Temperature control method for high-temperature ultrasonic vibration fatigue test

Abstract

The invention discloses a temperature control method for a high-temperature ultrasonic vibration fatigue test. The temperature control method comprises the following steps: A, obtaining a spontaneous heating stable temperature of a test piece under a target vibration load; b, the initial stable heating power and the initial stable heating duty ratio which enable the test piece to be maintained at the stable target heating temperature are obtained, and the stable target heating temperature is obtained by subtracting the spontaneous heating stable temperature from the stable target temperature; c, executing a temperature initial stabilization stage, applying a target vibration load to the test piece, and heating the test piece by using the initial stable heating power and the initial stable heating duty ratio so as to maintain the temperature of the test piece at a stable target temperature; and D, executing a temperature closed-loop stabilization stage, obtaining feedback stable heating power and a feedback stable heating duty ratio according to the temperature of the test piece, and heating the test piece by using the feedback stable heating power and the feedback stable heating duty ratio, so that the temperature of the test piece is maintained at a stable target temperature.

Description

Technical Field

[0001] The invention relates to a temperature control technology, and in particular to a temperature control method for a high-temperature ultrasonic vibration fatigue test. Background Art

[0002] High-temperature equipment such as aircraft engines and gas turbines are important high-temperature equipment for the core competitiveness of the manufacturing industry in the fields of aviation, energy, etc. Their high-temperature service environment is becoming increasingly harsh, bringing new challenges to their long-life design, manufacturing, and full-life safety assurance of operation and maintenance management. At present, the total life of an aircraft exceeds 30 years, and the in-service life of an aircraft engine reaches 50,000 hours. The vibration frequency of the whole machine and its components is high, and they are subjected to high-frequency loads of more than 1,000 Hz, and the continuous working time is long. It is required that the components can withstand more than 10 9 More than times of stress cycles without damage. Obviously, only carrying out traditional low-cycle and high-cycle fatigue is incomplete and uneconomical. Therefore, the study of ultra-high cycle fatigue is one of the hot spots in the fatigue research field in recent years. The study of ultra-high cycle fatigue not only involves the basic problems of failure characteristics and failure mechanism of high-cycle fatigue, but also faces technical difficulties in test methods and test equipment, especially the ultra-high cycle fatigue test of the above-mentioned high-temperature equipment in high-temperature service environment.

[0003] At present, ultra-high cycle fatigue tests are mainly based on two methods: ultrasonic resonance / resonance (such as 20KHz) and conventional vibration table resonance (100-2000Hz). 9For the cyclic test, ultrasonic resonance (such as 20KHz) only takes 13.9 hours, while conventional vibration table resonance (100-2000Hz) takes at least 139 hours. Therefore, conventional vibration table resonance (100-2000Hz) is usually only used to verify whether ultrasonic resonance (such as 20KHz) has frequency-related effects. High-temperature service environments are usually achieved by induction heating, resistance furnace heating, radiation furnace heating or other high-temperature boxes. The test piece has self-heating under high-frequency vibration. For example, under room temperature conditions, IN718 / GH4169 nickel-based high-temperature alloy materials self-heat at a resonance frequency of 20KHz for about 20 minutes and stabilize to 220 degrees Celsius. Existing temperature control is mainly based on temperature closed-loop control or intermittent loading. The temperature closed-loop control collects the real-time temperature of the test piece through a temperature sensor. When it exceeds a certain threshold above the operating temperature, heating and resonance are stopped, and heating and resonance are resumed after cooling. Intermittent loading uses resonance for 150 milliseconds (ms) and then stops resonance for 600ms (still maintaining the original heating power, some high damping materials require 100ms-3000ms intermittent parameters) to ensure the continuous stability of the set working temperature. With temperature closed-loop control, the temperature uniformity of the test piece is poor, the temperature range fluctuates greatly, and it is necessary to frequently stop heating and resonance, and then reheat and resonate, resulting in a long test time. With intermittent loading, the test cycle is long, resulting in a long test time. If the intermittent loading scheme parameters are used for 10 9 A cyclic test requires at least 69.4 hours. Summary of the invention

[0004] The object of the present invention is to provide a temperature control method for a high-temperature ultrasonic vibration fatigue test, which is used to improve the situation where the temperature uniformity of the temperature closed-loop control is poor and the test time is long.

[0005] According to an embodiment of the present invention, the temperature control method includes the steps of A. obtaining a self-heating stable temperature of a test piece under a target vibration load; B. obtaining an initial stable heating power and an initial stable heating duty cycle for maintaining the test piece at a stable target heating temperature, wherein the stable target heating temperature is the stable target temperature minus the self-heating stable temperature; C. executing an initial temperature stabilization phase, applying the target vibration load to the test piece, and heating the test piece using the initial stable heating power and the initial stable heating duty cycle so that the temperature of the test piece is maintained at the stable target temperature; and D. executing a temperature closed-loop stabilization phase, obtaining a feedback stable heating power and a feedback stable heating duty cycle according to the temperature of the test piece, and heating the test piece using the feedback stable heating power and the feedback stable heating duty cycle so that the temperature of the test piece is maintained at the stable target temperature.

