A micro-motion testing device and its testing method suitable for high-temperature environments

Abstract

This invention proposes a micro-motion testing device and method suitable for high-temperature environments. The micro-motion testing device includes a normal load loading device, a micro-motion pad limiting device, a tangential load loading device, a high-temperature loading device, a test piece, and a micro-motion pad. The normal load loading device includes a split-type stress ring, loading bolts, anti-loosening nuts, a loading box, a sensor assembly, a linear bearing, a loading connecting rod, and a water-cooling device. The split-type stress ring is bolted together to form a complete stress ring, facilitating installation and disassembly during testing. Tightening the loading bolts generates a normal compressive force, which is sequentially transferred to the test piece through the sensor assembly, the loading connecting rod, and the micro-motion pad. The loading connecting rod passes through the linear bearing and is mounted on the split-type stress ring, reducing the loss of normal load transmission and improving coaxiality. A water-cooling device is located near the linear bearing on the split-type stress ring to cool the linear bearing and prevent heat transfer to the sensor assembly.

Description

Technical Field

[0001] This invention belongs to the field of aerospace engine technology, specifically relating to a micro-motion testing device and method suitable for high-temperature environments, used for conducting micro-motion damage assessment of high-temperature components of aero-engines. Background Technology

[0002] Under the coupled action of alternating amplitude loads such as force vibration and temperature cycling, the contact surfaces of connectors will undergo relative motion with displacement amplitude on the order of micrometers, known as fretting. Fretting between the contact surfaces of structural components can promote the formation of cracks, crack propagation, and even fracture at the damaged site. This process is called fretting fatigue, which accelerates the failure of structural components and leads to a significant reduction in the structural life of some connectors. It is one of the important causes of structural failure and is known as the "cancer" of industry.

[0003] In the aerospace industry, fretting fatigue is a significant source of failures. Statistics show that approximately one-sixth of aero-engine failures are caused by fretting fatigue. The turbine disk and blades of an aero-engine are connected by a tenon joint structure. At extremely high speeds, vibrations, inertial forces caused by blade aerodynamics, and temperature loads (approximately 600°C) constitute the contact load on the contact surface. Under this load, high stress concentration and wear occur at the edges of the contact area, leading to crack formation and a decrease in fatigue life, making fretting fatigue the primary failure mode of tenon joint structures. To assess the fretting fatigue life of aero-engine tenon joint structures, fretting tests are necessary to reveal the failure mechanisms of fretting fatigue and fretting wear. Due to the multiaxial load characteristics of fretting tests, especially since fretting fatigue testing is still a typical non-standard test, the design of the test equipment remains the biggest challenge in conducting experimental research.

[0004] Current fretting testing devices are mainly based on modified fatigue testing machines. While applying tangential loads using a uniaxial fatigue testing machine, a separately designed loading device applies normal loads. Among these, the stress ring device, designed using a self-balancing force system loading principle, has become a common choice for applying normal loads in high-temperature environments due to its advantages. For example, Chinese invention patent application CN110208108 A (A Single-Clip Fretting Fatigue Testing Device Suitable for High Temperatures) proposes a feasible scheme for conducting fretting fatigue tests in high-temperature environments. This scheme uses a purely mechanical device for normal load application, namely a bolt-loaded stress ring device. Its structure is compact, and the loading is simple and reliable, making it particularly suitable for high-temperature environments. To avoid interference with the normal and tangential loading devices, the high-temperature furnace is divided into three relatively independent parts. Furthermore, to avoid arranging sensors in a high-temperature environment, strain gauges are attached to the stress ring to measure strain, thereby indirectly converting it into a normal load.

[0005] However, existing technical solutions have their own shortcomings and are difficult to meet the needs of conducting fretting fatigue and fretting wear tests in high-temperature environments. The specific shortcomings are as follows:

[0006] (1) Existing technical solutions mostly use an integral stress ring for normal load loading, which requires the use of a customized split high-temperature furnace for heating. The test device is heavy and the installation process is complicated and cumbersome, which is not conducive to the development of fretting tests.

