NASA Technical Memorandum 4545 E_&-1 ^cl

PSIDD: A Post-Scan Interactive Data

Display System for Ultrasonic Scans

Don J. Roth and Steven A. Szatmary

November 1993

NASA
NASA Technical Memorandum 4545

PSIDD: A Post-Scan Interactive Data

Display System for Ultrasonic Scans

Don J. Roth

Lewis Research Center

Cleveland, Ohio

and

Steven A. Szatmary

Cleveland State University

Cleveland, Ohio

1993

National Aeronautics and

Space Administration

Office of Management

Scientific and Technical

Information Division
1

predictions of material behavior, and it can be the basis for

artificial intelligence techniques that allow defect identification based on waveform shapes and property versus frequency

behavior. This type of comprehensive analysis in such a convenient format is not commonly done in conventional ultrasonic

testing.

II. System Overview

a. Hardware and Software

The system uses a VAX 4000 - 200 computer running VAX/

VMS A5.5-1 operating system interfaced to a Grinnell 274

image processing system via a DRV11 direct memory access

board installed on the VAX’s Q-bus. Two video displays are

used (fig. 2(a)). A DEC VT340 terminal is the user terminal

attached to the computer and a Mitsubishi 20LP is the video

display monitor attached to the image processing system. A

cursor control unit is attached to the image processor. Highlevel VAX FORTRAN software used for driving the system

was written at the Lewis Research Center . The Grinnell library

of FORTRAN subroutines3 is called from this high-level software. The user starts the PSIDD program and is queried from

the user terminal. The video display monitor shows ultrasonic

images and the associated waveforms, spectra, and properties.

b. User Interface

The PSIDD user interface consists of the VT340 user terminal, the 20LP video display, the cursor control unit (CCU), and

the PSIDD executable code. PSIDD is started from the user

terminal after logging into an account on the VAX. The user

terminal is used to query the initial user options and display

error messages. The video display monitor is used in conjunction with the CCU to display image and waveform information.

Three different display screens are shown on the video display

during PSIDD operation: (1) image display, (2) waveform

display, and (3) graph display. The image display is used to

view the ultrasonic property images and to select scan locations

where the user wishes to examine the digitized waveforms,

spectra, and frequency-dependent property data. The waveform display is the screen that actually displays this information, and the graph display is a full screen enlargement of one

Summary

An ultrasonic data display system was developed at NASA

Lewis Research Center that allows the user to interactively

examine digitized waveforms and processed information associated with any specific scan location of an ultrasonic contact

scan. This information is displayed on a video display monitor

and includes acquired time-domain waveforms, frequencydomain magnitude and phase spectra, and ultrasonic properties

(pulse velocity, phase velocity, reflection coefficient, attenuation coefficient, attenuation coefficient error) as a function of

frequency for a material. This report describes the system

features and illustrates the system’s usefulness for nondestructive materials characterization.

I. Purpose of PSIDD System

The post-scan interactive data display system (PSIDD) has

been developed for viewing raw (digitized) data and resulting

properties at any scan location on any of the ultrasonic images

formed from ultrasonic contact scans.1 It was developed to

(1) confirm the accuracy of images both from a software signal

processing and hardware performance standpoint and (2) interactively compare ultrasonic properties at different locations

within samples. In ultrasonic contact scanning, two front surface and two back surface ultrasonic pulses obtained using the

pulse-echo configuration are digitized and stored at every scan

location. Subsequently, the pulses associated with each scan

point are Fourier-transformed to the frequency domain and

used in calculating ultrasonic reflection coefficient, attenuation

coefficient, cross-correlation (pulse) velocity, and phase velocity (fig. 1).1

 Images of these ultrasonic properties are then

formed at preselected frequencies. This ultrasonic method is

especially sensitive for quantifying global variations (such as

pore fraction variations) in microstructure1 as well as detecting

isolated material defects2 in monolithic and composite materials. Microstructural variations are indicated via gray or color

scale variations in an ultrasonic image; at such locations there

can be questions as to the validity of the indication. PSIDD

allows the operator to examine the digitized ultrasonic waveforms at such locations and verify whether the waveforms and

the resulting ultrasonic properties are valid, and, if valid, how

the waveforms and properties differ from those at other sample

areas. This form of analysis is likely to yield more accurate
2

of the graphs from the waveform display. The movement of the

CCU joystick and the positioning of the function switches on

the CCU cause PSIDD to switch among the three screens and

perform different tasks depending on which screen is currently

displayed on the video display.

