Title of Invention

A DEVICE FOR MEASUREMENT OF ULTRASONIC VELOCITY AND ATTENUATION IN SOLIDS UNDER DIFFERENT THERMAL CONDITIONS

Abstract A device for the measurement of ultrasonic velocity and attenuation in solid materials under different thermal conditions, which comprises two cylindrical wave guides(4,5) having plane and parallel ends characterized in that the said wave guides being movably fixed coaxially by means such as spring loaded end holders(12) attached to a stand(13) so as to allow placement of a test specimen (1) in between the proximal wave guide ends and fixing of an ultrasonic generating(2) and receiving(3) transducers(2,3) at the distal wave guide ends, the said transducers(2,3) being connected to an ultrasonic pulsar/receiver in turn connected to a digital storage oscilloscope (DSO,shown in fig 6), the said distal wave guide portions being also provided with cooling jackets(7), the said coaxially movably fixed wave guides(4,5) and specimen(l) being enclosed in a tubular heating chamber(6) consisting of a perforated insulating pipe(14) closed at both ends with insulating sheets(15) having co-centric holes for the wave guides(4,5), the said insulating pipe being provided with spirally wound external electrical heating element(lO) connected to a known temperature controller, the said temperature controller having temperature sensors(8,9) placed in proximity of the said specimen(l) and heating element(lO), the said heating element(lO) being enclosed with insulating material(ll) and casing(16), the said the digital storage oscilloscope (DSO) is connected to a personal computer through known interface means selected from measurement storage module and interface cables.
Full Text The present invention relates to a device for the measurement of ultrasonic velocity and attenuation in solid materials under different thermal conditions.
The device of the present invention is a low cost setup especially for the measurement of velocity and attenuation of ultrasonic waves in solid material at different temperatures.
The measurement of ultrasonic velocity and attenuation of ultrasonic waves in a solid material gives the elastic properties of the material. The evaluation of these parameters can be used to characterise the: materials completely. The measurement of ultrasonic velocity and attenuation are the prime factors for ultrasonic Non-Destructive Testing (NOT) for quality assessment of materials. The change in the structure of the materials are well reflected in density / velocity and hence elastic modulus. The phenomenon such as porosity, fatigue, creep and materials strength can be explained through the change in ultrasonic velocity. Similarly, the grain size,, voids and texture can be studied through attenuation measurements. The above studies in the materials can be used to characterise the materials completely for a wide range of temperatures. The establishment of above data on new materials such as composites, ceramics at high temperature is required essentially for the selection of materials for a particular application.
Conventionally, for ultrasonic velocity and attenuation measurements in a material, one can use either pulse echo technique or through transmission technique. The pulse echo technique is depicted in Fig.l of the drawings accompanying this specification, wherein a single transducer (2) is used for generation and reception of the ultrasonic waves sent through a wave guide (4) to a solid specimen (1). In through transmission technique as shown in Fig.2 of the drawings a transducer (2) is used for generation of ultrasonic waves and sending through wave guide (4) through a specimen (1) to the other one (3) used for reception of ultrasonic waves through wave guide (5). In both the methods, the transducer(s) is coupled

with the specimen using a suitable couplant, which provides good acoustic impedance matching between the transducer and specimen.
Then, either by using pulse echo or through transmission technique, the transit time for the ultrasonic waves in the material is measured precisely. The measurement of transit time helps in determining the ultrasonic velocity in the material using the formula U = d/t. By measuring the amplitude of the echoes, attenuation of the ultrasonic waves in the material is determined using the relation a = (l/2d) ln(Io/I). Either of the above two methods is normally applied at room temperature for the measurement of velocity and attenuation in most of the solid materials.
However, the above two experimental arrangements is not suitable for measurement of velocity and attenuation of the ultrasonic waves in a solid material at higher temperatures. In recent years, using the state-of-the art transducers, one can measure the velocity and attenuation, up to 773 K without making any special arrangement using high temperature transducer. However, the cost of the high temperature transducer is very high.
In conventional pulse echo or through transmission experimental setup for high temperature studies, the transducer fails to excite and finally it will not generate ultrasonic waves. Therefore, the transducer (which is a source for generation of ultrasonic waves) should be kept away from the higher temperature region. With the above idea in mind, an attempt has been made to generate ultrasonic waves using transducer, which is kept at room temperature. Thus, the generated ultrasonic waves can be passed through suitable wave guide(s) into specimen, which is kept inside the furnace. In this method, one can use pulse echo or through transmission technique for the measurement of transit time in the material at high temperatures. Therefore, for the transmission of ultrasonic waves from the transducer

