DESC:FIELD OF THE INVENTION
The present invention relates generally to an apparatus for inspection of concrete structures and, in particular, to a rebound hammer which measures the hardness of underwater concrete structures such as dams, bridges, ports, concrete coated pipelines and the like.
BACKGROUND OF THE INVENTION
Owing to various factors including defects in the manufacturing stage, seismic variations, corrosion, and current action, underwater structures are subjected to significant damage and deterioration, often to a greater extent than above ground structures. For concrete structures operating underwater, for example, dams, bridges, ports, and concrete coated pipelines, the only methodology commercially available, till date to qualitatively study the structural integrity is visual inspection and use of thickness measuring gauges with the help of professional divers. Therefore, there is paramount interest to develop quantitative nondestructive testing (NDT) in addition to existing qualitative methodologies of inspection for underwater structures.
Nondestructive testing (NDT) of concrete structures is conventionally performed on concrete structures for both, new structures and existing structures, to follow statutory norms, to understand the quality of construction, to predict its remaining life and prevent any catastrophic failures. Conventionally, the Schmidt hammer, also known as the rebound hammer is widely used for evaluation of concrete quality owing to the low equipment cost and the ease of its use.

Conventionally, underwater inspection of structures is typically done by professional divers who reach the structure carrying the payloads including lights, cameras, and ultrasonic transducers. However, these divers are limited to operate within depths up to 30 to 40 meters. Further, there are risks involved in operations related to the environmental condition such as underwater currents, visibility and working in enclosed spaces. In order to improve the repeatability of the results and mitigate the risks involved, remotely operated vehicles (ROVs) are preferred in many underwater operations.
Currently there are no solutions/ patents available relating to a robotic platform based rebound hammer for underwater concrete structures. The closest solutions provided for underwater rebound hammer is in patent documents viz. KR101383766B1, KR101723531B1, JP2006349566A which describe different methodologies for hermetically sealing the Schmidt hammer for underwater application. This solution is used using a diver who carries this equipment and reaches the structure of interest. The diver places the rebound hammer perpendicular to the surface or change the setting in the instrument to automatically measure the angle of placement of the instrument with respect to the surface. Since diver is employed for measuring, a limitation of depth up to 30-40m is imposed.
Thus, a need therefore exists for a measuring apparatus which provides a long-sought solution to the problem of accurately measuring internal damage and deterioration to underwater concrete structures and the like.
OBJECTIVE OF THE INVENTION
These objectives are provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. These objectives are not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
An important objective of the invention aims at providing a compact solution for the shortcomings of the above-mentioned systems.
Another objective of the present invention is to provide a rebound hammer for remote robotic inspection of underwater concrete structures.
Yet another objective of the present invention is to measure rebound number using robotic platforms for underwater structures.
Further objective of the current invention is to provide a self-aligning mechanism which aligns the rebound hammer to the surface of interest.
Yet another objective of the current invention is to provide actuators to load the hammer mass to prepare for the surface impact.
Another objective of the current invention is to acquire data from a safe location.
Object of the present invention is not limited to the above-mentioned problem. Other technical problems that are not mentioned will become apparent to those skilled in the art from the following description.
SUMMARY OF THE INVENTION
According to an aspect of the invention, a rebound hammer for remote robotic inspection of underwater concrete structures is disclosed. The rebound hammer is mounted on a remotely operated vehicle (ROV) and operated underwater from a command station. The said rebound hammer comprises an enclosure that encloses a spring driven mass mounted on a guide rod, wherein the mass slides on a guide rod within the enclosure. A plunger housed inside a plunger guide is connected to the free end of the mass wherein said plunger performs a hammering movement by reciprocating in the longitudinal direction within the enclosure. Further, the hammer comprises an actuator disposed at the tip end region of the enclosure and is employed to load the springs to perform a predetermined hammering operation on the surface of underwater concrete structure by reciprocating in its axial direction. A scale is mounted inside the enclosure having marks of rebound numbers. When the actuator releases the spring driven mass from a locked position causes mass to impact plunger which performs hammering on the surface of the concrete structure and transfers energy to the surface such that the plunger reacts and re-transmits the rebound energy to the mass causing the mass to slide along the guide rod towards the rear portion of the enclosure wherein the rebound is measured on the scale by taking the reference position of mass in the form of a rebound number to measure the hardness.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawing, illustrating by way of example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in greater detail with reference to an embodiment which is illustrated in the drawing figures:
Figure 1 shows a robotic underwater rebound hammer with ancillary systems, according to an embodiment of the present invention;
Figure 2 shows functional connectivity of the rebound hammer with the ancillary systems, according to an embodiment of the present invention; and
Figure 3 shows a flowchart explaining the process of acquiring data underwater using an underwater robotic platform, according to an embodiment of the present invention.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.
DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
Rebound hammer is an apparatus used to measure the hardness of concrete structures and is based on the principle that the rebound of an elastic mass is a function of the hardness of the surface against which the mass impinges. In many cases, the energy absorbed by the concrete is empirically related to its strength. The methodology of inspection begins with the selection and preparation of the concrete surface to be tested. A known amount of energy is applied by impinging the hammer loaded by a spring of known stiffness against the test surface and the rebound is measured and translated into the rebound number. The angle of the plunger to the surface affects the results obtained and may require suitable corrections.
