A method for testing the strength of small-sized surfaces using ultrasonic shot peening

Abstract

The present invention belongs to the technical field of metal workpiece surface strengthening, and relates to a method for ultrasonic shot peening strength testing of small-sized profiles, comprising: cutting a micro-test piece from a standard test piece according to the small-sized surface size of the workpiece to be tested; designing the size of the micro-test piece according to the small-sized surface size; processing a test piece according to the profile structure to be ultrasonically shot peened, processing a deep groove according to the size of the micro-test piece on the surface of the test piece to be strength tested; embedding a soft magnetic sheet at the bottom of the deep groove; placing the micro-test piece in the deep groove, where the micro-test piece is attracted to the deep groove by the magnetic force of the soft magnetic sheet; placing the clamped test piece fixture on an ultrasonic shot peening device for shot peening, and obtaining the shot peening process parameters using a shot peening intensity conversion method between micro-test pieces and standard test pieces; and measuring the strength. Cutting the micro-test piece on the standard test piece can realize shot peening strength testing of most small-sized profile workpieces; clamping the micro-test piece by magnetic adsorption greatly improves the measurement accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of metal workpiece surface strengthening, and in particular relates to a method for detecting the strength of small-sized surface ultrasonic shot peening. Background Art

[0002] Ultrasonic shot peening is an emerging metal surface strengthening process. Unlike traditional pneumatic shot peening, which uses a linear jet of medium, ultrasonic shot peening utilizes diffuse and repeated ejection of the medium to achieve the desired effect on complex, small-scale surfaces or cavity structures. Peening intensity is the most important performance metric during the process. Using an Almen strip fixed to the surface to perform shot peening and measuring its deformation is a key method for controlling shot peening quality. Traditionally, shot peening uses a 75mm x 19mm (length x width) Almen strip for strength measurement, as per industry standard HB / Z26-2011. However, many workpiece peening surfaces are currently smaller than this strip size, making this method unsuitable for small workpiece surfaces.

[0003] When testing small workpieces under special circumstances, the following two methods are commonly used: GE standard P11TF8 proposes a masking test method, which uses a block to partially mask the standard test strip, leaving an area consistent with the shot peening area of the small workpiece. Measurement and conversion are then performed after shot peening. Standard SAE J442 proposes a MINI test strip (sub-size test strip) test method, which stipulates that a 25mm×3mm test strip can be used to measure the shot peening intensity of small-sized surfaces. Of the above two methods, the former is only applicable to workpieces where the masking of the test strip does not interfere with the shot peening area, and the masking method may differ from the actual workpiece. The latter is still a fixed size and cannot be used to measure smaller sizes. The clamping method is screw clamping, and the nut squeezes the originally narrow shot peening space, affecting the accuracy of the shot peening measurement. It also requires specialized measuring tools and is expensive. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for ultrasonic shot peening strength testing of small-sized surface, so as to solve the problem that ultrasonic shot peening strength testing cannot be achieved for workpieces with small-sized surface structures.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for testing the strength of small-sized surface ultrasonic shot peening includes the following steps:

[0007] S1. Make micro specimens:

[0008] According to the small surface size of the workpiece to be tested, a micro test piece is cut from the standard test piece; the size of the micro test piece is designed according to the small surface size;

[0009] S2. Make the test piece fixture:

[0010] The test piece is processed according to the surface structure of ultrasonic shot peening as needed, and deep grooves are processed on the surface of the test piece that needs to be tested for strength according to the size of the micro test piece; a soft magnetic sheet is embedded in the bottom of the deep groove;

[0011] S3. Clamping the test piece:

[0012] The micro-test piece is placed in the deep groove. The micro-test piece is attracted to the deep groove by the magnetic force of the soft magnetic sheet. The surface of the micro-test piece is consistent with the small surface of the workpiece to be tested.

[0013] S4. Ultrasonic shot peening of test pieces:

[0014] The clamped specimen fixture is placed on an ultrasonic shot peening device for shot peening. The shot peening process parameters are obtained by converting the shot peening intensity of the micro specimen and the standard specimen.