[0006] In one or more embodiments, the temperature control method further includes, before step C, step E: obtaining an initial heating power and an initial heating time for the test piece to reach the target heating temperature; and step F: executing an initial temperature rise phase, heating the test piece using the initial heating power and the initial heating time to heat the test piece so that the test piece is heated to the target heating temperature.

[0007] In one or more embodiments, the stable target temperature is the stable target median temperature±the target temperature control threshold; the heating target temperature is the stable target median temperature or the stable target median temperature minus the target temperature control threshold.

[0008] In one or more embodiments, the step A includes step A1. calibrating the self-heating stable temperature of the test piece at different vibration loads; and step A2. obtaining the self-heating stable temperature of the test piece at the target vibration load according to an interpolation method.

[0009] In one or more embodiments, the step B includes step B1. calibrating the initial stable heating power and the initial stable heating duty cycle of the test piece maintained at different stable temperatures; and step B2. obtaining the initial stable heating power and the initial stable heating duty cycle of the test piece maintained at the stable target heating temperature according to the interpolation method.

[0010] In one or more embodiments, step D includes making the post-stable heating duty cycle equal to the front-stable heating duty cycle, and making the post-stable heating power equal to the front-stable heating power. If the temperature change rate of the test piece is greater than zero, then the post-stable heating duty cycle that is less than the front-stable heating duty cycle is obtained. If the temperature change rate of the test piece is less than zero, then the post-stable heating duty cycle that is greater than the front-stable heating duty cycle is obtained. If the temperature change rate of the test piece is equal to zero, then the post-stable heating duty cycle that is equal to the front-stable heating duty cycle is obtained.

[0011] In one or more embodiments, step D also includes obtaining a post-stable heating power less than a front stable heating power if the temperature of the test piece is greater than the stable target temperature, obtaining a post-stable heating power greater than the front stable heating power if the temperature of the test piece is less than the stable target temperature, and obtaining a post-stable heating power equal to the front stable heating power if the temperature of the test piece is equal to the stable target temperature.

[0012] In one or more embodiments, the front stable heating power is the initial stable heating power, the front stable heating duty cycle is the initial stable heating duty cycle, the rear stable heating power is the feedback stable heating power, and the rear stable heating duty cycle is the feedback stable heating duty cycle; or the step D is iteratively executed, the front stable heating power is the feedback stable heating power of the previous step D, the front stable heating duty cycle is the feedback stable heating duty cycle of the previous step D, the rear stable heating power is the feedback stable heating power of the next step D, and the rear stable heating duty cycle is the feedback stable heating duty cycle of the next step D.

[0013] The embodiments of the present invention have at least the following beneficial effects:

[0014] Step B takes into account the self-heating of the test piece under the target vibration load, removes the self-heating stable temperature under the target vibration load from the stable target temperature, and obtains the initial stable heating power and initial stable heating duty cycle for heating the test piece to maintain it at the stable target temperature in step C according to the stable target heating temperature formed by subtracting the self-heating stable temperature from the stable target temperature. This improves the temperature uniformity of the test piece in step C, reduces the temperature fluctuation range, avoids frequent starting and stopping of the heating and vibration equipment, thereby shortening the test time, improving the test accuracy, and reducing the test cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:

[0016] Figure 1 It is a schematic diagram of a high temperature ultrasonic vibration fatigue test device;

[0017] Figure 2 This is a picture of the temperature rise curve of self-heating;

[0018] Figure 3 This is a picture of the heating temperature rise curve;

[0019] Figure 4 This is the temperature control curve of high temperature ultrasonic fatigue vibration test;

[0020] Figure 5 This is a flow chart of the temperature control method for high temperature ultrasonic fatigue vibration test;

[0021] Reference numerals:

[0022] 1- Ultrasonic vibration component;

[0023] 11-Test framework;

[0024] 12-ultrasonic signal generator;

[0025] 13- piezoelectric ceramics;

[0026] 14-Magnifying rod;

[0027] 15- Computer;

[0028] 2- Heating component;

[0029] 21-heater;

[0030] 22- Power controller;

[0031] 3- Temperature measurement component;

[0032] 4-Displacement measurement component;

[0033] 41- Non-contact displacement measurement equipment;

[0034] 42-optical reflecting prism;

[0035] 5-Data acquisition component;

[0036] 6- Test piece. DETAILED DESCRIPTION

[0037] Reference will now be made in detail to embodiments of the present invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided to explain the present invention, not to limit the present invention. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made in the present invention without departing from the scope or spirit of the present invention. For example, a feature illustrated or described as part of one embodiment may be used together with another embodiment to produce yet another embodiment. Therefore, the present invention is intended to cover these modifications and variations within the scope of the appended claims and their equivalents.

