Description:FORM 2
THE PATENTS ACT 1970
[39 OF 1970]
&
The Patents Rules, 2003

COMPLETE SPECIFICATION
[See section 10 and rule 13]

TITLE: “A METHOD AND A SYSTEM FOR NON-DESTRUCTIVE TESTING OF ROD LIKE STRUCTURE”

Name and Address of the Applicant:
TATA STEEL LIMITED, Jamshedpur, Jharkhand, India 831001.

Nationality: INDIAN

The following specification particularly describes the nature of the invention and the manner in which it is to be performed.

TECHNICAL FIELD

The present disclosure relates to the field of structural health monitoring. Particularly, but not exclusively, the present disclosure relates to a non-destructive testing method and a system for monitoring and detecting defects in rod like structures with a single accessible end. Further embodiments of the present disclosure disclose the method and the system for detecting defects by transmitting high frequency acoustic signals through the rod.

BACKGROUND

Generally, large structures are constructed for manufacturing, processing, storage etc. These structures may comprise of large components or rod like supporting members that are often welded or bolted together. The whole structure may further be firmly connected to the ground surface by means of large bolts and nuts. Over the time, due to the constant load acting over these structures and other environmental factors, the components of the structure begin to deteriorate. The foundation bolts or rod like structures are also susceptible to deterioration and any damage to these rods which goes un-checked may further lead to an unstable foundation and the integrity of the overall structure may be compromised. Also, risk of such structures collapsing also greatly increases. Hence, there exists a need to monitor the rods in any given structure by a suitable means.

Failures of many cylindrical rod-like structures in various plants is a cause of concern with. Some of the examples of in-service failures of these structures are most commonly observed in foundation bolts i.e. anchor studs, T-head bolts, etc. The foundation bolts are mainly used in pre-engineered buildings and the foundation bolts are also used for fastening heavy machines to foundations in various industries. Failure of these bolts can be due to stress corrosion cracking, corrosion wastages, fatigue cracking or far end cracks, etc. Further, failure of the tie rods through necking at the corroded regions mainly used in coke oven batteries as post-tensioning members for the refractory sidewalls are also commonly observed. Wear of nuclear fuel rods in nuclear power plants and damage of ropes, cables, etc. due to microcracking or corrosion have become a common phenomenon and the monitoring of these structures has become necessary. The above-mentioned structures are usually embedded in soil or concrete i.e. having one end accessibility in most of the cases.

Non-destructive methods have been developed for monitoring the condition of the rods and other critical components in any given structure. The patent application “EP3176575A1” provides a method and device for non-destructive testing of an anchor bolt. As per the method of ‘675 application, the section of the anchor bolt that is exposed from the surface of the foundation is hit to produce an impact noise and a signal waveform and a corresponding impact noise is received and subjected to frequency analysis to obtain frequency information for the said signal waveform. However, from the method disclosed in the ‘675 application, it is tough to analyze signals discarding the unexpected noise. In most of the applications mentioned above, the method of ‘675 application cannot be directly used because of many operational constraints such as water sprinkling for cooling in high-temperature applications.

Further, the patent document “EP0935258A1” describes a method and apparatus for ultrasonic inspection of a nuclear fuel rod. The method of ‘258 application involves transmitting ultrasonic guided waves through the fuel rod and detecting a reflected ultrasonic wave which is indicative of a variation of the wall thickness. The method of ‘258 application is based on the comb method where guided waves are induced by a periodic distribution of normal excitations with the spatial period equaling the wavelength of the excited mode. However, the above-mentioned apparatus is fixed around the circumference of the fuel rod and is not possible if the circumferential access is not present. Further, the apparatus cannot be used if the circumference of the rod comprises of threads, since surface irregularities often interfere with the transmission and the reception of the waves.

