CN107703006A - Stretching preloads lower dynamic torsional fatigue Mechanics Performance Testing device - Google Patents

Abstract

The invention relates to a dynamic torsional fatigue mechanical performance testing device under tensile preload, which belongs to the technical field of precision instruments. A horizontal arrangement is adopted, including a tensile unit, a torsional fatigue unit, a force signal and displacement signal detection unit, and a specimen clamping unit. On the same axis; the tensile unit, the torsional fatigue unit, the force signal and displacement signal detection unit and the specimen clamping unit are all installed on the bottom plate; the magnetic field and thermal field loading are placed between the tensile unit and the torsional fatigue unit, Realize the coupled loading of force, heat and magnetism. The advantages are that the testing precision is high, the structure is relatively simple, and it is easy to implement. It can realize the combined loading of tension, torsional fatigue and torsional fatigue under tensile preload; it can realize the coupled loading of force, electricity, heat and magnetism; it can observe the microstructural changes such as crack propagation when the material is subjected to torsional fatigue in real time.

Description

Testing device for dynamic torsional fatigue mechanical properties under tensile preload

technical field

The invention relates to the field of precision scientific instruments in the field of material micromechanical performance testing, in particular to a dynamic torsional fatigue mechanical performance testing device under tensile preload. The instrument can be integrated with optical microscope and electrothermal magnetic field, which provides an effective method for studying the failure mechanism and crack propagation of torsional fatigue materials under tensile preload.

Background technique

The development of materials has greatly promoted the progress of society, but at the same time, with the advancement of science and technology, human beings have higher and higher requirements for the use of materials, and the conditions of use have become more and more complex. Although material science and technology are developing rapidly, the current main research areas are focused on the development and application of new materials. The development of characterization and evaluation technology for material properties is slow, and mechanical performance testing devices that can truly simulate the actual service conditions of materials are very rare. Obviously, if the application of traditional testing devices cannot fully reflect the actual stress state of some components, the measured mechanical parameters do not have absolute reference value.

In addition, automobile spindles, machine tool transmission shafts, etc. are subjected to the interaction of a series of composite loads such as tension, torsional fatigue, and even electrothermal magnetic fields during actual service, and these actual external factors will have a greater impact on the mechanical properties of materials. . Therefore, it is difficult to guarantee the reliability of components in structural design based on the mechanical parameters measured under a single load. If we can develop a mechanical testing instrument that can provide close to the real stress of the material and simulate the real environment in which the material is located in the test of the mechanical properties of the material, the mechanical properties of the material under actual service conditions can be obtained more accurately, thereby More effectively avoid a series of major accidents caused by material failure.

Contents of the invention

The object of the present invention is to provide a dynamic torsional fatigue mechanical performance testing device under tensile preload, which solves the above-mentioned problems in the prior art. The present invention has the following characteristics: (1) It can realize the single load loading of tension and torsional fatigue and the combined loading of torsional fatigue under tensile preload; Axial gap to ensure the symmetry of fatigue loading; (3) It can be coupled with electric field, thermal field and magnetic field to realize coupling loading of force, electricity, heat and magnetism; (4) It can be integrated with optical microscope to realize the torsional fatigue loading of materials Dynamic monitoring of microscopic properties such as tissue evolution and damage mechanism. The invention provides an experimental method capable of simulating the torsional fatigue of materials in real service state, which is of great significance for revealing the microcosmic changes of material failure.

Above-mentioned purpose of the present invention is achieved through the following technical solutions:

The dynamic torsional fatigue mechanical performance test device under tensile preload adopts a horizontal arrangement, including a tensile unit, a torsional fatigue unit, a force signal and displacement signal detection unit, and a specimen clamping unit. The tensile unit and the torsional fatigue unit are respectively arranged on both sides of the test piece 41, and on the same axis as the test piece 41; the tensile unit, the torsional fatigue unit, the force signal and displacement signal detection unit and the test piece clamping unit are all installed on the bottom plate 2; the magnetic field 1. The thermal field loading is placed between the tensile unit and the torsional fatigue unit to realize the coupled loading of force, heat and magnetism.

