DE102011011764A1 - Ultrasonic measuring system for determining pre-stressing force in e.g. screw of e.g. steel girder, has data processing unit that is structurally separated from and connected to data acquisition unit via wired or wireless connection - Google Patents

Abstract

The ultrasonic measuring system has a data acquisition unit (20), and a transducer (12) for transmitting an ultrasonic pulse to a connecting element (10) and for receiving the ultrasonic pulse echoes from the connecting element, where the data acquisition unit is connected with the transducer. A data processing unit (24) is structurally separated from the data acquisition unit and connected to the data acquisition unit via a wired or wireless connection (22). An independent claim is included for method for performing ultrasonic measurement.

Description

Technical area

The present invention relates to an ultrasonic measuring system which includes an ultrasonic transducer and allows accurate transit time measurements of ultrasonic pulses in stressors such as screws, bolts, rivets, or the like, under tension.

State of the art

Out DE 42 25 035 A1 and DE 42 32 254 A1 Ultrasonic testing methods are known. DE 10 2004 038 638 refers to a connection component, in whose head or foot area there is an ultrasonic sensor whose structure is formed as a layer structure.

DE 10 2009 060 441 A1 relates to a sensor element. A connecting component comprises an integrated ultrasonic sensor for analyzing the mechanical stress distribution, in particular for determining the pretensioning force of the connecting component, the ultrasonic sensor having an at least two-layered construction with an electrode layer and at least one layer of a material having piezoelectric properties. The electrode layer and the layer of a material having piezoelectric properties are vapor-deposited, in particular sputtered, on at least one freely accessible end of the connection component, wherein structures are formed in the electrode layer by producing lasered-out regions.

The most important field of ultrasonic measuring methods is the investigation of mechanical stress conditions, in particular the measurement of the prestressing force in connecting elements of various types. Another very broad area is health monitoring of fasteners and components exposed to dynamic loads. The basis of these measurements is the excitation, the propagation and the detection of mechanical ultrasonic waves in the materials to be investigated, which pass through the stressed or stressed areas of the components, thereby changing their properties in characterizing manner. Especially in the case of force measurement, the difference between the transit times of an ultrasound pulse between a connecting element under mechanical tension and an unloaded reference state is determined. Due to the mechanical tension, both an extension of the connecting element is forced, and the speed of sound in the material is reduced. It is thus possible to measure an increase in the sound propagation time, which in turn can be converted into forces via empirical calibration parameters.

The o. G. Methods of providing connectors with glued or sputtered transducers place a converter, which converts electrical signals and waveforms into mechanical ultrasonic pulses and back, directly on the connector. To excite the transducer and register the echoes, a combination of digital and analog electronics is required, which is connected to the transducer via cable. For data analysis, data storage and presentation of the measurement results, a computer integrated in the measuring unit is used. Pulse-transmitting and echo-receiving electronics are housed together with the evaluation computer in a common housing or rack. In order to avoid interference of the measuring signals and to limit the signal attenuation, the integrated measuring unit itself must be placed in the vicinity of the measuring point.

Presentation of the invention

The present invention has for its object to provide an ultrasonic measuring system, with the principle of the ultrasonic pulse echo method allows an investigation of the mechanical stress state and the internal structure of polycrystalline materials by ultrasonic transducers.

In particular, the present invention has the object, the determination of the biasing force in fasteners of various types, such as screws, bolts or rivets to allow reliable.

To measure the voltage states in the connecting elements, however, only the analog / digital component of the pulse transmitting and echo receiving electronics is necessary at the location of the measurement since the analog signals involved can not be transmitted to and from the transducer wirelessly. After the digitization of the echo signals, all further processing steps can be performed both spatially and temporally separated from the location and time of the excitation of the transducer. An inventively proposed separation of the analog-digital pulse-transmitting echo receiving electronics from the data analysis and storage unit connected behind is advantageous in cases where there are strong spatial limitations at the measuring location and no measuring electronics can be installed where the measuring location is not constantly accessible and continuous in time the condition is to be monitored or, with the smallest possible size, manual measurements are to be made at a specific point or in an inspection mode.

