Variable-temperature ultra-high-cycle biaxial fatigue test device with variable stress ratio

Abstract

The invention discloses a variable-stress-ratio variable-temperature ultra-high-cycle biaxial fatigue test device which is characterized in that the device comprises a stretcher, a vibration component and a heating furnace, the vibration component is arranged on the stretcher, the stretcher comprises a stretcher frame and a stretcher cross rod arranged in the stretcher frame, and the stretcher cross rod is arranged in the stretcher frame. The vibration component comprises a piezoelectric ultrasonic transducer, an amplitude transformer, a first amplification rod and a second amplification rod, the first amplification rod is arranged on the lower side of a cross rod of the stretcher, the second amplification rod is arranged at the bottom of the stretcher, a cross-shaped sample is arranged between the first amplification rod and the second amplification rod, and the piezoelectric ultrasonic transducer is arranged on the cross-shaped sample. The two ends of the cross-shaped sample are connected with the first amplification rod and the second amplification rod respectively, and the piezoelectric ultrasonic transducer and the amplitude transformer are arranged on the first amplification rod. The variable-temperature ultra-high-cycle biaxial fatigue test is realized by only changing the sample size and adding the heating furnace, so that the equipment manufacturing cost and the test operation complexity are greatly reduced, and the equipment maintenance and test cost is reduced.

Description

Technical Field

[0001] The invention relates to a multi-axial ultra-high cycle fatigue performance test, in particular to a variable-stress ratio variable-temperature ultra-high cycle biaxial fatigue test device. Background Art

[0002] In real engineering applications, structures are often in complex multiaxial stress fields, accompanied by dynamic changes in ambient temperature. In order to obtain the mechanical response behavior of materials under variable temperature and complex stress states, it is particularly important to conduct ultra-high cycle biaxial fatigue tests under different stress ratios and variable temperature conditions. At present, commercial biaxial fatigue test devices usually directly apply tensile, torsion and bending loads on the specimen to simulate the multiaxial stress field of the component. In order to accurately load and measure the stress and deformation of the specimen during the test, the test equipment must be equipped with special loading axes, high-precision sensors, advanced control systems, etc. The test equipment is complex in design and requires precise operation, which requires high technical requirements for operators. At the same time, the complex design and operation requirements lead to high equipment manufacturing and maintenance costs. These limiting factors undoubtedly pose a challenge to researchers in fatigue research under a wide range of materials and complex loading conditions. Summary of the invention

[0003] The purpose of the present invention is to provide a variable-temperature ultra-high-cycle biaxial fatigue testing device with a variable stress ratio, so as to solve the problems in the prior art of complex testing devices, high operating requirements and poor maintenance economy.

[0004] The present invention is implemented by adopting the following technical scheme: a variable-stress-ratio variable-temperature ultra-high-cycle biaxial fatigue testing device, characterized in that it includes a stretching machine, a vibrating component and a heating furnace, the vibrating component is arranged on the stretching machine, the stretching machine includes a stretching machine frame and a stretching machine cross bar arranged in the stretching machine frame, the vibrating component includes a piezoelectric ultrasonic transducer, a horn, an amplifier rod 1, and an amplifier rod 2, the amplifier rod 1 is arranged on the lower side of the stretching machine cross bar, the amplifier rod 2 is arranged at the bottom of the stretching machine, a cross-shaped specimen is arranged between the amplifier rod 1 and the amplifier rod 2, the two ends of the cross-shaped specimen are respectively connected to the amplifier rod 1 and the amplifier rod 2, the piezoelectric ultrasonic transducer and the horn are arranged on the amplifier rod 1, the heating furnace is arranged on the cross-shaped specimen, and the middle part of the cross-shaped specimen is located in the heating furnace.

[0005] Furthermore, the stretching machine is also provided with a stretching machine fixing device, and there are two stretching machine fixing devices, which are respectively arranged on the stretching machine cross bar and the bottom of the stretching machine, and are respectively fixedly connected to the amplitude transformer and the second amplifier rod.

[0006] Furthermore, a cooling device is provided on the outside of the heating furnace.

[0007] Furthermore, the stretching machine cross bar is slidably connected to the stretching machine frame and moves up and down along the stretching machine frame.

[0008] Furthermore, the heating furnace includes a heating furnace body and a temperature control device, and the heating furnace body and the temperature control device are connected via a wire.

[0009] Furthermore, the heating furnace body is a hollow sphere, which is composed of two hemispheres. Through holes corresponding to the shape of the cross-shaped sample are arranged around the hollow sphere, so that the four ends of the cross-shaped sample extend out of the heating furnace body.

[0010] Furthermore, the stretching machine stretches the cross-shaped specimen longitudinally by moving the stretching machine crossbar, thereby applying average stress, and the size of the applied average stress is controlled by a computer, thereby controllably changing the longitudinal stress ratio of the cross-shaped specimen.