The stretching unit is powered by an AC servo motor 1, after being decelerated by the worm gears I, II 4, 9, and worms I, II 5, 7, the lead screw 11 is driven to rotate, and the lead screw nut pair converts the rotational motion of the lead screw 11 into a nut 12 Linear motion, so as to realize the loading of tensile force; wherein the AC servo motor 1 is fixed on the base plate 2 through the motor support 3, and the worm I5 is connected to the output shaft of the AC servo motor 1; the worm gear I4 and the worm II7 are connected On the shaft I6, the shaft I6 is fixed on the base plate 2 through the shaft support 8; the worm wheel II9 is connected to the lead screw 11 through a flat key, and the lead screw 11 is connected to the base plate 2 through the lead screw support 10; the nut 12 is connected to the nut support 13, and the nut support 13 is connected to the guide rails II, III 38, 43 through the sliders III, IV 39, 40, and the guide rails II, III 38, 43 are connected to the support plate 34 through the inner hexagonal screws, and the support plate 34 is fixed on the base plate 2.

The torsional fatigue unit adopts the electromagnetic exciter 21 as a driver, and converts the reciprocating linear motion of the electromagnetic exciter 21 into the reciprocating rotational motion of the axis II33 through the gear 19 and the rack 22, thereby realizing the loading of the torsional fatigue load; , the shaft II 33 is fixedly connected to the base plate 2 through the torsion shaft support 18, the electromagnetic exciter 21 is fixed on the base plate 2, and the electromagnetic exciter 21 is fixedly connected to the rack 22 through a threaded connection; the tooth The bar 22 is connected to the guide rail I30 through the sliders I, II23, 28, the guide rail I30 is connected to the height-adjustable bottom plate 29, and the height-adjustable bottom plate 29 is embedded in the bottom plate 2 through a groove; the gear 19 is connected by a key connection onto axis II33.

The force signal and displacement signal detection unit includes a tension sensor 14, a torque sensor 17, a linear grating displacement sensor and an encoder 20; one end of the tension sensor 14 is threaded to the nut support 13, and the other end is connected to the clamp body on the support I15; the torque sensor 17 is connected by a flange, one end is connected to the shaft II33, and the other end is connected to the clamp body II24; the linear grating displacement sensor includes a grating ruler 36 and a reading head 37, and the grating The ruler 36 is fixed on the bottom plate 2 through the grating ruler support 35, and the reading head 37 is fixed on the clamp body support I15, and the deformation of the test piece is indirectly measured by measuring the displacement of the clamp body support I15. The coupling 32 is connected with the shaft II 33 to realize the measurement of the reciprocating rotation angle and the fatigue cycle, wherein the encoder 20 is fixedly connected to the bottom plate 2 through the bracket 31 .

The specimen clamping unit includes pressure plates I, II25, 26 and clamp bodies I, II27, 24, the clamp body I27 is connected to the clamp body support I15 through threads, and the clamp body II24 is connected through the clamp body support II16 On the bottom plate 2; the clamp bodies I, II 27, 24 are processed with profiling grooves to realize the positioning of the test piece 42, and the pressure plates I, II 25, 26 are respectively fixed on the clamp bodies II, I 24, 27 by hexagon socket screws , to apply a clamping force.

The gear 19 and the rack 22 adopt a double-thick gear staggered tooth structure to eliminate the meshing gap, so as to ensure that the output displacement of the electromagnetic exciter 21 is completely converted into the torsional displacement of the test piece 41; wherein, the double-thick staggered tooth gear adjusts the staggered tooth angle Finally, it is locked by bolt 42. The height-adjustable bottom plate 29 adjusts the radial gap between the rack and pinion, the height-adjustable bottom plate 29 is positioned through four trapezoidal grooves, and the height is adjusted through four flat-head screws below.