into the specimen, a suitable wave guide is more essential to prevent the transducer damage from high temperature effect.
Reference may be made to Marie-Helene Nadal et al. 14th WCNDT, New Delhi, 2259-2262, 1996 wherein an experimental setup has been designed for the determination of velocity (both longitudinal and shear) up to 1273 K on cylindrical specimens as shown in Fig.3 of the drawings. The various parts are specimen (1), transducers (2&3), wave guides (4&5) and the heating chamber (6). The contact impulse method is used with a suitable wave guide to protect the ultrasonic transducers from the thermal exposure. The measurement of time of flight (transit time) in the specimen is performed on different paths corresponding to transmissions and reflections, which allows excluding the effects of the temperature gradients in wave guides. Data processing is adjusted to take into account various deformations undergone by the time: profile of the echoes (especially phase rotation and frequency scattering). This device was used for metallic and composite materials. The accuracy on the elastic constants is in the order of ±1 %.
The drawbacks are :
a) The size of the experimental set up is large (each wave guide length is 330 mm).
b) The technique is not extended for the measurement of attenuation.
c) Necessary spring load arrangement to provide a good contact and uniform
pressure between transducer, wave guide and specimen is not given, which is
essential for attenuation measurement.
d) The possibility of using specimens other than the cylindrical shape were not given.
e) Necessary cooling arrangement to avoid the temperature gradient from the wave
guide on both sides is not given,

f) The possibility of using lower ( Reference may be made to Rajagopalan, Acoust. Lett., 1, pp. 112 - 155, wherein an attempt has been made to design and fabricate an experimental setup for the measurement of velocity and attenuation in solid materials from 373 to 1273 K. The block diagram of the experimental setup is shown in Fig.4 of the drawings. The various parts are specimen (1), heating chamber (6), transducer (2) and cooling jackets (7). The drawbacks are :
a. A larger specimen size is required and the specimen should be made up of three
different faces in a single piece (i.e. different cross sections).
b. One end of the specimen is kept at elevated temperature (i.e. inside the furnace),
while the other end of the specimen is coupled with the transducer (with out the
use of any wave guide) and a provision for cooling arrangement is made on other
end of the sample.
c. The whole specimen under study is not in uniform temperature, since one end of
the specimen is inside the furnace while the other end is outside the furnace.
d. Not applicable for through transmission technique.
e. The temperature gradient on the specimen is not considered.
f. The specimen arrangement setup is not applicable for specimens with small
thickness and therefore, the possibility of using newer small size specimens are
less due to the requirement of larger size of the specimen used in this experiment.

The main object of the present invention is to provide a device for the measurement of high temperature ultrasonic velocity and attenuation in solid materials under different thermal conditions, which obviates the drawbacks as detailed above.
Another object of the present invention is to provide a device which prevents the transducer damages during ultrasonic measurements at higher temperatures.
Still another object of the present invention is to provide a device having provision for the specimen of different shape and size having plane / parallelism between the opposite faces.
Yet another object of the present invention is to provide a device for the measurement of ultrasonic velocity and attenuation through pulse echo technique.
The following are the novelty and inventive steps involved in the device of the present invention :
i) It is a low cost set up and also compact in size and portable
ii) A good contact and uniform pressure between the transducer, wave guide and specimen are essential to measure both velocity and attenuation in solid specimens and is provided by employing the mechanical arrangement (spring load) in the present device, iii) One can determine the velocity of ultrasonic waves in solid specimens using both pulse
echo and through transmission technique.
iv) The transducers are prevented from temperature gradient by using recrystallised alumina / quartz wave guides and also by providing necessary water cooling arrangement at one end of each of the wave guides, which is located outside the heating chamber (The total length of the wave guide chosen in the present device is 80 mm, each).

