Claims:WE CLAIM:
1. A pulse velocimetry system (400) for inspection of submerged concrete structures, the system (400) comprising
a transducer alignment and positioning module (100) configured to communicate with a pulse receiver and data acquisition module (200), the pulse receiver and data acquisition module (200) configured to communicate with a data analysis and transmission module (250) that transfers data received from the pulse receiver and data acquisition module (200) to a data analysis and interpretation module (300), the transducer alignment and positioning module (100) having
a slider mechanism (110);
a plurality of alignment unit (120) slidably positioned in the slider mechanism (110); and
at least one probe (130) positioned in each alignment unit (120), at least one probe (130) acts a transmitter and at least one probe (130) acts as a receiver, the alignment unit (120) adapted to self-align one probe (130) positioned in one alignment unit (120) with respect to the probe (130) positioned in other alignment unit (120) and with respect to a target surface (150).
2. The pulse velocimetry system as claimed in claim 1, wherein the alignment unit (120) includes a plurality of alignment pins (126) positioned on an outer surface of a probe mount (125).

3. The pulse velocimetry system as claimed in claim 1, wherein the alignment unit (120) includes a plurality of adjustment pins (128) positioned through the probe mount (125).

4. The pulse velocimetry system as claimed in claim 1, wherein the probe (130) is provided with a shock absorbing protection sleeve (132) at the front portion thereof.

5. The pulse velocimetry system as claimed in claim 1, wherein a plurality of probes (502) is placed on a motion controllable scanner (500) with motors and encoders (506).

6. The pulse velocimetry system as claimed in claim 1, wherein the slider mechanism (110) includes a support structure (111) having a lead screw (112) or a guide rail (112) placed thereon; and

at least one probe (130) positioned on the guide rail or the lead screw (112).

7. A method for inspection of submerged concrete structures using the pulse velocimetry system as claimed in claims 1-6, the method comprising the steps of:
positioning a pulse velocimetry module (100) in near proximity of a target structure (150);
aligning one alignment unit (120) positioned on a sliding mechanism (110) with respect to other alignment unit (120);
aligning one probe (130) placed on a probe mount (125) of each alignment unit (120) with respect to other probe (130) placed on a probe mount (125) of each alignment unit (120) in predefined configuration with the target structure (150);
measuring a distance (L) between two probes (130);
passing the ultrasonic waves generated by at least one probe (130) through the target structure (150);
recording a time (t) required for receiving the ultrasonic wave by at least one other probe (130);
transferring the reading to a pulse receiver and data acquisition module (200) through a data and power transmission module (250);
transferring the data to data analysis and interpretation module (300); and
analyzing the readings by the data analysis and interpretation module (300).

8. The method as claimed in claim 7, wherein the step of analyzing includes measuring a velocity (v) of ultrasonic wave by calculation of the time (t) and the distance (L).

9. The method as claimed in claim 7, wherein at least one probe (130) acts a transmitter and at least one probe (130) acts as a receiver.

10. The method as claimed in claims 7 or 9, wherein the at least one probe (130) is placed on one surface of the target structure (150) perpendicular to at least one another probe (130) placed on other surface of the target structure (150).

11. The method as claimed in claims 7 or 9, wherein both the probe (130) are placed on the same surface of the target structure (150).

Dated this 11th day of January, 2021

For PLANYS TECHNOLOGIES PRIVATE LIMITED
By their Agent

(D. MANOJ KUMAR) (IN/PA 2110)
KRISHNA & SAURASTRI ASSOCIATES LLP

, Description:FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[SEE SECTION 10, RULE 13];

ULTRASONIC PULSE VELOCIMETRY SYSTEM FOR INSPECTION OF SUBMERGED CONCRETE STRUCTURES & METHOD THEREFOR;

PLANYS TECHNOLOGIES PVT. LTD., A COMPANY REGISTERED UNDER THE COMPANIES ACT, HAVING ADDRESS NO. 5, BALAJI NAGAR MAIN ROAD, JAYA NAGAR EXT., PUZHUTHIVAKAM, CHENNAI – 600091, TAMIL NADU, INDIA;