The invention has the beneficial effects of high testing precision, relatively simple structure and easy realization. Compared with other existing torsional fatigue equipment, the present invention has the following characteristics and advantages: (1) It can realize the combined loading of tension, torsional fatigue and torsional fatigue under tensile preload; (2) It can be combined with electric field, thermal field and Magnetic field coupling realizes coupled loading of force, electricity, heat and magnetism; (3) It can be integrated with an optical microscope to realize in-situ observation, and observe microstructural changes such as crack propagation when the material is subjected to torsional fatigue in real time. In a word, the invention provides an effective method for studying the failure mechanism and crack propagation of dynamic torsional fatigue materials under tensile preload, and has strong practical value.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention, and constitute a part of the application. The schematic examples and descriptions of the present invention are used to explain the present invention, and do not constitute improper limitations to the present invention.

Fig. 1 is a schematic diagram of the overall appearance structure of the present invention;

Fig. 2 is the structure schematic diagram of torsional fatigue unit of the present invention;

Fig. 3 is the structural representation of stretching unit of the present invention;

Fig. 4 is a schematic structural view of the specimen clamping unit of the present invention;

Fig. 5 is a schematic diagram of the anti-backlash structure of the rack and pinion of the present invention.

In the figure: 1. AC servo motor; 2. Bottom plate; 3. Motor support; 4. Worm gear I; 5. Worm I; 6. Shaft I; 7. Worm II; 8. Shaft support; 10. Lead screw support; 11. Lead screw; 12. Nut; 13. Nut support; 14. Tension sensor; 15. Clamp body support I; 16. Clamp body support II; 17. Torque sensor; 18. Torsion shaft support; 19, gear; 20, encoder; 21, electromagnetic exciter; 22, rack; 23, slider I; 24, clip body II; 25, pressure plate I; 26, pressure plate II; 27, Clamp body Ⅰ; 28. Slider Ⅱ; 29. Height adjustable bottom plate; 30. Guide rail Ⅰ; 31. Bracket; 32. Encoder coupling; 33. Shaft Ⅱ; 34. Support plate; 35. Grating ruler support 36. Grating ruler; 37. Reading head; 38. Guide rail II; 39. Slider III; 40. Slider IV; 41. Test piece; 42. Bolt; 43. Guide rail III.

detailed description

The detailed content of the present invention and its specific implementation will be further described below in conjunction with the accompanying drawings.

Referring to Figures 1 to 5, the device for testing dynamic torsional fatigue mechanical properties under tensile preload of the present invention adopts a horizontal arrangement, including a tensile unit, a torsional fatigue unit, a force signal and displacement signal detection unit, and a specimen holder. holding unit, the tensile unit and the torsional fatigue unit are respectively arranged on both sides of the test piece 42, and on the same axis as the test piece 42; the tensile unit, the torsional fatigue unit, the force signal and displacement signal detection unit and the test piece All clamping units are installed on the bottom plate 2; a large space is reserved in the central area of the device, and the magnetic field and thermal field loading can be placed between the tensile unit and the torsional fatigue unit to realize the coupled loading of force, heat and magnetism; in-situ observation The unit can be placed directly above the unit.

Referring to Fig. 3, the stretching unit is powered by an AC servo motor 1, and after being decelerated by worm gears I, II 4, 9, and worms I, II 5, 7, it drives the lead screw 11 to rotate, and the lead screw nut pair drives the lead screw 11 to rotate. The rotary motion is converted into the linear motion of the nut 12, so as to realize the loading of the tensile force; wherein the AC servo motor 1 is fixed on the base plate 2 through the motor support 3, and the worm I5 is connected to the output shaft of the AC servo motor 1; The worm wheel I4 and the worm II7 are connected to the shaft I6, and the shaft I6 is fixed on the bottom plate 2 through the shaft support 8; the worm wheel II9 is connected to the lead screw 11 through a flat key, and the lead screw 11 is connected to the bottom plate through the lead screw support 10 2; the nut 12 is connected to the nut support 13, the nut support 13 is connected to the guide rail II, III 38, 43 through the slider III, IV 39, 40, and the guide rail II, III 38, 43 is connected to the support by the hexagon socket head screw The support plate 34 is fixed on the bottom plate 2 on the plate 34 .

