Combined clamping method for ceramic matrix composite segmented cylindrical structure

Abstract

The invention belongs to the field of aero-engine part clamping, and particularly relates to a combined clamping method for a ceramic matrix composite segmented cylindrical structure, which comprises the following steps of: firstly, clamping a workpiece, and connecting a lower rib plate of the workpiece with a positioning reference surface of a clamp by using two groups of positioning pins; then, the lower pressing plate, the workpiece lower rib plate and the clamp positioning datum plane are clamped and fixed through bolts, pointers of the two dial indicators abut against the inner wall face, between the workpiece upper rib plate and the workpiece lower rib plate, of the workpiece, and the initial reading of the dial indicators is zero; two sets of combined positioning pins penetrate through an upper pressing plate, a pin hole I in an upper rib plate of a workpiece and an upper supporting plate to be clamped and fixed, in the process, a supporting base is repeatedly adjusted to be connected with a bolt of the upper pressing plate, it is guaranteed that under the state that the workpiece is clamped, the change of the micrometer indication does not exceed the limiting value, and it is indicated that clamping of the workpiece is completed; and the steps are repeated to complete clamping of the whole cylindrical structure. Through the method, the machining deformation of the cylindrical structure is effectively relieved, and the machining precision is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the field of aerospace engine parts clamping, and in particular relates to a combined clamping method for a ceramic-based composite material segmented cylindrical structure. Background Art

[0002] As the temperature requirements of aircraft engines continue to increase, ceramic-based composite components are gradually used in hot-end components. The cylindrical structure of aircraft engines is common in casing parts. In order to increase its operating temperature, ceramic-based composites are used. Due to the hard, brittle, and heterogeneous characteristics of ceramic-based composites, large-size molding is difficult, so they need to be formed and processed in sections. The use of segmented processing will result in height differences after the sections are spliced, which cannot meet the use requirements. Segmented processing means that the parts are not combined and processed individually; and the conventional combined processing method is still difficult to achieve high-precision processing due to problems such as repeated clamping and workpiece deformation. Therefore, it is necessary to design a combined clamping method for segmented cylindrical structures of ceramic-based composite materials to solve the processing problems of cylindrical structures of ceramic-based composite materials. Summary of the invention

[0003] In view of the deficiencies in the prior art, the object of the present invention is to provide a combined clamping method for a ceramic matrix composite segmented cylindrical structure, so as to achieve high-precision machining of ceramic matrix composite parts.

[0004] A combined clamping method for a ceramic matrix composite segmented cylindrical structure comprises the following steps:

[0005] Step 1: First, clamp a workpiece, set a lower pressure plate above the lower rib of the workpiece, use the lower pressure plate to fit the lower rib of the workpiece with the positioning reference surface of the fixture, and use two sets of positioning pins to connect the lower rib of the workpiece with the positioning reference surface of the fixture to limit the horizontal movement of the lower rib of the workpiece;

[0006] Step 2: Use bolts to clamp and fix the lower pressure plate, the lower rib of the workpiece, and the fixture positioning reference surface, so that the lower rib of the workpiece is in a clamped state and the vertical movement of the lower rib of the workpiece is restricted;

[0007] Step 3: Install two magnetic gauge seats inside the fixture, and the pointer of the micrometer on the magnetic gauge seat is against the inner wall of the workpiece between the upper rib plate and the lower rib plate of the workpiece. The initial reading of the micrometer is zero;

[0008] Step 4: Install the upper pressing plate on the upper part of the upper rib of the workpiece, a support plate is provided below the upper rib of the workpiece, a support seat is provided between the upper pressing plate and the fixture, and the upper pressing plate and the support seat, as well as the fixture and the support seat are fixed by bolts respectively; use two sets of combined positioning pins to penetrate the upper pressing plate, the pin hole I on the upper rib of the workpiece and the upper support plate for clamping and fixing. During this process, repeatedly adjust the bolts connecting the support seat to the upper pressing plate to ensure that when the workpiece is clamped, the change in the thousandth indication value does not exceed the limit value, indicating that one workpiece is clamped;

[0009] Step 5, repeat steps 1 to 4 to complete the clamping of other workpieces on the fixture, thereby completing the clamping of the entire cylindrical structure;

[0010] Step 6: Use the clamping fixture of the cylindrical structure completed in step 5 to carry out processing tests.

