A device for detecting the arc of aircraft parts and its stability evaluation method

Abstract

This invention provides a device for inspecting the circular arc surfaces of aircraft parts and a method for evaluating their stability. The device includes a dial indicator, fixing screws, and a testing frame. The testing frame has a three-jaw, equally divided structure with a through hole through which the fixing screws can pass. The testing frame is fixed to the middle of the measuring rod of the dial indicator by the fixing screws. The testing method uses the bowstring method of the dial indicator to measure the hole depth and butt joint depth of the measured convex or concave circular arc surface. This invention is a handheld circular arc surface inspection device, which is convenient to operate and easy to operate online in the field. It also has high measurement accuracy, replacing the problem of poor accuracy when using a hook ruler in the field. In addition, with the use of a measuring needle, it can perform high-precision measurements of small holes in the skin, the skin butt joint depth, and the scratch depth.

Description

Technical Field

[0001] This invention relates to the field of measurement technology, specifically to a device for detecting the arc of aircraft parts and a method for evaluating its stability. Background Technology

[0002] In the manufacturing and inspection of aircraft parts, dimensional issues related to curved surfaces that cannot be directly measured are frequently encountered, such as the depth of holes and the depth of butt joints, as well as the depth of scratches on convex or concave curved surfaces. Measuring these curved parts requires the use of measuring tools such as gauges, depth gauges, and feeler gauges. Especially when the diameter of the hole is smaller than the diameter of the gauge, other auxiliary tools are usually needed for measurement. This method of inspection is time-consuming, labor-intensive, inefficient, and lacks accuracy. For mass-produced curved parts, the use of traditional inspection methods severely impacts on-time product delivery.

[0003] There is an urgent need to provide a method for evaluating the stability of a circular arc surface inspection device that can be directly used on the production site. The inspection device developed using this method should have high measurement accuracy, a wide range, simple structure, small size, and low cost, so as to make up for the shortcomings of current circular arc surface inspection and measurement methods. Summary of the Invention

[0004] Purpose of the Invention: To address the technical problem of low accuracy in measuring the depth of holes, especially small holes, on arc surfaces during the processing and inspection of aircraft parts, where there is no direct method for detection and indirect or auxiliary measurement methods are commonly used, and the problem that qualitative measurement methods are mostly used when detecting scratches and gaps in arc areas, which cannot accurately measure the depth of scratches, this invention provides a mechanically based detection device for arc surfaces of aircraft parts and its stability evaluation method. The device includes a dial indicator, a fixing screw, and a detection frame. The detection frame has a three-jaw equidistant structure with a through hole through which the fixing screw can pass. The detection frame is fixed to the middle of the measuring rod of the dial indicator by the fixing screw.

[0005] In a first aspect, this application provides an aircraft part arc detection device, the device comprising:

[0006] Testing frame;

[0007] The measuring claw is installed on the lower part of the detection frame;

[0008] A measuring column is installed on the upper part of the detection frame;

[0009] A dial indicator is positioned on the measuring column.

[0010] Secondly, this application also provides a stability evaluation method for an aircraft parts arc detection device, the method comprising the following steps:

[0011] Step 1: Establish a reasonably simplified finite element model of the aircraft part arc detection device;

[0012] Step 2: Parametric modeling of the measuring claw considering structural stability;

[0013] Step 3: Finite element simulation calculation;

[0014] Step 4: Establish the criteria for stability assessment.

[0015] Preferably, step one involves establishing a reasonably simplified finite element model of the aircraft part arc detection device, and the specific process is as follows:

[0016] A three-dimensional geometric model of the aircraft part arc detection device was created using CAD software. All parts except dial indicator, measuring column, detection frame and measuring claw were deleted from the aircraft part arc detection device model to create a simplified model. The simplified model was ensured to have the same length, width and height as the actual aircraft part arc detection device.

[0017] A measurement object model is established below the simplified model. The length and width of the measurement object model are not less than the length and width outline dimensions of the actual aircraft part arc detection device.

[0018] Preferably, the parametric modeling of the measuring claw considering structural stability in step two includes the following steps:

[0019] Based on step 1, keep the geometry and size of the measuring claw unchanged, only increase the number of measuring claws, and establish three-dimensional geometric models of the aircraft part arc detection device with different numbers of measuring claws respectively;

[0020] For the three-dimensional geometric model of the aircraft part arc detection device with different numbers of measuring claws, keep the geometry unchanged and only change its height. Increase the original measuring claw height by 1mm in a single step to establish the three-dimensional geometric model of the aircraft part arc detection device with different measuring claw heights.

