Method for testing normal connection strength of titanium alloy sheet diffusion connection component

Abstract

The invention relates to the technical field of diffusion bonding, in particular to a method for testing the normal bonding strength of a titanium alloy thin plate type diffusion bonding component, a thin plate sample comprises a first thin plate piece and a second thin plate piece which are sequentially stacked up and down, and the first thin plate piece is provided with a through hollow part in the thickness direction of the first thin plate piece; the diffusion connection interface of the first sheet part and the second sheet part is an annular area, the lower end face area, located on the periphery of the annular area, of the first sheet part is a first concave face, and the upper end face area, directly facing the hollow part, of the second sheet part is a second concave face; the method comprises the following steps: applying pressure along the normal direction of a diffusion bonding interface to the upper end surface of a second thin plate piece through a hollow part until a thin plate sample is damaged; and determining the normal connection strength of the sheet sample according to the loading pressure value and the area of the diffusion connection interface. The method for testing the normal connection strength of the titanium alloy sheet type diffusion connection component aims to solve the problem that the normal connection strength of the titanium alloy sheet type diffusion connection component is difficult to detect.

Description

Technical Field

[0001] The present invention relates to the technical field of diffusion bonding, and in particular to a method for testing the normal connection strength of a titanium alloy thin plate diffusion bonding component. Background Art

[0002] Due to its excellent performance, titanium alloys are usually designed into thin plate components for use in aerospace weight reduction structures. However, titanium alloys have active chemical properties and poor welding performance, and conventional welding methods are prone to produce welding defects such as pores and oxides. Diffusion bonding has the advantages of high connection strength, controllable precipitation phase, and few defects, and is considered to be an advanced technology for solving titanium alloy welding problems. The normal connection strength of diffusion bonding is an important indicator for measuring the quality of diffusion bonding. The width of diffusion bonding usually ranges from a few microns to tens of microns, and it is difficult to accurately apply tension to the diffusion bonding interface to measure its connection strength. In addition, the thickness of thin plate diffusion bonding components is very small, and it is difficult to use them to process the clamping end of the mechanical tensile specimen for conventional mechanical testing.

[0003] Currently, there are three main methods for testing diffusion bond quality: metallography, mechanical testing, and ultrasonic testing. Metallography is the most common testing method. It involves cutting a metallographic sample from the diffusion bond area, calculating the length of the welded area in the cross section, and dividing the weld length by the sample length to calculate the weld rate. The weld rate is used as a criterion for evaluating diffusion bond quality. It is generally believed that a higher weld rate indicates better diffusion bond quality. Metallography only measures the quality of a local cross section and cannot obtain mechanical property data. Mechanical testing involves measuring mechanical properties such as tensile strength, shear strength, and hardness at the diffusion bond interface, comparing these to the parent material, and using the difference in mechanical properties as an evaluation criterion. Conventional mechanical testing lacks clamping material at both ends, making sampling and sample preparation difficult. Ultrasonic testing involves transmitting ultrasonic waves from the component surface toward the diffusion bond area, detecting defects based on the difference in the characteristics of the received and transmitted waves. Ultrasonic testing cannot detect micron-level defects, making it difficult to assess their impact.

[0004] Therefore, the inventors provide a method for testing the normal connection strength of titanium alloy thin plate diffusion-bonded components. Summary of the Invention

[0005] (1) Technical problems to be solved The embodiment of the present invention provides a method for testing the normal connection strength of titanium alloy thin plate diffusion-bonded components, which solves the technical problem of difficulty in testing the normal connection strength of titanium alloy thin plate diffusion-bonded components.

[0006] (2) Technical solution The present invention provides a method for testing the normal connection strength of a titanium alloy thin plate diffusion-bonded component. The thin plate specimen includes a first thin plate member and a second thin plate member stacked one above the other and diffusion-bonded. The first thin plate member has a through hollow portion along its thickness direction. The diffusion-bonded interface between the first thin plate member and the second thin plate member is an annular region. The lower end surface region of the first thin plate member located outside the annular region is a first concave surface, and the upper end surface region of the second thin plate member facing the hollow portion is a second concave surface. The method comprises the following steps: applying pressure along the normal direction of the diffusion bonding interface to the upper end surface of the second thin plate through the hollow portion until the thin plate sample is destroyed; The normal connection strength of the thin plate sample is determined according to the loading pressure value and the area of ​​the diffusion bonding interface.

[0007] Furthermore, the thin plate specimen is installed on a positioning fixture, which includes a base having a mounting cavity and a positioning groove. The first thin plate member is installed in the positioning groove, and the second thin plate member is located in the mounting cavity and has a set distance from the inner wall of the mounting cavity.

