LT5493B - Method and device for threaded joint tightening degree defining - Google Patents

Abstract

This method is intended to use in machines, buildings, different technical equipment, where threaded joints are applied. This invention is intended to measure tightening of responsible threaded joints during assembling process and exploitation period. Such joints are used in machines and transport equipment construction and engines, buildings, etc. Presented here method of defining threaded joints tightening degree is based on statement, that tightened by bolts or pins details assumed to be a vibration system, where bolts or pins are vibrating relative to clamped details. Dynamical characteristics of such system are defined from vibration sensor signal, given from transient vibration process between bolt surface and clamped detail, excitedby hammer or similar device with shock (force impulse) sensor (in case, when shock duration is significant). Given bolt (pin) vibrations and shock process signal are transmitted to analyzer, where desired dynamical characteristics are calculated. Defining tightenin

Description

1. Technical field to which the invention relates

The invention relates to machines, structures, various technical devices, etc., in which various threaded joints are used. The present invention relates specifically to the measurement of the tightening of the responsible tightening threads during assembly and operation. Such connections are used, for example, in machinery, transport equipment, their construction and motors, boilers, turbines, responsible structures and the like.

The object of the invention is to provide a new non-destructive control method for controlling the tightening of threaded joints during the manufacture and operation of said devices.

For the purposes of this Article, "bolted joints" means joints of two or more parts, assemblies and technical units which are pressed together by means of dedicated surfaces (hereinafter referred to as "joints"), where the links joining these joints are head bolts (studs) or studs; the following are used for this compression:

• head bolts, nuts, and threaded through holes in threaded fittings and tightened with nuts;

• screws with head, screwed into one of the outermost fittings and slotted through the holes provided for this purpose in the other fittings or piece;

• Screw in the studs into one of the outermost parts, pierce through the holes made in them in the other parts or in the part and tighten with nuts from the ends of the studs that are not screwed into the part;

• Threads through the threaded holes in all parts to be clamped together are tightened with nuts at both ends.

Washers may be placed under the bolt heads or under the nuts. The shape (design) of the bolt heads or nuts shall correspond to that of a clamping tool, such as a wrench, when used externally (hexagonal head) or another tool used from the inside or a possible surface of the head.

The closest method for determining the size of a threaded joint and the device designed for this purpose is a method of screwing or bolting a threaded joint and measuring it by measuring the elongation of the bolt or stud by ultrasonic wave (http //: www .surebolt.com).

2. State of the art

The following techniques for controlling and measuring threaded joints are known (PemeTOB / H., ΡΙββηοβ AC, OaaeeB B.3. HanejKHOCTb Maumu.- MocKBa: Buicuiaa inKOJia, 1988; Roloff / Matek. Machinenelemente. 16 Auflage. 2003 et al.). :

1) torque measurement of bolt or nut using a torque wrench;

2) measuring the angle of rotation of the bolt or nut;

3) estimating the size of the gap at the point of contact of the compressible parts;

(4) Measurement of the clamping axial force acting on the bolt or stud;

5) measurement of the elongation of the bolt or stud during tightening.

Methods 1, 2 are not accurate and reliable because the measurement results are determined by frictional forces occurring in the threaded joint. The accuracy of the aforementioned measuring methods is 15 ^ -30%, which is why for many responsible devices such accuracy is insufficient.

The method of headings 4 to 5 where the distance between the surfaces of the fittings is ultrasonic, the force of which is obtained when there is no gap between the fittings (for example, SU 1737173 Al). In order to measure the size of the clamping fitting in this way, it is necessary to access the surfaces of the fittings to measure the ultrasonic passage; special sophisticated equipment is also required and the measurement results are not stable enough.

A special design washer or bolt is required when measuring the bolt or stud axial force (SU 1679077 Al) using the method in position 4. The above condition limits the scope of the method.

The exact size of the clamping can be determined in the manner described in position 5, by measuring the elongation of the bolt or stud that occurs during tightening. This is done using special design screws (SU 1564417 Al), and tensimetry methods are used (KyapHBueB B.H. JeeTajm MainnH.-JIeHHHrpan: MainHHocTpoeHHe, 1980).

