RU194611U1 - Installation for testing material samples for fatigue - Google Patents

Abstract

The utility model relates to testing equipment, namely to facilities for testing materials for fatigue. The setup uses the cantilever bending test method for a rotating sample. The loading force is realized due to the interaction of the magnetic core fixed to the active grip with the field of the first section of the stationary electric coil. The second section of this coil is used in a displacement meter. There is a temperature release device. It is represented by a laser mounted on a turntable having an electromagnetic drive with a control trigger. The control circuit includes the contacts of the stops of the turntable. There is a block for identifying the extremum of the active capture moving function with an indicator. The indicator reflects the current value of the active capture movement, the moment of reaching the extremum and the cyclical nature of the heat treatment device. 3 s.p. f-ly, 10 ill.

Description

 The utility model relates to testing equipment, namely to facilities for testing material samples for fatigue.

A number of methods and means of testing materials are described in the fundamental monographs of L.M. Shkolnik (Shkolnik L.M. Fracture growth rate and survivability of metal. - M.: Metallurgy, 1973. - 216 p .; Shkolnik L.M. Fatigue test methodology: reference book. - M .: Metallurgy, 1978. - 304 s. ) The application of a method is determined by the purpose of research.

The machine for testing fatigue during cantilever bending of a rotating sample of material - UKI - 10M, MUI - 6000, MVC - 6M, MVP - 10000, U40, CHUM - 70, has become widespread. For samples of small sections, self-oscillating loading mode is used (patent RU 100622 U1, publ. 12/20/2010; patent RU 108843 U1, publ. 09/27/2011).

Sometimes a researcher provides for an intermediate heat treatment in a fatigue test program. To do this, the material sample is freed from the grips, heat treatment is carried out separately and the sample is again mounted in the test setup. Installation for testing samples for fatigue according to patent RU 2624595 C1, publ. 07/04/2017 provides for recrystallization annealing due to an inductor with a coil covering the sample. The installation uses a self-oscillating loading mode.

The installation in question has limited operational capabilities for the following reasons:

- a large time constant of the heat cycle of heat treatment due to the heating of the surrounding elements;

- low coefficient of thermal conversion due to the dissipation of thermal energy;

- the installation does not reveal the current state of the material, i.e. the heat treatment procedure is carried out at an arbitrary point in time;

- self-oscillating loading mode limits the size range of samples.

Closest to the technical nature of the proposed solution is the installation for testing materials for fatigue according to patent RU 145586 U1, publ. 09/20/2014. The cited material fatigue testing apparatus comprising a base, active and passive grips, a loading device including two solenoid release coils and a drive mounted on the base, connected to a current source, a coaxial magnetic rod coupled to them, which is fixed to the active gripper and oriented in directions of deformation of the material sample, an electronic key of solenoid coils containing an amplifier-driver with the formation of a drive pulse formation circuit, at it is equipped with an active capture displacement meter and a phase determiner, the loading device is equipped with a passive capture drive consisting of a spindle with a phase position sensor and a clamp, with a passive capture at one end of the spindle and an electric motor at the other end, the current source is equipped with a test mode switch containing the commutator of the release and drive solenoid coils, the outputs of the solenoid coils are connected to the drive pulse formation circuit and the input of the active displacement meter capture through the switch of the solenoid release coils and the drive, the outputs of the spindle phase position sensor and the active capture displacement meter are connected to the inputs of the phase determiner. In this installation, the active capture displacement meter is made in the form of a closed current loop consisting of a series-connected solenoid release coil, a resistor, and a high-frequency output of a current source, while a rectifier is connected in parallel with the resistor, and a low-pass filter is connected in series with it.

The stated design of the installation for testing materials for fatigue has the same drawbacks as installations - analogues.

The technical result of the proposed solution is to expand the operational capabilities of the installation for testing samples of materials for fatigue.