c. Features For Application to Ultrasonic Contact Scan 

 Images

PSIDD first allows the display of any of the ultrasonic

property images at predetermined frequencies generated from

spectral analysis of ultrasonic contact scan data. These images

include cross-correlation (pulse) velocity, phase velocity, reflection coefficient, attenuation coefficient, and attenuation

coefficient error.1 From a grid overlaying the image and

representing the locations where ultrasonic data were obtained,

and the use of the CCU, PSIDD allows the operator to examine

time-domain waveforms at any location where ultrasonic data

were obtained. PSIDD also allows the user to examine at these

locations (1) the frequency-domain magnitude and phase spectra of the waveforms and (2) the calculated ultrasonic material

properties including phase velocity, reflection coefficient, attenuation coefficient, and attenuation coefficient error as a

function of frequency. Digitized and calculated property data

obtained from an ultrasonic contact scan and stored in files are

retrieved via a direct access data retrieval algorithm which

allows display of data at any point. All this information is

displayed on the video display. For the frequency-domain

transformed waveforms and frequency-dependent properties

portions of the video display, the user can move the CCU over

any waveform box to view on video in real-time specific values

of waveforms and properties at any frequency within the

broadband frequency regime realized during the ultrasonic

contact scan. Waveforms are auto-scaled in both horizontal and

vertical directions and can be individually enlarged to take up

the entire video display for more detailed viewing. The user can

choose to view the two back surface waveforms with or without

the ultrasonic system noise subtracted. Where interpolation of

spectra and property data is needed, the user has the choice of

linear or natural cubic spline interpolation.

III. Detailed Explanation of PSIDD Operation and Features

a. Initial Setup and Queries

Before using PSIDD, the user is first required to edit an

initialization file (PSIDD.ini) that tells PSIDD in which file

directory path the image and data files generated from the

ultrasonic contact scan are located. The user then runs PSIDD

by typing “run PSIDD” at the DCL (Digital Command Language) prompt on the user terminal and is queried regarding

data set prefix name. In this example, a scanned silicon nitride

sample having scan information stored in files with file name

prefix SN2_CC_10 is confirmed and PSIDD displays messages to the user terminal regarding the files read in associated

with this prefix (fig. 2(b)). The user is then asked what specific

image type and frequency are desired (fig. 2(c)). Here, as an

example, phase velocity is chosen for the image type and

60 MHz is chosen for the frequency. At this point, the image

display comes up to video with a grid overlaying the image that

represents the locations where ultrasonic data were obtained

(fig. 3(a)). As will be explained, the image can be viewed

without the grid if a clearer view is necessary (fig. 3(b)). In

figure 3(a), the outlying black areas overlayed with the grid

represent areas of the rectangular holder which contained the

disk-shaped sample. A scale marker is present in the lower right

corner below the gray scale bar. The 60-MHz phase velocity

image indicates material gradients via gray scale variations.

These gradients will be investigated with PSIDD in section IV.

Figure 4 shows the CCU attached to the image processing

system that allows options to be executed for the PSIDD

system. Figures 5(a) to (c) show the menus to be used in

conjunction with the CCU for selecting options in the image

display, waveform display, and graph display, respectively.

The CCU has two switches labeled “FUN A” and “FUN B.” All

the options on the three menus are accessed by moving the

cursor control joystick, toggling the FUN A and FUN B

switches (down = 0 and up = 1), and, subsequently, pressing the

ENTER button on the CCU. (For the image processor setup

used at Lewis Research Center, the cursor 1 switch on the CCU

must be in the “up” position to allow cursor viewing.) With

FUN A = 0 and FUN B = 0, by depressing the “Q” key on the

user terminal keyboard and the enter key on the CCU, the user

can quit PSIDD at any point in the program.

b. Image Display

For the image display, the following four options exist as

shown in the image display menu (fig. 5(a)). With FUN A = 0

and FUN B = 1, the image color scheme can be varied from gray

scale to a variety of different color schemes, two of which are

shown in figures 6(a) and (b). With FUN A = 1 and

FUN B = 0, locations where ultrasonic scan data and resulting

property values are deemed questionable (from analysis

performed after the contact scan) are highlighted as shown in

figure 7. Each different color and pattern scheme represents a

different questionable data condition and indicates what ultrasonic property might be affected. Codes BA, BC, BP, and BV

represent locations where attenuation coefficient, crosscorrelation velocity, phase velocity, and both types of velocities, respectively, might be suspect as a result of faulty data.

Code BE represents edge locations for a nonrectangular sample.

Table I gives the criteria used to code the potentially suspect

scan locations.