[0007] (2) In the existing technical solution, the micro-motion pad is directly matched with the centering or limiting device. Due to the influence of dimensional tolerance, there is an assembly gap. Under the action of tangential load, the micro-motion pad will rotate rigidly, which affects the uniformity of normal load loading on the one hand, and the accuracy of tangential load on the other hand.

[0008] (3) Existing technical solutions mostly arrange strain gauges on the stress ring and establish the relationship between strain and normal load through the finite element method, and then indirectly measure the normal load. Due to the influence of various factors such as simulation model, processing, strain gauge bonding, and friction loss, the systematic error is large and the measurement accuracy of normal load is poor. Summary of the Invention

[0009] To overcome the shortcomings of existing technical solutions, this invention provides a fretting test device and its test method suitable for high-temperature environments. It can fully meet the requirements of normal load neutrality, tangential load accuracy, and installability, and can effectively carry out fretting wear and fretting fatigue tests on material-level test pieces, serving and supporting the fretting fatigue performance evaluation of high-temperature components of aero-engines.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A fretting test device suitable for high-temperature environments includes a normal load loading device, a fretting pad limiting device, a tangential load loading device, a high-temperature loading device, and corresponding test pieces and fretting pads. The normal load loading device includes a split-type stress ring, loading bolts, anti-loosening nuts, a loading box, a sensor assembly, a linear bearing, a loading connecting rod, a water cooling device, and a stress ring water-cooling pipe joint. The split-type stress rings are connected by bolts to form a complete stress ring, achieving synchronous and stable loading of the normal load. The split-type design facilitates test installation. Tightening the loading bolts generates a normal clamping force, which is sequentially transmitted to the test piece through the sensor assembly, loading connecting rod, and fretting pad. The loading connecting rod... The linear bearing is mounted on the split-half stress ring to reduce the loss of normal load transmission and improve coaxiality. Water-cooling devices are installed on the upper and lower end faces of the split-half stress ring near the linear bearing to cool the bearing and prevent heat transfer to the sensor assembly. The micro-motion pad limiting device includes a support housing, a bearing cover, an adjusting bolt, and a shaped split-half linear bearing. The adjusting bolt tightens the micro-motion pad, eliminating the clearance between the micro-motion pad and the support housing, ensuring precise control during tangential load application. The shaped split-half linear bearing reduces the coefficient of friction between the micro-motion pad and the support housing, minimizing the loss of normal load transmission caused by the preload introduced by the adjusting bolt during clearance elimination. The tangential load loading device is a water-cooled tensile clamp, consisting of an upper clamp and a lower clamp, which are completely symmetrical. Both the upper and lower clamps include a test piece clamp, a clamping section, a clamp water-cooled pipe joint, a limiting device tightening bolt, and a test piece tightening bolt. One end of the test piece clamp is connected to the test piece and the micro-movement pad limiting device, and the other end is connected to the clamping section. The other end of the clamping section is connected to the fatigue testing machine. Periodic tangential loads are applied by the fatigue testing machine and transferred to the test piece sequentially through the clamping section and the test piece clamp. The high-temperature loading device is a split-type high-temperature furnace, which is placed inside the split-type stress ring. It includes a left furnace body and a right furnace body connected by hinges. The high-temperature furnace is provided with mutually perpendicular tangential loading holes and normal loading holes, which pass through the tangential load loading device and the normal load loading device, respectively. A rectangular observation window is provided in the middle of the opening and closing surfaces of the left and right furnace bodies for auxiliary positioning during the pre-test installation process and status monitoring during the test.

[0012] Furthermore, the split-type stress ring is provided with a through-type square groove for arranging the signal lines of the sensor assembly.

[0013] Furthermore, the sensor assembly includes a pressure sensor and a sensor mounting base, which are connected by bolts. The sensor mounting base is symmetrically provided with a "I"-shaped limiting structure on the outside, which cooperates with the square groove to restrict circumferential movement and prevent the torque during the bolt tightening process from causing the sensor assembly to rotate and damaging the signal line.