The tasks are solved:

1. Development of a constructive installation scheme implementing a wide-range test mode.

2. Development of a unit for identifying the current state of the material of the test sample.

3. Development of a heat treatment device with a high thermal cycle efficiency.

The specified technical result is achieved by the fact that the installation for testing samples of materials for fatigue, containing a base, active and passive grips, a loading device, including two solenoid coils mounted on the base, connected to a current source, a magnetic core connected to them, which is fixed to the active grip and oriented in the direction of deformation of the material sample, the active capture displacement meter, which is made in the form of a closed current loop as part of a follower They are connected to the first solenoid coil, resistor and high-frequency output of the current source, and a rectifier connected in series with the low-pass filter is connected in parallel with the resistor, it is equipped with an extremum detection unit for the characteristics of the active capture movement and a heat treatment device for the material sample, while the second solenoid coil is connected to an adjustable DC output of a current source. In the proposed installation, the device for heat treatment of a sample of material is made on the basis of a rotary platform with a leading leash, which is equipped with two fixed electrocontact stops in its extreme positions and a drive composed of an electromagnet having a spring-loaded anchor connected to the leading leash with a flexible link with a speed regulator for its movement, RS - a trigger, the output of which is connected via an electronic key to the winding of the electromagnet, and its inputs are connected to the low-voltage output of the direct current source through the contacts of the electric contact stops, while the laser is mounted on the turntable in such a way that the axial line of its optical beam intersects the axial line of the material sample, and the diameter of the optical beam is less than the diameter of the working section of the material sample, while the speed regulator of the armature of the rotary platform drive magnet is made a plate fixed to the end of the electromagnet of the drive of the turntable under its spring-loaded anchor plate with a hole coaxial to the anchor, while the plate has a rotary I flap for partial closure of the aperture plate and provided with a locking position. In the proposed installation, the extremum detection block of the active capture motion characteristic contains a power supply, a time circuit consisting of a series-connected signal shaper of the high-frequency output of the current source and two countable triggers, a sampling conjunctor, the first input of which is connected to the output of the active capture displacement meter, and the second through the shaper duration with the output of the driver of the signal of the high-frequency output of the current source of the time circuit, the output of the conjunctor of sampling n through time-controlled input conjunctors with two integrators, the outputs of which are connected to the first inputs of the output conjunctors, the second inputs of the latter are connected to the output of the read conjunct, the inputs of which are connected to the time circuit through an inverter, the outputs of the output conjunctors are connected to the inputs of the comparison circuit and the amplitude selector, the output of the latter is through an extremum trigger, and the output of the comparison circuit is directly connected to the indicator.

The proposed technical solutions are illustrated by drawings:

FIG. 1 is a structural diagram of an apparatus for testing material samples for fatigue;

FIG. 2 is a view A of FIG. 1;

FIG. 3 is a structural diagram of the emphasis of the turntable;

FIG. 4 is a diagram of a drive circuit of a turntable;

FIG. 5 is a diagram of a meter for moving active capture;

FIG. 6 is a functional diagram of a block for detecting an extremum of an active capture displacement characteristic;

FIG. 7 is a diagram of an integrator;

FIG. 8 is a diagram of a comparison device;

FIG. 9 is a diagram of an amplitude selector;

FIG. 10 - voltage diagrams at the outputs of the elements of the functional diagram.

Accepted Designations

1. Passive capture

2. Sample material

3. Active capture

3-a. Magnetic core of active capture

4. The frame of the solenoid bifilar electric coil

5. Generator signal generator G

6. The first counting trigger

7. Second counting trigger

8. Sample Conjunctor

9. Shaper of the duration of the sampling pulse

10. The first integrator

11. The second integrator

12. Amplitude selector

13. RS - trigger fixing the extremum

14. Indicator

15. Comparison device

16. Reading conjunctor

17, 18. Input conjunctors of integrators

19, 20. Output conjunctors of integrators

21. Inverter

22. Reset Connector

24. Power supply (current source)

25. Turntable bearings

26. Installation base

27. Turntable

28. Electromagnet drive turntable

29. Leash

30, 31. Contact stops

32. Electromagnet winding 28

33. The frame of the electromagnet 28

34. Electromagnet anchor 28

35. Flexible traction

36. Anchor spring

37. Speed controller plate

30. Plate hole

40. Pin

41. Damper

42. Arc groove shutter

43. Lock pint

44. Plate mounting screws

45. The body of the electrical contact stop

46, 47. Contact elements

48. RS - trigger heat treatment device

49. Electronic key

50. Laser

In the practical implementation of the design decisions made, the designer proceeds from the principle of continuity, i.e. he widely uses the practice of the individual components and parts of similar products. We assume that the implementation of the proposed technical solutions will be carried out using some elements of the widespread machine UKI - 10M. Based on this approach in FIG. 1, the spindle with its electric drive and the counter of the loading cycles are not reflected, but only the passive grip 1 is shown.

In accordance with the structural diagram (Fig. 1), the test sample of material 2 is mounted at one end in a passive grip, and the other in the active grip 3 in the form of a ball-bearing assembly. There is a two-section (with bifilar winding) electric solenoid coil made on the frame 4. One winding W _{H is} designed to set the loading force of the material sample, the other - W _u is part of the active capture displacement meter circuit. A magnetic core 3-a enters the central hole of the frame 4 with a radial clearance, which is fixed at one end by an active grip. The loading force for the middle portion of the movement of the 3-a magnetic core is proportional to the current in the winding W _H (Sotskov B.S. Fundamentals of calculation and design of electromechanical elements of automatic and telemechanical devices. - M - L: Energy, 1965. p. 308-309). The inductance L _{u of the} other winding W _u also varies linearly. The winding W _{H is} connected to an adjustable DC output U _{H of the} current source.

The winding circuit W _{u is} shown in FIG. 5. The winding W _u together with the high-frequency sinusoidal output U _{G of the} current source (for clarity, this is reflected in the form of a generator G) and the resistor R1 form a closed electrical circuit.

RMS current value

where z is the impedance of the circuit.

here ω is the cyclic frequency of the signal of the generator G.

The voltage drop across the resistor R1 is proportional to the current

The sinusoidal voltage (3) is rectified by the diode bridge VD1-VD4 and smoothed by a U-shaped electric filter on two capacitors C1, C2 and resistor R2. Thus the output of the filter is obtained a smooth function in the form of displacement voltage U _pr. The nature of this function with respect to the argument, the number of loading cycles N will be similar to the Shkolnik deformation diagram (Shkolnik L.M. Crack growth rate and metal survivability. - M.: Metallurgy, 1973, p. 62, Fig. 24). The considered function reflects the processes in the material of the sample material. The ascending section of the function reflects an increase in the elastic limit due to the hardening phenomenon. The descending section corresponds to the appearance of irreversible damage, i.e. microcracks arise and grow.

It is important for the researcher to know how the state of the material changes with an increase in the number of loading cycles. Since the ascending and descending sections can correspond to a certain value of the displacement function, it is necessary, at a minimum, to identify the extremum of the function U _pr = f (N).

In FIG. 6 is a functional block diagram of an extremum detection unit of an active capture displacement characteristic. The time axis is defined by the generator G of the active capture displacement meter. The time chain includes the generator 5 of the signal generator G and two series-connected counting flip-flops 6, 7.

Discretization of the displacement function U _CR = f (N) is carried out by the conjunctor 8 using a shaper of duration 9. At the output of the conjunctor 8, rectangular pulses of constant duration with an amplitude equal to the value of the function U _CR = f (N) at the given time are obtained. The time step of these pulses is equal to the period of the signal of the generator G.

The principle of detecting an extremum is to compare the amplitudes of two adjacent pulses at the output of the sampling conjuncture 8. An increasing section of the function U _pr = f (N) corresponds to a large amplitude of the next pulse relative to the previous one. In a falling section, vice versa. Since the compared pulses are separated in time, two integrators 10, 11 are provided in the circuit. The output potentials of the integrators are compared by the amplitude selector 12 (Fig. 9), the outputs of which control the RS-trigger 13 of the extremum.

To reflect the operating mode of the installation, a display indicator is provided. The indicator has three time channels (according to the principle of a three-channel electron beam escillograph):

- channel moving active capture;

- channel of the trigger state of the extremum;

- channel device for heat treatment of a sample of material.

The signal of movement of the active capture forms the comparison device 15 as the difference potential of the integrators. Accordingly, the user will observe bipolar pulses on the indicator that are proportional to the amount of active capture displacement, moreover, on the increasing portion of the function U _pr = f (N), the pulses are positive, and on the falling one, negative. The pulse duration forms the read conjunct 16. The main functional components are controlled by a time chain using input integrators 17, 18 and output 19, 20. To implement the logical function of the operation of the read conjunct 16, an inverter 21 is provided. One measurement cycle is carried out during the single state of the trigger 7 of the time chain. At the end of one measurement cycle, the conjunctor 22 generates a reset pulse.

The state channel of the trigger 13 extremum reflects the potential of a single output. On the ascending branch of the function U _CR = f (N), the potential is close to zero (coincides with the sweep line). When reaching the extreme, the potential is close to the low-voltage power supply E (microcircuit power).

The channel of the heat treatment device of the material sample reflects in the form of a meander the cycles of its operation.

Power supply to all elements of the installation provides a power supply 24.

The extremum identification block of the active capture displacement characteristic works as follows - see diagrams of voltages at the outputs of circuit elements (Fig. 10). The initial state of all block triggers is set in a regular way by the power supply front when the power supply 24 is turned on (not shown in Fig. 6).

The clock cycle of the unit sets the time target for the high-frequency (kilohertz) signal U _G of the power supply 24. This signal is converted by the driver 5 into a rectangular shape U ₅ . The front of the pulse U _{5 is} triggered by a counting trigger 6, and by the cut of the last pulse, the counting trigger 7 is triggered.

The second input signal of the block is the analog displacement function U _pr = f (N) from the circuit of FIG. 5 which is input conjunctor 8. The second input to the shaper conjunctor 8 9 into a rectangular pulse U _9, U formed by the pulse _5. Thus, a rectangular impulse of duration U ₉ and an amplitude equal to U _ol at a given time will appear at the output of the conjunctor 8.

Next, in the interval of the single state of the trigger 7 of the time chain, the amplitudes of two adjacent pulses U ₈ are compared: the previous pulse goes to the input of the integrator 10, and the next to the input of the integrator 11. The integrators are designed the same way according to the scheme of FIG. 7. The charging current of capacitor C is determined by the parameters of the RC circuit and the amplitude of the input pulse. The output voltage of the integrator U ₁₀ (U ₁₁ ) is proportional to the amplitude of the input pulse coming from the output of the conjunctor 8. The discharge of the capacitor C is carried out through the transistor VT by the reset signal U ₂₂ . The output voltages of the integrators are supplied to the inputs of the comparison device 15 and the amplitude selector 12. The output of the amplitude selector is connected to the inputs of the extremum trigger 13. The distribution of pulses is carried out by the conjunctors 17, 18, 19, 20, and their operation logic is traced from the voltage diagrams of FIG. 10. The procedure for comparing the output voltages of the integrators takes place during the action of the pulse U ₁₆ from the output of the read conjunct 16.

The comparison circuit (Fig. 8) is a differential amplifier on transistors VT1, VT2 according to the scheme with a common emitter. In the initial state, the transistors are in cutoff mode due to the resistors R1, R4. When the input signals U ₁₉ , U ₂₀ arrive, the operating point is shifted to the active region of the transistors, while the collector voltages will be proportional to the input signals. The differential potential of the collectors goes to the indicator 14.

The operation of the amplitude selector 12 (Fig. 9) is conveniently considered together with the trigger of extremum 13. Scheme 12 is a composition of two diode limiters: one is built on the diode VD1 and resistor R1, the other on the diode VD2 and resistor R2. The operating principles of each limiter are based on the characteristic of the diode - with a positive potential of the anode with respect to the cathode, the diode is electrically conductive. On an increasing section of the characteristic U _pr = f (N), the input voltages are correlated as U ₂₀ > U ₁₉ , therefore, the diode VD1 is electrically conductive and the potential of the first limiter is fed to the reset input R of the RS-flip-flop 13. When the extremum of the function U _pr = f (N) is reached the situation becomes reverse and at this moment a pulse from the second limiter arrives at the trigger input S, respectively, trigger 13 goes into a single state.

We turn to the device for heat treatment of a sample of material. A rotary platform 27 is installed in the bearings 25 on the basis of the 26 fatigue testing equipment samples. To rotate the platform, a drive electromagnet 28 and a lead 29 are mounted on the platform. The rotation angle of the platform is limited by two electrical contact stops 30, 31 that interact with the lead 29. In order to simplify the design of the stops, the leash is made of an insulating material, for example fiberglass (or its surface in the contact zone with the stops has a dielectric coating ) The coil 32 of the electromagnet 28 is wound on the frame 33. The anchor 34 of the electromagnet has a cylindrical shape and is placed in the hole of the frame with some radial clearance. A coil spring 36 is installed under the anchor, which rests on a plate 37 fixed with screws on the frame 33.

To stabilize the speed of movement of the armature provides a speed controller (Fig. 2). A through hole 39 coaxial with the opening of the frame 33 is made on the plate 37. A rotary shutter 41 is installed on the plane of the plate with the help of a pin 40. The arc groove 42 of the shutter together with the screw 43 form a shutter position lock. The plate 37 is attached to the electromagnet frame 33 with screws 44. The principle of operation of the speed controller is based on the formation of viscous friction, which, in contrast to constant (Coulomb) friction, does not form a stagnation zone in the displacement characteristic.

The force of viscous friction is equal to

where x is the linear velocity of the armature of the electromagnet;

h = ρS is the coefficient of viscous friction;

Here ρ is the density of air;

S is the effective section of the hole 39.

From the above formulas it follows that the force of viscous friction can be controlled by changing the effective cross section of the hole 39 by turning the shutter 41.

Both contact stops are made of the same type - FIG. 3, where the section of the lead 29 of the turntable is conventionally shown. In the electrically insulating housing 45 of the abutment, two flexible contact elements 45, 46, which are common for relay devices, are fixed. The contact elements are mounted in such a way that they form a normally open contact. The control circuit of the electromagnet 28 in addition to the contact stops 30, 31 includes an RS-trigger 48 and a power electronic key 49.

In addition to the above elements, a laser 50 is included in the device under consideration. The laser is mounted on the turntable 27 in such a way that the axial line of its optical beam intersects the axial line of the material sample, and the diameter of the optical beam is smaller than the diameter of the working part of the material sample. The above ratio of diameters provides a high coefficient of efficiency of the thermal cycle, since the optical spot of the laser beam passes only along the surface of the working section of the sample and does not heat the surrounding elements of the installation. Due to the relatively short heat treatment time, the heating of the thickened ends of the sample in the grips will be limited.

In the initial position, under the influence of the spring 36 of the anchor, the lead 29 is on the stop 30 and its contact S ₀ is closed, while the optical beam of the laser 50 is located at the beginning of the working section of the material sample. Accordingly, when the turntable is shifted to the second stop 31, the optical beam passes the entire length of the working portion of the material sample.

Consider the option of temperature release of a sample of material to eliminate hardening. To implement this process, the load of the sample is removed by disconnecting the power supply U _{H of the} winding W _{H of the} electromagnet 4 at the time of the appearance of a single signal of the trigger of extremum 13 on the indicator 14. Without stopping the rotation of the passive capture 1, turn on the heat treatment device. Since the contact S _{0 of the} stop 30 is closed in the initial position, the trigger 48 is set to a single state and includes an electronic key 49, which feeds the winding 32 of the electromagnet 28. Anchor 34 through the rod 35 and the lead 29 rotates the platform 27 together with the laser 50 to the stop 31. reaching the stop 31, the leash 29 closes the normally open contact S _k , which leads to the overturn of the trigger 48, respectively, to deenergize the coil 32. After that, the platform 27 under the action of the spring 36 will return to its original position. When the platform oscillates, along with the laser, the beam of the latter passes the path of the working section of the material sample, and since the sample rotates, heating is carried out over the entire surface. The heating temperature is determined by the laser power and the number of cycles of the turntable. Note that the time to intimidate the initial hardening is relatively small, because the depth of heating of a sample of material is needed by tenths of a millimeter.

The proposed installation allows you to perform other types of heat treatment, such as quenching. It is known that some materials are quenched by heating, followed by cooling in air. If you block the power of the electromagnet 28, then only the initial portion of the sample will be subjected to heat treatment, where the mechanical stresses are maximum. The cycle period of the heat treatment device is determined by the inertia of the kinematic elements and the stiffness of the spring 36 anchors

where m is the mass of the moving elements of kinematics reduced to the anchor 34 of the electromagnet 28;

D - spring stiffness 36.

They use a fatigue testing device for samples of materials in accordance with the test program. The proposed installation allows you to implement a variety of programs, including tests with a given load and tests with a given deformation. Consider the basis of one version of a program for testing a material sample for fatigue.

Fix a sample of material in passive and active captures and include installation. Set the required frequency of rotation of the passive capture (as was noted above by the spindle drive on which the passive capture is fixed). According to the calibration schedule of the installation by the voltage regulator U _H on the power supply 24, the magnitude of the winding current W _{H of the} solenoid coil 4 sets the loading force of the material sample. The magnitude of the deflection is measured on the scale grid of the indicator 14.

During the rotation of the loaded sample of material due to hardening, the deflection of the active capture changes, which leads to the displacement of the magnetic core of the 3rd active capture. The displacement of the rod changes the inductance L _{u of the} winding W _{u of the} active capture displacement meter, at the output of which the displacement function V _pr = f (N) is formed. The block identifying the extremum of the displacement characteristic generates an extremum signal and reflects it on the indicator.

Next, a temperature release of a sample of material is carried out. By turning off the power U _{H, the} windings W _H remove the load of the material sample and turn on the heat treatment device. In accordance with the operating cycle of the trigger 48, the optical beam of the laser 50 repeatedly moves along the working area of the rotating material sample, providing heating to the desired temperature. The heating time depends on the material being studied, the type of heat treatment, and the laser power. Next, continue testing in accordance with the test program.

Thus, the proposed installation for testing samples of materials for fatigue allows you to implement a wide range of test programs. The installation indicator shows on a scale the current value of the active capture displacement in the form of rectangular pulses, while the upward section corresponds to positive impulses, and the downward section to negative ones. The indicator also reflects the moment of the extremum of the active capture movement function and the number of cycles of the heat treatment device. Heat treatment is performed without dismantling the sample both at an arbitrary point in time and by a signal about the current state of the material sample. Installation of the project in circulation, the test mode is set by the electric authorities.

Claims (4)

1. Installation for testing samples of materials for fatigue, containing a base, active and passive grips, a loading device, including two solenoid coils mounted on the base, connected to a current source, a magnetic core coupled to them, which is fixed to the active grip and oriented in the direction of deformation material sample, active capture displacement meter, which is made in the form of a closed current loop as part of a series-connected first solenoid coil, resistively and a high-frequency output of the current source, while a rectifier is connected in parallel with the resistor, a low-pass filter is connected in series, characterized in that it is equipped with an extremum detection unit for the characteristics of the active capture displacement and a temperature release device for the material sample, while the second solenoid coil is connected to an adjustable DC output of a current source. 2. Installation for testing samples of materials for fatigue according to claim 1, characterized in that the device for temperature tempering of a sample of material is made on the basis of a rotary platform with a leading leash, which is equipped with two fixed electrocontact stops in its extreme positions and a drive composed of an electromagnet having a spring loaded connected to a leading leash through flexible traction, an anchor with a speed regulator for its movement, an RS-trigger, the output of which is connected via an electronic key to the winding of the electromagnet, and its input The odes are connected to the low-voltage direct current output of the current source through the contacts of the contact stops, while the laser is mounted on the rotary platform so that the axial line of its optical beam intersects the axial line of the material sample and the diameter of the optical beam is smaller than the diameter of the working section of the material sample. 3. Installation for testing material samples for fatigue according to claim 2, characterized in that the speed controller of the armature of the rotary platform drive electromagnet is made in the form of a rotary platform drive magnet mounted at the end of the electromagnet under its spring-loaded armature plate with a hole coaxial with the armature, while the plate is mounted rotary damper with the possibility of partial overlapping of the plate hole and equipped with a position lock. 4. Installation for testing samples of materials for fatigue according to claim 1, characterized in that the extremum detection block of the active capture displacement characteristic comprises a power supply, a time circuit consisting of a series-connected signal shaper of the high-frequency output of the current source and two countable triggers, a sampling conjunctor, the first the input of which is connected to the output of the active capture displacement meter, and the second through the shaper of duration with the output of the shaper of the signal of the high-frequency output of the source as a current of the time circuit, the output of the sampling conjunct is connected via time-controlled input conjunctures with two integrators, the outputs of which are connected to the first inputs of the output conjunctors, the second inputs of the latter are connected to the output of the read conjunct, the inputs of which are connected to the time circuit via an inverter, the outputs of the output conjunctors are connected to the inputs of the comparison circuit and the amplitude selector, the output of the latter is through an extremum trigger, and the output of the comparison circuit is directly connected to the indicator.

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