b 1 +30 ksi
b2 +30 ksi
b3 +30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
b 1 -10 ksi
MIVC Data, B Specimens
1' A588 Steel, (o X H)
b2 -10 ksi
b3 -10 ksi
b 1 -20 ksi
b2 -20 ksi
b3 -20 ksi
b1 -30 ksi
b2 -30 ksi
b3 -30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
750
MIVC Data, Specimen M1
1' A36 Steel, (a II H)
o 50 100 150 200
Magnetic Field Strength (Oe)
--A-- -10 ksi ' 0-- -20 ksi -30 ksi A- - +10 ksi
+20 ksi " " +30 ksi O ksi


Relative Velocity Change (10e6)
MIVC Data, Specimen M2
1' A36 Steel, (a II H)
Magnetic Field Strength (Oe)
---10 ksi 0 -20 ksi -30 ksi A + 10 ksi
+20 ksi +30 ksi O ksi


Relative Velocity Change (10e6)
MIVC Data, Specimen M3
1 A36 Steel, (o II H)
Magnetic Field Strength (Oe)
--A 10 ksi 0 -20 ksi S -30 ksi + 10 ksi
+20 ksi +30 ksi **** O ksi


Relative Velocity Change (10e6)
750
MIVC Data, Specimen M1
1' A36 Steel, (o X H)
Magnetic Field Strength (Oe)
--A-- -10 ksi -20 ksi -- -30 ksi - A- - +10 ksi
" - +20 ksi -- +30 ksi O ksi


Relative Velocity Change (I0e6)
MIVC Data, Specimen M2
1" A36 Steel, (a 1 H)
750
0 50 100 150 200
Magnetic Field Strength (Oe)
A- -10 ksi - 0 -20 ksi ---B-- -30 ksi - A- - + 10 ksi
+20 ksi H +30 ksi O ksi


Relative Velocity Change (10e6)
MIVC Data, Specimen M3
1' A36 Steel, (o J. H)
Magnetic Field Strength (Oe)
A -10 ksi -o- -20 ksi B -30 ksi --A-- + 10 ksi
+20 ksi H +30 ksi O ksi


Relative Velocity Change (10e6)
ml O ksi
MIVC Data, M Specimens
1 A36 Steel, (a II H)
m2 O ksi
m3 O ksi
m 1 +10 ksi
m2 +10 ksi
m3 +10 ksi
ml +20 ksi
m2 +20 ksi
m3 +20 ksi
ml +30 ksi
m2 +30 ksi
m3 +30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
m 1 10 ksi
MIVC Data, M Specimens
1 A36 Steel, (o II H)
0 m2 -10 ksi
D m3 -10 ksi
~ A m 1 -20 ksi
m2 -20 ksi
" 0 m3 -20 ksi
A ml -30 ksi
m2 -30 ksi
O 50 100 150 200 B m3 -30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
MIVC Data, M Specimens
1' A36 Steel, (a 1 H)
m2 O ksi
m3 O ksi
ml +10 ksi
m2 +10 ksi
m3 + 10 ksi
ml +20 ksi
m2 +20 ksi
m3 +20 ksi
ml +30 ksi
m2 +30 ksi
m3 +30 ksi
Magnetic Field Strength (Oe)


Relative Velocity Change (10e6)
MIVC Data, M Specimens
1' A36 Steel, (o J. H)
A.. m 1 -10 ksi
m2 -10 ksi
m3 -10 ksi
ml -20 ksi
m2 -20 ksi
m3 -20 ksi
m 1 -30 ksi
m2 -30 ksi
m3 -30 ksi
Magnetic Field Strength (Oe)


Appendix B
Listings of the Computer Programs Used


MAIN PROGRAM LISTING IN HP-BASIC
10 OPTION BASE 0
20 DIM X$[8]
30 DIM Strings[40]
31 DIM FS[20] ! String for filename
33 ASSIGN @G meter TO 701 !Set up variable name for gaussmeter
34 ASSIGN Matec TO 711 !Set up variable name for Matec unit
40 REMOTE G meter !Put in remote status and clear
50 CLEAR Gmeter
51 REMOTE Matec
52 CLEAR Matec
60 DIM Readings(50)!Array to hold points at which to take data
70 GINIT
80 GRAPHICS ON
90 CLEAR SCREEN
91 PLOTTER IS CRT,"INTERNAL";COLOR MAP"
92 SET PEN 0 INTENSITY 7,.7,.7
93 SET PEN 1 INTENSITY 1,0,0,
94 ALPHA PEN IN
95 KEY LABELS OFF
100 AXES 5,5,65,35,2,2,3 !Draw axis on screen
110 MOVE 65,35 !Move to zero
120 WAIT 1
130 INPUT "INPUT FILENAME(NO PATH, BUT USE .PRN EXTENSION)",FS
140 MASS STORAGE IS ":DOS,A"
150 CREATE FS,100I [Create data file on A drive
160 ASSIGN Pathl TO FS
170 Tol = .0010 Tolerance for taking data
180 Max_gauss=200 Maximum value of magnetic field
190 Min_gauss=00
200 Steps=20 [Number of data points to take
210 REDIM Readings(Steps),
220 Jump=LOG(Max_gauss)/Steps [Use log spacing of data points
230 Fill in array of points to take readings at
240 Readings(0)=0
250 FOR 1=1 TO Steps
260 Readings(I)=EXP (I*Jump)/1000
270 NEXT I
280 ! Constants
281 Hits=0 [diagnostic for number of lockups on data bus
290 Done=0 [boolean to determine if done
300 Now_read=0 [current reading of gaussmeter to take data
310 Next_read=l [next reading of gaussmeter to take data
320 Direction =1 [bolean for ascending or descending
78


