A method for controlling deformation of a thin plate-shaped part based on bridge monitoring

Abstract

In view of the problem that the thin plate test model of an aviation wind tunnel is prone to deformation caused by clamping and cutting force, a thin plate part machining deformation control method based on bridge monitoring is provided.The method sets a rectangular measuring beam between the part body and the process support, pastes strain gauges, and forms an electric bridge for measuring longitudinal force, transverse force and rolling force;first, the zero point under no load is collected, and when clamping, the clamping force is adjusted to eliminate over-constraint with the electric bridge voltage fluctuation ≤0.1 mV as the standard;the limit stress of the measuring beam corresponding to the allowable deformation of the part is obtained through simulation, and the allowable voltage change threshold of the electric bridge is converted;the longitudinal force electric bridge output is monitored in real time during machining, and if the threshold is exceeded, the depth of cut is reduced.The method relies on the strain electric bridge to realize the monitoring and feedback of clamping and cutting force, effectively suppresses the bending and twisting deformation of the thin plate, and improves the machining precision and yield of the aviation thin plate parts.

Description

Technical Field

[0001] This invention belongs to the field of aerospace aerodynamic test model processing and manufacturing technology, and particularly relates to a method for controlling deformation during the processing of thin plate-shaped parts based on bridge monitoring. Background Technology

[0002] Thin-plate parts, with their large length-to-diameter ratio and poor rigidity, are highly susceptible to deformation during machining due to clamping stress, cutting forces, and residual stress release, resulting in bending, warping, and bulging. Clamping is the primary cause of deformation in the machining of thin-plate parts; the vast majority of deformations are caused by clamping stress. Excessive clamping force can cause the part to bend, resulting in springback and warping after machining is completed and the parts are released. Insufficient clamping force leads to vibration during cutting, producing chatter marks and machining errors. Cutting force is also a direct cause of deformation during machining; excessive cutting force can cause the part to bend, resulting in elastic deformation. The airfoil in a wind tunnel test model is a typical example of a thin-plate part, often resulting in out-of-tolerance scrapping or poor test data quality due to machining deformation. Summary of the Invention

[0003] The purpose of this invention is to provide a method for controlling deformation during the machining of thin plate-shaped parts based on bridge monitoring, in order to solve the problem of deformation of thin plate-shaped parts due to clamping and cutting. The technical solution adopted by this invention is as follows:

[0004] A method for controlling deformation during machining of thin plate-shaped parts based on bridge monitoring includes the following steps:

[0005] Step 1: Select a sheet metal with a thickness greater than that of the thin plate-shaped part as the processing substrate. Cut the processing substrate to form a part body that matches the contour of the thin plate-shaped part, and several process support blocks distributed around the part body. Several rectangular protrusions are retained on the outer periphery of the part body. The rectangular protrusions and the process support blocks are connected one-to-one by the retained connecting ribs. Rectangular grooves are processed on the upper and lower sides of each connecting rib, so that the connecting ribs between each pair of rectangular grooves form a rectangular measuring beam. The part body, the several process support blocks, and the connection between the part body and the process support blocks form the blank of the thin plate-shaped part.

[0006] Step 2: Attach strain gauges to the rectangular measuring beam and assemble them into a longitudinal force measuring bridge, a transverse force measuring bridge, and a rolling force measuring bridge;

[0007] Step 3: Place the blank freely on the machining platform of the machine tool and record the zero-point data of the longitudinal force measuring bridge, transverse force measuring bridge and rolling force measuring bridge of all rectangular measuring beams;

[0008] Step 4: Fix the blank on the processing platform;

[0009] Step 5: Using the longitudinal deformation angle of the part body as input, perform simulation calculations to obtain the tensile stress values ​​of the upper and lower end faces of each rectangular measuring beam under the maximum permissible bending deformation error;

[0010] Step 6: Compare the calculation results of Step 5, and take the smallest of the tensile stress values ​​of the upper and lower ends of all rectangular measuring beams as the maximum allowable cutting stress for subsequent machining of the part body.