[0011] The variable temperature ultra-high cycle biaxial fatigue testing device with a variable stress ratio described in the present invention has the following beneficial effects: By changing the size of the cross-shaped specimen, a stable in-phase or out-of-phase biaxial stress is generated in the longitudinal and transverse directions of the specimen under the loading of a single excitation displacement; the tensile machine provides an external controllable load for the cross-shaped specimen, thereby controllably changing the longitudinal stress ratio of the specimen; a separately designed heating furnace can accurately adjust the temperature of the cross-shaped specimen, and finally realize ultra-high cycle biaxial fatigue tests at different stress ratios and temperatures. The present invention realizes variable temperature ultra-high cycle biaxial fatigue tests by only changing the specimen size and adding a heating furnace, greatly reducing the equipment manufacturing cost and the operational complexity of the test, and reducing equipment maintenance and test costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0013] Figure 1 A schematic diagram of a variable stress ratio variable temperature ultra-high cycle biaxial fatigue test device; Figure 2 It is a structural schematic diagram of a vibration component; Figure 3 It is a structural schematic diagram of a heating furnace; Figure 4 It is a structural schematic diagram of a stretching machine; In the figure, 1-stretching machine; 2-piezoelectric ultrasonic transducer; 3-amplifier; 4-amplifier rod 1; 5-cross-shaped sample; 6-heating furnace; 7-stretching machine fixture 2; 8-stretching machine cross bar; 9-stretching machine fixture 1; 10-cooling device; 11-amplifier rod 2. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0015] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] like Figure 1 As shown, a variable-stress ratio variable-temperature ultra-high-cycle biaxial fatigue test device comprises a piezoelectric ultrasonic transducer 2, an amp 3, an amplifier rod 1 4, a cross-shaped specimen 5, an amplifier rod 2 11, a heating furnace 6, a cooling device 10, a stretching machine 1, and a computer. The piezoelectric ultrasonic transducer 2 and the amp 3 are fixed by a stretching machine fixing device 1 9. The piezoelectric ultrasonic transducer 2, the amp 3 and the amplifier rod 1 4 are connected by bolts and controlled by a computer system to produce longitudinal vibration in coordination, and the longitudinal excitation displacement amplitude is adjusted by the computer control system. The lower end of the amplifier rod 1 4 is connected to the cross-shaped specimen 5. Under the action of the longitudinal excitation displacement, the cross-shaped specimen 5 produces a standard symmetrical tension-compression resonance vibration mode in its transverse and longitudinal directions. The heating furnace 6 is a new type of heating furnace 6 specially designed according to the cross-shaped specimen 5. During the heating process, the cross-shaped specimen 5 is located in the middle of the heating furnace 6, and the middle of the cross-shaped specimen 5 is heated uniformly and temperature-controlled. The purpose of the cooling device 10 is to eliminate the temperature influence of the heating device on the amplifier rod 1 4 and the amplifier rod 2 11. The cross-shaped specimen 5 is connected to the amplifier rod 11 and fixed by the stretching machine fixture 7. Due to the fixing effect of the stretching machine fixture 1 9 and the stretching machine fixture 7 on the piezoelectric ultrasonic transducer 2, the amplitude transformer 3, the amplifier rod 1 4, the cross-shaped specimen 5 and the amplifier rod 11, during operation, the stretching machine cross bar 8 moves upward according to the load input by the computer, and then the cross-shaped specimen 5 is stretched in the longitudinal direction and an average stress is applied to it. The average stress is superimposed on the cyclic symmetrical stress generated by the longitudinal tension-compression vibration mode, that is, the longitudinal stress ratio of the specimen is controlled by the controllable change of the average stress.

[0017] like Figure 2 As shown, the piezoelectric ultrasonic transducer 2 continues to adjust and transmit the longitudinal excitation displacement through the amplitude transformer 3 and the amplifier rod 1 4. The bottom of the amplifier rod 1 4 drives the cross-shaped sample 5 to vibrate, and the amplifier rod 2 11 is responsible for the fixed connection between the cross-shaped sample 5 and the stretching machine; the computer controls the longitudinal amplitude output by the piezoelectric ultrasonic transducer 2.

[0018] like Figure 3 As shown, the heating part of the heating furnace 6 is composed of an upper and lower part, which respectively cover the cross-shaped sample 5 when in use, so as to achieve uniform heating of the middle part of the cross-shaped sample 5.

[0019] like Figure 4 As shown, the stretching machine 1 stretches the sample by moving the stretching machine crossbar 8, and the computer controls the magnitude of the applied average stress to change the longitudinal stress ratio of the sample. In this way, only the size of the sample is changed, and the biaxial loading method can be achieved through the resonance of the sample, which greatly saves the test cost and the difficulty of operating the equipment.