[0008] Furthermore, the positioning tool also includes a pressing plate, which is pressed on the upper end surface of the base and has a guide hole for the loading pressure head to pass through along its thickness direction.

[0009] Furthermore, the axes of the installation cavity, the positioning groove, the guide hole, the thin plate specimen and the loading pressure head coincide with each other.

[0010] Furthermore, the pressing plate is mounted on the base via fasteners.

[0011] Furthermore, the weak positions of the thin plate specimen include a first position, a second position and a third position, the first position being the annular area, the second position being the first cylindrical surface of the first thin plate member in contact with the positioning tooling and closest to the hollow portion, and the third position being the second cylindrical surface at the pressure boundary position applied to the second thin plate member; the ratios of the shear stress at the second position and the third position to the shear strength of the material are both smaller than the ratio of the tensile stress at the first position to the tensile strength of the material.

[0012] Furthermore, the loading rate of the loading pressure head is a set value.

[0013] Furthermore, the tensile stress at the first position is positively correlated with the loading pressure, and is inversely correlated with the square difference between the diameter of the second thin plate and the inner cavity diameter of the hollow portion.

[0014] Furthermore, the shear stress at the second position is positively correlated with the loading pressure, and is inversely correlated with the distance from the second position to the axis of the thin plate sample and the thickness of the first thin plate member at the fixed end.

[0015] Furthermore, the shear stress at the third position is positively correlated with the loading pressure, and inversely correlated with the distance from the boundary of the loading pressure to the axis of the thin plate sample, and the difference between the maximum thickness of the thin plate sample and the depth of the hollow portion.

[0016] (3) Beneficial effects In summary, the present invention overcomes the disadvantage that thin plate components cannot be processed into clamping ends of conventional mechanical tensile specimens by applying tension to the diffusion bonding interface of thin plate components in the form of stamping, and by designing the structural parameters of thin plate specimens, while realizing quantitative and rapid testing of the normal connection strength of the diffusion bonding interface of thin plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 This is a flow chart of a method for testing the normal connection strength of a titanium alloy thin plate diffusion bonded component provided by an embodiment of the present invention; Figure 2 This is a structural front view of a thin plate specimen provided by an embodiment of the present invention; Figure 3 This is a top view of the structure of a thin plate sample provided by an embodiment of the present invention; Figure 4 Schematic diagram of an overcut structure of a thin plate specimen provided by an embodiment of the present invention; Figure 5 This is a schematic diagram of the assembly structure of a thin plate specimen and a positioning tool provided by an embodiment of the present invention; Figure 6 This is a schematic diagram of the assembly structure dimensions of a thin plate specimen and a positioning tool provided by an embodiment of the present invention; Figure 7 yes Figure 6 A magnified view of the structure at point A; Figure 8 This is a schematic diagram of the structure and dimensions of a thin plate sample provided in Example 1 of the present invention; Figure 9 yes Figure 8 Structural cross-sectional view at the BB surface.

[0019] In the picture: 1-thin plate specimen; 101-first thin plate member; 1011-hollow portion; 102-second thin plate member; 2-positioning fixture; 201-base; 2011-mounting cavity; 2012-positioning groove; 202-pressing plate; 2021-guide hole; 3-loading pressure head; D-diffusion bonding interface; E-first cylindrical surface; F-second cylindrical surface. DETAILED DESCRIPTION

[0020] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are intended to illustrate the principles of the present invention and are not intended to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments and covers any modifications, replacements, and improvements to the parts, components, and connection methods without departing from the spirit of the present invention.

[0021] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0022] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0023] It should also be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "disposed" and "installed" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0024] Diffusion bonding is widely used in the aerospace industry, particularly for thin-plate components such as hollow aeroengine blades. However, quality testing methods are lacking, and component safety design and service performance assessment need to be improved. Therefore, this application investigates methods for testing the normal bond strength of thin-plate diffusion-bonded components, aiming to improve the diffusion bonding quality evaluation system and provide valuable insights for the design of titanium alloy thin-plate components.

[0025] Figure 1It is a flow chart of a method for testing the normal connection strength of a titanium alloy thin plate diffusion-bonded component provided by an embodiment of the present invention. The thin plate specimen 1 includes a first thin plate member 101 and a second thin plate member 102 stacked in sequence and diffusion-connected. The first thin plate member 101 has a through hollow portion 1011 along its thickness direction. The diffusion connection interface between the first thin plate member 101 and the second thin plate member 102 is an annular area. The lower end face area of ​​the first thin plate member 101 located outside the annular area is a first concave surface, and the upper end face area of ​​the second thin plate member 102 opposite to the hollow portion 1011 is a second concave surface.