Using another known method of measuring the elongation of screws or studs that occur during tightening, which can be considered as closest to ours, does not require the use of special design screws or studs. In this method of measurement, the elongation of a bolt or stud is determined by the difference between the phases of the ultrasonic wave missed through the bolt (or stud) and bounced off its (or its) end. The disadvantages of this method are as follows:

1. It is necessary to know the true dimension of each bolt or stud of the same nominal dimension in its untightened state, since the actual dimension of the bolts or studs of the same nominal dimension may vary within the permitted manufacturing tolerances. This setting of all bolt or stud lengths is technologically inconvenient.

2. Ultrasonic waves are scattered by bolt material, making it difficult to measure the length of long bolts or studs.

3. This method requires the use of sophisticated hardware to measure bolt or stud tightening.

3. Gist of the Invention

The method of determining the size of the threaded joint in the present invention differs from the methods 1-5 in Section 2. The method of determining the size of the threaded bolt tightening here allows for the simplest and most accurate determination of the size of the threaded bolt bolt during assembly and operation, without the use of a specially designed bolt stud washer and using modern digital technology. This method is based on the fact that screw or pin tightened threading can be considered as a mechanical oscillating system in which each bolt or pin turns to the tightened parts when excited. The contact stiffness and friction of the joints in such an oscillating system, as well as their dynamic properties, depend on the size of the screws or studs tightening this joint. Impact load (a short-term impulse of force on the end of a screw or stud screw along the bolt or stud axis) causes their quenching free oscillations (transient oscillation) in relation to the fasteners. The characteristics of these oscillations (frequencies, damping velocity, etc.) depend on the size of the clamping screw. Such low-intensity oscillations can be considered linear because they occur in a force-tightening coupling environment that is approximately linear. Changing the size of the threaded joint tightening also changes the contact stiffness and friction of the oscillating system, but its oscillations may also be considered linear, but they will be different from the former because of the otherwise tightening environment. In this case, it is known that having the analytical-numerical expressions of linear transient oscillation process and knowing the nature of transient load, all dynamic characteristics of the system under study are obtained: amplitude-frequency, phase-frequency, amplitude-phase characteristics, frequency and amplitude spectra of resonant vibrations function between excitation force and measured vibrations, etc. (e.g. Λορφ P., Bmnon P. CoepeMeHHbie cHcreMbi ynpaBjieHHH. Περ. c βηγ.ι. MocKBa: JlaoopaTopmt 6a3OBbix 3HaHHH. 2002; BnSpaųHH b τεχΗηκε: tom

YY. reHKHHa. - MocKBa: ManiHHOCTpoeHHe. 1981 et al.). Which of these characteristics is used depends on the particular case and design of the joint being investigated. The process of obtaining these characteristics is simplified and the accuracy of the data obtained is enhanced if the impact load could be considered instantaneous (in the form of a force pulse). Such assumption is possible in most of the cases presented here, if the minimum frequency period required for the measuring process of the screw (stud) oscillation frequencies is significantly longer than the duration of the impact load.

By processing the data obtained during the measurement, the dynamic characteristics of the threaded joint are determined, depending on the size of the joint tightening. No special threaded construction is required for this type of screw-in tightening. This method requires hardware and a computer with appropriate software to measure the nature of the excitation force and the vibrations of the oscillating system (transient oscillatory process) by a sensor, to convert the digital signal into a digital code. Determination of dynamic characteristics is simplified when the excitation force can be considered as an instantaneous impulse and then does not need to be measured. The present invention provides specific cases where the same portion of a bolt or stud (bolt head or end, end of a stud) is used to measure the oscillation of the bolt (s) and to apply the force causing the oscillation, although this force may be added elsewhere her) on the spot. With the recent excitation, the method of clamping and the apparatus needed to perform it remain unchanged, but the magnitude of the vibrations to be measured and their accuracy may be reduced.

In order to measure the size of the screw connection, it is necessary to know the dynamic characteristics of the properly tightened screw and compare them with the dynamic characteristics of the test thread. The manufacturing errors of precision made threaded joints do not determine the nature of the dynamic characteristics of these joints, since the responsible threaded joints are accurate.

It is easier to determine the measured tightening of a threaded joint using its dynamic characteristics than to measure the length of each bolt (stud) using an ultrasonic device (see the disadvantages of the ultrasonic method above). Our proposed method of tightening the threaded joint requires modern, simple and compact equipment that does not require any special threaded construction.

The effectiveness of the presented method is confirmed by an experimental study, the results of which are approved at the international scientific conference Mechatronic Systems and materials MSM

2005 and 2006. will be published in the already published "Application of

Freuuency Method for Defining Threaded Joint Tightening Degree.

