Patent Description:
In the field of ultrasonic inspection, it is sometimes necessary to use two modes of waves to accurately detect a part for inspection for certain material properties, dimensions, or defects. For example, in the detection of the nodularity of spheroidal graphite cast iron, if there is only one mode of waves, it is not easy to distinguish whether the change in the time-of-flight is from a change in the thickness of the sample or from a change in the speed of the ultrasonic wave itself, which greatly affects the effectiveness of the inspection. For example, in the assessment of the tensile force of the bolt, if only one mode of ultrasonic wave is adopted, it cannot be known whether the time-of-flight of the ultrasonic wave is from the change of the part's dimension or the change of the speed of the ultrasonic wave caused by the tensile stress of the bolt. Thus, the bolt tension cannot be detected by an ultrasonic method.

In order to generate ultrasonic waves of two different modes, the open literature <NUM> (<NPL>) mentioned that the ultrasonic longitudinal wave generates mode-converted transverse wave on the reflection bottom surface of the part to be measured by employing a specially designed piezoelectric ultrasonic transducer; the open literature <NUM> (<NPL>) mentions that an electromagnetic ultrasonic transverse wave transducer generates mode-converted longitudinal wave at the reflection bottom of the part to be tested by using a high-power source for excitation and a multiple averaging method; the open literature <NUM> (<NPL>) mentions that the ultrasonic longitudinal waves and transverse waves are respectively generated in the testing part by adopting two piezoelectric transducers in combination; the open literature <NUM> (US Patent <CIT>) mentions the use of a piezoelectric transducer in combination with an electromagnetic ultrasonic transducer to generate longitudinal and transverse waves, respectively, on the surface of a testing part. <CIT> discloses a wave electromagnetic acoustic sensor according to prior art.

None of the methods in the above open literature can generate both longitudinal wave and transverse wave on the surface of the part to be inspected, causing errors in high-precision inspection, particularly in bolt tension inspection. The piezoelectric transducers referred to in the open literature <NUM> to <NUM> need to take the influence of the wedges and the couplant on the propagation time of the ultrasonic wave during the forward and backward propagation of the ultrasonic wave from the piezoelectric wafer to the surface of the part to be tested. Neither of the electromagnetic ultrasonic transducers described in the open literature <NUM> and <NUM> can generate ultrasonic longitudinal wave on the surface of a testing part.

Based on the problems in the prior art, the invention aims at providing an electromagnetic ultrasonic double-wave transducer, which can simultaneously generate longitudinal wave and transverse wave on the surface of a testing part.

Based on the above problems, the invention provides a technical solution:.

An electromagnetic ultrasonic double-wave transducer according to claim <NUM>, comprising a shell, and a permanent magnet assembly, a coil, a shielding layer, and a wire which are provided in said shell.

Said permanent magnet assembly comprises a first permanent magnet and a second permanent magnet sleeved on the first permanent magnet. The magnetizing directions of the first permanent magnet and the second permanent magnet are perpendicular to the bottom of said shell, and the magnetic field directions of said first permanent magnet and the second permanent magnet are opposite; a non-conducting non-magnetic bushing material is provided between said first permanent magnet and said second permanent magnet, and upper end faces of said first permanent magnet and said second permanent magnet realize magnetic circuit closing by means of a magnetic circuit closing element.

Said coil is fixed on the bottom of said shell and is located below said first permanent magnet. Said shielding layer is provided between the lower end of said first permanent magnet and said coil and below said second permanent magnet. One end of said wire is connected to said coil, and the other end is connected to power supply and signal plug.

In one embodiment, said first permanent magnet is cylindrical while said second permanent magnet is annular.

In one embodiment, the inner diameter of said second permanent magnet is <NUM>-<NUM> larger than the outer diameter of said first permanent magnet.

In one embodiment, the lower end faces of said first permanent magnet and said second permanent magnet have a height difference from -<NUM> to <NUM>.

In one embodiment, said coil is helical, and the outer diameter thereof is larger than the outer diameter of said first permanent magnet and smaller than the inner diameter of said second permanent magnet.