[0038] It should be noted that these and other subsequent drawings are only examples and are not drawn to scale, and should not be used to limit the actual scope of protection required by the present invention.

[0039] The terms "first", "second", etc. may be used interchangeably to distinguish one feature from another, and are not intended to mean that each feature must be located as shown in the figures in each embodiment.

[0040] The current temperature closed-loop control collects the real-time temperature of the test piece through a temperature sensor. When it exceeds a certain threshold above the operating temperature, heating and resonance are stopped, and heating and resonance are restarted after the temperature drops. The temperature uniformity of the test piece is poor and the temperature range fluctuates greatly. Frequent stopping of heating and resonance, and then reheating and resonance, results in long test time and greatly increases the test cost. The ultrasonic resonance circuit needs to re-search the resonant frequency of the test piece when it is started. Therefore, the power of the ultrasonic generator and the stress or amplitude of the test piece gradually reach the set value. Frequent starting and closing of the ultrasonic vibration equipment directly leads to large fluctuations in the vibration load corresponding to the fatigue cycle in the start-stop stage and non-true values, and also increases the risk of failure of equipment such as the power supply.

[0041] Figure 1 A high temperature ultrasonic vibration fatigue test device is shown, which is used to perform the high temperature ultrasonic vibration fatigue test method described below. Figure 1 As shown, the high temperature ultrasonic vibration fatigue test device may include an ultrasonic vibration component 1, a heating component 2, a temperature measurement component 3, a displacement measurement component 4 and a data acquisition component 5. The ultrasonic vibration component 1 is used to apply ultrasonic vibration to the test piece 6, so that the test piece 6 has a fatigue life greater than 10 8 Ultra-high cycle fatigue of cycles. The ultrasonic vibration component 1 may include a test frame 11, an ultrasonic signal generator 12, a piezoelectric ceramic 13, an amplifier rod 14 and a computer 15. The computer 15 controls the ultrasonic signal generator 12 to emit a high-frequency sinusoidal signal to drive the piezoelectric ceramic 13 to convert the electrical signal into mechanical resonance / vibration displacement. The frequency of the high-frequency sinusoidal signal can be 20 kilohertz (KHz). The mechanical resonance displacement is usually in a few microns (um), which is increased to tens of microns with the help of the amplifier rod 14 so that the test piece 6 obtains the required vibration load stress state. The ultrasonic vibration component 1 is fixed to the test frame 11.

[0042] Continue to refer to Figure 1 The heating assembly 2 is used to heat the test piece 6. The heating assembly 2 may include a heater 21 and a power controller 22. The heater 21 may be in the form of induction heating, radiation heating, single or multiple hot air duct heating, etc. The power controller 22 is used to adjust the power of the heater 21, thereby adjusting the temperature of the test piece 6. The power controller 22 may adjust the power of the heater 21 by adjusting the frequency, current, etc. of the heater 21.

[0043] Continue to refer to Figure 1 The temperature measuring component 3 is used to measure the temperature of the test piece 6. The temperature measuring component 3 can be a non-contact measuring device such as a temperature-sensitive coating and a spectrometer, an infrared thermal imager, etc. The temperature measuring component 3 can record the temperature data of the test piece 6 into the computer 15 through the data acquisition component 5. The computer 15 adjusts the power of the heater 21 through the power controller 22 based on the temperature data to achieve the temperature closed-loop control described later.

[0044] Continue to refer to Figure 1 , the displacement measurement component 4 is used to calibrate and measure the displacement of the test piece 6 under resonance. The displacement measurement component 4 can record the displacement data into the computer 15 through the data acquisition component 5 to accurately obtain the stress state and stiffness change of the test piece 6. The displacement measurement component 4 can be a non-contact displacement measurement device 41, such as an optical displacement measurement device such as a laser displacement sensor and a laser vibrometer. The displacement measurement component 4 can measure the displacement of any end surface of the upper and lower ends of the test piece 6, so as to calculate the amplitude of the resonance of the test piece 6. The high-temperature ultrasonic vibration fatigue test device can be provided with two displacement measurement components 4, and the two displacement measurement components 4 simultaneously measure the displacement of the top end surface and the bottom end surface of the test piece 6, respectively. The ratio of the difference between the mean displacement values ​​measured by the two displacement measurement components 4 and the initial length of the test piece 6 is the elongation of the test piece 6 during the vibration self-heating or heating described later. By comparing the elongation calculated according to the material thermal expansion coefficient of the test piece 6, it can be used to assist in judging the temperature measurement accuracy of the temperature measurement component 3 during the test. The non-contact displacement measuring device 41 can be an optical displacement measuring device such as a laser displacement sensor, a laser vibrometer, etc. An optical reflection prism 42 can be set to change the measurement path, so that the non-contact displacement measuring device 41 can be conveniently arranged to measure the displacement of the top surface of the test piece 6 so that the measurement is not affected by the environment.