[0014] Furthermore, the loading box and the split stress ring are designed separately and are connected by bolts, which facilitates the installation of the sensor assembly and the loading rod.

[0015] Furthermore, the water-cooling device is equipped with a stress ring water-cooling pipe joint, which is connected to a chiller through a water-cooling pipe to provide cooling water. Each split stress ring is provided with two stress ring water-cooling pipe joints, wherein the water-cooling pipe joint located at the lower end is the water inlet and the water-cooling pipe joint located at the upper end is the water outlet, so as to achieve sufficient cooling of the split stress ring.

[0016] Furthermore, the irregularly shaped split linear bearing and the micro-motion pad are in an interference fit when they are in close contact, and the assembly formed by the irregularly shaped split linear bearing and the micro-motion pad is in a clearance fit with the support shell, ensuring that the adjusting bolt has sufficient adjustment stroke to eliminate the clearance.

[0017] Furthermore, there are four sets of adjusting bolts, which respectively restrict the displacement of the micro-movement pads on both sides in two directions in a plane perpendicular to the normal, thereby eliminating the assembly gap. At the same time, each adjusting bolt is equipped with a spring washer and a nut to prevent the adjusting bolts from loosening and forming new gaps during the test.

[0018] Furthermore, the irregularly shaped split linear bearing includes an outer bearing ring, a fixing frame, fixing screws, limiting pins, and ball rollers. The overall outer contour and the working surface contour are square. Each corner of the outer contour is chamfered and divided into two parts along the diagonal. Each part is connected by four limiting pins along the diagonal direction to prevent the adjusting bolt from tightening, thereby eliminating misalignment during the clearance process.

[0019] Furthermore, each inner surface of the bearing outer ring is provided with two cylindrical grooves for installing ball rollers; the radius of the ball rollers is smaller than the radius of the cylindrical grooves, and the diameter is larger than the maximum depth of the cylindrical grooves, ensuring that the ball rollers protrude from the surface of the bearing outer ring after installation, thereby supporting the micro-moving pads.

[0020] Furthermore, the ball roller is made of silicon nitride, which has high hardness and elastic modulus, good wear resistance, and a low coefficient of friction.

[0021] Furthermore, the fixing bracket is installed on both sides of the outer ring of the bearing to restrict the movement of the ball rollers in the groove. The fixing bracket and the outer ring of the bearing are connected by fixing screws to ensure sufficient connection rigidity.

[0022] Furthermore, the stress ring water-cooled pipe joint and the clamp water-cooled pipe joint are pneumatic quick-connect joints, which facilitate rapid installation and disassembly before and after the test.

[0023] Furthermore, the outer wall of the high-temperature loading device is provided with a support structure evenly distributed along the circumference to support the split stress ring, so that the loading link remains suspended and does not directly contact the high-temperature loading device, thus avoiding the introduction of additional resistance on the normal load transmission path.

[0024] Furthermore, the test pieces include fretting wear test pieces and fretting fatigue test pieces. The test pieces have a square cross-section and are connected to the test piece fixture by means of threads and pins.

[0025] Furthermore, the micro-motion pad has a convex shape and a square contact portion with the irregularly shaped split linear bearing, which has self-positioning and anti-rotation functions.

[0026] This invention also provides a micro-motion testing method suitable for high-temperature environments, comprising the following steps:

[0027] Step 1: Assemble the micro-motion pad and the micro-motion pad limiting device into one piece, tighten the adjusting bolt, and eliminate the fitting gap of the micro-motion pad;

[0028] Step 2: Install the tangential load loading device, the micro-motion pad limiting device, and the test piece on the fatigue testing machine;

[0029] Step 3: Close the left and right furnace bodies of the high-temperature loading device, place the loading connecting rod through the normal loading hole, and assemble the normal load loading device;

[0030] Step 4: Connect the water cooling pipes, turn on the chiller, set the heating temperature, and start heating. Once the temperature reaches the set value, keep it warm for 30 minutes to ensure the temperature is completely stable.

