A method for fabricating pressure measuring holes on the surface of an experimental model

Abstract

This invention relates to a method for machining pressure measuring holes on the surface of a test model, comprising the following steps: Step 1: Fabricating a clamping plate according to the location of the pressure measuring hole and the profile of the test model at that location; Step 2: Marking a reference point 'a' on the inner surface of the clamping plate and a corresponding reference point 'b' on the test model, measuring the offset distance Δ of the pressure measuring hole relative to reference point 'b', and marking the inner surface of the clamping plate with the same offset distance Δ based on reference point 'a'; Step 3: Machining a guide hole on the clamping plate at the marked pressure measuring hole location using a small multi-axis CNC machining center according to the spatial angle of the pressure measuring hole; Step 4: Fixing the clamping plate to the marked location on the test model, and using a drilling tool to pass the drill bit through the guide hole to machine the pressure measuring hole on the test model. This invention, based on a small multi-axis CNC machining center and a drilling tool, achieves low-cost and precise machining of pressure measuring holes on the three-dimensional curved surface of a large-size model.

Description

Technical Field

[0001] This invention relates to the field of fluid mechanics testing technology, and in particular to a method for processing pressure measuring holes on the surface of a test model. Background Technology

[0002] The pressure on the surface of an object, often referred to as "pressure," is a frequently conducted measurement experiment in fluid mechanics. Measuring the pressure and its distribution on an object's surface provides data support for its fluid dynamics shape and structural design. The pinhole pressure measurement method is a commonly used method for measuring surface pressure. It involves drilling a small hole along the normal direction on the object's surface, connecting a pressure measuring tube to the rear end, and sensing the local pressure. Theory and practice show that to accurately obtain the surface pressure of an object, the following requirements apply to the pressure measuring hole: ①. Diameter d is generally 0.5mm-2mm; ②. The ratio of depth h to diameter d is greater than 2; ③. The axis is perpendicular to the object's surface; ④. The inner wall of the hole is smooth, and the orifice is burr-free. Among these, the perpendicularity of the pressure measuring hole axis to the object's surface is particularly important. In a rectangular coordinate system, the spatial angle of the pressure measuring hole axis can be determined by two parameters: the angle θ between it and the z-axis, and the angle φ between its projection onto the Oxy plane and the x-axis.

[0003] Common surface and underwater vehicles often exhibit strong three-dimensional geometric features, particularly at the bow and stern. Taking modern ships as an example, their bows feature bulbous bows, and their sterns have propeller-supported structures, both relatively small and pointed in size compared to the overall hull. The midsection is a relatively large, parallel midbody, thus highlighting the distinct three-dimensional characteristics of the bow and stern lines. When machining pressure testing holes in these areas, to ensure the hole axis is perpendicular to the surface, a multi-axis CNC machining center capable of precisely controlling the drilling angle is typically required.

[0004] The Reynolds number (Re) is an important physical parameter for conducting fluid dynamics experiments.

[0005]

[0006] In the formula, U is the incoming flow velocity, L is the characteristic length of the test model, and υ is the kinematic viscosity of the fluid.

[0007] Currently, fluid mechanics experiments for engineering applications are increasingly moving towards higher Relative Dynamics (Re). However, existing testing equipment has limited fluid media and flow rates. Therefore, increasing the size of the test model is a common approach when the testing equipment allows. However, machining pressure measurement holes on the surface of large-scale test models with significant three-dimensional features requires drilling on large multi-axis CNC machining centers. Due to the relative scarcity of large multi-axis CNC machining centers, the machining cost is extremely high.

[0008] In summary, the current method of machining pressure measuring holes on the three-dimensional curved surface of large-size test models requires drilling on a large multi-axis CNC machining center, which is extremely costly and there is still considerable room for improvement in the machining method.

[0009] Therefore, we propose a method for fabricating pressure measurement holes on the surface of an experimental model. Summary of the Invention

[0010] To address the shortcomings of existing production technologies, the applicant provides a method for machining pressure measurement holes on the surface of a test model. This method involves introducing a clamping tool that is relatively small compared to the test model, marking the positions of the pressure measurement holes on the clamping tool, machining guide holes using a small multi-axis CNC machining center, and finally achieving low-cost and precise machining of pressure measurement holes on the three-dimensional curved surface of a large-size model using the clamping tool.