With advancements in technologies, ultrasonic guided wave inspection for testing small-diameter (around 15 mm) cylindrical steel anchor rods embedded in soil have been used. Piezoelectric probes are attached to the sides of the rods and ultrasonic waves are transmitted along the circumference of the rods. The piezoelectric probes often transmit ultrasonic waves at low frequencies which serves better for detecting corrosion wastages and a reduction in diameter of the rod due to corrosion. However, the low frequencies used in the above methods are not suitable for detecting fatigue cracks in the rods. Also, an access to the circumference of the rod is always required since the piezoelectric probes are coupled on the circumference of the anchor rods. These rods are often mounted below the ground surface and accessibility to mount the piezoelectric probes along the circumferential surface of the rod is not always possible.

Conventionally, the excitation of the ultrasounds was by mounting a sensor on the circumference of the structure. However, for a majority of the rods or anchor bolts that lie under the ground surface, there might not be an accessible circumferential portion for mounting those sensors for excitation of a mode. Further, due to the cylindrical geometry of the rod, the sensors or the piezoelectric probes that are mounted on the circumference of the rods produce multiple internal reflections of the ultrasonic beam instead of the normal beam spread. Consequently, the mode-converted signals due to the multiple internal reflections result in confusion in detecting and analyzing the reflected ultrasonic waves.

The present disclosure is directed to overcome one or more limitations stated above or other such limitations associated with the conventional methods or apparatus.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of the conventional system and method are overcome by the system and method as claimed and additional advantages are provided through the provision of the system as claimed in the present disclosure.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment of the disclosure, a method for non-destructive testing of rod is disclosed. The method comprises of transmitting a high frequency acoustic signals through the rod by a transceiver, where the transceiver is provisioned at an accessible end of the rod. Further, a reflected acoustic signal from the rod is received by the transceiver. Also, an indication unit associated with the transceiver indicates a waveform of the reflected acoustic signal where, a variation in amplitude of the waveform of the reflected acoustic signal is indicative of defects in the rod.

In an embodiment of the disclosure, the high frequency acoustic signal is a product of the frequency transmitted by the transceiver and a diameter of the rod and is greater than 40 MHz-mm for steel rods.

In an embodiment of the disclosure, the high frequency acoustic signal is a product of the frequency transmitted by the transceiver and a diameter of the rod divided by velocity at which the transmitted frequency travels through the rod and is greater than 10 for the rod made of a material other than steel.

In an embodiment of the disclosure, the transmitted wave reflects from the boundary of the rod and is converted into different modes.

In an embodiment of the disclosure, the defects in the rod is at least one of necking, due to corrosion and fatigue cracks.

In an embodiment of the disclosure, a time of flight (TOF) of the reflected acoustic signal is indicative of the location of defects.

In an embodiment of the disclosure, the high frequency acoustic signal generates an ultra-higher order mode cluster (UHOMC) guided wave regime in the rod.

In another non-limiting embodiment of the disclosure, a system for non-destructive testing of rod is disclosed. The system comprises of a transceiver positioned at an accessible end of the rod. The transceiver is configured to transmit a high frequency acoustic signal through the rod and receive a reflected high frequency acoustic signal. Further, an indication unit associated with the transceiver is configured to indicate a waveform of the reflected acoustic signal, where a variation in amplitude of the waveform of the reflected signal is indicative of the defects in the rod.

In an embodiment of the disclosure, the transmitted wave reflects from the boundary of the rod and is converted to different modes.

In an embodiment of the disclosure, the different modes generated due to the reflection along the boundary of the rod are longitudinal, flexural or torsional.

In an embodiment of the disclosure, the high frequency acoustic signal generates an ultra-higher order mode cluster (UHOMC) guided wave regime in the rod.

In an embodiment of the disclosure, the receiver and the indication unit is an oscilloscope.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

The novel features and characteristics of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

Fig. 1 is a schematic representation of system for non-destructive testing of a rod showing ultrasonic wave propagation through a rod for detecting defects, in accordance with an embodiment of the present disclosure.

Fig. 2 shows a dispersion plot of ultrasound waves of different frequencies through a steel rod, in accordance with an embodiment of the present disclosure.

