Title of Invention

"A DEVICE FOR THE MEASURING VELOCITY AND ATTENUATION OF ULTRASONIC WAVES IN SOLID SAMPLE AT LOW TEMPERATURES UPTO 90K"

Abstract A device for the measurement of ultrasonic velocity and attenuation in solid samples at low temperatures, such as over a wide range of temperature from 90 to 303 K which essentially consists of a novel spring loaded arrangement which provides a good contact, gentle and uniform pressure between the crystal and solid sample. The necessary cooling / heating of the sample can be selected depending on the requirements. The device of the present invention makes it possible to measure the ultrasonic velocity and attenuation in solid samples using both through transmission technique and pulse echo method. The above setup also permits use of a low thickness of sample in the order of mm to cm range.
Full Text The present invention relates to a device for the measurement of ultrasonic velocity and attenuation in solid sample at low temperatures.
The device of the present invention is specially for the measurement of velocity and attenuation of ultrasonic waves in solid sample at low temperatures in the range of 90 to 303 K.
Ultrasonic non-destructive characterisation of solid sample plays an important role in the field of Science, Engineering and Industry. In recent years, characterisation of solid samples in a wide range of temperature has been carried out by many workers. The characterisation of samples through ultrasonic non-destructive testing (NDT) have been used to understand the various properties such as physical, structural changes, thermal, elastic moduli, effect of voids, grain size etc. Elastic moduli are closely related to various fundamental solid state phenomena such as specific heat and Debye temperature. Elastic moduli are function of temperature and pressure, and it is also related with the thermodynamic property of the samples.
The temperature dependence of acoustic properties of solid samples such as high temperature superconducting glass, manganese perovskite, semiconducting glass, glass & glass-ceramic, bioactive glass and aeronautic samples has been successfully employed to characterise the samples for proper applications. Particularly, to identify the transition temperature (Tg) in superconducting samples, the anti-ferromagnetic (AF) and charge ordering (CO) in manganese perovskite type samples, structural and physical properties of materials.
In order to carryout the ultrasonic velocity and attenuation measurements in a solid sample, one can use either pulse echo method or through transmission technique. The pulse echo method is depicted in Fig. 1 of the drawings accompanying this specification, wherein a single transducer (2) is used for generation and reception of the ultrasonic waves sent to the solid sample (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 the solid sample (1), whereas the other one is (3) used for reception of ultrasonic waves. In both the methods, the transducers (2,3) is coupled with the solid sample (1) using a suitable couplant, which provides a good acoustic impedance matching between the transducers (2,3) and solid sample (1).
Thus, either by using the pulse echo method or through transmission technique, the transit time for the ultrasonic waves in the solid sample can be measured precisely. The ultrasonic velocity in the solid sample is determined using the formula U = d/t (where t is the time taken to travel the ultrasonic wave in a d distance). By measuring the amplitude of the back wall echoes, attenuation of the ultrasonic waves in the solid sample is determined using the relation a = (-20/2d(m-n))log(Im/In), where m & n are the amplitudes of the mth and nth back wall echoes. Either of the above two methods is normally used at room temperature for the measurement of velocity and attenuation in most of the solid samples.
To carryout the ultrasonic velocity and attenuation measurements in solid samples below the room temperature, a separate experimental arrangement is required to bring the solid sample temperature to very low temperature. Using the specially designed experimental setup, one can measure the velocity and attenuation of ultrasonic waves in solid samples up to liquid helium temperature.
Reference may be made to Ramana and Reddy, Acoust. Lett., 13, (1989) 83, wherein an attempt has been made to design and fabricate an experimental setup for the measurement of velocity and attenuation in solid samples from room temperature to liquid nitrogen temperature. The cross sectional view of the experimental setup is shown in Fig.3 of the drawings. The various parts are solid sample (1), transducers (2,3), vacuum chamber (5), liquid nitrogen chamber (6), rubber rings (15) and movable mechanical clamp screw (49).