[0045] Continue to refer to Figure 1 The data acquisition component 5 is used to perform multi-channel high-speed acquisition of the displacement data measured by the displacement measurement component 4, the temperature data measured by the temperature measurement component 3, the resonant frequency of the high-frequency sinusoidal signal emitted by the ultrasonic signal generator 12, and the power data (such as frequency and current) of the heater 21. The resonant frequency of the high-frequency sinusoidal signal emitted by the ultrasonic signal generator 12 can be 20KHz, and the sampling rate of the data acquisition component 5 must be at least 200KHz, and 400KHz is recommended. Therefore, the data acquisition component 5 is provided with a high-speed acquisition card for signal acquisition and storage. The high-speed acquisition card of the data acquisition component 5 can also be directly installed on the computer 15, such as the PCI, USB, COM and other expansion channels of the computer 15.

[0046] If the material of the test piece 6 has high internal damping or low thermal conductivity, such as titanium alloy, resin-based composite material, etc., the high-temperature ultrasonic vibration fatigue test device can also be provided with a cooling component (not shown in the figure) around the test piece 6 to avoid the test piece 6 from self-heating due to high-frequency vibration in the room-temperature ultra-high cycle fatigue test, which leads to a decrease in fatigue performance. The cooling component can be cooled by air cooling, water cooling, etc.

[0047] High temperature ultrasonic vibration fatigue test method can be Figure 1The high-temperature ultrasonic vibration fatigue test device shown is used for execution. The high-temperature ultrasonic vibration fatigue test method is described below in combination with the above-mentioned high-temperature ultrasonic vibration fatigue test device. The high-temperature ultrasonic vibration fatigue test method includes a temperature control method for the high-temperature ultrasonic vibration fatigue test.

[0048] like Figure 5 As shown, the temperature control method includes step A. obtaining the self-heating stable temperature of the test piece 6 under the target vibration load. In step A, the test piece 6 is driven to vibrate by the ultrasonic vibration component 1, and the heating component 2 does not heat the test piece 6.

[0049] Step A may include step A1. calibrating the self-heating stable temperature of the test piece 6 under different vibration loads. Perform high-frequency resonance tests of the test piece 6 under different displacement states through the ultrasonic vibration component 1, the temperature measurement component 3, the displacement measurement component 4 and the data acquisition component 5. The ultrasonic vibration component 1 drives the test piece 6 to vibrate. The temperature measurement component 3 measures the temperature of the test piece 6. The displacement measurement component 4 measures the actual displacement and amplitude of the test piece 6, and obtains the stress state of the test piece 6 in combination with finite element analysis. The data acquisition component 5 obtains the stress state of the test piece 6 under different displacement / stress states σ according to the above data. i Self-heating temperature rise curve under Self-heating temperature rise curve The average temperature in the temperature stabilization section is the self-heating stabilization temperature. Figure 2 The test piece 6 of the nickel-based high-temperature alloy GH4169 is shown as an example under different stress states σ i Self-heating temperature rise curve under In the figure, UTS represents the tensile strength of the material. The self-heating temperature rise curve is usually divided into three stages, namely the rapid heating stage, the temperature stabilization stage and the rapid fracture temperature rise stage. Among them, the temperature stabilization stage occupies the vast majority of the cycle life. Therefore, the self-heating temperature rise curve can only record the following: Figure 2 The rapid heating period and part of the temperature stabilization period shown in the figure can usually be recorded for only 10 to 20 minutes. For example, the test piece 6 of the nickel-based high-temperature alloy GH4169 can be recorded for 1000 seconds, which is 2×10 7 The cycle lasts about 16 minutes.

[0050] Step A may also include step A2. Obtain the self-heating stable temperature of the test piece 6 under the target vibration load according to the interpolation method. For the target vibration load, according to the corresponding target stress state σk, according to different stress states σ i Self-heating temperature rise curve under Interpolate the target stress state σ k Self-heating temperature rise curve under And calculate the self-heating temperature rise curve The average temperature in the temperature stabilization section is the self-heating stabilization temperature of the test piece 6 under the target vibration load. The interpolation method may be linear interpolation, Kriging interpolation or the like.