Fig. 3a and 3b are schematic representations of system of Fig. 1, showing necking and fatigue cracks on the rod, according to an exemplary embodiments of the disclosure.

Fig. 4 illustrate a graphical representation of waveforms displayed by an indication unit when necking or reduction in diameter of the rod is detected, in accordance with an embodiment of the present disclosure.

Fig. 5 illustrate a graphical representation of waveforms displayed by an indication unit when a fatigue crack is detected in the rod, in accordance with an embodiment of the present disclosure.

Figs. 6a to 6c are schematic representations of system of Fig. 1, showing different positioning arrangements of a transducer and a receiver at an accessible end of the rod, according to an exemplary embodiments of the disclosure.

Fig. 7a to 7c are a schematic representations of system of Fig. 1, showing the rod with threads, nut, a change in a head section of the rod and a modified positioning of a transceiver, according to an exemplary embodiments of the disclosure.

Fig. 8 is a schematic representation of the of ultrasonic wave propagation through the rod with the modified positioning of a transceiver, in accordance with an embodiment of the present disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the method for non-destructive testing of rod illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other devices for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure. The novel features which are believed to be characteristic of the disclosure, as to its organization, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a system that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such mechanism. In other words, one or more elements in the device or mechanism proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the mechanism.

Embodiments of the present disclosure discloses a method for non-destructive testing of rod. In conventional methods, the excitation of the ultrasounds was by mounting a sensor on the circumference of the structure. However, for a majority of the rods or anchor bolts that lie under the ground surface, there might not be an accessible circumferential portion for mounting those sensors for excitation of a mode. Further, due to the cylindrical geometry of the rod, the sensors or the piezoelectric probes that are mounted on the circumference of the rods produce multiple internal reflections of the ultrasonic beam which results in uncertainty in detecting and analysing the reflected ultrasonic waves. Also, conventional methods of detecting defects in rod are mainly focussed on detecting necking or reduction in diameter of the rod. However, fatigue cracks are often not detected, since conventional methods involve ultrasound transducers transmitting low frequency ultrasound wave.

Accordingly, the present disclosure discloses a method and a system for non-destructive testing of rod. The method involves, transmitting a high frequency acoustic signals through the rod by a transceiver, where the transceiver is positioned at an accessible end of the rod. In an embodiment, the high frequency acoustic signal from the transceiver is a product of the frequency transmitted by the transceiver and a diameter of the rod and is greater than 40 MHz-mm for steel rods. Further, for the rod made of a material other than steel, the high frequency acoustic signal is a product of the frequency transmitted by the transceiver and a diameter of the rod divided by a velocity at which the transmitted frequency travels through the rod is greater than 10. These, high frequency acoustic signals transmitted from the transceiver, reflect from the boundary of the rod and gets converted into different modes. Further, the acoustic signals are reflected back to the transceiver when a defect is encountered along the rod. The reflected signals are indicated by an indication unit associated with the transceiver. The amplitude and the time of flight of the reflected signals are analysed to determine the type of the defect and the location of the defect.

The following paragraphs describe the present disclosure with reference to Figs. 1 to 8.