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

TECHNICAL FIELD OF THE INVENTION
The present invention relates to inspection of submerged concrete structures, and particularly to an ultrasonic pulse velocimetry system for inspection of submerged concrete structures and method therefor.
BACKGROUND OF THE INVENTION
Structures constructed below the water surface need periodic inspection to assess integrity in order to prevent catastrophic damages affecting lives or causing unscheduled maintenance activities. Inspection schedules are also made mandatory through regional regulations. Underwater structures may get damaged by various factors such as defects in the manufacturing stage, seismic variations, corrosion, and ocean current/wave action. There are several types of inspection method available in literature including visual, ultrasonic, eddy current and X-ray based inspections.
In view of this, for underwater operation of concrete structures, visual inspection is one of the methodologies used till date in the industry to assess structural integrity. However, visual inspection can only provide a qualitative indicator to structural integrity. The systems and techniques available in the current state of the art fail to inspect defects and flaws present inside the submerged concrete structure. There is high risk in depending on the results obtained by visual inspections as such techniques are not capable of inspection of internal defects of the structures. If the defects, damage or flaws present inside the concrete structures are not identified at the right time, there is risk of collapsing the structure manufactures below and above the water level.
Further, among various ultrasonic methods, ultrasonic testing and ultrasonic pulse velocimetry (UPV) has been used from early 1960s to detect defects, quantify uniformity and measure ultrasonic pulse velocity in concrete structures. Accuracy in recording the readings is the most important factor for qualitative inspection. The techniques and mechanism available in current state of art fail to provide accuracy necessary for recording the readings due to improper alignment of inspecting mediums such as transducers. Repetitive inspection may cause destruction of the concrete structures.
Therefore, there is a need for accurate non-destructive technique for inspection of underwater concrete structures.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a pulse velocimetry system for inspection of submerged concrete structures. The system includes a transducer alignment and positioning module configured to communicate with a pulse receiver and data acquisition module. The pulse receiver and data acquisition module is configured to communicate with a data analysis and transmission module that transfers data received from the pulse receiver and data acquisition module to a data analysis and interpretation module. The transducer alignment and positioning module includes a slider mechanism. A plurality of alignment unit is slidably positioned in the slider mechanism. At least one probe is positioned in each alignment unit. At least one probe acts a transmitter and at least one probe acts as a receiver. The alignment unit is adapted to self-align one probe positioned in one alignment unit with respect to the probe positioned in another alignment unit and with respect to a target surface. The alignment unit includes a plurality of alignment pins positioned on an outer surface of a probe mount. The alignment unit includes a plurality of adjustment pins positioned through the probe mount. The probe is provided with a shock absorbing protection sleeve at the front portion thereof. In an embodiment, a plurality of probes is placed on a motion controllable scanner with motors and encoders. The slider mechanism includes a support structure having a lead screw or the guide rail placed thereon. At least one probe is positioned on the guide rail or the lead screw.
In another aspect, the present invention provides a method for inspection of submerged concrete structures using the pulse velocimetry system. In a first step, a pulse velocimetry module is positioned in near proximity of a target structure. In the next step, one alignment unit positioned on a sliding mechanism is aligned with respect to other alignment unit. In the next step, a probe placed on a probe mount of each alignment unit is aligned with respect to a probe placed on a probe mount of each alignment unit in predefined configuration with the target structure. At least one probe acts a transmitter and at least one probe acts as a receiver. In the next step, a distance between two probes is measured. In the next step, the ultrasonic waves generated by at least one probe is passed through the target structure. In the next step, a time required for receiving the ultrasonic wave by at least one other probe is recorded. In the next step, the reading is transferred to a pulse receiver and data acquisition module through a data and power transmission module. In the next step, the data is transferred to data analysis and interpretation module. In the last step, the readings are analyzed by the data analysis and interpretation module. The step of analyzing includes measuring a velocity of ultrasonic wave by calculation of the time and the distance. Then, at least one probe is placed on one surface of the target structure perpendicular to at least one probe placed on other surface of the target structure. In an embodiment, both the probes are placed on the same surface of the target structure.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows schematic diagram of an ultrasonic inspection of submerged concrete structures in accordance with an embodiment of the present invention of the present invention;
FIG. 2 shows a system of transducer alignment and positioning module of the system of FIG. 1;
FIG. 3 is a side view of a module of FIG. 2 aligned to the target object;
FIGS. 4 (a-c) show different configurations of a slider mechanism of the system of FIG. 1;
FIG. 5 shows an another embodiment of the system of the present invention;
FIG. 6 is a schematic illustrating the modes of estimating the ultrasonic pulse velocity (UPV) using system of FIG. 1;
FIG. 7 shows an illustration of the A, B and C-scan modalities of data representation; and
FIG. 8 shows a pulse receiver and data acquisition module of the system of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION
Although specific terms are used in the following description for sake of clarity, these terms are intended to refer only to particular structure of the invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention.
References in the specification to “one embodiment” or “an embodiment” mean that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
