CN116165056A - High-speed rotation bending fatigue stress and temperature synchronous test board and measurement method - Google Patents

Abstract

A high-speed rotation bending fatigue stress and temperature synchronous test board and a measuring method mainly comprise a supporting seat, wherein a hollow shaft is rotatably arranged on the supporting seat, one end of the hollow shaft is fixedly provided with a sample, a strain gauge and a thermocouple are arranged on the sample, a stress signal lead of the strain gauge and a thermocouple signal lead of the thermocouple penetrate through the hollow shaft and are correspondingly connected with a sleeve combined electrode, and the sleeve combined electrode is fixed at the other end of the hollow shaft; the other end of the sleeve combined electrode correspondingly penetrates through the sealing bearings and the liquid metal of the plurality of groups of liquid metal conducting devices, the plurality of groups of liquid metal conducting devices are electrically connected with the dynamic signal acquisition instrument 13, and the dynamic signal acquisition instrument is electrically connected with the machine. The high-speed rotation bending fatigue stress and temperature synchronous test board and the measurement method provided by the invention can accurately measure the stress of the high-speed rotation fatigue test sample and the temperature rise real-time change process caused by fatigue.

Description

High-speed rotation bending fatigue stress and temperature synchronous test board and measurement method

Technical Field

The invention relates to the technical field of rotating bending fatigue testing, in particular to a high-speed rotating bending fatigue stress and fatigue temperature synchronous testing platform and a measuring method.

Background

The high-speed rotating bending fatigue test is mainly used for measuring the fatigue life of a smooth sample of a material under cyclic alternating bending load, and a relation curve of fatigue limit stress sigma (nominal stress) and fatigue life (cycle number) N is called a stress-life curve or an S-N curve. The number of cycles experienced before a material fatigue fracture is the fatigue life under that load. Fatigue life typically involves four stages of crack nucleation, micro-crack propagation, macro-crack propagation, and final fracture. The analysis of the fatigue fracture cause, fracture properties, fracture modes, fracture mechanisms, stress states of the fracture process and crack propagation rates at present mainly utilizes fatigue fractures. Although fracture morphology records some fracture process stress states, there is a large deviation from the true alternating stress states experienced by the material fatigue process. Fatigue fracture is a low stress plastic strain accumulation damage, the material fatigue process is subjected to elastic-to-plastic transformation, and the stress state is necessarily changed in real time.

In addition, from a material perspective, the low stress plastic strain energy generated during fatigue can be converted to thermal energy causing a localized temperature increase in the material. Therefore, fatigue temperature evolution is very closely related to fatigue life as an associated phenomenon in metal fatigue process. The temperature change is used as a fatigue performance evaluation index, so that the fatigue limit and the fatigue life of the material can be rapidly predicted. In recent years, although the temperature field of a fatigue specimen under different loads can be measured by non-contact temperature measurement means such as infrared thermal imaging, infrared thermal imaging is greatly affected by factors such as specimen material, surface finish, fatigue amplitude, environment and the like. In particular to a high-speed rotation bending fatigue test, the rotation speed of a sample is high, the radial amplitude is large, the heat loss is fast, and a great error is brought to a temperature measurement result. In order to improve the fatigue life prediction precision and reduce the uncertainty of the measurement process, the fatigue damage assessment of various characteristic quantity coupling is carried out on the basis of the real fatigue alternating stress and the fatigue temperature rise as test, and the method has become an important means for fatigue damage test analysis.