In one embodiment, the non-conductive material is filled between said coil and said shielding layer, and the non-conducting non-magnetic material is filled between said permanent magnet assembly and said shell.

In one embodiment, said shell includes a shell body and a wear plate disposed at the lower end of said shell body.

In one embodiment, the non-conductive material is filled between said coil and said shielding layer, and the non-conducting non-magnet-conduction material is filled between said permanent magnet assembly and said shell.

Compared with the prior art, the invention has following advantages;.

By adopting the technical solution of the invention, the ultrasonic transducer can simultaneously excite longitudinal waves and transverse waves on the surface of a testing part, and the two modes of ultrasonic waves are used for detecting physical quantities such as material properties like elastic modulus of materials, defects, length, stress and the like, thereby the measurement error caused by the time delay of the piezoelectric ultrasonic wedge and the coupling agent is avoided, the detection error possibly caused by the mode conversion of the ultrasonic waves is also avoided, and the detection precision is improved.

In order to more clearly illustrate the technical solutions of the embodiments of the invention, the drawings required to be used in the description of the embodiments are briefly introduced below, the drawings in the description are only some embodiments of the invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

The above-described solution is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes and are not intended to limit the scope of the invention. The conditions used in the embodiments may be further adjusted according to the conditions of the particular manufacturer, and the conditions not specified are generally conditions used in routine experiments.

As is shown in <FIG>, a schematic structural diagram of the embodiment in the invention provides an electromagnetic ultrasonic double-wave transducer, comprising a shell <NUM>, and a permanent magnet assembly, a coil <NUM>, a shielding layer <NUM>, and a wire <NUM> which are provided in the shell <NUM>.

The permanent magnet assembly comprises a first permanent magnet <NUM> and a second permanent magnet <NUM> sleeved on the first permanent magnet <NUM>. The magnetizing directions of the first permanent magnet <NUM> and the second permanent magnet <NUM> are perpendicular to the bottom of the shell <NUM>, and the magnetic field directions of the first permanent magnet <NUM> and the second permanent magnet <NUM> are opposite. A non-conducting non-magnetic bushing material <NUM> is provided between the first permanent magnet <NUM> and the second permanent magnet <NUM>, and upper end faces of the first permanent magnet <NUM> and the second permanent magnet <NUM> realize magnetic circuit closing by means of a magnetic circuit closing element <NUM>.

Said coil <NUM> is fixed on the bottom of said shell <NUM> and is located below said first permanent magnet <NUM>. Said shielding layer <NUM> is provided between the lower end of said first permanent magnet <NUM> and said coil <NUM> and below said second permanent magnet <NUM>. One end of said wire <NUM> is connected to said coil <NUM>, and the other end is connected to a power supply and signal plug <NUM>.

In this embodiment, the magnetic circuit closing element <NUM> is made of mild steel or ferrite with a thickness greater than <NUM>. The non-conducting non-magnetic bushing material <NUM> is made of plastic, rubber or polymer material, such as bakelite.

The inner diameter of said second permanent magnet <NUM> is <NUM>-<NUM> larger than the outer diameter of said first permanent magnet <NUM>, and said coil <NUM> is helical, and the outer diameter thereof is larger than the outer diameter of said first permanent magnet <NUM> and smaller than the inner diameter of said second permanent magnet <NUM>. The lower end face of the first permanent magnet <NUM> can be flush with that of the second permanent magnet <NUM>, and they also can have a height difference of less than <NUM>, which means that the lower end face of the first permanent magnet <NUM> is located above that of the second permanent magnet <NUM>, or is located below that of the second permanent magnet <NUM>.

In this embodiment, the shielding layer <NUM> is a highly conductive copper sheet or silver sheet, and is attached to the lower ends of the first permanent magnet <NUM> and the second permanent magnet <NUM>.

In order to further optimize the implementation effect of the invention, the non-conductive material <NUM> is filled between said coil <NUM> and said shielding layer <NUM>, such as air, resin and non-conductive soft magnetic material; the non-conducting non-magnetic material is filled between said permanent magnet assembly and said shell <NUM>, i.e., epoxy resin.