In general aspect, the present invention relates to a modular and compact pulse velocimetry ultrasonic testing (NDT) system for inspection of underwater concrete structures. The invention is to be used as an appendage which may be attached to any remotely operated platform used to perform NDT of the structure of interest. The analysis of condition of the structure is based on the data measured by the transducers and the velocity of ultrasonic wave passed through the structure.
The system of the present invention contains the following parts,
• Ultrasonic transducers
• Pulser-receiver and data acquisition module
• Data and power transmission module
• Data analysis and interpretation module
• Transducer alignment and positioning module
The ultrasonic transducers generate the ultrasonic energy used to inspect the structure of interest. The ultrasonic transducers are supplied with modulated power by the pulser-receiver and the data is recorded digitally by the data acquisition module. Data and power for the pulser-receiver and data acquisition module is provided from the underwater robotic platform or divers through the data and power transmission module. The data analysis and interpretation module performs the necessary calculations to enable simpler data interpretation to the end-user. Further, the transducer alignment and positioning module is key in enabling obtain high measuring high quality of data from the transducers since any NDT system operating underwater is influenced by distortions by underwater currents and inherent system noise, and other factors including accessibility, type and thickness of marine growth.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures.
Referring to FIG. 1, an ultrasonic pulse velocimetry system (400) in accordance with an embodiment is shown. The system (400) includes a transducer alignment and positioning module (100) configured to communicate with a pulse receiver and data acquisition module (200). The pulse receiver and data acquisition module (200) is configured to communicate with a data analysis and transmission module (250) that transfers data received from the pulse receiver and data acquisition module (200) to a data analysis and interpretation module (300).
Referring to FIGS. 2 and 3, the transducer alignment and positioning module (100) in accordance with an embodiment is shown. The transducer alignment and positioning module (100) includes a slider mechanism (110) positioned on an underwater robotic unit (111). The slider mechanism (110) has a plurality of alignment unit (120) slidably positioned thereon. The alignment unit (120) have at least one marine ultrasonic transducer (130) mounted thereon. The alignment unit (120) ensures alignment of the marine grade ultrasonic transducers (130), also known as probes (130) against a target surface (150). The alignment unit (120) also adjusts a relative position of the probes (130) with each other to vary the distance between the probes (130) to obtain optimum results. It is to be noted here that at least one probe (130) positioned in each alignment unit (120), at least one probe (130) acts a transmitter and at least one probe (130) acts as a receiver, the alignment unit (120) adapted to self-align one probe (130) positioned in one alignment unit (120) with respect to the probe (130) positioned in other alignment unit (120) and with respect to a target surface (150).
The alignment unit (120) also compensates for any misalignment of the entire system (100) which may be caused by a variation of factors including control of the robotic platform, environmental conditions, and surface conditions of the specimen of interest. It is to be noted here that the alignment unit (120) is self-aligned. There is no powered means is used to align the probes (130) to the target surface (150). However, it is understood here that powered means of control; either remote controlled or autonomous control may be implemented in alternative embodiments of the present invention.
In accordance with an embodiment, the alignment unit (120) includes at least one holder (122) mounted therewith with a suitable sliding arrangement. The holder (122) is a cup shaped frame. The holder (122) has a support plate (124) fixed at inner side thereof. The support plate (124) includes a probe mount (125) positioned thereon with a suitable connecting means. The probe mount (125) holds the probe (130). The probe mount (125) is equipped with a plurality of alignment pins (126) and a plurality of adjustment pins (128).
The alignment pins (126) are positioned on the outer surface of the probe mount (125). The alignment pins (126) allow the probe (130) to align with the target surface (150) with an adjustable stand-off distance. The alignment pins (126) maintain a constant stand-off distance and additionally, serve to penetrate the light marine growth on the target surface (150) to provide slight adhesion which has been found to assist in alignment and stability. The alignment pins (126) may have different materials, sizes and shapes depending on the end use.
The adjustment pins (128) are inserted through the probe mount (125) at predefined locations. In an embodiment, there are three adjustment pins (128) positioned on three jaws of the probe mount (125). However, it is understood here that number of adjustment pins (128) may vary in alternative embodiments of the present invention. The adjustment pins (128) are used for clamping the probe (130) in the probe mount (125) by adjusting the jaws of the probe mount (125). The adjustment pins (128) facilitate use of probes having different diameter, uneven surfaces and lengths.
The probe (130) is positioned in the probe mount (125) and clamped with the adjustment pins (128). In an embodiment, the probe (130) is provided with a shock absorbing protection sleeve (132) at the front portion of the probe (130). The shock absorbing protection sleeve (132) protects the probe (130) against damages from impact against the target surface (150) of inspection.
In accordance with an embodiment of the present invention, a camera is positioned on a carrier provided with either a diver or an underwater drone or a similar vehicle. It is to be noted here that the camera is to be positioned such that the image captures the two probes in a single frame. The signal transmission and the receiver module (200) may also be positioned on the carrier. Similar provisions can be made to mount them on the present and alternative embodiment.