[0021] Preferably, the finite element simulation calculation in step four includes the following steps:

[0022] For each physical component of the dial indicator, measuring column, testing frame, measuring jaws, and the model of the object being measured, set Young's modulus, Poisson's ratio, and density;

[0023] Boundary condition setting;

[0024] Grid generation;

[0025] The displacement and stress fields of the three-dimensional geometric model of the aircraft part arc detection device were calculated using the statics module of the finite element software.

[0026] Preferably, the boundary condition setting includes:

[0027] Set a constraint at the bottom of the object model to limit 6 degrees of freedom; the frictional force between the measuring claw and the object model is used as the supporting force to maintain stability, and the friction coefficient between the three-dimensional geometric model of the measuring claw and the object model is input.

[0028] Preferably, the grid division includes:

[0029] In the three-dimensional geometric model and measurement object model of the aircraft part arc detection device, the maximum dimensions of a single grid do not exceed 10% of the length, width, and height of the part.

[0030] Preferably, step four, establishing the stability judgment criteria, includes the following steps:

[0031] 4-1 The normal interaction force T between the measuring jaw and the measured object model in the aircraft part circular arc inspection device model is obtained by integrating the contact stress using Formula 1. z

[0032] T z =-∫σ z dA 1

[0033] Where, σ z Let A be the stress component along the vertical direction for each element, and A be the contact area; the normal interaction force T is obtained by integrating over the entire contact area. z ;

[0034] 4-2 Repeat step 4-1 to iterate and calculate the normal interaction force T between the i-th measuring claw and the measured object model. z,i Record the maximum value T of the normal interaction force. z,max and minimum value T z,min ;

[0035] 4-3 Establish stability criteria based on Formula 2:

[0036]

[0037] Wherein, ε is the stable use probability of the aircraft part arc detection device model; when the calculated result of ε is equal to 100%, it means that the stability of the aircraft part arc detection device during use is good. When the calculated result of ε is less than or equal to the design value, it is necessary to modify the number of measuring claws and the height of measuring claws in the simplified model, and repeat step two until the calculated stable use probability ε meets the actual requirements.

[0038] The beneficial effects of this invention are:

[0039] This invention is a handheld arc surface inspection device, which is convenient to operate and easy to use online in the field. In the inspection of batch-produced parts, it replaces traditional measurement methods such as feeler gauges and hook gauges. This rapid arc surface inspection device based on a dial indicator greatly improves inspection efficiency and accuracy. The invention has a robust structure, ensuring uniform stress on all parts during measurement, making it durable and resistant to damage. Compared with existing arc surface inspection technologies, this structure improves measurement stability and accuracy. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the finite element model of the aircraft part arc detection device in step one of the present invention.

[0041] Figure 2 This is a schematic diagram of a three-dimensional geometric model of the aircraft part arc detection device with different numbers of measuring claws in step two of the present invention;

[0042] Figure 3 This is a schematic diagram of the mesh division result in step three of the present invention;

[0043] Figure 4 This is a schematic diagram showing the results of calculating the normal interaction force in step three of this invention;

[0044] Figure 5 This is a schematic diagram showing the stable usage probability of the aircraft part arc detection device model with different numbers of measuring claws and different measuring claw heights, calculated in step four of this invention.

[0045] The numbers in the diagram are explained as follows: 1. Dial gauge; 2. Measuring column; 3. Inspection frame; 4. Measuring claw; 5. Measurement object. Detailed Implementation

[0046] This invention provides a device for inspecting the circular arc surfaces of aircraft parts and a method for evaluating their stability. The device includes a dial indicator, fixing screws, and a testing frame. The testing frame has a three-jaw, equally divided structure with a through hole through which the fixing screws can pass. The testing frame is fixed to the middle of the measuring rod of the dial indicator by the fixing screws. The testing method uses the bowstring method of the dial indicator to measure the hole depth and butt joint depth of the measured convex or concave circular arc surface. This invention is a handheld circular arc surface inspection device, which is convenient to operate and easy to operate online in the field. It also has high measurement accuracy, replacing the problem of poor accuracy when using a hook ruler in the field. In addition, with the use of a measuring needle, it can perform high-precision measurements of small holes in the skin, the skin butt joint depth, and the scratch depth.

