High-temperature loading equivalent monitoring method for high-temperature random vibration fatigue test

Abstract

The invention belongs to the technical field of aerospace, and particularly relates to a high-temperature loading equivalent monitoring method for a high-temperature random vibration fatigue test, which comprises the following steps: S1, manufacturing a false piece made of the same material as a test piece; s2, arranging temperature measuring points which are the same as the test piece on the dummy piece, arranging thermocouples on the temperature measuring points on the dummy piece and the test piece, heating the dummy piece and the test piece at the same time in a static state, and obtaining the temperatures of the temperature measuring points of the dummy piece and the test piece through the thermocouples; s3, temperature correction is calculated based on the temperature of the test piece temperature measuring point and the temperature of the fake piece temperature measuring point; s4, the target temperature of the temperature measuring point of the test piece is given, and the temperature of the temperature measuring point of the fake piece is calculated based on the temperature correction amount; and S5, dismounting the thermocouple of the temperature measuring point on the test piece, heating the test piece and the false piece at the same time, and when the temperature measuring point of the false piece reaches the calculated temperature of the temperature measuring point of the false piece, starting a high-temperature random vibration fatigue test on the test piece.

Description

Technical Field

[0001] The present application belongs to the technical field of aerospace, and in particular to a high temperature loading equivalent monitoring method for a high temperature random vibration fatigue test. Background Art

[0002] Vibration fatigue is common in thin-walled structures in aerospace, such as aircraft engine flame tubes, thermal insulation and vibration shields, ramjet engine tail nozzles, and supersonic aircraft outer skins. In addition to bearing mechanical vibration loads, aerodynamic loads, and strong sound loads, these thin-walled structures are also in severe high-temperature load environments. These complex environments seriously affect the mechanical properties of thin-walled structures, resulting in reduced structural strength and stability, and even fatigue cracks in certain parts, posing huge safety hazards. Therefore, the study of high-temperature random vibration fatigue of thin-walled structures in the aerospace field occupies an extremely important position in the thermal strength design and verification of aircraft structures.

[0003] In high-temperature random vibration fatigue tests, in order to ensure that the test environment meets the predetermined requirements, the temperature of the test piece must be accurately measured. Common temperature measurement methods include non-contact and contact measurements. Non-contact temperature measurement is mainly an infrared thermometer, which calculates the radiation energy spectrum of the structure by measuring the radiation energy spectrum of the structure. However, in the process of heating the structure with an infrared lamp, the structural radiation energy of the structure itself will be submerged, and the radiation energy spectrum of the structure cannot be accurately measured. Contact temperature measurement is mainly through thermocouples. Thermocouples are a closed loop composed of two wires of different materials. One end is called the cold end, which is connected to the measuring instrument, and the other end is called the hot end, which is placed at the temperature measurement location.

[0004] At present, the existing technology for structural thermal test laboratories also mainly uses thermocouples for temperature measurement, but how to connect the thermocouple to the test piece is a difficult problem. Currently, common installation methods include threaded connection, welding, and high-temperature glue and tape connection. Among them, threaded connection and welding are mainly used in metal structures. Threaded connection is the easiest to install, but it will change the mechanical properties of the structure; welding thermocouples is a huge workload and is not suitable for certain metals such as titanium alloys. The high-temperature glue and tape connection is not stable enough and is easy to fall off during the thermal vibration test, resulting in the inability of the thermocouple to continuously monitor the temperature changes of the measuring point.

[0005] Due to the long duration and complexity of high-temperature random vibration fatigue tests, how to accurately and continuously monitor the temperature of the structure is an urgent problem to be solved. When using infrared lamps to heat the structure, the infrared thermometer cannot accurately measure the temperature of the structure, and the thermocouple and the test piece usually need to be in direct contact to monitor temperature changes. However, due to the combined effects of vibration and temperature changes, the thermocouple is easy to fall off during the test, resulting in the inability to continuously monitor the temperature changes of the measuring points. This not only affects the accuracy of the test data, but also increases the uncertainty and risk of the test. Therefore, the development of a device and method that can equivalently monitor temperature changes is of great significance to improving the reliability and accuracy of high-temperature random vibration fatigue tests. Summary of the invention

[0006] In order to solve the above problems, the present application provides: 1. A high temperature loading equivalent monitoring method for high temperature random vibration fatigue test,

[0007] Step S1: making a dummy piece with the same material as the test piece;