As explained in the following paragraphs, the highlighting

allows the user to (1) go to highlighted locations for a closer

examination of the digitized and processed data and (2) perform

data filtering as needed to obtain a more accurate image if the
3

data are deemed bad. With FUN A = 1 and FUN B = 1, the user

terminal displays the queries shown in figure 2(b) and the user

has the opportunity to select a new image type. With the video

cursor moved to a specific image location (x = 11, y = 12)

(displayed in the upper right corner of figs. 8(a) and (c)), and

FUN A = 0 and FUN B = 0, the waveform data corresponding

to the cursor location on the image is displayed on video

figs. 8(b) and (d)). If the cursor is not on the image grid area and

FUN A = 0 and FUN B = 0, then the overlayed image grid is

toggled off and on.

c. Waveform Display

The waveform display shown in figure 8(b) has 13 boxes of

information associated with the scan point. The top row of

boxes show digitized time-domain ultrasonic waveform data

from the pulse-echo ultrasonic contact measurement (fig. 1) at

that location. In figure 8(b) the waveforms labeled FS1(T) and

FS2(T) are the first front surface reflections without and with

the sample present on the buffer rod, respectively, where T is

time. The waveforms labeled B1(T) and B2(T) are the first and

second ultrasonic pulses reflected off the sample back surface.

The delay times relative to the main ultrasonic pulse where the

echoes occur are given at the top of the four boxes. The time and

voltage scales of the waveforms are shown in the lower right

and middle left of the boxes, respectively. The time scale is

denoted by a scale marker, and the voltage scale is given in volts

(V)/division (D).

The middle four boxes of the waveform display in figure 8(b)

show ultrasonic properties as a function of frequency. The

equations used to calculate frequency-dependent ultrasonic

properties obtained from the pulse-echo configuration are

given in the appendix. The first box on the left shows the

Fourier-transformed front surface reflections FS1(F) and FS2(F)

magnitude spectra where F is frequency. The spectra are color

coded. Highest magnitude in volt-sec is shown at the upper left,

and frequency scale (auto-scaled based on frequency extent of

magnitude spectra) is shown at the middle right. The selected

image frequency of 60 MHz is pointed at with a dotted line. The

next two boxes to the immediate right show phase angle (θ) and

magnitude spectras for Fourier-transformed back surface

reflections B1(F) and B2(F). The lower left of the phase angle

spectra box shows the lowest phase angle (referenced from

θ = 0°) in terms of number of 360° revolutions (RV) plus the

number of degrees less than 360°. (Please note that the number

of revolutions can be a function of the signal processing

routine’s attempt to provide a continuous curve for phase angle

vs. frequency.) A dotted line in the magnitude spectra box

points to the ratio of the B1(F) and B2(F) magnitudes at the

selected image frequency of 60 MHz. As before, highest

magnitude in volt-sec is shown at the upper left of the magnitude spectra box and frequency scaling (which is the same as for

the FS1(F)/FS2(F) box) is displayed at the middle right of both

boxes. The next box to the right contains two graphs: the upper

one contains phase velocity (cm/μsec) as a function of frequency while the lower one shows the ratio of phase velocity to

cross-correlation velocity as a function of frequency. The next

box to the right displays reflection coefficient as a function of

frequency. As before, the magnitudes of the properties at the

selected image frequency are pointed at with a dotted line and

displayed.

The lowest set of boxes shows attenuation coefficient as a

function of frequency (neper (NP)/cm (CM)) (left-most box),

% error in the attenuation coefficient as a function of frequency

(middle), and an information box (right-most box). The attenuation coefficient box shows color-coded error (± sigma) bands

which were derived from the % error in the attenuation coefficient calculation. The error bands and % error in attenuation

coefficient are necessary to show what frequencies are most

valid for the attenuation coefficient calculation. The information box displays the present date, sample name, sample thickness, scan position, nominal transducer center frequency,

cross-correlation velocity, phase velocity at the selected image

frequency, frequency range over which extreme-value data

filtering/clipping was performed, and whether the scan location

is “good” (G) or “potentially bad” (BA, BC, BP, BV, or BE)

where “potentially bad” refers to the questionable data previously discussed.

At this point, movement of the video cursor into the lower

two rows of boxes on the waveform display allows the display

of ultrasonic property values at any frequency in the lower right

corner of the information box (fig. 8(e)). In figures 8(e) and (f),

phase velocity at 78 MHz and the ratio of B1(F)/B2(F) at

65 MHz are displayed, respectively, by moving the video

cursor into the appropriate boxes. With the waveform display

on video, the following four options exist as shown in the

waveform display menu (fig. 5(b)). With FUN A = 0 and

FUN B = 0, the user is returned to the image display. With FUN

A = 0 and FUN B = 1, the waveform display can be toggled

between color and gray scale schemes (fig. 8(g)). The gray scale

scheme can be used if a gray scale printer is available or gray

scale hardcopies are required. With FUN A = 1 and FUN

B = 0, and the cursor located in one of the two back surface echo

(B1(T) or B2(T)) boxes in the top row of boxes, the specific

waveform can be displayed with or without noise subtracted.