[0015] S5. Strength measurement:

[0016] After the shot peening is completed, the micro specimen is taken out and measured using a measuring tool to read the deformation and deflection data of the micro specimen. This deformation and deflection data is the actual shot peening intensity measured by the micro specimen.

[0017] Furthermore, in S4, the specific steps of the method for converting the shot peening intensity of the micro test piece and the standard test piece are as follows:

[0018] 4.1. Make a double specimen fixture for holding standard specimens and micro specimens:

[0019] The double test piece fixture is provided with a clamping unit for clamping the standard test piece and a slot for clamping the micro test piece, and a soft magnetic sheet is bonded in the slot;

[0020] 4.2. Clamping the test piece: Clamp the standard test piece in the clamping unit, and use a waste test piece to protect the micro test piece position;

[0021] 4.3. Install the double test piece fixture into the ultrasonic shot peening device, adjust the shot peening parameters, and shot peen the standard test piece until the design strength value F1 of the standard test piece is obtained. At this time, the corresponding shot peening process is D1;

[0022] A new micro-test piece is clamped in the tank, and a waste test piece is used to protect the standard test piece position. The micro-test piece is shot peened using process D1 to obtain the micro-test piece strength value F2;

[0023] Take another micro test piece and install it into the test piece fixture made in S2, adjust the shot peening parameters, and obtain the intensity value F3; when F3 = F2, the corresponding shot peening process D2 is the shot peening process actually required for the part, and the shot peening effect corresponding to the shot peening intensity F3 is equivalent to the shot peening effect under the shot peening intensity F1.

[0024] Furthermore, in step 4.1, the size of the groove body is the same as the deep groove processed in S2, and the soft magnetic sheet is the same as the soft magnetic sheet bonded in S2.

[0025] Furthermore, in step 4.1, the double specimen fixture is made of an alloy with a hardness of not less than HRC57;

[0026] The clamping unit for holding standard test pieces is designed according to industry standards.

[0027] Furthermore, in S1, a micro test piece is cut from the standard test piece using a laser or electric spark cutting method.

[0028] Furthermore, in S1, the width of the micro-test piece is at least 2 mm, the aspect ratio is not less than 4:1 and not more than 10:1, and the flatness of the micro-test piece is within the range of ±0.025 mm.

[0029] Furthermore, the sum of the thicknesses of the soft magnetic sheet and the micro-test piece is equal to the depth of the deep groove.

[0030] Furthermore, in S1, the soft magnetic sheet is bonded to the bottom of the deep groove.

[0031] Furthermore, in S2, the test piece includes two symmetrical parts, and when in use, the two parts are connected by bolts.

[0032] Furthermore, in S5, a vernier caliper is used for measurement, wherein one of the calipers contacts the two end points of the micro-test piece, and the other caliper contacts the highest point of the arc of the micro-test piece.

[0033] Compared with the prior art, the present invention has the following beneficial technical effects:

[0034] The present invention discloses a method for ultrasonic shot peening strength detection of small-sized surfaces. A required micro-test piece is cut from a standard test piece. The micro-test piece can be freely designed in size and converted in strength according to the small-sized surface of the workpiece, so that shot peening strength detection of most small-sized surface workpieces can be realized, which greatly expands the detection range. On the basis of the existing standard test piece detection method, the shot peening process parameters required by the micro-test piece in the actual part application environment are obtained through the intensity conversion method, which avoids the influence of the part shape and makes the shot peening parameters more accurate. The micro-test piece is creatively clamped by magnetic adsorption, which not only makes the clamping and removal of the micro-test piece very convenient, but also reduces the influence of the traditional screw installation method on the shot peening effect, prevents the nut from blocking and interfering with the shot peening when screw clamping is used, and the surface of the micro-test piece can be consistent with the surface of the workpiece, which greatly improves the measurement accuracy.