[0051] like Figure 5 As shown, the temperature control method may also include step E. obtaining the initial heating power and initial heating time for the test piece 6 to reach the target temperature. In step E, the ultrasonic vibration component 1 does not drive the test piece 6 to vibrate, and the heating component 2 heats the test piece 6. The test piece 6 is heated and calibrated by the heating component 2, the temperature measurement component 3, the data acquisition component 5, and the computer 15 in the ultrasonic vibration component 1. In the initial heating stage, the temperature measurement component 3 records the temperature data of the test piece 6 into the computer 15 through the data acquisition component 5, and the computer 15 controls the power of the heater 21 through the power controller 22 based on the temperature data to heat the test piece 6 to the heating temperature. Figure 3 The heating temperature rise curve of the test piece 6 made of nickel-based high-temperature alloy GH4169 is shown as an example. like Figure 3 As shown, in the initial heating stage, the power controller 22 controls the power of the heater 21 by controlling the current of the heater 21. In the following description, the current of the heater 21 represents the power of the heater 21. In the initial heating stage, the heating component 2 is heated by the current I1 for the initial heating time t I0 The heating test piece 6 is heated to the heating temperature T i -ΔT j (Can also be T i , see below), where the current I1 represents the initial heating power, T i is the stable median temperature, ΔT j is the temperature control threshold. The stable temperature is the temperature margin range, which can be represented by the stable median temperature ± the temperature control threshold, that is, T i ±ΔT j .

[0052] The stable target temperature can be a temperature margin section, including the stable target median temperature T k and target temperature control threshold ΔT k , which can be represented by the stable target median temperature ± the target temperature control threshold, that is, T k ±ΔT k In the initial heating stage, the heating assembly 2 heats the test piece 6 so that the temperature of the test piece 6 rises very quickly, for example, Figure 3 As shown, the test piece 6 of the nickel-based high-temperature alloy GH4169 material is heated to 650 degrees Celsius within 10 seconds. Therefore, when the heating component 2 uses the initial heating power I1, based on the heating temperature T i -ΔTj Heating temperature rise curve In the initial heating stage, according to the heating target temperature T k -ΔT k (Can also be T k , see below), interpolate to get the initial heating time t I0，k The heating component 2 can be heated by the initial heating power I1 and the initial heating time t IO，k The test piece 6 is heated to reach the target temperature T k -ΔT k (Can also be T k , as described later). The interpolation method may be linear interpolation, Kriging interpolation, or the like.

[0053] like Figure 5 As shown, the temperature control method further includes step B. obtaining an initial stable heating power and an initial stable heating duty cycle for maintaining the test piece 6 at a stable target heating temperature, wherein the stable target heating temperature is the stable target temperature minus the self-heating stable temperature. In step B, the ultrasonic vibration component 1 does not drive the test piece 6 to vibrate, and the heating component 2 heats the test piece 6.

[0054] Step B may include step B1. Calibrate the initial stable heating power and initial stable heating duty cycle of the test piece 6 maintained at different stable temperatures. The test piece 6 is heated and calibrated by the heating component 2, the temperature measurement component 3, the data acquisition component 5, and the computer 15 in the ultrasonic vibration component 1. In the stable heating stage, the temperature measurement component 3 records the temperature data of the test piece 6 into the computer 15 through the data acquisition component 5. The computer 15 adjusts the power and duty cycle of the heater 21 through the power controller 22 based on the temperature data to achieve temperature closed-loop control, and heats the test piece 6 so that its temperature is controlled at a stable temperature. Figure 3 As shown, in the stable heating stage, the power controller 22 adjusts the power of the heater 21 by adjusting the current and duty cycle of the heater 21. The heating component 2 is heated by a current I i，2 and duty cycle η i，j The test piece 6 is heated to a stable temperature T i ±ΔT j , where the current I i，2 Characterizes the initial stable heating power, η i，j is the initial stable heating duty cycle, ηi,j is the current on time t of the heating component 2 during the working cycle Ii，j The whole working cycle t i，j By controlling the current I i，2 At different duty cycles η i，j Work to calibrate the temperature control threshold ΔT j , and according to the stable median temperature Ti and target temperature control threshold ΔT k , interpolate to get the corresponding initial stable heating duty cycle η i，k The interpolation method may be linear interpolation, Kriging interpolation or the like.

[0055] Step B may also include step B2. Obtaining the initial stable heating power and initial stable heating duty cycle for maintaining the test piece 6 at the stable target heating temperature according to the interpolation method. The stable target heating temperature is the stable target temperature T k ±ΔT k Self-heating stable temperature to reduce target vibration load The stable target median temperature T can be used during interpolation k Simplified stable target temperature T k ±ΔT k , the stable target heating temperature can be simplified to the stable target median temperature T k Self-heating stable temperature to reduce target vibration load That is to say Based on different stable median temperatures T i Heating temperature rise curve The stable heating stage corresponds to different initial stable heating powers I i，2 , according to the simplified stable target heating temperature Interpolation is used to obtain the corresponding initial stable heating power I k，2 , based on different stable median temperatures T i Heating temperature rise curve The stable heating stage corresponds to different initial stable heating duty cycles η i，k , according to the simplified stable target heating temperature Interpolation gives the corresponding initial stable heating duty cycle η k,init In step C described later, the heating component 2 can be heated by initially stabilizing the heating power I k,2 and the initial stable heating duty cycle η i，k The test piece 6 is heated to maintain a stable target temperature T k ±ΔT k The interpolation method may be linear interpolation, Kriging interpolation or the like.

[0056] like Figure 5 As shown, the temperature control method may further include step F. executing an initial temperature rise phase, heating the test piece 6 using an initial temperature rise heating power and an initial temperature rise heating time, so that the test piece 6 is heated to a target temperature. Figure 4 The temperature control curve of the test piece 6 of the nickel-based high-temperature alloy GH4169 in the high-temperature ultrasonic fatigue vibration test is shown as an example. Figure 4As shown, in the initial temperature rise stage, the heating component 2 is heated by the initial temperature rise power I1 and the initial temperature rise heating time t IO,k The test piece 6 is heated to reach the target temperature T k -ΔT k (Can also be T k , see below).

[0057] like Figure 5 As shown, the temperature control method further includes step C. executing the initial temperature stabilization stage, applying the target vibration load to the test piece 6, and heating the test piece 6 using the initial stable heating power and the initial stable heating duty cycle, so that the temperature of the test piece 6 is maintained at a stable target temperature. Figure 4 As shown, when the data acquisition component 5 records that the temperature of the test piece 6 measured by the temperature measurement component 3 reaches the heating target temperature T k -ΔT k (Can also be T k , as described later), the initial temperature rise phase ends and the initial temperature stabilization phase begins. In the initial temperature stabilization phase, the ultrasonic vibration component 1 drives the test piece 6 to vibrate, so that the test piece 6 generates a target stress state σ corresponding to the target vibration load. k At the same time, the heating component 2 is heated by the initial stable power I k，2 and the initial stable heating duty cycle η i，k The test piece 6 is heated to maintain a stable target temperature T k ±ΔT k .

[0058] Step B takes into account the self-heating of the test piece 6 under the target vibration load, removes the self-heating stable temperature under the target vibration load from the stable target temperature, and obtains the initial stable heating power and initial stable heating duty cycle for heating the test piece 6 to maintain it at the stable target temperature in step C according to the stable target heating temperature formed by subtracting the self-heating stable temperature from the stable target temperature. This improves the temperature uniformity of the test piece 6 in step C, reduces the temperature fluctuation range, avoids frequent starting and stopping of the heating and vibration equipment, thereby shortening the test time, improving the test accuracy, and reducing the test cost.

[0059] The heating target temperature can be the stable target median temperature T k Reduce target temperature control threshold ΔT k , that is, T k -ΔT k The heating target temperature can also be the stable target median temperature T k The heating target temperature is the condition for entering the initial temperature stabilization stage from the initial temperature heating stage, and determines the timing for entering the initial temperature stabilization stage from the initial temperature heating stage. The heating target temperature is the lower threshold T of the stabilization target temperature. k -ΔTk , the upper threshold T of the stable target temperature k ±ΔT k The difference is large, so that the heating component 2 passes the initial stable heating power I k，2 and the initial stable heating duty cycle η i，k Heating the test piece 6 to maintain a stable target temperature T k ±ΔT k When the temperature of the test piece 6 is not easy to exceed the upper threshold value T of the stable target temperature k +ΔT k , the temperature control effect is good. The heating target temperature is the stable target median temperature T k , heating the test piece 6 to a higher temperature during the initial temperature rise stage and then entering the initial temperature stabilization stage, shortening the time for heating the test piece 6 during the initial temperature stabilization stage and reducing the test time.

[0060] like Figure 5 As shown, the temperature control method further includes step D. executing the temperature closed-loop stabilization phase, obtaining the feedback stable heating power and the feedback stable heating duty cycle according to the temperature of the test piece 6, and heating the test piece 6 using the feedback stable heating power and the feedback stable heating duty cycle, so that the temperature of the test piece 6 is maintained at a stable target temperature. After executing the initial temperature stabilization phase, the temperature of the test piece 6 measured by the temperature measurement component 3 is continuously recorded by the data acquisition component 5, and the heating power and the heating duty cycle are closed-loop controlled accordingly.

[0061] Step D may include making the post-stable heating duty cycle equal to the pre-stable heating duty cycle, and making the post-stable heating power equal to the pre-stable heating power, if the temperature change rate of the test piece 6 is greater than zero, then obtaining a post-stable heating duty cycle that is less than the pre-stable heating duty cycle, if the temperature change rate of the test piece 6 is less than zero, then obtaining a post-stable heating duty cycle that is greater than the pre-stable heating duty cycle, and if the temperature change rate of the test piece 6 is equal to zero, then obtaining a post-stable heating duty cycle that is equal to the pre-stable heating duty cycle. The pre-stable heating power is the initial stable heating power, the pre-stable heating duty cycle is the initial stable heating duty cycle, the post-stable heating power is the feedback stable heating power, and the post-stable heating duty cycle is the feedback stable heating duty cycle. Alternatively, step D is iteratively executed, the pre-stable heating power is the feedback stable heating power of the previous step D, the pre-stable heating duty cycle is the feedback stable heating duty cycle of the previous step D, the post-stable heating power is the feedback stable heating power of the next step D, and the post-stable heating duty cycle is the feedback stable heating duty cycle of the next step D.

[0062] like Figure 3As shown, step D is iteratively executed, the front stable heating power is the feedback stable heating power of the previous step D, the front stable heating duty cycle is the feedback stable heating duty cycle of the previous step D, the rear stable heating power is the feedback stable heating power of the next step D, and the rear stable heating duty cycle is the feedback stable heating duty cycle of the next step D. Take this case as an example:

[0063] Let η k，i+1 =η k,i , and let I k，2，i+1 =I k，2，i ,

[0064] like but

[0065] like but

[0066] like Then η k，i+1 =η k，i .

[0067] Among them, η k，i is the pre-stable heating duty cycle, η k，i+1 is the post-stabilization heating duty cycle, I k，2，i is the front stable heating power, I k，2，i+1 To stabilize the heating power, is the temperature change rate of the test piece 6, α is the first coefficient, which is related to the magnetic permeability of the material of the test piece 6, etc., and α is usually taken as 2.0.

[0068] Step D may also include obtaining a post-stable heating power less than the previous stable heating power if the temperature of the test piece 6 is greater than the stable target temperature, obtaining a post-stable heating power greater than the previous stable heating power if the temperature of the test piece 6 is less than the stable target temperature, and obtaining a post-stable heating power equal to the previous stable heating power if the temperature of the test piece 6 is equal to the stable target temperature. The previous stable heating power is the initial stable heating power, and the post-stable heating power is the feedback stable heating power. Alternatively, step D is iteratively executed, the previous stable heating power is the feedback stable heating power of the previous step D, and the post-stable heating power is the feedback stable heating power of the next step D.

[0069] like Figure 3 As shown, step D is iteratively executed, the front stable heating power is the feedback stable heating power of the previous step D, and the rear stable heating power is the feedback stable heating power of the latter step D. Take this case as an example:

[0070] If T>T k +μ·ΔT k , then I k，2，i+1 =β·I k，2，i ;

[0071] If T < T k -μ•ΔT k , then I k，2，i+1 =(2.0-β)·I k，2，i ;

[0072] If T≤T k +μ·ΔT k , and T ≥ T k -μ·ΔT k , then I k，2，i+1 =I k，2，i .

[0073] Where, T is the temperature of the test piece 6, I k，2，i+1 is the post-stabilization heating power, I k，2，i is the pre-stabilized heating power, β is the second coefficient, which is related to the material magnetic permeability of the test piece 6, etc. β is usually set to 0.7, T k +μ·ΔT k The target median temperature is T k Add temperature control sensitivity threshold μ·ΔT k , which gives a margin to the heating power adjustment condition, ΔT k is the target temperature control threshold, μ is the temperature control sensitivity coefficient, and μ is recommended to be 0.75. Similarly, T k -μ·ΔT k The target median temperature is T k Reduce temperature control sensitivity threshold μ·ΔT k , thereby giving margin to the adjustment conditions of the heating power.

[0074] The temperature control method of the high-temperature ultrasonic vibration fatigue test calibrates the self-heating law of the high-frequency resonance of the test piece 6 under different vibration loads and the temperature rise law of the heating component 2 heating the test piece 6, and coordinately controls the control parameters of the heating component 2, thereby providing a closed-loop temperature control strategy for the high-temperature ultrasonic vibration fatigue test, avoiding a significant increase in the test cycle and the risk of equipment failure caused by high-frequency intermittent loading during the test. At the same time, the initial control parameters used are combined with the closed-loop temperature control strategy to ensure that the temperature regulation is more active and the fluctuation threshold and range are more controllable.

[0075] In the temperature control method of the high-temperature ultrasonic vibration fatigue test, if the internal damping of the material of the test piece 6 is very large, resulting in a large temperature fluctuation range of the test piece 6, an adaptive control strategy can be adopted for step D to automatically optimize the values ​​of α and β.

[0076] In the high-temperature ultrasonic vibration fatigue test method, the displacement measurement component 4 can measure the displacement of any end surface of the test piece 6 at the upper and lower positions, and the data acquisition component 5 collects the displacement data measured by the displacement measurement component 4, thereby calculating the amplitude of the resonance of the test piece 6, which can be used to judge the conditions for test shutdown, and can also be used to analyze the stress changes of the test piece 6 under the vibration load cycle.

[0077] In the high-temperature ultrasonic vibration fatigue test method, two displacement measurement components 4 simultaneously measure the displacement of the top and bottom surfaces of the test piece 6, and the data acquisition component 5 collects the displacement data measured by the displacement measurement component 4. The ratio of the difference between the average displacements measured by the two displacement measurement components 4 and the initial length of the test piece 6 is the elongation of the test piece 6 when it is vibrating and self-heating or heated. The comparison with the elongation calculated based on the thermal expansion coefficient of the material of the test piece 6 can be used to assist in judging the temperature measurement accuracy of the temperature measurement component 3 during the test.

[0078] In the high-temperature ultrasonic vibration fatigue test method, the data acquisition component 5 collects the ultrasonic signal generator 12 to search the resonant frequency of the test piece 6 in real time, thereby recording the stiffness change of the test piece 6, which can be used to determine the damage evolution process of the test piece 6 and as a judgment condition for shutdown work.

[0079] Although the present invention is disclosed as above by the embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention.

Claims

1. A temperature control method for high temperature ultrasonic vibration fatigue test, characterized in that include: Step A. Obtaining the self-heating stable temperature of the test piece under the target vibration load; Step B. obtaining an initial stable heating power and an initial stable heating duty cycle for maintaining the test piece at a stable target heating temperature, wherein the stable target heating temperature is the stable target temperature minus the self-heating stable temperature; Step C. executing an initial temperature stabilization phase, applying the target vibration load to the test piece, and heating the test piece using the initial stable heating power and the initial stable heating duty cycle, so that the temperature of the test piece is maintained at the stable target temperature; as well as Step D. execute the temperature closed-loop stabilization phase, obtain feedback stable heating power and feedback stable heating duty cycle according to the temperature of the test piece, and use the feedback stable heating power and the feedback stable heating duty cycle to heat the test piece to maintain the temperature of the test piece at the stable target temperature.

2. The temperature control method for high temperature ultrasonic vibration fatigue test according to claim 1, characterized in that Before step C, the method further comprises: Step E. obtaining an initial heating power and an initial heating time for the test piece to reach a target heating temperature; and Step F: performing an initial temperature rise phase, heating the test piece using the initial temperature rise heating power and the initial temperature rise heating time, so that the test piece is heated to the temperature rise target temperature.

3. The temperature control method for high temperature ultrasonic vibration fatigue test according to claim 2, characterized in that: The stable target temperature is the stable target median temperature ± the target temperature control threshold; The heating target temperature is the stable target median temperature or the stable target median temperature minus the target temperature control threshold.

4. The temperature control method for high temperature ultrasonic vibration fatigue test according to claim 1, characterized in that The step A comprises: Step A1. calibrating the self-heating stable temperature of the test piece under different vibration loads; and Step A2: Obtain the self-heating stable temperature of the test piece under the target vibration load according to the interpolation method.

5. The temperature control method for high temperature ultrasonic vibration fatigue test according to claim 1, characterized in that The step B comprises: Step B1. calibrating the initial stable heating power and the initial stable heating duty cycle of the test piece maintained at different stable temperatures; and Step B2. Obtaining, by interpolation method, an initial stable heating power and an initial stable heating duty cycle for maintaining the test piece at the stable target heating temperature.

6. The temperature control method for high temperature ultrasonic vibration fatigue test according to claim 1, characterized in that The step D comprises: The post-stable heating duty cycle is set equal to the pre-stable heating duty cycle, and the post-stable heating power is set equal to the pre-stable heating power. If the temperature change rate of the test piece is greater than zero, a post-stable heating duty cycle smaller than the pre-stable heating duty cycle is obtained. If the temperature change rate of the test piece is less than zero, a post-stable heating duty cycle greater than the pre-stable heating duty cycle is obtained. If the temperature change rate of the test piece is equal to zero, a post-stable heating duty cycle equal to the pre-stable heating duty cycle is obtained.

7. The temperature control method for high temperature ultrasonic vibration fatigue test according to claim 6, characterized in that The step D also includes: If the temperature of the test piece is greater than the stable target temperature, a post-stable heating power less than the front stable heating power is obtained; if the temperature of the test piece is less than the stable target temperature, a post-stable heating power greater than the front stable heating power is obtained; if the temperature of the test piece is equal to the stable target temperature, a post-stable heating power equal to the front stable heating power is obtained.

8. The temperature control method for high temperature ultrasonic vibration fatigue test according to claim 7, characterized in that: The front stable heating power is the initial stable heating power, the front stable heating duty cycle is the initial stable heating duty cycle, the rear stable heating power is the feedback stable heating power, and the rear stable heating duty cycle is the feedback stable heating duty cycle; or The step D is iteratively executed, the front stable heating power is the feedback stable heating power of the previous step D, the front stable heating duty cycle is the feedback stable heating duty cycle of the previous step D, the rear stable heating power is the feedback stable heating power of the next step D, and the rear stable heating duty cycle is the feedback stable heating duty cycle of the next step D.

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