An electro-mechanical impedance probe with resonance-promoting covers

Abstract

The disclosure regards an electro-mechanical impedance (EMI) probe for structural health monitoring, comprising at least one piezoelectric device attached on a rod, configured for generating mechanical vibrations transmitted to the surroundings, and at least one protective cover surrounding at least one part of the rod, configured for preventing vibration dampening caused by an object contacting the rod.

Description

[0001] P7240PC00

[0002] An electro-mechanical impedance probe with resonance-promoting covers The present disclosure relates to a novel electro-mechanical impedance probe with resonance-promoting covers, a structural health monitoring system and a method directed to monitoring the structural health of a structure.

[0003] Background

[0004] In the field of structural health monitoring it is highly important to predict and detect early damages in structures, in order to optimize the maintenance of such structures. The state of the art in this field relates to workers being deployed on a structure, such as a bridge, in order to conduct electro-mechanical impedance (EMI) measurements in the building blocks of the structure, such as the concrete or other building materials. Such a process is highly-costly, inefficient, and dangerous for the workers.

[0005] To address the above challenges, certain solutions have been developed, enabling testing of a probe rod while being moulded by a matrix material, such as concrete. Such a solution may generate mechanical vibrations that can propagate through the probe rod, and measure the propagated mechanical vibrations using a sensor. Then, the probe rod can alert a maintenance unit if certain damage, such as corrosion, has been detected. By utilizing such a probe rod it is possible to monitor the health of a structure. However, as such probes are typically moulded into a matrix material, and it is known that matrix materials dampen the vibrational modes of a material that they encapsulate, then such probes lead to very faint signals during an EMI measurement. As a result, it may be challenging to measure corrosion or any other damage stemming from the steel rods or from the concrete of a structure due to the vibration dampening effect before the damages are severe.

[0006] Hence, an improved system for health monitoring of a structure is needed, in order to enhance the detection properties and prevent damage in a structure at an earlier stage.

[0007] Summary

[0008] One purpose of the present disclosure is to enhance the monitoring capabilities of a structure, such as a bridge, by improving the EMI setups. Specifically, the present disclosure relates to an electro-mechanical impedance (EMI) probe for structural health monitoring, comprising at least one piezoelectric device attached on a rod, configured for generating mechanical vibrations transmitted to the surroundings, and at least one P7240PC00

[0009] protective cover surrounding at least one part of the rod, configured for preventing vibration dampening caused by an object contacting the rod.

[0010] For example, the EMI probe may be installed in a building, where at least a part of the rod is surrounded by a protective cover. Typically, such EMI probes are moulded into matrix materials, such as concrete. By being moulded into a matrix material, the EMI probe is partly in contact with the structure, and any kind of vibrations generated by a piezoelectric device will be transmitted to the structure. However, the drawback of being in contact with the structure is that the matrix material may significantly dampen the vibrations, thereby reducing the measurement capabilities of an EMI probe.

[0011] To address that challenge, the present disclosure relates to a part of the rod that is surrounded by the protective cover, thereby forming a part or structure in the rod that will not be in contact with the matrix material into which it is moulded. Such a feature provides an advantage, since when the piezoelectric material will transmit vibrations to the probe, the matrix material will not fully absorb the vibrations due to the protective cover. As a result, it is possible to use a sensor to measure the vibrations when transmitted through the rod, and to detect early signs of damage in the structure. In an embodiment, the protective cover may be placed at various parts of the rod, such as surrounding the piezoelectric device. Further details about that embodiment are provided in the detailed description of the present disclosure.

[0012] Moreover, the probe can be configured such that the at least one protective cover surrounding at least one part of the rod, optionally including the piezoelectric device, forms a space between the protective cover and the rod and / or the piezoelectric device. For example, when a protective cover is placed around a rod, the protective cover and the rod may not be in direct contact, as e.g., a space of air may be formed between the protective cover and the rod. The space may be filled with air or another material, for example, a polymer such as a polymer foam or a silicone that protects the piezoelectric device while not attenuating the vibrations from the piezoelectric device. Such a protective cover may have a custom design according to the needs of each EMI probe, e.g. customized dimensions of the cover and space. It can be advantageous to have a space between the protective cover and the part of the rod that is surrounded by the protective cover, as that can further reduce the vibration dampening effect of surrounding materials, such as embedding matrix materials. Therefore, by using such a P7240PC00

[0013] protective cover on at least one part of the rod, it is possible to probe the structural health of a building, while at the same time reducing the vibration dampening effect the building has on the EMI measurements.

[0014] Furthermore, the probe can be configured such that a piezoelectric device is attached on one end of the rod. Optionally a second piezoelectric device is attached at the opposite end of the rod, and further optionally additional piezoelectric devices are attached between the two ends. In addition, it may be beneficial that a piezoelectric device is surrounded by at least one protective cover. For example, a first protective cover may be located at a first end of the rod, and / or a second protective cover may be located at a second end of the rod. Such a configuration may further reduce the vibration dampening effect of surrounding materials, as the source of the mechanical vibrations can be protected.