(Noise at the time delays where the back surface echoes were

located was digitized and stored before the couplant and sample

were placed on the ultrasonic transducer.) The bottom text line

in the information box will now show if the waveform is

displayed with or without noise subtracted (fig. 8(h)). With

FUN A = 1 and FUN B = 1, the B2(T) box can now be enlarged

for a closer examination if necessary (fig. 9(a)). With FUN

A = 1 and FUN B = 0, and the cursor located in one of the lower

two rows of boxes showing ultrasonic properties as a function

of frequency, the graph interpolation method can be toggled

from spline to linear. The bottom (small) text line in the

information box will now show if the waveform is displayed

using linear or spline interpolation (fig. 8(e)). Spline interpolation provides smoothed graphs in comparison to those displayed with linear interpolation and is useful when ultrasonic
4

contact scans have been performed at nominal frequencies less

than ~20 MHz. Linear interpolation is a speedier algorithm and

results in only slightly less smooth graphs when ultrasonic

contact scans have been performed at nominal frequencies

greater than ~20 MHz. With FUN A = 1 and FUN B = 1, the

phase velocity versus frequency box can now be enlarged for a

closer examination if necessary (fig. 9(b)).

d. Graph Display

The enlarged graph displays allow more detailed examination of waveforms and frequency-dependent properties. In the

graph displays showing ultrasonic properties versus frequency,

movement of the video cursor allows the display of ultrasonic

property values at any frequency (within the broadband frequency regime realized during the ultrasonic contact scan) in

the lower right corner of the screen (fig. 9(c)). The graph

display menu applies to these enlarged full-screen displays of

one of the graphs on the waveform display, and the following

four options exist. With FUN A = 0 and FUN B = 0, the user is

returned to the waveform display. With FUN A = 0 and FUN B

= 1, the user can toggle the enlarged image between color and

gray scale. If FUN A = 1 and FUN B = 0, and the graph

displayed is one of the two back surface echoes, the noise

subtraction option can be toggled. If FUN A = 1 and FUN

B = 0, and the graph displayed is one of the ultrasonic property

versus frequency plots, then the interpolation method is toggled

between linear and spline. If FUN A = 1 and FUN B = 1, and the

graph displayed is one of the two back surface echoes, the

waveform is displayed with and without the noise subtracted

(fig. 9(d)). If FUN A = 1 and FUN B = 1, and the graph displayed

is one of the ultrasonic property versus frequency plots, the plot

is displayed with both interpolation options (fig. 9(e)).

IV. Examples of Application to 

Materials Characterization

Research at Lewis

Two examples are presented here showing the usefulness of

this system for nondestructive materials characterization. The

examples show post-scan analyses of a silicon nitride disk

sample scanned with a 125-MHz broadband ultrasonic transducer and a ceramic matrix composite (SiC fiber/CalciaAlumina-Silica matrix) plate sample scanned with a 10-MHz

broadband ultrasonic transducer, respectively.

a. Examination of waveforms and frequency-dependent 

properties at different regions of silicon nitride disk

As shown in the previous section, the 60-MHz phase velocity

image of the silicon nitride disk indicates material gradients via

gray scale variations (fig. 3). Specifically, six circular areas of

very dark shading (low velocity), a moderately dark central

region (average to slightly below average velocity), and a light

edge (high velocity) are shown. Through destructive methods,

these regions were shown to differ in pore fraction.1

 The origin

of the differences between the different colored regions

(figs. 8(a) and (c)) can be explored in terms of ultrasonic

properties by examining the waveforms and properties. For

example, examining the phase angle graphs of the different

regions on the waveform displays (figs. 8(b) and (d)) shows that

over the same frequency range the phase angle spread (∆θ) is

greater at the dark spot than at the light edge region. This leads

to the differences in the phase velocity for the different regions

of the disk (a greater ∆θ results in a lower phase velocity), thus

verifying the validity of the image. Moving the video cursor in

the respective phase velocity boxes and comparing velocity

values show the trend of lower velocity at the dark spot for all

frequencies. Also, if the back surface echoes B1(T) and B2(T)

in figs. 8(b) and (d) are compared, the waveforms in figure 8(b)

corresponding to the low velocity location of the disk are

shifted to the right (out in time; B2(T) is most noticeably

shifted) in the respective time windows in relation to those in

figure 8(d) corresponding to the high velocity edge location.

Thus, observed cross-correlation (pulse) velocity differences

between the two regions are verified by examining the digitized

waveforms (see respective information boxes at lower right of

waveform displays).