[0011] Step 7: Based on the maximum allowable cutting stress, combined with the material's elastic modulus, the strain gauge's sensitivity coefficient, and the bridge excitation voltage, calculate the allowable change in strain voltage of the longitudinal force measurement bridge.

[0012] Step 8: Collect the zero-point value of the longitudinal force measurement bridge of each rectangular measuring beam as a reference, and record the actual change of strain voltage of each longitudinal force measurement bridge in real time as a reference for cutting control.

[0013] Step 9: Begin machining the thin plate-shaped part. When the actual change in strain voltage of each longitudinal force measuring bridge is less than or equal to the corresponding allowable change in strain voltage, proceed with normal machining. When the actual change in strain voltage of each longitudinal force measuring bridge is greater than the corresponding allowable change in strain voltage, reduce the depth of cut of the machine tool until the actual change in strain voltage of each longitudinal force measuring bridge is less than or equal to the corresponding allowable change in strain voltage.

[0014] Furthermore, the specific steps of step two are as follows:

[0015] The strain gauges include a first strain gauge, a second strain gauge, a third strain gauge, a fourth strain gauge, a fifth strain gauge, a sixth strain gauge, a seventh strain gauge, an eighth strain gauge, a ninth strain gauge, a tenth strain gauge, an eleventh strain gauge, and a twelfth strain gauge;

[0016] The first strain gauge and the third strain gauge are attached to the two ends of the upper end face of the rectangular measuring beam along the longitudinal direction, and the second strain gauge and the fourth strain gauge are attached to the two ends of the lower end face of the rectangular measuring beam along the longitudinal direction. The first strain gauge, the third strain gauge, the fourth strain gauge and the second strain gauge form a longitudinal force measuring bridge.

[0017] The fifth and seventh strain gauges are attached to the longitudinal ends of one side of the rectangular measuring beam, and the sixth and eighth strain gauges are attached to the longitudinal ends of the other side of the rectangular measuring beam. The fifth, sixth, eighth and seventh strain gauges form a transverse force measuring bridge.

[0018] The ninth and eleventh strain gauges are attached to the middle of one side of the rectangular measuring beam, and the tenth and twelfth strain gauges are attached to the middle of the other side of the rectangular measuring beam. The ninth, tenth, twelfth and eleventh strain gauges form a rolling force measuring bridge.

[0019] Furthermore, the specific steps of step four are as follows:

[0020] Several clamping devices are respectively connected to the processing platform by bolts, so that several process support blocks are pressed and fixed on the processing platform in a one-to-one correspondence between the clamping devices, and the voltage change of the longitudinal force measuring bridge, transverse force measuring bridge and rolling force measuring bridge of all rectangular measuring beams is less than or equal to 0.1mV. If the voltage change exceeds 0.1mV, the position of the clamping device is adjusted until the voltage change is less than or equal to 0.1mV.

[0021] Furthermore, the specific steps of step five are as follows:

[0022] The computer simulation calculation uses the longitudinal deformation angle of the part body as the input and the tensile stress value of each rectangular measuring beam as the output. The calculation is performed on the upper and lower end faces of each rectangular measuring beam when the upper end face of the part body is cut, under the maximum permissible bending deformation error of the part body.

[0023] Furthermore, the specific steps of step seven are as follows:

[0024] Based on the maximum allowable cutting stress selected in step six, calculate the allowable change in strain voltage of each longitudinal force measuring bridge. The calculation formula is as follows:

[0025] ;

[0026] In the formula, ΔU is the allowable variation of the strain voltage of the longitudinal force measuring bridge, K is the sensitivity coefficient of the first strain gauge, the third strain gauge, the fourth strain gauge and the second strain gauge, ε1 is the micro-strain at the bonding position of the first strain gauge, ε2 is the micro-strain at the bonding position of the second strain gauge, ε3 is the micro-strain at the bonding position of the third strain gauge, ε4 is the micro-strain at the bonding position of the fourth strain gauge, and U is the excitation voltage of the longitudinal force measuring bridge.