Fig. 1 is a schematic representation of ultrasonic wave propagation through a rod (8) for detecting defects. The rod (8) includes an accessible end (13) and the other end or non-accessible end (7) of the rod (8) may often not be reachable in case of applications such as but not limited to anchor bolts. Anchor bolts are often used to secure the foundation of a structure to the ground and the anchor bolts often lie below the ground surface. Therefore, most of the anchor bolts comprise of the accessible end (13) which lies above the ground surface and the non-accessible end (7) which lies below the ground surface. Further, the accessible end (13) of the rod (8) is provided with a transceiver (Z). The transceiver (Z) further includes a transducer (Z1) and a receiver (Z2) [as shown in Fig. 6]. Further, the rod (8) has a diameter: (D0) and the transceiver (Z) that is provided at the accessible end (13) of the rod (8) transmits ultrasonic waves of high frequency (f) through the rod (8). The high frequency acoustic signal or the ultrasonic waves that are transmitted by the transceiver (Z) at the accessible end (13) of the rod (8) is such that the product of the frequency (f) transmitted by the transceiver (1) and a diameter (D0) of the rod (8) and is greater than 40 MHz-mm for steel rods (8) i.e. f*D0>40 MHz-mm. For any given diameter (D0), the frequency (f) that is transmitted from the transceiver (Z) is increased such that the overall product of the transmitted frequency (f) and the diameter (D0) of the rod (8) becomes greater than 40 MHz-mm for rods (8) of steel material. For example, if the diameter (D0) of the rod (8) made of steel is 10mm, then the frequency (f) of the ultrasonic waves that are transmitted through the transceiver (Z) must be greater than 4 MHz so that the product of the diameter (D0) and the frequency (f) transmitted becomes greater than 40 MHz-mm. Thus, the operator or a control unit may choose a suitable frequency (f) for transmission through the rod (8) based on the diameter (D0) of the rod (8) such that the condition: f*D0>40 MHz-mm is complied with. The maximum value of 40MHz-mm for steel rods (8) is preferred since the transmission of higher frequency (f) acoustic signal generates a guided wave. Further, the velocity (v) at which the transmitted guided wave travels through the rod (8) is a function of the frequency (f) at which the ultrasonic wave is transmitted through the rod (8). This relation is explained in greater detail below.

Fig.2 shows a dispersion plot of ultrasound waves of different frequencies through a steel rod (8). The plot may be divided into four regimes where 101 shows a conventional guided wave regime, 102 shows higher-order mode (HOM) guided wave regime, 103 shows higher-order mode cluster (HOMC) guided wave regime and 104 shows a regime where ultra-higher order mode cluster (UHOMC) guided wave regime. The UHOMC guided wave regime behaves as a non-dispersive guided wave regime.

As seen from the Fig. 2, the X-axis represents the product of frequency (f) and rod diameter (f*D0) in MHz-mm at which the ultrasonic wave is transmitted through the rod (8) and the Y axis represents the phase velocity (v) at which the transmitted ultrasonic wave propagates through the rod (8). A close observation from the Fig. 2, clearly shows that the velocity (v) of the transmitted ultrasonic wave varies drastically when the product of frequency (f) and rod diameter is around 10 MHz-mm. When the product of frequency and rod diameter is below 20 MHz-mm, the frequency lies along the conventional guided wave regime (101) and around higher-order mode (HOM) guided wave regime (102). The velocity (v) at which the ultrasonic waves travel through the rod (8) in these guided wave regimes (101 and 102) vary drastically. The variation in this velocity is seen from V1. However, as the frequency increases beyond 40MHz in the UHOMC guided wave regime (104), the velocity (v) becomes constant throughout. Therefore, by transmitting a frequency (f) above 40 MHz-mm, a constant velocity (v) at which the transmitted ultrasonic wave travels through the rod (8) is achieved. The constant velocity is seen from V2.

S. No. D0
(mm) Material Frequency (f) (MHz) f* D0
(MHz-mm) L-Mode Velocity (m/s)
1 40 42CrMo4
(Steel) 4 160 5865
2 40 1 40 5848
3 40 0.5 20 2541
4 40 0.15 6 3058
5 80 4 320 5846
6 80 2 160 5846
7 80 1 80 5846
8 80 0.5 40 5840
9 100 4 400 5815
10 100 2 200 5800
11 100 1 100 5810
12 100 0.5 50 5810