The signal transmission of the existing continuous rotating mechanism usually adopts a conductive slip ring, also called a collector ring, a rotating joint, a collector ring, an adapter, a commutator and the like, and the structure mainly comprises a stator and a rotor, wherein an electric brush is fixed on the stator or the rotor and is in electrical contact with the conductive ring on the corresponding stator or rotor to carry out power transmission and data transmission. When the rotational speed is low (< 1000 r/min), partial signal measurements can be made with the conductive slip ring. However, when the rotor rotates at a high speed, the brushes and the conductive ring are caused to rub rapidly, so that the abrasive grains on the surface are increased, and meanwhile, the temperature is increased due to frictional heat generation. The abrasion mark abrasive particles can cause contact resistance to change to cause a large amount of interference signals, and the temperature rise can cause signal drift to cause measurement signal distortion. In addition, the bending fatigue test sample is small in size, so that the use of the conductive slip ring is limited. How to realize the online real-time transmission of the contact type measuring signals of the high-speed rotating mechanism without interference, drift and distortion has become a great difficulty.

Disclosure of Invention

The invention aims to solve the technical problem of providing a high-speed rotation bending fatigue stress and temperature synchronous test board and a measurement method, which are used for accurately measuring the temperature rise real-time change process caused by stress and fatigue of a high-speed rotation fatigue sample while obtaining a common S-N curve, wherein a measurement signal is real fatigue alternating stress and fatigue temperature, and the signal has no interference and no drift and does not need to be processed.

In order to solve the technical problems, the invention adopts the following technical scheme:

a high-speed rotation bending fatigue stress and temperature synchronous test board comprises a supporting seat, wherein a hollow shaft is rotatably arranged on the supporting seat, and the hollow shaft is driven to rotate at a high speed through a driving device; a sample is fixed at one end of the hollow shaft, a strain gauge and a thermocouple are arranged on the sample, a stress signal lead of the strain gauge and a thermocouple signal lead of the thermocouple penetrate through the hollow shaft and are correspondingly connected with a sleeve combined electrode, and the sleeve combined electrode is fixed at the other end of the hollow shaft;

each group of electrodes of the sleeve combined electrode correspondingly passes through a group of liquid metal conducting devices, and the liquid metal conducting devices are sequentially and electrically connected with the dynamic signal acquisition instrument and the computer.

The sleeve combined electrode comprises a conductive stress sleeve negative electrode, a conductive stress sleeve positive electrode, a conductive thermowell negative electrode and a conductive thermowell positive electrode, wherein the stress sleeve negative electrode, the conductive stress sleeve positive electrode, the conductive thermowell negative electrode and the conductive thermowell positive electrode are mutually sleeved and then are adhered and fixed by insulating glue and are kept insulated.

The four electrodes of the sleeve combined electrode are gradually lengthened from outside to inside and extend from left to right.

The liquid metal conductive device comprises a liquid metal device wall, the liquid metal device wall is connected with a liquid metal device end socket to form a sealed container, a sealed bearing for a sleeve combined electrode to pass through in a sealing mode is arranged on the left side and the right side of the sealed container, liquid metal is arranged in the sealed container, and a signal wire connector is arranged on one side of the sealed container.

The liquid metal is gallium-indium-based alloy which is liquid at normal temperature, so that the rotary sleeve combined electrode immersed in the liquid metal at the normal temperature is ensured to realize non-contact signal communication with the signal wire connector.

The hollow shaft is fixed with the sample and the hollow shaft is fixed with the sleeve combined electrode through a spring chuck, and the spring chuck is correspondingly provided with a wire passing hole.

The high-speed rotation bending fatigue stress and temperature synchronous test board is characterized in that the high-speed rotation fatigue alternating stress of a sample is collected in real time through a strain gauge, and the fatigue temperature is collected through a thermocouple; the acquisition signal is coaxially output through a lead wire and then connected with the sleeve combined electrode; the sleeve combined electrode is fixed on the hollow shaft by a spring chuck and synchronously rotates with the sample; the four electrodes of the sleeve combined electrode respectively penetrate through and are immersed in the four independent liquid metal conductive devices; when the sleeve pipe combined electrode rotates at a high speed, signals are transmitted to the dynamic signal acquisition instrument through liquid metal in the liquid metal conductive device, and acquired data are recorded in real time through a computer through a data line.