[0027] ε1, ε2, ε3 and ε4 are calculated using the following four formulas:

[0028] ;

[0029] ;

[0030] ;

[0031] ;

[0032] In the formula, E is the elastic modulus of the material, σ1 is the tensile stress value at the first strain gauge bonding position, σ2 is the tensile stress value at the second strain gauge bonding position, σ3 is the tensile stress value at the third strain gauge bonding position, and σ4 is the tensile stress value at the fourth strain gauge bonding position.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] This invention monitors the forces acting on the clamping and machining of thin plate-shaped parts by setting up an electric bridge, guiding the clamping and machining feed, providing a quantitative reference for the machining process, and controlling the deformation of the thin plate-shaped parts by controlling the clamping force and cutting force, thereby improving machining accuracy and efficiency. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a clamping device fixing a blank of a thin plate-shaped part;

[0036] Figure 2 This is a schematic diagram showing the strain gauge mounting positions on the longitudinal force measurement bridge;

[0037] Figure 3 This is a schematic diagram showing the strain gauge mounting positions of the transverse force measurement bridge and the roll force measurement bridge;

[0038] Figure 4 This is the bridge circuit diagram of the longitudinal force measurement bridge;

[0039] Figure 5 This is the bridge circuit diagram of the Wheatstone bridge for measuring lateral force;

[0040] Figure 6 This is the circuit diagram of the Wheatstone bridge for measuring rolling force.

[0041] In the figure, 1. Process support block, 2. Part body, 3. Rectangular measuring beam, 4. Rectangular protrusion, 5. Rectangular groove, 6. Connecting rib, 7. Clamping device, R1. First strain gauge, R2. Second strain gauge, R3. Third strain gauge, R4. Fourth strain gauge, R5. Fifth strain gauge, R6. Sixth strain gauge, R7. Seventh strain gauge, R8. Eighth strain gauge, R9. Ninth strain gauge, R10. Tenth strain gauge, R11. Eleventh strain gauge, R12. Twelfth strain gauge. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0043] The connections mentioned in this invention are divided into fixed connections and detachable connections. Fixed connections, also known as non-detachable connections, include but are not limited to conventional fixed connection methods such as folded connections, riveted connections, adhesive connections, and welded connections. Detachable connections include but are not limited to conventional disassembly methods such as bolted connections, snap-fit ​​connections, pin connections, and hinged connections. When a specific connection method is not explicitly defined, it is assumed that at least one existing connection method can be found to achieve this function, and those skilled in the art can choose according to their needs. For example, a welded connection can be chosen for fixed connections, and a bolted connection can be chosen for detachable connections.

[0044] The present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0045] Example: Figures 1-6 As shown, a method for controlling deformation during machining of thin plate-shaped parts based on bridge monitoring includes the following steps:

[0046] Step 1: Select a sheet metal with a thickness greater than that of the thin plate-shaped part as the processing substrate. Cut the processing substrate to form a part body 2 that matches the contour of the thin plate-shaped part, and a number of process support blocks 1 distributed around the part body 2. Several rectangular protrusions 4 are retained on the outer periphery of the part body 2. The several rectangular protrusions 4 and the several process support blocks 1 are connected one-to-one by the retained connecting ribs 6. Rectangular grooves 5 are processed on the upper and lower sides of each connecting rib 6, so that the connecting ribs 6 between each pair of rectangular grooves 5 form a rectangular measuring beam 3. The part body 2, the several process support blocks 1 and the connection part between the part body 2 and the process support blocks 1 form the blank of the thin plate-shaped part.

[0047] Step 2: Attach the first strain gauge R1 and the third strain gauge R3 to the two ends of the upper longitudinal direction of the rectangular measuring beam 3, and attach the second strain gauge R2 and the fourth strain gauge R4 to the two ends of the lower longitudinal direction of the rectangular measuring beam 3. The first strain gauge R1, the third strain gauge R3, the fourth strain gauge R4 and the second strain gauge R2 form a longitudinal force measuring bridge.