It is to be noted here that the data acquired is very sensitive to the alignment of the probes (130) with respect to the surface (150) of interest. Misalignment can be caused from placing the probes (130) on uneven or corroded surfaces. Further, surfaces covered with marine growth can also pose challenges. It is also not desirable to place the probes (130) face directly on the surface of interest to prevent wear and tear. The alignment unit (120) along with the alignment pins (126) allows the probes (130) to align with the target surface (150) with an adjustable stand-off distance. The alignment units (120) also compensate for any misalignment of the entire system (100) which may be caused by a variation of factors including control of the robotic platform, environmental conditions, and surface conditions of the specimen of interest. The present embodiment mounted on a robotic platform is shown in Fig. 8.
Referring to FIGS. 4A-4C, different configurations of the slider mechanism (110) of the ultrasonic pulse velocimetry system (100) is shown. The slider mechanism (110) includes a lead screw (112) or a guide rail (112) mounted on a support structure (111). The support structure (111) may have various shapes such as linear, circular, square, rectangular, cylindrical and the like. The lead screw (112) or the guide rail (112) have at least one probe (130) mounted thereon with suitable arrangement thereon. The movement of probe (130) is facilitated by a motor /drive (113) positioned with the guide rail (112) or the lead screw (112).
Referring to FIG. 5, another embodiment of the system (500) of the present invention is shown. The system (500) includes a plurality of marine transducers or probes (502) placed on the motion controllable scanner (500) with motors and encoders (506). The number of probes (502) in each row may vary depending upon the required speed of the data acquisition process, resolution and penetration of ultrasonic energy which are determined by the application of interest. It is noteworthy to state that there are limits on the type and the dimensions of marine growth which are dependent on the frequency and type of the probes (502) used. Also, protection for the probes (502), in the form of flexible sleeves (506) may also be provided in the front portion of the probe (502) to protect it against damages from impacts that commonly occur during usage with a carrier such as a remotely operated vehicle. This leaves the probe (502) with a small standoff distance between the target surface (150) of inspection and itself. The standoff distances are factored into the calculations and in the generation of the report following performing NDT of the structure. In this one embodiment, a feedback mechanism is in-built in the motor and encoder (506) system, through which the exact position between the probes (130) is known.
In accordance with the present invention, to calculate the distance between the probes (502), the plurality of marine probes (502), either one probe or a group of probes (502) are chosen to be the excitation/ transmitter element and the other probe (502) are used in the receiver mode. The distances are calculated with reference to the transmitter probe (502), i.e., if total of 3 probes are used, with the first one being the transmitter, then, the distance of probes two and three are measured with respect to their distance from the first probe/ transmitter probe (502).
In operation, referring to FIGS. 1 to 8, in operation, the ultrasonic pulse velocimetry system (400) is positioned in near proximity of a target structure (150). In next step, one alignment unit (120) positioned on the sliding mechanism (110) is aligned with respect to other alignment unit (120). In the next step, the probe (130) placed on a probe mount (125) of each alignment unit (120) is aligned with respect to the target structure (150). In the next step, a distance (L) between two probes (130) is measured. In the next step, the ultrasonic waves generated by at least one probe (130) acting as a transmitter are passed from one probe (130) to at least one other probe (130) through the target structure (150). In the next step, a time (t) required for receiving the ultrasonic wave by the other probe (130) acting as a receiver is recorded. The recordings are transferred to the pulse receiver and data acquisition module (200) which powers the probes (130). The pulse receiver and data acquisition module (200) receives the analog data and stores the same in a digital form. In accordance with an embodiment, the data is transmitted from the probes (130) to the pulse receiver and data acquisition module (200), and then to the data analysis and interpretation module (300) via the data and power transmission module (250). The data and power transmission module (250) includes underwater cables and special underwater connectors for transmission of data and power to all elements of the system (400).
In the next step, the data stored in pulse receiver and data acquisition module (200) is transferred to the data analysis and interpretation module (300) that analyses the condition of the structure by calculation of velocity of transmission of the ultrasonic wave between two probes (130) i.e transmitter and receiver probes (130). The calculation and analysis are performed by the data analysis and interpretation module (300). It is understood here that as the number of transducers/ probes increase, the complexity of analysis performed increases.
In accordance with the present invention, the distance between the probe (130) and the target surface (150) is variable and is selected on the basis of factors including the thickness & type of the marine growth, input power, corrosion products or any protrusions on the target surface (150) which might affect the quality of the measurement or damage the probe/ transducer (130) itself. In general, the distance between the target surface (150) and the probe (130) that is the standoff distance ranges between of 5-50 mm.
Referring to FIG. 6, the probes (130) mounted on the alignment unit (120) are positioned in different configurations on the target structure (150). At least one probe (130) act as a transmitter (T) and at last one probe (130) act as a receiver (R) of ultrasonic waves from the target surface (150). The time record of the received signal is referred to as an A-scan as shown in FIG 7. Three configurations shown in FIG. 6 are used to estimate the ultrasonic pulse velocity according to the accessibility of the surfaces, viz., direct, semi-direct and indirect methods. In the direct method, the probes (130) are placed on opposite surfaces. In the semidirect method, the at least one probe (130) is placed on one surface of the target structure (150) perpendicular to at least one other probe (130) placed on other surface o the target structure (150). In indirect method, the both the probe (130) are placed on the same surface of the target structure (150). Table 1 shows grading of concrete on the basis of the estimated ultrasonic pulse velocity using the direct mode (A), conventionally used in the industry.
Pulse velocity (m/s) in direct mode Concrete Quality Grading
Above 4500 Excellent
3500 – 4500 Good
3000 – 3500 Medium
Less than 3000 Doubtful

