Method and device for improving the residual internal stress of a tube for a tail drive shaft of a helicopter

Abstract

This invention pertains to the field of aviation and relates to a method and apparatus for improving residual internal stress in helicopter tail drive shaft tubing. The method includes: processing a single tubing using an improved process: solution heat treatment → large deformation tension straightening → small diameter expansion → a final small deformation tension straightening to relax the residual stress caused by the diameter expansion.

Description

Technical Field

[0001] This invention belongs to the field of aviation and relates to a method and apparatus for improving the residual internal stress of helicopter tail drive shaft tubing. Background Technology

[0002] Currently, the domestically produced tail drive shaft tubing of this model has undergone static load and fatigue tests, and the test results are approximately 10% lower than those of imported tubing of the same model. Analysis indicates that the main cause of this problem is the influence of residual stress. The domestic production process for this model of tail drive shaft tubing involves solution treatment followed by diameter reduction, diameter expansion, and tension straightening. This processing method results in excessive localized residual stress on the tubing surface, thereby reducing the tubing's static load and fatigue strength. Summary of the Invention

[0003] Purpose of the invention: To provide a method and apparatus for improving the residual internal stress of helicopter tail drive shaft tubing, thereby improving the process, reducing the residual stress of the tubing, and increasing its static load and fatigue strength.

[0004] Technical solution:

[0005] In a first aspect, a method for improving residual internal stress in helicopter tail drive shaft tubing is provided, comprising:

[0006] Take a pipe and process it using the improved process:

[0007] Solution heat treatment → large deformation tension straightening → small diameter expansion → final small deformation tension straightening to relax the residual stress caused by diameter expansion.

[0008] The method further includes:

[0009] After processing, the internal stress ring is taken out and its internal stress magnitude and mechanical property values ​​are tested.

[0010] The method further includes:

[0011] To obtain the correspondence between the change in pipe diameter and the axial extension under load during tension straightening.

[0012] When the lead time is 2 hours and 20 minutes, the corresponding relationship fitted by the exponential function is as follows:

[0013] ;

[0014] Where x% represents the axial extension under load, and y% represents the change in pipe diameter.

[0015] When the aging time is 2 hours and 20 minutes, the corresponding relationship based on the linear fitting is as follows:

[0016] ;

[0017] Where x% represents the axial extension under load, and y% represents the change in pipe diameter.

[0018] When the lead time is 22 hours, the corresponding relationship based on linear fitting is as follows:

[0019] ;

[0020] Where x% represents the axial extension under load, and y% represents the change in pipe diameter.

[0021] Secondly, a device for improving residual internal stress in helicopter tail drive shaft tubing is provided, comprising:

[0022] The processing module is used to process a single pipe using an improved process: solution heat treatment → large deformation tension straightening → small diameter expansion → and finally, another small deformation tension straightening to relax the residual stress caused by the diameter expansion.

[0023] Thirdly, a computer-readable storage medium is provided, on which a computer program is stored, characterized in that the computer program implements the above-described method when executed by a processor.

[0024] Beneficial effects:

[0025] While ensuring that other properties and dimensional tolerances of the tail drive shaft tubing of this model are qualified, the residual internal stress of the tail drive shaft tubing of this model is reduced. Attached Figure Description

[0026] Figure 1 This is a diagram showing the dimensional changes (relationship between permanent deformation and loading deformation) during tension straightening in the implementation method.

[0027] Figure 2 This is a diagram showing the dimensional changes (relationship between pipe diameter change and axial extension) during tension straightening in the implementation method.

[0028] Figure 3 The illustration shows a variation of the implementation method. Detailed Implementation

[0029] Avoid using expansion and reduction simultaneously to prevent strength reduction and residual stress increase caused by the Bauschinger effect. Take two pipes from the same processing batch and the same furnace batch, as well as one imported pipe of the same specification, and process them separately according to the following technical solutions:

[0030] 1) Group A: Take a pipe and process it according to the conventional method: solution heat treatment → diameter reduction → diameter expansion → tension straightening. After processing, take the internal stress ring and test its internal stress and mechanical property values.

[0031] 2) Group B: Take one pipe and process it using the improved process: solution heat treatment → large deformation tension straightening (which can improve strength and relax quenching stress, causing a small change in the average diameter of the pipe) → small diameter expansion (to compensate for the diameter deterioration caused by tension straightening; the expansion mandrel should be slightly larger than the pipe after tension straightening) → finally, perform another small deformation tension straightening to relax the residual stress caused by the diameter expansion. After processing, take an internal stress ring and test its internal stress magnitude and mechanical property values.

[0032] 3) Group C: Take the internal stress ring of imported pipe of the same size and condition, and test its internal stress magnitude and mechanical property values.

[0033] Figure 1 The graph showing the dimensional changes (relationship between permanent deformation and loading deformation) during tension straightening in the implementation method was obtained after fitting a large amount of experimental data:

[0034] Delivery time: 2 hours 20 minutes

[0035] For those with a delivery time of 22 hours:

[0036] From an economic perspective, the analysis is based on an aging time of 2 hours and 20 minutes. To achieve 2% permanent deformation, the load elongation (x%) is 2.37%. Using a 2-meter scale, the load elongation is 2000 × 2.37% mm = 47.3 mm, leaving a remaining elongation of 40 mm.

[0037] Figure 2 The graph showing the dimensional changes (relationship between pipe diameter change and axial elongation) during tension straightening in the implementation method was obtained after fitting a large amount of experimental data:

[0038] For a timeframe of 2 hours and 20 minutes, the result is fitted using an exponential function:

[0039] Fitting to a straight line:

[0040] (This method has a slightly larger margin of error)

[0041] For a lead time of 22 hours, a linear fit is used:

[0042]

[0043] Example

[0044] 1.Group A:

[0045] 1) Reduction of diameter: The pipe is reduced in diameter as a whole using an outer mold with an inner diameter of 90.8mm;

[0046] 2) Expanding the diameter: The pipe is expanded as a whole using an expanding mandrel with an outer diameter of 87.2 mm;

[0047] 3) Tension straightening, with a loading elongation of 1.6% (residual 2.43%), results in a pipe diameter reduction of 0.63%. When the pipe diameter is 91mm, the corresponding diameter reduction is 0.57mm. The corresponding wall thickness reduction is 0.011mm.

[0048] 4) After processing, take a set of internal stress rings and test the internal stress values.

[0049] Group 2.B:

[0050] 1) Large deformation tension straightening, with a loading elongation of 1.6% (residual 1.28%), results in a pipe diameter reduction of 0.8%. When the pipe diameter is 91mm, the corresponding diameter reduction is 0.73mm. The corresponding wall thickness reduction is 0.016mm.

[0051] 2) The diameter expansion is 0.7%. Calculated based on 86.41. 86.41 * (1 - 0.7%) = 85.81 mm

[0052] 3) Low-tension straightening, with a loading elongation of 1% and a residual elongation of 0.72%. The diameter decreases by 0.57%. Based on a straightened diameter of 90.16mm (wall thickness 2.12mm), the original diameter was 90.67mm, and the wall thickness should be 2.13mm.

[0053] 4) After processing, take a set of internal stress rings and test the internal stress values.

[0054] Group 3.C:

[0055] Take an internal stress ring of imported pipe of the same size and condition, and test its internal stress for comparison.

[0056] in conclusion:

[0057] 1. The comparison of opening value data is shown in Table 1:

[0058] Table 1

[0059]

[0060] 2. Three sets of pipe mechanical property test samples were taken as comparisons, as shown in Table 2:

[0061] Table 2

[0062]

[0063] Conclusion: The improved processing method can reduce the residual stress of the pipe while ensuring the mechanical performance requirements.

Claims

1. A method for improving residual internal stress in helicopter tail drive shaft tubing, characterized in that, include: Take a pipe and process it using the improved process: Solution heat treatment → large deformation tension straightening → small diameter expansion → final small deformation tension straightening to relax the residual stress caused by diameter expansion. The method further includes: When obtaining the results of tension straightening, the relationship between the elongation permanent deformation and the loading deformation is as follows: For a timeframe of 2 hours and 20 minutes: b% = (0.94a - 0.2253)%, a ∈ [1.5, 3.5]; For a timeframe of 22 hours: b% = (a - 0.503)%, a ∈ [1.5, 3.5]; Where a is the loading deformation rate multiplied by 100, and b% is the elongation permanent deformation rate; When obtaining tension straightening, the relationship between the change in pipe diameter and the axial extension under load is as follows: When the lead time is 2 hours and 20 minutes, the corresponding relationship fitted by the exponential function is as follows: ； When the aging time is 2 hours and 20 minutes, the corresponding relationship based on the linear fitting is as follows: y%=(0.378x+0.172)%,x∈[1.69,3.07]; When the lead time is 22 hours, the corresponding relationship based on linear fitting is as follows: y%=(0.34x-0.133)%,x∈[0.98,3.00]; Where x is the axial elongation rate multiplied by 100, and y% is the pipe diameter change rate.

2. The method according to claim 1, characterized in that, The method further includes: After processing, the internal stress ring is taken out and its internal stress magnitude and mechanical property values ​​are tested.

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