Referring to Fig. 2, the torsional fatigue unit adopts the electromagnetic exciter 21 as the driver, and converts the reciprocating linear motion of the electromagnetic exciter 21 into the reciprocating rotational motion of the shaft II 33 through the gear 19 and the rack 22, thereby realizing torsion Fatigue load loading; wherein, the shaft II 33 is fixedly connected to the base plate 2 through the torsion shaft support 18, the electromagnetic exciter 21 is fixed on the base plate 2, and the electromagnetic exciter 21 is connected to the rack 22 through a threaded connection. Fixed connection; the rack 22 is connected to the guide rail I30 through the sliders I, II23, 28, the guide rail I30 is connected to the height-adjustable bottom plate 29, and the height-adjustable bottom plate 29 is embedded in the bottom plate 2 through a groove; the gear 19 Connected to shaft II 33 by means of a keyed connection.

1 and 3, the force signal and displacement signal detection unit includes a tension sensor 14, a torque sensor 17, a linear grating displacement sensor and an encoder 20; one end of the tension sensor 14 is threaded to the nut support On the seat 13, the other end is connected to the clamp body support I15; the torque sensor 17 is connected to the shaft II33 at one end, and the other end is connected to the clamp body II24 through a flange connection; the linear grating displacement sensor includes a grating Ruler 36 and reading head 37, the grating ruler 36 is fixed on the base plate 2 through the grating ruler support 35, the reading head 37 is fixed on the clamp body support I15, and the displacement of the test piece is indirectly measured by measuring the displacement of the clamp body support I15 The amount of deformation can effectively avoid the displacement measurement error of the test piece caused by the deformation of the tensile force sensor; the encoder 20 is connected to the shaft II33 through the encoder coupling to realize the measurement of the reciprocating rotation angle and the fatigue cycle, wherein the encoder 20 It is fixedly connected to the base plate 2 through a bracket 31 .

Referring to Fig. 4, the specimen clamping unit includes pressure plates I, II 25, 26 and clamp bodies I, II 27, 24, the clamp body I 27 is screwed to the clamp body support I15, and the clamp body II 24 passes through The clamp body support II16 is connected to the base plate 2; the clamp bodies I, II27, and 24 are processed with profiling grooves to realize the positioning of the test piece 42, and the pressure plates I, II25, and 26 are respectively fixed on the clamp body by hexagon socket screws. On Ⅱ, Ⅰ24, 27, apply clamping force.

Referring to Fig. 5, the gear 19 and the rack 22 adopt a double-thick gear staggered tooth structure to eliminate the meshing gap, so as to ensure that the output displacement of the electromagnetic exciter 21 is completely converted into the torsional displacement of the test piece 41; The toothed gear is locked by the bolt (42) after adjusting the misaligned tooth angle. The height-adjustable bottom plate 29 adjusts the radial gap between the rack and pinion, the height-adjustable bottom plate 29 is positioned through four trapezoidal grooves, and the height is adjusted through four flat-head screws below.

The test device for dynamic torsional fatigue mechanical properties under tensile preload of the present invention has a large space reserved in the central area, and can be used in coupling with electric field, thermal field and magnetic field to realize coupling loading of force, electricity, heat and magnetism, thereby truly simulating the actual state of the material. service status. The tensile unit adopts an AC servo motor to realize the loading of the tensile load after the two-stage deceleration and torque increase of the worm gear; the torsional fatigue unit uses the electromagnetic exciter as the driver, and is driven by the rack and pinion mechanism to realize the loading of the torsional fatigue load; The signal and displacement signal detection unit adopts force sensor, linear grating displacement sensor and photoelectric encoder for signal acquisition. The test device can realize tensile loading, torsional fatigue loading, and composite loading of dynamic torsional fatigue under tensile preload. In addition, a certain space is reserved in the central area of the device, which can realize the coupled loading and testing of mechanical heat and magnetic force. The overall structure of the device is small, and it can be integrated with an optical microscope to monitor the expansion behavior of torsional fatigue cracks in real time and realize in-situ observation. This device realizes the coupling loading of tensile and torsional fatigue, the principle is reliable, and can accurately measure the torque and torsion angle. At the same time, through the ingenious design of the double thick gear staggered tooth structure, the transmission clearance of torsional fatigue loading is eliminated, and the dynamic performance is good. , can accurately test and analyze the mechanical properties and failure mechanisms of materials under torsional fatigue, and has broad application prospects.