Referring to Figure 1, a robotic underwater rebound hammer with ancillary systems, according to an embodiment of the present invention is shown. The underwater rebound hammer (100) comprises an enclosure (108) that encloses a mass (102) driven by a spring (104) such that the mass (102) slides on a guide rod within the enclosure to carry out test on an underwater concrete structure (126). The enclosure (108) is a watertight enclosure (108) that prevents entry of water therein. A plunger (124) housed inside a plunger guide (106) is connected to a free end of the mass (102) wherein said plunger (124) performs a hammering movement by reciprocating in the longitudinal direction within the enclosure (108). The plunger (124) which passes through a plunger guide (106) is pressed firmly against a surface (122) of the concrete structure (126) during the test. The hammer (100) comprises an actuator (112) disposed at a tip end region of the enclosure (108). The actuator (112) is employed to load the springs (104) to perform a predetermined hammering operation on the surface (122) of the underwater concrete structure (126) by reciprocating in its axial direction. A scale is mounted inside the enclosure and has marks of rebound numbers to measure hardness. When the actuator (112) releases the spring (104) driven mass (102) from a locked position causes said mass (102) to impact plunger (124) which performs hammering on the surface (122) and transfers energy to the surface (122) during the test. The plunger (124) reacts and re-transmits the rebound energy to the mass (102) thereby causing the mass (102) to slide along the guide rod towards the rear portion of the enclosure (108). The rebound is measured on the scale and measured in terms of rebound number. The harder and more compact the concrete structure the greater rebound of spring driven mass with the maximum rebound of mass being indicative of the hardness of the concrete structure under test.
The robotic underwater rebound hammer (100) includes ancillary systems like a LASER targeting system (110), an alignment system (114), an accelerometer (116), position and control system, a sensor (118), and a data acquisition and transfer system (120). The LASER targeting system (110) has a LASER source that emits light on a target region to visually position and observe the impact of the plunger (124) on the surface (122) by the pilot. The LASER source can emit light through a process of optical amplification. Additionally, an alignment mechanism (114) is attached to the rebound hammer to enable the required inclination to the surface. Further, the enclosure (108) is provided with the accelerometer (116) to measure the inclination of the rebound hammer with respect to the underwater concrete structure (126).
The actuator (112) with position and control system has a controller and a position sensor used to draw feedback from the actuator for the ROV pilot to see the status of compression of the rebound hammer against the surface. Following the impact of the rebound hammer on the surface, the rebound is absorbed, primarily by the actuator system. Any remaining rebound force is absorbed by the robotic platforms thruster systems which help maintain its position.
The sensors (118) according to an embodiment of the present invention are electronic sensors employed for processing and conversion of the mechanically obtained rebound number into digital data to be transferred to the robotic platform. The data acquisition and transfer system (120) functions to collect the digital data from the rebound hammer and transmits to the pilot team in the command station. The data acquired by the rebound hammer is also position-tagged for repeatability using an underwater positioning system. Corresponding figure 2 shows functional connectivity of the rebound hammer with the ancillary systems, according to an embodiment of the present invention.
The rebound hammer (100) along with the ancillary systems is positioned on a remotely operated vehicle (ROV) (130) which is operated underwater from the command station. The ROV (130) carries high-definition camera modules using which the rebound hammer and the surface of interest underwater can be viewed in real-time. The underwater rebound hammer (100) carrying ROV (130), is also integrated with an underwater positioning system (128). The underwater positioning system (128) is used to sample to the data points as subjected by the industrial standards. The robotic underwater rebound hammer is provided with plurality of connectors providing power and data to hammer for data acquisition and transfer to and from the command station.
Figure 3 shows a flowchart explaining the process of acquiring rebound number using a rebound hammer, according to an embodiment of the present invention. The process (200) includes underwater LASER targeting of the region of interest (202) by a ROV pilot, while setting the target region, the coordinates of the target region is geotagged (204) to ensure evenly spaced measurements using an underwater positioning system. In the next step, the rebound hammer is positioned perpendicular to the surface of the concrete structure (206) using the alignment system. The accelerometer is used for measuring the inclination of the rebound hammer (210). In the further step, the actuator system is used to load the rebound hammer (208) to carry out the test, wherein the plunger is pressed firmly against the surface of the concrete structure under test. This releases the mass driven by the spring from a locked position thereby causing the mass to impact plunger which transfers energy to the surface of the concrete structure under test. Plunger reacts and re-transmits the rebound energy to mass causing said mass to slide along guide rod towards the rear portion of enclosure. The rebound is measured on the scale in the form of rebound number (212) which is later converted to a digital value (214). The digital data is acquired by the pilot team (216) in the command station for further processing to find out the hardness value of the concrete structure. The data can be processed either underwater on the system or at the command station. These steps can be repeated moving and aligning the rebound hammer at different target regions (218) using the underwater positioning system (128) underwater.