[0031] Step 5: Tighten the loading bolts, observe the reading of the pressure sensor to ensure that the normal load meets the test requirements, set the tangential load parameters through the fatigue testing machine control software, and then start the test;

[0032] Step 6: Monitor the pressure sensor reading during the test. If the reading changes by more than 2%, pause the test and readjust the normal load; otherwise, no adjustment is needed until the test ends.

[0033] The advantages of this invention compared to the prior art are as follows:

[0034] (1) The normal load loading device proposed in this invention adopts a large number of split designs, such as split stress ring, split loading box, segmented connecting bolts and loading rods, which facilitates the installation and disassembly of high temperature test, and facilitates the replacement of high temperature vulnerable parts, and the test cost is low.

[0035] (2) The present invention arranges a pressure sensor between the loading bolt and the loading rod to directly measure the normal load. Compared with the method of indirect measurement using strain gauges, the system error is smaller and the measurement accuracy is higher.

[0036] (3) The micro-motion pad limiting device proposed in this invention uses adjusting bolts to eliminate assembly gaps, resulting in higher loading accuracy of tangential loads. At the same time, it uses irregularly shaped split linear bearings to reduce friction and reduce the transmission loss of normal loads. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a micro-motion testing device suitable for high-temperature environments according to the present invention, wherein 1-normal load loading device, 2-micro-motion pad limiting device, 3-tangential load loading device, 4-high temperature loading device, 5-test piece, and 6-micro-motion pad;

[0038] Figure 2 This is a schematic diagram of a normal load loading device applying a normal load to a test piece, where 11-half stress ring, 12-loading bolt, 13-anti-loosening nut, 14-loading box, 17-loading connecting rod, 181-water cooling device, and 182-stress ring water cooling pipe joint.

[0039] Figure 3 A cross-sectional view of a normal load loading device applying a normal load to a test specimen, wherein 15-sensor assembly, 16-linear bearing;

[0040] Figure 4 This is a schematic diagram of the assembly of the split stress ring and the sensor assembly, where 111-square groove, 151-pressure sensor, and 152-sensor mounting base;

[0041] Figure 5 This is a schematic diagram of the assembly of the micro-motion pad limiting device with the test piece and the micro-motion pad, where 21-support shell, 22-bearing cover, and 23-adjusting bolt;

[0042] Figure 6 This is a cross-sectional view of the fretting pad limiting device, the test piece, and the fretting pad after assembly, including 24-irregular split linear bearing;

[0043] Figure 7 This is a schematic diagram of a non-circular split linear bearing, where 241 is the outer ring of the bearing, 242 is the fixing bracket, and 243 is the fixing screw.

[0044] Figure 8 Exploded view of the components of a split linear bearing, where 244 is the locating pin and 245 is the ball roller;

[0045] Figure 9a , Figure 9b , Figure 9c This is a schematic diagram showing the connection between the tangential load loading device and the test specimen; where, Figure 9a This is a configuration diagram for a threaded connection type fretting wear test specimen. Figure 9b This is a configuration diagram for a threaded connection type fretting fatigue test specimen. Figure 9c This is a configuration diagram for a pin-connected fretting fatigue test specimen, where 31-test specimen clamp, 32-clamping section, 33-clamp water-cooled pipe joint, 34-limiting device tightening bolt, 35-test specimen tightening bolt, and 36-pin;

[0046] Figure 10 This is a schematic diagram of a high-temperature loading device, where 41-left furnace body, 42-right furnace body, 43-tangential loading hole, 44-normal loading hole, 45-observation window, and 46-stress ring support structure.

[0047] Figure 11a , Figure 11b , Figure 11c This is a schematic diagram of the test specimen; where, Figure 11a This is a threaded connection type fretting wear test specimen. Figure 11b This is a threaded connection type fretting fatigue test specimen. Figure 11c This is a pin-connected fretting fatigue test specimen;

[0048] Figure 12 This is a schematic diagram of the micro-motion pad. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0050] The technical solution of a micro-motion testing device and its testing method suitable for high-temperature environments according to the present invention will be described in detail below with reference to the accompanying drawings.

[0051] like Figure 1 As shown, a micro-motion testing device suitable for high-temperature environments according to the present invention includes a normal load loading device 1, a micro-motion pad limiting device 2, a tangential load loading device 3, a high-temperature loading device 4, and corresponding test pieces 5 and micro-motion pads 6.

[0052] like Figure 2 and Figure 3As shown, the normal load loading device 1 includes a split stress ring 11, a loading bolt 12, a lock nut 13, a loading box 14, a sensor assembly 15, a linear bearing 16, a loading connecting rod 17, a water cooling device 181, and a stress ring water cooling pipe joint 182. The split stress ring 11 is connected by bolts to form a complete stress ring, realizing synchronous and stable loading of the normal load. At the same time, the split design facilitates test installation. The normal clamping force generated by tightening the loading bolt 12 passes through the loading box 14 and is transmitted to the test piece 5 in sequence through the sensor assembly 15, the loading connecting rod 17, and the micro-motion pad 6. The loading connecting rod 17 is mounted on the split stress ring 11 through the linear bearing 16 to reduce the loss of normal load transmission and improve coaxiality. The upper and lower end faces of the split stress ring 11 near the linear bearing 16 are provided with water cooling devices 181 to cool the linear bearing 16 and prevent heat from being transferred to the sensor assembly 15.

[0053] Further, if Figure 4 As shown, a through square groove 111 is provided on the protrusion of the split stress ring 11 for arranging the signal lines of the sensor assembly 15.

[0054] Further, if Figure 4 As shown, the sensor assembly 15 includes a pressure sensor 151 and a sensor mounting base 152, which are connected by bolts. The sensor mounting base 152 is symmetrically provided with a "I"-shaped limiting structure on the outside, which cooperates with the square groove 111 on the split stress ring 11 to limit circumferential movement and prevent the torque during the bolt tightening process from causing the sensor assembly 15 to rotate and damage the signal line.

[0055] Furthermore, the loading box 14 and the split stress ring 11 are designed separately and are connected by bolts, which facilitates the installation of the sensor assembly 15 and the loading rod 17.

[0056] Furthermore, the water cooling device 181 is equipped with a stress ring water cooling pipe joint 182, which is connected to a chiller through a water cooling pipe to provide cooling water. Each split stress ring 11 is provided with two stress ring water cooling pipe joints 182, wherein the water cooling pipe joint located at the lower end is the water inlet and the water cooling pipe joint located at the upper end is the water outlet, so as to achieve sufficient cooling of the split stress ring 11.

[0057] like Figure 5 and Figure 6As shown, the micro-motion pad limiting device 2 includes a support housing 21, a bearing cover 22, an adjusting bolt 23, and a non-circular split linear bearing 24. By adjusting the bolt 23 to tighten the micro-motion pad 6, the fit gap between the micro-motion pad 6 and the support housing 21 is eliminated, ensuring precise control during the application of tangential load. The non-circular split linear bearing 24 is used to reduce the coefficient of friction between the micro-motion pad 6 and the support housing 21, thereby reducing the loss caused by the preload introduced by the adjusting bolt 23 during the gap elimination process on the transmission of normal load.

[0058] Furthermore, the irregularly shaped split linear bearing 24 in the tightly fitted state has an interference fit with the micro-motion pad 6, and the irregularly shaped split linear bearing 24 after fitting with the micro-motion pad 6 has a clearance fit with the support housing 21, ensuring that the adjusting bolt 23 has sufficient adjustment stroke to eliminate the clearance.

[0059] Furthermore, there are four sets of adjusting bolts 23, which respectively restrict the displacement of the micro-movement pads 6 on both sides in two directions within a plane perpendicular to the normal, thereby eliminating the assembly gap. At the same time, each adjusting bolt 23 is equipped with a spring washer and a nut to prevent the adjusting bolts from loosening and forming new gaps during the test.