3.1. Disclosure of Invention

The size of the clamping screw is determined using the "bolt (stud) and the surface of the clamp" dynamic vibration characteristics of the oscillating system, which are determined individually for each screw (stud). The required amount of tightening shall be determined by comparing the obtained dynamic characteristics of the screw (stud) or only a part thereof with the characteristics of the properly tightened screw (stud).

The aforementioned dynamic characteristics are obtained by measuring with a vibration sensor the transient oscillation of the bolt (stud) and the surface of one of the clamping elements caused by the impact of a hammer or similar inert, and of the impulse of the excitation force ( when the impact is not considered a force pulse). The resulting bolt (pin) oscillations and excitation force signals through the converter are analog - the code is transmitted to a computer, which determines the required dynamic characteristics.

4. Description of the drawings

A method for determining the size of a threaded screw and a device for realizing it is shown in FIG. 1, 2, 3, 4, 5, 6. In each case, only one bolt or one pin is shown.

FIG. 1 shows a diagram of the measurement of the vibration of a screwed coupling and the equipment needed to measure them when the coupling is tightened by a head screw which is screwed into one of the peripheral clamping parts and the vibrations of the screw are decided by its head vibrations.

Fig. 2 shows a node different from that of fig. 1 in that it uses a screw with a head and a nut, and when the vibrations of the bolt are judged by the vibrations of its head.

FIG. The case illustrated in Fig. 3 differs in that about fig. In Fig. 2, the vibrations of the head bolt are solved by the vibrations of the screw end of the bolt opposite to the head.

FIG. 4 shows the case from FIG. The assembly of Fig. 1 differs in that it shows a joint where it is tightened by studs screwed into one of the clamping members and the oscillations of the stud are judged by the oscillations at the end.

FIG. 5 shows a case which, from FIG. The difference in Figure 4 is that the joint shown here is screwed into a stud with nuts on both ends.

FIG. 6 shows a case where FIG. The units 1, 2, 3, 4, 5 use a laser to measure the oscillation of the bolt or stud.

FIG. 1 shown parts: 1 - bolt; 2 - Measuring surface of screw head; 3 washer; 4, 5 - screw 1 screwed parts; 6 - sensor for measuring vibrations between screw head surface 2 and part 4; 7 - measuring nozzle of sensor 6; 8 - sensor 6 support; 9 support bracket assembly 8 (magnetic, screw or other device connecting the support 8 to the fitting 4); 10 - Hammer or similar device for exerting a vibrating force; 11 - force pulse recording sensor incorporated in device 10; 12 - the calibrator of the initial continuous signal amplifiers of sensors 6 and 11; 13 - analog / digital converter; 14 - Computer; Δ is the distance between the sensor tip 7 and the measuring surface 2.

FIG. 2 shows a part different from FIG. 1 parts shown: 15 - nut.

FIG. 3 shows a portion different from FIG. The parts shown in Figures 1 are: 16 - Screw surface 1 of the screw used to measure its vibration.

FIG. 4 shows parts different from FIG. 1 and FIG. 3 parts shown: 17 - pin; 18 - stud 17 end surface.

FIG. 5 is not different from FIG. 1 and FIG. 4 parts shown.

FIG. 6 shows parts different from FIG. 1, 2, 3, 4, 5 parts: 19 - laser vibration meter for surfaces 2, 16, 18; S3 - laser beam; δ is the distance of the laser meter 19 from the measuring surface (δ f 0).

5. Description of the practice of the invention

5.1 General

The proposed method of determining the tightening of threaded joints is realized by a slight short-term impact (force impulse) through a bolt or pin, inducing free oscillations (transient oscillation) between the bolt (pin) and the part being tightened therewith. Vibration and force sensors record continuous bolt (stud) vibration and force pulse signals, amplified and calibrated, digitized and transmitted to a computer for further processing and storage. In the computer, the data received from the sensors is processed and the oscillating system screw (pin) is a tightened detail frequency characteristic, the nature of which determines the amount of screw tightening for each screw (pin).

5.2. Description of the method and intended installation

The tightening of the threaded joint shall be determined and controlled by measuring separately the tightening of each screw (stud). Using FIG. 1 shows a diagram.

Ί is measured by screw 1 connecting parts 4 and 5 (tightening having transient vibrations of the measuring surface 2 of its head relative to the part 4. Vibrations are caused by a hammer 1 by striking the bolt 1 with a low intensity and measured by vibration sensor 6 whose measuring nozzle 7 measures either through a small air gap Δ when using a capacitive sensor (Δ = 0.0l-e-0.1 mm) or touching the measuring surface using, for example, an induction sensor (then Δ = 0). surface 2, or, if appropriate, another part of bolt 1. The continuous signal Si defining the free extinguishing oscillations of the surface 2 caused by the impact is transmitted to the amplifier 12, which also transmits an oscillating shock signal s ₂ obtained from the force incorporated in the hammer 10. (tensometric, piezoelectric, etc.) measuring sensor 11. In amplifier 12 s amplified and calibrated continuous signals are transmitted to an analog-to-code converter 13. It converts the analog signal into a digital one and transmits it to a computer 14, which calculates the dynamic characteristics of the bolt (tightening) (amplitude-frequency, amplitude-frequency, amplitude-phase, frequency-phase characteristics, spectra of resonant frequencies, phases and amplitudes, transmission function between excitation and measured vibrations, etc.). Which of the dynamic characteristics is appropriate to use is decided separately for specific measurement cases. The values obtained for the bolt (for the determination of the amount of tightening) are compared with those of the properly tightened bolt obtained in the same way. By comparing these characteristics, the tightening of the test bolt is determined by reference to the reference bolt. When the vibration force is about 10 + 15 shorter than the maximum frequency the force is considered as pulse (force pulse) In which case sensor 11 and its signal s _{2 are} not used.

Screw-in threaded fitting is measured in the same way as screw fitting, using the same hardware. In this case, the vibrations are measured at the surface 17 of the end of the stud 16 and are excited by the hammer 10, striking through that surface or, if appropriate, through another portion of the stud. The measurement of the oscillation of the bolt or stud by the laser 19 beam S3 bounced to one of the measuring planes 2, 16 or 18, respectively, is shown in FIG. 6. The distance δ of the laser 19 from the measuring surface may be significantly greater than the distance Δ. The method of measurement and the equipment used are the same except for laser replacement of the vibration sensor.

Claims (6)

1. A method of determining the size of a threaded coupling, comprising machine static pressurized couplings used in hardware assemblies by means of screws, nuts and nuts, each of which is determined by the size of each coupling bolt. or the amount of clamping of the stud determined by the dynamic characteristics of the screw / stud - stud component of the oscillating system. 2. A method for determining the magnitude of a thread coupling clamp according to claim 1, characterized in that the dynamic characteristics used are: amplitude-frequency, phase-to-frequency, amplitude-to-phase characteristics, resonant frequency-phase amplitude spectra, oscillating system transfer function. 3. A method for determining the size of a threaded joint in accordance with claim 1, characterized in that the dynamic characteristics are obtained from the relative transient oscillations between the bolt (stud) and the surface of the bolted parts (transient quenching process) and then triggered by a hammer or similar device. determining the aforementioned characteristics after processing vibration and shock signals or vibration signals only. 4. Method for determining the magnitude of the clamping clamp according to any one of claims 1, 2, 3, characterized in that, when the impact force is at least 10 ... 15 times less than the maximum frequency of the vibration system of the test subjects. are obtained by processing only the vibration signal of this system. 5. A device for determining the magnitude of a threaded joint, characterized in that the device comprises a sensor for measuring the surface of the bolt or stud vibrations relative to the surface of the bolt, or a laser for detecting such vibrations, magnetically, bolted or otherwise rigidly attached to the bolt. , measuring surface-to-surface oscillation of a screw or pin, a "analogue code" of a hammer or similar device with a built-in impact sensor, a continuous screw or pin oscillator and a hammer impact converter converting analogue signals into a digital signal sensor, software for determining frequency characteristics from vibration and force sensing signals. 6. A device for determining the size of a threaded joint in a different manner. the apparatus consists of a sensor for measuring the vibration of a bolt or stud vibration relative to the surface of a clamping member or a laser which senses these vibrations, which is magnetically, bolted or otherwise rigidly attached to a clamping member for measuring the vibration of a bolt or stud "analog - code" of a device, continuous screw or pin oscillator signal converter, which converts the sensor into analogue signals into a digital code on a computer having the appropriate software for determining the dynamic characteristics of a vibration sensor signal