Testing device and method for measuring dynamic load in static strain load calibration mode

Abstract

The invention belongs to the technical field of aircraft ground tests, and discloses a test device and method for measuring a dynamic load in a static strain load calibration mode, the device comprises four strain gauges, and the four strain gauges are respectively pasted on four centrosymmetric point positions of the same cross section of a rod piece; wherein every two strain gauges with symmetrical point positions form a group, the strain gauges in the same group are pasted in the same direction, the strain gauges in different groups are pasted in different directions, and the pasting directions are divided into the axial direction of the rod piece and the normal direction of the rod piece; the four strain gauges are connected in pairs to form a full-bridge circuit. According to the method, full-bridge strain measurement is adopted, and strain measurement errors caused by bending, temperature change and noise vibration are counteracted according to the principle that adjacent arms of a full-bridge circuit are subtracted and opposite arms are added. According to the arrangement mode of the load calibration strain gauges disclosed by the invention, errors caused by various interferences in the dynamic test process can be effectively eliminated, the measurement precision is greatly improved, the dynamic load can be accurately measured through a strain-load static calibration method, a good test effect can be achieved, and the test purpose is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft ground tests, and relates to a measurement method in a static strain-load calibration mode, and in particular to a test device and method for measuring dynamic load in a static strain-load calibration mode. Background Art

[0002] When performing performance tests on rod-type aircraft, it is necessary to measure the dynamic or even transient loads on the rods. Force sensors cannot be installed on the rods, so the common method is to attach a strain gauge to the rods for static strain-load calibration, and then calculate the load based on the strain value measured dynamically. Since strain gauges are sensitive to factors such as temperature, noise, and electromagnetic interference in the dynamic test environment, the rods may be deformed by bending and torsion during the test, which may affect the measurement results. Therefore, there are problems such as large errors between the measurement results and the theoretical values ​​during the dynamic measurement process. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a test device and method for measuring dynamic load by static strain load calibration, which can effectively remove various interference factors in the measurement of dynamic load of rods during dynamic tests and greatly improve the measurement accuracy.

[0004] The technical solution of the present invention is as follows:

[0005] A test device for measuring dynamic load by static strain load calibration method comprises four strain gauges, which are respectively pasted on four centrally symmetrical points of the same cross section of a rod; wherein, every two strain gauges at mutually symmetrical points form a group, the strain gauges in the same group have the same pasting direction, and the strain gauges in different groups have different pasting directions, and the pasting directions are divided into the axial direction of the rod and the normal direction of the rod; the four strain gauges are connected in pairs to form a full-bridge circuit.

[0006] Furthermore, it also includes a strain measuring instrument and four output wires, and the four output wires are respectively connected to the strain measuring instrument and the four strain gauges.

[0007] A test method for measuring dynamic load by static strain load calibration, wherein four strain gauges are marked as R1, R2, R3 and R4 in the order of cross-section arrangement, wherein R1 and R3 are strain gauges pasted along the axial direction of the rod, and R2 and R4 are strain gauges pasted along the normal direction of the rod; four output wires are respectively excitation +, excitation -, feedback +, and feedback - wires; full-bridge strain measurement is adopted, and according to the principle of subtracting adjacent arms and adding opposite arms of the full-bridge circuit, the strain measurement errors caused by bending, temperature change and noise vibration are offset.

[0008] Furthermore, during static calibration, a static load F is applied to the rod, the strain gauge reading ε is read, and then the εF axis and εF method are calculated; the εF axis is the axial strain value caused entirely by the load F, and the εF method is the normal strain value caused entirely by the load F.

[0009] Furthermore, given a linearly varying static load F value, after multiple rounds of static calibration, the strain calibration coefficient K value is obtained. The strain calibration coefficient K is a binary function of the εF axis and the εF method.

[0010] Furthermore, the strain of R1 is ε1=εF axis, the strain of R2 is ε2=εF method=uεF axis, u is the Poisson's ratio of the rod; the strain of R3 is ε3=εF axis, the strain of the working strain gauge of R4 is ε4=εF method=uεF axis, and the strain measuring instrument reading ε=ε1-ε2+ε3-ε4=2(εF axis-εF method)=2(1-u)εF axis; the εF axis and εF method are calculated from the strain measuring instrument reading ε.

[0011] A test method for measuring dynamic load by static strain load calibration, wherein four strain gauges are marked as R1, R2, R3 and R4 in the order of cross-section arrangement, wherein R1 and R3 are strain gauges pasted along the normal direction of the rod, and R2 and R4 are strain gauges pasted along the axial direction of the rod; four output wires are respectively feedback +, feedback -, excitation +, and excitation - wires; full-bridge strain measurement is adopted, and according to the principle of subtracting adjacent arms and adding opposite arms of the full-bridge circuit, the strain measurement errors caused by bending, temperature change and noise vibration are offset.

[0012] Furthermore, the strain of R2 is ε2=εF axis, the strain of R3 is ε3=εF method=uεF axis, u is the Poisson's ratio of the rod; the strain of R4 is ε4=εF axis, the strain of the working strain gauge of R1 is ε1=εF method=uεF axis, and the strain gauge reading ε=ε2-ε3+ε4-ε1=2(εF axis-εF method)=2(1-u)εF axis; the εF axis and εF method are calculated from the strain gauge reading ε.

[0013] The beneficial effects of the present invention are as follows:

[0014] The load calibration strain gauge arrangement disclosed in the present invention can effectively eliminate errors caused by various interferences in the dynamic test process, greatly improve the measurement accuracy, and can accurately measure the dynamic load through the strain-load static calibration method, so as to obtain good test results and achieve the test purpose. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram of the commonly used load calibration strain gauge arrangement.

[0016] Figure 2 This is a diagram of the arrangement of the load calibration strain gauges of the present invention. DETAILED DESCRIPTION

[0017] This section is an embodiment of the present invention, which is used to explain and illustrate the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships based on the orientations or positional relationships in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or case referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implying the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0019] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be interpreted in a broad sense, for example, it can be a fixed connection, a detachable connection or an integrated connection; it can be a mechanical connection or a point connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0020] Embodiment 1:

[0021] A test device for measuring dynamic load by static strain load calibration method comprises four strain gauges, which are respectively pasted on four centrally symmetrical points of the same cross section of a rod; wherein, every two strain gauges at mutually symmetrical points form a group, the strain gauges in the same group have the same pasting direction, and the strain gauges in different groups have different pasting directions, and the pasting directions are divided into the axial direction of the rod and the normal direction of the rod; the four strain gauges are connected in pairs to form a full-bridge circuit.

[0022] The utility model also comprises a strain measuring instrument and four output wires, wherein the four output wires are respectively connected to the strain measuring instrument and four strain gauges.

[0023] A test method for measuring dynamic load by static strain load calibration, wherein four strain gauges are marked as R1, R2, R3 and R4 in the order of cross-section arrangement, wherein R1 and R3 are strain gauges pasted along the axial direction of the rod, and R2 and R4 are strain gauges pasted along the normal direction of the rod; four output wires are respectively excitation +, excitation -, feedback +, and feedback - wires; full-bridge strain measurement is adopted, and according to the principle of subtracting adjacent arms and adding opposite arms of the full-bridge circuit, the strain measurement errors caused by bending, temperature change and noise vibration are offset.

[0024] During static calibration, a static load F is applied to the rod, the strain gauge reading ε is read, and then the εF axis and εF method are calculated; the εF axis is the axial strain value caused entirely by the load F, and the εF method is the normal strain value caused entirely by the load F.

[0025] Given a linearly changing static load F value, after multiple rounds of static calibration, the strain calibration coefficient K value is obtained. The strain calibration coefficient K is a binary function of the εF axis and the εF method.

[0026] The strain of R1 is ε1=εF axis, the strain of R2 is ε2=εF method=uεF axis, u is the Poisson's ratio of the rod; the strain of R3 is ε3=εF axis, the strain of the working strain gauge of R4 is ε4=εF method=uεF axis, the strain measuring instrument reading ε=ε1-ε2+ε3-ε4=2(εF axis-εF method)=2(1-u)εF axis; the εF axis and εF method are calculated from the strain measuring instrument reading ε.

[0027] A test method for measuring dynamic load by static strain load calibration, wherein four strain gauges are marked as R1, R2, R3 and R4 in the order of cross-section arrangement, wherein R1 and R3 are strain gauges pasted along the normal direction of the rod, and R2 and R4 are strain gauges pasted along the axial direction of the rod; four output wires are respectively feedback+, feedback-, excitation+, and excitation-wires; full-bridge strain measurement is adopted, and according to the principle of subtracting adjacent arms and adding opposite arms of the full-bridge circuit, the strain measurement errors caused by bending, temperature change and noise vibration are offset.

[0028] The strain of R2 is ε2=εF axis, the strain of R3 is ε3=εF method=uεF axis, u is the Poisson's ratio of the rod; the strain of R4 is ε4=εF axis, the strain of the working strain gauge of R1 is ε1=εF method=uεF axis, and the strain measuring instrument reading ε=ε2-ε3+ε4-ε1=2(εF axis-εF method)=2(1-u)εF axis; εF axis and εF method are calculated from the strain measuring instrument reading ε.

[0029] Embodiment 2:

[0030] The commonly used load calibration strain gauge arrangement is shown in the figure below. Figure 1As shown, a working strain gauge R1 is pasted on the rod, and the excitation end and feedback end of the R1 working gauge are connected to the strain gauge for measurement using a 1 / 4 bridge circuit. The strain of the R1 working strain gauge reading during static calibration is ε=ε1=εF (indicating the strain value completely caused by load F). Given a linear static load F value, the strain calibration coefficient K value will be obtained. During the dynamic test, the strain of the R1 working strain gauge is ε1=εF+εM+εt+εZ, where εM represents the strain caused by bending moment, εt represents the strain caused by temperature change, and εZ represents the strain caused by noise vibration. As shown above, the strain value measured by the working strain gauge R1 cannot fully reflect the strain caused by load F. If this measurement result is multiplied by the strain calibration coefficient K, the load value obtained will be very different from the theoretical value.

[0031] A static strain-load calibration of the present invention proposes a strain gauge arrangement method, that is, by evenly pasting four strain gauges at four symmetrical points on the cross section of the rod to form a full-bridge circuit, the strain changes caused by factors such as temperature, noise, and electromagnetic interference in the dynamic test environment can be eliminated, and the strain changes of the rod due to bending and torsion can be offset, so that the strain changes caused by the rod load can be accurately measured in the dynamic process, thereby achieving the purpose of accurately measuring the dynamic load.

[0032] The load calibration strain gauge arrangement of the present invention is shown in the figure Figure 2 As shown, four working strain gauges R1, R2, R3, and R4 are evenly pasted on a certain cross section of the rod. It should be noted that R1 and R3 are pasted along the axial direction of the rod, and R2 and R4 are pasted along the normal direction of the rod. The four working gauges are connected in pairs to form a full-bridge circuit. The connected circuit is connected to the strain gauge through four output wires (excitation +, excitation -, feedback +, feedback -) to perform full-bridge strain measurement. During static calibration, the strain of the R1 working strain gauge is ε1 = εF axis, the strain of the R2 working strain gauge is ε2 = εF method = uεF axis, and u is the Poisson's ratio of the rod. The strain of the R3 working strain gauge is ε3 = εF axis, and the strain of the R4 working strain gauge is ε4 = εF method = uεF axis. According to the principle of subtracting adjacent arms and adding opposite arms of the full-bridge circuit, the strain gauge reading ε = ε1-ε2+ε3-ε4 = 2(εF axis-εF method) = 2(1-u)εF axis. Given a linear static load F value, the strain calibration coefficient K value will be obtained. During the dynamic test, the strain of the R1 working strain gauge is ε1 = εF axis + εM + εt + εZ, the strain of the R2 working strain gauge is ε2 = εF method + εt + εZ, and the strain of the R3 working strain gauge is ε3 = εF axis - εM + εt + εZ

[0033] The strain of the R4 working strain gauge is ε4=εF method+εt+εZ. According to the principle of subtracting adjacent arms and adding opposite arms in the full-bridge circuit, the strain gauge reading ε=ε1-ε2+ε3-ε4=2(εF axis-εF method)=2(1-u)εF axis, and the measured value is completely consistent with the calibration value. It can be seen that the method of the present invention can completely measure the strain value caused by the load F, and can offset the errors caused by bending, temperature changes and noise vibration.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A test device for measuring dynamic load by static strain load calibration, characterized in that: It includes four strain gauges, which are respectively pasted on four centrally symmetrical points on the same cross section of the rod; wherein, every two strain gauges at mutually symmetrical points form a group, the strain gauges in the same group have the same pasting direction, and the strain gauges in different groups have different pasting directions, and the pasting directions are divided into along the axial direction of the rod and along the normal direction of the rod; the four strain gauges are connected in pairs to form a full-bridge circuit.

2. A test device for measuring dynamic load by static strain load calibration method according to claim 1, characterized in that: The utility model also comprises a strain measuring instrument and four output wires, wherein the four output wires are respectively connected to the strain measuring instrument and four strain gauges.

3. A test method for measuring dynamic load by static strain load calibration method, using a test device for measuring dynamic load by static strain load calibration method as claimed in claim 2, characterized in that: The four strain gauges are marked as R1, R2, R3 and R4 in the order of cross-section arrangement, where R1 and R3 are strain gauges pasted along the axial direction of the rod, and R2 and R4 are strain gauges pasted along the normal direction of the rod; the four output wires are excitation +, excitation -, feedback +, and feedback - wires respectively; the full-bridge strain measurement is adopted, and according to the principle of subtracting adjacent arms and adding opposite arms of the full-bridge circuit, the strain measurement errors caused by bending, temperature changes and noise vibration are offset.

4. According to the test method for measuring dynamic load by a static strain load calibration method as described in claim 3, during static calibration, a static load F is loaded on the rod, the strain gauge reading ε is read, and then the εF axis and εF method are calculated; the εF axis is the axial strain value completely caused by the load F, and the εF method is the normal strain value completely caused by the load F.

5. According to the test method for measuring dynamic load by a static strain load calibration method as described in claim 4, a linearly changing static load F value is given, and after multiple rounds of static calibration, a strain calibration coefficient K value is obtained, and the strain calibration coefficient K is a binary function of the εF axis and the εF method.

6. According to the test method for measuring dynamic load by a static strain load calibration method as described in claim 4, the strain of R1 is ε1=εF axis, the strain of R2 is ε2=εF method=uεF axis, u is the Poisson's ratio of the rod; the strain of R3 is ε3=εF axis, the strain of the working strain gauge of R4 is ε4=εF method=uεF axis, the strain measuring instrument reading ε=ε1-ε2+ε3-ε4=2(εF axis-εF method)=2(1-u)εF axis; the εF axis and εF method are calculated from the strain measuring instrument reading ε.

7. A test method for measuring dynamic load by static strain load calibration method, using the test device for measuring dynamic load by static strain load calibration method as claimed in claim 2, characterized in that: The four strain gauges are marked as R1, R2, R3 and R4 in the order of cross-section arrangement, where R1 and R3 are strain gauges pasted along the normal direction of the rod, and R2 and R4 are strain gauges pasted along the axial direction of the rod; the four output wires are feedback +, feedback -, excitation +, and excitation - wires respectively; the full-bridge strain measurement is adopted, and according to the principle of subtracting adjacent arms and adding opposite arms of the full-bridge circuit, the strain measurement errors caused by bending, temperature changes and noise vibration are offset.

8. The test method for measuring dynamic load by static strain load calibration according to claim 7, characterized in that: During static calibration, a static load F is applied to the rod, the strain gauge reading ε is read, and then the εF axis and εF method are calculated; the εF axis is the axial strain value caused entirely by the load F, and the εF method is the normal strain value caused entirely by the load F.

9. The test method for measuring dynamic load by static strain load calibration according to claim 8, characterized in that: Given a linearly changing static load F value, after multiple rounds of static calibration, the strain calibration coefficient K value is obtained. The strain calibration coefficient K is a binary function of the εF axis and the εF method.

10. The test method for measuring dynamic load by static strain load calibration according to claim 8, characterized in that: The strain of R2 is ε2=εF axis, the strain of R3 is ε3=εF method=uεF axis, u is the Poisson's ratio of the rod; the strain of R4 is ε4=εF axis, the strain of the working strain gauge of R1 is ε1=εF method=uεF axis, and the strain measuring instrument reading ε=ε2-ε3+ε4-ε1=2(εF axis-εF method)=2(1-u)εF axis; εF axis and εF method are calculated from the strain measuring instrument reading ε.

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