The drawbacks are:
a. The solid sample holding arrangement is not suitable for samples with thickness above 55
mm and diameter 25 mm therefore, it is not possible to use higher thickness and diameter
solid samples.
b. Non-usage of couplant, therefore, one cannot get the proper impedance matching between
the solid sample and transducer. Also the shear wave cannot be passed into the solid
sample without providing a good couplant between transducer and solid sample.
c. The solid sample cooling rate was not discussed. Then, there is possibility of crack /
damage in the transducer / solid sample due to the rapid change in temperature in the
solid sample region, while the sample setup is inserted in the liquid nitrogen region.
d. The possibility of using other technique such as pulse echo were not discussed.
e. Using the existing movable mechanical screw arrangement for solid sample / transducer
holder, one cannot give a gentle, uniform pressure between the same, rather the over load
due to the screwing arrangement some time will damage the transducer / solid sample
f. Moreover in the low temperature measurements, X- and Y-cut crystals only can be used
respectively for the generation of longitudinal and shear ultrasonic waves. On the other
hand, the generation of longitudinal and shear wave using transducer at low temperature
will damage the transducer and hence after two or three times of continuous operation
(from low to room temperature and vice versa), damages the transducer and hence it can
not generate ultrasonic waves.
The X- or Y-cut crystal (4) is normally bonded using suitable couplant (48) with the solid sample (1) as shown in Fig.4a of the drawings. The necessary signal to excite the crystal is given (50) and hence it generates either longitudinal / shear ultrasonic waves depending on the type of crystal used.

The transducer is shown in Fig.4b of the drawings, where the X- or Y-cut crystal (4) is mounted in metal case (53). High absorbing materials (52) is used to observe the scattered ultrasonic waves to the backside of the crystal and hence, it generates the ultrasonic waves in the front face of the crystal (4). Buffer materials (51) is also packed in front surface of the PZT crystal (4) to avoid cracks or damage due to the pressure exerted through the solid sample (1) and / or to avoid chemical reactions with the couplant (48). The necessary signal (50) to excite the crystal is given at the backside of the PZT crystal (4).
The main object of the present invention is to provide a device for the measurement of ultrasonic velocity and attenuation in solid sample at low temperatures, which obviates the drawbacks as detailed above.
Another object of the present invention is to provide a device, which prevents the crystal damages during ultrasonic measurements using pulse echo method at lower temperatures by providing a novel spring loaded arrangement.
Still another object of the present invention is to provide a device for the measurement of ultrasonic velocity and attenuation using through transmission technique.
Yet another object of the present invention is to provide a device having provision for the solid sample of different size and thickness having plane / parallelism between the opposite faces.
The device of the present invention is useful to measure the velocity and attenuation of ultrasonic waves in solid samples up to liquid nitrogen temperature. Using X- and Y-cut crystals respectively the longitudinal and shear ultrasonic waves are generated. In the present invention, a PZT crystal is bonded with a solid sample using non-aqueous stop cock grease as a couplant. In order to provide a good contact between the PZT crystal and solid sample, a novel spring loaded mechanical arrangement is provided above the PZT crystal. By applying uniform pressure using the spring loaded arrangement, the solid sample and PZT crystal is

also prevented from any crack during the cooling from room to liquid nitrogen temperature. The efficiency of the heat conduction from liquid nitrogen chamber to sample chamber is increased by means of passing the nitrogen gas in between the said chambers.
In the drawings accompanying this specification in Figs.5,6,7 represents the schematic diagram of the cross sectional view of the device of the present invention, namely cryostat (whole assembly), sample chamber and novel spring loaded arrangement respectively of the present invention. The various parts are:
1. Solid sample / solid sample under study / check / test
4. PZT Crystal
5. Outer vacuum chamber
6. Liquid nitrogen chamber
7. Nitrogen gas chamber
8. Solid sample chamber - the place where the solid sample is placed
9. Lid plate of the solid sample chamber

10. BNC cable tube - signal cable to the crystal
11. Connecting tube - to connect the solid sample chamber with the upper flange
12. Power supply tube - to heater coil
13. Port to vacuum pump
14. Port to Pirani vacuum gauge head
15. Rubber O ring - to seal the vacuum
16. Lower flange of the cryostat
17. Upper flange of the cryostat
18. Bolt & nut - to clamp the lower and upper flanges
19. Liquid nitrogen inlet tube
20. QF25 connector - to connect the vacuum paths