[0011] In the step 1, the flatness of the fixture positioning reference surface is not greater than 0.02 mm.

[0012] In step 1, two groups of pin holes II are provided on the lower rib plate of the workpiece, and the positioning pins and the pin holes II are connected to the lower pressure plate and the lower rib plate of the workpiece by a clearance fit method, and the positioning accuracy of the positioning pins is not greater than 0.02mm; the clearance between the positioning pins and the pin holes II is less than 0.05mm.

[0013] In step 2, the clamping force torque acting on the bolt is no more than 5 MPa.

[0014] In step 4, the upper edge of the support seat is flush with the upper edge of the rib plate on the workpiece.

[0015] In step 4, the combined locating pin is a combined structure of a top locating pin and a bottom bolt, the top locating pin connects the upper pressure plate and the upper rib plate of the workpiece, and the bottom bolt is tightened in the support plate, so that the upper rib plate of the workpiece and the upper pressure plate and the support plate can achieve both horizontal and vertical limiting; the top locating pin and the pin hole I are also clearance-matched, and the position accuracy of the top locating pin is not greater than 0.02mm; the clearance between the locating pin and the pin hole I is less than 0.05mm.

[0016] In step 4, the limit value of the thousandth indication is 0.005 mm.

[0017] In step 6, the dimensional accuracy and run-out of the workpiece after processing are less than 0.04 mm; the change in dimensional accuracy and run-out after repeated clamping is less than 0.005 mm.

[0018] In the step 1, a copper foil is provided between the lower rib plate and the lower pressing plate of the workpiece, and the thickness of the copper foil is not less than 0.5 mm.

[0019] The upper pressing plate, the supporting plate and the lower pressing plate are provided with chamfers facing the workpiece side.

[0020] The beneficial effects of the present invention are as follows:

[0021] By using the invented combined processing tooling for the segmented cylindrical structure of ceramic-based composite materials, the processing deformation of the cylindrical structure is effectively alleviated, and the processing accuracy is significantly improved. After processing, the inner wall runout error of the cylindrical structure of ceramic-based composite materials is no more than 0.05mm, which meets the product use requirements. Through the above method, the process route of grinding the coating on the aircraft engine is avoided, and the assembly efficiency is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of a ceramic matrix composite material segmented cylindrical structure workpiece;

[0023] Figure 2 It is a top view of the combined processing tooling for the segmented cylindrical structure of the ceramic matrix composite material without the upper pressing plate installed;

[0024] Figure 3 It is a schematic diagram of the clamping of the combined processing tooling and workpiece of the segmented cylindrical structure of the ceramic matrix composite material;

[0025] Among them, 1. fixture; 2. workpiece; 3. support seat; 4. lower pressure plate; 5. positioning pin; 6. fixture positioning reference surface; 7. upper pressure plate; 8. support plate; 9. lower rib plate of workpiece; 10. upper rib plate of workpiece. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below with reference to the accompanying drawings.

[0027] like Figures 1 to 3 As shown, a combined clamping method for a ceramic matrix composite segmented cylindrical structure comprises the following steps:

[0028] Step 1: First, clamp a workpiece 2, set a lower pressing plate 4 above the lower rib plate 9 of the workpiece, and set a copper foil between the lower rib plate 9 of the workpiece and the lower pressing plate 4, and the thickness of the copper foil is not less than 0.5mm; use the lower pressing plate 4 to fit the lower rib plate 9 of the workpiece with the positioning reference surface 6 of the fixture, and the positioning reference of the lower rib plate 9 of the workpiece is Correspondingly, a workpiece positioning reference is machined on the fixture 1 The matching fixture positioning reference surface 6 has high precision requirements. The overall plane processing of the fixture 1 is very likely to cause deformation of the workpiece. The fixture positioning reference surface 6 is a small boss surface processed on the fixture 1. The flatness of the fixture positioning reference surface 6 is not greater than 0.02 mm. In this embodiment, the flatness of the fixture positioning reference surface 6 is 0.01 mm; two groups of pin holes II are provided on the lower rib plate 9 of the workpiece, and two groups of positioning pins 5 are used to pass through the two groups of pin holes II on the lower rib plate 9 of the workpiece and connect with the fixture positioning reference surface 6 to limit the horizontal movement of the lower rib plate 9 of the workpiece. The positioning pins 5 and the pin holes II are clearance-matched, and the position of the positioning pins 5 is not greater than 0.02 mm; the clearance between the positioning pins 5 and the pin holes II is less than 0.05 mm;