[0035] Furthermore, measurement using a vernier caliper is simple and easy, and does not require the investment of special measuring tools. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of a typical two-tooth fir-tree-shaped mortise and tenon shot peening strength test piece;

[0037] Figure 2 Schematic diagram of the grooving of the tenon tooth surface;

[0038] Figure 3 Schematic diagram of installing soft magnetic sheets in deep grooves on tenon tooth surfaces;

[0039] Figure 4 This is a schematic diagram of a micro test piece cut from a standard test piece;

[0040] Figure 5 Schematic diagram of installing micro test piece on tenon tooth surface;

[0041] Figure 6 Schematic diagram of ultrasonic shot peening of strength test piece;

[0042] Figure 7 Schematic diagram of using a vernier caliper to detect the deformation deflection (shot peening intensity) of a micro specimen;

[0043] Figure 8 Schematic diagram of the double-test piece fixture;

[0044] Figure 9 Schematic diagram of double-test piece fixture ultrasonic shot peening;

[0045] In the figure: 1. Test piece; 2. Mortise and tenon; 3. Tenon tooth surface; 4. Cut surface; 5. Bolt; 6. Deep groove; 7. Soft magnetic sheet; 8. Standard test piece; 9. Miniature test piece; 10. Ultrasonic shot peening device; 11. Vernier caliper; 12. Double test piece fixture. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following is a further detailed description with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0047] The components described and illustrated in the drawings and embodiments of the present invention may be arranged and designed in a variety of different configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. All other embodiments derived by those skilled in the art based on the drawings and embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0048] The present invention discloses a method for detecting the strength of ultrasonic shot peening of a small-sized surface, the steps of which are as follows:

[0049] S1. Preparation of micro specimen 9:

[0050] Based on the required small surface size, a micro-strip 9 is cut from a standard test piece 8 measuring 75mm x 19mm x 0.8mm (length x width x height) using low-stress machining methods such as laser or electrospark cutting. The minimum width is 2mm, and the aspect ratio is no less than 4:1 and no more than 10:1. The flatness of the test piece is within ±0.025mm. The test piece is designed based on the workpiece size, eliminating the need for two standard test pieces 8, achieving universality.

[0051] S2. Make the workpiece test piece fixture:

[0052] A test piece 1 is processed according to the surface structure required for ultrasonic shot peening, and then a deep groove 6 is processed according to the size of a micro test piece 9 on the surface required for strength testing;

[0053] A single-sided adhesive-coated soft magnetic sheet 7 is cut to the desired size, placed in the slot, and securely bonded. Using the soft magnetic sheet 7 to absorb the test piece solves the problem of screw clamping on small surfaces, making it easier to load and unload the test piece.

[0054] S3. Clamping the test piece:

[0055] The micro test piece 9 is placed in the deep groove 6. The thickness of the soft magnetic sheet 7 and the test piece is equal to the groove depth. The surface of the test piece is consistent with the surface of the workpiece, which can achieve the minimum impact on the original workpiece space and the height restoration of the surface.

[0056] Since the test piece is made of general 70# spring steel, it can be magnetically adsorbed in the deep groove 6 .

[0057] S4. Ultrasonic shot peening of test pieces:

[0058] The test piece fixture is placed on the ultrasonic shot peening device 10 for shot peening treatment. The shot peening process parameters of the shot peening treatment are obtained by using the shot peening intensity conversion method of the micro test piece 9 and the standard test piece 8;

[0059] S5. Strength measurement:

[0060] After shot peening is complete, the specimen is removed by clamping or other means and measured using a vernier caliper 11. During measurement, one jaw contacts the specimen's two end points, while the other jaw contacts the highest point of the arc to avoid excessive force that could cause deformation. The specimen's deformation and deflection are then read, representing the shot peening intensity measured using the micro-specimen 9. Using a vernier caliper 11 for measurement eliminates the need for specialized measuring tools and is a simple and easy method.