With further reference to the above Table.1, various experiments have been conducted where the velocity (v) of the transmitted ultrasonic wave is recorded for the product of various values of the transmitted frequency (f) and the rod diameter (D0). With reference to the first four rows of the table. 1, the rod diameter (D0) is 40mm and the frequency is varied to different values. As seen from the rows three and four, for f* D0 value of 20 and 6 MHz-mm, the velocity (v) at which the ultrasonic eaves travel through the steel rod (8) is 2541 and 3058 m/s. These velocities (v) are greatly different from each other. However, with reference to rows 1 and 2, for f* D0 value of 160 and 40 MHz-mm, the velocity (v) at which the ultrasonic waves travel through the steel rod (8) is 5865 and 5848 m/s and the variation between these velocities (v) is very less. Hence, transmitting an ultrasonic wave in compliance with the condition of f*D0>40 MHz-mm, enables the transmitted wave to travel though the rod (8) at a constant velocity (v). Almost constant propagation velocity (v) of the transmitted ultrasonic wave can also be observed from the rows 4 to 8 and 9 to 12, where the velocity (v) at which the transmitted wave travels through the rod (8) remains almost constant for values of frequency greater than 40 Hz. Thus, it may be concluded that transmitting an ultrasonic wave in the UHOMC guided wave regime (frequency greater than 40 MHz) enables the transmitted wave to travel through the rod (8) at a constant velocity.

Further, for materials other than steel, the high frequency (f) acoustic signal is a product of the frequency (F) transmitted by the transceiver (Z) and the diameter (D0) of the rod (8) divided by a velocity (v) at which the transmitted frequency (f) travels through the rod (8) is greater than 10 i.e. (f* D0/v)>10. For any given diameter (D0), the frequency (f) that is transmitted from the transceiver is increased such that the overall product of the transmitted frequency (f) and the diameter (D0) of the rod (8) divided by the velocity (v) at which the transmitted frequency (f) travels through the rod (8) becomes greater than 10 for rods (8) of material other than steel. Thus, the operator may choose a suitable frequency (f) for transmission through the rod (8) based on the diameter (D0) of the rod (8) and the velocity (v) at which the transmitted frequency (f) travels such that the condition: (f* D0/v)>10 is complied with.

In an embodiment of the disclosure, modes of excitation of guided waves in the rod (8) by the transceiver (Z) may be piezoelectric, laser, magneto strictive, electromagnetic based transduction or any other method known in the art.

Fig. 3 is a schematic representation of necking (N) due to corrosion and fatigue cracks (C) on the rod (8). With further reference to Fig. 1 and Fig. 3, the transceiver (Z) positioned at the accessible end (13) of the rod (8) transmits a high frequency (f) ultrasonic wave which is in compliance with the condition of f*D0>40 for rod (8) of steel material and the condition of (f* D0/v)>10 for rod (8) of any other material than steel. When the transmitted wave reflects from the boundary of the rod (8), it gets converted to different modes i.e. longitudinal, flexural or torsional mode and follows sine law. Since, the transmitted waves are of a higher frequency, a great number of modes are generated, and interactions of these modes further generate different higher-order modes which form a UHOMC guided wave regime (104). The propagation model though the rod (8) when a wave is transmitted from the transceiver (Z) is shown in Fig. 1. The transmitted wave initially forms a Fresnel zone (9) and a Fraunhofer zone (10) around the accessible end (13) of the rod (8). As the wave travels further along the rod (8), the wave interacts with the boundaries of the rod (8) and mode conversion (1) occurs in the rod (8). When the initial wave interacts with boundary of the rod (8), the wave gets reflected and converts into a shear wave (3) and longitudinal wave (4). This reflection and conversion of the transmitted wave into the shear wave (3) and longitudinal wave (4) is called as a first mode conversion. The shear wave (3) further interacts with the boundary and coverts into S-Mode (5) and L-Mode (6). The S and L mode (6 and 7) waves have the shape of the letters S and L respectively, after reflection from the boundary of the rod (8). As the beam divergence is very low in case of higher frequencies, one of the wave directly reaches the rod end (7) by first mode conversion and follows a path of 2 to 4. The second wave may reach the rod end (7) through multiple reflections along the boundary of the rod (8) by following the path 2-3-6. The first wave that follows the second wave may generate trailing echoes.
Over time, due to harsh environmental conditions and due to fatigue, the rods (8) may be subjected to corrosion. The corrosive environment results in necking (N) or reduction in diameter of the rod (8) at certain areas. Further, fatigue cracks (C) also develop along the surface of the rod (8) and the cracks (C) may further propagate through the rod (8). Fatigue cracks (C) are caused majorly due to vibrations and fatigue loading. As seen from Fig. 3, corrosion may cause the diameter, D0 of the rod (8) to be reduced to a diameter D1. Further, this reduced diameter D1 may be observed only for a certain length “L1” along the overall length “L0” of the rod (8). With further reference from Fig. 1, when a high frequency (f) acoustic signal or ultrasonic wave is transmitted through the rod (8) by the transceiver (Z) at the accessible end (13), the ultrasonic waves travel along the rod (8) and when the wave interacts with the boundaries of the rod (8), mode conversion (1) occur in the rod (8). As the wave propagates through the rod (8), any defects in the rod (8) will cause the high frequency wave to be reflected. The reflected wave is received by the transceiver (Z) and is suitably indicated by an indication unit (15).