[0029] Step 2: Use a torque wrench to clamp and fix the lower pressure plate 4, the lower rib plate 9 of the workpiece, and the fixture positioning reference surface 6 on the bolts, so that the lower rib plate 9 of the workpiece is in a clamped state, and the vertical movement of the lower rib plate 9 of the workpiece is restricted; the clamping force torque acting on the bolts is not greater than 5MPa, which is 5MPa in this embodiment;

[0030] Step 3: Install two magnetic gauge bases inside the fixture 1, and place the pointer of the micrometer on the magnetic gauge base against the inner wall of the workpiece between the upper rib 10 and the lower rib 9 of the workpiece. The initial reading of the micrometer is zero.

[0031] Step 4: Install the upper pressing plate 7 on the upper part of the upper rib 10 of the workpiece, a support plate 8 is provided below the upper rib 10 of the workpiece, a support seat 3 is provided between the upper pressing plate 7 and the fixture 1, and the upper pressing plate 7 and the support seat 3, the fixture 1 and the support seat 3 are respectively fixed by bolts; use two sets of combined positioning pins to penetrate the upper pressing plate 7, the pin holes I of the upper rib 10 of the workpiece and the upper support plate 8 for clamping and fixing. In this process, repeatedly adjust the bolts connecting the support seat 3 to the upper pressing plate 7 to ensure that when the workpiece 2 is clamped, the change in the millimeter reading does not exceed 0.005mm, indicating that one workpiece is clamped;

[0032] The combined positioning pin is a combination structure of a top positioning pin and a bottom bolt. The top positioning pin connects the upper pressure plate 7 and the upper rib plate 10 of the workpiece. The bottom bolt is tightened in the support plate 8, so that the upper rib plate 10 of the workpiece and the upper pressure plate 7 and the support plate 8 can achieve both horizontal and vertical limit. The top positioning pin and the pin hole I are also clearance-matched, and the position accuracy of the top positioning pin is not greater than 0.02mm; the clearance between the positioning pin and the pin hole I is less than 0.05mm;

[0033] Step 5, repeat steps 1 to 4 to complete the clamping of other workpieces on the fixture, thereby completing the clamping of the entire cylindrical structure;

[0034] Step 6: Use the clamping fixture of the cylindrical structure completed in step 5 to carry out processing tests. The dimensional accuracy and run-out of the workpiece after processing are less than 0.04mm; the processing accuracy meets the design requirements of the drawing, and the change in dimensional accuracy and run-out after repeated clamping is less than 0.005mm.

[0035] In this embodiment, the upper pressing plate 7 , the supporting plate 8 , and the lower pressing plate 4 are chamfered toward the workpiece 2 .

[0036] The present invention adopts an over-positioning method to limit the freedom of the workpiece in order to ensure effective positioning and clamping of the workpiece in the actual assembly state; in the clamping process, it is necessary to avoid over-positioning to prevent deformation of the workpiece and thus cause the workpiece size to exceed the tolerance. The upper rib plate 10 of the workpiece and the lower rib plate 9 of the workpiece adopt a clamping method of two pins on one side, and the bolts of the upper pressure plate, the fixture and the support seat are only involved in clamping.

[0037] According to the hard, brittle and heterogeneous characteristics of ceramic-based composite materials, the present invention connects the lower pressure plate 4 and the lower rib 9 of the workpiece through two groups of locating pins, and tightens them with bolts. The upper rib 10 of the workpiece is connected to the upper pressure plate 7 and the support plate 8 through combined locating pins. To prevent over-positioning, the present invention adjusts the tightening force of the bolts between the upper pressure plate 7 and the support seat 3, thereby facilitating the adjustment of the position and tightening force of the upper pressure plate 7 and the upper rib 10 of the workpiece, and uses a micrometer to assist, thereby preventing excessive clamping and causing deformation of the workpiece 2; at the same time, to prevent the lower pressure plate 4 from damaging the surface of the lower rib 9 of the workpiece and to ensure that the lower rib 9 of the workpiece is in good contact with the fixture positioning reference surface 6, copper foil is provided between the lower pressure plate 4 and the lower rib 9 of the workpiece.