[0061] If the shot peening intensity of the workpiece design drawing is based on the large-sized standard test piece 8, the intensity conversion can be performed to achieve compatibility with the standard test piece 8, thereby achieving the processing required by the existing drawing. The shot peening intensity conversion method of the micro test piece 9 and the standard test piece 8 is as follows:

[0062] 4.1. Making a double test piece fixture 12:

[0063] Made of alloy with a size of 80mm x 40mm x 20mm and a hardness of no less than HRC57, the fixture's standard test piece 8 is designed to be fixed in accordance with industry standard HB / Z26-2011. The micro test piece 9 follows the aforementioned design, using slots and a soft magnetic sheet 7 for clamping.

[0064] like Figure 8 As shown, the double test piece fixture 12 is provided with a clamping unit for clamping the standard test piece 8 and a slot for clamping the micro test piece 9, and the soft magnetic piece 7 is bonded in the slot.

[0065] 4.2、Clamp the test piece. Figure 9 As shown, the standard test piece 8 is clamped at the clamping unit position, the micro test piece 9 position is protected by a waste test piece, and then the double test piece fixture 12 is installed on the ultrasonic shot peening device 10.

[0066] 4.3. Shot peen the test piece to obtain the strength value F1 of the standard test piece 8. Adjust the shot peening parameters until F1 meets the strength requirements of the workpiece design drawing. The corresponding shot peening process is now D1. Clamp a new micro-test piece 9 in the slot position, and use a waste test piece for protection in the position of the standard test piece 8. Shot peen the micro-test piece 9 using process D1 to obtain the strength value F2 of the micro-test piece 9. Take another micro-test piece 9 and install it in the workpiece-specific strength test fixture. Adjust the shot peening parameters to obtain the strength value F3. When F2 = F3, the shot peening process D2 obtained is the actual processing process required for the part. At this time, the shot peening effect corresponding to the shot peening intensity F3 is equivalent to the shot peening effect under the shot peening intensity F1. That is, through the intensity conversion test, the shot peening intensity technical parameter requirements of the original drawing F1 are achieved.

[0067] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0068] Take the aircraft engine turbine disc mortise and tenon as an example: Figure 1As shown, the tenon 2 is a two-tooth fir-tree-shaped tenon structure of a certain aircraft engine, and the tenon tooth surface 3 is a surface that needs to be shot peened. Since the tenon 2 is a narrow cavity structure, it is difficult to effectively process it with traditional pneumatic direct shot peening, and an ultrasonic ejection shot peening process is required. The size of the tenon 2 is approximately 20mm (length) × 15mm (width) × 30mm (depth), and the size of the tenon tooth surface 3 is approximately 30mm (length) × 2mm (width). The size of the tenon 2 is much smaller than the size of the standard test piece 8 of 75mm × 19mm × 0.8mm (length × width × height), and the size of the tenon tooth surface 3 is also smaller than the size of the 25mm × 3mm test piece (Sub-size test strip). At this time, whether the standard test piece 8 or the MINI test piece is used, it is impossible to directly measure the shot peening strength of the tenon tooth surface 3. Therefore, it is necessary to use the method of the present invention to perform shot peening strength testing on small-sized surfaces.

[0069] The present invention discloses a method for detecting the strength of small-sized surface ultrasonic shot peening, the steps of which are:

[0070] S1. Preparation of micro specimen 9:

[0071] According to the size of the tenon tooth surface 3, that is, the width is 2mm, the maximum length-to-width ratio does not exceed 10:1, such as Figure 4 As shown, a 20 mm × 2 mm × 0.8 mm (length × width × height) micro-strip 9 is cut from a 75 mm × 19 mm × 0.8 mm (length × width × height) standard test piece 8 using a stress-free machining method such as laser or electric spark cutting. The flatness of the test piece is measured and ensured to be within ±0.025 mm.

[0072] S2. Make the test piece fixture:

[0073] like Figure 1 As shown, a tenon shot peening strength test piece 1 is processed according to the structural dimensions of the turbine disc tenon 2. In order to facilitate the processing of the tenon tooth surface 3 as shown in FIG. Figure 2 The deep groove 6 shown can be used to cut the mortise and tenon test piece 1 into two parts according to the cutting surface 4, and the two parts can be combined by bolts 5 when in use.

[0074] like Figure 2 As shown, a deep groove 6 is machined on the tenon tooth surface 3, with dimensions of 20.4 mm × 2.4 mm × 2.3 mm (length × width × depth).

[0075] like Figure 3 As shown, a soft magnetic sheet 7 with the same area and a thickness of 1.5 mm is embedded in the bottom of the deep groove 6 and is firmly bonded with a high bonding strength adhesive.

[0076] S3. Clamping the test piece: Figure 5 As shown, the micro test piece 9 is placed in the deep groove 6 and is attracted by the magnetic strip, so that the surface of the test piece is flush with the tenon tooth surface 3.

[0077] S4. Ultrasonic shot peening of test pieces: Figure 6 As shown, the test piece fixture is placed on the ultrasonic shot peening device 10 for shot peening, and the shot peening process parameters of the shot peening treatment are obtained by using the shot peening intensity conversion method of the micro test piece 9 and the standard test piece 8.

[0078] Specifically, the strength conversion method is as follows: a standard test piece 8 is installed on the double test piece fixture 12, and a waste test piece is used to protect the position of the micro test piece 9. The standard test piece 8 is first shot peened to obtain a strength value F1. When F1 meets the strength parameter requirements of the drawing design, the corresponding shot peening process is D1;

[0079] Then, the position of the standard test piece 8 is protected, and the micro test piece 9 is installed in the slot position on the double test piece fixture 12. The micro test piece 9 is shot peened using the shot peening process D1 to obtain the strength arc height value F2;

[0080] Next, a micro-test piece 9 is installed in the deep groove 6 of the tongue-and-groove shot peening strength test piece 1. The test piece is then placed on the ultrasonic shot peening apparatus 10, and the shot peening parameters are adjusted to obtain an intensity value F3. When F2 = F3, the shot peening process D2 obtained is the actual processing required for the part. The shot peening effect obtained at the shot peening intensity of F3 is equivalent to that obtained at the shot peening intensity of F1. This conversion allows for accurate testing when the drawing uses F1 as the design parameter.

[0081] S5. Shot peening intensity test: Figure 7 As shown, after the shot peening is completed, the micro specimen 9 is removed and measured using a vernier caliper 11. During measurement, one caliper contact is made with the two end points of the specimen, and the other caliper contact is made with the highest point of the arc of the specimen. The caliper distance reading is read, and this reading is the shot peening intensity value measured using the micro specimen 9.

[0082] During each test, there is a certain degree of error due to fluctuations in equipment and parameters. The standard stipulates that the test value must not differ from F3 by more than 10% to be acceptable. Therefore, although the shot peening process parameter D2 is obtained based on the strength conversion method, there is no guarantee that the finished product will have a strength of F3. Subsequent testing is required during each process to determine if the parameters deviate significantly.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for testing the strength of small-sized surface ultrasonic shot peening, characterized in that: The following processes are included: S1. Preparation of micro specimen (9): According to the small surface size of the workpiece to be inspected, a micro test piece (9) is cut from the standard test piece (8); the size of the micro test piece (9) is designed according to the small surface size; S2. Make the test piece fixture: A test piece (1) is processed according to the surface structure of ultrasonic shot peening as required, and a deep groove (6) is processed on the surface of the test piece (1) to be subjected to strength testing according to the size of the micro test piece (9); and a soft magnetic sheet (7) is embedded in the bottom surface of the deep groove (6); S3. Clamping the test piece: The micro-test piece (9) is placed in the deep groove (6), and the micro-test piece (9) is attracted to the deep groove (6) by the magnetic force of the soft magnetic piece (7), and the surface of the micro-test piece (9) is consistent with the surface of the small surface of the workpiece to be tested; S4. Ultrasonic shot peening of test pieces: The clamped specimen fixture is placed on an ultrasonic shot peening device (10) for shot peening. The shot peening process parameters of the shot peening process are obtained by converting the shot peening intensity of the micro specimen (9) and the standard specimen (8). S5. Strength measurement: After the shot peening is completed, the micro-test piece (9) is taken out and measured using a measuring tool to read the deformation deflection data of the micro-test piece (9). The deformation deflection data is the actual shot peening intensity measured by the micro-test piece (9); In S4, the specific steps of the shot peening intensity conversion method of the micro test piece (9) and the standard test piece (8) are as follows: 4.