It is instructive to look at the attenuation coefficient image at

60 MHz of the same sample. When the new image type option

on the image display (FUN A = 1 and FUN B = 1) menu is used,

the attenuation coefficient image at 60 MHz is displayed to

video (fig. 10(a)). Comparing this image with the phase velocity image (fig. 3) shows that sample positions where changes in

velocity with position (i.e., material gradients) were most

severe corresponded to areas of highest attenuation coefficient. 1

Examining waveform displays at high and low attenuation

coefficient locations (figs. 10(b) to (e)) reveals interesting

contrasts. The B2(T) waveform at the high attenuation coefficient location is lower in amplitude and distorted when compared to the B2(T) waveform at the low attenuation coefficient

location. This contrast also manifests itself in the B2(F) magnitude graphs. The B2(F) graph at the high attenuation coefficient location shows a double-peak characteristic (causing the

location to be designated BA [see information box and fig.7])

with a severe dropout in the 60-MHz region as compared to that

for the low attenuation coefficient region. Comparing attenuation coefficient versus frequency behavior shows that (1) the

attenuation coefficient at 60 MHz is more than an order of

magnitude greater at the high attenuation coefficient location

than at the low attenuation coefficient location (both have a

calculated error of ~50%) verifying the validity of the image

and (2) the attenuation coefficient versus frequency slope is

much greater at the high attenuation coefficient location than at

the low attenuation coefficient location in the ~30 to 60 MHz

frequency range. (In this frequency range, the calculated error

in the attenuation coefficient is on the order of ≤50%.) The

phase velocity versus frequency behaviors over the frequency
5

range 10 to 130 MHz also show differences at the two locations.

Both locations show phase velocity decreasing with frequency

but the higher attenuation coefficient location shows a greater

velocity decrease (from ~1.12 to 1.07 cm/μsec) and steeper

velocity versus frequency slope than does the low attenuation

coefficient location (which shows a velocity decrease from

~1.09 to 1.08 cm/μsec). The latter result indicates that sharp

material gradients also affect phase velocity behavior. (Closer

examination of these differences between locations can be

accomplished by using the graph enlarge option [FUN A = 1

and FUN B = 1] on the waveform display menu.) It is

envisioned that different subsurface defect conditions (pore vs.

inclusion) would generate characteristic signatures that could

be identified through the combination of waveform shape and

ultrasonic property versus frequency behavior.

Figure 7 shows a number of scan locations coded BA

including location x = 34, y = 9 (fig. 11(a)). At this point, the

waveform display shows an improperly digitized FS2(T)

(fig. 11(b)). (Note that several situations might result in a scan

point being coded BA as shown in table I.) Thus, the plot of

FS2(F) is abnormal and leads to abnormally low reflection and

attenuation coefficients (below user-specified limits), which if

left unfiltered would result in invalid reflection and attenuation

coefficient images. In this example, locations where points

were coded BA were filtered out; i.e., they had their ultrasonic

property versus frequency plots set equal to the previous

“good” scan point. This is the reason that the ultrasonic property versus frequency plots on the waveform display, as well as

the image locations on the image display, do not appear

abnormal. Thus, PSIDD allows the user to determine whether

filtering is indeed necessary for the coded points and to review

the actual digitization. Figure 7 also shows several points coded

BV, including the scan location x = 15, y = 17 (fig. 11(c)). This

situation results when the B1(T) waveform is improperly

digitized at a lower amplitude setting than for the B2(T)

waveform (note the respective voltage/division [V/D] settings)

(table I and fig. 11(d)). Thus, the plot of B1(F) magnitude is

grossly abnormal. Obviously, this situation is incorrect and

points coded BV are filtered out and subsequently examined

with PSIDD to look at the actual digitization.

b. Examination of waveforms and frequency-dependent

properties at different regions of SiC/CAS composite plate

In this example, a rectangular SiC/CAS composite plate was

contact scanned and the cross-correlation velocity image recalled in PSIDD (fig. 12(a)). This image shows low velocity

regions in the upper left and lower right corners of the image

that correspond to porosity clusters. It is of interest to investigate the differences at the high and low velocity regions.

Moving the cursor to a high velocity scan location (x = 14,

y = 12) at the center of the image (fig. 12(b)) and a low velocity

scan location (x = 2, y = 12) at the upper left corner of the image

(fig. 12(d)), respectively, the waveforms and ultrasonic properties versus frequency behavior can be compared

(figs. 12(c) and (e)). For the low velocity location, the back

surface echoes B1(T) and B2(T) are clearly shifted to the right

(out in time) (B2(T) is shifted most severely) in comparison to

those for the high velocity spot. Thus, observed crosscorrelation (pulse) velocity differences between the two regions are verified by examining the digitized waveforms (see

respective information boxes at lower right of waveform displays). Further significant differences between the two locations are seen in the phase velocity versus frequency and

attenuation coefficient versus frequency plots. For the low

velocity location, phase velocity decreases with frequency

while at the high velocity location, phase velocity increases

with frequency. The slope of the attenuation coefficient versus

frequency plot is significantly greater at the low velocity

location than at the high velocity location.

After the attenuation coefficient image at 6 MHz for the SiC/

CAS plate (fig. 13(a)) is retrieved, the video cursor is placed on

a high attenuation coefficient location to examine the waveforms at that point (fig. 13(b)). In comparison to the waveforms

at a low attenuation coefficient location (which is also a high

velocity location) (fig. 12(c)), it is seen that B1(T) and B2(T)

are highly attenuated and distorted. This manifests itself in

oscillating and distorted B1(F) and B2(F) magnitude spectra

and an oscillating attenuation coefficient versus frequency

behavior with much greater attenuation coefficient values than

those displayed at the low attenuation coefficient location.