[0047] Please see Figure 1-Figure 5 The technical solution of the present invention is: a stability evaluation method for an aircraft part arc detection device based on mechanics, comprising the following steps:

[0048] Step 1: Establish a reasonably simplified finite element model of the aircraft part arc detection device;

[0049] Step 2: Parametric modeling of the measuring claw considering structural stability;

[0050] Step 3: Finite element simulation calculation;

[0051] Step 4: Establish the criteria for stability assessment;

[0052] The first step involves establishing a reasonably simplified finite element model of the aircraft part arc detection device. The specific process is as follows:

[0053] 1-1 A three-dimensional geometric model of the aircraft part arc inspection device was created using CATIA 2018 software. All parts except for dial indicator 1, measuring column 2, inspection frame 3, and measuring jaw 4 were removed from the original model to create a simplified model. The simplified model was ensured to have the same length, width, and height dimensions as the actual aircraft part arc inspection device. Figure 1 As shown;

[0054] 1-2 Below the simplified model, establish the measurement object model 5. The length and width of the measurement object model are not less than the length and width outline dimensions of the actual aircraft part arc detection device. In this embodiment, the length, width, and height of the measurement object model are 200mm, 200mm, and 3mm, respectively.

[0055] The parametric modeling of the measuring claw considering structural stability in step two includes the following steps:

[0056] 2-1 Based on step 1, keeping the geometry and dimensions of the measuring claws unchanged, only the number of measuring claws is increased from 2 to 7. Three-dimensional geometric models of the aircraft part arc detection device are established for different numbers of measuring claws, such as... Figure 2 As shown;

[0057] 2-2 For the three-dimensional geometric model of the aircraft part arc detection device with different numbers of measuring claws, keep the geometry unchanged and only change its height. Increase the original measuring claw height of 16mm by 1mm in a single step to establish the three-dimensional geometric model of the aircraft part arc detection device with different measuring claw heights of 15mm and 16mm.

[0058] Step three, the finite element simulation calculation, includes the following steps:

[0059] 3-1 Young's modulus, Poisson's ratio, and density are set for each physical component of the dial indicator, measuring column, testing frame, measuring jaws, and the model of the object being measured. In this embodiment, the Young's modulus of dial indicator 1, measuring column 2, testing frame 3, and measuring jaws 4 are uniformly set to 70 GPa, and the Poisson's ratio to 0.33. The density is 2.63 × 10⁻⁶. -9 t / mm3 The Young's modulus of the measured object model 5 is 210 × 10⁻⁶. 5 GPa, Poisson's ratio is 0.30, and density is 4×10 -9 t / mm 3 ;

[0060] 3-2 Boundary Condition Setting: Set constraints on the bottom of the measurement object model 5 to limit 6 degrees of freedom; the frictional force between the measuring claw 4 and the measurement object model 5 is used as the supporting force to maintain stability, and the friction coefficient between the measuring claw 4 and the measurement object model 5 is input as μ = 0.2;

[0061] 3-3 Mesh Generation: In the 3D geometric model and measurement object model of the aircraft part arc detection device, the maximum dimensions of a single mesh do not exceed 10% of the part's dimensions. Figure 3 As shown;

[0062] 3-4 uses the statics module of the finite element software AQBAQUS 6.14 to calculate the displacement and stress fields of the three-dimensional geometric model of the aircraft part arc detection device during use, such as... Figure 4 As shown.

[0063] Step three, establishing the criteria for stability assessment, includes the following steps:

[0064] 4-1 The normal interaction force T between the measuring jaw and the measured object model in the aircraft part circular arc inspection device model is obtained by integrating the contact stress using Formula 1. z

[0065] T z =-∫σ z dA 1

[0066] Where, σ z For each element, the stress component along the vertical direction is represented by the CPRESS compressive stress result, where A represents the contact area of ​​45 mm². 2 By summing up each element and integrating over the entire contact area, the normal interaction force T is obtained. z =1.05N;

[0067] 4-2 Repeat step 4-1, iterating through the three measuring jaws and calculating the normal interaction forces between them and the measured object model. The results are 1.08N, 1.05N, and 1.05N, respectively. Record the maximum normal interaction force T. z,max =1.08N and minimum value T z,min =1.05N;

[0068] 4-3 Establish stability criteria based on Formula 2:

[0069]

[0070] Where ε represents the stable usage probability of the aircraft part arc detection device model. In this embodiment, the stable usage probabilities ε for jaw heights of 15mm and 16mm are 97.6% and 96.3%, respectively, indicating good stability of the aircraft part arc detection device during use. When the calculated result of ε is less than or equal to the design value, it is necessary to increase the number of jaws or decrease the jaw height in the simplified model, repeating step two until the calculated stable usage probability ε meets the actual requirements. Figure 5 As shown.

[0071] This invention provides a device for detecting the radius of a circular arc based on a dial indicator, such as... Figure 1 As shown, it consists of a dial indicator, a testing frame, measuring jaws, and a measuring column. The specific implementation steps are as follows:

[0072] (1) Assembly and calibration. Pass the measuring rod of the dial indicator vertically through the through hole in the middle of the test frame, and lock the test frame and dial indicator together with screws to assemble the measuring device. Place the measuring rod and measuring column of the dial indicator against the calibration platform at the same time, and rotate the dial indicator scale until the pointer coincides with the zero position.

[0073] (2) Measure the depth of the hole on the arc surface. Distribute the dial indicator measuring column at the hole opening, align and zero the dial indicator measuring rod at the hole opening, and insert the measuring rod and dial indicator into the bottom of the hole through the measuring frame (different deep holes and small holes can be measured by changing the diameter of the measuring head and the length of the measuring rod). Measure the hole diameter depth on the arc surface by reading the dial indicator.

[0074] (3) Measure the depth of scratches and gaps on the arc surface. Distribute the dial indicator measuring column on both sides of the scratch. Align and zero the dial indicator measuring rod on the arc surface. Insert the measuring rod and dial indicator into the bottom of the scratch through the measuring frame (different widths of scratches can be measured by changing the diameter of the measuring head). Measure the depth of the scratch on the arc surface by reading the meter.

Claims

1. A method for evaluating the stability of an aircraft parts arc detection device, characterized in that, The method includes the following steps: Step 1: Establish a reasonably simplified finite element model of the aircraft part arc detection device; the aircraft part arc detection device includes a detection frame, a measuring jaw, a measuring column, and a dial indicator; wherein, the measuring jaw is installed on the lower part of the detection frame; the measuring column is installed on the upper part of the detection frame; and the dial indicator is arranged on the measuring column; Step 2: Parametric modeling of the measuring claw considering structural stability; Step 2 includes the following steps: Based on Step 1, keeping the geometry and size of the measuring claw unchanged, only increasing the number of measuring claws, and establishing three-dimensional geometric models of the aircraft part arc detection device with different numbers of measuring claws respectively; For the three-dimensional geometric models of the aircraft part arc detection device with different numbers of measuring claws, keeping the geometry unchanged, only changing its height, increasing the original measuring claw height by 1mm at a time, and establishing three-dimensional geometric models of the aircraft part arc detection device with different measuring claw heights; Step 3: Finite element simulation calculation; Step 4: Establish stability judgment criteria; Step 4 includes the following steps: 4-1 The normal interaction force T between the measuring claw and the measured object model in the aircraft part circular arc inspection device model is obtained by integrating the contact stress using formula (1). z ; T z =-∫σ z dA (1) Where, σ z Let A be the stress component along the vertical direction for each element, and A be the contact area; the normal interaction force T is obtained by integrating over the entire contact area. z ; 4-2 Repeat step 4-1 to iterate and calculate the normal interaction force T between the i-th measuring claw and the measured object model. z,i Record the maximum value T of the normal interaction force. z,max and minimum value T z,min ; 4-3 Establish the stability criterion based on formula (2): Wherein, ε is the stable use probability of the aircraft part arc detection device model; when the calculated result of ε is equal to 100%, it means that the stability of the aircraft part arc detection device during use is good. When the calculated result of ε is less than or equal to the design value, it is necessary to modify the number of measuring claws and the height of measuring claws in the simplified model, and repeat step two until the calculated stable use probability ε meets the actual requirements.

2. The method according to claim 1, characterized in that, Step one involves establishing a reasonably simplified finite element model of the aircraft part arc detection device. The specific process is as follows: A three-dimensional geometric model of the aircraft part arc detection device was created using CAD software. All parts except dial indicator, measuring column, detection frame and measuring claw were deleted from the aircraft part arc detection device model to create a simplified model. The simplified model was ensured to have the same length, width and height as the actual aircraft part arc detection device. A measurement object model is established below the simplified model. The length and width of the measurement object model are not less than the length and width outline dimensions of the actual aircraft part arc detection device.

3. The method according to claim 1, characterized in that, The finite element simulation calculation in step three includes the following steps: For each physical component of the dial indicator, measuring column, testing frame, measuring jaws, and the model of the object being measured, set Young's modulus, Poisson's ratio, and density; Boundary condition setting; Grid generation; The displacement and stress fields of the three-dimensional geometric model of the aircraft part arc detection device were calculated using the statics module of the finite element software.

4. The method according to claim 3, characterized in that, The boundary condition settings include: Set a constraint limiting 6 degrees of freedom at the bottom of the object model; the frictional force between the measuring claw and the object model serves as the supporting force to maintain stability, and input the friction coefficient between the three-dimensional geometric models of the measuring claw and the object model.

5. The method according to claim 4, characterized in that, The grid division includes: In the three-dimensional geometric model and measurement object model of the aircraft part arc detection device, the maximum dimensions of a single grid do not exceed 10% of the length, width, and height of the part.

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