21. Butterfly valve - to seal the vacuum
22. SS bellow - connecting metal hose
23. Teflon bush - to prevent the metal contact between the BNC connector and
cryostat
24. BNC connector - for crystal
25. Electrical power supply connector - to heater coil
26. Sensor connector - to both solid sample and heater sensors
27. Nitrogen gas guide tube - to pass nitrogen gas into the nitrogen gas chamber
28. Thick walled outer vessel of the solid sample chamber
29. Copper vessel - to hold the heater coil and to cover the solid sample holder
30. Solid sample holding stage - where the solid sample is to be placed
31. SS nut - to clamp the solid sample holder discs with the SS threaded rod
32. Lower solid sample holder disc
33. Heater sensor
34. Solid sample temperature sensor
35. Teflon bush - to clamp the crystal gently
36. Solid sample holder upper disc
37. Nylon bush - to prevent any metal contacts in the solid sample holder assembly
38. Heater coil
39. Novel spring loaded arrangement
40. SS tube - supporting tube to prevent the metal contact using nylon bush
41. SS threaded rod - to hold solid sample holding assembly
42. Binding screw - to hold the copper vessel with the sample chamber lid
43. Fine threaded screw

44. Outer cover (bell shaped receptacle) in the spring loaded arrangement where the
fine threaded screw is fixed
45. Inner cover (bell shaped receptacle) to hold the spring and light weight pipe
46. Low tension spring
47. Light weight tube in which the teflon bush is fixed at one end
48. Couplant
A device of the present invention as shown in Figs.5,6,7 comprises a vacuum chamber (5), liquid nitrogen chamber (6), nitrogen gas chamber (7), solid sample chamber (8), PZT crystal (4), temperature sensors (33&34), spring loaded arrangement (39) and accessories (15,23,24,25&26). The outer double walled vacuum chamber (5) is followed by the liquid nitrogen chamber (6) in which the liquid nitrogen is supplied to bring the temperature to 90 K in the solid sample (1) region, and the efficiency of the heat conduction is increased by passing the nitrogen gas in the area (called as nitrogen gas chamber (7)) between the sample chamber (8) and liquid nitrogen chamber (6). The said two chambers are attached with the lower flange (16), and the rate of transfer of temperature to the sample chamber (8) is controlled by the thick walled vessel (28), which is provided as the outer cover of the sample chamber (8). The temperature at the solid sample (1) is monitored by the sample sensor (34) and the other one (33) is used to monitor the temperature at heater coil (38), which is wound on the peripheral surface of the copper vessel (29) clamped with the lid plate (9) by using binding screw (42). The said solid sample (1) / test sample is placed on the sample holding stage (30) which is attached with the lower circular disc (32). The upper circular disc (36) is used to hold the spring loaded arrangement (39) and below the spring load the PZT crystal (4) is coupled with the solid sample (1) by using a suitable couplant. The above said two circular discs (32,36) are connected with three threaded rods (41) with a provision to align the same. The sample holder assembly is fixed with the lid plate (9), and the total sample chamber (8) is

attached with the connecting tube (11). The said tube is fixed with the upper flange (17) which is rested on the lower flange (16) using rubber O ring (15). The signal wires for PZT crystal (4) and sensors (33,34), and heater coil (38) were taken out through the connecting tube (11) and power supply guide tube (12) respectively, and the same can be taken out from the vacuum sealed ports made at the top of the connecting tube (11).
In the present invention the pulse echo method is used for the measurement of velocity and attenuation of ultrasonic waves in solid sample at low temperatures of the order of 90 to 303 K.
Accordingly, the present invention provides a device for the measurement of ultrasonic velocity and attenuation in solid sample at low temperatures, which comprises a cryostat, such as herein described, essentially consisting of a solid test sample chamber (8,28) having a scalable (15) lid plate (9), characterized in that the bottom of the said lid (9) being provided with at least three removably fixed vertical stainless steel tubes (40) enclosing removably fixed coaxially placed vertical stainless steel threaded rods (41) protruding beyond the bottom of the said tubes (40) in such a manner so as to hold a disc (32) by means such as non-metallic bush and stainless steel nut (31), the said disc (32) being provided with a concentrically placed removably fixed test sample (1) holding stage (30), the said tubes (40) being provided at the middle level with an annular disc (36) slidable by means (37) such as non-metallic bush, the concentric annular opening of the said annular disc (36) being provided with fixed vertical bell shaped outer receptacle (44) having a concentric internally threaded hole at the top, the said hole having a matching threaded vertical screw (43) fixed to the top of a bell shaped inner receptacle (45) placed vertically and concentrically inside the said outer receptacle (44), the said inner receptacle (45) being provided with a concentrically and coaxially placed low tension spring (46) fixed to the top end of a light weight vertical tube (47) having a non-metallic bush-pad (35) fixed to the bottom end in such a manner as to