[0020] The present invention provides a variable temperature ultra-high cycle biaxial fatigue testing device with controllable stress ratio, which realizes controllable stress ratio, in-phase and out-of-phase biaxial stress loading at different temperatures, so as to accurately simulate the mechanical response of components under multi-axial stress fields. Based on the ultrasonic vibration fatigue testing method, the size of the cross-shaped specimen is designed to meet the requirement that the cross-shaped specimen generates high-frequency (20 KHz) and standard symmetrical tension-compression resonance vibration modes in both the transverse and longitudinal directions of the specimen under the high-frequency excitation of the test device. By changing the length dimension of the cross-shaped specimen in the transverse direction, the in-phase (longitudinal-transverse directions are both tensile or compressed) or out-of-phase (longitudinal tension, transverse compression) load loading of the specimen in the transverse and longitudinal directions at the same time is realized. In addition to high-frequency vibration, the cross-shaped specimen also bears the stable tension of the stretching machine in the longitudinal direction to generate average stress, and the average stress is superimposed on the cyclic symmetrical stress generated by the longitudinal tension-compression vibration mode. The longitudinal stress ratio is controlled by the controllable change of the tension of the stretching machine, that is, the change of the average stress. In addition, the vibration of the cross-shaped specimen is completed in a heating furnace with variable and controllable temperature, thereby realizing the functions of controllable stress ratio, biaxial stress loading on the same plane at different temperatures and fatigue performance testing. Compared with other biaxial or multiaxial devices, the present invention can achieve corresponding functions by only changing the sample size and adding a hot furnace device, thereby simplifying the test equipment, reducing the operating difficulty, and reducing the test cost.

[0021] The above embodiments describe the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the changes and modifications made by those skilled in the art shall be within the scope of protection of the appended claims of the present invention without departing from the spirit and scope of the present invention.

Claims

1. A variable temperature ultra-high cycle biaxial fatigue testing device with variable stress ratio, characterized in that: The invention comprises a stretching machine (1), a vibration component and a heating furnace (6), wherein the vibration component is arranged on the stretching machine (1), the stretching machine (1) comprises a stretching machine frame and a stretching machine cross bar (8) arranged in the stretching machine frame, the vibration component comprises a piezoelectric ultrasonic transducer (2), a horn (3), a first amplifier rod (4), and a second amplifier rod (11), the first amplifier rod (4) being arranged on the lower side of the stretching machine cross bar (8), the second amplifier rod (11) being arranged at the bottom of the stretching machine (1), a cross-shaped specimen (5) being arranged between the first amplifier rod (4) and the second amplifier rod (11), the two ends of the cross-shaped specimen (5) being respectively connected to the first amplifier rod (4) and the second amplifier rod (11), the piezoelectric ultrasonic transducer (2) and the horn (3) being arranged on the first amplifier rod (4), and the heating furnace (6) being arranged on the cross-shaped specimen (5), and the middle part of the cross-shaped specimen (5) being located in the heating furnace (6).

2. The variable stress ratio variable temperature ultra-high cycle biaxial fatigue testing device according to claim 1, characterized in that: The stretching machine (1) is also provided with a stretching machine fixing device. There are two stretching machine fixing devices, which are respectively arranged on the stretching machine cross bar (8) and the bottom of the stretching machine (1), and are respectively fixedly connected to the amplitude transformer (3) and the second amplifier rod (11).

3. The variable stress ratio variable temperature ultra-high cycle biaxial fatigue testing device according to claim 1, characterized in that: A cooling device (10) is also provided on the outside of the heating furnace (6).

4. The variable temperature ultra-high cycle biaxial fatigue testing device with variable stress ratio according to claim 1, characterized in that: The stretching machine cross bar (8) is slidably connected to the stretching machine frame and moves up and down along the stretching machine frame.

5. The variable stress ratio variable temperature ultra-high cycle biaxial fatigue testing device according to claim 1, characterized in that: The heating furnace (6) comprises a heating furnace body and a temperature control device, and the heating furnace body and the temperature control device are connected via a wire.

6. The variable temperature ultra-high cycle biaxial fatigue testing device with variable stress ratio according to claim 5, characterized in that: The heating furnace body is a hollow sphere, which is composed of two hemispheres. Through holes corresponding to the shape of the cross-shaped sample (5) are arranged around the hollow sphere, so that the four ends of the cross-shaped sample (5) extend out of the heating furnace body.

7. The variable stress ratio variable temperature ultra-high cycle biaxial fatigue testing device according to claim 1, characterized in that: The stretching machine (1) stretches the cross-shaped specimen (5) longitudinally by moving the stretching machine crossbar (8), thereby applying an average stress, and the magnitude of the applied average stress is controlled by a computer, thereby controllably changing the longitudinal stress ratio of the cross-shaped specimen (5).

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