Figure 13(c) shows that B2(T) at this scan location retains the

same distorted characteristic with or without system noise

subtracted.

The velocity and attenuation coefficient images of the SiC/

CAS composite reveal features similar to those seen in

conventional x-ray and ultrasonic c-scan images of the composite;2 however, PSIDD affords the opportunity to more

closely examine the interaction of defects with ultrasound. As

for the previous example showing the silicon nitride disk, it is

envisioned that different material conditions in the composite

(pore clusters, excess second phases, etc.) would generate

characteristic signatures that could be identified through the

combination of waveform shape and ultrasonic property versus

frequency behavior.

V. Conclusion

An ultrasonic data display system was developed that allows

the user to interactively examine digitized and processed information associated with any specific scan location of an ultrasonic contact scan. This information is displayed on a video

display monitor and includes acquired time-domain waveforms, frequency-domain magnitude and phase spectra, and

ultrasonic properties (pulse velocity, phase velocity, reflection

coefficient, attenuation coefficient, attenuation coefficient

error) as a function of frequency for a material. This report

describes the system features and illustrates its usefulness for
6

nondestructive materials characterization. This system can

serve as a component of an artificial intelligence system for

automatic defect classification based on wave shape and ultrasonic property versus frequency characteristics. Additionally,

PSIDD can be modified for use with immersion c-scanning

where RF waveforms are digitized and stored. Other features

such as display of waveforms with and without diffraction

corrections can easily be added.

Lewis Research Center

National Aeronautics and Space Administration

Cleveland, Ohio, November 1993

VI. Appendix – Equations Used to

 Calculate Ultrasonic Properties

The following equations are valid for the pulse-echo

configuration (fig. 1). Cross-correlation velocity is calculated

from4

V X = 2

τ o

(1)

where τo is the time shift for which

limT T

T

1 →∞ Bt B − ∫ ( ) O⋅ 2 ( ) t + τ τ () −∞≤ ≤∞ 2

reaches a maximum value and X is sample thickness.

Ultrasonic reflection coefficient is calculated according to5

R f FS f

FS f ( ) = ( )

( )

2

1

(3)

where f is frequency and FS f FS f 1 2 ( ) ( ) and are the Fourier

magnitude spectra of the time domain pulses FS1(t) and FS2(t)

without and with the sample present on the buffer rod,

respectively.

Attenuation coefficient is calculated according to5

α(f) X

B f Rf

B f = () ()

( )

1

2

1

2

ln ( ) 4

where Bf Bf 1 2 ( ) ( ) and are the Fourier magnitude spectra

of time-domain pulses B1(t) and B2(t), respectively. Percent

error in the attenuation coefficient is calculated according to

%

exp

( )

 

.

ERRα α σ

α α

α α

α σ





 



 = 















×

[ ] ( ) [ ] + ( )

( ) −

+































 





+ + ( )( )( )









100 100 1

2

1

4 4

1

1 1 5

1 4

2

2 2 2

2 2 2

0 5

X SNR

XR X

R R

SNR X

exp

where σα is the error in the attenuation coefficient measurement, X the sample thickness, σX the the error in the thickness

measurement, R the reflection coefficient, and SNR the signalto-noise ratio.

Phase velocity is calculated according to6

V f X f ( ) = ( ) = − 2 2 6 1 2

π

θ

θθ θ

∆ , ( ) ∆

where

θ1

1 f 7 B f

B f

1

1

( ) = ( ) ( )

( ) ( )

− tan

Im

Re ( )

and

θ 2

1 f 8 B f

B f

2

2

( ) = ( ) ( )

( ) ( )

− tan

Im

Re ( )

where f is frequency and B1(f) and B2(f) are the Fourier

transformations of time domain pulses B1(t) and B2(t),

respectively.
7

VII. References

1. Roth, D.J., et al.: Quantitative Mapping of Pore Fraction Variations in Silicon

Nitride Using an Ultrasonic Contact Scan Technique. NASA TP–3377.

2. Roth, D.J., et al.; NDE Approaches for Characterization of Microstructural

Variations in Ceramic and Metal Matrix Composites. HITEMP Review

1993, Oct. 28–29, 1993, Cleveland, OH.

3. Grinnell Systems GMR Series Software Package User’s Manual. Release

2.2, June 19, 1981, available from Mark McLoud Associates, 165–F

Criftich Lane, Campbell, CA 95008, (Ph: 408–559–7888).

4. Hull, D.R.; Kautz, H.E.; and Vary, A.: Measurement of Ultrasonic Velocity

Using Phase-Slope and Cross-Correlation Methods. Mater. Eval., vol. 43,

no. 11, 1985, pp. 1455–1460.

