A scaled-down design method for the impact dynamic response of aircraft stiffened plate structures
By keeping the relative stiffness constant in the design of aircraft stiffened plate structures and using the equivalent method of double-plate structures, the thickness of stiffened plates and the size of stiffeners can be flexibly adjusted, thus solving the problem of predicting the dynamic response of aircraft stiffened plate structures under impact loads and achieving efficient and accurate prediction of scaled-down models.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTHWESTERN POLYTECHNICAL UNIV
- Filing Date
- 2023-12-10
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies cannot effectively predict the dynamic response of aircraft stiffened plate structures under impact loads, and the thickness dimension in the scaled-down model design is difficult to scale according to the geometric similarity ratio, resulting in geometric distortion, which increases the difficulty and cost of testing.
By constraining the relative stiffness to remain constant, a scaled-down model of a stiffened plate is designed. The thickness of the panel, the size and material of the stiffeners are flexibly adjusted. The equivalent method of a double-plate structure is adopted to ensure the similar proportional relationship and predict the dynamic response of the prototype.
It shortened the testing cycle, reduced costs, improved the similarity between the scaled-down model and the prototype, and was able to accurately predict the dynamic response of the aircraft stiffening plate with errors within an acceptable engineering range.
Smart Images
Figure CN117786841B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of aircraft structure / strength testing technology, specifically relating to a scaled-down design method for the impact dynamic response of aircraft stiffened plate structures. Background Technology
[0002] Stiffened plate structures possess advantages such as light weight, high stiffness, and excellent mechanical properties, and are widely used in aircraft fuselage sections, wings, and cargo holds. Research on their dynamic response under impact loads is crucial. To objectively assess the impact safety performance of cabin structures, full-aircraft or fuselage section impact testing is an indispensable part of aircraft safety design. However, full-scale prototype impact testing of aircraft is costly, requires stringent testing conditions, and consumes enormous human and material resources, often making it difficult to conduct relevant experimental verification on full-scale prototypes. Designing small-scale models using similarity methods to replace full-scale structural testing and predict prototype test results is an effective approach that has gained popularity in recent years. Currently, publicly available similarity scaled-down model design methods have been applied to complex thin-plate structures, airships, trains, and other fields. These methods can design scaled-down models that satisfy similarity relationships based on similarity theory, enabling the prediction of the prototype's static response and dynamic characteristics. However, these publicly available similarity methods cannot effectively predict the static and dynamic characteristics of aircraft stiffened plate structures.
[0003] In practical engineering applications, some unavoidable difficulties arise. Aircraft stiffened plates are a type of thin-walled structure where the thickness is much smaller than the length and width. Considering the difficulties in processing and manufacturing, in scaled-down model design, the thickness dimension of the thin-walled structure cannot be scaled to the in-plane dimension using the same geometric similarity ratio, resulting in a geometric distortion model. Currently, some design methods have been provided for addressing the geometric distortion problem in scaled-down design of stiffened plate structures in the shipbuilding field. However, these methods mainly focus on designing scaled-down models to evaluate the buckling characteristics of stiffened plate structures. They cannot provide a systematic design method for the similarity relationships of physical quantities involved in the geometric dimensions, impact loads, and dynamic responses of aircraft stiffened plate structures under impact loads. Therefore, for aircraft stiffened plate structures, especially under impact loads, these publicly available similarity methods also cannot provide effective predictions.
[0004] Therefore, designing a scaled-down model of an aircraft stiffening plate structure using similarity theory, focusing on the difficulties in processing technology and manufacturing, conducting tests on the scaled-down model with geometric distortion, shortening the test cycle, improving the accuracy of the similarity relationship between the scaled-down model with geometric distortion and the full-size structure, and reducing the relative error of the scaled-down model prediction are problems that urgently need to be solved by those skilled in the art. Summary of the Invention
[0005] The technical problem to be solved:
[0006] To overcome the shortcomings of existing technologies, this invention provides a scaled-down design method for the dynamic impact response of stiffened plate structures in aircraft. For stiffened plate structures subjected to impact loads, a scaled-down model is designed based on similarity theory to reflect the actual dynamic response of the prototype, including impact force and displacement. This method ensures that the relative stiffness of the scaled-down model and the prototype are equal by limiting the conditions. During the design of the scaled-down model, the thickness of the stiffened plate panel, the cross-sectional dimensions of the stiffeners, the number of stiffeners, and the material of the stiffeners can be flexibly adjusted. This overcomes the practical difficulty of scaling up and processing test pieces based on geometric similarity for thin-walled structures like aircraft stiffened plates, while also shortening the test cycle and scale, and saving costs.