MAIN PROGRAM LISTING (CONTINUED)
330 Counter=0
331 Total=0
332 Average=0
333 GOSUB Setup determine direction to plot graph (up or down)
335 GOSUB Getzero !establish a velocity at zero mag. field
336 WAIT 1 Iwait statements are necessary to prevent bus lockup
340 Start main program
350 WHILE DoneOl
351 WAIT .30
360 GOSUB Getx
370 IF (ABS(ABS(Gauss)-Readings(Now_read))) < =Tol THEN
381 WAIT .001
383 GOSUB Gety
384 WAIT .001
385 ON TIMEOUT 7,.07 GOSUB Clearbus
390 RPLOT Gauss*(60000/Max_gauss),Polarity *((Velocity-Average)
/1000),-3
400 OUTPUT Strings USING "DDDD.D,5X,DDDDDDDD";Gauss*1000,
Polarity*Velocity/25
410 OUTPUT @Pathl;String$"
420 IF (Next_read=0) OR (Next_read=Steps) THEN
430 Direction=Direction*(-l)
440 END IF
450 Now_read=Next_read
460 Counter=Counter+l
470 Next read=Next read+Direction
480 IF (Counter=(4*Steps) +1) THEN
490 Done = l
500 BEEP
510 ASSIGN Path 1 TO *
520 DISP "TEST FINISHED"
530 END IF
540 END IF
550 IMAGE 10A,DD.DDDD,12A,DD.DDDD,20X,DDDDDDD,5X,DD
560 IF (Counter/Steps) > 2 THEN
570 Sign=-l
580 ELSE
590 Sign = l
600 END IF
610 DISP USING 550; "TARGET" ,Readings(Now_read)*Sign,
" READING",Gauss,Velocity,Hits
620 END WHILE
630 GOTO Tail
79


MAIN PROGRAM LISTING IN HP-BASIC (CONTINUED)
640 Getx: Get data from gaussmeter
650 ENTER Gmeter;XS
660 IF (NUM(XS[3])< >51) AND (NUM(XS[3])< >50) THEN Offset=-l
661 ON ERROR GOSUB Fixstring
670 IF (NUM(X$[3+Offset])=51) THEN Sign$ = "-"
680 IF (NUM(X$[3+Offset])=50) THEN SignS = + "
690 Gauss=VAL(Sign$&". "&XS[5+Offset])
700 Offset=0
710 RETURN 0
720 Gety: !Get data from matecs
723 ENTER Matec USING "#,W"; Velocity
780 RETURN
781 Getzero: Calculate average zero for y axis
782 DISP "SET GAUSSMETER READOUT TO ZERO...PRESS CONT WHEN READY"
783 PAUSE
785 FOR 1 = 1 TO Steps
786 ENTER Matec USING "#,W";Velocity
787 ON TIMEOUT 7,. 1 GOSUB Clearbus
789 DISP "CALCULATING AVERAGE ZERO... PLEASE WAIT",Steps-I
790 Total=Total+(Velocity/1000)
791 WAIT 1.0
792 NEXT I
793 DISP "OFFSET IS", Total 1000/S teps
794 WAIT 3
795 Average=(Total* 1000)/Steps
798 RETURN
799 Setup: [Determine polarity of matecs readings for graphing
800 DISP "SET GAUSSMETER READOUT TO APPROX",Min_gauss,"PRESSCONT"
801 PAUSE
802 ENTER Matec USING "#,W";Nul read
803 WAIT 1
804 DISP "SET GAUSSMETER READOUT TO APPROX",Max_gauss/1000,
"PRESS CONT"
805 PAUSE
806 ENTER Matec USING "#,W";Max_read
807 IF Nul_read < Max_read THEN
808 Polarity =1
809 ELSE
810 Polarity=-l
811 END IF
812 1DISP "SET GAUSSMETER READOUT BACK TO ZERO AND PRESS CONT "
813 PAUSE
814 RETURN
80