A method for synchronously measuring high-speed rotation bending fatigue stress and temperature comprises the following steps:

step one: firstly, a strain gauge, a stress signal lead, a thermocouple and a thermocouple signal lead pass through a spring chuck and a hollow shaft; the positive electrode and the negative electrode of the stress signal lead are correspondingly connected with the positive electrode and the negative electrode of the stress sleeve of the sleeve combined electrode; the positive electrode and the negative electrode of the thermocouple signal lead are correspondingly connected with the positive electrode and the negative electrode of the thermowell of the sleeve combined electrode; then, sticking the strain gauge and the thermocouple on the sample, and fixing one end of the sample on the hollow shaft by using a spring chuck;

step two: fixing the mounting joint at the other end of the sample, and hanging a weight tray according to the fatigue load;

step three: penetrating the sleeve combined electrode into the C-shaped adapter tube clamp, and fixing the sleeve combined electrode together at one end of the hollow shaft by using the spring chuck;

step four: after the four electrodes extending out of the sleeve combined electrode correspondingly pass through the four mutually independent liquid metal conducting devices, liquid metal is injected into the liquid metal conducting devices, so that the four electrodes extending out of the sleeve combined electrode are immersed and pass through the liquid metal corresponding to the liquid metal conducting devices;

step five: a plurality of groups of signal wires are correspondingly connected with a liquid metal conducting device and a dynamic signal acquisition instrument respectively, a data wire is connected with a computer and the dynamic signal acquisition instrument, stress and temperature acquisition control software is opened, parameters are adjusted to clear the balance of the bridge, and fatigue alternating stress and fatigue temperature data are prepared to be acquired;

step six: starting a high-speed motor, driving the driving wheel and the hollow shaft to rotate by a belt, and recording the fatigue cycle times by a counter;

step seven: after the sample breaks, stopping the high-speed motor, and reading the number of times of fatigue life recorded by the control box to obtain primary S-N data;

step eight: stopping stress and temperature acquisition control software, and storing fatigue fracture life-time stress change and a fatigue temperature curve;

step nine: repeating the above steps to complete the S-N curve and the real-time stress and temperature change curve.

The invention relates to a high-speed rotation bending fatigue stress and fatigue temperature synchronous test platform and a measurement method, which have the following technical effects:

1) Compared with the existing bending fatigue test device, the device can be used for measuring the bending fatigue stress and the fatigue temperature of the high-speed rotation on line in real time while obtaining a general stress-life curve (S-N curve). The invention can provide real and effective alternating stress and fatigue temperature rise change data for deep research of fatigue accumulated damage fracture problem of high-speed rotating shaft parts, is helpful for revealing the material accumulated damage mechanism under the action of fatigue alternating load, obtains accurate accumulated damage model, realizes accurate prediction of the service life of the high-speed rotating shaft parts, and prevents the occurrence of high-speed rotating fatigue fracture accident of the shaft parts.

2) Because the liquid metal is adopted as the signal transmission medium of the rotating mechanism, friction does not occur when the rotating electrode and the liquid metal transmit signals, so that the problems of signal interference and drift caused by high-speed rotation friction abrasion marks and friction temperature rise of the traditional conductive device such as a contact conductive slip ring and the like are avoided, and the real and accurate measurement of high-speed rotation bending fatigue alternating stress and fatigue temperature without interference and drift is realized.

3) The coaxial signal transmission design is adopted, the testing device is separated from the test object, no additional force is generated on the sample, and the measurement result is not influenced; in addition, when the test sample is replaced, the test device is not required to be disassembled for permanent use.

4) The patent with the application number of 201720985741.9 is a liquid metal conductive slip ring, adopts a ring body and conductor structure, fills with an amateur metal in the ring body, and inserts the conductor into the cavity of the ring body, so that the transmission of electric signals can be realized. However, the conductor of the device is a conducting strip, and the conducting strip does not pass through liquid metal and can only output a first-level signal; the columnar electrodes are coaxially arranged, and a plurality of groups of liquid metals independently penetrate through the corresponding groups of liquid metals, so that multistage signals can be coaxially output. If the fatigue signal (positive electrode and negative electrode) and the temperature signal (positive electrode and negative electrode) need 4 electrodes to coaxially rotate to output signals, the device can be realized, but the comparison file can only output 1 electrode, and the multipole signal coaxial output cannot be realized.

Drawings

The invention is further illustrated by the following examples in conjunction with the accompanying drawings:

FIG. 1 is a schematic diagram of the structure of the present invention.

Fig. 2 is a schematic diagram showing connection between a signal line and a sleeve combined electrode in the present invention.

Fig. 3 is a schematic diagram showing connection between the sleeve combined electrode and the liquid metal conductive device in the invention.

FIG. 4 is a schematic diagram of a complete transmission path of a spin-on variable stress measurement signal according to the present invention.

FIG. 5 is a schematic view of a fatigue-life measuring device according to the present invention.

FIG. 6 is a schematic diagram of a counting device according to the present invention.

Fig. 7 is a schematic view of a weight loading device according to the present invention.

Fig. 8 is a schematic view of a signal lead through a spring clip according to the present invention.

FIG. 9 is a graph showing actual measurement of high-speed rotation bending alternating fatigue stress and fatigue temperature in the present invention.

FIG. 10 is a partial enlarged view of fatigue stress versus fatigue temperature in the present invention.

In the figure: the high-speed motor 1, the mounting joint 2, the sample 3, the strain gauge 4, the stress signal lead 5, the stress lead positive electrode 51, the stress lead negative electrode 52, the collet chuck 6, the stress wire hole 61, the temperature wire hole 62, the weight plate 7, the hook 71, the thermocouple 8, the thermocouple signal lead 9, the thermocouple lead positive electrode 91, the thermocouple lead negative electrode 92, the counter 10, the counting wire 101, the control box 11, the power control wire 112, the support base 12, the liquid gold conductive support table 121, the rotating shaft support base 122, the dynamic signal collector 13, the computer 14, the data wire 15, the stress signal lead negative electrode 16, the stress signal lead positive electrode 161, the thermocouple signal lead negative electrode 162, the thermocouple signal lead positive electrode 163, the liquid metal conductive device 17, the liquid gold device head 171, the liquid gold device wall 172, the sealing bearing 173, the thermocouple conductive post positive electrode 174, the thermocouple conductive post negative electrode 175, the stress conductive post positive electrode 176, the conductive post negative electrode 177, the liquid metal 178, the well combination electrode 18, the well 181, the well positive electrode 182, the well 183, the well bridge wire 184, the c-shaped junction 19, the hollow shaft bearing 21, the high-speed tube clamp 21, the thermocouple wire hole 212, the belt clamp 21, the belt pulley hole 212, the top groove 212.

Detailed Description

As shown in fig. 1 and 5, a high-speed rotation bending fatigue stress and temperature synchronous test board and a measurement method thereof comprise a support base 12, wherein a liquid-metal conductive support base 121 and a rotating shaft support base 122 are fixed on the support base 12. The liquid metal conductive support table 121 is used for installing the liquid metal conductive device 17, two sets of rotating shaft support seats 122 are provided, and the left and right hollow shafts 20 are rotatably installed on the rotating shaft support seats 122 through bearings. The hollow shaft 20 is driven to rotate by a belt conveying mechanism consisting of a driving wheel 21 and a belt 22 and a high-speed motor 1. The rotation speed of the high-speed motor 1 is 3000-20000 r/min and is adjustable.

As shown in fig. 1 and 8, a collet 6 is fixed at one end of the hollow shaft 20, and a stress wire through hole 61 and a temperature wire through hole 62 are provided on the collet 6, wherein the stress wire through hole 61 is used for the stress signal lead 5 to pass through, and the temperature wire through hole 62 is used for the thermocouple signal lead 9 to pass through. The sample 3 is mounted on the hollow shaft 20 by means of the collet 6.