5. Generazio, E.R., The Role of the Reflection Coefficient in Precision

Measurement of Ultrasonic Attenuation. Materials Evaluation, Vol. 43,

No. 8, 1985, pp. 995–1004.

6. Sachse, W.; and Pao, Y.H.: On the Determination of Phase and Group

Velocities of Dispersive Waves in Solids. J. Appl. Phys, vol. 49, no. 8,

1978, pp. 4320–4327.

Table I.–Criteria for "Coding" Locations in Ultrasonic Contact Scan Images

Condition

Reflection coefficient at transducer center frequency is

above or below user-specified limits.a

Attenuation coefficient at transducer center frequency is

above or below user specified limits.

Fourier magnitude spectra of second back surface pulse B2(F)

exhibits "significant" double-peak characteristic.

Cross-correlation velocity is above or below user-specified

limits.

The first and last two locations in a scan row for irregularly

shaped (egs. circular) sample.

Phase velocity at transducer center frequency is above or

below user-specified limits.

First back surface pulse B1(T) is improperly digitized at a

lower amplitude setting than for the second back surface

pulse B2(T).

Code and definition

BA - questionable attenuation coefficient values

BCb

 - questionable cross-correlation velocity

value

BEb,c - questionable data at edge locations

BPb

 - questionable phase velocity values

BVb - questionable cross-correlation and phase

velocity data

a

Questionable reflection coefficient will lead to a questionable attenuation coefficient.

b

Points coded BC, BP, BV, or BE are implied to also be coded BA since any questionable waveform of the three

acquired at a scan location will affect the attenuation coefficient calculation. c

When the ultrasonic transducer is located at the interface between the edges of an irregularly shaped sample, such

as a circular puck and the sample holder during an ultrasonic contact scan, scattering effects may take place

making the waveforms of questionable validity.
8

Pressure gauge

Transducer holder

Vibrator

Ceramic sample

Air gap

X-axis

Y-axis

Z-axis

Base

Sample holder

Transducer

Pressure

gauge support

Scanner hardware

Voltage

Time

(b)

(a)

Back surface

Specimen

Front

surface

Buffer

rod

Piezoelectric

crystal To pulserreceiver

Couplant

(membrane

or liquid)

X

FS2(T)

B1(T)

B2(T)

Sample top

surface

Y

(d) X

User terminal

VAX 4000-200

FORTRAN

(including PSIDD code)

Image processor Color

display

X, Y, Z

controllers

Waveform

digitizer

Time base

Time delay

Voltage base

Pressure

sensor

Ultrasonic

pulse-receiver

(c)

Scanner

instrumentation

• Instrument control

• Data acquisition

• Analysis calculation

• Image processing

 and display

GPIB

Air

FS2(T) B1(T) B2(T)

Figure 1.—Ultrasonic measurement method and contact scan system. (a) Diagram of buffer rod-couplant-sample

 pulse-echo contact configuration. FS2(T) = front surface reflection; B1(T) = first back-surface reflection; B2(T) = 

 second back-surface reflection. FS1(T), not shown in this figure but shown in upcoming waveform displays, is 

 acquired without sample or couplant on buffer rod. (b) Resulting waveforms for pulse-echo contact technique. 

 (c) Computer-controlled ultrasonic contact scan system. (d) Schematic (top view) of ultrasonic contact scan 

 procedure showing examples of successive transducer positions along X- and Y-dimensions of sample. 
9

(b)

(c)

Figure 2.—Video display setup, queries to user and messages to user for PSIDD operation.

 (a) Video display setup. (b) Initial query and messages to user terminal. (c) Queries 

 concerning image type and frequency to user terminal.

(a) C-93-06328

Cursor

control

unit

User

terminal

Video

display

monitor
10

Figure 3.—Ultrasonic image (phase velocity, 60 MHz) of silicon

 nitride disk. (a) Image with superimposed grid showing 

 locations of ultra-sonic measurements. (b) Image without 

 superimposed grid.

(a)

(b)

Overlay grid showing

scan locations

Sample

holder

region

Sample

Video cursor Gray scale bar

representing

velocity values
11

Figure 4.—Cursor control unit attached to image processing system.

Enter button

C-93-06329

Fun A and

Fun B

switches

Cursor

switches

Video cursor

joystick used

to move cursor
12

Figure 5.—PSIDD cursor control: menus used in conjunction with cursor control unit for selecting options in PSIDD. 

 (a) Image display. (b) Waveform display. (c) Graph display.
13

Figure 6.—Example color schemes for ultrasonic contact 

 scan images. (a) Example color scheme for image.

 (b) Example color scheme for image.

(a)

(b)
14

Figure 7.—Ultrasonic image (phase velocity, 60 MHz) with

 high-lighted scan locations representing locations of 

 questionable data.