Fig. 4 illustrates a graphical representation of waveform displayed by an indication unit (15) when necking (N) or reduction in diameter of the rod (8) is detected. 4(a) and 4(b) in Fig. 4 show the waveform and corresponding results after recording the reflected and transmitted waves for abnormalities in the wave due to reduction in cross-section of the rod (8). When no defects are detected in the rod (8), the waveform is almost constant, and no peak amplitudes are observed as seen from Fig. 4(a). However, when the 20% reduction in the cross-section of the rod (8) is present, a corresponding disruption in the wave, in the form of an increased amplitude is indicated by the indication unit (15). Waveform generated when necking (N) is observed can be seen from Fig. 4(b). 20% reduction in cross-section of the rod (8) is indicative of a reduction in diameter of the rod (8). With reference to Fig. 3(a), corrosion causes necking (N) of the rod (8) and the diameter of the rod (8) reduces from D0 to D1. A 20 % reduction in diameter signifies (D0- D1)/ D0=20. Further, scenarios where the reduction in diameter of the rod (8) may vary are also suitably indicated by the indication unit (15) based on the reflected high frequency wave.

Fig. 5 illustrates a graphical representation of waveform displayed by an indication unit (15) when cracks (C) are detected in the rod (8). 5(a) shows the waveform from a rod (8) without any cracks (C). Further, when the waveform and corresponding results after recording the reflected and transmitted waves in a rod (8) with fatigue cracks (C) is observed, irregularities (740) in the form of peak amplitudes are prevalent in the waveform as seen from 5(b). Peak amplitudes in the waveform are often indicative of necking (N) or the crack (C) present in the rod (8). The cracks (C) and necking (N) in the rod (8) is often detected. Further, the amplitude of the reflected acoustic signal due to defects in the rod (8) is greater than the amplitude of the reflected acoustic signal travelling through the rod (8). In an embodiment, the amplitude of the reflected waveform when a fatigue crack (C) is detected in the rod (8) may be lesser than the amplitude of the waveform indicated due to necking (N) in the rod (8). The time of flight (TOF) for the transmitted wave to be reflected from abnormalities such as necking (N) or cracks (C) may be detected by the receiver and this TOF may further be suitably indicated by the indication unit (15). Further, this TOF of the reflected signal from the abnormalities (N or C) is directly indicative of the exact location of the crack. Since, the velocity (v) at which a reflected or a transmitted wave travels through the rod (8) would already be known, the precise location along the length of the rod (8) where the abnormalities (N or C) exist may be easily calculated from the recorded TOF of the reflected signal. Thus, the result from the indication unit (15), show easy identification of far end fatigue cracks (C) with a greater resolution and sensitivity.

In an embodiment of the disclosure, the indication unit (15) is an oscilloscope.

In an embodiment of the disclosure, sizing of the defects may be accomplished. By obtaining more samples for different kinds of defects and accordingly comparing the detected anomaly with the recorded samples, the precise size of the defect or the anomaly may be predicted.