v) One can measure the ultrasonic velocity and attenuation in solid specimens of thickness up to few millimeters of shape either rectangular / cylindrical solid specimen.
vi) One can easily control the heating rate, and usually the heating rate depends on the physical property of the material to be tested.
vii) The heat radiation from inside the heating chamber is guarded by the special arrangement using asbestos rope / glass wool.
In the drawings accompanying this specification Fig.5 represents the schematic diagram of a part of the device of the present invention. The various parts are:
1. Solid specimen / specimen under study / check / test
2. Transducer - to generate ultrasonic waves
3. Transducer - to receive ultrasonic waves
4. Wave guide - to propagate the ultrasonic waves from transducer (2) to specimen
5. Wave guide - to propagate the ultrasonic waves from specimen to transducer (3)
6. Heating chamber
7. Cooling jacket
8. Specimen temperature sensor
9. Heater temperature sensor
10. Heating element
11. Insulating material - asbestos rope, glass wool
12. Spring load mechanical arrangement
13. Stand - to hold the entire setup
14. Tubular heating chamber - asbestos pipe
15. Insulating sheet - asbestos sheet

16. Casing - thin aluminum sheet.
In Fig. 6 of the drawings a block diagram of the device of the present invention is
shown wherein the transducers (2 & 3) are connected to a high power ultrasonic
pulser / receiver, which in turn is connected to a digital storage oscilloscope (DSO).
The DSO and the ultrasonic pulser / receiver are interfaced with a personal computer
through measurement / storage module and RS232 cables.
The device of the present invention comprises a heating chamber (6), insulating material (11), wave guides (4,5), temperature sensors (8,9), spring load arrangement (12) and electrical accessories. The outer surface of the heating chamber (14) has been crewed like a string in order to wind the heating element (10) to stay away from any short circuit between the succeeding strings of the wire. The two ends of the pipe closed tightly using insulating sheets (15) with a hole at the centre in which the wave guides (4,5) has been positioned. The solid specimen (1) is placed in between one end of each wave guide (4,5) and the transducers (2,3) are fixed in contact with the other end of each wave guide (4,5). The transducer to generate (2) and receive (3) the ultrasonic waves, and the wave guides (4,5) are tightly clamped with a suitable spring load arrangement (12) for providing uniform pressure and good contact without any air gap between specimen (1), wave guides (4,5) and transducers (2,3). Necessary cooling arrangement (7) is also provided to prevent the transducers (2,3) from temperature gradient from the wave guides (4,5). The transducers (2,3) are connected to a high power ultrasonic pulser / receiver which is connected to a digital storage oscilloscope (DSO) arid a personal computer.
In the present invention the through transmission technique is used for ultrasonic velocity and attenuation measurements.

Accordingly the present invention provides a A device for the measurement of ultrasonic velocity and attenuation in solid materials under different thermal conditions, which comprises two cylindrical wave guides(4,5) having plane and parallel ends characterized in that the said wave guides being movably fixed coaxially by means such as spring loaded end holders(12) attached to a stand(13) so as to allow placement of a test specimen (1) in between the proximal wave guide ends and fixing of an ultrasonic generating(2) and receiving(3) transducers(2,3) at the distal wave guide ends, the said transducers(2,3) being connected to an ultrasonic pulsar/receiver in turn connected to a digital storage oscilloscope (DSO,shown in fig 6), the said distal wave guide portions being also provided with cooling jackets(7), the said coaxially movably fixed wave guides(4,5) and specimen(l) being enclosed in a tubular heating chamber(G) consisting of a perforated insulating pipe(14) closed at both ends with insulating sheets(15) having co-centric holes for the wave guides(4,5), the said insulating pipe being provided with spirally wound external electrical heating element(lO) connected to a known temperature controller, the said temperature controller having temperature sensors(8,9) placed in proximity of the said specimen(l) and heating element(lO), the said heating element(lO) being enclosed with insulating material(ll) and casing(16), the said the digital storage oscilloscope (DSO) is connected to a personal computer through known interface means selected from measurement storage module and interface cables.
In an embodiment of the present invention the wave guide used is such as recrystallised alumina, quartz rod.
In another embodiment of the present invention the heating element used is such as nichrome wire.
In still another embodiment of the present invention the insulating pipe and sheets used is such as asbestos pipe and asbestos sheets.
In yet another embodiment of the present invention the insulating material used to cover the heating element is such as asbestos rope, ceramic wool, and glass wool.