As shown in fig. 1-2, the strain gauge 4 and the thermocouple 8 are mounted on the sample 3, wherein the strain gauge is a temperature self-compensating strain gauge, and the thermocouple is any one of a welding spot type K type, an S type, an E type, an N type, a J type, an R type and a T type.

The stress signal lead 5 of the strain gauge 4 and the thermocouple signal lead 9 of the thermocouple 8 correspondingly pass through the stress wire through hole 61 and the temperature wire through hole 62 and then correspondingly connect with the sleeve combined electrode 18. The sleeve combined electrode 18 is inserted into the C-shaped transfer pipe clamp 19 by interference fit, and then the C-shaped transfer pipe clamp 19 is locked at one end of the hollow shaft 20 by the spring chuck 6.

The stress signal lead 5 includes a stress lead positive electrode 51 and a stress lead negative electrode 52.

The couple signal lead 9 comprises a couple lead positive electrode 91 and a couple lead negative electrode 92.

As shown in fig. 3, the sleeve combined electrode 18 comprises 4 groups of electrodes, namely a stress sleeve negative electrode 181, a stress sleeve positive electrode 182, a thermowell negative electrode 183 and a thermowell positive electrode 184; wherein, stress lead anode 52 is electrically connected to stress sleeve anode 181, stress lead anode 51 is electrically connected to stress sleeve anode 182, thermocouple lead anode 91 is electrically connected to thermocouple sleeve anode 184, and thermocouple lead anode 92 is electrically connected to thermocouple sleeve anode 183.

The stress sleeve negative electrode 181, the stress sleeve positive electrode 182, the thermowell negative electrode 183 and the thermowell positive electrode 184 are formed by processing metal materials. The stress sleeve anode 181, the stress sleeve cathode 182, the thermowell anode 183 and the thermowell anode 184 are mutually sleeved, then are bonded and fixed by using insulating glue and are mutually insulated, so that mutual noninterfere is ensured.

As shown in fig. 3, the four electrodes of the sleeve combined electrode 18 are gradually elongated from outside to inside and gradually extend from left to right. As in the present embodiment, of the 4 sets of electrodes, thermowell anode 184 is located at the shortest outermost layer, thermowell cathode 183 is nested within thermowell anode 184 and both ends extend out of thermowell anode 184; the stress sleeve anode 182 is nested in the thermowell cathode 183 and both ends extend out of the thermowell cathode 183; the stress sleeve anode 181 is nested within the stress sleeve cathode 182 and both ends extend beyond the stress sleeve anode 182.

As shown in fig. 3, the four sets of electrodes of the sleeve combined electrode 18 respectively pass through one set of liquid metal conducting devices 17, as shown in fig. 3 of this embodiment, the four sets of liquid metal conducting devices 17 are respectively marked a, b, c, d from right to left, the positive electrode 184 of the thermowell passes through a and contacts the liquid metal 178 in a, the negative electrode 183 of the thermowell passes through b and contacts the liquid metal 178 in b, the positive electrode 182 of the stress sleeve passes through c and contacts the liquid metal 178 in c, and the negative electrode 181 of the stress sleeve passes through d and contacts the liquid metal 178 in d. The sleeve combination electrode 18, when rotated in the liquid metal 178, may transmit a temperature signal through the liquid metal 178 to the head signal lead connector.

As shown in fig. 3-4, each group of liquid metal conducting devices 17 comprises a liquid metal device wall 172, the liquid metal device wall 172 is connected with a liquid metal device seal head 171 to form a sealed container, sealing bearings 173 for the sleeve combined electrode 18 to pass through in a sealing manner are arranged on the left and right sides of the sealed container, and the sealing bearings 173 are high-speed waterproof bearings. The sealed container is provided with liquid metal 178, and one side of the sealed container is provided with a group of signal wire connectors. The four signal wire connectors of the four sets of liquid metal conductive devices 17 are thermocouple conductive post anodes 174, thermocouple conductive post cathodes 175, stress conductive post anodes 176, thermocouple conductive post cathodes 177, respectively. The sleeve combination electrode 18 transmits signals through the liquid metal to the four sets of signal conductor joints of the liquid metal conducting means 17 as it rotates in the liquid metal.