[0008] Step S2: Arrange the same temperature measuring points on the dummy as on the test piece, and arrange thermocouples at the temperature measuring points on the dummy and the test piece, place the dummy and the test piece in a high temperature box, heat the dummy and the test piece at the same time in a static state, and obtain the temperatures of the temperature measuring points of the dummy and the test piece through the thermocouples;

[0009] Step S3: calculating the temperature correction amount based on the temperatures of the test piece temperature measurement point and the dummy piece temperature measurement point;

[0010] Step S4: Given a target temperature of the test piece temperature measuring point, the temperature of the dummy piece temperature measuring point is calculated based on the temperature correction amount;

[0011] Step S5: Remove the thermocouple at the temperature measuring point on the test piece, heat the test piece and the dummy at the same time, and when the temperature measuring point of the dummy reaches the temperature calculated from the temperature measuring point of the dummy, start the high temperature random vibration fatigue test on the test piece.

[0012] Preferably, step S2 specifically includes:

[0013] The dummy and the test piece are heated simultaneously until the temperature measuring point of the dummy reaches the target temperature, the temperature of the temperature measuring point of the test piece is obtained, and a first correction amount between the temperature of the temperature measuring point of the test piece and the target temperature is calculated;

[0014] The dummy and the test piece are heated simultaneously until the temperature measuring point of the test piece reaches the target temperature, the temperature of the temperature measuring point of the dummy is obtained, and a second correction amount between the temperature of the temperature measuring point of the dummy and the target temperature is calculated;

[0015] The correction amount of the target temperature is obtained based on the first correction amount and the second correction amount.

[0016] Preferably, the target temperature includes a plurality of target temperatures.

[0017] Preferably, step S2 further comprises:

[0018] The temperature of the temperature measuring point of the test piece and the temperature of the temperature measuring point of the dummy are obtained to establish a measuring point temperature and time curve, the correction amount and time curve is calculated, the correction amount in the time interval with the smallest correction amount fluctuation is used as the correction amount of the target temperature, and the time is used as the heating time.

[0019] Preferably, the target temperature includes 300°C and 500°C.

[0020] The temperature measuring points include a plurality of points, and correction value versus time curves of the plurality of temperature measuring points are obtained, and the temperature measuring point with the smallest fluctuation is used as the temperature measuring point for the high temperature random vibration fatigue test in step S5.

[0021] The advantages of the present application include: the present invention designs a dummy and controls the temperature measurement points on the dummy so that the temperature distribution on the test piece meets the test requirements. This can avoid the loss or distortion of temperature data due to reasons such as thermocouple shedding, thereby improving the accuracy of the test data, and can also ensure the stability of the temperature of the test piece during the test and the long-term test loading requirements. The temperature equivalent monitoring device and method provided by this method can not only be completely separated from the vibration loading system and remain stationary during the vibration loading process, but also can well reflect the temperature distribution of key parts of the test piece, which is helpful to promote thermal structure design in fields such as aerospace. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a random vibration fatigue test specimen for a certain material;

[0023] Figure 2 This is a schematic diagram of the test measurement point layout;

[0024] Figure 3 It is the temperature-time curve of the measuring point (test 1);

[0025] Figure 4 This is the temperature-time curve of the measuring point (Test 2);

[0026] Figure 5 This is the temperature-time curve of the measuring point (Test 3);

[0027] Figure 6 It is the temperature-time curve of the measuring point (Test 4);

[0028] Figure 7 It is the temperature-time curve of the measuring point (Test 5);

[0029] Figure 8This is the temperature-time curve of the measuring point (Test 6). DETAILED DESCRIPTION

[0030] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present application will be further described in detail in detail and in detail in conjunction with the accompanying drawings. It can be understood that the specific embodiments described here are only partial embodiments of the present application, which are only used to explain the present application, not to limit the present application. It should be noted that, for the convenience of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design. In the absence of conflict, the embodiments in the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0031] In addition, it should be noted that, unless otherwise clearly specified and limited, the words "installed", "connected", "connected" and similar terms used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, an indirect connection through an intermediate medium, or the internal connection of two components. Technical personnel in the field can understand their specific meanings in this application according to the specific circumstances.

[0032] In the random vibration fatigue performance test of materials, cantilever standard parts are usually used for testing. Therefore, taking a random vibration fatigue test piece of a certain material as an example, high temperature loading is heated by a high temperature box, and the shape and size of the test piece are marked as follows Figure 1 shown.

[0033] 1. Design of dummy parts and measuring points

[0034] The schematic diagram of the test piece is as follows: Figure 1 As shown, there is no hole end constraint, the total length of the test piece is 190mm, and the constraint length is 38.5mm. The dummy is a rectangular structure with a length of 151.5mm, a width of 30mm, and a thickness of 1.5mm. The material is consistent with the test piece. The dummy is placed at the bottom of the heating area of ​​the high-temperature box, and the plane where the thermocouple is installed on the dummy faces the left view of the test piece.

[0035] Assume that three temperature measuring points (C1, C2 and C3) are arranged on the test piece, and the measuring points (D1, D2 and D3) on the dummy piece correspond to them one by one, as shown in the following figure: Figure 2 In order to reduce the impact of air convection and make the temperature of the measuring point on the dummy as close as possible to that of the test piece, the dummy is raised as much as possible with insulation material without hindering the vibration of the test piece and the arrangement of the thermocouple wires, so that the upper surface of the dummy and the lower surface of the left view of the test piece are as close as possible.

[0036] 2. Working condition design and high temperature loading verification

[0037] In order to enhance the reliability and applicability of the high-temperature loading equivalent monitoring scheme, the verification test is divided into two temperature states of 300℃ and 500℃, and the following high-temperature loading test is carried out.

[0038] The test environment temperature is 11.5℃.

[0039] Test 1: The temperature of the measuring point C1 is controlled to be 300℃, and the heating rate is 1℃ / s. The temperature change curves of all measuring points of the test piece and the dummy piece are as follows: Figure 3 shown.

[0040] After constant temperature, the temperature of measuring point C1 fluctuates between 295.0℃-312.0℃, and the temperature of measuring point D1 fluctuates between 285.8℃-295.1℃. As time goes by, the temperature of measuring point D1 gradually approaches that of measuring point C1, and the temperature of measuring point D2 gradually approaches that of measuring point C2.

[0041] Test 2: The temperature of the measuring point C1 is controlled to 500℃, and the heating rate is 1℃ / s. The temperature change curves of all measuring points of the test piece and the dummy piece are as follows: Figure 4 shown.

[0042] After constant temperature, the temperature of measuring point C1 fluctuates between 489.1℃-511.1℃, the temperature of measuring point D1 fluctuates between 482.8℃-494.4℃, and as time goes by, the temperature of measuring point D1 gradually approaches measuring point C1, the temperature of measuring point D2 gradually approaches measuring point C2, and the temperature of measuring point D3 gradually approaches measuring point C3.

[0043] Test 3: The temperature of the measuring point D1 is controlled to 300℃, and the heating rate is 1℃ / s. The temperature change curves of all measuring points of the test piece and the dummy piece are as follows: Figure 5 shown.

[0044] After constant temperature, the temperature of measuring point C1 fluctuates between 281.2℃-337.1℃, and the temperature of measuring point D1 fluctuates between 292.8℃-318.9℃. As time goes by, the temperature fluctuation range of measuring point D1 completely enters the temperature fluctuation range of C1, and the temperature fluctuation range of measuring point D2 completely enters the temperature fluctuation range of C2.

[0045] Test 4: The temperature of the measuring point D1 is controlled to 500℃, and the heating rate is 1℃ / s. The temperature change curves of all measuring points of the test piece and the dummy piece are as follows: Figure 6 shown.

[0046] After constant temperature, the temperature of measuring point C1 fluctuates between 486.8℃-537.4℃, and the temperature of measuring point D1 fluctuates between 490.2℃-512.5℃. As time goes by, the temperature fluctuation range of measuring point D1 completely enters the temperature fluctuation range of C1, and the temperature fluctuation range of measuring point D2 completely enters the temperature fluctuation range of C2.

[0047] According to the tests and analysis of the previous four experiments, when the temperature control point is C1 and the control temperature is 300℃ and 500℃, the temperature of the D1 measuring point is lower than the control temperature. When the temperature control point is at D1, the temperature of the test piece measuring point C1 is higher and has a larger fluctuation range than the temperature measured when the temperature control point is set to C1. Therefore, when the temperature control measuring point is changed to D1, the control temperature setting should be slightly lower than the target temperature. According to the test results of Experiment 1 and Experiment 2, setting the control temperature of the temperature control point D1 to 290℃ and 480℃ respectively can make the temperature of the temperature measuring point C1 300℃ and 500℃. To verify this hypothesis, continue the following experiments.

[0048] Test 5: The temperature of the measuring point D1 is controlled to 290℃, and the heating rate is 1℃ / s. The temperature change curves of all measuring points of the test piece and the dummy piece are as follows: Figure 7 shown.

[0049] After constant temperature, the temperature of measuring point C1 fluctuates between 276.1℃-328.3℃, and the temperature of measuring point D1 fluctuates between 284.1℃-307.3℃. As time goes by, the temperature fluctuation range of measuring point D1 completely enters the temperature fluctuation range of C1, and the temperature fluctuation range of measuring point C1 gradually shrinks. The temperature change of measuring point C2 is similar to that of measuring point C1.

[0050] Test 6: The temperature of the measuring point D1 is controlled to 480℃, and the heating rate is 1℃ / s. The temperature change curves of all measuring points of the test piece and the dummy piece are as follows: Figure 8 shown.

[0051] After constant temperature, the temperature of measuring point C1 fluctuates between 470.3℃-522.7℃, and the temperature of measuring point D1 fluctuates between 470.3℃-492.2℃. As time goes by, the temperature fluctuation range of measuring point D1 completely enters the temperature fluctuation range of C1, and the temperature fluctuation range of measuring point D2 completely enters the temperature fluctuation range of C2.

[0052] In summary, controlling the temperature of the dummy at the same location as the test piece can not only completely separate the vibration loading system from the static state during the vibration loading process, but also well reflect the temperature distribution of the key parts of the test piece, indicating that the present invention is effective. However, when the dummy measuring point is used as the temperature control point, the temperature of the test piece measuring point is higher than the temperature measured on the test piece when the temperature control point is set, and the fluctuation range is larger. In order to meet the requirements of continuous and stable high-temperature loading in the thermal vibration test, the temperature setting of the measuring point on the dummy is slightly lower than the target temperature, which can be obtained by controlling the temperature of the test piece measuring point to test the temperature of the equivalent measuring point of the dummy during the pre-test.

[0053] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A high temperature loading equivalent monitoring method for high temperature random vibration fatigue test, characterized in that: Step S1: making a dummy piece with the same material as the test piece; Step S2: Arrange the same temperature measuring points on the dummy as on the test piece, and arrange thermocouples at the temperature measuring points on the dummy and the test piece, place the dummy and the test piece in a high temperature box, heat the dummy and the test piece at the same time in a static state, and obtain the temperatures of the temperature measuring points of the dummy and the test piece through the thermocouples; Step S3: calculating the temperature correction amount based on the temperatures of the test piece temperature measurement point and the dummy piece temperature measurement point; Step S4: Given a target temperature of the test piece temperature measuring point, the temperature of the dummy piece temperature measuring point is calculated based on the temperature correction amount; Step S5: Remove the thermocouple at the temperature measuring point on the test piece, heat the test piece and the dummy at the same time, and when the temperature measuring point of the dummy reaches the temperature calculated from the temperature measuring point of the dummy, start the high temperature random vibration fatigue test on the test piece.

2. The high temperature loading equivalent monitoring method for high temperature random vibration fatigue test according to claim 1, characterized in that: Step S2 specifically includes: The dummy and the test piece are heated simultaneously until the temperature measuring point of the dummy reaches the target temperature, the temperature of the temperature measuring point of the test piece is obtained, and a first correction amount between the temperature of the temperature measuring point of the test piece and the target temperature is calculated; The dummy and the test piece are heated simultaneously until the temperature measuring point of the test piece reaches the target temperature, the temperature of the temperature measuring point of the dummy is obtained, and a second correction amount between the temperature of the temperature measuring point of the dummy and the target temperature is calculated; The correction amount of the target temperature is obtained based on the first correction amount and the second correction amount.

3. The high temperature loading equivalent monitoring method for high temperature random vibration fatigue test according to claim 2, wherein the target temperature includes multiple ones.

4. The high temperature loading equivalent monitoring method for high temperature random vibration fatigue test according to claim 2, step S2 further comprises: The temperature of the temperature measuring point of the test piece and the temperature of the temperature measuring point of the dummy are obtained to establish a measuring point temperature and time curve, the correction amount and time curve is calculated, the correction amount in the time interval with the smallest correction amount fluctuation is used as the correction amount of the target temperature, and the time is used as the heating time.

5. The high temperature loading equivalent monitoring method for high temperature random vibration fatigue test according to claim 2, wherein the target temperature includes 300°C and 500°C.

6. The high-temperature loading equivalent monitoring method for high-temperature random vibration fatigue test according to claim 4, wherein the temperature measuring points include multiple ones, and correction value and time curves of the multiple temperature measuring points are obtained, and the temperature measuring point with the smallest fluctuation is used as the temperature measuring point of the high-temperature random vibration fatigue test in step S5.

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