In this embodiment, said coil <NUM> is made of double-layer PCB board or wound by enameled wire.

In this embodiment, said shell <NUM> includes a shell body <NUM>-<NUM> and a wear plate <NUM>-<NUM> disposed at the lower end of said shell body <NUM>-<NUM>; the wear plate <NUM>-<NUM> is made of ceramic wafer or epoxy plate and the shell body <NUM>-<NUM> is made of stainless steel, aluminum alloy or red copper material; the power supply and signal plug <NUM> is fixed at the upper part of the shell body <NUM>-<NUM>.

As is shown in <FIG>, the schematic structural diagram of embodiment <NUM> is the same as the embodiment <NUM> except structure of the permanent magnet assembly and structure of the coil <NUM>; the permanent magnet assembly comprises a third permanent magnet <NUM> and a fourth permanent magnet <NUM> wherein the fourth permanent magnet <NUM> are arranged side by side with said third permanent magnet <NUM> and located on two sides of the width direction of said third permanent magnet <NUM>, and between said fourth permanent magnet <NUM> and said third permanent magnet <NUM> are non-conducting non-magnetic bushing material <NUM>;.

In this embodiment, the cross sections of said third permanent magnet <NUM> and said fourth permanent magnet <NUM> are rectangular and said coil <NUM> is butterfly shaped.

In the implementation, the first permanent magnet <NUM>, the second permanent magnet <NUM>, the third permanent magnet <NUM> and the fourth permanent magnet <NUM> are all made of NdFeB materials.

The electromagnetic ultrasonic transducer can simultaneously excite vertical downward-transmitted ultrasonic transverse waves and ultrasonic longitudinal waves on the near surface of a conductive or magnetic testing part such as low-carbon steel, aluminum alloy and the like, and the amplitude of the longitudinal waves excited by said electromagnetic ultrasonic transducer can reach <NUM>% to <NUM>% of the transverse waves at most in a test with a matched instrument. While the conventional electromagnetic ultrasonic transducer can hardly excite longitudinal wave.

For example, the Young's modulus and the Poisson's ratio of isotropic materials were detected by using the electromagnetic ultrasonic double-wave transducer of embodiment <NUM>.

In isotropic materials, the elasticity modulus E and Poisson's ratio v are related to the velocity of the longitudinal wave Cl and the transverse wave CS as follows:
<MAT>
<MAT>
where T is defined as T≡Cl/CS, ρ is the density, and taken <NUM>×<NUM><NUM>kg/m<NUM> for <NUM># carbon steel.

Therefore, the Young's modulus and the Poisson's ratio of the material can be estimated by detecting the longitudinal wave velocity, the transverse wave velocity and the density of the material.

A hand-held high-power ultrasonic testing instrument PREMAT-HS200 manufactured by Suzhou Phaserise Technology Co. is used as an electromagnetic ultrasonic pulser/receiver equipped with the electromagnetic ultrasonic double-wave transducer of the invention. The testing part is selected from a CSK-IIA standard sample according to JB/T <NUM>-<NUM> standard. The sample dimension is <NUM> long, <NUM> wide and <NUM> in height The electromagnetic ultrasonic transducer is placed in the middle of the upper surface of the sample to be tested, and is <NUM> away from the left edge of the sample, and <NUM> away from the upper edge. The test frequency is <NUM>, the excitation voltage 1200Vpp, the display delay <NUM>, the sampling time <NUM>, the sampling speed <NUM>/s, and the repetition rate <NUM>. The test data for the automatic gain is shown in <FIG>. Increasing the gain further on the basis of <FIG> results in <FIG>. In <FIG>, multiple periodic echoes and mode-converted waves are labeled, and it can be seen that the electromagnetic ultrasonic double-wave transducer of the invention excites longitudinal waves (first echo is LL) and transverse waves (first echo is SS) simultaneously on the surface of the sample.

Calculations from equations (<NUM>) and (<NUM>) using the data in table <NUM> lead to:
<MAT>
<MAT>.