be able to provide pressure contact between a PZT crystal (4) interfaced with couplant (48) to test sample (1) placed on holding stage (30), the said vertical tubes (40), discs (32,36) being enclosed in a copper vessel (29) removably fixed by means (42) such as screw to the bottom of the said lid (9).
In an embodiment of the present invention the copper vessel (29) enclosing the test sample holder is provided on the outer peripheral surface with heating means (38) such as a heater coil.
In another embodiment of the present invention temperature sensors (33, 34) are provided proximally to the copper vessel (29) surface and test sample (1).
In yet another embodiment of the present invention the test sample chamber (8) is enclosed in a nitrogen gas chamber (7) which is enclosed in a liquid nitrogen chamber (6) which is further enclosed in an outer double walled vacuum chamber (5).
In still another embodiment of the present invention the PZT crystal (4), temperature sensors (33,34) and heater coil (38) are connected to ultrasonic pulser / receiver, temperature controller and power supply, respectively.
In a further embodiment of the present invention the device is connected to a digital storage oscilloscope and a personal computer through conventional interfaces.
The novel device of the present invention comprises two cylindrical chambers (5,6) being attached at one end with the lower flange (16) and the other ends of each (5,6) is closed separately, so as to provide a good vacuum in the vacuum chamber (5). The nitrogen gas chamber (7) and solid sample chamber (8) being connected with a vacuum pump (13). The liquid nitrogen is supplied in the liquid nitrogen chamber (6) to bring the low temperature inside the device (8). The temperature from the liquid nitrogen chamber (6) is transferred to the solid sample region (8) through a media of inert gas supplied in the nitrogen gas chamber (7). The transfer rate is being controlled by the thick walled outer vessel (28) of the solid

sample chamber (8). The said solid sample chamber (8) consists of the test solid sample (1) coupled with the PZT crystal (4) and the two (1,4) were placed on solid sample holding stage (30) and were clamped using the spring loaded arrangement (39). The PZT crystal (4) is connected to an pulser / receiver in turn connected to a digital storage oscilloscope (DSO). The said spring loaded arrangement (39) consists of a low tension spring (46) which positioned between inner cover pipe (45) and light weight pipe (47) and the three (45,46,47) were held with outer cover pipe (44) using fine threaded screw (43). The said spring loaded arrangement (39) is held by the upper disc (36) of the solid sample holder, which is clamped with the nut (31) positioned with the lid plate (9). The lid plate (9) is fixed with the connecting tube (11) finally fixed to upper flange (17). The said flange (17) is rested with rubber O ring (15) and bolt-nut (18) to provide tight vacuum in the nitrogen gas chamber (7). The materials used in the construction of the device are stainless steel. The lower and upper flanges were sized and well polished having thickness 10 mm and diameter 275 mm with a diameter 93 mm hole at the centre so as to insert the solid sample chamber. The outer wall of the nitrogen gas (innermost) chamber is sized and one end of the pipe is welded with the lower flange and the other end is closed with the same material. Similarly, for liquid nitrogen chamber, a pipe having the inner diameter of 20 mm larger than the outer diameter of the nitrogen gas chamber is sized and one end is welded with the lower flange i.e. next to the nitrogen gas chamber. The other end of the liquid nitrogen chamber is closed with the same material. Then for the outer chamber, namely vacuum chamber, the diameter of 180 mm and length 360 mm (thickness 1.4 mm) pipe is sized and is fixed as the outer vessel and also one end of the vessel is welded with the lower flange and other end is closed. An outlet provision is also made in the outer chamber to provide a better vacuum. In the solid sample region, the outer thick walled vessel is sized and one end of the vessel is closed with the same material. In the other end of the vessel, a "L" type step is made so as to clamp with the