[0060] like Figure 7 and Figure 8 As shown, the irregularly shaped split linear bearing 24 of the micro-motion pad limiting device 2 includes a bearing outer ring 241, a fixing frame 242, a fixing screw 243, a limiting pin 244, and a ball roller 245. The overall outer contour and the working surface contour are square. Each corner of the outer contour is chamfered and divided into two parts along the diagonal. Each part is connected by four limiting pins 244 along the diagonal direction to prevent misalignment during the tightening of the adjusting bolt 23 to eliminate the gap.

[0061] Furthermore, each inner surface of the bearing outer ring 241 is provided with two cylindrical grooves for mounting ball rollers 245. The radius of the ball rollers 245 is slightly smaller than the radius of the cylindrical grooves, but the diameter is slightly larger than the maximum depth of the cylindrical grooves, ensuring that the ball rollers 245 protrude from the surface of the bearing outer ring 241 after installation, thereby supporting the micro-moving pads 6.

[0062] Furthermore, the ball roller 245 is made of silicon nitride, which has high hardness and elastic modulus, good wear resistance and low coefficient of friction.

[0063] Furthermore, the fixing bracket 242 is installed on both sides of the bearing outer ring 241 to restrict the movement of the ball roller in the groove. The fixing bracket 242 and the bearing outer ring 241 are connected by fixing screws 243 to ensure sufficient connection rigidity.

[0064] like Figure 9a , Figure 9b , Figure 9c As shown, the tangential load loading device 3 is a water-cooled tensile clamp, which is divided into an upper clamp and a lower clamp, and is completely symmetrical. Each part includes a test piece clamp 31, a clamping section 32, a clamp water-cooled pipe joint 33, a limiting device tightening bolt 34, and a test piece tightening bolt 35. One end of the test piece clamp 31 is connected to the test piece 5 and the micro-movement pad limiting device 2, and the other end is connected to the clamping section 32. The other end of the clamping section 32 is connected to the fatigue testing machine. The fatigue testing machine applies a periodic tangential load, which is transferred to the test piece 5 through the clamping section 32 and the test piece clamp 31 in sequence.

[0065] Furthermore, the tangential load loading device 3 has multiple configurations to adapt to different test requirements. For fretting wear tests, such as... Figure 9a As shown, the test piece 5 is connected to the test piece clamp 31 of the lower fixture via a thread, and a test piece tightening bolt 35 is also provided. For fretting fatigue testing, two configuration options are available: one is a threaded connection configuration: both ends of the test piece 5 are threaded, and are respectively connected to the test piece clamp 31 of the upper and lower fixtures via threads, as shown. Figure 9b As shown; the second configuration is a pin connection: the test piece 5 is a flat plate with pin holes at both ends, which are connected to the test piece clamps 31 of the upper and lower clamps via pins 36, as shown. Figure 9c As shown.

[0066] Furthermore, the stress ring water-cooled pipe joint 182 and the clamp water-cooled pipe joint 33 are pneumatic quick-connect joints, which facilitate quick installation and disassembly before and after the test.

[0067] like Figure 10 As shown, the high-temperature loading device 4 is a split-type high-temperature furnace, which is placed inside the split-type stress ring 11. It includes a left furnace body 41 and a right furnace body 42 connected by hinges. It is provided with mutually perpendicular tangential loading holes 43 and normal loading holes 44, which pass through the tangential load loading device 3 and the normal load loading device 1, respectively. A rectangular observation window 45 is provided in the middle of the opening and closing surface of the left furnace body 41 and the right furnace body 42 for auxiliary positioning during the pre-test installation process and status monitoring during the test.

[0068] Furthermore, the outer wall of the high-temperature loading device 4 is provided with a stress ring support structure 46 evenly distributed along the circumference, which is used to support the split stress ring 11, so that the loading connecting rod 17 remains suspended and does not directly contact the high-temperature loading device 4, thus avoiding the introduction of additional resistance on the normal load transmission path.