The results are very close to the nominal value of the sample.

The transducer of the invention can be used for accurate detection of bolt tension. According to the open literature <NUM>(<NPL>), the Bolt tension σ can be expressed as
<MAT>.

wherein γ is the clamping length ratio of the bolt, namely the ratio of the length of the bolt under tension to the total length; E is the Young's modulus; α is the acoustic elastic coefficient of the transverse wave; β is the acoustic elastic coefficient of the longitudinal waves; CS0 and Cl0 are transverse and longitudinal wave velocities in the absence of tension; TOFs is the fight time of bolt transverse wave; TOFl is the fight time of bolt longitudinal wave. For the bolt with calibrated material parameters, the tensile stress applied to the bolt can be calculated as long as TOFS and TOFl can be accurately measured. The transducer used by the invention can simultaneously excite longitudinal waves and transverse waves on the inspection surface end of the bolt. <FIG> shows that longitudinal wave (LL) and transverse wave (SS) signals are simultaneously excited on the tested surface end of a bolt with <NUM> nominal diameter by using the electromagnetic ultrasonic double-wave transducer of the invention. Thus, TOFs and TOFl values can be simultaneously and accurately measured. <FIG> is the experimental raw data of TOFS and TOFl ratio versus tensile stress applied to the <NUM>-nominal-diameter bolt in <FIG>. during calibration by a hydraulic bolt tensile machine. As can be seen from <FIG>, the correspondence between the two is a relatively smooth monotonous function in one-to-one correspondence, and the corresponding bolt tensile stress error range is relatively small. Professional data processing methods can also be applied to process the one-to-one monotone function shown in the <FIG>, so as to obtain higher inspection precision for the bolt tensile stress.

For instance, Young's modulus and the Poisson's ratio of isotropic materials were measured by using the electromagnetic ultrasonic double-wave transducer of embodiment <NUM>.

After selecting the same sample and measurement parameters as in embodiment <NUM>, The <FIG> in embodiment <NUM> corresponds to <FIG> of embodiment <NUM>. In <FIG>, the amplitude of the longitudinal wave generated simultaneously with the transverse wave on the surface of the testing sample is about one third of that of the embodiment <NUM>, but the final detection results of the Young's modulus and the Poisson's ratio are not much different from that of the embodiment <NUM>. In addition, the electromagnetic ultrasonic double-wave transducer of embodiment <NUM> is directional, and is very advantageous for detecting the sound velocity of transverse waves and the longitudinal waves in each direction of a material having a regular texture, such as a cold-rolled steel sheet or an aluminum sheet.

Claim 1:
An electromagnetic ultrasonic double wave transducer, comprising a shell (<NUM>), and a permanent magnet assembly, a coil (<NUM>), a shielding layer (<NUM>), a magnetic closing element (<NUM>), a power supply and signal plug (<NUM>) and a wire (<NUM>) which are provided in the shell (<NUM>); said permanent magnet assembly comprises a first permanent magnet (<NUM>) and a second permanent magnet (<NUM>) sleeved on the first permanent magnet (<NUM>); the magnetizing directions of the first permanent magnet (<NUM>) and the second permanent magnet (<NUM>) are perpendicular to the bottom of the shell (<NUM>), and the magnetic field directions of the first permanent magnet (<NUM>) and the second permanent magnet (<NUM>) are opposite; a non-conducting non-magnetic bushing material (<NUM>) is provided between the first permanent magnet (<NUM>) and the second permanent magnet (<NUM>), and upper end faces of the first permanent magnet (<NUM>) and the second permanent magnet (<NUM>) realize magnetic circuit closing by means of the magnetic circuit closing element (<NUM>); said coil (<NUM>) is fixed on the bottom of said shell (<NUM>) and is located below said first permanent magnet (<NUM>); said shielding layer (<NUM>) is provided between the lower end of said first permanent magnet (<NUM>) and said coil (<NUM>) and below said second permanent magnet (<NUM>); one end of said wire (<NUM>) is connected to said coil (<NUM>), and the other end is connected to the power supply and signal plug (<NUM>).