[0007] The technical solution of this invention is: a scaled-down design method for the dynamic impact response of an aircraft stiffened plate structure, the specific steps of which are as follows:
[0008] Define the impact load location and impact parameters of the aircraft stiffening plate, as well as the geometric parameters of the stiffening plate and its stiffeners;
[0009] Determine the dynamic yield stress of the stiffened plate and calculate its relative stiffness;
[0010] Design a stiffened plate equivalent structure that satisfies the requirement of constant relative stiffness, namely a double plate structure obtained by stacking two flat plates.
[0011] Define the basic geometric similarity ratio for the scaled-down model of the stiffened plate;
[0012] Determine the similarity ratio of the stiffened panel thickness;
[0013] Determine the similarity ratio of the width, height, and spacing between adjacent stiffeners;
[0014] Obtain the geometric dimensions of the scaled-down model of the stiffened plate;
[0015] Obtain the dynamic response of the scaled-down model of the stiffened plate;
[0016] Based on the similarity ratio of the dynamic response, the scaled-down model of the stiffened plate can be used to predict the dynamic response of the prototype by inverse calculation according to the similarity ratio.
[0017] A further technical solution of the present invention is: the upper surface of the aircraft stiffening plate is subjected to a concentrated mass impact load, the impact mass is G, and the impact velocity is V; the length and width of the stiffening plate are L and d respectively, the thickness of the plate is H, the height and width of the stiffening rib cross-section are h and b respectively, and the spacing between the stiffening ribs is a.
[0018] A further technical solution of the present invention is: the formula for calculating the relative stiffness K of the stiffening plate is:
[0019] A further technical solution of the present invention is: in the double-plate structure, the length, width, and thickness of the upper plate are consistent with the length L, width d, and thickness H of the stiffening plate, and the length and width of the lower plate are consistent with the length L and width d of the stiffening plate. The thickness of the lower plate is determined by the equivalent stiffening ribs, thus obtaining the equivalent thickness H of the double-plate structure. e for:
[0020]
[0021] A further technical solution of the present invention is: the basic geometric similarity ratios of the stiffened plate scaled-down model are as follows: stiffened plate length similarity ratio β L =L m / L p The thickness of the stiffened panel is similar in proportion to β. H =H m / H p The similarity ratio β of the stiffened plate width d =d m / d p β, the height similarity ratio of the reinforcing ribs h =h m / h p β, similarity ratio of stiffener width b =b m / b p The spacing between the reinforcing ribs is similar in proportion β. a =a m / a p Relative stiffness K and similarity ratio β K =K m / K p Equivalent thickness H e Similarity ratio similarity ratio of elastic modulus β E =E m / E p Time similarity ratio β t =t m / t p Density similarity ratio β ρ =ρ m / ρ p The similarity ratio of the stiffened plate mass β M =M m / M p Impact mass similarity ratio β G =G m / G p Impact velocity similarity ratio β V =V m / V p Displacement similarity ratio β δ =δ m / δp Impact force similarity ratio β F =F m / F p Kinetic energy similarity ratio Dynamic yield stress similarity ratio In this model, the subscript m represents a scaled-down model and the subscript p represents a prototype.
[0022] A further technical solution of the present invention is: the equivalent thickness H e The similarity ratio, the relative stiffness K similarity ratio, and the stiffened plate panel thickness similarity ratio satisfy the following conditions:
[0023]
[0024] Where, β K When K = 1, it can be guaranteed that the relative stiffness K of the scaled-down model is equal to the relative stiffness K of the prototype.
[0025] A further technical solution of the present invention is: the basic similarity ratio of the geometric dimensions between the scaled-down model of the stiffened plate and the prototype is β, where β L =β d =β; Due to the limitations of the scaling model's manufacturing process, the stiffened panel thickness of the scaling model is directly selected as the thinnest processable thickness, thereby determining the similarity ratio β of the stiffened panel thickness. H , and β H It is not equal to the basic similarity ratio β.
[0026] A further technical solution of the present invention is: in the geometric design of the scaled-down model of the stiffened plate, when determining the similarity ratio of the width, height and spacing of the stiffeners, it is necessary to ensure that β K =1, then Therefore, the length and width directions of the stiffened plate can be adjusted independently and flexibly to arrange stiffeners of different geometric dimensions and numbers;
[0027] Or, define in, To achieve a similar dynamic stress ratio for the stiffened panel,
[0028] To ensure the dynamic stress similarity ratio of the stiffeners, Therefore, the scaled-down design of the stiffened plate can be completed by adjusting the material of the stiffener in the scaled-down model.
[0029] A further technical solution of the present invention is: the calculation method for the dynamic response of the scaled-down model of the stiffened plate is as follows: first, obtain the impact mass G of the stiffened plate prototype. p Impact velocity V pThen, the impact mass G experienced by the scaled-down model of the stiffened plate is calculated based on the similarity ratio. m =G p β ρ β 2 β H Initial impact velocity (V) m )0=(V p )0β V Finally, the impact force F of the scaled-down model of the stiffened plate structure is calculated through numerical simulation or experiment. m Kinetic energy (E) K ) m Impact velocity V m and displacement δ m .
[0030] A further technical solution of the present invention is: the method by which the scaled-down model of the stiffened plate predicts the dynamic response of the prototype by back-calculation according to a similar ratio is as follows:
[0031] The similarity ratio of the dynamic response is determined as β. δ =β H ,
[0032] Impact force, kinetic energy, impact velocity, and displacement were calculated using a scaled-down model of stiffened plates.
[0033] Based on similarity theory, the corresponding impact force F′ of the stiffened plate prototype can be predicted by reverse calculation according to the following relationship. p Kinetic energy (E) K )′ p Impact velocity V′ p and displacement δ′ p The formula is as follows:
[0034] F′ p =F m / β F ;
[0035] (E K )′ p =(E K ) m / β EK ;
[0036] V′ p =V m / β V ;
[0037] δ′ p =δ m / β δ .
[0038] Beneficial effects
[0039] The beneficial effects of this invention are as follows: This invention proposes a scaled-down design method for the impact dynamic response of aircraft stiffened plate structures. Instead of using similarity ratios of other geometric dimensions to obtain the stiffened plate panel thickness, it directly selects the thinnest processable thickness for the scaled-down model based on existing manufacturing processes. This results in geometric distortion of the thickness. Furthermore, it ensures that the similarity ratio β of the stiffened plate's relative stiffness K is maintained. K Under the premise of equal to 1, the cross-sectional dimensions and number of stiffeners can be artificially adjusted, causing geometric distortion of the stiffener dimensions in the scaled-down model. This distortion is not smaller than the minimum machinable size using existing processing techniques, thus reducing the difficulty of fabricating the scaled-down model. Furthermore, while the geometric dimensions are distorted, the stiffener material in the scaled-down model can also be adjusted, not necessarily maintaining consistency with the prototype, providing multiple options for designing scaled-down models of stiffened plates. Based on the similarity ratio of dynamic responses, the scaled-down model designed in this invention can predict the dynamic responses of the prototype, including displacement, velocity, energy, and impact force, with the prediction relative error within an acceptable range for engineering applications, demonstrating good similarity.
[0040] This invention utilizes scaled-down model testing to replace prototype testing, shortening the testing cycle. Considering the processing technology and difficulty of scaled-down test pieces, the scaled-down model can undergo geometric distortion, flexibly adjusting the thickness of the stiffened plate panel, the cross-sectional dimensions, quantity, and material of the stiffeners. This provides useful guidance for the scaled-down design of aircraft stiffened plate structures subjected to impact loads and has broad engineering application prospects. Attached Figure Description
[0041] Figure 1 A flowchart of a scaled-down design method for the impact dynamic response of an aircraft stiffening plate structure provided by the present invention;
[0042] Figure 2 This is a schematic diagram of the stiffened plate structure provided by the present invention;
[0043] Figure 3 This is a two-dimensional dimensioning diagram of the stiffened plate structure provided by the present invention;
[0044] Figure 4 The figures show a comparison and analysis of the prototype simulation results of the stiffened plate and the prototype prediction results of the scaled-down model simulation results at a similar scale; (a) figure is the displacement-time curve of the center point of the stiffened plate, (b) figure is the velocity-time curve of the center point of the stiffened plate, (c) figure is the kinetic energy-time curve of the stiffened plate structure, and (d) figure is the impact force-time curve of the stiffened plate. Detailed Implementation
[0045] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.
[0046] In practical applications, aircraft stiffening plates are thin-walled structures whose thickness is much smaller than their length and width. Considering the difficulties in processing and manufacturing, in scaled-down model design, the thickness dimension of the thin-walled structure cannot be scaled to its in-plane dimensions using the same geometric similarity ratio, thus resulting in a geometrically distorted model. However, current scaled-down model methods cannot predict the impact loads experienced by aircraft stiffening plates. This invention provides a scaled-down design method for the dynamic impact response of aircraft stiffening plate structures, with the specific steps as follows:
[0047] Step 1: The upper surface of the stiffened plate of the aircraft is subjected to a concentrated mass impact load, the impact mass is G, the impact velocity is V; the length and width of the stiffened plate are L and d respectively, the thickness of the plate is H, the height and width of the stiffener cross-section are h and b respectively, and the spacing between the stiffeners is a.
[0048] Step 2: Determine the dynamic yield stress of the stiffened plate as σ. d The relative stiffness K of the stiffened plate is determined as follows:
[0049]
[0050] Step 3: While maintaining the relative stiffness, the stiffened plate is equivalent to a double-plate structure formed by directly stacking two plates. The length, width, and thickness of the upper plate are consistent with the length L, width d, and thickness H of the stiffened plate. The length and width of the lower plate are consistent with the length L and width d of the stiffened plate. The thickness of the lower plate is determined by the equivalent stiffener. The thickness of the upper and lower plates is added together to obtain the equivalent thickness H of the double-plate structure. e for:
[0051] Step 4: Subscript m represents the scaled-down model, and subscript p represents the prototype. Define the similarity ratio (the ratio of the values of the scaled-down model to the prototype) of each physical parameter between the scaled-down model and the prototype of the stiffened plate structure as follows: similarity ratio β of stiffened plate length L =L m / L p The thickness of the stiffened panel is similar in proportion to β. H =H m / H p The similarity ratio β of the stiffened plate width d =d m / d p β, the height similarity ratio of the reinforcing ribs h =h m / h p β, similarity ratio of stiffener width b =b m / b p The spacing between the reinforcing ribs is similar in proportion β. a =am / a p Relative stiffness K and similarity ratio β K =K m / K p Equivalent thickness H e Similarity ratio similarity ratio of elastic modulus β E =E m / E p Time similarity ratio β t =t m / t p Density similarity ratio β ρ =ρ m / ρ p The similarity ratio of the stiffened plate mass β M =M m / M p Impact mass similarity ratio β G =G m / G p Impact velocity similarity ratio β V =V m / V p Displacement similarity ratio β δ =δ m / δ p Impact force similarity ratio β F =F m / F p Kinetic energy similarity ratio Dynamic yield stress similarity ratio
[0052] Step 5: According to the equation analysis method, for the expression of the equivalent thickness in Step 3, in order to make the scaled-down model of the stiffened plate similar to the prototype, the equivalent thickness H is... e The similarity ratio, the relative stiffness K similarity ratio, and the stiffened plate panel thickness similarity ratio must satisfy the following conditions:
[0053]
[0054] Therefore, it is necessary to ensure β K =1, which means that the relative stiffness K of the scaled-down model is equal to the relative stiffness K of the prototype;
[0055] Step 6: Set the basic similarity ratio of the geometric dimensions between the scaled-down model of the stiffened plate and the prototype as β, where β L =β d =β, due to the limitations of the scaling model's manufacturing process, the stiffened panel thickness of the scaling model is directly selected as the thinnest processable thickness, thus determining the similarity ratio β of the stiffened panel thickness. H , and β HThe thickness of the stiffened plate panel is geometrically distorted because it is not equal to the basic similarity ratio β.
[0056] Step 7: Based on steps 2 and 5, we can ensure that β K When = 1, then we have β b β h and β a The β value can be flexibly selected based on the actual processing technology. b β h To ensure that the width and height dimensions of the stiffeners in the scaled-down model of the stiffened plate are convenient for machining the test specimen, and to flexibly select β... a Adjust the number and spacing of stiffeners in the scaled-down model of the stiffened plate to allow for the processing space of the scaled-down model test piece; thereby obtaining the geometric dimensions of the scaled-down model of the stiffened plate.
[0057] Step 8: Based on the similarity ratio of geometric dimensions between the scaled-down model and the prototype set in Step 6, calculate the impact mass G experienced by the scaled-down model of the stiffened plate. m =G p β ρ β 2 β H Initial impact velocity (V) m )0=(V p )0β V The impact force F of the scaled-down model of the stiffened plate structure was calculated through numerical simulation or experiment. m Kinetic energy (E) K ) m Impact velocity V m and displacement δ m ;
[0058] Step 9: The similarity ratio of the dynamic response is β δ =β H , Using the impact force, kinetic energy, impact velocity, and displacement calculated from the scaled-down model of the stiffened plate, and based on similarity theory, the corresponding impact force F′ of the original stiffened plate can be predicted by reverse calculation according to the following relationship. p Kinetic energy (E) K )′ p Impact velocity V′ p and displacement δ′ p :
[0059] F′ p =F m / β F ;
[0060] (E K )′ p =(EK ) m / β EK ;
[0061] V′ p =V m / β V ;
[0062] δ′ p =δ m / β δ .
[0063] Specifically, in step 7, while ensuring Under the condition that the height h, width b, and spacing a of the stiffeners are similar in proportion, they can be flexibly adjusted individually along the length and width directions in the plane of the stiffened plate, and stiffeners of different geometric dimensions and numbers can be arranged.
[0064] Specifically, the dynamic stress similarity ratio of the stiffened plate panel is defined. Dynamic stress similarity ratio of stiffeners In step 7, the following can be done: Further expanded to Therefore, the method of adjusting the stiffener material of the scaled-down model can be used to achieve the scaled-down design of the stiffened plate.
[0065] Therefore, this invention uses scaled-down model tests to replace prototype tests, shortening the test cycle. At the same time, considering the processing technology and difficulty of scaled-down test pieces, the scaled-down model can undergo geometric distortion, flexibly adjusting the thickness of the stiffened plate panel, the cross-sectional dimensions, quantity and material of the stiffeners. This provides useful guidance for the scaled-down design of aircraft stiffened plate structures subjected to impact loads and has broad engineering application prospects.
[0066] The above technical solution will be further explained below with reference to the accompanying drawings and examples:
[0067] Reference Figure 1 As shown in the figure, this invention discloses a scaled-down design method for the impact dynamic response of an aircraft stiffened plate structure, including the following specific steps:
[0068] Step 1: The upper surface of the aircraft stiffening plate is subjected to a concentrated mass impact load, with an impact mass of G and an impact velocity of V; the length and width of the stiffening plate are L and d, respectively, the thickness of the plate is H, the height and width of the stiffener cross-section are h and b, respectively, and the spacing between the stiffeners is a; In this embodiment, a stiffening plate of a certain type of aircraft wing is selected as the design prototype. The stiffening plate has L and d of 600 mm, H of 2 mm, h and b of 20 mm and 4 mm, respectively, and a of 150 mm.
[0069] Step 2: Determine the dynamic yield stress of the stiffened plate as σ. dThe relative stiffness K of the stiffened plate is determined as follows:
[0070]
[0071] Step 3: While maintaining the relative stiffness, the stiffened plate is equivalent to a double-plate structure formed by directly stacking two plates. The length, width, and thickness of the upper plate are consistent with the length L, width d, and thickness H of the stiffened plate. The length and width of the lower plate are consistent with the length L and width d of the stiffened plate. The thickness of the lower plate is determined by the equivalent stiffener. The thickness of the upper and lower plates is added together to obtain the equivalent thickness H of the double-plate structure. e for:
[0072]
[0073] Step 4: Subscript m represents the scaled-down model, and subscript p represents the prototype. Define the similarity ratio (the ratio of the values of the scaled-down model to the prototype) of each physical parameter between the scaled-down model and the prototype of the stiffened plate structure as follows: similarity ratio β of stiffened plate length L =L m / L p The thickness of the stiffened panel is similar in proportion to β. H =H m / H p The similarity ratio β of the stiffened plate width d =d m / d p β, the height similarity ratio of the reinforcing ribs h =h m / h p β, similarity ratio of stiffener width b =b m / b p The spacing between the reinforcing ribs is similar in proportion β. a =a m / a p Relative stiffness K and similarity ratio β K =K m / K p Equivalent thickness H e Similarity ratio similarity ratio of elastic modulus β E =E m / E p Time similarity ratio β t =t m / t p Density similarity ratio β ρ =ρ m / ρ p The similarity ratio of the stiffened plate mass β M =M m / M pImpact mass similarity ratio β G =G m / G p Impact velocity similarity ratio β V =V m / V p Displacement similarity ratio β δ =δ m / δ p Impact force similarity ratio β F =F m / F p Kinetic energy similarity ratio Dynamic yield stress similarity ratio
[0074] Step 5: According to the equation analysis method, for the expression of the equivalent thickness in Step 3, in order to make the scaled-down model of the stiffened plate similar to the prototype, the equivalent thickness H is... e The similarity ratio, the relative stiffness K similarity ratio, and the stiffened plate panel thickness similarity ratio must satisfy the following conditions:
[0075]
[0076] Therefore, it is necessary to ensure β K =1, which means that the relative stiffness K of the scaled-down model is equal to the relative stiffness K of the prototype;
[0077] Step 6: Set the basic similarity ratio of the geometric dimensions between the scaled-down model of the stiffened plate and the prototype as β, where β L =β d =β, due to the limitations of the scaling model's manufacturing process, the stiffened panel thickness of the scaling model is directly selected as the thinnest processable thickness, thus determining the similarity ratio β of the stiffened panel thickness. H , and β H The stiffened panel thickness is geometrically distorted because it is not equal to the basic similarity ratio β. In this embodiment, the basic similarity ratio β = 1 / 4 is selected, and the stiffened panel thickness similarity ratio β... H =1 / 2;
[0078] Step 7: Based on steps 2 and 5, we can ensure that β K When = 1, then we have β b β h and β a The β value can be flexibly selected based on the actual processing technology. b β h To ensure that the width and height dimensions of the stiffeners in the scaled-down model of the stiffened plate are convenient for machining the test specimen, and to flexibly select β... aAdjust the number and spacing of the stiffeners in the scaled-down model of the stiffened plate to allow sufficient processing space for fabricating the scaled-down model test piece; thereby obtaining the geometric dimensions of the scaled-down model of the stiffened plate; in this embodiment, β is selected. b =1,β h =1 / 4, β a =1 / 4; The geometric dimensions of the scaled-down model of the stiffened plate are 150mm for L and d, 1mm for H, 5mm and 4mm for h and b respectively, and 37.5mm for a;
[0079] Step 8: Based on the similarity ratio of geometric dimensions between the scaled-down model and the prototype set in Step 6, calculate the impact mass G experienced by the scaled-down model of the stiffened plate. m =G p β ρ β 2 β H Initial impact velocity (V) m )0=(V p )0β V In this embodiment, both the scaled-down model and prototype of the stiffened plate are made of 2024-T351 aluminum alloy commonly used in aircraft. The impact mass G experienced by the stiffened plate prototype is... p It weighs 16 kg and has an initial impact velocity (V). p The velocity is 0 = 6 m / s; therefore, the impact mass G experienced by the scaled-down model can be calculated. m The initial impact velocity is 0.5 kg (V). m The impact force F of the stiffened plate structure scaled-down model is calculated through numerical simulation or experiment, with a value of 12 m / s. m Kinetic energy (E) K ) m Impact velocity V m and displacement δ m ;
[0080] Step 9: The similarity ratio of the dynamic response is β δ =β H , The similarity relationship satisfied by the final dynamic response in this embodiment is β. δ =1 / 2, β F =1 / 4, β V =2; Using the impact force, kinetic energy, impact velocity, and displacement calculated from the scaled-down model of the stiffened plate, and based on similarity theory, the corresponding impact force F′ of the original stiffened plate is predicted by reverse calculation according to the following relationship. p Kinetic energy (E) K )′ p Impact velocity V′ p and displacement δ′ p :
[0081] F′ p =F m / β F ;
[0082]
[0083] V′ p =V m / β V ;
[0084] δ′ p =δ m / β δ .
[0085] Validation.
[0086] Numerical simulations were performed on the prototype and scaled-down model of the stiffened plate subjected to impact loads to obtain the four dynamic responses of the prototype and scaled-down model: impact force, kinetic energy, impact velocity, and displacement. Based on the scaled-down model design method, the similarity between the predicted results of the scaled-down model and the actual results of the prototype was analyzed. Figure 4 The results show that throughout the impact process, the center point displacement-time curve, center point velocity-time curve, kinetic energy-time curve, and impact force-time curve of the scaled-down model prediction and the actual prototype results all exhibit good consistency. Specifically, the relative errors between the peak impact force and displacement predicted by the scaled-down model and the actual peak impact force and displacement of the prototype are 1.56% and 2.15%, respectively, which are within the acceptable error range for engineering applications. These results indicate that the simulation results predicted by the scaled-down model of the stiffened plate are highly similar to the actual simulation results of the prototype. The dynamic response of the scaled-down model of the aircraft stiffened plate structure designed in this invention can effectively predict the dynamic response of the prototype, demonstrating good similarity.
[0087] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.
Claims
1. A scaled-down design method for the impact dynamic response of an aircraft stiffened plate structure, characterized in that... The specific steps are as follows: Define the impact load location and impact parameters of the aircraft stiffening plate, as well as the geometric parameters of the stiffening plate and its stiffeners; Determine the dynamic yield stress of the stiffened plate and calculate its relative stiffness; Design an equivalent stiffened plate structure that maintains constant relative stiffness, i.e., a double-plate structure obtained by stacking two flat plates; in the double-plate structure, the length, width, and thickness of the upper plate are the same as the length of the stiffened plate. L ,width d ,thickness H To maintain consistency, the length and width of its lower panel must match the length of the stiffening plate. L ,width d To maintain consistency, the thickness of the bottom panel is determined by the equivalent stiffeners, thus obtaining the equivalent thickness of the double-panel structure. for: in, a To ensure the spacing between the reinforcing ribs, b The width of the stiffener cross-section, h The height of the reinforcing rib cross-section, K The relative stiffness of the stiffened plate; Define the basic geometric similarity ratio for the scaled-down model of the stiffened plate; Determine the similarity ratio of the stiffened panel thickness; Determine the similarity ratio of the width, height, and spacing between adjacent stiffeners; Obtain the geometric dimensions of the scaled-down model of the stiffened plate; the design of the geometric dimensions of the scaled-down model of the stiffened plate, when determining the similarity ratio of the width, height and spacing of the stiffeners, must ensure relative stiffness. K Similarity ratio ,but ,in, To ensure that the spacing between the stiffeners is in a similar proportion, To ensure that the width of the reinforcing ribs is in a similar proportion, To ensure that the height of the reinforcing ribs is similar in proportion, The thickness of the stiffened panel is similar to that of the panel; therefore, the length and width directions of the stiffened panel can be adjusted independently and flexibly to arrange stiffeners of different geometric dimensions and numbers. Or, define ,in, To achieve a similar dynamic stress ratio for the stiffened panel, , To ensure the dynamic stress similarity ratio of the stiffeners, In this context, the subscript m represents the scaled-down model and the subscript p represents the prototype; therefore, the scaled-down design of the stiffened plate can be completed by adjusting the material of the stiffeners in the scaled-down model. Obtain the dynamic response of the scaled-down model of the stiffened plate; the calculation method for the dynamic response of the scaled-down model of the stiffened plate is as follows: First, obtain the impact mass of the stiffened plate prototype. Impact speed Then, the impact mass experienced by the scaled-down model of the stiffened plate is calculated based on the similarity ratio. Initial impact velocity ;in, The basic similarity ratio of the geometric dimensions between the scaled-down model of the stiffened plate and the prototype is given. For density similarity ratio, To establish a similar impact velocity ratio, the impact force of the scaled-down model of the stiffened plate structure was calculated using numerical simulation or experiment. ,kinetic energy Impact speed and displacement ; Based on the similarity ratio of the dynamic response, the scaled-down model of the stiffened plate can be used to predict the dynamic response of the prototype by inverse calculation according to the similarity ratio.
2. The scaled design method for the impact dynamic response of an aircraft stiffened plate structure according to claim 1, characterized in that: The upper surface of the aircraft stiffening plate is subjected to a concentrated impact load, the impact mass of which is... G Impact velocity is V The length and width of the stiffening plate are respectively L and d The thickness of the panel is H The height and width of the reinforcing rib cross-section are respectively h and b The spacing between the reinforcing ribs is a。 3. The scaled design method for the impact dynamic response of an aircraft stiffened plate structure according to claim 2, characterized in that: The relative stiffness of the stiffening plate K The calculation formula is: .
4. The scaled design method for the impact dynamic response of an aircraft stiffened plate structure according to claim 1, characterized in that: The basic geometric similarity ratios of the scaled-down models of the stiffened plate are as follows: stiffened plate length similarity ratio Similar proportions of stiffened panel thickness Similar proportions of stiffened plate width Similarity ratio of reinforcing rib height Similarity ratio of stiffener width The spacing between the reinforcing ribs is similar in proportion. Relative stiffness K Similarity ratio Equivalent thickness Similarity ratio Similarity ratio of elastic modulus similarity in time Density similarity ratio Similarity ratio of stiffened plate quality Similarity in impact mass Similarity ratio of impact velocity Displacement similarity ratio Similarity in impact force Kinetic energy similarity ratio Dynamic yield stress similarity ratio ; where the subscript m represents a scaled-down model and the subscript p represents a prototype.
5. The scaled design method for the impact dynamic response of an aircraft stiffened plate structure according to claim 4, characterized in that: The equivalent thickness Similar proportions, relative stiffness K The similarity ratio and the similarity ratio of stiffened panel thickness must meet the following conditions: ； in, This ensures the relative stiffness of the scaled-down model. K Relative stiffness of the prototype K equal.
6. The scaled design method for the impact dynamic response of an aircraft stiffened plate structure according to claim 5, characterized in that: The basic geometric similarity ratio between the scaled-down model of the stiffened plate and the prototype is as follows: ,in The thickness of the stiffened panel in the scaled-down model is directly selected from the thinnest processable thickness, thereby determining the similarity ratio of the stiffened panel thickness. .
7. The scaled design method for the impact dynamic response of an aircraft stiffened plate structure according to claim 6, characterized in that: The method for predicting the dynamic response of the prototype by back-calculating the stiffened plate scaled-down model according to a similar ratio is as follows: The similarity ratio of the dynamic response is determined as follows: , , , ; Impact force, kinetic energy, impact velocity, and displacement were calculated using a scaled-down model of stiffened plates. Based on similarity theory, the corresponding impact force of the stiffened plate prototype can be predicted by reverse calculation according to the following relationship. ,kinetic energy Impact speed and displacement The formula is as follows: ； ； ； 。