Table 1
Ultrasonic waves generated by the one probe (130) acting as a transmitter travel through the structures of the target structure (150) or structures to be inspected and are received by the other probe (130) acting as a receiver, thereby measuring the time of arrival. Therefore, with the knowledge of the distance between the two probes (130) (L) and the time of arrival of the generated wave (t), the velocity of sound/ ultrasonic wave (v), in the medium is calculated as v = L/t. Based on the velocity of sound in the medium estimated, a rough classification, shown in Table 1, as an indicator of concrete quality is used to decide if further investigation is required at the region of interest.
Referring to FIG. 7, a schematic representation of scan modalities of data collected and interpreted by the data analysis and interpretation module (300) is shown. A scan collects 2-dimensional representation of the structure’s depth cross section. A scan is a graphical representation of time Vs amplitude. B-scan collects 3- dimensional representation of the structure’s cross section. B scan collects A-scans in one axis i.e a collection of time Vs amplitude when the probes (130) moves along one (vertical) line. B and C-scan allow easy interpretation of the internal state of the specimen from the data collected during the inspection process. C-scan collects B-scan. The entire surface can be visualized as an image that facilitates rapid interpretation of structural integrity or presence of the defects.
It is to be noted here that the plurality of probes (130) can significantly improve the system (100) capacity to allow faster data collection and the use of numerous advanced techniques to improve resolution and penetration including synthetic aperture focusing, total focusing method and full matrix capture. The system (400) of the present invention is mobile and can be carried by a remotely operated vehicle or a diver or equivalent carrier.
The system (100) of the present invention facilitates generation of a velocity map of the target surface which can detect non-uniformities and surface breaking defects in one of the modalities of inspection. In another embodiment described herein the system of the present invention can generate two-dimensional and three-dimensional scan images (B and C-scans) to detect major defects including delaminations, voids and honey combings in another modality of inspection. The system of the present invention performs NDT on uneven concrete surfaces and stable NDT operation in underwater currents. The system of the present invention also enables remote data acquisition that facilitates control of the system from a safe location above the water surface mitigating the risks to the personnel involved in a conventional diver-based operation.
The embodiments of the invention shown and discussed herein are merely illustrative of modes of application of the present invention. Reference to details in this discussion is not intended to limit the scope of the claims to these details, or to the figures used to illustrate the invention.
It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the scope of the present invention.