In particular, with modern wireless transmission methods, digital data can be transmitted without disruption and loss to an analysis system with corresponding evaluation software, which can run on any suitable computer system detached from special hardware and can thus easily be adapted to extended requirements with regard to the analysis methods or improved computer systems. Technologies (eg faster CPUs) for z. For example, can exploit larger measurement rates. The determination of the user to a specific hardware and instrumentation equipment is significantly reduced. A separate development of the analog-digital pulse transmitting and echo receiving electronics and their purely information technology connection with a corresponding industry-compatible computer system reduces the turnaround time for technical changes.

When the connector is fixedly mounted with said analog-digital pulse-transmitting and echo-receiving electronics, the previously passive transducer-provided screw becomes an active element of a connection acting as a physical sensor such as pressure / temperature and itself can monitor. A further development is the integration of the transducer / electronics combination in the screw already during their production, the active screw can then connect with your environment, either actively queried or automatically send all necessary data about their condition, without necessarily a permanent Connection with a receiver of the data is required.

Following the solution proposed according to the invention, the difference between the transit times of an ultrasound pulse between a connecting element under mechanical tension and an unloaded reference state is determined, which can be converted into forces via empirical calibration parameters. The transit time of an ultrasound pulse in a material in turn is given by the length of a connecting element together with the speed of sound, wherein the emitted pulse is reflected at the opposite end of the transmitter. The method of force measurement is based on the physical principles of the change in length of a connecting element under mechanical stress and the concomitant reduction in the propagation velocity of a shaft. Both mechanisms lead to increase the transit time of an ultrasonic pulse in a connecting element in the built-in, d. H. charged condition.

For the generation of an ultrasonic pulse in a connecting element, a converter is required, which converts electrical signal forms into corresponding mechanical waveforms upon transmission of the pulse and conversely reconverts to an electrical analogue signal upon receipt of the echo. Such ultrasonic transducers exist in a wide variety of designs and have a wide variety of conversion characteristics. In particular, it is the piezo-thin-film transducer applied in a high vacuum according to FIG DE 10 2009 060 441 A1 to name a, which has a very broadband conversion characteristic and relatively weak echo signals. In contrast, for example, are classic glued piezo-disk transducers, which are very narrow-band and correspondingly stronger ultrasonic echo signals to deliver.

The inventively proposed ultrasonic measuring system uses in close conjunction with digital hardware these different characteristics, d. H. different transducer transducer characteristics and provides the necessary organization of the measurement cycle, including waveform definition, ultrasound pulse transmission, waiting a pre-specified period of time to return the echo, and digitizing and forwarding it with additional data.

A directly connected analog signal component takes over the task of converting the transmit and receive pulse between the analog and digital signal form as well as filtering and amplifying the very weak signals of the ultrasonic echoes, especially in the case of thin-film transducers.

Following the solution proposed according to the invention, only the electronics which are absolutely necessary for the excitation of the tranducer and the detection of the echoes are placed at the location of the measurement. The collected information is transmitted in digital form via cable or wireless to the corresponding other components of the measuring system, which may be spatially separated from the location of the measurement, while the evaluation of the transmitted information may take place both spatially and temporally separate from the data acquisition.

In addition to individual measurements with a corresponding external trigger, the ultrasonic measuring system can also be used to control repeated or automatic measurement series, up to a largely autonomous execution of predefined measuring cycles, whereby a connection to the external data analysis and control system does not always have to be guaranteed.

It is advantageous to attach the data acquisition unit of the ultrasonic measuring system proposed according to the invention as close as possible to the location of the measurements. Since this does not allow the installation situation or the accessibility in all cases, For example, the electrical analog signal of the transmit pulse and the signal of the echo can be routed through variable length cables. Due to the finite signal speed in the cable, there is a not inconsiderable contribution to the total transit time of the pulse, which must be separately determined and subtracted in order to conclude on the pure ultrasonic transit time of the ultrasonic pulse in the connecting element. In conjunction with the hardware, the ultrasound measurement system must provide the necessary method to directly measure this so-called cable runtime or to assume an externally measured cable runtime as a numerical value and to correctly use it for the ultrasonic transit time measurements.