In another embodiment of the present invention the ultrasonic pulser / receiver and the digital storage oscilloscope (DSO) are interfaced via known means such as measurement / storage module and interface cables to a personal computer.
During the construction of the tubular heating chamber, the asbestos pipe is sized into 67 mm length with 80 x 70 mm respectively outer and inner diameter. After sizing, threads are made in the pipe, to wind the heater wire to avoid any short circuit between the succeeding wires. In order to radiate the heat energy from heater coil to specimen, small holes from outer to inner area of the asbestos pipe has been made. Then, the heater coil is wound on the thread strings and is tightened at the ends. Now two pieces of asbestos sheet whose diameter is equal to the asbestos pipe were cut and sized to rest the wave guide in the asbestos sheet. A hole has been made at centre of the sized asbestos sheet through which the wave guide is passed into the heating chamber from both the ends. Significant care has been taken in positioning the wave guides and specimen in a straight line to achieve good results. The ends of the wave guides are well polished and made plane / parallel to each other before fixing into the heating chamber. The heating chamber is supported by a stand with a suitable height, which helps in positioning the wave guide and specimen in a straight line. One temperature sensor called specimen sensor is placed near the specimen and the other sensor namely heater sensor is placed near the heating element. After making all arrangements, the transducers namely sender and receiver are made in contact with the other end of the each wave guide. In order to provide a uniform pressure and good contact between transducers, wave guide and specimen, a suitable spring load arrangement is provided. Further, to prevent the transducer from temperature gradient from wave guide, necessary cooling arrangement is also made, if required for use.

The received signals are analyzed with the help of Digital Storage Oscilloscope (DSO) to determine ultrasonic velocity and attenuation in the solid specimen. Using the external Proportional Integral and Derivative (P.I.D.) arrangements, the necessary current is given to the heater coil, to raise the temperature inside the furnace.
Normally, the velocity and attenuation of ultrasonic waves in any solid specimen can be determined by passing the ultrasonic waves into the material. In the case of high temperature studies, the above technique fails due to the transducer, which is used for both generation and reception of ultrasonic waves.
Therefore, in the present invention, the through transmission technique is used i.e. one transducer is used for generation and the other one for reception of ultrasonic waves. Further, in order to avoid the direct heating of the transducer from the furnace, wave guide is used.
In the present invention, the specimen and a part of the wave guides are within the furnace / heating chamber, while the transducer (both sender and receiver) and the remaining part of the wave guides are outside the furnace.
A good and uniform pressure is applied to provide good acoustic matching between the transducer, wave guides and specimen. The transducer is safe-guarded against direct heating. In addition, use is made of recrystallised alumina / quartz as wave guide, for which the temperature gradient is less and hence the effect of temperature on transducer is nil.
The cooling arrangement can also be used to prevent the transducer from temperature gradient, if required.
For the measurement of transit time, two wave guides are kept in contact (without the specimen) and the transit time (t1) of the ultrasonic wave through the wave guides is determined. Then, the given specimen whose ultrasonic velocity is to be determined is inserted in between the two wave guides carefully without altering the position of the wave

guides and transducers. Now, the transit time (t2) is determined. The difference between the transit time t1 and t2 results in the transit time (t) of ultrasonic wave in the given solid specimen. The velocity of the ultrasonic waves in the solid material is determined by substituting t value in the following relation:
(Formula Removed)
where d is the thickness of the solid specimen and the same can be measured using a digital micrometer.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention:
Example-1
Transit time of ultrasonic waves in recrystallised alumina specimen (calibration) Thickness of the specimen = 159.84 mm
(Table Removed)
The same is represented in the form of graph as shown in Fig.7 of the drawings.
Example-2
Velocity of ultrasonic waves in 45V2O5-50TeO2-5Bi2O3 specimen Thickness of the specimen = 4.2675 mm
(Table Removed)
The same is represented in the form of graph as shown in Fig. 8 of the drawings.
It shows that the through transmission technique using wave guides determines well the change in ultrasonic velocities on specimen with rise in temperature. The device of the present invention can be used with specimen of different thickness i.e. from mm to cm range. The damage of transducers due to the rise in temperature is nil. The effect of transit time of the ultrasonic waves through the wave guides due to temperature gradient is negligible. The temperature in the specimen region (furnace) can be raised in a uniform manner using external arrangement. The main advantages of the present invention are :
a. The total cost of the furnace is low and the raw materials used for the construction of
the same are easily available in the market.
b. Compact in size and portable.
c. The specimen, wave guides and transducers are easily clamped without any difficulty.
d. One can use both pulse echo and through transmission technique.
e. Significantly, the transducers were prevented from the higher temperature, since the
recrystallised alumina / quartz rod is used as a wave guide material and necessary
cooling arrangement were provided.
f. One can measure the velocity and attenuation of ultrasonic waves in solid specimens
of different thickness.
g. Heating rate is controlled, and usually the heating rate depends on the physical
property of the material to be tested.
h. The heat radiation from inside the heating chamber is guarded by special arrangement
using asbestos rope, i. A good acoustic contact between transducers, wave guides and specimen.