[0015] The present disclosure further relates to a structural health monitoring system for installation on a structure under test, comprising an electro-mechanical impedance (EMI) probe moulded into a matrix material, such as concrete, wherein the EMI probe may be the EMI probe described above. The EMI probe may comprise at least one piezoelectric device attached on a rod, the at least one piezoelectric device configured for generating mechanical vibrations transmitted to the rod and to the matrix material. The EMI probe may further comprise at least one sensor configured to detect mechanical vibrations from the rod and from matrix material, and at least one protective cover surrounding at least one part of the rod, said protective cover preventing the matrix material from contacting onto at least one surface of the part of the rod, thereby preventing the matrix material from dampening the vibrational modes of the structure under test. Such a configuration may be utilized to detect any damage in a structure, and to possible predict any future damaged based on the detected mechanical vibrations of the at least one sensor. Additionally, the EMI probe can be installed in different stages of the construction of a building, or during a new construction phase, when e.g. new concrete is poured or retrofitted into existing concrete structures.

[0016] Therefore, the EMI probe and the structural health monitoring systems are versatile options that are capable of providing early and accurate feedback on the structural health of a structure. P7240PC00

[0017] In addition, the present disclosure relates to a method for assessing the structural health of a structure, comprising the steps: obtaining a probe moulded into a matrix material, such as concrete, wherein the EMI probe may be the EMI probe described above. The method further relates to the step of generating and transmitting mechanical vibrations to the probe and to the matrix material, said probe being in contact with a structure under test. Further, the method comprises the step of surrounding at least one part of the probe with a protective cover, said protective cover preventing the matrix material from contacting onto at least one surface of the part of the probe, thereby preventing the matrix material from dampening the vibrational modes of the structure under test, and detecting mechanical vibrations from the probe and from the structure under test.

[0018] Description of Drawings

[0019] Various embodiments are described hereinafter with reference to the drawings. The drawings are examples of embodiments and are intended to illustrate some of the features of the presently disclosed electro-mechanical impedance probe with resonance-promoting covers, and are not limiting to the presently disclosed system and method.

[0020] Fig. 1 shows a schematic of an EMI probe comprising a rod a piezoelectric device and protective covers.

[0021] Fig. 2 shows a schematic of an EMI probe comprising piezoelectric devices on the ends of the rod, wherein the piezoelectric devices are surrounded by protective covers. Fig. 3 shows a schematic of structural health monitoring system.

[0022] Fig.4 shows an example of an EMI probe where a part of the probe is moulded into a matrix material.

[0023] Fig. 5 shows the steps of the method for assessing the structural health of a structure. Fig. 6 shows an example of an EMI probe where both ends of the rod are moulded into a matrix material.

[0024] Fig. 7 shows an example of EMI probe installation in a steel rod frame.

[0025] Fig. 8 shows the real part of the EMI measurements as a function of frequency for different damage levels on a rod.

[0026] Fig. 9 shows the real part of the EMI measurements as a function of frequency for different damage levels on a rod measurements when subjected to accelerated corrosion. P7240PC00

[0027] Fig. 10 shows the real part of the EMI measurements as a function of frequency for a reference sample where no corrosion is performed.

[0028] Detailed description

[0029] As described in the summary, one purpose of the present disclosure is to provide a solution for enhancing the monitoring capabilities of a structures, by improving the existing EMI probe solutions. As the state of the art EMI probe solutions suffer from vibration dampening due to the surrounding structures to an EMI probe, the present disclosure relates to a configuration that may significantly mitigate the vibration dampening.

[0030] Specifically, the present disclosure relates to an electro-mechanical impedance (EMI) probe for structural health monitoring, comprising at least one piezoelectric device attached on a rod, configured for generating mechanical vibrations transmitted to the surroundings, and at least one protective cover surrounding at least one part of the rod, configured for preventing vibration dampening caused by an object contacting the rod. For example, as shown in Fig. 1 an EMI probe 100 may comprise a rod 101 on which a piezoelectric device 102 is attached. In this example, two parts of the rod are surrounded by protective covers 103 with the purpose of preventing vibration dampening which can be caused by an object contacting the rod. For example, when the EMI probe is moulded into a matrix material, such a concrete, the areas of the rod that are contacted by the matrix material will experience vibration dampening. By using such protective cover, the vibration dampening is reduced, allowing a sensor to capture the vibrations that are transmitted through the rod, and detect any potential damages. The piezoelectric device may be attached on the rod using an adhesive material 104. The vibrations transmitted to the surroundings are referred to vibrations that are transmitted to the EMI probe, to a matrix material that may encapsulate the probe, or to the surrounding structure of the EMI probe. As the purpose of the present disclosure is to prevent and predict and possible damage in a structure, transmitting and receiving vibrations from the whole structure can be beneficial in order to extract as much information as possible.

[0031] Moreover, the probe can be configured, such that the at least one protective cover is configured for preventing contact of a part of the probe with surrounding materials. As described above, by placing a protective cover on a part of the probe, the vibration dampening caused by any surrounding material can reduced on that part of the probe. P7240PC00

[0032] In addition, the probe can be configured, such that the at least one protective cover surrounding at least one part of the rod forms a space between the protective cover and the rod. Forming such a space can be important, as it can prevent or diminish the protective cover itself from damping the vibrations of the rod. Therefore, introducing such spaces can be beneficial to optimize the detection of vibrations in the probe. The space between the protective cover and the rod may be filled by any material that can protect the piezoelectric device from any possible damage, while at the same time such a material does not cause any attenuation of vibrations. The material can for example be a polymer such as polymer foam, polypropylene foam, and / or elastomers, such as silicones, silicone composites, silicone oil, mineral oil, and / or air.

[0033] Rod characteristics

[0034] In an embodiment, the probe can be configured such that the rod has a cylindrical shape. Depending on the type of structure that the probe can be installed on, different shapes of rods may be utilized. In addition, the probe can be configured, such that the rod is made of a solid conductive material, such as stainless steel. It is important that the rod is made of a conductive material, in order to allow the piezoelectric device to function properly and transmit electro-mechanical vibrations to the probe.

[0035] Depending on the type of application, the size of the probe may vary. In an embodiment, the rod may have a length preferably larger than 5 cm, more preferably larger than 10 cm, most preferably larger than 20 cm. Different lengths may be chosen depending on the area that the probe is to be installed in a structure. For example, a rod with small length may be chosen for an area with small volume.

[0036] Furthermore, the probe can be configured, such that the rod has a diameter preferably larger than 5 mm, more preferably larger than 10 mm, most preferably around 12 mm, such as 16, 18, 20, 22, 25, 30, 40, or 50 mm. The diameter of the rod can influence the propagation of the electro mechanical vibrations in the rod and the surrounding structures. In addition, the thickness of the protective covers depends on the material it is made of, in order to withstand pressure changes inside the moulded material without collapsing. Therefore, the choice of diameter may depend on the specific materials that surround the probe, and the characteristics of each structure.

[0037] Piezoelectric device

[0038] In addition, the probe can be configured, such that the piezoelectric device comprises or is made of a polymer, ceramic or composite material, such as lead zirconate titanate, barium titanate or lead titanate. Depending on the type of structure that is to P7240PC00

[0039] be tested, different piezoelectric device can be attached to the rod. For example, a piezoelectric device may be chosen based on the piezoelectric coefficients of a piezoelectric material or based on the quality factor of the piezoelectric material.

[0040] Depending on the type of application, different frequency signals may be used to excite the piezoelectric device in order to generate mechanical vibrations. In an embodiment the piezoelectric device is excited by sinusoidal signals of frequency in the range of 5 kHz to 500 kHz, thereby generating mechanical vibrations. That frequency range is the most important when monitoring the structural health of structures, as the vibration modes of standard building materials is found within this range. Therefore, if damage such as corrosion has occurred in a building material, such as stainless steel or concrete, a signature of that can be visible as a peak or dip in resistance measured by a sensor attached on the EMI probe.

[0041] Moreover, the probe can be configured, such that the piezoelectric device has a volume preferably less than 102mm3.

[0042] In an embodiment, it may be beneficial that a piezoelectric device is attached on one end of the rod. Optionally a second piezoelectric device is attached at the opposite end of the rod, and further optionally additional piezoelectric devices are attached between the two ends. Having that configuration allows the vibrations generated from the piezoelectric device to propagate towards the rod, before being detected by a sensor which e.g., can be attached on the other end of the probe. The piezoelectric device may be attached on the rod by an adhesive material, such as a conductive glue.

[0043] Furthermore, the probe can be configured, such that at least one piezoelectric device is surrounded by a protective cover. The inventors have realized that surrounding a piezoelectric device by a protective cover may enhance the sensitivity of the frequency measurement by a sensor, thereby increasing the performance of the EMI probe. For example, Figure 2 shows an EMI probe 200 wherein two piezoelectric devices 201 and surrounded by protective covers 202. In addition, it may be beneficial to introduce a space between the protective cover and the piezoelectric device, in order to further reduce the vibration damping which may be caused by the protective cover itself, and to enable most of the vibrations generated by a piezoelectric device to be propagated to the rod and to the surrounding materials. P7240PC00

[0044] Protective covers

[0045] The protective covers may be designed having various shapes and comprising different materials. In an embodiment, the probe can be configured such that the at least one protective cover is made of a plastic, metallic or composite material. Specifically, any type of hard plastic, either 3D printable or moldable material may be used. Metallic covers may be used if the metallic covers are electrically and mechanically isolated from the rod.

[0046] It is found that the hardness of the protective cover affects the vibration attenuation significantly, specifically for a protective cover surrounding a piezoelectric device. A protective cover with a high hardness will dampen the vibrations significantly, e.g. to a similar degree as the concrete, such that no improvement in the quality of the measurements may be obtained, and similarly a protective cover that is too soft may provide no protection and just fall of the probe. Thus, to mitigate degradation of a resonance peak for an EMI probe with a piezoelectric device surrounded by a protective cover, and particularly in physical contact with the protective cover, the protective cover advantageously has sufficient and tailored hardness. The hardness of a protective cover may be quantified by the Shore hardness scale shown in Table 1 below. The hardness may be measured based on the method of JIS S 6050 SRIS- 0101 (GS-701N).

[0047] Table 1. Shore hardness scale.

[0048] A 1020 30405060 708090 100

[0049]

[0050] Advantageously, the protective cover is made of a polymer, preferably an elastomer, where an elastomer is a polymer with elastic properties, since the hardness of such materials may be precisely tailored. For example, the protective cover advantageously comprises or consists of a silicone or silicone composite, where silicone composite means a mixture of a silicone having reinforcing fillers, such as fibers or additives. In an embodiment of the disclosure, the at least one protective cover is made of a polymer, a P7240PC00

[0051] polymer foam, an elastomer, a silicone, or a silicone composite, and preferably comprises a silicone or silicone composite, and most preferably consists of a silicone.

[0052] To further facilitate tailoring of the hardness, the protective cover advantageously comprises or consists of a two-component elastomer, such as a two-component silicone. By the term two-component is meant a mix-to-use kit, where the two parts may react to form the elastomer. For example, a two-component silicone may comprise a first component A and a second component B, which may be mixed to react and form a solid elastic silicone rubber. The hardness of the elastomer will accordingly depend on the hardness of respectively component A and B and the mixing ratio between the two components. For example, for a two-component silicone, it is found that the hardness between component A and B preferably is configured such that the mixing ratio is equal to or between 1:5 to 1:40, such as 1:10 or 1:20. In an embodiment of the disclosure, the at least one protective cover comprises or consists of a two-component elastomer, such as a two-component silicone. In a further embodiment, the two-component elastomer has a ratio between the first component and second component of 1:5 to 1:40, more preferably a ratio of 1:7 to 1:30, and most preferably a ratio of 1:10, 1:15, or 1:20.

[0053] To facilitate reduced vibration attenuation, the protective cover is advantageously configured to have a hardness larger than 20 Shore A, such as a hardness of 43 Shore A. In an embodiment of the disclosure, the at least one protective cover is configured to have a hardness larger than 20 Shore A, more preferably larger than 25 Shore A, even more preferably larger than 30 Shore A, most preferably larger than 40 Shore A, such as 43 Shore A, and preferably lower than 70 Shore A, more preferably lower than 60 Shore A, even more preferably lower than 50 Shore A, most preferably lower than 45 Shore A, such as between 45 Shore A and 30 Shore A.

[0054] The hardness range of silicones may be particularly advantageous and flexible to tailor. Using silicone that is too hard or too soft will reduce the vibrations and the quality of the measurements. However, a hardness between 50 Shore A and 30 Shore A is found to allow the probe, e.g. the ends of the probe to vibrate essentially freely, specifically when the probe is cast into concrete. In an embodiment of the disclosure, the at least one protective cover consists of a two-component silicone with a hardness of between 50 Shore A and 30 Shore A, such as 35, 40, 43, 45, or 47 Shore A. P7240PC00

[0055] For further reduce vibration attenuation, the protective cover may be a solid protective cover, such as a solid silicone cover in direct physical contact with the rod and / or probe along the surrounded part, as shown in Figure 1. Further, the probe may be adapted with a first protective cover located at a first end, and a second protective cover located at a second end of the rod, as shown in Figure 2. In an embodiment of the disclosure, the at least one protective cover is a solid protective cover, such that the at least one protective cover is in direct physical contact with the rod along the surrounded part. In a further or alternative embodiment, a first protective cover is located at a first end of the rod, and a second protective cover is located at a second end of the rod.

[0056] Advantageously, the protective cover has both a sufficient hardness and / or thickness to provide efficient reduced vibration attenuation. For example, the protective cover may be a 30 mm thick solid silicone. In an embodiment of the disclosure, the thickness of the at least one protective cover is 5-50 mm, more preferably 10-40 mm, and most preferably 15-35 mm, such as 20, 25, or 30 mm.

[0057] The measurements, shown in the example in Figure 8, were repeated for 8 probes cast into concrete, where the ends of the probes were surrounded by protective covers consisting of silicone. The probes included rods with diameter 10 mm and 16 mm, and the protective silicone covers have a thickness of 30 mm. The silicone covers were two-component silicones with mixing ratios of 1:10 or 1:20, corresponding to a hardness between 50 Shore A and 30 Shore A. For example, a cover may have a mixing ratio of 1:10 and a hardness of 43 Shore A.

[0058] The measurements were similar to Figure 8, and distinct peaks in the frequency signature were obtained including sharp peaks sensitive to damage and corrosion. For comparative tests without protective covers, vibrations are attenuated, and a much lower degree of sensitivity will be present.

[0059] The 8 probes were further subjected to variable degree of corrosion. Fig. 9 shows an example of an accelerated corrosion measurement, where a probe rod is submerged in salt water and exposed to accelerated corrosion by a current, such as an anodic current. Figure 9 shows the real part of the EMI measurements 900 as a function of frequency 901 for two different time points, each corresponding to a different damage P7240PC00

[0060] level on a rod. The first curve 902 corresponds to a measurement from 14 October 2025, while the second curve 903 corresponds to a measurement from 11 November 2025, where the probe rod has been corroded by the accelerated corrosion process. The shift in the frequency peak around 200 kHz, and the increase of the measured impedance indicate that corrosion and damage have occurred. Thus, a clear difference in the frequency signature and amplitude of measured impedance is seen as a function of the degree of corrosion. As a result, the presently disclosed protective covers can provide early signs of corrosion in a material, by enabling monitoring of resonance peaks, which can be directly linked to the structural quality of the material. As described herein, such an increase in sensitivity of the recorded signals is enabled by supressing the vibration dampening effect which is present when a probe rod is in contact with other materials, for example when in contact with concrete.

[0061] For reference, Figure 10 shows a reference sample, where the probe is not submerged in saltwater and not exposed to a current. The real impedance 1000 is monitored as a function of frequency 1001 for a first measurement 1002 performed on 14 October 2025, and a second measurement 1003 performed on 11 November 2025. As this is a reference sample where no corrosion is performed, the resonance peak 1004 at 200 kHz is stable with respect to its magnitude and frequency. By utilizing the protective covers of the present disclosure, vibration damping can be prevent, thereby enabling more resonance peaks to be successfully recorded by the sensor.

[0062] Importantly, state of the art solutions that do not comprise protective covers as described herein would not be capable of recording such resonance peaks, as vibration dampening would absorb the energy before reaching the sensor. Therefore, the EMI probe of the present disclosure provides significant advantages compared to state of the art solutions, as the EMI probe can accurately monitor resonance peaks and enable a user to follow any signs of possible structural damage. As a result, maintenance can be cheaper and carried out before irreparable damage has been made on a structure.

[0063] Moreover, the probe can be configured, such that the at least one protective cover has a ring shape, comprising an inner diameter and an outer diameter, wherein the inner diameter is preferably larger than the diameter of the rod, and the outer diameter is preferably smaller than twice the diameter of the rod. Preferably, the outer diameter of P7240PC00

[0064] the protective covers can be as small as possible, in order to enable the EMI probe to be installed easily in structures.

[0065] Structural health monitoring system

[0066] The present disclosure further relates to a structural health monitoring system for installation on a structure under test, comprising an electro-mechanical impedance (EMI) probe moulded into a matrix material, such as concrete. The EMI probe may comprise at least one piezoelectric device attached on a rod, the at least one piezoelectric device configured for generating mechanical vibrations transmitted to the rod and to the matrix material, at least one sensor configured to detect mechanical vibrations from the rod and from matrix material, and at least one protective cover surrounding at least one part of the rod, said protective cover preventing the matrix material from contacting onto at least one surface of the part of the rod, thereby preventing the matrix material from dampening the vibrational modes of the structure under test. Such a configuration may be utilized to detect any damage in a structure, and to possible predict any future damaged based on the detected mechanical vibrations of the at least one sensor. Additionally, the EMI probe can be installed in different stages of the construction of a building, or during a new construction phase, when e.g. new concrete is poured or retrofitted into existing concrete structures. The structural health monitoring system may detect and predict any damage not only in the rod and the matrix material, but also in the surrounding structure that may be in contact with the rod.

[0067] The at least one sensor may be any kind of sensor capable of detecting electromechanical vibrations. A sensor may be installed in a concrete structure where the concrete before additional concrete is poured to the structure. Therefore, it is possible to extract structural health information in the sensor that will be inside the concrete structure, as well as temperature and humidity data. The humidity data may warn about possible water leakage in the building. In addition, the humidity data may be used to calibrate the system, as different ranges of humidity may affect the EMI measurements. The sensors may be installed in any type of structure, such as bridges, tunnels, houses, commercial buildings, or any other concrete structure, either when the structure is built or when the structure is retrofitted. P7240PC00

[0068] Figure 3 shows an example of a structural health monitoring system comprising an EMI probe. The EMI probe comprises a rod 300, such as a steel bar, a piezoelectric device 301 attached to the rod with an adhesive material and a sensor 303 for detecting mechanical vibrations. The EMI probe may be moulded into a matrix material 304, such as concrete. For example, mechanical vibrations by the piezoelectric device can be transmitted through the rod, accessing also a damaged part of the rod 312. These mechanical vibrations will be modified due to the damaged part, and they can be detected by the sensor 303. The sensor may comprise a corrosion sensing unit 305, a communication 306 configured to send and receive data to a second device, and antenna 307 for facilitating wireless communication, a power management unit (PMU) 308 and a super capacitor 309. In an embodiment, the sensor may also comprise an artificial neural network 310, configured to collect and analyze the detected data, and predict possible damage in the structure. The EMI probe may further comprise a reference electrode 311, configured to acquire mechanical vibrations of the structure, with the purpose of subtracting the background vibrations that may occur.

[0069] Figure 4 shows an example of an EMI probe, where a rod 400 has a part surrounded by a protective cover 401. A part of the rod is moulded into a matrix material 402, such as concrete.

[0070] The system can be configured, such that the sensor is configured to detect mechanical vibrations in a spectrum between 5 kHz to 500 kHz. Further, the sensor may be configured to detect humidity data and / or temperature data. Temperature and humidity may affect the detected vibrations. Therefore, it can be beneficial to detect the temperature and humidity in order to correct the detected vibrations accordingly, and to correctly assign certain changes in the detected vibrations to environmental factors.

[0071] The system can be configured, such that the sensor comprises an antenna configured to transmit the detected mechanical vibrations and / or data to an auxiliary device. Such an auxiliary device may be a server, or any computing unit which may analyze the data, and alert a user if certain maintenance shall be conducted in the tested structure. Accordingly, the system can be configured according to any one of the embodiments described herein. For example, the system may be configured to comprise the probe described herein. P7240PC00

[0072] Method for assessing structural health

[0073] The present disclosure further relates to a method for assessing the structural health of a structure, comprising the steps: obtaining a probe moulded into a matrix material, such as concrete, generating and transmitting mechanical vibrations to the probe and to the matrix material, said probe being in contact a structure under test, surrounding at least one part of the probe with a protective cover, said protective cover preventing the matrix material from contacting onto at least one surface of the part of the probe, thereby preventing the matrix material from dampening the vibrational modes of the structure under test, and detecting mechanical vibrations from the probe and from the structure under test. The steps of the method can be seen in Fig. 5. The first step is obtaining a probe moulded into a matrix material 500, then generating and transmitting mechanical vibrations to the probe and to the matrix material 501, surrounding at least one part of the probe with a protective cover 502, and detecting mechanical vibrations from the probe and from the structure under test 503.

[0074] The steps of the method can be configured according to any one of the embodiments of the present disclosure. For example, the method may be configured to be carried out be carried out by the probe and / or the system described herein. Further, the probe and / or the system described herein may be configured to carry out the method described herein.

[0075] Examples

[0076] Figure 6 shows an example of an EMI probe 600 comprising a rod 601 and two piezoelectric devices that are surrounded by protective materials 602. Said parts with the protective materials are moulded into a matrix material, in this example concrete. Such an EMI probe may be installed into a structure, such as into a frame of steel bars 700 as shown in Figure 7.

[0077] Figure 8 shows measurements of resistance 800 as a function of frequency 801 in a 15 cm long rod moulded into concrete using 3D printed protective covers. The resistance, which is the real part of the EMI measurements, relates to how a structure responds to mechanical vibrations. The resonance peaks and dips when the rod is damaged 803 804 and clearly visible in comparison to the resonance peaks and dips when no damage was caused to the rod 802. Such sensitivity is caused by the use of the P7240PC00

[0078] protective covers, that reduce the vibration dampening effect of the moulded material and other surrounding materials. P7240PC00

[0079] Further details

[0080] 1. An electro-mechanical impedance (EMI) probe for structural health monitoring, comprising

[0081] • at least one piezoelectric device attached on a rod, configured for generating mechanical vibrations transmitted to the surroundings, and • at least one protective cover surrounding at least one part of the rod, configured for preventing vibration dampening caused by an object contacting the rod.

[0082] 2. The probe according to item 1 , wherein the at least one protective cover is configured for preventing contact of a part of the probe with surrounding materials.

[0083] 3. The probe according to any one of the preceding items, wherein the at least one protective cover surrounding at least one part of the rod forms a space between the protective cover and the rod.

[0084] 4. The probe according to item 3, wherein the space formed between the protective cover and the rod is filled by a material, such as a polymer, a polymer foam, an elastomer, a silicone, a silicone composite, and / or air.

[0085] 5. The probe according to any one of the preceding items, wherein the rod has a cylindrical shape.

[0086] 6. The probe according to any one of the preceding items, wherein the rod is made of a solid conductive material, such as stainless steel.

[0087] 7. The probe according to any one of the preceding items, wherein the rod has a length preferably larger than 5 cm, more preferably larger than 10 cm, most preferably larger than 20 cm.

[0088] 8. The probe according to any one of the preceding items, wherein the rod has a diameter preferably larger than 5 mm, more preferably larger than 10 mm, most preferably around 12 mm, such as 16, 18, 20, 22, 25, 30, 40, or 50 mm. P7240PC00

[0089] 9. The probe according to any one of the preceding items, wherein the piezoelectric device comprises or is made of a polymer, ceramic or composite material, such as lead zirconate titanate, barium titanate or lead titanate.

[0090] 10. The probe according to any one of the preceding items, wherein the piezoelectric device is excited by sinusoidal signals of frequency in the range of 5 kHz to 500 kHz, thereby generating mechanical vibrations.

[0091] 11. The probe according to any one of the preceding items, wherein the piezoelectric device has a volume preferably less than 102mm3.

[0092] 12. The probe according to any one of the preceding items, wherein the at least one piezoelectric device is attached on one end of the rod, optionally wherein a second piezoelectric device is attached at the opposite end of the rod, and further optionally additional piezoelectric devices are attached between the two ends.

[0093] 13. The probe according to any one of the preceding items, wherein a piezoelectric device is attached on the rod by an adhesive material, such as a conductive glue.

[0094] 14. The probe according to any one of the preceding items, wherein at least one piezoelectric device is surrounded by the at least one protective cover.

[0095] 15. The probe according to any one of the preceding items, wherein the at least one protective cover is made of a plastic, metallic or composite material.

[0096] 16. The probe according to any one of the preceding items, wherein the at least one protective cover is made of a polymer, a polymer foam, an elastomer, a silicone, or a silicone composite, and preferably comprises a silicone or silicone composite, and most preferably consists of a silicone.

[0097] 17. The probe according to item 16, wherein the at least one protective cover comprises or consists of a two-component elastomer, such as a two-component silicone. P7240PC00

[0098] 18. The probe according to item 17, wherein the two-component elastomer has a ratio between the first component and second component of 1:5 to 1:40, more preferably a ratio of 1:7 to 1:30, and most preferably a ratio of 1:10, 1:15, or 1:20.

[0099] 19. The probe according to any one of the preceding items, wherein the at least one protective cover is configured to have a hardness larger than 20 Shore A, more preferably larger than 25 Shore A, even more preferably larger than 30 Shore A, most preferably larger than 40 Shore A, such as 43 Shore A, and preferably lower than 70 Shore A, more preferably lower than 60 Shore A, even more preferably lower than 50 Shore A, most preferably lower than 45 Shore A, such as between 45 Shore A and 30 Shore A.

[0100] 20. The probe according to any one of items 17-19, wherein the at least one protective cover consists of a two-component silicone with a hardness of between 50 Shore A and 30 Shore A, such as 35, 40, 43, 45, or 47 Shore A.

[0101] 21. The probe according to any one of the preceding items, wherein the at least one protective cover is a solid protective cover, such that the at least one protective cover is in direct physical contact with the rod along the surrounded part.

[0102] 22. The probe according to any one of the preceding items, wherein a first protective cover is located at a first end of the rod, and a second protective cover is located at a second end of the rod.

[0103] 23. The probe according to any one of the preceding items, wherein the thickness of the at least one protective cover is 5-50 mm, more preferably 10-40 mm, and most preferably 15-35 mm, such as 20, 25, or 30 mm. P7240PC00

[0104] 24. The probe according to any one of the preceding items, wherein the at least one protective cover has a ring shape, comprising an inner diameter and an outer diameter, wherein the inner diameter is preferably larger than the diameter of the rod, and the outer diameter is preferably smaller than twice the diameter of the rod.

[0105] 25. A structural health monitoring system for installation on a structure under test, comprising

[0106] • an electro-mechanical impedance (EMI) probe moulded into a matrix material, such as concrete, comprising

[0107] o at least one piezoelectric device attached on a rod, the at least one piezoelectric device configured for generating mechanical vibrations transmitted to the rod and to the matrix material, o at least one sensor configured to detect mechanical vibrations from the rod and from matrix material, and

[0108] o at least one protective cover surrounding at least one part of the rod, said protective cover preventing the matrix material from contacting onto at least one surface of the part of the rod, thereby preventing the matrix material from dampening the vibrational modes of the structure under test.

[0109] 26. The system according to item 25, wherein the sensor is configured to detect mechanical vibrations in a spectrum between 5 kHz to 500 kHz.

[0110] 27. The system according to any one of the items 25-26, wherein the sensor is further configured to detect humidity data and / or temperature data.

[0111] 28. The system according to any one of the items 25-27, wherein the sensor comprises an antenna configured to transmit the detected mechanical vibrations and / or data to an auxiliary device.

[0112] 29. The system device according to any one of the items 25-28, wherein the system is configured according to any one of the items 1-24, such as configured to comprise the probe according to any one of items 1-24. P7240PC00

[0113] 30. A method for assessing the structural health of a structure, comprising the steps • Obtaining a probe moulded into a matrix material, such as concrete, • generating and transmitting mechanical vibrations to the probe and to the matrix material, said probe being in contact a structure under test, • surrounding at least one part of the probe with a protective cover, said protective cover preventing the matrix material from contacting onto at least one surface of the part of the probe, thereby preventing the matrix material from dampening the vibrational modes of the structure under test, and

[0114] • detecting mechanical vibrations from the probe and from the structure under test.

[0115] 31. The method according to item 30, configured to be carried out by the probe according to any one of items 1-24 and / or the system according to any one of items 25-29.

[0116] 32. The probe according to any one of items 1-24 and / or the system according to any one of items 25-29, configured for carrying out the method according to item 30.

Claims

P7240PC00Claims1. An electro-mechanical impedance (EMI) probe for structural health monitoring, comprising• at least one piezoelectric device attached on a rod, configured for generating mechanical vibrations transmitted to the surroundings, and • at least one protective cover surrounding at least one part of the rod, configured for preventing vibration dampening caused by an object contacting the rod.

2. The probe according to claim 1 , wherein the at least one protective cover is configured for preventing contact of a part of the probe with surrounding materials.

3. The probe according to any one of the preceding claims, wherein the at least one protective cover surrounding at least one part of the rod forms a space between the protective cover and the rod.

4. The probe according to claim 3, wherein the space formed between the protective cover and the rod is filled by a material, such as a polymer, a polymer foam, an elastomer, a silicone, silicone composite and / or air.

5. The probe according to any one of the preceding claims, wherein the rod has a diameter preferably larger than 5 mm, more preferably larger than 10 mm, most preferably around 12 mm.

6. The probe according to any one of the preceding claims, wherein the at least one piezoelectric device is attached on one end of the rod, optionally wherein a second piezoelectric device is attached at the opposite end of the rod, and further optionally additional piezoelectric devices are attached between the two ends.

7. The probe according to any one of the preceding claims, wherein a piezoelectric device is attached on the rod by an adhesive material, such as aP7240PC00conductive glue.

8. The probe according to any one of the preceding claims, wherein at least one piezoelectric device is surrounded by the at least one protective cover.

9. The probe according to any one of the preceding claims, wherein the at least one protective cover is made of a plastic, metallic or composite material, such as a polymer, a polymer foam, an elastomer, a silicone, or a silicone composite, and preferably comprises a silicone or silicone composite, and most preferably consists of a silicone.

10. The probe according to any one of the preceding claims, wherein the at least one protective cover has a ring shape, comprising an inner diameter and an outer diameter, wherein the inner diameter is preferably larger than the diameter of the rod, and the outer diameter is preferably smaller than twice the diameter of the rod.

11. The probe according to any one of the preceding claims, wherein the at least one protective cover consists of a two-component silicone with a hardness of between 50 Shore A and 30 Shore A, such as 35, 40, 43, 45, or 47 Shore A.

12. A structural health monitoring system for installation on a structure under test, comprising• an electro-mechanical impedance (EMI) probe moulded into a matrix material, such as concrete, comprisingo at least one piezoelectric device attached on a rod, the at least one piezoelectric device configured for generating mechanical vibrations transmitted to the rod and to the matrix material, o at least one sensor configured to detect mechanical vibrations from the rod and from matrix material, ando at least one protective cover surrounding at least one part of the rod, said protective cover preventing the matrix material from contacting onto at least one surface of the part of the rod, thereby preventing the matrix material from dampening theP7240PC00vibrational modes of the structure under test.

13. The system according to claim 12, wherein the sensor is configured to detect mechanical vibrations in a spectrum between 5 kHz to 500 kHz.

14. The system device according to any one of the claims 12-13, wherein the system is configured to comprise the probe according to any one of the claims 1-11.

15. A method for assessing the structural health of a structure, comprising the steps • Obtaining a probe moulded into a matrix material, such as concrete, • generating and transmitting mechanical vibrations to the probe and to the matrix material, said probe being in contact a structure under test, • surrounding at least one part of the probe with a protective cover, said protective cover preventing the matrix material from contacting onto at least one surface of the part of the probe, thereby preventing the matrix material from dampening the vibrational modes of the structure under test, and• detecting mechanical vibrations from the probe and from the structure under test.

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