[0069] like Figure 11a , Figure 11b , Figure 11cAs shown, the contact area between test piece 5 and micro-motion pad 6 is the assessment section, with a square cross-section, which can be connected to test piece fixture 31 via threads or pins. Figure 11a As shown, for the fretting wear test, test piece 5 is connected to the lower fixture with a single-sided thread, and is equipped with test piece tightening bolt 35 to minimize the influence of assembly clearance on the fretting stroke; as Figure 11b As shown, for the fretting fatigue test, test piece 5 is connected to the upper and lower clamps respectively using double-sided threads; as Figure 11c As shown, for fretting fatigue testing, a flat test piece 5 can also be used, which is connected to the upper and lower clamps by double-sided pins respectively.

[0070] like Figure 12 As shown, the micro-motion pad 6 has a convex shape and a square contact portion with the irregularly shaped split linear bearing 24, which has self-positioning and anti-rotation functions.

[0071] The present invention also provides a test method for a micro-motion test device suitable for high-temperature environments, comprising the following steps:

[0072] Step 1: Assemble the micro-motion pad 6 and the micro-motion pad limiting device 2 into one unit, tighten the adjusting bolt 23, and eliminate the fitting gap of the micro-motion pad 6;

[0073] Step 2: Install the tangential load loading device 3, the micro-movement pad limiting device 2, and the test piece 5 on the fatigue testing machine;

[0074] Step 3: Close the left furnace body 41 and right furnace body 42 of the high temperature loading device 4, place the loading connecting rod 17 through the normal loading hole 44, and assemble the normal load loading device 1.

[0075] Step 4: Connect the water cooling pipes, turn on the chiller, set the heating temperature, and start heating. Once the temperature reaches the set value, keep it warm for 30 minutes to ensure the temperature stabilizes completely.

[0076] Step 5: Tighten the loading bolt 12, observe the reading of the pressure sensor 151, ensure that the normal load meets the test requirements, set the tangential load parameters through the fatigue testing machine control software, and then start the test;

[0077] Step 6: Monitor the reading of pressure sensor 151 during the test. If the reading changes by more than 2%, pause the test and readjust the normal load; otherwise, no adjustment is needed until the test ends.

[0078] This invention can improve the feasibility and ease of installation of high-temperature fretting tests, and reduce load transfer loss and test system errors, while improving loading and measurement accuracy. It can be used to accurately evaluate the fretting damage behavior between high-temperature contact components of aero-engines.

[0079] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A micro-motion testing device suitable for high-temperature environments, characterized in that, The system includes a normal load loading device, a micro-motion pad limiting device, a tangential load loading device, a high-temperature loading device, and corresponding test pieces and micro-motion pads. The normal load loading device comprises a split stress ring, loading bolts, anti-loosening nuts, a loading box, a sensor assembly, a linear bearing, a loading connecting rod, a water cooling device, and a stress ring water-cooling pipe joint. The split stress rings are connected by bolts to form a complete stress ring, achieving synchronous and stable normal load loading. The split design also facilitates test installation. Tightening the loading bolts generates a normal compressive force, which is sequentially applied through the sensor assembly. The loading linkage and fretting pad transfer the load to the test piece. The loading linkage is mounted on the split-type stress ring via a linear bearing to reduce the loss of normal load transfer and improve coaxiality. The upper and lower end faces of the split-type stress ring near the linear bearing are equipped with water-cooling devices to cool the linear bearing and prevent heat transfer to the sensor assembly. The fretting pad limiting device includes a support housing, bearing cover, adjusting bolts, and a non-standard split-type linear bearing. By tightening the fretting pad with the adjusting bolts, the clearance between the fretting pad and the support housing is eliminated, ensuring precise and controllable application of the tangential load. The friction coefficient between the micro-motion pad and the supporting shell is reduced by using a non-circular split linear bearing, thereby reducing the loss caused by the preload introduced by the adjusting bolt during the clearance elimination process on the normal load transmission. The tangential load loading device is a water-cooled tensile fixture, consisting of an upper fixture and a lower fixture, which are completely symmetrical. Both the upper and lower fixtures include a test piece fixture, a clamping section, a water-cooled pipe joint for the fixture, a limiting device tightening bolt, and a test piece tightening bolt. One end of the test piece fixture is connected to the test piece and the micro-motion pad limiting device, while the other end is connected to the clamping section. One end is connected to a fatigue testing machine; the fatigue testing machine applies a periodic tangential load, which is transferred to the test piece through the clamping section and the test piece fixture in sequence; the high temperature loading device is a split high temperature furnace, which is placed inside the split stress ring and includes a left furnace body and a right furnace body connected by a hinge. The high temperature furnace is provided with mutually perpendicular tangential loading holes and normal loading holes, which pass through the tangential load loading device and the normal load loading device respectively. A rectangular observation window is provided in the middle of the opening and closing surfaces of the left furnace body and the right furnace body for auxiliary positioning during the pre-test installation process and status monitoring during the test. The split-type stress ring is provided with a through-type square groove for arranging the signal lines of the sensor assembly. The sensor assembly includes a pressure sensor and a sensor mounting base, which are connected by bolts. The sensor mounting base is symmetrically provided with a straight-line limiting structure on the outside, which cooperates with a square groove to restrict circumferential movement and prevent the torque during the bolt tightening process from causing the sensor assembly to rotate and damaging the signal line. The irregularly shaped split linear bearing and the micro-motion pad are in an interference fit when they are in close contact, and the assembly formed by the irregularly shaped split linear bearing and the micro-motion pad is in a clearance fit with the support shell, so as to ensure that the adjusting bolt has sufficient adjustment stroke to eliminate the clearance. There are four sets of adjusting bolts, which respectively limit the displacement of the micro-moving pads on both sides in two directions in a plane perpendicular to the normal, thereby eliminating the assembly gap. At the same time, each adjusting bolt is equipped with a spring washer and a nut to prevent the adjusting bolts from loosening and forming new gaps during the test. The irregular split linear bearing includes an outer bearing ring, a fixing frame, fixing screws, limiting pins, and ball rollers. The overall outer contour and working surface contour are square. Each corner of the outer contour is chamfered and divided into two parts along the diagonal. Each part is connected by four limiting pins along the diagonal direction to prevent the adjusting bolt from tightening, thereby eliminating misalignment during the clearance process. Two cylindrical grooves are provided on each inner surface of the outer ring of the bearing for installing ball rollers; the radius of the ball rollers is smaller than the radius of the cylindrical grooves, and the diameter is larger than the maximum depth of the cylindrical grooves, so as to ensure that the ball rollers protrude from the surface of the outer ring of the bearing after installation, thereby supporting the micro-moving pads. The fixing bracket is installed on both sides of the outer ring of the bearing to restrict the movement of the ball rollers in the groove. The fixing bracket and the outer ring of the bearing are connected by fixing screws to ensure sufficient connection rigidity. The test pieces include fretting wear test pieces and fretting fatigue test pieces. The test pieces have a square cross section and are connected to the test piece fixture by means of threads and pins.

2. A micro-motion testing method for high-temperature environments based on the micro-motion testing device for high-temperature environments as described in claim 1, characterized in that, Includes the following steps: Step 1: Assemble the micro-motion pad and the micro-motion pad limiting device into one piece, tighten the adjusting bolt, and eliminate the fitting gap of the micro-motion pad; Step 2: Install the tangential load loading device, the micro-motion pad limiting device, and the test piece on the fatigue testing machine; Step 3: Close the left and right furnace bodies of the high-temperature loading device, place the loading connecting rod through the normal loading hole, and assemble the normal load loading device; Step 4: Connect the water cooling pipes, turn on the chiller, set the heating temperature, and start heating. Once the temperature reaches the set value, keep it warm for 30 minutes to ensure the temperature is completely stable. Step 5: Tighten the loading bolts, observe the reading of the pressure sensor to ensure that the normal load meets the test requirements, set the tangential load parameters through the fatigue testing machine control software, and then start the test; Step 6: Monitor the pressure sensor reading during the test. If the reading changes by more than 2%, pause the test and readjust the normal load; otherwise, no adjustment is needed until the test ends.

Images