MAIN PROGRAM LISTING IN HP-BASIC (CONTINUED)
815 Clearbus: IClear the hp-ib interface for further data collection
817 CLEAR Matec
818 CLEAR G meter
820 Hits=Hits+l
822 RETURN
823 Fixstring: !
824 X$ = "llllllir
825 ERROR RETURN
826 Tail: ILabel for ending routine
827 END
81


SETUP PROGRAM LISTING IN HP-BASIC (CONTINUED)
370 IF (3.0< P4new) AND (Pnew < 100.0) THEN
375 P4=P4new
380 OUTPUT Matecs USING "#,W";4,P4
390 GOTO 355
400 END IF
410 OUTPUT 1;"ADJUST GATE OVER PULSE ON SCOPE"
420 OUTPUT 1;"DELAY IS CURRENTLY",P6,"INPUT LARGER DELAY-
430 OUTPUT l;"TO MOVE RIGHT, SMALLER TO MOVE LEFT, (0 TO END)"
440 INPUT P6new
450 IF (5 < P6new) AND (P6new < 1000) THEN
460 P6=P6new
470 OUTPUT Matecs USING "#,W";6,P6
480 GOTO 420
490 END IF
500 OUTPUT 1; "PRESS LOCAL KEY ON HP SYNTHESIZER"
510 OUTPUT 1; "PRESS FREQ KEY UNDER ENTRY-
520 OUTPUT 1;"PRESS THE RIGHT ARROW UNDER MODIFY",
530 OUTPUT 1; "UNTIL THE 100S PLACE IS BLINKING"
540 OUTPUT 1; "ADUST THE FREQUENCY UNTIL THE AMPLITUDE-
550 OUTPUT l;"OF THE ECHO IS ZERO-
560 END
82


SETUP PROGRAM LISTING IN HP-BASIC
10 OUTPUT 1;"SETTING UP SIGNAL SYNTHESIZER... PRESS CONT"
30 Freq=5
20 PAUSE
40 Amp=700
50 ASSIGN Signal TO 717
60 REMOTE Signal
70 IMAGE AAA,AA,DD,AA,AA,DDDD,AA
80 OUTPUT Signal USING 70;"FUl","FR",Freq,"MH","AM",Amp,"MV"
90 OUTPUT 1; "FREQUENCY IS SET AT",Freq," MHz-
100 OUTPUT 1; "AMPLITUDE IS SET AT", Amp, "mV"
110 OUTPUT IMPRESS CONT"
120 PAUSE
130 OUTPUT 1;"SETTING UP MATEC MBS-800... PRESS CONT"
140 PAUSE
150 PI =3840
160 P2=0
170 P3=40
180 P4=40
190 P6=200
200 P7 = 100
210 P10 = 10
220 PI 1=2
230 ASSIGN Matecs TO 711
240 REMOTE Matecs
250 OUTPUT Matecs USING "#,W";1,PI
260 OUTPUT Matecs USING "#,W";2,P2
261 OUTPUT Matecs USING "#,W";3,P3
270 OUTPUT Matecs USING "#,W";3,P3
280 OUTPUT Matecs USING "tf,W";4,P4
290 OUTPUT Matecs USING "#,W";6,P6
300 OUTPUT Matecs USING "#,W";7,P7
310 OUTPUT Matecs USING "#,W";10,P10
320 OUTPUT Matecs USING "#,W";11,P11
330 OUTPUT 1;"SETUP COMPLETE......PRESS CONT"
340 PAUSE
350 OUTPUT 1;"ADJUST GAIN TO 700 mV ON SCOPE-
355 OUTPUT 1;"GAIN IS CURRENTLY",P4," "
357 OUTPUT 1;"INPUT NEW GAIN, (0 TO END)"
360 INPUT P4new
83


References
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with Controlled Magnetic Reluctance Under the Poles, "Soviet Journal of
Nondestructive Testing 11, 745, 1975.
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R. E. Green. "Evaluation of Residual Stress Instrumentation,"
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Administration, Washington, D.C., 1987.
H. Kwun and S. C. Grigory. "Residual Stress Measurements in Steel
Components of Highway Bridges," Southwest Research Institute, Contract No.
DTFH61-83-C-0016, Federal Highway Administration, Washington, D.C.,
1985.
H. Kwun and C. M. Teller. "Stress Dependance of Magnetically Induced
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R. Langman. "Measurement of the Mechanical Stress in Mild Steel by Means
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of Rotation of Magnetic Field Strength-Part 2: Biaxial Stress," NDT
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M. Le Floch. "Qualitative Approach to the Effect of Parallel Stresses on Soft
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M. J. Sablik, H. Kwun, G. L. Burkhardt and D. C. Jiles, "Model for the Effect
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