Advantageously, the data acquisition unit of the ultrasonic measuring system can be integrated into a transportable housing for universal use in a wide variety of application areas. It is preferably a combination of a specially designed analog electronics in conjunction with a digital part for control. By virtue of the embodiment of the separation of the data acquisition unit from the data evaluation unit as proposed according to the invention, handling is substantially more advantageous primarily because of the possible miniaturization and also the force measurement rate and power consumption. The data acquisition unit can be used much more flexible and possibly also meet extended guidelines, in particular requirements for explosion safety. In the ultrasonic measuring system proposed according to the invention, a strict separation of the measurement of data and of the data processing is realized, so that the possibility exists of operating a plurality of data acquisition units on only one data evaluation station (eg via Ethernet or WLAN). The data acquisition unit remains invisible to the user, works almost completely maintenance-free and can be optimized due to its largely low level of complexity to the actual measurement process - primarily with regard to speed.

In summary, the data acquisition unit of the ultrasound measuring system proposed according to the invention with a strict separation of data acquisition and data processing is characterized by a very high degree of transparency towards the user. The measuring system is extremely low maintenance because there are only a few configuration parameters. Furthermore, there is a simple update option via Ethernet or WLAN. The data acquisition unit generates a detailed error report analysis and is characterized by a high data acquisition speed and low power consumption with a high force measurement rate. Furthermore, the data acquisition unit of the inventively proposed ultrasonic measuring system is extremely easy to handle, which is not least due to a small and compact housing.

In the solution proposed according to the invention for an ultrasound measuring system, the data acquisition unit comprises the connection to the ultrasound transducer as an analogue working part, while the digital component is used for data processing of the organization of the data acquisition unit and furthermore represents the interface to the user or user.

The analog operating part of the hardware component can be divided into the two signal paths of the transmission pulse of the data acquisition unit to the transducer and the echo signal from the transducer to the data acquisition unit. Both signal paths necessarily use the same signal cable outside the data acquisition unit, in particular designed as coaxial cable. The effort involved in connecting the data acquisition unit to the transducer is limited to the absolute minimum. Special requirements are made especially for the generation and transmission of the waveforms to and from the transducer. The high dynamics of the expected echo signals in the waveform transmission is determined by different transducer designs, the (for the measurement of such small forces) very high accuracy requirement for the transit time measurement and the sometimes very strong influences of the passing material.

It is desirable to carry out the signal transmission as noise-free as possible, with high gain, undistorted, independent of frequency within the excited bandwidth of the transducer, phase-stable and largely without time uncertainty with high absolute time resolution.

The digital hardware component is used to time control and regulate the analog hardware component and the total ultrasonic transit time measurement cycles. All necessary parameters for the definition of the pulse waveform and the sequence control are available at the time of a measurement. This is ensured by the software of this component. The user of the ultrasonic measuring system proposed according to the invention is in contact with this component in order to initiate ultrasonic transit time measurements and to obtain their results in the form of digitized echoes and further information. For further processing of the measurements, an export and transfer of the digitized echo signals together with all other parameters relevant for the measurement to a downstream, spatially separated from the data acquisition unit data processing unit is provided.

Since temperature changes also change the length of connecting elements and thus ultrasonic transit times, a separate synchronized measurement of the temperature during the propagation of the ultrasound pulse is required. This is done via a high-precision temperature-sensitive resistance element, such as a Pt100 sensor.

Although the data acquisition unit should be placed as close as possible to the location of the runtime measurements, this optimal situation can not always be chosen. Therefore, there arises a need to conduct the electrical analog signal of the transmission pulse and the signal of the echo through cables of variable length. Because of the finite signal speed within the cable, there is a not inconsiderable contribution to the total transit time of the ultrasound pulse, which must be separately determined and subtracted in order to determine the pure ultrasonic transit time in the connecting elements. The digital hardware component provides a way to directly determine the duration of the electrical signal in the connected cable and export it via the user interface so that it can be subtracted from the total measured transit time.