connecting plate, which is connected with the connecting tube. The heating element is wound spirally on the copper vessel and the vessel is placed inside the thick walled outer vessel and is clamped with the connecting plate using binding screw. A novel spring loaded arrangement as herein above described was made and fixed on the upper disc of the solid sample holder to provide a gentle and uniform pressure between the solid sample and crystal. The crystal and the solid sample are placed on the solid sample holding stage, which is fixed with the lower disc of the solid sample holder and the two discs were held by the three threaded rods, which are attached co-centrically to the bottom of the lid plate. Care was taken to hold the crystal, solid sample and the spring loaded arrangement in a coaxial line. The signal cable for the crystal and for the sensors (positioned one at sample and the other at heater coil) were taken out through the connecting tube and the power supply for the heating element is provided using a separate pipe and this is placed adjacent to the connecting tube.
The received signals are analyzed with the help of Digital Storage Oscilloscope (DSO) to determine ultrasonic velocity and attenuation in the solid sample. Using the external Proportional Integral and Derivative (P.I.D.) controller arrangement, the necessary current is given to the heater coil, to warm up the temperature inside the sample region, if necessary.
Normally, the velocity and attenuation of ultrasonic waves in any solid sample can be determined by passing the ultrasonic waves into the sample. In the present invention, the pulse echo method is used to measure the velocity and attenuation of ultrasonic waves in solid samples. A gentle, and uniform pressure is applied to provide good contact and impedance matching between the crystal and solid sample. The block diagram of the experimental setup using the present invention to measure the velocity and attenuation in solid samples is shown in Fig.8 of the drawings accompanying this specification.
The technique used in the device of the present invention is to measure the velocity and attenuation of ultrasonic waves in solid samples is pulse echo method and it is

universally accepted by the most of the non-destructive testing (NDT) community. The following are the novelty and / or non-obvious inventive steps involved in the device of the present invention, which are different from the prior-art as depicted in Fig.3 of the drawings: i) Provision to use low solid sample thickness i.e. in the order of even 2 mm thickness ii) Provision to use either pulse echo method or through transmission technique iii) The required couplant can be used between the crystal and solid sample to provide good
coupling between the same
iv) A novel spring loaded arrangement provides a good contact, gentle and uniform pressure between the crystal and solid sample. This will also safeguard the crystal / solid sample without any damage / crack due to the non-uniform cooling, v) Any shape of the solid sample either rectangular or cylindrical with plane parallelism
between the opposite faces can be used for the velocity and attenuation measurements vi) The solid sample cooling / heating rate can be controlled, which results in the solid
sample / crystal being protected from rapid increase / decrease in temperature vii) Providing a thick walled vessel around the solid sample region, the transfer of
temperature to the sample chamber is being controlled as per the requirements. viii) Heating arrangement is also provided to heat the solid sample temperature, if necessary. The following example is given by way of illustration and therefore, should not be construed to limit the scope of the present invention:
Example-1
Transit time of longitudinal ultrasonic waves in glass sample. Thickness of the solid sample = 4.9 mm

(Table Remove)
The same is represented in the form of graph as shown in Fig.9 of the drawings.
From the above results, pulse echo method determines well the change in ultrasonic velocities on solid sample with change in temperature. The present device can be used with solid sample of different thickness i.e. from mm to cm range. The main advantages of the present invention are
a. One can measure the ultrasonic velocity and attenuation of solid samples having
thickness mm to cm range.
b. The novel spring loaded arrangement provides a gentle and uniform pressure, and
good contact between the solid sample and crystal.
c. One can use either pulse echo method or through transmission technique.
d. The cooling and heating rate of temperature is controlled depending on the
requirements.
e. Heating arrangement is also provided to warm up the solid sample region, if
necessary.
f. Provides ease of transfer of temperature from liquid nitrogen region to sample region
by way of an inert (nitrogen) gas being used in the vessel, which is in between the
sample and liquid nitrogen chamber.