Both the liquid metal device wall 172 and the liquid metal device head 171 are made of insulating rubber materials, and the seal bearing 173 is made of insulating ceramic wear-resistant materials.

The sealing container formed by connecting the liquid gold device wall 172 with the liquid gold device end socket 171 and the high-speed waterproof sealing bearing 173 can prevent the conductive liquid gold from leaking in the high-speed rotation process of the sleeve combined electrode 18.

Preferably, the liquid metal 178 is a gallium-indium-based alloy that is liquid at normal temperature, so as to ensure that the stress sleeve anode 181, the stress sleeve anode 182, the thermowell anode 183, and the thermowell anode 184 immersed therein are in non-contact signal communication with the thermocouple conductive post anode 174, the thermocouple conductive post anode 175, the stress conductive post anode 176, and the thermocouple conductive post anode 177.

As shown in fig. 4, a dynamic signal collector 13 is mounted on one side of the workbench, and stress signal wire cathodes 16, stress signal wire anodes 161, thermocouple signal wire cathodes 162, thermocouple signal wire anodes 163, stress signal wire cathodes 16, stress signal wire anodes 161, thermocouple signal wire cathodes 162, and thermocouple signal wire anodes 163 are respectively connected to the four groups of signal wire joints of the four groups of liquid metal conductive devices 17, and the other ends of the stress signal wire cathodes 16, the stress signal wire anodes 161, the thermocouple signal wire cathodes 162, and the thermocouple signal wire anodes 163 are connected to the dynamic signal collector 13. The dynamic signal acquisition instrument 13 is electrically connected with the computer 14 through a data line 15.

As shown in fig. 6, the driving wheel 21 is provided with a counting hole 211, a counter 10 is installed at a proper position below the driving wheel 21, and the counter 10 is connected with the control box 11 through a counting lead 101. The count is made by the counter 10 for recording the number of fatigue life times.

As shown in fig. 7, a mount joint 2 is fixed to the other end of the sample 3, and a weight tray 7 is hung on the mount joint 2. In the device, power is provided by a high-speed motor, a test sample is driven to rotate through a belt and a driving wheel, the test sample applies fatigue load through weights, the fatigue cycle number is recorded by a counter, the test is stopped after the test sample is broken, the cycle number of the counter is read, and an S-N curve is drawn according to the fatigue load and the cycle number after the array test is repeatedly completed.

A high-speed rotation bending fatigue stress and temperature synchronous test board and a measuring method thereof comprise the following steps:

step one: as shown in fig. 4-5 and 8, the strain gauge 4, the stress signal lead 5, the thermocouple 8 and the thermocouple signal lead 9 are first passed through the collet 6 and the hollow shaft 20. Then the stress lead positive electrode 51 and the stress lead negative electrode 52 are correspondingly connected with the stress sleeve positive electrode 182 and the stress sleeve negative electrode 181 of the sleeve combined electrode 18; the thermocouple lead positive electrode 91 and the thermocouple lead negative electrode 92 are correspondingly connected with the thermocouple well positive electrode 184 and the thermocouple well negative electrode 183 of the well combined electrode 18; then, the strain gauge 4 and the thermocouple 8 are adhered to the sample 3, and one end of the sample 3 is fixed to the hollow shaft 20 by the collet chuck 6.

Step two: the mounting joint 2 is fixed at the other end of the sample 3, and the weight tray 7 is hung according to fatigue load.

Step three: the sleeve combined electrode 18 is inserted into the C-shaped adapter tube clamp 19, and the sleeve combined electrode 18 is fixed together at one end of the hollow shaft 20 by the collet chuck 6.

Step four: after the four electrodes (the stress sleeve negative electrode 181, the stress sleeve positive electrode 182, the thermowell negative electrode 183 and the thermowell positive electrode 184) extending from the sleeve combined electrode 18 respectively pass through the four mutually independent liquid metal conducting devices 17, the liquid metal 178 is injected into the liquid metal conducting devices 17, so that the stress sleeve negative electrode 181, the stress sleeve positive electrode 182, the thermowell negative electrode 183 and the thermowell positive electrode 184 are immersed in and pass through the liquid metal 178.

Step five: the stress signal wire cathode 16, the stress signal wire anode 161, the thermocouple signal wire cathode 162 and the thermocouple signal wire anode 163 are respectively and correspondingly connected with the liquid metal conductive column stress conductive column cathode 177, the stress conductive column anode 176, the thermocouple conductive column cathode 175, the thermocouple conductive column anode 174 and the dynamic signal acquisition instrument 13, the computer 14 and the dynamic signal acquisition instrument 13 are connected by the data wire 15, stress and temperature acquisition control software is opened, parameters are adjusted to clear the balance of the bridge, and data acquisition is prepared.

Step six: the high-speed motor 1 is started, the belt 22 drives the driving wheel 21 and the hollow shaft 20 to rotate, and the counter 10 records the fatigue cycle times.

Step seven: after the sample breaks, the high-speed motor 1 is stopped, and the read control box 11 records the number of times of fatigue life.

Step eight: stopping the stress and temperature acquisition control software, and storing the fatigue fracture life-time stress change and the fatigue temperature curve, wherein the result is shown in fig. 9, and the acquired fatigue alternating stress and fatigue temperature data have no interference signals and no signal drift; as shown in fig. 10, when the stress ratio r= -1 of the rotation bending fatigue alternating stress, the fatigue alternating stress is measured as a sine wave rule, and the fatigue temperature is in an ascending trend.

Claims (8)

1. A high-speed rotation bending fatigue stress and temperature synchronous test board is characterized in that: the device comprises a supporting seat (12), wherein a hollow shaft (20) is rotatably arranged on the supporting seat (12), and the hollow shaft (20) is driven to rotate at a high speed through a driving device; a sample (3) is fixed at one end of the hollow shaft (20), a strain gauge (4) and a thermocouple (8) are arranged on the sample (3), a stress signal lead (5) of the strain gauge (4) and a thermocouple signal lead (9) of the thermocouple (8) penetrate through the hollow shaft (20) and are correspondingly connected with a sleeve combined electrode (18), and the sleeve combined electrode (18) is fixed at the other end of the hollow shaft (20);

each group of electrodes of the sleeve combined electrode (18) correspondingly penetrates through a group of liquid metal conducting devices (17), and the liquid metal conducting devices (17) are electrically connected with the dynamic signal acquisition instrument (13) and the computer (14) in sequence.

2. The high-speed rotating bending fatigue stress and temperature synchronization test stand according to claim 1, wherein: the sleeve combined electrode (18) comprises a conductive stress sleeve negative electrode (181), a stress sleeve positive electrode (182), a thermowell negative electrode (183) and a thermowell positive electrode (184), wherein the stress sleeve negative electrode (181), the stress sleeve positive electrode (182), the thermowell negative electrode (183) and the thermowell positive electrode (184) are mutually sleeved and then are adhered and fixed by using insulating glue, and are kept insulated.

3. The high-speed rotating bending fatigue stress and temperature synchronization test stand according to claim 2, wherein: four electrodes of the sleeve combined electrode (18) are gradually lengthened from outside to inside and gradually extend from left to right.

4. A high-speed rotational bending fatigue stress and temperature synchronization test stand according to claim 3, wherein: the liquid metal conductive device (17) comprises a liquid metal device wall (172), the liquid metal device wall (172) is connected with a liquid metal device end socket (171) to form a sealed container, a sealed bearing (173) for a sleeve combined electrode (18) to pass through in a sealing mode is arranged on the left side and the right side of the sealed container, liquid metal (178) is arranged in the sealed container, and a signal wire connector is arranged on one side of the sealed container.