Highlighting color

and pattern schemes
15

Figure 8.—Moving video cursor to different locations in ultrasonic (phase velocity, 60 MHz) image to obtain waveform 

 display at those locations. (a) Video cursor moved to scan location (x = 11, y = 12) of dark color (low velocity).

 (b) Waveform display for scan location x = 11, y = 12. (c) Video cursor moved to scan location (x = 32, y = 4) of 

 light color (high velocity). (d) Waveform display for scan location x = 32, y = 4.

(a) (b)

(c) (d)
16

Figure 8.—Concluded. (e) Moving video cursor in phase velocity box of waveform display allows display of phase velocity 

 at any frequency. (f) Moving video cursor in B1(F)/B2(F) magnitude box of waveform display allows display of ratio B1(F)/

 B2(F) at any frequency. (g) Gray scale color scheme for waveform display. (h) With video cursor in B2(T) box, noise 

 originally present without sample on buffer rod (fig. 1) can be subtracted. 

(e) (f)

(g) (h)
17

Figure 9.—Enlarged displays at scan location x = 11, y = 12. (a) Enlarged display of waveform B2(T).

 (b) Enlarged display of phase velocity graph. (c) Enlarged display with interactive video cursor 

 allowing display of ultrasonic property at any frequency. (d) B2(T) waveform with noise subtracted 

 (green) and without noise subtracted (orange). Not much difference is noted between the two in 

 this example. (e) Percent attenuation coefficient error with spline (green) and linear (orange) 

 interpolation options overlayed.

(d)

(b)

(a)

(e)

(c)
18

Figure 10.—Attenuation coefficient image of silicon nitride disk and movement of video cursor to different 

 locations in image to obtain waveform display at those locations. (a) Attenuation coefficient (60 MHz) 

 image. (b) Video cursor moved to scan location (x = 9, y = 14) of light color (high attenuation coefficient) 

 corresponding to edge of dark region seen in phase velocity (60 MHz) image (fig. 8). (c) Waveform display

 for scan location x = 9, y = 14. (d) Video cursor moved to scan location (x = 22, y = 9) of dark color (low 

 attenuation coefficient). (e) Waveform display for scan location x = 22, y = 19.

(c)

(d) (e)

(b)

(a)
19

Figure 11.—Waveform displays for coded points of ultrasonic (phase velocity, 60 MHz) image of silicon nitride disk. 

 (a) Video cursor moved to scan location (x = 34, y = 9) coded BA. (b) Waveform display for scan location x = 34, y =9.

 (c) Video cursor moved to scan location (x = 15, y = 17) coded BV. (d) Waveform display for scan location x = 15, y = 17.

(a) (b)

(c) (d)
20

Figure 12.—Ultrasonic (cross-correlation) velocity image of SiC/CAS plate and movement of video cursor to 

 different locations in image to obtain waveform display at those location. (a) Image with superimposed grid 

 showing locations of ultrasonic measurements. (b) Video cursor moved to scan location (x = 14, y = 12) of

 light color (high velocity). (c) Waveform display for scan location x = 14, y = 12. (d) Video cursor moved to 

 scan location (x = 2, y = 12) of dark color (low velocity). (e) Waveform display for scan location x = 2, y = 12.

(c)

(d) (e)

(b)

(a)
21

Figure 13.—Ultrasonic (attenuation coefficient, 60 MHz) image of SiC/CAS plate and movement of video cursor to high 

 attenuation coefficient location. (a) Video cursor moved to scan location (x = 4, y = 8) of light color (high attenuation

 coefficient). (b) Waveform display for scan location x = 4, y = 8. (c) Enlarged display of B2(T) magnitude graph showing 

 waveform with noise subtracted (green) and without noise subtracted (orange).

(a)

(b) (c)
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24

A03

PSIDD: A Post-Scan Interactive Display System for Ultrasonic Scans

Don J. Roth and Steven A. Szatmary

Ultrasonics; Nondestructive testing; Signal analysis; Velocity;

Attenuation; Image analysis

Unclassified -Unlimited

Subject Category 38

Don J. Roth, NASA Lewis Research Center; and Steven A. Szatmary, Cleveland State University, 1983 East 24th Street,

Cleveland, Ohio 44115. Responsible person, Don J. Roth, (216) 433–6017.

An ultrasonic data display system was developed at NASA Lewis Research Center that allows the user to interactively

examine digitized waveforms and processed information associated with any specific scan location of an ultrasonic

contact scan. This information is displayed on a video display monitor and includes acquired time-domain waveforms,

frequency-domain magnitude and phase spectra, and ultrasonic properties (pulse velocity, phase velocity, reflection

coefficient, attenuation coefficient, attenuation coefficient error) as a function of frequency for a material. This report

describes the system features and illustrates the system’s usefulness for nondestructive materials characterization.