On the hardware side, a high-precision quartz oscillator and external temperature sensors are used for the two measured variables, transit time and temperature. These must in turn be calibrated at regular intervals with corresponding reference standards in order to ensure the functionality and correctness of the measurement results. For this purpose, corresponding signal inputs are provided.

To carry out an ultrasonic cycle, the ultrasound measuring system proposed according to the invention, with the combination of digitally operating and analog hardware components, performs the following tasks:
An analog, complex, time-limited electrical pulse waveform is generated. Optionally there is the possibility of a variable amplification of the generated analog signal for exciting ultrasound transducers of various types. There is a transfer of the generated electrical waveform to the location of the transducer. After transmitting the ultrasound pulse, the output signal chain is switched off to avoid unnecessary interference in the received signal chain. After a predetermined variable definable period of time ultrasonic echoes are detected. At the same time, the determination of the temperature of the connecting element during the ultrasonic pulse propagation takes place in the material of the component to be measured.

This is followed by bandpass filtering and amplification of the very weak echo signals of the transducers, which now operate as receivers. This is followed by a digitization of the amplified input signal over a predetermined time range after the transmission of the pulse, and optionally its averaging over many echoes to increase the signal-to-noise ratio.

Finally, a complete time series, i. H. a measurement cycle along with other complementary data over a data transfer channel (eg Ethernet) forwarded to a PC-like system for further data analysis.

Short description of the drawing

With reference to the drawing, the invention will be described below in more detail.

It shows:

1 the schematic structure of the inventively proposed ultrasonic measuring system,

2 a representation of the components of the data acquisition unit,

3 a detailed representation of the components contained in a pulse transmitting module and an echo receiving module of the data acquisition unit.

variants

The representation according to 1 is a schematic representation of the inventively proposed ultrasonic measuring system.

The representation according to 1 is a connecting element 10 to be taken, in which it is shown in the illustration 1 is a screw. Alternatively, the connecting element 10 also be represented by a rivet, a bolt or other connection component. 1 further shows that at the head of the connecting element 10 a transducer 12 is arranged. In the transducer 12 it may be one formed by thin film technology or another commercially available ultrasonic transducer ( 12 ).

The connecting element 10 includes a shaft 14 , To the shaft 14 of the connecting element 10 - designed as a screw - closes a threaded section 16 at. About the transducer 12 is the connecting element 10 as shown in 1 with a data acquisition unit 20 connected with integrated analog / digital converter.

The cable connection 18 between the transducer 12 and the data acquisition unit 20 is preferably given by a coaxial cable. The cable connection 18 between the data acquisition unit 20 and the transducer 12 is not mandatory. Allow the installation conditions of the connecting element 10 so the data acquisition unit can 20 directly on the top of the transducer 12 be put on. This allows the electrical coupling of the transducer 12 directly to the data acquisition unit 20 respectively. Should this be the installation conditions of the connecting element 10 On the other hand, it is not possible to optionally use the transducer 12 on the top of the connecting element 10 with measuring module 20 over the cable connection 18 to connect and in this way the excitation signals to the transducer 12 to conduct and the echoes received on the particular designed as a coaxial cable connection 18 to the data acquisition unit 20 transferred to.

Via a wired or wireless connection 22 which is, for example, Ethernet or WLAN or the like, is the data acquisition unit 20 in turn connected to a data processing enabling system, in particular a PC, which serves to evaluate the data, indicated in Figure by the data evaluation unit 24 ,

The representation according to 2 are components of the data acquisition unit refer.

As 2 shows stands the data acquisition unit 20 over the cable connection 18 with the connecting element 10 , trained here as a screw, in conjunction. The data acquisition unit 20 includes a pulse transmission module 26 , with which an ultrasonic pulse via the cable connection 18 and the in 2 not shown transducer in the connecting element 10 is initiated. Furthermore, the data acquisition unit comprises 20 an echo receiving module 28 , which - also via the cable connection 18 - from the connecting element 10 over the in 2 not shown transducer the echo of the pulse transmission module 26 emitted ultrasonic pulse receives. Furthermore, in the data acquisition unit 20 according to the schematic representation according to 2 a control module 30 as well as a communication module 32 contain. About the communication module 32 be over the wireless connection 22 Correspondingly prepared data for the data evaluation unit 24 transmitted. The control module 30 assumes the logical and temporal sequence control of all components involved in the measuring process. In particular, in the control module 30 a correction of the duration of the ultrasonic pulse in the connecting element 10 by the maturity portion, which depends on the duration in the cable connection 18 eliminated. Furthermore, it takes place in the control module 30 also a temperature compensation of the measured ultrasonic pulse transit time through the connecting element 10 ,