5. The high-speed rotating bending fatigue stress and temperature synchronization test stand according to claim 4, wherein: the liquid metal (178) is a gallium-indium based alloy that is liquid at normal temperature.

6. The high-speed rotating bending fatigue stress and temperature synchronization test stand according to claim 5, wherein: the hollow shaft (20) and the sample (3) and the hollow shaft (20) and the sleeve combined electrode (18) are fixed through a C-shaped transfer pipe clamp (19) with an insulating layer coated on the inner wall and a collet chuck (6), and the collet chuck (6) is correspondingly provided with a wire passing hole.

7. The high-speed rotational bending fatigue stress and temperature synchronization test stand according to claim 6, wherein: the high-speed rotation fatigue alternating stress of the sample (3) is collected in real time through the strain gauge (4), and the fatigue temperature is collected through the thermocouple (8); the acquisition signal is coaxially output through a lead wire and then is connected with a sleeve combined electrode (18); the sleeve combined electrode (18) is fixed on the hollow shaft (20) by the spring chuck (6) and rotates synchronously with the sample (3); four electrodes of the sleeve combined electrode (18) respectively penetrate through and are immersed in four independent liquid metal conducting devices (17); when rotating at high speed, the sleeve combined electrode (18) transmits signals to the dynamic signal acquisition instrument (13) through liquid metal in the liquid metal conductive device (17), and the computer (14) records acquired data in real time through a data wire.

8. The method for synchronously testing the high-speed rotation bending fatigue stress and the temperature according to claim 7, comprising the following steps:

step one: firstly, a strain gauge (4), a stress signal lead (5), a thermocouple (8) and a thermocouple signal lead (9) penetrate through a collet chuck (6) and a hollow shaft (20); the positive electrode and the negative electrode of the stress signal lead (5) are correspondingly connected with the positive electrode and the negative electrode of a stress sleeve of the sleeve combined electrode (18); the positive electrode and the negative electrode of the thermocouple signal lead (9) are correspondingly connected with the positive electrode and the negative electrode of a thermowell of the sleeve combined electrode (18); then, sticking the strain gauge (4) and the thermocouple (8) on the sample (3), and fixing one end of the sample (3) on the hollow shaft (20) by using the collet chuck (6);

step two: fixing the mounting joint (2) at the other end of the sample (3), and hanging a weight tray (7) according to fatigue load;

step three: penetrating the sleeve combined electrode (18) into the C-shaped adapter tube clamp (19), and fixing the sleeve combined electrode (18) together at one end of the hollow shaft (20) by using the spring chuck (6);

step four: after correspondingly penetrating through the four mutually independent liquid metal conducting devices (17), the four electrodes extending out of the sleeve combined electrode (18) are injected with liquid metal (178) into the liquid metal conducting devices (17), so that the four electrodes extending out of the sleeve combined electrode (18) are immersed in and penetrate through the liquid metal (178) corresponding to the liquid metal conducting devices (17);

step five: a plurality of groups of signal wires are correspondingly connected with a liquid metal conducting device (17) and a dynamic signal acquisition instrument (13) respectively, a data wire (15) is connected with a computer (14) and the dynamic signal acquisition instrument (13), stress and temperature acquisition control software is opened, parameters are adjusted to clear the balance of the bridge, and fatigue alternating stress and fatigue temperature data are prepared to be acquired;

step six: starting a high-speed motor (1), driving a driving wheel (21) and a hollow shaft (20) to rotate by a belt (22), and recording fatigue cycle times by a counter (10);

step seven: after the sample breaks, stopping the high-speed motor (1), and reading the number of times of fatigue life recorded by the control box (11) to obtain primary S-N data;

step eight: stopping stress and temperature acquisition control software, and storing fatigue fracture life-time stress change and a fatigue temperature curve;

step nine: repeating the above steps to complete the S-N curve and the real-time stress and temperature change curve.

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