The rebound hammer attached remotely operated vehicle (ROV) can be used for different structures including rocks, mortar and fresh concrete by changing the appropriate impact energy as dictated by the standards in the region.
The rebound hammer attached to ROV provides various advantages including but not limited to, operating under any depth of operation unlike diver based underwater inspection solutions, provides virtually unlimited endurance – attractive from the point of view of reducing downtime in time-critical applications including dams, power generating units, bridges, and ports, and also, the usage on robotic platforms enables safe use in turbid waters, enclosed spaces and dangerous underwater currents.
In the above detailed description, reference is made to the accompanying drawings that form a part thereof, and illustrate the best mode presently contemplated for carrying out the invention. However, such description should not be considered as any limitation of scope of the present unit. The structure thus conceived in the present description is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit. The embodiments shown herein are only exemplary. And further embodiments are possible within the scope of the invention.
,CLAIMS:
1. A rebound hammer (100) for remote robotic inspection of underwater concrete structures (126), the rebound hammer (100) being mounted on a remotely operated vehicle (ROV) (130) and operated underwater from a command station, the rebound hammer comprising of:
an enclosure (108) enclosing a mass (102) driven by a spring (104) mounted on a guide rod, the mass (102) configured to slide on the guide rod within the enclosure (108);
a plunger (124) housed inside a plunger guide (106), the plunger (124) connecting to a free end of the mass (102), the plunger (124) configured to perform a hammering movement by reciprocating in a longitudinal direction within the enclosure (108);
an actuator (112) disposed at a tip end region of the enclosure (108) is employed to load the springs (104) to perform a predetermined hammering operation on the surface (122) of underwater concrete structure (126) by reciprocating in its axial direction; and
a scale mounted inside the enclosure (108) having marks of rebound numbers defined thereon,
wherein, the actuator (112) releases the spring (104) driven mass (102) from a locked position to cause said mass (102) to impact plunger (124) which performs hammering on the surface (122) of the concrete structure (126) and transfers energy to the surface (122) ,the plunger (124) reacts and re-transmits the rebound energy to the mass (102) causing the mass (102) to slide along the guide rod towards the rear portion of the enclosure (108) such that by taking the reference position of mass (102) the rebound is measured on the scale in the form of a rebound number to measure the hardness.
2. The rebound hammer (100) as claimed in claim 1, further comprises a position and control system having a controller and a position sensor employed to draw feedback from the actuator (112) for a pilot to see the status of compression of the rebound hammer (100) against the surface (122).
3. The rebound hammer (100) as claimed in claim 1, further comprises an alignment mechanism (114) attached to the rebound hammer (100) to enable inclination to the surface (122).
4. The rebound hammer (100) as claimed in claim 1, further comprises a LASER targeting system (110) having a LASER source emitting light on a target region to visually position and observe the plunger (124) impact on the surface (122) by the pilot.
5. The rebound hammer (100) as claimed in claim 1, wherein the enclosure (108) is provided with an accelerometer (116) to measure the inclination of the rebound hammer (100) with respect to the underwater concrete structure (126).
6. The rebound hammer (100) as claimed in claim 1, further comprises a sensor (118), the sensor is an electronic sensor employed for processing and conversion of mechanically obtained rebound number into digital data.
7. The rebound hammer (100) as claimed in claim 6, further comprises a data acquisition and transfer system (120) to collect the digital data from the rebound hammer and transmit to the pilot team in the command station.
8. The rebound hammer (100) as claimed in claim 1, wherein the data acquired by the rebound hammer (100) is position-tagged for repeatability by an underwater positioning system (128).
9. The rebound hammer (100) as claimed in claim 1, further comprises plurality of connectors for providing power and data to the rebound hammer for data acquisition and transfer to and from the command station.
10. The rebound hammer (100) as claimed in claim 1, wherein the harder and more compact the concrete structure the greater rebound of spring driven mass with the maximum rebound of mass being indicative of the hardness of the concrete structure.
11. A method (200) of acquiring a rebound number underwater with a rebound hammer, comprising the steps of:
facilitating underwater LASER targeting (202) of the region of interest by a ROV pilot, while setting the target region the coordinates of the target region is geotagged (204) to confirm evenly spaced measurements by an underwater positioning system;
positioning (206) the rebound hammer perpendicular to the surface of the concrete structure by an alignment system
measuring an inclination of the rebound hammer (210) by an accelerometer, wherein the plunger is pressed firmly against the surface of the concrete structure;
loading the rebound hammer (208) by an actuator system, wherein when the actuator releases the spring driven mass from a locked position causes said mass to impact plunger which performs hammering the surface of the concrete structure and transfers energy to the surface, at which the plunger reacts and re-transmits the rebound energy to the mass causing mass to slide along the guide rod towards the rear portion of the enclosure; and
measuring (212) the rebound on a scale in the form of rebound number considering the reference position of mass, to measure the hardness.
12. The method as claimed in claim 11, further comprising converting (214) the rebound number into a digital value by a sensor.