Furthermore, the consideration of the influence of temperature on the ultrasonic roller transit time takes place within the connecting component formed as a screw 10 in the control module 30 because this is equipped with a corresponding algorithmic intelligence. Corresponding to the pure ultrasound signal transit time in the connecting element 10 Corrected data is sent via the communication module 32 and the wired or wireless connection 22 to the data evaluation unit 24 - indicated here by a laptop - transmitted.

The representation according to 3 are individual components of the in 2 shown Pulssendemoduls and the in 2 shown echo receiving module of the data acquisition unit.

Out 3 it turns out that the pulse transmitting module 26 analogous to the representation according to 2 over the cable connection 18 with the connecting element formed here as a screw 10 with the interposition of an in 3 not shown Transducers is connected. The pulse transmission module 26 includes an output amplifier with which the ultrasonic pulse by means of the cable connection 18 in the connecting element 10 is coupled. In addition, the pulse transmitting module includes 26 as shown in 3 a pulse shape memory 38 in which different types of ultrasonic pulses are imaged in digital form. Between the pulse form memory 38 and the output amplifier 34 is a digital to analogue converter 36 provided, which the present in digital form ultrasonic pulses in the pulse form memory 38 are stored, converted into corresponding analog signals, by means of the output amplifier 34 in the cable connection 28 to the transducer 12 of the connection component 10 be coupled.

That in the data acquisition unit 20 included echo receiving module 28 includes an input amplifier on the input side 40 with which the from the connecting component 10 , about in 3 not shown transducer 12 and the cable connection 18 amplified ultrasonic echoes are amplified. The input amplifier 40 of the echo receiving module 28 is a bandpass filter 42 downstream; this in turn an analog / digital converter 44 , About the analog / digital converter 44 The analogue echo signals are converted into digital signals stored in an ultrasonic echo memory 46 of the echo receiving module 38 the data acquisition unit 20 get saved.

From the 1 and 2 it shows that the connection 22 for example, as a wireless connection between the data acquisition unit 20 and the data evaluation unit 24 is trained. As a wireless connection is for example a wireless connection in question. Alternatively, the connection may be 22 be designed to be wired and designed, for example, as an Ethernet connection.

The inventively proposed ultrasonic measuring system as above based on the 1 to 3 described, in a further advantageous application can also be used to make a Mehrfachverschraubung, so for example on a flange. In the context of a multiple screw connection, for example, four, six or a different number of fasteners 10 for example, screws bolted to a hub, for example to a wind turbine motor and to a hub of a wind turbine rotor. For this purpose, usually several simultaneously operated tightening tools are used, in each of which a data acquisition unit 20 As described above is integrated and the resulting overall system to several tightening tools each with integrated data acquisition units per se is operated via a control loop such that a Mehrfachverschraubung simultaneously on all fasteners 10 can be generated with defined biasing forces.

LIST OF REFERENCE NUMBERS

10

connecting element

12

Tranducer

14

shaft

16

threaded portion

18

cable connection

20

Data acquisition unit

22

wireless connection

24

data evaluation

26

Pulse transmitter module

28

Echo reception module

30

control module

32

communication module

34

output amplifier

36

Digital / analog converter

38

Pulse shape memory

40

input amplifier

42

Bandpass filter

44

Analog / digital converter

46

echo memory

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4225035 A1 [0002]
• DE 4232254 A1 [0002]
• DE 102004038638 [0002]
• DE 102009060441 A1 [0003, 0012]

Claims (15)