[0048] The fifth strain gauge R5 and the seventh strain gauge R7 are attached to the two ends of the longitudinal direction on one side of the rectangular measuring beam 3, and the sixth strain gauge R6 and the eighth strain gauge R8 are attached to the two ends of the longitudinal direction on the other side of the rectangular measuring beam 3. The fifth strain gauge R5, the sixth strain gauge R6, the eighth strain gauge R8 and the seventh strain gauge R7 form a transverse force measuring bridge.

[0049] The ninth strain gauge R9 and the eleventh strain gauge R11 are attached to the middle of one side of the rectangular measuring beam 3, and the tenth strain gauge R10 and the twelfth strain gauge R12 are attached to the middle of the other side of the rectangular measuring beam 3. The ninth strain gauge R9, the tenth strain gauge R10, the twelfth strain gauge R12 and the eleventh strain gauge R11 form a rolling force measuring bridge.

[0050] Step 3: Place the blank freely on the machining platform of the machine tool and record the zero-point data of the longitudinal force measuring bridge, transverse force measuring bridge and rolling force measuring bridge of all rectangular measuring beams 3;

[0051] Step 4: Connect several clamping devices 7 to the processing platform with bolts, so that the clamping devices 7 correspond one-to-one with the process support blocks 1 and press them firmly on the processing platform. Ensure that the voltage change of the longitudinal force measuring bridge, transverse force measuring bridge and rolling force measuring bridge of all rectangular measuring beams 3 is less than or equal to 0.1mV. If the voltage change exceeds 0.1mV, adjust the position of the clamping devices 7 until the voltage change is less than or equal to 0.1mV, thereby eliminating the over-constraint.

[0052] Step 5: Perform simulation calculations using a computer, taking the longitudinal deformation angle of the part body 2 as the input and the tensile stress value of each rectangular measuring beam 3 as the output, to calculate the tensile stress value of the upper end face and the tensile stress value of the lower end face of each rectangular measuring beam 3 under the maximum permissible bending deformation error of the part body 2 when cutting the upper end face of the part body 2.

[0053] Step 6: Compare the calculation results of Step 5, and take the smallest of the upper end tensile microstrain and lower end tensile microstrain of all rectangular measuring beams 3 as the maximum allowable cutting stress for subsequent machining of the part body 2.

[0054] Step 7: Based on the maximum allowable cutting stress selected in Step 6, calculate the allowable change in strain voltage of each longitudinal force measuring bridge. The calculation formula is as follows:

[0055] ;

[0056] In the formula, ΔU is the allowable variation of the strain voltage of the longitudinal force measuring bridge, K is the sensitivity coefficient of the first strain gauge R1, the third strain gauge R3, the fourth strain gauge R4 and the second strain gauge R2, ε1 is the micro-strain at the bonding position of the first strain gauge R1, ε2 is the micro-strain at the bonding position of the second strain gauge R2, ε3 is the micro-strain at the bonding position of the third strain gauge R3, ε4 is the micro-strain at the bonding position of the fourth strain gauge R4, the strain value is positive for tension and negative for compression, and U is the excitation voltage of the longitudinal force measuring bridge.

[0057] ε1, ε2, ε3 and ε4 are calculated using the following four formulas:

[0058] ;

[0059] ;

[0060] ;

[0061] ;

[0062] In the formula, E is the elastic modulus of the material, σ1 is the tensile stress value at the bonding position of the first strain gauge R1, σ2 is the tensile stress value at the bonding position of the second strain gauge R2, σ3 is the tensile stress value at the bonding position of the third strain gauge R3, and σ4 is the tensile stress value at the bonding position of the fourth strain gauge R4.

[0063] Step 8: Collect the zero-point value of the longitudinal force measurement bridge of each rectangular measuring beam 3 as a reference, and record the actual change of strain voltage of each longitudinal force measurement bridge in real time as a reference for cutting control.

[0064] Step 9: Begin machining the thin plate-shaped part. When the actual change in strain voltage of each longitudinal force measuring bridge is less than or equal to the corresponding allowable change in strain voltage, proceed with normal machining. When the actual change in strain voltage of each longitudinal force measuring bridge is greater than the corresponding allowable change in strain voltage, reduce the depth of cut of the machine tool until the actual change in strain voltage of each longitudinal force measuring bridge is less than or equal to the corresponding allowable change in strain voltage.