Fig. 6 is a schematic representation of embodiments with different positioning arrangements of the transducer (Z1) and the receiver (Z2) at the accessible end (13) of the rod (8). In an embodiment of the disclosure, as seen from Fig. 6(a), a first arrangement may include transducer (Z1) and receiver (Z2) as a single probe mounted at the accessible end (13) of the rod (8). In an embodiment of the disclosure, as seen from Fig. 6(b), transducer (Z1) and receiver (Z2) are separate probes mounted at the accessible end (13) of the rod (8). In an embodiment of the disclosure, as seen from Fig. 6(c), the transducer (Z1) and receiver (Z2) are separate probes where transducer (Z1) is mounted at the accessible end (13) and receiver (Z2) is mounted at the circumference of the accessible end (13).

Fig. 7 is a schematic representation of the rod (8) of Fig.1 with threads (11), nut (12), a change in the section (14) of the rod (8) and a modified positioning of a transceiver (Z). The above-mentioned rods (8) are ideal rod-like structures. However, there might be a possibility of the presence of threads (11), nut (12), head or section change (14) or groove (16) at the accessible end (13) of these rods (8). Accordingly, the Fig. 7 shows the modified positioning of the transducer (Z1) and receiver (Z2). The rod (8) having threads (11) and nut (12) at both the ends (e.g.: tie rods, anchor bolts, etc.) is shown in Fig. 7(a). Further, the rod (8) having threads (11) and nut (12) at the accessible end (13) (e.g.: head bolts i.e. hex, T-head, etc.) and head/cross-sectional change (14) at the other end is shown in Fig. 7(b). Both of the above-mentioned conditions include rods (8) with threads (11), nut (12) and head/cross-sectional change (14). Even with such configuration, the transceiver (Z) mounted at the accessible end (13) of the rod (13) enables the transmission of high frequency acoustic waves throughout the rod (8). = In an embodiment, the transceiver (Z) provided at the accessible end (13) of the rod (8) transmits high frequency acoustic waves beyond 40MHz, thereby generating a greater number of modes, and interactions of these modes further generate different higher-order modes which form a UHOMC guided wave regime. Since, a greater number of modes are generated due to internal reflection along the rod (8), any small defects or abnormalities cause the transmitted wave to be reflected. Further, the high transmission frequency also ensures that the transmitted waves travel along the overall length of the rod (8). Fig. 7(c) shows the provision of a grove (15) at the accessible end (13) of the rod (8). Under such conditions, the transceiver cannot be mounted at the centre since, the grove (15) would create discrepancies when the transceiver (Z) transmits the high frequency acoustic waves. Therefore, the positioning of the transceiver (Z) is modified. Accordingly, the transceiver (Z) may either be positioned above or below the groove (15).

Fig. 8 is a schematic representation of the of ultrasonic wave propagation through the rod (8) with a groove (15) and with the modified positioning of a transceiver (Z). As mentioned above, the transceiver (Z) may be positioned right below the groove (16). The positioning or mounting of the transceiver (Z) may also be provided above the groove (16). The change in the ray diagram by mounting the transceiver (Z) a little offset with respect to the centre of the accessible end (13) is shown in Fig. 8. Since, the space of mounting the transceiver (Z) is less when the groove (15) exists in the rod (8), the beam divergence is comparatively higher due to less transducer diameter. The ray propagation is almost the same as described above. One of the wave directly reaches the rod end (7) by first mode conversion and follows a path of 2-4. The second wave reaches the rod end (7) by following 2-3-6. As described above, these transmitted waves reflect when they encounter any abnormalities and the reflected wave is further indicated on the indication unit (15) in a suitable waveform.

In an embodiment of the disclosure, the waveforms indicated by the indication unit (15) is analysed by an expert to identify the peak amplitudes that are indicative of necking (N) and the cracks (C) in the rod (8). The rod (8) may comprise of bends and other small anomalies which are also revealed in the waveform indicated by the indication unit (15). Therefore, analysis by an operator may be required for detecting amplitudes which indicate necking (N) and the cracks (C) in the rod (8).