We Claim:
1. A device for measurement of ultrasonic velocity and attenuation in solids under different
thermal conditions, which comprises two cylindrical wave guides(4,5) having plane and parallel
ends characterized in that the said wave guides being movably fixed coaxially by means such as
spring loaded end holders(12) attached to a stand(13) so as to allow placement of a test
specimen (1) in between the proximal wave guide ends and fixing of an ultrasonic generating(2)
and receiving(3) transducers(2,3) at the distal wave guide ends, the said transducers(2,3) being
connected to an ultrasonic pulsar/receiver in turn connected to a digital storage oscilloscope
(DSO,shown in fig 6), the said distal wave guide portions being also provided with cooling
jackets(7), the said coaxially movably fixed wave guides(4,5) and specimen(l) being enclosed
in a tubular heating chamber(6) consisting of a perforated insulating pipe(14) closed at both
ends with insulating sheets(15) having co-centric holes for the wave guides(4,5), the said
insulating pipe being provided with spirally wound external electrical heating element(lO)
connected to a known temperature controller, the said temperature controller having
temperature sensors(8,9) placed in proximity of the said specimen(l) and heating element(lO),
the said heating element(lO) being enclosed with insulating material(ll) and casing(16), the
said the digital storage oscilloscope (DSO) is connected to a personal computer through known
interface means selected from measurement storage module and interface cables.
2. A device and claimed in claim 1 wherein the wave-guide used is selected from recrystallised
alumna, quartz rod.
3. A device as claimed in claim 1-2 wherein the heating element used is selected from nichrome
wire.
4. A device a claimed in claim 1-3, wherein the insulating pipe and sheets used is preferably
selected from asbestos.
5. A device as claimed in claim 1-4 wherein the insulating material used to cover the heating
element is selected from asbestos rope, ceramic wool, and glass wool.
6. A device for measurement of ultrasonic velocity and attenuation in solids under different
thermal conditions substantially as herein described with reference to the examples and figures
5 to 8 of the drawings accompanying this specification.

Documents:

699-del-2001-abstract.pdf

699-del-2001-claims.pdf

699-del-2001-correspondence-others.pdf

699-del-2001-correspondence-po.pdf

699-del-2001-description (complete).pdf

699-del-2001-drawings.pdf

699-del-2001-form-1.pdf

699-del-2001-form-18.pdf

699-del-2001-form-2.pdf

699-del-2001-form-3.pdf


Patent Number 244567
Indian Patent Application Number 699/DEL/2001
PG Journal Number 51/2010
Publication Date 17-Dec-2010
Grant Date 10-Dec-2010
Date of Filing 22-Jun-2001
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110001, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 VENKATACHALAM RAJENDRAN HEAD, DEPARTMENT OF PHYSICS, MEPCO SCHLENK ENGINEERING COLLEGE, MEPCO ENGINEERING COLLEGE (PO)-626005, VIRUDHUNAGAR (DT), TAMILNADU, INDIA.
2 NALLAIYAN PALANIVELU SENIOR RESEARCH FELLOW, DEPARTMENT OF PHYSICS, MEPCO SCHLENK ENGINEERING COLLEGE, MEPCO ENGINEERING COLLEGE (PO)-626005, VIRUDHUNAGAR(DT), TAMILNADU, INDIA.
3 BIJAY KRISHNA CHAUDHURI HEAD, SOLID STATE PHYSICS DEPARTMENT, INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE, JADAVPUR, CALCUTTA-700032, INDIA.
PCT International Classification Number G01H 5/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA