An APU mockup and a method of designing the same

Abstract

The application provides an APU dummy and a design method thereof. The front right and left column bodies, the front left column body and the rear column body, and the front right column body and the rear column body are connected through a front horizontal rod, an outer side horizontal rod and an inner side horizontal rod respectively, a triangular joint is arranged above the triangle, the triangular joint is connected with a heading rod, the heading rod is connected with the rear column body, the front right column body and the front left column body through a rear inclined support rod, a front inner inclined support rod and a front outer inclined support rod respectively, the front end and the rear end of the heading rod are respectively provided with a heading rod front joint and a heading rod rear joint, the bottom ends of the front left column body, the front right column body and the rear column body are respectively provided with a front left column body connecting joint, a front right column body connecting joint and a rear column body connecting joint which are the same as the interface structure and the position of the APU real part, and the triangular joint is located at the gravity center position of the APU real part. The APU dummy has the characteristics of simple connecting structure, unique connecting process, wide channel for obtaining manufacturing materials, low manufacturing cost, convenient preservation and management, and convenience for static loading and measurement.

Description

Technical Field

[0001] This invention belongs to the field of static testing technology for large aircraft structures, specifically relating to an APU dummy and its design method. Background Technology

[0002] An APU (Auxiliary Power Unit) is an auxiliary power unit for an aircraft. When the main power source fails, the auxiliary power unit takes over to provide electrical power to the aircraft. The APU of a certain large amphibious aircraft is installed on the external fuselage panel. The APU is large (1620mm long, 600mm wide, 600mm high) and heavy (approximately 250kg) (see...). Figure 1 The APU (Air Processing Unit) is located in a critical part of the aircraft. Deformation or damage to the APU mounting bracket will inevitably have a serious impact on the aircraft structure and APU components, potentially even leading to a flight accident. Therefore, it is necessary to conduct static tests on the APU mounting bracket to assess its static strength requirements. However, the APU contains numerous components and related conduits and wires, which are complex and interconnected with other components, making them bulky, heavy, and expensive. Using a real APU for testing would not only lack reliable connectors to meet the actuator loading requirements, but damage to the real APU would also result in significant economic losses. Therefore, a dummy APU must be designed to perform the static test in place of the real component.

[0003] Currently, there is limited data on static testing of APU dummy components on aircraft, and most of the data pertains to assembled structures. This necessitates lengthy processes for component inspection, assembly, and final assembly. After assembly, the components require performance checks and adjustments, further extending the testing cycle. Similarly, after the static test, extensive disassembly and corrosion protection of components are required. Furthermore, the predominantly assembled structure necessitates a greater number of parts, significantly increasing the costs of component processing, corrosion protection, and assembly, while also adding to the complexity of the manufacturing process. Summary of the Invention

[0004] The purpose of this invention is to provide an APU dummy and its design method. The APU dummy of this invention features a simple connection structure, a unique connection process, widely available manufacturing materials, low manufacturing cost, convenient storage and management, and ease of static loading and measurement.

[0005] Technical Solution. An APU dummy component includes a front right column, a front left column, and a rear column arranged at the three vertices of a triangle; the front right and left columns are connected to each other, the front left and rear columns are connected to each other, and the front right and rear columns are connected to each other via a front horizontal bar, an outer horizontal bar, and an inner horizontal bar, respectively; a triangular joint is provided at the top of the triangle, and the triangular joint is connected to a yaw bar; the yaw bar is connected to the rear column, the front right column, and the front left column via a rear diagonal brace, a front inner diagonal brace, and a front outer diagonal brace, respectively; the front and rear ends of the yaw bar are respectively provided with a yaw bar front joint and a yaw bar rear joint; the bottom ends of the front left column, the front right column, and the rear column are respectively provided with a front left column connection interface, a front right column connection interface, and a rear column connection interface with the same interface structure and position as the actual APU component; the triangular joint is located at the center of gravity of the actual APU component.

[0006] In the aforementioned APU dummy used for static load testing of the APU, the front right column, front left column, rear column, and yaw bar are all solid structures.

[0007] In the aforementioned APU dummy for static load testing, the front horizontal bar, outer horizontal bar, inner horizontal bar, rear diagonal brace, front inner diagonal brace, and front outer diagonal brace are all hollow bars.

[0008] In the aforementioned APU dummy for static load testing, the connections of the front horizontal bar, outer horizontal bar, inner horizontal bar, rear diagonal brace, front inner diagonal brace, and front outer diagonal brace are all welded and fixed.

[0009] A design method for an APU dummy component as described above: Calculate the center of gravity of the APU real component, and place the triangular joint in the APU dummy component at the center of gravity of the APU real component; construct finite element models of the APU real component and the APU dummy component respectively, and perform finite element analysis: apply yaw load, lateral load, and vertical load to the center of gravity of the APU real component and the triangular joint of the APU dummy component respectively, and compare the consistency of the deformation displacement of the finite element models of the APU real component and the dummy component with the load distribution at each interface under each load, to ensure that the deformation displacement deviation and load distribution deviation of the finite element models of the APU real component and the dummy component are within the design range.

[0010] In the aforementioned design method for the APU dummy component, the calculation method for the center of gravity of the actual APU component is as follows: Based on cross-sectional similarity, the APU prototype is divided into seven segments along the flight direction, namely: L1~L7; Calculate the weight of each segment separately. M i and the corresponding centroid coordinates ( X i , Y i , Z i ); Calculate the center of gravity of the APU component using the following formula (X 0, Y 0, Z 0):

[0011]

[0012]

[0013] In the formula, M i For APU genuine parts i Segment weight, M This is the total weight of the APU component.

[0014] In the aforementioned design method for the APU dummy used in the static load test of the APU, the construction and analysis of the finite element models of the real APU and the APU dummy are based on the software HyperMesh / HyperWorks, and the steps are as follows: Step 1: Obtain the cross-sectional characteristic data of each segment of the APU component at the center of gravity; Step 2: Build a full-fledged APU model and input the full-fledged cross-sectional characteristic data shown in Step 1 into the finite element software HyperMesh. Step 3: Based on the APU prototype model, establish the interface models, set the constraints of the interface parts, and complete the finite element model construction of the APU prototype. Step 4, at the center of gravity of the APU component ( X 0, Y 0, Z Apply loads along the heading, side, and vertical directions at point 0 to obtain the deformation displacements of the APU component in the heading, side, and vertical directions and the load distribution of each interface. Step 5: Input the finite element model parameters of the APU dummy into the finite element software HyperMesh, and set the same interface model and interface constraints as in Step 3 to complete the finite element model construction of the APU dummy. Step 6: Apply the same load as in step 4 to the triangular joint of the APU dummy to obtain the yaw, lateral, and vertical deformation displacements of the APU dummy and the load distribution of each interface. Step 7: Compare the results obtained in steps 4 and 6 to ensure that the deformation deviation and load distribution deviation between the real and dummy APUs are within the design range.

[0015] In the aforementioned design method for APU dummy components, the cross-sectional characteristic data at the center of gravity of each segment in step 1 are shown in the table below:

[0016] In the aforementioned design method for APU dummy components, step 5 includes the following parameters for the finite element model of the APU dummy component: the diameter and thickness of the front horizontal bar, outer horizontal bar, inner horizontal bar, rear diagonal brace, front inner diagonal brace, and front outer diagonal brace, as well as the weld thickness and weld area.

[0017] In the aforementioned design method for the APU dummy, in step 7, when the deviation exceeds the design range, the parameters of the APU dummy finite element model are adjusted and iterative analysis continues until the deviation is within the design range.

[0018] Advantages of this invention: This invention solves the problem that large-volume, heavy, and complex internal connection structures of APU dummy components are inconvenient to directly apply to static testing of components. It can provide a structural solution for static testing dummy components for similar components in aviation, aerospace and other application fields.

[0019] The APU dummy component of this invention has a simple structure; each connector has a regular shape, is easy to process and manufacture; has low processing cost; has a wide range of material acquisition channels; saves production, testing and subsequent storage and management costs; and is convenient for static loading and measurement.

[0020] This invention provides a design method for dummy components. This design method solves the problem that conventional engineering calculation methods have difficulty in addressing the structural stiffness matching between real and dummy components with complex cross-sectional features. This design method can provide a certain reference for the design of other static test dummy components. Attached Figure Description

[0021] Figure 1 This is a diagram showing the actual APU component and its installation. Figure 2 This is an isometric drawing of the APU dummy component of the present invention; Figure 3 This is a front view of the APU dummy component of the present invention; Figure 4 This is a top view of the APU dummy component of the present invention; Figure 5 This is a side view of the APU dummy component of the present invention; Figure 6 A schematic diagram of the segmentation of an APU component; Figure 7 A schematic diagram for inputting cross-sectional characteristic data of an APU real component; Figure 8 This is a picture of a fake APU component. Figure 9 This is a schematic diagram of the application of an APU dummy component. Detailed Implementation

[0022] To better understand the function and purpose of the present invention, and not to be regarded as a limiting solution, the following detailed description of the embodiments of the present invention is given based on the accompanying drawings.

[0023] Example 1. An APU dummy component, see [link to example]. Figures 2-5 The triangle includes a front right column 01, a front left column 02, and a rear column 03 located at the three vertices of the triangle. The front right and left columns, the front left column 02 and the rear column 03, and the front right column 01 and the rear column 03 are connected by a front horizontal bar 04, an outer horizontal bar 05, and an inner horizontal bar 06, respectively. A triangular joint 13 is provided above the triangle, and the triangular joint 13 is connected to a heading rod 08. The heading rod 08 is connected by a rear diagonal brace 07, a front inner diagonal brace 09, and a front outer diagonal brace 06. The diagonal brace 10 is connected to the rear column 03, the front right column 01, and the front left column 02; the yaw rod 08 has a front yaw rod connector 12 and a rear yaw rod connector 11 at its front and rear ends, respectively; the bottom ends of the front left column 02, the front right column 01, and the rear column 03 are respectively equipped with a front left column connection 14, a front right column connection 15, and a rear column connection interface 16, which correspond to the interface structure and position of the APU prototype; the triangular connector 13 is located at the center of gravity of the APU prototype. To achieve the accuracy and precision of the static test loading and results, the center of gravity of the APU prototype is used as the loading point of the APU dummy.

[0024] The APU component needs to withstand loads from three directions: heading, lateral, and vertical. A corresponding triangular joint 13 is installed at the center of gravity of the APU component to facilitate the loading of the actuator cylinder.

[0025] Considering the potential for torque effects in three operating conditions—heading, lateral, and vertical—the APU dummy component must have a single-ear connector with a certain torque effect in the direction flush with the triangular connector 13 to facilitate actuator cylinder loading. Therefore, a front connector 12 and a rear connector 11 of the heading stick were designed. Furthermore, since the heading load is the largest (according to CCAR25.561, the forward overload coefficient is the largest, at 9.0g), the front and rear connectors of the heading stick are positioned in the aircraft's heading direction. See [link to relevant documentation]. Figure 3 As shown.

[0026] Considering that the APU dummy needs to be connected to the body, connection interfaces need to be designed. Based on the vibration damper used for the connection of the APU real part, in order to maximize the matching of the load transmission path of the APU dummy and the load of each joint with the APU real part, the APU dummy is connected to the APU vibration damper real part. Therefore, each connection interface is matched with the APU vibration damper real part. Thus, the front left column connection 14, the front right column connection 15, and the rear column connection interface 16 are respectively set with the same interface structure and position as the APU real part.

[0027] The aforementioned front right column 01, front left column 02, and rear column 03 are all solid structures. To achieve a match between the stiffness of the APU dummy component and the stiffness of the real component, a solid column (front right column 01, front left column 02, and rear column 03) is designed on the upper part of each of the three connection interfaces (front left column connection interface 14, front right column connection interface 15, and rear column connection interface 16) to simulate the stiffness of the interface area of ​​the real APU. The stiffness of each solid column is consistent with the stiffness of each interface area of ​​the real APU component.

[0028] Among them, the shock absorbers connected to the front right column 01 and the front left column 02 are the same parts, and the APU parts are completely symmetrical. Therefore, the front right column 01 and the front left column 02 are designed as solid bodies with the same diameter and height and equal stiffness.

[0029] To facilitate processing, the diameter of the rear column 03 is set to be the same as that of the front right column 01 and the front left column 02. The difference in stiffness between the rear column 03 and the front right column 01 and the front left column 02 is achieved only by changing the height of the rear column 03.

[0030] To facilitate displacement measurement during static testing and to facilitate monitoring and comparison of displacement under heading, vertical and lateral load conditions during the test, all solid columns are set to be horizontal, and the top surfaces of all columns are at the same height. This height is less than the height of the triangular joint 13 and each diagonal brace set at the center of gravity of the APU dummy part, so as to leave space for static testing for dynamic cylinder loading.

[0031] The aforementioned yaw bar 08 is a solid structure to improve the local stiffness of the loading area of ​​the dummy actuator cylinder.

[0032] The aforementioned front horizontal bar 04, outer horizontal bar 05, inner horizontal bar 06, rear diagonal brace 07, front inner diagonal brace 09, and front outer diagonal brace 10 are all hollow bars. To ensure the dummy component can withstand vertical loads, diagonal braces are installed between each column. Since each connecting rod forms a triangular stable structure after connection, its structure can effectively ensure load transfer and structural stiffness. Therefore, all connecting rods are made hollow bars to reduce weight.

[0033] The connections of the aforementioned front horizontal bar 04, outer horizontal bar 05, inner horizontal bar 06, rear diagonal brace 07, front inner diagonal brace 09, and front outer diagonal brace 10 are all welded and fixed.

[0034] The aforementioned APU dummy components are all constructed from 30CrMnSiA.

[0035] The aforementioned APU dummy component welding fixing structure uses 0Cr18Ni9 as the welding material.

[0036] The aforementioned design method for the APU dummy component involves: calculating the center of gravity of the APU real component and placing the triangular connector 13 in the APU dummy component at the center of gravity of the APU real component; constructing finite element models of the APU real component and the APU dummy component, and performing finite element analysis; applying yaw load, lateral load, and vertical load to the center of gravity of the APU real component and the triangular connector 13 of the APU dummy component, respectively; comparing the deformation displacement of the finite element models of the APU real component and the dummy component under each load and the consistency of the load distribution at each interface to ensure that the deformation displacement deviation and load distribution deviation of the finite element models of the APU real component and the dummy component are within the design range; through this design, the matching of the stiffness of the APU dummy component and the stiffness of the APU real component is effectively ensured.

[0037] The method for calculating the center of gravity of the aforementioned APU component is as follows: Based on cross-sectional similarity, the APU prototype is divided into seven segments along the flight path: L1 to L7, see [link to relevant documentation]. Figure 6 ; Calculate the weight of each segment separately. M i and the corresponding centroid coordinates ( X i , Y i , Z i (See Table 1 for details); Calculate the center of gravity of the APU component using the following formula ( X 0, Y 0, Z 0):

[0038]

[0039]

[0040] In the formula, M i For APU genuine parts i Segment weight, M This is the total weight of the APU component.

[0041] Table 1

[0042] Specifically, the construction and analysis of the finite element models of the APU real component and the APU dummy component were carried out using the software HyperMesh / HyperWorks, and the steps are as follows: Step 1: Obtain the cross-sectional characteristic data of each segment of the APU component at the center of gravity; Step 2: Input the profile characteristic data into the finite element software HyperMesh. See [link / reference]. Figure 7 ; Step 3: Based on the APU prototype model, establish the interface models, set the constraints of the interface parts, and complete the finite element model construction of the APU prototype. Step 4, at the center of gravity of the APU component ( X 0, Y 0, Z 0) Set up three loading conditions: heading, lateral, and vertical. The heading load is F1, the lateral load is F2, and the vertical downward load is F3. The deformation displacement and load distribution of each interface of the APU component in the heading, lateral, and vertical directions are obtained accordingly. Step 5: Input the finite element model parameters of the APU dummy into the finite element software HyperMesh, and set the same interface model and interface constraints as in Step 3 to complete the finite element model construction of the APU dummy. Step 6: Apply the same load as in step 4 to the triangular joint 13 of the APU dummy to obtain the yaw, lateral and vertical deformation displacement and load distribution of each interface of the APU dummy. Step 7: Compare the results obtained in steps 4 and 6 to ensure that the deformation deviation and load distribution deviation between the real and dummy APU parts are within the design range, so as to ensure that the stiffness of the dummy APU parts matches that of the real APU parts.

[0043] In step 1 above, the profile characteristics at the centroid of each segment are shown in Table 2: Table 2

[0044] In step 5 above, the parameters of the APU dummy finite element model include: the wall thickness, pipe diameter and thickness of the front horizontal bar 04, the outer horizontal bar 05, the inner horizontal bar 06, the rear diagonal brace 07, the front inner diagonal brace 09, and the front outer diagonal brace 10, as well as the welding thickness and welding area of ​​each connecting rod.

[0045] In step 7 above, when the deviation exceeds the design range, the parameters of the APU dummy finite element model are adjusted, and the finite element analysis continues until the deviation is within the design range. The design range is: deformation deviation within ±2% and load distribution deviation within ±2%.

[0046] Through the above design, the APU dummy structure of the present invention effectively meets the following design requirements: 1) The mounting structure is consistent with the machine mounting interface; 2) It has connection ports that can withstand loading from horizontal, vertical and lateral directions; 3) The strength meets the requirements to avoid damage to the dummy during static testing; 4) The stiffness matches that of the real APU.

[0047] After the design is completed, the APU dummy of the present invention shall be manufactured according to the following method: Specifically, all the following connectors are made of 30CrMnSiA material. The connection process is unique: all connections are made by welding, using 0Cr18Ni9 as the welding material.

[0048] S1. Weld the front right column 01 to the front right column connection interface 15, the front left column 02 to the front left column connection interface 14, and the rear column 03 to the rear column connection interface 16 respectively. S2. Weld the above-obtained welded parts to each horizontal bar (outer horizontal bar 05, front horizontal bar 04, inner horizontal bar 06); S3. Weld the triangular connector 13 to the heading rod 08; S4. The welded parts obtained in S3 are welded to the welded parts obtained in S2 through each of the diagonal braces (front outer diagonal brace 10, front inner diagonal brace 09 and rear diagonal brace 07); S5. Spray painting for corrosion protection, using MS 25D05 primer and MS 25D06 topcoat.

[0049] The welding process is complete upon completing the above steps. See the actual sample for details. Figure 8 .

[0050] Specifically, in the horizontal direction, the front left column 02 and the rear column 03 are connected by the outer horizontal bar 05; the front left column 02 and the front right column 01 are connected by the front horizontal bar 04, with a spacing of 330mm; the front right column 01 and the rear column 03 are connected by the inner horizontal bar 06; the yaw distance between the rear column 03 and the front left column 02 and the right column 01 is 438mm; to ensure that the dummy can withstand the load in the vertical direction, diagonal braces and yaw bars 08 are set between each column, and each diagonal brace and axial bar is connected by a joint 13; among them, the yaw bar 08 is a solid bar to improve the rigidity of the dummy.

[0051] Specifically, all horizontal and diagonal braces are hollow bars with an inner diameter of 21mm, an outer diameter of 25mm, and a thickness of 4mm. The heading bar 08 is a solid bar with a diameter of Ø30mm.

[0052] To meet the requirements of heading, vertical and lateral loading in the static test of APU components, three Ø10mm diameter holes are reserved on the triangular joint 13, and the thickness of the triangular joint 13 is 15mm. One Ø10mm diameter hole is reserved at each end of the heading rod 08. The thickness of the front heading rod joint 12 and the rear heading rod joint 11 at both ends is 10mm, and the distance between the joint holes at both ends is 230mm.

[0053] This invention describes the design method, specific structure, and manufacturing process of an APU dummy component used in APU static testing. This APU dummy component has been successfully applied in the static testing of the APU of a large amphibious aircraft. This test is a reserved item by the airworthiness verification authority. The dummy component and loading components have been approved by the authority, and the relevant static test and analysis reports have been approved. See [link to relevant documentation]. Figure 9 .

[0054] The above-described embodiments merely illustrate the implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. An APU dummy component, characterized in that, It includes a front right column, a front left column, and a rear column located at the three vertices of the triangle; the front right column and the front left column are connected to each other, the front left column and the rear column are connected to each other, and the front right column and the rear column are connected to each other via a front horizontal bar, an outer horizontal bar, and an inner horizontal bar, respectively; a triangular joint is provided at the top of the triangle, and the triangular joint is connected to the heading rod; the heading rod is connected to the rear column, the front right column, and the front left column via a rear diagonal brace, a front inner diagonal brace, and a front outer diagonal brace, respectively; the front and rear ends of the heading rod are respectively provided with a heading rod front joint and a heading rod rear joint; the bottom of the front left column, the front right column, and the rear column are respectively provided with a front left column connection interface, a front right column connection interface, and a rear column connection interface with the same interface structure and position as the APU component; the triangular joint is located at the center of gravity of the APU component.

2. The APU dummy component according to claim 1, characterized in that, The front right column, front left column, rear column, and yaw bar are all solid structures.

3. The APU dummy component according to claim 1, characterized in that, The front horizontal bar, outer horizontal bar, inner horizontal bar, rear diagonal brace, front inner diagonal brace, and front outer diagonal brace are all hollow bars.

4. The APU dummy component according to claim 1, characterized in that, The connections of the front horizontal bar, outer horizontal bar, inner horizontal bar, rear diagonal brace, front inner diagonal brace, and front outer diagonal brace are all fixed by welding.

5. A design method for an APU dummy component as described in any one of claims 1-4, characterized in that, Calculate the center of gravity of the APU real component and place the triangular joint of the APU dummy component at the center of gravity of the APU real component. Construct finite element models of the APU real component and the APU dummy component and perform finite element analysis: apply yaw load, lateral load and vertical load to the center of gravity of the APU real component and the triangular joint of the APU dummy component respectively, and compare the deformation displacement of the finite element models of the APU real component and the dummy component under each load and the consistency of the load distribution at each interface to ensure that the deformation displacement deviation and load distribution deviation of the finite element models of the APU real component and the dummy component are within the design range.

6. The design method for an APU dummy component according to claim 5, characterized in that, The method for calculating the center of gravity of an APU component is as follows: Based on cross-sectional similarity, the APU prototype is divided into seven segments along the flight direction, namely: L1~L7; Calculate the weight M of each segment separately. i and the corresponding centroid coordinates (X) i Y i Z i ); Calculate the center of gravity (X0, Y0, Z0) of the APU component using the following formula: , , , In the formula, M i Let M be the weight of the i-th segment of the APU component, and M be the total weight of the APU component.

7. The design method for an APU dummy component according to claim 6, characterized in that, The construction and finite element analysis of the APU real component and APU dummy component were performed using HyperMesh, and the steps are as follows: Step 1: Obtain the cross-sectional characteristic data of each segment of the APU component at the center of gravity; Step 2: Input the profile characteristic data into the finite element software HyperMesh; Step 3: Based on the finite element model of the APU real component, establish the interface models, set the constraints of the interface parts, and complete the finite element model construction of the APU real component. Step 4: Apply corresponding loads along the heading, lateral, and vertical directions at the center of gravity (X0, Y0, Z0) of the APU real part, respectively, to obtain the deformation displacement of the APU real part in the heading, lateral, and vertical directions and the load distribution of each interface. Step 5: Input the finite element model parameters of the APU dummy into the finite element software HyperMesh, and set the same interface model and interface constraints as in Step 3 to complete the finite element model construction of the APU dummy. Step 6: Apply the same load as in step 4 to the triangular joint of the APU dummy to obtain the yaw, lateral, and vertical deformation displacements of the APU dummy and the load distribution of each interface. Step 7: Compare the results obtained in steps 4 and 6 to ensure that the deformation deviation and load distribution deviation between the real and dummy APUs are within the design range.

8. The design method for an APU dummy component according to claim 7, characterized in that, In step 1, the profile characteristics at the centroid of each segment are shown in the table below: 。 9. The design method for an APU dummy component according to claim 7, characterized in that, In step 5, the parameters of the APU dummy finite element model include: the diameter and thickness of the front horizontal bar, outer horizontal bar, inner horizontal bar, rear diagonal brace, front inner diagonal brace, and front outer diagonal brace, as well as the weld thickness and weld area.

10. The design method for an APU dummy component according to claim 7, characterized in that, In step 7, when the deviation exceeds the design range, the parameters of the APU dummy finite element model are adjusted and iterative analysis continues until the deviation is within the design range.

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