In an embodiment of the disclosure, the transceiver (Z) may be mounted only at the accessible end (13) of the rod (8) for detecting all the minor defects such as necking (N) and cracks (C).

In an embodiment of the disclosure, the transceiver (Z), transmits high frequency acoustic waves beyond 40MHz-mm for steel and beyond 10MHz-mm divided by longitudinal velocity of the sound for other materials.’, thereby generating a greater number of modes and interactions of these modes further generate different higher-order modes which form a UHOMC guided wave regime.

In an embodiment of the disclosure, the transceiver (Z), transmitting the high frequency acoustic waves, not only enables the detection of necking (N) in the rod (8), but also enables the detection of minute cracks (C) in the rod (8)

Equivalents

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding the description may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated in the description.
Referral Numerals:

Description Referral numerals
Mode conversion in the rod 1
Initial wave 2
Shear wave 3
Longitudinal wave 4
S mode wave 5
L mode wave 6
Rod end 7
Rod 8
Fresnel zone 9
Fraunhofer zone 10
Threads 11
Nut 12
Accessible end 13
Change in head section 14
Indication unit 15
Grove 16
Necking N
Surface crack C
Transceiver Z
Transmitter Z1
Receiver Z2

Claims:We Claim:

1. A method for non-destructive testing of a rod (8), the method comprising:
transmitting, by a transceiver (Z) high frequency acoustic signals through the rod (8), wherein the transceiver (Z) is provisioned at an accessible end (13) of the rod (8);
receiving, by the transceiver (Z) a reflected acoustic signal from the rod (8);
indicating, by an indication unit (15) associated with the transceiver (Z), a waveform of the reflected acoustic signal wherein, a variation in amplitude of the waveform of the reflected acoustic signal is indicative of defects in the rod (8).

2. The method as claimed in claim 1, wherein the high frequency acoustic signal is a product of the frequency (f) transmitted by the transceiver (Z) and a diameter (D0) of the rod (8) and is greater than 40 MHz-mm for steel rods (8).

3. The method as claimed in claim 1, wherein the high frequency acoustic signal is a product of the frequency (f) transmitted by the transceiver (Z) and a diameter (D0) of the rod (8) divided by velocity (v) at which the transmitted frequency travels through the rod (8) and is greater than 10 for the rod (8) made of a material other than steel.

4. The method as claimed in claim 1, wherein the transmitted wave reflects from the boundary of the rod (8) and is converted into different modes.

5. The method as claimed in claim 1, wherein the defects in the rod is at least one of necking (N) due to corrosion and, fatigue cracks (C).

6. The method as claimed in claim 1, wherein a time of flight (TOF) of the reflected acoustic signal is indicative of location of the defects.

7. The method as claimed in claim 1, wherein the high frequency acoustic signal generates an ultra-higher order mode cluster (UHOMC) guided wave regime in the rod (8).

8. A system (100) for non-destructive testing of a rod (8), the system comprising:
a transceiver (Z) positioned at an accessible end of the rod (8), wherein, the transceiver (Z) is configured to:
transmit a high frequency acoustic signal through the rod (8); and
receive a reflected high frequency acoustic signal; and
an indication unit (15) associated with the transceiver (Z), configured to indicate a waveform of the reflected acoustic signal, wherein a variation in amplitude of the waveform of the reflected signal is indicative of defects in the rod (8).

9. The system (100) as claimed in claim 8, wherein the transmitted wave reflects from the boundary of the rod (8) and is converted to different modes.

10. The system (100) as claimed in claim 9, wherein the different modes generated due to the reflection along the boundary of the rod (8) are longitudinal, flexural or torsional.

11. The system (100) as claimed in claim 8, wherein the high frequency acoustic signal generates an ultra-higher order mode cluster (UHOMC) guided wave regime in the rod (8).

12. The system (100) as claimed in claim 8, wherein receiver (Z2) and the indication unit (15) is an oscilloscope.