[0011] The technical solution adopted in this invention is as follows:

[0012] A method for fabricating pressure measurement holes on the surface of a test model includes the following steps:

[0013] Step 1: Make the cardboard;

[0014] A clamping plate is made according to the location of the pressure measuring hole and the profile of the test model at that location, and the installation position of the clamping plate is marked on the test model. The inner surface of the clamping plate matches the outer surface of the test model.

[0015] Step 2: Mark the positions of the pressure testing holes on the card plate;

[0016] Mark a reference point a on the inner surface of the plate and a reference point b at the corresponding position on the test model. Measure the offset distance Δ of the pressure measuring hole relative to the reference point b. Mark the inner surface of the plate with the same offset distance Δ based on the reference point a.

[0017] Step 3: Machining guide holes on the card plate;

[0018] At the pressure testing hole position marked on the card plate, a small multi-axis CNC machining center is used to machine a guide hole on the card plate according to the spatial angle of the pressure testing hole. The guide hole connects the inner surface of the card plate and the outer surface of the card plate. The diameter of the guide hole is less than or equal to the diameter of the pressure testing hole.

[0019] Step 4: Machining pressure measurement holes on the test model;

[0020] Fix the clamping plate at the marked position on the test model, align the axis of the guide hole with the axis of the pressure measuring hole, guide and position the drill bit through the guide hole, and use a drilling tool to pass the drill bit through the guide hole to machine the pressure measuring hole on the test model.

[0021] Its further features are:

[0022] The outer surface of the card is obtained by linear expansion of the inner surface of the card.

[0023] The distance between the outer surface and the inner surface of the card plate is the width of the card plate. The width of the card plate is greater than the thickness of the card plate, and the thickness of the card plate is greater than the diameter of the pressure measuring hole.

[0024] The card and the test model are bonded together with glue.

[0025] The beneficial effects of this invention are as follows:

[0026] The method of this invention is scientific, reasonable, and easy to operate. It does not rely on the relatively scarce large multi-axis CNC machining centers, but is based on the more commonly used small multi-axis CNC machining centers, and realizes low-cost and accurate machining of pressure measuring holes on the three-dimensional curved surface of large-size models.

[0027] In addition, the present invention also has the following advantages:

[0028] (1) The processing cost does not increase with the increase of the size of the test model. The larger the size of the test model, the better the cost reduction effect.

[0029] (2) There are no special requirements for pallet materials, dimensions, processing methods, processing equipment, etc., and the implementation is highly flexible. Attached Figure Description

[0030] Figure 1 This is a flowchart of the processing of the present invention.

[0031] Figure 2 This is a schematic diagram of the card plate and experimental model of the present invention.

[0032] Figure 3 This is a schematic diagram of reference point a on the card plate of the present invention.

[0033] Figure 4 This is a schematic diagram of reference point b in the experimental model of the present invention.

[0034] Figure 5 This is a schematic diagram of the guide hole for the card plate of the present invention.

[0035] Figure 6 This is a schematic diagram of the orifice pressure measurement method of the present invention.

[0036] Figure 7 This is a schematic diagram of the spatial angle of the pressure measuring hole in this invention.

[0037] Figure 8 This is a schematic diagram of the pressure measurement point arrangement in Embodiment 1 of the present invention.

[0038] Figure 9 This is a bottom view of the surface pressure distribution of the test model in straight flight mode in Embodiment 1 of the present invention.

[0039] Wherein: 1. Pressure measuring hole; 101. Pressure measuring hole axis; 2. Pressure measuring tube; 3. Pressure measuring device; 4. Test model; 401. Outer surface of test model; 5. Reference point a; 6. Reference point b; 7. Clamping plate; 701. Inner surface of clamping plate; 702. Outer surface of clamping plate; 8. Guide hole. Detailed Implementation

[0040] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0041] like Figures 1-7 As shown, a method for processing pressure measurement holes on the surface of a test model includes the following steps:

[0042] Step 1: Make the cardboard 7;

[0043] A clamping plate 7 is fabricated based on the location of the pressure measuring hole 1 and the profile of the test model 4 at that location. The installation position of the clamping plate 7 is marked on the test model 4. The inner surface 701 of the clamping plate matches the outer surface 401 of the test model. The outer surface 702 of the clamping plate is obtained by expanding the profile of the inner surface 701 of the clamping plate. The distance between the outer surface 702 and the inner surface 701 of the clamping plate is the width of the clamping plate 7. The width of the clamping plate 7 is greater than the thickness of the clamping plate 7, and the thickness of the clamping plate 7 is greater than the diameter of the pressure measuring hole 1.

[0044] Step 2: Mark the position of pressure test hole 1 on the card plate 7;

[0045] Mark a reference point a5 on the inner surface 701 of the card plate and mark a reference point b6 at the corresponding position of the test model 4. Measure the offset distance Δ of the pressure measuring hole 1 relative to the reference point b6. Based on the reference point a5, mark the inner surface 701 of the card plate with the same offset distance Δ.

[0046] Step 3: Machining guide holes 8 on the clamping plate 7;

[0047] At the pressure measuring hole 1 marked on the card plate 7, a small multi-axis CNC machining center is used to machine a guide hole 8 on the card plate 7 according to the spatial angle of the pressure measuring hole 1. The guide hole 8 connects the inner surface 701 and the outer surface 702 of the card plate. The diameter of the guide hole 8 is less than or equal to the diameter of the pressure measuring hole 1.

[0048] Step 4: Machining pressure measuring hole 1 on test model 4;

[0049] Fix the clamping plate 7 to the marked position on the test model 4, and glue the clamping plate 7 and the test model 4 together. Align the axis of the guide hole 8 with the axis of the pressure measuring hole 101. Guide and position the drill bit through the guide hole 8. Use a drilling tool to pass the drill bit through the guide hole 8 to machine the pressure measuring hole 1 on the test model 4.

[0050] Compared to the test model 4, the clamping plate 7 is smaller and has a more regular shape, requiring fewer processing methods and tools. A commonly used small multi-axis CNC machining center can be used, making the cost of machining the guide hole 8 on the clamping plate 7 far less than directly machining the pressure measuring hole 1 on the test model 4. Since the drill bit can be guided and positioned through the guide hole 8, a simple, ordinary drilling tool, such as a pistol drill, can be used to accurately machine the pressure measuring hole 1 on the large-sized three-dimensional curved surface of the test model 4, thus reducing processing costs.

[0051] like Figure 6 As shown, the orifice pressure measurement method is a commonly used method for measuring the pressure on the surface of an object. It involves making a small hole along the normal direction on the surface of the object, connecting the pressure measuring tube 2 and the pressure measuring device 3 at the rear end, and sensing the local pressure.

[0052] like Figure 7 As shown, in a rectangular coordinate system, the spatial angle of the pressure measuring hole axis 101 can be determined by two parameters: the angle θ between it and the z-axis, and the angle φ between its projection on the Oxy plane and the x-axis.

[0053] Example 1

[0054] This embodiment further illustrates how to use the method proposed in this invention to process the pressure measurement holes on the surface of the "Yupeng Wheel" wind tunnel test model.

[0055] The "Yupeng" is a modern, multi-purpose cargo training vessel designed and built independently by China. Its main parameters are shown in Table 1. Experimental model 4 has no appendages and a scale ratio of 1:94.5.

[0056] Table 1 Main parameters of Yupeng wheel

[0057]

[0058]

[0059] According to the test requirements, a total of 937 pressure measurement points need to be made on the surface of test model 4, which has a total length of 2.114m. Figure 8 As shown, there are more pressure measurement points located at the bow and stern where the ship's shape changes drastically. The diameter of pressure measurement hole 1 is required to be 1 mm, and the axis 101 of the pressure measurement hole must be perpendicular to the surface of the test model 4.

[0060] The above requirements would be too costly to achieve using traditional large multi-axis CNC machining centers. Therefore, the method proposed in this invention is used, and the machining process is as follows: Figure 1 As shown, it includes the following steps:

[0061] Step 1: Make the cardboard 7;

[0062] The pressure measurement points selected for this experiment were the intersections of the station lines and water lines or longitudinal profiles of test model 4. Test model 4 had 34 stations arranged longitudinally and 13 water lines arranged vertically. To improve efficiency, the pressure measurement points at each station were combined, and a clamping plate 7 was made for each station.

[0063] According to the position of the pressure measuring hole 1 and the profile of the test model 4 at that position, the clamping plate 7 is made, and the installation position of the clamping plate 7 is marked on the test model 4. The inner surface 701 of the clamping plate matches the outer surface 401 of the test model. The clamping plate 7 can be fixed on the surface of the test model 4 by gluing. The outer surface 702 of the clamping plate is obtained by expanding the line of the inner surface 701 of the clamping plate. The width of the clamping plate 7 is about 25mm and the thickness is about 6mm.

[0064] At this time, the maximum size of all the card plates 7 is less than 300mm. The guide holes 8 are made using conventional processing methods and tools, so the impact on processing costs is small.

[0065] Step 2: Mark the position of pressure test hole 1 on the card plate 7;

[0066] Mark a reference point a5 on the inner surface 701 of the card plate, and mark a reference point b6 at the corresponding position of the test model 4. Measure the offset distance Δ of the pressure measuring hole 1 relative to the reference point b6. Based on the reference point a5, mark the inner surface 701 of the card plate with the same offset distance Δ.

[0067] Step 3: Machining guide holes 8 on the clamping plate 7;

[0068] At the pressure testing hole 1 marked on the caliper 7, a VMC-800 five-axis CNC machining center is used. The X / Y / Z axis travel during machining is less than 800mm / 500mm / 500mm. Guide holes 8 are machined according to the spatial angle of each pressure testing hole 1 to connect the inner surface 701 and the outer surface 702 of the caliper. The diameter of the guide holes 8 is ≤1mm. The drill bit is guided and positioned through the guide holes 8.

[0069] Compared to the 2.114m long test model 4, the clamping plate 7 is smaller in size and has a regular shape, requiring fewer processing methods and tools. It uses a commonly used five-axis CNC machining center. Therefore, the cost of machining the guide hole 8 on the clamping plate 7 is much lower than the cost of directly machining the pressure measuring hole 1 on the test model 4.

[0070] Step 4: Make pressure measurement holes on test model 4.

[0071] The card plate 7 is fixed to the marked position on the surface of the test model 4 by adhesive. Each pressure measuring hole 1 is machined by a pistol drill. Since the drill bit is guided and positioned by the guide hole 8, the pressure measuring hole 1 on the three-dimensional curved surface of the large-size test model 4 can be precisely machined.

[0072] Using the aforementioned test model 4, a benchmark test of the surface pressure field of the Yupeng wheel model was conducted in a wind tunnel. Typical results are as follows: Figure 9 As shown, the relevant results effectively demonstrate the flow conditions around the Yupeng wheel test model.

[0073] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A method for processing pressure measuring holes on the surface of a test model, characterized in that, Includes the following steps: Step 1: Make the cardboard (7); According to the position of the pressure measuring hole (1) and the profile of the test model (4) at that position, a clamping plate (7) is made, and the installation position of the clamping plate (7) is marked on the test model (4). The inner surface (701) of the clamping plate matches the outer surface (401) of the test model. Step 2: Mark the position of the pressure testing hole (1) on the card plate (7); Mark a reference point a (5) on the inner surface (701) of the card plate and mark a reference point b (6) at the corresponding position on the test model (4). Measure the offset distance Δ of the pressure measuring hole (1) relative to the reference point b (6). Mark the inner surface (701) of the card plate with the same offset distance Δ based on the reference point a (5). Step 3: Machining guide holes (8) on the card plate (7); At the position of the pressure measuring hole (1) marked on the card plate (7), a small multi-axis CNC machining center is used to machine a guide hole (8) on the card plate (7) according to the spatial angle of the pressure measuring hole (1). The guide hole (8) connects the inner surface (701) and the outer surface (702) of the card plate. The diameter of the guide hole (8) is less than or equal to the diameter of the pressure measuring hole (1). Step 4: Machining pressure measuring holes (1) on the test model (4); Fix the clamp (7) at the marked position on the test model (4) so ​​that the axis of the guide hole (8) coincides with the axis of the pressure measuring hole (101). Guide and position the drill bit through the guide hole (8). Use a drilling tool to make the drill bit pass through the guide hole (8) to process the pressure measuring hole (1) on the test model (4). The outer surface (702) of the card plate is obtained by the linear expansion of the inner surface (701) of the card plate; the width of the card plate (7) is 25mm and the thickness is 6mm.

2. The method for processing pressure measuring holes on the surface of a test model as described in claim 1, characterized in that: The distance between the outer surface (702) and the inner surface (701) of the card plate is the width of the card plate (7). The width of the card plate (7) is greater than the thickness of the card plate (7), and the thickness of the card plate (7) is greater than the diameter of the pressure measuring hole (1).

3. The method for processing pressure measuring holes on the surface of a test model as described in claim 1, characterized in that: The card plate (7) and the test model (4) are bonded together with glue.

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