Method for releasing tension-compression strain coupling of torsion to helicopter rotor shaft

Abstract

The invention provides a method for releasing tension-compression strain coupling of torsion to a helicopter rotor shaft, which comprises the following steps of: pasting a strain gauge on one side of the helicopter rotor shaft and on the outer side of the rotor shaft along the direction of the rotor shaft, and uniformly pasting a half circle of strain gauges on the outer side of the rotor shaft according to each preset degree by taking the center of the strain gauge as a circle center; the method comprises the following steps: pasting a strain gauge on the outer side of a rotor shaft along the direction of the rotor shaft on the axial symmetry side of a helicopter rotor shaft, and uniformly pasting a half circle of strain gauges on the outer side of the rotor shaft according to each preset degree by taking the center of the strain gauge as a circle center; then loading is carried out in the pulling and pressing direction of the rotor shaft, and strain output of each strain gauge is measured; the strain output of each strain gauge is loaded and measured in the torsion direction of the rotor shaft; then two strain gauges are selected, the coupling factor of torsion to tension and compression strain is calculated in an exhaustion mode, the two strain gauges are selected, and the axial force test of the rotor shaft is completed. According to the invention, tension-compression strain coupling of torsion to the helicopter rotor shaft can be relieved; back-end test equipment does not need to be changed; and the test flight rotor shaft tension of the helicopter can be accurately measured.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter flight test, and in particular relates to a method for relieving the coupling of tension and compression strain of a helicopter rotor shaft by torsion. Background Art

[0002] Helicopter rotor shaft tension is a key parameter for helicopter flight test performance, quality analysis and rotor shaft life determination. The commonly used test method for rotor shaft tension is to obtain the tension value by measuring the tensile and compressive strain of the shaft. The tensile and compressive strain of the rotor shaft is measured by pasting two sets of T-type strain gauges on the shaft to form an electric bridge, such as Figure 1 shown.

[0003] During the helicopter test flight, the rotor shaft is not only subjected to large tension but also strong torque. The T-type strain gauge bridge has poor compensation ability for the coupled strain caused by torsion, which makes the measurement result not completely tensile and compressive strain, but contains a considerable proportion of torsional coupled strain, which ultimately leads to a large error in the measured rotor shaft tension value. Summary of the invention

[0004] In order to solve the problem of large errors in the rotor shaft tension value measured in the prior art, the present invention provides a method for releasing the coupling of torsion on the tension and compression strain of the helicopter rotor shaft, which can release the coupling of torsion on the tension and compression strain of the helicopter rotor shaft, so that the coupling degree of torsion on the tension and compression strain of the helicopter rotor shaft is no more than 5%; it is compatible with the original test equipment and does not need to change the back-end test equipment; it can accurately measure the rotor shaft tension of the helicopter test flight. The technical solution is as follows:

[0005] In a first aspect, a method for relieving the coupling of torsion strain on the tensile and compressive strains of a helicopter rotor shaft is provided, the method comprising:

[0006] Step 1: On one side of the helicopter rotor shaft, a strain gauge M1 is pasted on the outside of the rotor shaft along the direction of the rotor shaft. With the center of the strain gauge M1 as the center of the circle, a half circle of strain gauges is evenly pasted on the outside of the rotor shaft at each preset degree, wherein the first strain gauge and the last strain gauge are located on the same horizontal plane as M1;

[0007] Step 2: On the symmetrical side of the helicopter rotor axis, a strain gauge M2 is pasted on the outside of the rotor shaft along the direction of the rotor shaft. With the center of the strain gauge M2 as the center of the circle, a half circle of strain gauges is evenly pasted on the outside of the rotor shaft at each preset degree, wherein the first strain gauge and the last strain gauge are located on the same horizontal plane as M2;

[0008] Step 3: Load the rotor shaft in the tensile and compressive directions with a tensile force of F, and measure the strain output of each strain gauge;

[0009] Step 4: Load the rotor shaft in the torsion direction, the torque is b*F, and measure the strain output of each strain gauge, b is greater than 0 and less than 1;

[0010] Step 5: Select two strain gauges Mi and Mk from the half-circle strain gauges in step 1 and step 2, and exhaustively calculate the coupling factor α of torsion to tension and compression strain.

[0011] α= (Nε1+Nε2)-(Nε i +Nε k )

[0012] (Lε1+Lε2)-(Lε i +Lε k );

[0013] in,

[0014] Lε1 is the tensile and compressive loading response of strain gauge M1, and Lε2 is the tensile and compressive loading response of strain gauge M2.

[0015] Nε1 is the torsional loading response of strain gauge M1, Nε2 is the torsional loading response of strain gauge M2,

[0016] Lε i is the tensile and compressive loading response of strain gauge Mi, Lε k is the tensile and compressive loading response of strain gauge Mk,

[0017] Nε i is the torsional loading response of strain gauge Mi, Nε k is the torsional loading response of the strain gauge Mk;

[0018] Step 6: Select two strain gauges MX and MY according to the coupling factor α;

[0019] Step 7: Combine strain gauges M1, M2 and strain gauges MX, MY into a bridge circuit to complete the rotor shaft force test.

[0020] Optionally, step six specifically includes:

[0021] If the minimum value of the coupling factor α is less than or equal to the threshold, the two strain gauges corresponding to the minimum value are selected and the two strain gauges are counted as MX and MY.

[0022] Furthermore, the method further comprises:

[0023] If the minimum value of the influencing factor α is greater than the threshold, another strain gauge is pasted near the two strain gauges corresponding to the minimum value, and steps 3, 4, and 5 are repeated until strain gauges MX and MY that meet the requirement of less than or equal to 5% are found.

[0024] The preset degrees in step 1 and step 2 are equal and are 10°.

[0025] Among them, b in step 4 is 0.75.

[0026] Among them, the threshold is 5%.

[0027] Optionally, an axial force is applied to the rotor shaft in the tension and compression directions, and a torque is applied to the rotor shaft in the torsion direction, by means of a material testing machine.

[0028] Among them, in step seven, the strain gauges M1 and M2 are combined with the strain gauges MX and MY into a full-bridge circuit, the strain gauges M1 and M2 are the opposite arms, and the strain gauges MX and MY are the opposite arms.

[0029] The beneficial effects of the present invention are at least:

[0030] 1. Release the coupling of torsion on the tensile and compressive strain of the helicopter rotor shaft, so that the coupling degree of torsion on the tensile and compressive strain of the helicopter rotor shaft is no more than 5%;

[0031] 2. Compatible with the original test equipment, no need to change the back-end test equipment;

[0032] 3. Accurately measure the rotor shaft tension during helicopter test flight. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the bonding and bridge assembly of commonly used rotor shaft tension and compression strain gauges;

[0034] Figure 2 To decouple the rotor shaft strain gauge pasting position diagram;

[0035] Figure 3 Schematic diagram of the strain gauge bridge after decoupling. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below through specific implementation modes and drawings.

[0037] The present invention provides a method for relieving the coupling of tension and compression strain of a helicopter rotor shaft caused by torsion, comprising the following steps:

[0038] Step 1: On one side of the helicopter rotor shaft, a strain gauge M1 is pasted on the outside of the rotor shaft along the direction of the rotor shaft. With the center of the strain gauge M1 as the center of the circle, a half circle of strain gauges is evenly pasted on the outside of the rotor shaft at each preset degree, wherein the first strain gauge and the last strain gauge are located on the same horizontal plane as M1;

[0039] Step 2: On the symmetrical side of the helicopter rotor axis, a strain gauge M2 is pasted on the outside of the rotor shaft along the direction of the rotor shaft. With the center of the strain gauge M2 as the center of the circle, a half circle of strain gauges is evenly pasted on the outside of the rotor shaft at each preset degree, wherein the first strain gauge and the last strain gauge are located on the same horizontal plane as M2;

[0040] Step 3: Load the rotor shaft in the tensile and compressive directions with a tensile force of F, and measure the strain output of each strain gauge;

[0041] Step 4: Load the rotor shaft in the torsion direction, the torque is b*F, and measure the strain output of each strain gauge, b is greater than 0 and less than 1;

[0042] Step 5: Select two strain gauges Mi and Mk from the half-circle strain gauges in step 1 and step 2, and exhaustively calculate the coupling factor α of torsion to tension and compression strain.

[0043] α= (Nε1+Nε2)-(Nε i +Nε k )

[0044] (Lε1+Lε2)-(Lε i +Lε k );

[0045] in,

[0046] Lε1 is the tensile and compressive loading response of strain gauge M1, and Lε2 is the tensile and compressive loading response of strain gauge M2.

[0047] Nε1 is the torsional loading response of strain gauge M1, Nε2 is the torsional loading response of strain gauge M2,

[0048] Lε i is the tensile and compressive loading response of strain gauge Mi, Lε k is the tensile and compressive loading response of strain gauge Mk,

[0049] Nε i is the torsional loading response of strain gauge Mi, Nε k is the torsional loading response of the strain gauge Mk;

[0050] Step 6: Select two strain gauges MX and MY according to the coupling factor α;

[0051] Step 7: Combine strain gauges M1, M2 and strain gauges MX, MY into a bridge circuit to complete the rotor shaft force test.

[0052] In one embodiment, the specific implementation process of the present invention is as follows:

[0053] 1. If Figure 2 As shown, on one side (0°) and the symmetrical side (180°) of the helicopter rotor shaft, a strain gauge M1 and M2 are respectively pasted along the rotor shaft direction, and a group of strain gauges are evenly pasted every 10° in the horizontal direction, namely M3, M4······M21, M22, M23······M40;

[0054] 2. Load the rotor shaft in the tensile and compressive directions with a tensile force of F (N). Measure the strain output of each strain gauge, which are Lε1, Lε2,...,Lε 40 ;

[0055] 3. Load the rotor shaft in the torsion direction with a torque of 0.75*F (Nm). Measure the strain output of each strain gauge, which are Nε1, Nε2,...,Nε 40 ;

[0056] In this embodiment, the material testing machine is used to apply axial force loading in the tension and compression directions of the rotor shaft, and to apply torque loading in the torsion direction of the rotor shaft.

[0057] 4. From M3 to M40, select two strain gauges Mi and Mk, and exhaustively calculate the coupling factor α of torsion to tension and compression strain.

[0058] α= (Nε1+Nε2)-(Nε i +Nε k )

[0059] (Lε1+Lε2)-(Lε i +Lε k );

[0060] 5. The minimum value of the coupling factor α is less than or equal to 5%. Select the two strain gauges corresponding to the minimum value. The two strain gauges are counted as MX and MY.

[0061] MX and MY can be two of M3, M4...M21, or two of M22, M23...M40. It can also be that MX is one of M3, M4...M21, and MY is one of M22, M23...M40. The embodiment of the present invention is not limited to this.

[0062] In this embodiment, Lε3 and Nε3 of M3 and Lε3 of M25 are 25 、Nε 25 , substitute into the formula

[0063]

[0064] The coupling factor α is the smallest and is less than or equal to 5%, so MX and MY are selected as M3 and M25.

[0065] 6. Strain gauges M1, M2 and strain gauges M3, M25 form a bridge circuit, such as Figure 3 As shown, the tensile and compressive strain test of the rotor shaft is completed. The strain gauges M1, M2 and the strain gauges M3, M25 are combined into a full bridge circuit, the strain gauges M1, M2 are the opposite arm, and the strain gauges M3, M25 are the opposite arm.

[0066] The process of rotor shaft force test is as follows: the strain gauge bridge used for rotor shaft tension and pressure test is determined by this method, and the corresponding relationship between the strain bridge output and the rotor shaft force is obtained by calibration. Then, a rotor load test device is installed on the main rotor system, and the output voltage signal of the rotor shaft strain bridge is collected and recorded in the helicopter flight state, and the tensile and compressive loads on the rotor shaft in the helicopter flight state are calculated by the calibration coefficient.

[0067] In another embodiment, the specific implementation process of the present invention is as follows:

[0068] 1. On one side (0°) and the symmetrical side (180°) of the helicopter rotor shaft, a strain gauge M1 and M2 are respectively pasted along the rotor shaft direction. In the horizontal direction, a group of strain gauges are evenly pasted every 10°, namely M3, M4······M21, M22, M23······M40;

[0069] 2. The rotor shaft is loaded in the tension and compression directions with a tension of F (N). The strain output of each strain gauge is measured, which are Lε1, Lε2,...,Lε 40 ;

[0070] 3. Load the rotor shaft in the torsion direction with a torque of 0.75*F (Nm). Measure the strain output of each strain gauge, which are Nε1, Nε2,...Nε 40 ;

[0071] 4. From M3 to M40, select two strain gauges Mi and Mk, and exhaustively calculate the coupling factor α of torsion to tension and compression strain.

[0072]

[0073] 5. If the minimum value of the influencing factor α is greater than 5%, paste another strain gauge near the two strain gauges corresponding to the minimum value, and repeat steps 3, 4, and 5 until strain gauges MX and MY that meet the requirement of less than or equal to 5% are found.

[0074] In this embodiment, Lε5 and Nε5 of M5 and Lε5 of M39 are 39 、Nε 39 , substitute into the formula

[0075]

[0076] The coupling factor α is the smallest and is greater than 5%, so strain gauges are pasted on the left and right sides of M5 and M39, one strain gauge between M5 and M4, one strain gauge between M5 and M6, one strain gauge between M39 and M38, and one strain gauge between M39 and M40.

[0077] Repeat steps 3, 4, and 5 until strain gauges MX and MY that meet the requirement of less than or equal to 5% are found.

[0078] 6. Combine the strain gauges M1, M2 and the strain gauges MX, MY into a bridge circuit to complete the tensile and compressive strain test of the rotor shaft. Combine the strain gauges M1, M2 and the strain gauges MX, MY into a full bridge circuit, with the strain gauges M1 and M2 as the opposite arm and the strain gauges MX and MY as the opposite arm.

[0079] The above only expresses the implementation mode of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. In addition, the parts not detailed in the present invention are all conventional technologies.

Claims

1. A method for relieving the coupling of tension and compression strain of a helicopter rotor shaft caused by torsion, characterized in that: The method comprises: Step 1: On one side of the helicopter rotor shaft, a strain gauge M1 is pasted on the outside of the rotor shaft along the direction of the rotor shaft. With the center of the strain gauge M1 as the center of the circle, a half circle of strain gauges is evenly pasted on the outside of the rotor shaft at each preset degree, wherein the first strain gauge and the last strain gauge are located on the same horizontal plane as M1; Step 2: On the symmetrical side of the helicopter rotor axis, a strain gauge M2 is pasted on the outside of the rotor shaft along the direction of the rotor shaft. With the center of the strain gauge M2 as the center of the circle, a half circle of strain gauges is evenly pasted on the outside of the rotor shaft at each preset degree, wherein the first strain gauge and the last strain gauge are located on the same horizontal plane as M2; Step 3: Load the rotor shaft in the tensile and compressive directions with a tensile force of F, and measure the strain output of each strain gauge; Step 4: Load the rotor shaft in the torsion direction, with a torque of b*F, and measure the strain output of each strain gauge, where b is greater than 0 and less than 1; Step 5. Select two strain gauges Mi and Mk from the half-circle strain gauges in step 1 and step 2, and exhaustively calculate the coupling factor α of torsion to tension and compression strain. α＝ (Nε1+Nε2)-(Nε i +Nε k ) (Lε1+Lε2)-(Lε i +Lε k ); in, Lε1 is the tensile and compressive loading response of strain gauge M1, and Lε2 is the tensile and compressive loading response of strain gauge M2. Nε1 is the torsional loading response of strain gauge M1, Nε2 is the torsional loading response of strain gauge M2, Lε i is the tensile and compressive loading response of strain gauge Mi, Lε k is the tensile and compressive loading response of strain gauge Mk, Nε i is the torsional loading response of strain gauge Mi, Nε k is the torsional loading response of the strain gauge Mk; Step 6: Select two strain gauges MX and MY according to the coupling factor α; Step 7: Combine strain gauges M1, M2 and strain gauges MX, MY into a bridge circuit to complete the rotor shaft force test.

2. The method according to claim 1, characterized in that Step 6 specifically includes: If the minimum value of the coupling factor α is less than or equal to the threshold, the two strain gauges corresponding to the minimum value are selected and the two strain gauges are counted as MX and MY.

3. The method according to claim 1, characterized in that The method further comprises: If the minimum value of the influencing factor α is greater than the threshold, another strain gauge is pasted near the two strain gauges corresponding to the minimum value, and steps 3, 4, and 5 are repeated until strain gauges MX and MY that meet the requirement of less than or equal to 5% are found.

4. The method according to claim 1, characterized in that: The preset degrees in step 1 and step 2 are equal and are 10°.

5. The method according to claim 1, characterized in that The value b in step 4 is 0.

75.

6. The method according to claim 2, characterized in that The threshold is 5%.

7. The method according to claim 1, characterized in that The material testing machine is used to apply axial force loading in the tensile and compressive directions of the rotor shaft, and torque loading in the torsion direction of the rotor shaft.

8. The method according to claim 1, characterized in that In step seven, the strain gauges M1, M2 and the strain gauges MX, MY are combined into a full-bridge circuit, wherein the strain gauges M1, M2 are opposite arms and the strain gauges MX, MY are opposite arms.

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