Claims

1. A combined clamping method for a ceramic matrix composite segmented cylindrical structure, characterized in that: The following steps are involved: Step 1: First, clamp a workpiece, set a lower pressure plate above the lower rib of the workpiece, use the lower pressure plate to fit the lower rib of the workpiece with the positioning reference surface of the fixture, and use two sets of positioning pins to connect the lower rib of the workpiece with the positioning reference surface of the fixture to limit the horizontal movement of the lower rib of the workpiece; Step 2: Use bolts to clamp and fix the lower pressure plate, the lower rib of the workpiece, and the fixture positioning reference surface, so that the lower rib of the workpiece is in a clamped state and the vertical movement of the lower rib of the workpiece is restricted; Step 3: Install two magnetic gauge seats inside the fixture, and the pointer of the micrometer on the magnetic gauge seat is against the inner wall of the workpiece between the upper rib plate and the lower rib plate of the workpiece. The initial reading of the micrometer is zero; Step 4: Install the upper pressing plate on the upper part of the upper rib of the workpiece, a support plate is provided below the upper rib of the workpiece, a support seat is provided between the upper pressing plate and the fixture, and the upper pressing plate and the support seat, as well as the fixture and the support seat are fixed by bolts respectively; use two sets of combined positioning pins to penetrate the upper pressing plate, the pin hole I on the upper rib of the workpiece and the upper support plate for clamping and fixing. During this process, repeatedly adjust the bolts connecting the support seat to the upper pressing plate to ensure that when the workpiece is clamped, the change in the thousandth indication value does not exceed the limit value, indicating that one workpiece is clamped; Step 5, repeat steps 1 to 4 to complete the clamping of other workpieces on the fixture, thereby completing the clamping of the entire cylindrical structure; Step 6: Use the clamping fixture of the cylindrical structure completed in step 5 to carry out processing tests.

2. A combined clamping method for a ceramic matrix composite segmented cylindrical structure according to claim 1, characterized in that: In the step 1, the flatness of the fixture positioning reference surface is not greater than 0.02 mm.

3. The combined clamping method for a ceramic matrix composite segmented cylindrical structure according to claim 1, characterized in that: In step 1, two groups of pin holes II are provided on the lower rib plate of the workpiece, and the positioning pins and the pin holes II are connected to the lower pressure plate and the lower rib plate of the workpiece by a clearance fit method, and the positioning accuracy of the positioning pins is not greater than 0.02mm; the clearance between the positioning pins and the pin holes II is less than 0.05mm.

4. The combined clamping method for a ceramic matrix composite segmented cylindrical structure according to claim 1, characterized in that: In the step 1, a copper foil is provided between the lower rib plate and the lower pressing plate of the workpiece, and the thickness of the copper foil is not less than 0.5 mm.

5. The combined clamping method for a ceramic matrix composite segmented cylindrical structure according to claim 1, characterized in that: In step 2, the clamping force torque acting on the bolt is no more than 5 MPa.

6. The combined clamping method for a ceramic matrix composite segmented cylindrical structure according to claim 1, characterized in that: In step 4, the upper edge of the support seat is flush with the upper edge of the rib plate on the workpiece.

7. The combined clamping method for a ceramic matrix composite segmented cylindrical structure according to claim 1, characterized in that: In step 4, the combined locating pin is a combined structure of a top locating pin and a bottom bolt, the top locating pin connects the upper pressure plate and the upper rib plate of the workpiece, and the bottom bolt is tightened in the support plate, so that the upper rib plate of the workpiece and the upper pressure plate and the support plate can achieve both horizontal and vertical limiting; the top locating pin and the pin hole I are also clearance-matched, and the position accuracy of the top locating pin is not greater than 0.02mm; the clearance between the locating pin and the pin hole I is less than 0.05mm.

8. The combined clamping method for a ceramic matrix composite segmented cylindrical structure according to claim 1, characterized in that: In step 4, the limit of the thousandth indication is 0.005 mm.

9. The combined clamping method for a ceramic matrix composite segmented cylindrical structure according to claim 1, characterized in that: In step 6, the dimensional accuracy and run-out of the workpiece after processing are less than 0.04 mm; the change in dimensional accuracy and run-out after repeated clamping is less than 0.005 mm.

10. The combined clamping method for a ceramic matrix composite segmented cylindrical structure according to claim 1, characterized in that: The upper pressing plate, the supporting plate and the lower pressing plate are provided with chamfers facing the workpiece side.

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