Ultrasonic measuring system with a data acquisition unit ( 20 ), and a transducer ( 12 ) for coupling an ultrasonic pulse into a connecting element ( 10 ) and for coupling out an ultrasonic pulse echo from the connecting element ( 10 ), characterized in that it comprises a data acquisition unit ( 20 ) provided by a data processing unit ( 24 ) structurally separated and by means of a wired or wireless connection ( 22 ) is coupled with this. Ultrasonic measuring system according to claim 1, characterized in that the data acquisition unit ( 20 ) with the necessary analogue and digital components to excite the transducer ( 12 ) and is equipped for echo reception and has a smallest possible design. Ultrasonic measuring system according to claim 1, characterized in that the compound ( 22 ) is wired or wireless. Ultrasonic measuring system according to claim 1, characterized in that the data processing in the data processing unit ( 24 ) spatially and temporally separated from the excitation of the Tranducer ( 12 ) and echo reception. Ultrasonic measuring system according to one of the preceding claims, characterized in that the data acquisition unit ( 20 ) is placed in close spatial proximity to the measuring location, in particular directly on and firmly connected to a connecting element ( 10 ) without further cable connection to the transducer ( 12 ). Ultrasonic measuring system according to one of the preceding claims, characterized in that a plurality of independent data acquisition units ( 20 ) with a single central data processing unit ( 24 ) by connections ( 22 ) are connected. Ultrasonic measuring system according to one of the preceding claims, characterized in that the data acquisition unit ( 20 ) after appropriate configuration independently at regular or irregular time intervals, the state of the connecting element ( 10 ) automatically detects and passes on the information. Ultrasonic measuring system according to one of the preceding claims, characterized in that the data acquisition unit ( 20 ) as part of a manual inspection device together with another component for identifying the connecting element ( 10 ) how a barcode reader or camera is combined for simplified and error-free remeasurement and monitoring of the stress state of connecting elements ( 10 ). Ultrasonic measuring system according to one of the preceding claims, characterized in that the data acquisition unit ( 20 ) directly into the connecting element ( 10 ) is integrated, so that from the connecting element ( 10 ) with controllable transducer ( 12 ) for ultrasonic measurement an active connection element ( 10 ), which determines its own state independently and to a data evaluation unit ( 24 ) transmitted. Ultrasonic measuring system according to one of the preceding claims, characterized in that the data acquisition unit ( 20 ) directly in the production of the connecting element ( 10 ) is integrated into this and so an active connection element with sensor characteristic already arises during manufacture. Ultrasonic measuring system according to one of the preceding claims, characterized in that the data acquisition unit ( 20 ) is integrated with or connected in a function-expanding manner with tightening tools in order to fasten fasteners ( 10 ) ultrasonically controlled with defined preload force. Ultrasonic measuring system according to one of the preceding claims, characterized in that in a plurality of simultaneously operated tightening tools each have a data acquisition unit ( 20 ) is integrated and the total system thus obtained is controlled via a control loop so that a multiple screw simultaneously on all fasteners ( 10 ) takes place with defined preload forces. Ultrasonic measuring system according to one of the preceding claims, characterized in that the data processing unit ( 24 ) is integrated as a separate digital system in the data recording unit, so that the mechanical stress state of the connecting element ( 10 ) directly without further external evaluation units read by the user. Use of the ultrasonic measuring system according to one of claims 1 to 13, characterized in that this is used for life monitoring of components, in particular steel beams or hydraulic components and the like. Method for carrying out ultrasonic measurements in connecting elements ( 10 ) with an ultrasonic measuring system according to one or more of the preceding claims, with the following method steps: a) generating an analog complex time-limited electrical pulse waveform, b) transmitting the generated pulse waveform to the location of the transducer ( 12 c) switching off an output signal chain after transmission of the pulse to avoid unnecessary interference in a received signal chain, d) detecting an ultrasonic echo after a predetermined variable period of time, e) determining the temperature of the connecting element (FIG. 10 ) at the time of ultrasonic pulse propagation in the connecting element ( 10 f) bandpass filtering and amplification of the echo signals of the transducers working as receivers ( 12 g) digitizing the amplified input signal for a given time period after transmitting the pulse and / or averaging it over a number of echoes and h) forwarding a complete time series together with further complementary data via wired or wireless connections ( 22 ) to a data evaluation unit ( 24 ).

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