1. Make a double specimen fixture (12) for holding the standard specimen (8) and the micro specimen (9): The double test piece fixture (12) is provided with a clamping unit for clamping the standard test piece (8) and a slot body for clamping the micro test piece (9), and a soft magnetic sheet (7) is bonded to the slot body; 4.

2. Clamping the test piece: Clamp the standard test piece (8) in the clamping unit, and use a waste test piece to protect the position of the micro test piece (9); 4.

3. Install the double test piece fixture (12) to the ultrasonic shot peening device (10), adjust the shot peening parameters, and shot peen the standard test piece (8) until the design strength value F1 of the standard test piece (8) is obtained. At this time, the corresponding shot peening process is D1; A new micro-test piece (9) is clamped in the tank, a waste test piece is used to protect the position of the standard test piece (8), and the micro-test piece (9) is shot peened using process D1 to obtain a strength value F2 of the micro-test piece (9); Another micro specimen (9) is taken and installed in the specimen fixture made in S2, and the shot peening parameters are adjusted to obtain the intensity value F3; when F3=F2, the corresponding shot peening process D2 is the shot peening process actually required for the part, and the shot peening effect corresponding to the shot peening intensity F3 is equivalent to the shot peening effect under the shot peening intensity F1.

2. A method for testing the strength of small-sized profiles using ultrasonic shot peening according to claim 1, characterized in that: In step 4.1, the groove body has the same size as the deep groove (6) processed in S2, and the soft magnetic sheet (7) is the same as the soft magnetic sheet (7) bonded in S2.

3. The method for testing the strength of small-sized profiles using ultrasonic shot peening according to claim 1, wherein: In step 4.1, the double test piece fixture (12) is made of alloy with a hardness of not less than HRC57; The clamping unit for clamping the standard test piece (8) is designed according to industry standards.

4. The method for testing the strength of small-sized profiles using ultrasonic shot peening according to claim 1, wherein: In S1, a micro specimen (9) is cut from a standard specimen (8) using a laser or electric spark cutting method.

5. The method for testing the strength of small-sized surface ultrasonic shot peening according to claim 1, characterized in that: In S1, the width of the micro-test piece (9) is at least 2 mm, the aspect ratio is not less than 4:1 and not more than 10:1, and the flatness of the micro-test piece (9) is within the range of ±0.025 mm.

6. The method for testing the strength of small-sized profiles using ultrasonic shot peening according to claim 1, wherein: The sum of the thicknesses of the soft magnetic sheet (7) and the micro test piece (9) is equal to the depth of the deep groove (6).

7. The method for testing the strength of small-sized profiles using ultrasonic shot peening according to claim 1, wherein: In S1, the soft magnetic sheet (7) is bonded to the bottom of the deep groove (6).

8. The method for testing the strength of small-sized profiles using ultrasonic shot peening according to claim 1, wherein: In S2, the test piece (1) comprises two symmetrical parts, which are connected by bolts (5) when in use.

9. The method for testing the strength of small-sized profiles using ultrasonic shot peening according to claim 1, wherein: In S5, a vernier caliper (11) is used for measurement. During measurement, one of the calipers contacts the two end points of the micro-test piece (9), and the other caliper contacts the highest point of the arc of the micro-test piece (9).

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