We claim:
1. A device for the measurement of ultrasonic velocity and attenuation in solid sample at
low temperatures, which comprises a cryostat, such as herein described, essentially
consisting of a solid test sample chamber (8,28) having a scalable (15) lid plate (9),
characterized in that the bottom of the said lid (9) being provided with at least three
removably fixed vertical stainless steel tubes (40) enclosing removably fixed coaxially
placed vertical stainless steel threaded rods (41) protruding beyond the bottom of the said
tubes (40) in such a manner so as to hold a disc (32) by means such as non-metallic bush
and stainless steel nut (31), the said disc (32) being provided with a concentrically placed
removably fixed test sample (1) holding stage (30), the said tubes (40) being provided at
the middle level with an annular disc (36) slidable by means (37) such as non-metallic
bush, the concentric annular opening of the said annular disc (36) being provided with
fixed vertical bell shaped outer receptacle (44) having a concentric internally threaded
hole at the top, the said hole having a matching threaded vertical screw (43) fixed to the
top of a bell shaped inner receptacle (45) placed vertically and concentrically inside the
said outer receptacle (44), the said inner receptacle (45) being provided with a
concentrically and coaxially placed low tension spring (46) fixed to the top end of a light
weight vertical tube (47) having a non-metallic bush-pad (35) fixed to the bottom end in
such a manner as to be able to provide pressure contact between a PZT crystal (4)
interfaced with couplant (48) to test sample (1) placed on holding stage (30), the said
vertical tubes (40), discs (32,36) being enclosed in a copper vessel (29) removably fixed
by means (42) such as screw to the bottom of the said lid (9).
2. A device as claimed in claim 1, wherein the copper vessel (29) enclosing the test sample
holder is provided on the outer peripheral surface with heating means (38) such as a
heater coil.

3. A device as claimed in claim 1-2, wherein temperature sensors (33, 34) are provided
proximally to the copper vessel (29) surface and test sample (1).
4. A device as claimed in claim 1-3, wherein the test sample chamber (8) is enclosed in a
nitrogen gas chamber (7) which is enclosed in a liquid nitrogen chamber (6) which is
further enclosed in an outer double walled vacuum chamber (5).
5. A device as claimed in claim 1-4, wherein the PZT crystal (4), temperature sensors
(33,34) and heater coil (38) are connected to ultrasonic pulser / receiver, temperature
controller and power supply, respectively.
6. A device as claimed in claim 1-5, wherein the device is connected to a digital storage
oscilloscope and a personal computer through conventional interfaces.
7. A device for the measurement of ultrasonic velocity and attenuation in solid sample at
low temperatures substantially as herein described with reference to the example and
figures 5 to 9 of the drawings accompanying this specification.

Documents:

14-del-2002-abstract.pdf

14-del-2002-claims.pdf

14-del-2002-correspondence-others.pdf

14-del-2002-correspondence-po.pdf

14-del-2002-description (complete).pdf

14-del-2002-drawings.pdf

14-DEL-2002-Form-1.pdf

14-del-2002-form-18.pdf

14-del-2002-form-2.pdf

14-DEL-2002-Form-3.pdf


Patent Number 236828
Indian Patent Application Number 14/DEL/2002
PG Journal Number 49/2009
Publication Date 04-Dec-2009
Grant Date 24-Nov-2009
Date of Filing 10-Jan-2002
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 PHYSICS, MEPCO SCHLENK ENGINEERING COLLEGE, MEPCO ENGINEERING COLLEGE (PO)-626 005, VIRUDHUNAGAR (DT), TAMILNADU, INDIA.
2 NALLAIYAN PALANIVELU SENIOR RESEARCH FELLOW, DEPARTMENT OF PHYSICS, MEPCO SCHLENK ENGINEERING COLLEGE,MEPCO ENGINEERING COLLEGE (PO)-626 005, VIRUDHUNAGAR (DT), TAMILNADU, INDIA.
3 BIJAY KRISHNA CHAUDHURI HEAD, SOLID STATE PHYSICS DEPARTMENT, INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE, JADAVPUR, CALCUTTA-700 032, INDIA.
PCT International Classification Number G01F1/66
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA