RU2773228C2 - Method for controlled assembly of threaded connections and apparatus for implementation thereof - Google Patents

Abstract

FIELD: machine tools.

SUBSTANCE: group of inventions relates to an apparatus for controlled assembly of parts by tightening a threaded connection and to a method for implementation thereof. The apparatus comprises a striker, an anvil, a spindle, a wrench, a nut, a bolt, a comparison apparatus connected with a clock pulse generator and a comparator, an indicator, a vibration sensor configured to be secured on one of the assembled parts of a threaded connection, connected with a low-pass filter. The apparatus is equipped with a pin, a concentrator, a frequency-lowering element and a piezoceramic converter clamped by the pin between the concentrator and the frequency-lowering element, wherein the low-pass filter, comparator, comparison apparatus and indicator are connected in series, and the clock pulse generator is connected to the second input of the comparison apparatus. The method includes additional striking and analysis of the pulse characteristics of damped vibrations, wherein the tightening is ended when differences appear in the values of the half-periods of the analysed oscillations, wherein the oscillations passed through the threaded connection are transmitted to the vibration sensor and converted into an electrical signal, transmitted to the input of the low-pass filter, impact-rotational pulses are applied and the threaded connection is tightened simultaneously, wherein the signal from the low-pass filter is transmitted through the comparator to the comparison apparatus and the indicator, signals from the generator are received at the second input of the comparison apparatus.

EFFECT: increase in the accuracy of controlling the tightening of threaded connections.

2 cl, 1 dwg

Description

The invention relates to the field of mechanical engineering and can be used in the controlled assembly of threaded connections.

A known method for assembling threaded connections, including pre-tightening by applying torque to the movable element of the threaded connection and exposing the elements of the threaded connection and assembled parts to ultrasonic vibrations and final tightening with quality control of the connection (A.S. No. 1505770, IPC V25V 21/00, 09/07/89 Bulletin No. 33).

The disadvantage of this method is the low reliability of the connections.

The closest in technical essence is the method of controlled assembly of a threaded connection, which includes pre-tightening the threaded connection by applying torque to the movable element of the threaded connection and exposing the elements of the threaded connection and assembled parts to ultrasonic vibrations, converting mechanical vibrations into an electrical signal and determining the quality of tightening by analyzing oscillations (RF Patent No. 2414339, IPC V23R 19/06, 03.20.2011. Bull. No. 8).

The disadvantage of this method is the low accuracy of the control tightening threaded connections.

It is also known a device containing a striker, an anvil, a spindle, a key, a nut, a bolt, a comparison device connected to a clock pulse generator and a comparator, an indicator, a vibration sensor attached to one of the assembled parts, which is connected to a low-pass filter (A.s. USSR No. 1793366, IPC G01N 29/04, 1993, Bull. No. 5).

The disadvantage of the device is the low accuracy.

The technical result of the proposed invention is to improve the accuracy of control tightening threaded connections.

The technical result is achieved by the fact that in the method of controlled assembly of threaded connections, which includes pre-tightening the threaded connection by applying torque to the movable element of the threaded connection and exposing the elements of the threaded connection and assembled parts to ultrasonic vibrations, converting mechanical vibrations into an electrical signal and determining the quality of tightening by analysis of oscillations, additionally strike and analyze the impulse response of damped oscillations and finish tightening when differences appear in the values of the half-periods of the analyzed oscillations.

Also, the technical result is achieved by the fact that in a device for controlled assembly of parts by tightening a threaded connection, containing a striker, an anvil, a spindle, a key, a nut, a bolt, a comparison device connected to a clock pulse generator and a comparator, an indicator, a vibration sensor mounted on one of assembled parts, which is connected to a low-pass filter, a pin, a concentrator, a frequency-reducing element and a piezoceramic transducer are additionally introduced, which is clamped by a pin between the concentrator and the frequency-reducing element, in addition, a low-pass filter, a comparator, a comparator and an indicator are connected in series, and to the second input comparison device is connected to a clock generator.

One of the most advanced methods of calibrated tightening used in practice is the method by which tightening is carried out until the yield strength of the bolt material is reached, which makes it possible to achieve the maximum effect of tightening and make the most full use of the strength properties of the threaded connection (Gusakov B.V. Domestic and foreign methods and means of calibrated tightening of threaded connections // Assembling in mechanical engineering, instrument making, No. 9, 2003, pp. 12-24). Torque control, based on reaching the tightening force at the elastic limit point of the material of the threaded parts, is practically independent of friction, allows the use of smaller fasteners and lower accuracy grades, and ensures the minimum variation in the tightening force.

The use of ultrasonic vibrations makes it possible to control the state of formed contact bonds directly in the assembly process, and in the process of forming contact bonds under the action of additional ultrasonic vibrations, compensation of disturbing factors occurs, associated with a spread in the geometric parameters of threaded joints, mechanical properties of the material, friction coefficients, microgeometry of the parts to be connected (Increase performance of threaded connections by applying ultrasound during processing and assembly: monograph / B. L. Shtrikov, V. V. Golovkin, V. G. Shuvaev, I. V. Shuvaev. - M .: Mashinostroenie, 2009. - 125 p.) .

Ultrasonic mechanical vibrations are used simultaneously to perform the following useful functions: firstly, friction is reduced, distortions and deformations are eliminated during the screwing process, and the plasticity of the material is increased; secondly, mechanical oscillations are a source of diagnostic information about the parameters of the dynamic quality of an oscillatory mechanical system. The additional introduction of mechanical vibrations into the formed connection makes it possible to combine the operations of make-up and quality control, to obtain operational information about the dynamic parameters of the quality of the connection directly during the assembly process, and also to prevent self-unscrewing of threaded parts during operation.

When the ultrasonic assembly of the threaded connection reaches the yield point, the nonlinearity of the elastic characteristic of the mechanical oscillatory system (nonlinearity of the "saturation" type) begins to appear, caused by the presence of plasticity, which leads to a distortion of the amplitude-frequency characteristic and the appearance of a skeletal curve expressing the relationship between the frequency and amplitude of vibrations systems (Panovko Ya.G. Introduction to the theory of mechanical vibrations. - M .: Nauka. Main edition of physical and mathematical literature, 1980. - 272 p., S. 154-158). If the ultrasonic action is stopped, the mechanical system will return to its original state with a linear plasticity characteristic and a normal amplitude-frequency characteristic.

In the case when the applied force (moment) is large, the system becomes non-linear, the stiffness of the system (its elasticity coefficient) is no longer constant, the frequency and, accordingly, the period, begin to depend on the amplitude of the oscillations. That is, the behavior of a nonlinear system begins to depend on the amplitude of oscillations. In the case of a decrease in the stiffness coefficient when the yield point is reached, the system has a soft characteristic, and its skeletal curve turns out to be curved to the left. With a successive increase in the amplitude of the excitation force, the resonant frequency of oscillations decreases and the amplitude-frequency characteristic has a pronounced slope towards lower frequencies, and the skeletal curve corresponds to a soft stiffness characteristic. The resulting amplitude-frequency dependence resembles a resonant curve for a linear system, however, the resonant peak is somewhat deformed according to the curvature of the skeletal curve with a soft characteristic (Fundamentals of Measurement. Sensors and Electronic Devices: Textbook / K. Klassen. 4th ed. - Dolgoprudny: Publishing House "Intellect", 2012. - 352 p., S. 103-107).

If the amplitude of the sinusoidal action changes, then the peak of the resonance curve will move along the skeletal curve. Fixing the change in the sign of the increment of the resonant frequency, and when changing to a negative one, this moment is noted and a signal is given to stop tightening the threaded connection (Shuvaev V.G. Methodology for adaptive ultrasonic assembly of threaded connections of guaranteed quality // International Symposium "Reliability and Quality", 2018. Penza , May 21-31, 2018. S. 201-204). It is possible to improve the quality of identification by increasing the spectrum of the input action to the maximum possible value, that is, the best option is a shock input action. It is proposed, along with ultrasonic vibrations, to apply shock effects during the assembly process and to analyze damped vibrations, which will represent the impulse transient response of the system (weight function), that is, instead of frequency analysis of vibrations, to carry out temporal analysis, which will increase the resolution, since temporal characteristics can be measure more accurately.

Nonlinearity will manifest itself in a change in the period of damped oscillations, which is the basis of the proposed method. With a soft skeletal curve, there will be a decrease in the time between pulses and, having fixed this moment, it is possible to stop tightening the connection; in the case of a linear system, the time intervals will be symmetrical. Estimation of non-uniformity of the period of damped oscillations is made by comparing the time intervals between the intersections of the curve of the zero level.

The drawing shows a block diagram of a device for implementing the proposed method.

The device contains a striker 1, an anvil 2, a spindle 3, a wrench 4 and a nut 5. The product consists of assembled parts 6 and 7, which are pulled together by a bolt 8. The concentrator 9 amplifies mechanical vibrations. Pin 10 piezoceramic transducer 11 is clamped between the hub 9 and frequency-reducing element 12 (damper). The vibration sensor 13 is fixed on one of the assembled parts 7 and is connected to a low-pass filter 14, the signal from which is fed to the comparator 15. From the comparator 15, the signal is fed to the comparator 16, the second input of which receives signals from the clock generator 17. From the comparison device 16, the signals are sent to the indicator 18.

The method of assembling threaded connections is implemented as follows.

Pre-tighten the threaded connection. With successive impact interactions of striker 1 and anvil 2, rotational impulses are transmitted through spindle 3 and key 4 to nut 5, which is tightened with the required force. Under the action of the tightening force, the bolt is stretched, and the tightened parts are compressed. Using an electrical oscillation generator (not shown in the figure), ultrasonic mechanical vibrations are excited in the piezoceramic transducer 11, which are then amplified by the concentrator 9. The piezoceramic transducer 11 is clamped by a pin 10 between the concentrator and the frequency-reducing element 12 (damper). The piezoceramic transducer is assembled from discrete axial polarization washers, which are mechanically connected in series and electrically connected in parallel.

In the product, consisting of assembled parts 6 and 7, vibrations are excited and received during the screwing process, achieving resonance. The vibrations that have passed through the connection (bolt 8, nut 5 and assembled parts 6 and 7) are perceived by the vibration sensor 13, mounted on one of the assembled parts, and are converted into an electrical signal that is fed to the input of the low-pass filter 14. At the same time, the application of shock-rotational impulses, under the influence of which threaded connections are tightened in several shock cycles. Under the influence of the impact, a signal is formed from which the low-pass filter 14 extracts the impulse response of the system, detuning from the high-frequency components of the vibration. Next, the signal is fed to the comparator 15, where it is compared with the zero level, that is, levels greater than zero and levels less than zero are selected. The clock pulse generator 17 fills the selected levels with a high-frequency signal, which is recorded in the comparison device 16. The indicator 18 marks the results of comparing the levels of signals greater than zero and signals less than zero and signals a qualitative tightening of the threaded connection according to the dynamic criterion in the nonlinear region.

The proposed method for the controlled assembly of threaded connections makes it possible to ensure the guaranteed quality of each connection without tightening the technology for manufacturing and assembling connection parts through the use of control tools.

The developed device for the controlled assembly of parts makes it possible to analyze the impulse response and note the appearance of an inequality in the signals of damped oscillations, which indicates the transition of the joint to the plastic deformation zone.

Claims (2)

1. A device for controlled assembly of parts by tightening a threaded connection, containing a striker, an anvil, a spindle, a key, a nut, a bolt, a comparison device connected to a clock pulse generator and a comparator, an indicator, a vibration sensor designed to be mounted on one of the assembled parts a threaded connection that is connected to a low-pass filter, characterized in that it is equipped with a pin, a concentrator, a frequency-reducing element and a piezoceramic transducer, which is clamped by a pin between the concentrator and the frequency-reducing element, while the low-pass filter, comparator, comparator and indicator are connected in series, and the clock pulse generator is connected to the second input of the comparator. 2. A method for controlled assembly of a threaded connection by means of a device according to claim 1, including pre-tightening the threaded connection by applying torque to the movable element of the threaded connection and exposing the elements of the threaded connection and assembled parts to ultrasonic vibrations, converting mechanical vibrations into an electrical signal and analyzing vibrations, characterized in that they additionally strike and analyze the impulse response of damped oscillations and finish tightening when differences appear in the values of the half-periods of the analyzed oscillations, while the oscillations that have passed through the threaded connection are transmitted to the vibration sensor and converted into an electrical signal that is transmitted to the input of the lower filter frequencies, simultaneously carry out the application of shock-rotational pulses and tighten the threaded connection, while the signal from the low-pass filter is transmitted through the comparator to the comparison device and indicator, to the second input of the device The comparison devices receive signals from the generator.

Images