Method for determining parameters of thin-wall structure ribs under cyclic high temperature action on aircraft

Abstract

The invention belongs to the technical field of design of thin-wall structure ribs on airplanes, and particularly relates to a method for determining parameters of thin-wall structure ribs under the action of circulating high temperature on an airplane, which comprises the following steps: step 1, determining a fatigue life index, a circulating high temperature action temperature spectrum and a DFRcutoff value of a thin-wall structure; 2, calculating the maximum allowable thermal stress of the thin-wall structure based on the fatigue life index and the DFRcut value of the thin-wall structure; step 3, preliminarily designing rib parameters; 4, constructing a finite element model of the thin-wall structure; 5, solving the temperature field distribution of the thin-wall structure by using the finite element model of the thin-wall structure; 6, solving a stress field of the thin-wall structure by taking the temperature field of the thin-wall structure as a boundary condition; 7, according to the stress field distribution of the thin-wall structure, the maximum allowable thermal stress of the thin-wall structure is compared, rib parameters are modified, and suitable rib parameters are obtained.

Description

Technical Field

[0001] The present application belongs to the technical field of thin-walled structural rib design on aircraft, and specifically relates to a method for determining parameters of thin-walled structural ribs on aircraft subjected to cyclic high temperature. Background Art

[0002] Thin-walled structures on aircraft that are mainly subjected to cyclic high temperatures, such as aircraft exhaust ducts, are mainly subjected to thermal stresses generated by temperature in addition to a small amount of mechanical loads. At this time, cyclic high temperature becomes an important source of fatigue for the structure.

[0003] Currently, when designing ribs on thin-walled structures on aircraft, the thermal stress caused by cyclic high temperature is usually ignored, or a rough estimate is made of the thermal stress caused by cyclic high temperature. For structures such as aircraft exhaust ducts, there are cases of under-design or over-design. In view of this, the present application is proposed. Summary of the invention

[0004] The purpose of the present application is to provide a method for determining parameters of thin-walled structural ribs on an aircraft that is subjected to cyclic high temperatures, so as to overcome or alleviate at least one aspect of the known technical deficiencies.

[0005] The technical solution of this application is:

[0006] A method for determining parameters of thin-walled structural ribs on an aircraft subjected to cyclic high temperature, comprising:

[0007] Step 1: Determine the fatigue life index, cyclic high temperature temperature spectrum, and DFR of thin-walled structures cutoff value;

[0008] Step 2: Fatigue life index and DFR based on thin-walled structures cutoff value, calculate the maximum allowable thermal stress of thin-walled structures;

[0009] Step 3: Preliminary design of reinforcement parameters;

[0010] Step 4: Construct a finite element model of a thin-walled structure;

[0011] Step 5: Using the thin-walled structure finite element model, solve the temperature field distribution of the thin-walled structure;

[0012] Step 6: Using the temperature field of the thin-walled structure as the boundary condition, solve the stress field of the thin-walled structure;

[0013] Step 7: According to the stress field distribution of the thin-walled structure, compare the maximum allowable thermal stress of the thin-walled structure, modify the rib parameters, and obtain the applicable rib parameters.

[0014] According to at least one embodiment of the present application, in the method for determining the rib parameters of a thin-walled structure subjected to cyclic high temperature on the above-mentioned aircraft, in step one, the fatigue life index is the number of times n that the thin-walled structure is required to be subjected to cyclic high temperature.

[0015] The cyclic high temperature temperature spectrum is the temperature change process of a thin-walled structure when it is subjected to cyclic high temperature.

[0016] DFR cutoff The value is the maximum fatigue rating allowed for thin-walled structures.

[0017] According to at least one embodiment of the present application, in the above-mentioned method for determining the parameters of thin-walled structural ribs on an aircraft subjected to cyclic high temperature, in step 1, DFR is obtained through experiments or corresponding manuals. cutoff value.

[0018] According to at least one embodiment of the present application, in the method for determining parameters of thin-walled structural ribs on an aircraft subjected to cyclic high temperature, step 2 is specifically as follows:

[0019]

[0020] in,

[0021] σ max is the maximum allowable thermal stress of thin-walled structures;

[0022] σ m0 is the stress-related characteristic parameter of thin-walled structural materials;

[0023] X is the characteristic parameter for thermal stress calculation of thin-walled structures and is a related function of fatigue life index.

[0024] According to at least one embodiment of the present application, in the above-mentioned method for determining the rib parameters of a thin-walled structure subjected to cyclic high temperature on an aircraft, in step 2, for an aluminum alloy thin-walled structure, σ m0 Take 310MPa, for titanium alloy thin-walled structure, σ m0 Take 620MPa, for thin-walled steel structures, σ m0 Take 930MPa.

[0025] According to at least one embodiment of the present application, in the above method for determining the parameters of the thin-walled structural ribs on the aircraft subjected to cyclic high temperature, in step 2, X=S (5-lgn) ;

[0026] in,

[0027] S is the fatigue-related characteristic parameter of thin-walled structural materials.

[0028] According to at least one embodiment of the present application, in the method for determining the rib parameters of thin-walled structures subjected to cyclic high temperatures on the above-mentioned aircraft, in step two, for aluminum alloy thin-walled structures, S is 2, for titanium alloy thin-walled structures, S is 2, and for steel thin-walled structures, S is 1.8.

[0029] According to at least one embodiment of the present application, in the method for determining parameters of thin-walled structural ribs subjected to cyclic high temperature on the above-mentioned aircraft, in step three, the parameters of the preliminary designed ribs include rib height, rib bottom width, and rib thickness.

[0030] According to at least one embodiment of the present application, in the method for determining the rib parameters of the thin-walled structure subjected to cyclic high temperature on the above-mentioned aircraft, in step three, for the titanium alloy thin-walled structure of the aircraft exhaust duct, the preliminary design of the rib parameters is rib height 40mm, rib bottom width 60mm, and rib thickness 4mm.

[0031] According to at least one embodiment of the present application, in the method for determining the rib parameters of a thin-walled structure subjected to cyclic high temperature on the above-mentioned aircraft, in step four, a finite element analysis software is used to take the preliminary designed rib parameters as a geometric model, select the temperature in the temperature spectrum as a boundary condition, and establish a finite element model of the thin-walled structure.

[0032] According to at least one embodiment of the present application, in the method for determining the rib parameters of a thin-walled structure subjected to cyclic high temperature on the above-mentioned aircraft, in step seven, if the maximum stress obtained according to the stress field distribution of the thin-walled structure is slightly less than the maximum allowable thermal stress, it is considered that the rib parameters meet the design requirements, and applicable rib parameters are derived; if not, the rib parameters are modified and steps four to seven are repeated.

[0033] According to at least one embodiment of the present application, in the method for determining the parameters of the thin-walled structure ribs subjected to cyclic high temperature on the above-mentioned aircraft, in step seven, the maximum stress obtained according to the stress field distribution of the thin-walled structure is slightly less than the maximum allowable thermal stress, which means that the maximum stress obtained according to the stress field distribution of the thin-walled structure is less than the maximum allowable thermal stress, and the difference with the maximum allowable thermal stress is within 10%.

[0034] According to at least one embodiment of the present application, in the method for determining the rib parameters of a thin-walled structure subjected to cyclic high temperature on the above-mentioned aircraft, in step seven, when the rib parameters are modified, if the maximum stress obtained according to the stress field distribution of the thin-walled structure is greater than the maximum allowable thermal stress, the rib height, rib thickness or rib bottom width is increased; otherwise, the rib height, rib thickness or rib bottom width is reduced.

[0035] This application has at least the following beneficial technical effects:

[0036] A method for determining the parameters of thin-walled structural ribs on aircraft subjected to cyclic high temperature is provided, which fully considers the thermal stress generated by cyclic high temperature, and can design the rib parameters in detail, thereby avoiding under-design or over-design, and can provide effective guidance for the parameter design of thin-walled structural ribs on aircraft subjected to cyclic high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of a method for determining parameters of thin-walled structural ribs on an aircraft subjected to cyclic high temperature provided by an embodiment of the present application;

[0038] Figure 2 is a schematic diagram of temperature field distribution of a thin-wall structure provided in an embodiment of the present application;

[0039] Figure 3 It is a schematic diagram of solving the stress field of a thin-walled structure for the first time provided by an embodiment of the present application;

[0040] Figure 4 This is a schematic diagram of solving the stress field of a thin-walled structure for the second time provided in an embodiment of the present application;

[0041] Figure 5 This is a schematic diagram of the third solution of the stress field of a thin-walled structure provided in an embodiment of the present application.

[0042] In order to better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. In addition, the drawings are only used for illustrative purposes and should not be construed as limitations on the present application. DETAILED DESCRIPTION

[0043] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present application will be described in further detail in detail and in detail with reference to 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.

[0044] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of this application shall have the usual meanings understood by those of ordinary skill in the art to which this application belongs. The words used in the description of this application to indicate orientation are only used to indicate relative directions or positional relationships. When the absolute position of the described object changes, its relative positional relationship may also change accordingly. The word "include" used in the description of this application indicates that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, but does not exclude other elements or objects.

[0045] A method for determining the parameters of thin-walled structural ribs on aircraft subjected to cyclic high temperature. Figure 1 shown.

[0046] Step 1: Determine the fatigue life index, cyclic high temperature temperature spectrum, and DFR of thin-walled structures cutoff value.

[0047] The fatigue life index, cyclic high temperature temperature spectrum, DFR of thin-walled structures can be determined according to specific usage scenarios. cutoff value.

[0048] The fatigue life index is the number of times n that the thin-walled structure is subjected to cyclic high temperature.

[0049] The cyclic high temperature temperature spectrum is the temperature change process of a thin-walled structure when it is subjected to cyclic high temperature.

[0050] DFR cutoff The value is the maximum fatigue rating allowed for thin-walled structures and can usually be obtained through tests or corresponding manuals.

[0051] Step 2: Fatigue life index and DFR based on thin-walled structures cutoff value, calculate the maximum allowable thermal stress of thin-walled structures.

[0052]

[0053] in,

[0054] σ max is the maximum allowable thermal stress of thin-walled structures;

[0055] σ m0 is the stress-related characteristic parameter of the thin-walled structure material, where for aluminum alloy thin-walled structures, σ m0 Usually 310MPa can be taken. For titanium alloy thin-walled structures, σ m0 Usually 620MPa can be taken. For thin-walled steel structures, σ m0 Usually 930MPa can be taken;

[0056] X is the characteristic parameter for thermal stress calculation of thin-walled structures and is a related function of fatigue life index.

[0057] X=S (5-lgn) ;

[0058] in,

[0059] S is a characteristic parameter related to fatigue of thin-walled structural materials. For aluminum alloy thin-walled structures, S is usually 2; for titanium alloy thin-walled structures, S is usually 2; and for steel thin-walled structures, S is usually 1.8.

[0060] Step 3: Preliminary design of reinforcement parameters.

[0061] According to the temperature spectrum of cyclic high temperature action and the maximum allowable thermal stress of thin-walled structure, the reinforcement parameters are preliminarily designed.

[0062] The parameters of the preliminary design of the ribs include rib height, rib bottom width, and rib thickness.

[0063] For the titanium alloy thin-walled structure of aircraft exhaust duct, the preliminary design parameters of the ribs are usually rib height 40mm, rib bottom width 60mm, and rib thickness 4mm.

[0064] Step 4: Construct a finite element model of the thin-walled structure.

[0065] The finite element model of the thin-walled structure is established by taking the preliminary designed rib parameters as the geometric model and selecting the temperature in the temperature spectrum as the boundary condition.

[0066] Specifically, ABAQUS finite element analysis software can be used to build a model of thin-walled structure.

[0067] Step 5: Use the thin-walled structure finite element model to solve the temperature field distribution of the thin-walled structure.

[0068] Step 6: Using the temperature field of the thin-walled structure as the boundary condition, solve the stress field of the thin-walled structure.

[0069] Step 7: According to the stress field distribution of the thin-walled structure, compare the maximum allowable thermal stress of the thin-walled structure, modify the rib parameters, and obtain the applicable rib parameters.

[0070] If the maximum stress obtained according to the stress field distribution of the thin-walled structure is slightly smaller than the maximum allowable thermal stress, and the difference between the specific designable stress and the maximum allowable thermal stress is within 10%, it is considered that the rib parameters meet the design requirements, and the applicable rib parameters are obtained to prevent under-design or over-design. If not, the rib parameters are modified and steps 4 to 7 are repeated.

[0071] If the maximum stress obtained according to the stress field distribution of the thin-walled structure is greater than the maximum allowable thermal stress, the rib height, rib thickness or rib bottom width should be increased.

[0072] If the maximum stress obtained according to the stress field distribution of the thin-walled structure is less than the maximum allowable thermal stress, and the difference with the maximum allowable thermal stress is less than 10%, then the rib height, rib thickness or rib bottom width is reduced.

[0073] In a specific example, the method for determining parameters of thin-walled structural ribs on an aircraft subjected to cyclic high temperature disclosed in the above embodiment is used to determine parameters of thin-walled structural ribs on an exhaust duct of a certain type of aircraft, and is implemented as follows.

[0074] S1. According to the specific usage scenario, the fatigue life index of the thin-walled structure is determined as the equivalent number of cyclic high temperature effects n=300000, the cyclic high temperature effect temperature spectrum is the temperature of the thin-walled structure subjected to cyclic high temperature effects changes from room temperature to 200°C, and DFRcutoff=90.

[0075] S2, the aircraft exhaust duct is a titanium alloy thin-walled structure, S = 2, σ m0 =620MPa, calculated X = 0.72, the maximum allowable thermal stress σ max =69.5NPa.

[0076] S3. The preliminary design parameters of the ribs are rib height 40mm, rib bottom width 60mm, and rib thickness 4mm.

[0077] S4. Select the temperature in the temperature spectrum as the boundary condition, take the preliminary designed rib parameters as the geometric model, and use ABAQUS finite element analysis software to establish a finite element model of the thin-walled structure.

[0078] S5. Solve the temperature field distribution of thin-walled structures, such as Figure 2 shown.

[0079] S6. Solve the stress field of the thin-walled structure for the first time, such as Figure 3 As shown, the maximum stress is 91.2MPa, which is greater than the maximum allowable thermal stress σ max =69.5NPa; adjust the rib height to 60mm, and solve the stress field of the thin-walled structure for the second time, such as Figure 4 As shown, the maximum stress is 78.12MPa, which is still greater than the maximum allowable thermal stress σ max =69.5NPa; adjust the rib height to 80mm, and solve the stress field of the thin-walled structure for the third time, such as Figure 5 As shown, the maximum stress is 63.4MPa, which meets the design requirements. The applicable rib parameters are 80mm high, 60mm bottom width and 4mm thick.

[0080] The method for determining the parameters of the ribs of the thin-walled structure subjected to cyclic high temperature on an aircraft disclosed in the above-mentioned embodiment fully considers the thermal stress generated by the cyclic high temperature, and can design the rib parameters in detail, thereby avoiding under-design or over-design situations, and can provide effective guidance for the parameter design of the ribs of the thin-walled structure subjected to cyclic high temperature on an aircraft.

[0081] So far, the technical solution of the present application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A method for determining parameters of thin-walled structural ribs on an aircraft subjected to cyclic high temperature, characterized in that: include: Step 1: Determine the fatigue life index, cyclic high temperature temperature spectrum, and DFR of thin-walled structures cutoff value; Step 2: Fatigue life index and DFR based on thin-walled structures cutoff value, calculate the maximum allowable thermal stress of thin-walled structures; Step 3: Preliminary design of reinforcement parameters; Step 4: Construct a finite element model of a thin-walled structure; Step 5: Using the thin-walled structure finite element model, solve the temperature field distribution of the thin-walled structure; Step 6: Using the temperature field of the thin-walled structure as the boundary condition, solve the stress field of the thin-walled structure; Step 7: According to the stress field distribution of the thin-walled structure, compare the maximum allowable thermal stress of the thin-walled structure, modify the rib parameters, and obtain the applicable rib parameters.

2. The method for determining parameters of thin-walled structural ribs subjected to cyclic high temperature on an aircraft according to claim 1, characterized in that: In step 1, the fatigue life index is the number of times n that the thin-walled structure is required to be subjected to cyclic high temperature. The cyclic high temperature temperature spectrum is the temperature change process of a thin-walled structure when it is subjected to cyclic high temperature. DFR cutoff The value is the maximum fatigue rating allowed for thin-walled structures.

3. The method for determining parameters of thin-walled structural ribs subjected to cyclic high temperature on an aircraft according to claim 2, characterized in that: In step 1, obtain DFR through experiments or relevant manuals cutoff value.

4. The method for determining parameters of thin-walled structural ribs subjected to cyclic high temperature on an aircraft according to claim 3, characterized in that: Step 2 is as follows: in, σ max is the maximum allowable thermal stress of thin-walled structures; σ m0 is the stress-related characteristic parameter of thin-walled structural materials; X is the characteristic parameter for thermal stress calculation of thin-walled structures and is a related function of fatigue life index.

5. The method for determining parameters of thin-walled structural ribs subjected to cyclic high temperature on an aircraft according to claim 4, characterized in that: In step 2, for aluminum alloy thin-walled structures, σ m0 Take 310MPa, for titanium alloy thin-walled structure, σ m0 Take 620MPa, for thin-walled steel structures, σ m0 Take 930MPa.

6. The method for determining the parameters of thin-walled structural ribs on an aircraft subjected to cyclic high temperature according to claim 5, characterized in that: In step 2, X = S (5-lgn) ; in, S is the fatigue-related characteristic parameter of thin-walled structural materials.

7. The method for determining parameters of thin-walled structural ribs on an aircraft subjected to cyclic high temperature according to claim 6, characterized in that: In step 2, for aluminum alloy thin-walled structures, S is 2, for titanium alloy thin-walled structures, S is 2, and for steel thin-walled structures, S is 1.

8.

8. The method for determining parameters of thin-walled structural ribs subjected to cyclic high temperature on an aircraft according to claim 7, characterized in that: In step three, the preliminary design parameters of the ribs include rib height, rib bottom width, and rib thickness.

9. The method for determining parameters of thin-walled structural ribs on an aircraft subjected to cyclic high temperature according to claim 8, characterized in that: In step three, for the titanium alloy thin-walled structure of the aircraft exhaust duct, the preliminary design parameters of the ribs are rib height 40mm, rib bottom width 60mm, and rib thickness 4mm.

10. The method for determining parameters of thin-walled structural ribs subjected to cyclic high temperature on an aircraft according to claim 9, characterized in that: In step 4, finite element analysis software is used to establish a finite element model of the thin-walled structure by taking the preliminary designed rib parameters as the geometric model and selecting the temperature in the temperature spectrum as the boundary condition.

11. The method for determining parameters of thin-walled structural ribs on an aircraft subjected to cyclic high temperature according to claim 10, characterized in that: In step seven, if the maximum stress obtained according to the stress field distribution of the thin-walled structure is slightly less than the maximum allowable thermal stress, it is considered that the rib parameters meet the design requirements, and the applicable rib parameters are obtained; if not, the rib parameters are modified and steps four to seven are repeated.

12. The method for determining parameters of thin-walled structural ribs subjected to cyclic high temperature on an aircraft according to claim 11, characterized in that: In step seven, the maximum stress obtained according to the stress field distribution of the thin-walled structure is slightly less than the maximum allowable thermal stress, which means that the maximum stress obtained according to the stress field distribution of the thin-walled structure is less than the maximum allowable thermal stress, and the difference with the maximum allowable thermal stress is within 10%.

13. The method for determining parameters of thin-walled structural ribs on an aircraft subjected to cyclic high temperature according to claim 12, characterized in that: In step seven, when modifying the rib parameters, if the maximum stress obtained according to the stress field distribution of the thin-walled structure is greater than the maximum allowable thermal stress, the rib height, rib thickness or rib bottom width is increased; otherwise, the rib height, rib thickness or rib bottom width is reduced.

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