Referring to Fig. 1 to Fig. 5, the inventive device for testing dynamic torsional fatigue mechanical properties under tensile preload needs to calibrate and calibrate the tension sensor, torque sensor, grating linear displacement sensor and encoder before installing the test instrument. , and then install and debug the instrument. After each experiment, the clamp bodies I and II must be returned to their original positions for the clamping of the next test specimen.

The dynamic torsional fatigue mechanical property testing device under tensile preload of the present invention, its concrete testing method is as follows:

a. Before the start of each experiment, first check whether the clamp bodies Ⅰ and Ⅱ are at the zero position. You can use the software to record the absolute position of the zero point of the clamp bodies Ⅰ and Ⅱ, so that the clamp bodies Ⅰ and Ⅱ can be accurately adjusted after each experiment. Back to the zero point, which is convenient for the clamping of the test piece.

b. Put the test piece into the groove of the lower clamp body Ⅰ and Ⅱ, clamp it, and clear all the readings of the tension sensor, torque sensor and grating linear displacement sensor.

c. Carry out tensile preload parameter setting afterwards, the tensile loading mode of the present invention can adopt force loading mode or speed loading mode, and force loading mode is to feed back the size of loading force through the real-time measurement of tension sensor, and speed loading mode is The real-time measurement of the grating linear displacement sensor is used to feedback and control the loading speed. Different loading modes can be selected according to different experimental requirements.

d. Apply torsional fatigue load to the specimen after the tensile preload is loaded, and control the excitation frequency of the electromagnetic exciter according to different experimental requirements, so as to control the relevant parameters of the torsional fatigue test;

e. If in-situ observation is required during the experiment, the present invention needs to be placed under an optical microscope, and the specimen also needs to be polished and corroded, so as to dynamically observe the crack propagation mechanism of the material under torsional fatigue in real time.

The present invention draws the S-N curves of materials at different torsion frequencies by measuring the torsion angle and cycle times of torsional fatigue, and can also obtain mechanical parameters such as the shear modulus G of the material according to the linear stage of the torque-torsion angle curve obtained, the specific formula as follows:

Shear modulus G =

in, is the torque increment, is the angle increment, is the gauge length, is the sample diameter;

mean stress ;

in is the maximum stress, is the minimum stress;

Stress amplitude: ;

Stress ratio: ;

The mechanical properties of materials are mainly manifested in the deformation and failure properties of materials under load. The elastic modulus, shear modulus, fracture limit, fatigue strength and other parameters of the material are the most important test objects in the mechanical performance test of the material. Through the torsional fatigue test, a series of indicators such as the shear modulus, fatigue strength, and cycle times of the material can be measured, so as to measure the mechanical properties of the material when it is subjected to torsional fatigue. In addition, in-situ observation is also very helpful for the study of fatigue crack growth mechanism.

The above descriptions are only preferred examples of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made to the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. The utility model provides a dynamic torsional fatigue mechanical properties testing arrangement under tensile preload which characterized in that: the device is horizontally arranged and comprises a stretching unit, a torsion fatigue unit, a force signal and displacement signal detection unit and a test piece clamping unit, wherein the stretching unit and the torsion fatigue unit are respectively arranged on two sides of a test piece (41) and are on the same axis with the test piece (41); the stretching unit, the torsion fatigue unit, the force signal and displacement signal detection unit and the test piece clamping unit are all arranged on the bottom plate (2); the magnetic field and the thermal field are loaded between the tension unit and the torsional fatigue unit, so that the thermomagnetic coupling loading is realized.

2. The device for testing the dynamic torsional fatigue mechanical properties under the tensile preload according to claim 1, wherein: the stretching unit adopts an alternating current servo motor (1) to provide power, the speed is reduced through worm gears I, II (4, 9) and worms I, II (5, 7) to drive a lead screw (11) to rotate, and a lead screw nut pair converts the rotary motion of the lead screw (11) into the linear motion of a nut (12), so that the loading of stretching force is realized; the alternating current servo motor (1) is fixed on the bottom plate (2) through the motor support (3), and the worm I (5) is connected to an output shaft of the alternating current servo motor (1); the worm wheel I (4) and the worm II (7) are connected to the shaft I (6), and the shaft I (6) is fixed on the bottom plate (2) through a shaft support (8); the worm gear II (9) is connected to a lead screw (11) through a flat key, and the lead screw (11) is connected to the bottom plate (2) through a lead screw support (10); the nut (12) is connected to a nut support (13), the nut support (13) is connected to guide rails II and III (38 and 43) through sliders III and IV (39 and 40), the guide rails II and III (38 and 43) are connected to a support plate (34) through hexagon socket head cap screws, and the support plate (34) is fixed to the base plate (2).

3. The device for testing the dynamic torsional fatigue mechanical properties under the tensile preload according to claim 1, wherein: the torsional fatigue unit adopts an electromagnetic vibration exciter (21) as a driver, and the reciprocating linear motion of the electromagnetic vibration exciter (21) is converted into the reciprocating rotary motion of a shaft II (33) through a gear (19) and a rack (22), so that the loading of a torsional fatigue load is realized; the shaft II (33) is fixedly connected to the bottom plate (2) through a torsion shaft support (18), the electromagnetic vibration exciter (21) is fixedly connected to the bottom plate (2) through threads, and the electromagnetic vibration exciter (21) is fixedly connected with the rack (22) through threads; the rack (22) is connected to a guide rail I (30) through sliding blocks I and II (23 and 28), the guide rail I (30) is connected to a height-adjustable base plate (29), and the height-adjustable base plate (29) is embedded into the base plate (2) through a groove; the gear wheel (19) is connected to the shaft II (33) in a keyed manner.

4. The device for testing the dynamic torsional fatigue mechanical properties under the tensile preload according to claim 1, wherein: the force signal and displacement signal detection unit comprises a tension sensor (14), a torque sensor (17), a linear grating displacement sensor and an encoder (20); one end of the tension sensor (14) is connected to the nut support (13) through threads, and the other end of the tension sensor is connected to the clamp body support I (15); one end of the torque sensor (17) is connected to the shaft II (33) in a flange connection mode, and the other end of the torque sensor is connected to the clamp body II (24); the linear grating displacement sensor comprises a grating ruler (36) and a reading head (37), the grating ruler (36) is fixed on the bottom plate (2) through a grating ruler support (35), the reading head (37) is fixed on the clamp body support I (15), and deformation of a test piece is indirectly measured through measuring displacement of the clamp body support I (15); the encoder (20) is connected with the shaft II (33) through an encoder coupler (32) to realize measurement of reciprocating rotation angle and fatigue cycle, wherein the encoder (20) is fixedly connected on the bottom plate (2) through a support (31).

5. The device for testing the dynamic torsional fatigue mechanical properties under the tensile preload according to claim 1, wherein: the test piece clamping unit comprises pressing plates I and II (25 and 26) and clamp bodies I and II (27 and 24), wherein the clamp body I (27) is connected to a clamp body support I (15) through threads, and the clamp body II (24) is connected to the bottom plate (2) through a clamp body support II (16); the clamp comprises a clamp body I, a clamp body II, a clamp plate I, a clamp plate II, a clamp plate III, a clamp plate.

6. The device for testing the dynamic torsional fatigue mechanical properties under the tensile preload according to claim 3, wherein: the gear (19) and the rack (22) adopt a double-thick gear staggered structure to eliminate meshing gaps, so that the output displacement of the electromagnetic vibration exciter (21) is completely converted into the torsional displacement of the test piece (41); the height-adjustable bottom plate (29) is used for adjusting the radial clearance of the meshing of the gear and the rack, the height-adjustable bottom plate (29) is positioned through four trapezoidal grooves, and the height is adjusted through four flat head screws below the bottom plate.