[0065] This invention is primarily used for the fabrication of aerospace aerodynamic test models. A longitudinal force measuring bridge, a transverse force measuring bridge, and a rolling force measuring bridge are installed on a rectangular measuring beam 3. The clamping is adjusted based on the output signals of each bridge, controlling the clamping force and avoiding over-constraint. The cutting depth is adjusted by the output signals of each longitudinal force measuring bridge. This reduces deformation caused by clamping and cutting thin-plate parts, controlling the cutting deformation of thin-plate parts and improving machining accuracy.

[0066] The above embodiments are merely illustrative examples of the present invention and do not limit its scope of protection. Those skilled in the art can make partial changes to them, as long as they do not exceed the spirit and essence of the present invention, they are all within the scope of protection of the present invention.

Claims

1. A method for controlling deformation during machining of thin plate-shaped parts based on bridge monitoring, characterized in that, Includes the following steps: Step 1: Select a plate with a thickness greater than that of the thin plate-shaped part as the processing substrate, cut the processing substrate to form a part body (2) that matches the outline of the thin plate-shaped part, and a number of process support blocks (1) distributed around the part body (2). Several rectangular protrusions (4) are retained on the outer periphery of the part body (2). The several rectangular protrusions (4) and the several process support blocks (1) are connected one-to-one by the retained connecting ribs (6). Rectangular grooves (5) are processed on the upper and lower sides of each connecting rib (6) so that the connecting ribs (6) between each pair of rectangular grooves (5) form a rectangular measuring beam (3). The part body (2), the several process support blocks (1) and the connection between the part body (2) and the process support blocks (1) form the blank of the thin plate-shaped part. Step 2: Attach strain gauges to the rectangular measuring beam (3) and form a longitudinal force measuring bridge, a transverse force measuring bridge and a rolling force measuring bridge; Step 3: Place the blank freely on the processing platform of the machine tool and record the zero-point data of the longitudinal force measuring bridge, transverse force measuring bridge and rolling force measuring bridge of all rectangular measuring beams (3); Step 4: Fix the blank on the processing platform; Step 5: Using the longitudinal deformation angle of the part body as input, perform simulation calculations to obtain the tensile stress values ​​of the upper and lower end faces of each rectangular measuring beam under the maximum permissible bending deformation error; Step 6: Compare the calculation results of Step 5, and take the smallest of the upper end tensile stress value and the lower end tensile stress value of all rectangular measuring beams (3) as the maximum allowable cutting stress for subsequent machining of the part body (2). Step 7: Based on the maximum allowable cutting stress, combined with the material's elastic modulus, the strain gauge's sensitivity coefficient, and the bridge excitation voltage, calculate the allowable change in strain voltage of the longitudinal force measurement bridge. Step 8: Collect the zero point value of the longitudinal force measurement bridge of each rectangular measuring beam (3) as a reference, and record the actual change of strain voltage of each longitudinal force measurement bridge in real time as a reference for cutting control. Step 9: Begin machining the thin plate-shaped part. When the actual change in strain voltage of each longitudinal force measuring bridge is less than or equal to the corresponding allowable change in strain voltage, proceed with normal machining. When the actual change in strain voltage of each longitudinal force measuring bridge is greater than the corresponding allowable change in strain voltage, reduce the depth of cut of the machine tool until the actual change in strain voltage of each longitudinal force measuring bridge is less than or equal to the corresponding allowable change in strain voltage.

2. The method for controlling deformation during machining of thin plate-shaped parts based on bridge monitoring according to claim 1, characterized in that, The specific steps for step two are as follows: The strain gauges include a first strain gauge (R1), a second strain gauge (R2), a third strain gauge (R3), a fourth strain gauge (R4), a fifth strain gauge (R5), a sixth strain gauge (R6), a seventh strain gauge (R7), an eighth strain gauge (R8), a ninth strain gauge (R9), a tenth strain gauge (R10), an eleventh strain gauge (R11), and a twelfth strain gauge (R12). The first strain gauge (R1) and the third strain gauge (R3) are attached to the two ends of the upper end face of the rectangular measuring beam (3) along the longitudinal direction, and the second strain gauge (R2) and the fourth strain gauge (R4) are attached to the two ends of the lower end face of the rectangular measuring beam (3) along the longitudinal direction. The first strain gauge (R1), the third strain gauge (R3), the fourth strain gauge (R4) and the second strain gauge (R2) form a longitudinal force measuring bridge. The fifth strain gauge (R5) and the seventh strain gauge (R7) are attached to the two ends of the longitudinal direction on one side of the rectangular measuring beam (3), and the sixth strain gauge (R6) and the eighth strain gauge (R8) are attached to the two ends of the longitudinal direction on the other side of the rectangular measuring beam (3). The fifth strain gauge (R5), the sixth strain gauge (R6), the eighth strain gauge (R8) and the seventh strain gauge (R7) form a transverse force measuring bridge. The ninth strain gauge (R9) and the eleventh strain gauge (R11) are attached to the middle of one side of the rectangular measuring beam (3), and the tenth strain gauge (R10) and the twelfth strain gauge (R12) are attached to the middle of the other side of the rectangular measuring beam (3). The ninth strain gauge (R9), the tenth strain gauge (R10), the twelfth strain gauge (R12) and the eleventh strain gauge (R11) form a rolling force measuring bridge.

3. The method for controlling deformation during machining of thin plate-shaped parts based on bridge monitoring according to claim 1, characterized in that, The specific steps for step four are as follows: Several clamping devices (7) are respectively connected to the processing platform by bolts, so that several clamping devices (7) correspond one-to-one to press and fix several process support blocks (1) on the processing platform, and ensure that the voltage change of the longitudinal force measuring bridge, transverse force measuring bridge and rolling force measuring bridge of all rectangular measuring beams (3) is less than or equal to 0.1mV. If the voltage change exceeds 0.1mV, the position of the clamping device (7) is adjusted until the voltage change is less than or equal to 0.1mV.

4. The method for controlling deformation during machining of thin plate-shaped parts based on bridge monitoring according to claim 1, characterized in that, The specific steps for step five are as follows: The computer simulation calculation uses the longitudinal deformation angle of the part body (2) as the input and the tensile stress value of each rectangular measuring beam (3) as the output. The calculation is performed on the upper end face and the lower end face of each rectangular measuring beam (3) under the maximum permissible bending deformation error of the part body (2) when the upper end face of the part body (2) is cut.

5. The method for controlling deformation during machining of thin plate-shaped parts based on bridge monitoring according to claim 1, characterized in that, The specific steps for step seven are as follows: Based on the maximum allowable cutting stress selected in step six, calculate the allowable change in strain voltage of each longitudinal force measuring bridge. The calculation formula is as follows: ； In the formula, ΔU is the allowable variation of the strain voltage of the longitudinal force measuring bridge, K is the sensitivity coefficient of the first strain gauge (R1), the third strain gauge (R3), the fourth strain gauge (R4) and the second strain gauge (R2), ε1 is the micro-strain at the bonding position of the first strain gauge (R1), ε2 is the micro-strain at the bonding position of the second strain gauge (R2), ε3 is the micro-strain at the bonding position of the third strain gauge (R3), ε4 is the micro-strain at the bonding position of the fourth strain gauge (R4), and U is the excitation voltage of the longitudinal force measuring bridge. ε1, ε2, ε3 and ε4 are calculated using the following four formulas: ； ； ； ； In the formula, E is the elastic modulus of the material, σ1 is the tensile stress value at the bonding position of the first strain gauge (R1), σ2 is the tensile stress value at the bonding position of the second strain gauge (R2), σ3 is the tensile stress value at the bonding position of the third strain gauge (R3), and σ4 is the tensile stress value at the bonding position of the fourth strain gauge (R4).

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