[0026] To apply tension to the diffusion bonding interface by stamping, it is necessary to first remove the material near the diffusion bonding interface so that the diffusion bonding interface can bear the load independently. The structure of the thin plate sample 1 after removal is as follows: Figure 2-3 As shown, the thin plate specimen 1 is divided into two parts. The upper part (the first thin plate member 101) is used to fix the specimen, and the lower part (the second thin plate member 102) bears the pressure. In addition, to ensure that the pressure is accurately applied to the diffusion bonding interface, a small amount of overcutting is adopted on both the first thin plate member 101 and the second thin plate member 102, so that the hole of the hollow part 1011 is deeper, ensuring that all the upper panel material is removed in this area; in the outer peripheral overlap area, the material of the lower end surface of the first thin plate member 101 is cut upward a little more (beyond the level of the diffusion bonding interface). In this way, the interface to be tensile tested is ensured to be accurate. The section to be tested is placed at the minimum cross-section position, so that this section breaks first. The overcut position is as follows: Figure 4 shown.

[0027] Specifically, the method comprises the following steps: S100, applying pressure along the normal direction of the diffusion bonding interface to the upper end surface of the second thin plate through the hollow portion until the thin plate sample is destroyed.

[0028] In step S100, the specific operating process of the test is as follows: (1) Place the thin plate specimen in the groove of the positioning fixture; (2) Install the pressure plate to fully constrain the thin plate specimen and tighten the four bolts (fasteners) to fix the thin plate specimen; (3) Install the loading head and ensure that the axis of the loading head coincides with the axis of the thin plate specimen and the axis of the positioning fixture; (4) Fix the positioning fixture on the electronic universal material testing machine, and the testing machine applies pressure to the loading head until the thin plate specimen is broken, and the punching force value is recorded. Furthermore, the loading rate of the loading head is set to a set value (which can be 1mm / min). Selecting a reasonable loading rate makes the test data more realistic and discriminative.

[0029] S200. Determine the normal connection strength of the thin plate specimen based on the loading pressure value and the area of ​​the diffusion bonding interface.

[0030] It should be noted that, in order to facilitate testing, the first thin plate member 101 and the second thin plate member 102 are designed to be hollow cylindrical and cylindrical, respectively.

[0031] As an optional implementation, Figure 6 As shown, the weak positions of the thin plate specimen 1 include the first position, the second position and the third position. The first position is the annular area (i.e., the diffusion bonding interface D), the second position is the first cylindrical surface E of the first thin plate member 101 in contact with the positioning fixture 2 and closest to the hollow portion 1011, and the third position is the second cylindrical surface F at the pressure boundary position applied to the second thin plate member 102. The ratios of the shear stress at the second and third positions to the shear strength of the material are both smaller than the ratio of the tensile stress at the first position to the tensile strength of the material, that is, the boundary condition of formula (1) is satisfied. The calculation method of the tensile stress σ of the diffusion bonding interface is shown in formula (2).

[0032] Specifically, stress concentration is likely to occur at the second position, causing the corresponding position of the first thin plate 101 to reach the shear strength limit and fail before the diffusion bonding interface. The third position is the second thin plate 102, which first contacts the loading pressure head 3. If the design is unreasonable, a form of failure similar to punching will occur. The tensile stress at the first position is positively correlated with the loading pressure, and is negatively correlated with the square difference between the diameter of the second thin plate 102 and the inner diameter of the hollow part 1011. The shear stress at the second position is positively correlated with the loading pressure, and is negatively correlated with the distance from the second position to the axis of the thin plate sample and the thickness of the first thin plate 101 at the fixed end. The shear stress at the third position is positively correlated with the loading pressure, and is negatively correlated with the distance from the boundary of the loading pressure to the axis of the thin plate sample and the difference between the maximum thickness of the thin plate sample 1 and the depth of the hollow part 1011.

[0033] Where F is the loading pressure, Φ 1 is the diameter of the hollow part, Φ 2 is the diameter of the second thin plate; d1 is the distance from the edge of the first thin plate in contact with the positioning fixture (i.e., the second position) to the axis of the thin plate specimen; d2 is the distance from the boundary where the pressure F is applied (i.e., the third position) to the axis of the thin plate specimen; d3 is the upward overcut distance of the lower end surface of the first thin plate; d4 is the downward overcut distance of the upper end surface of the second thin plate; t1 is the thickness of the fixed end of the first thin plate; t2 is the sum of the thickness of the second thin plate and the depth of the upward overcut of the lower end surface of the first thin plate; h is the depth of the hollow portion; τ u is the shear strength of the thin plate specimen material, σ u is the tensile strength of the thin plate specimen material.

[0034] As an optional implementation, Figure 5 As shown, the thin plate specimen 1 is mounted on a positioning fixture 2, which includes a base 201 having a mounting cavity 2011 and a positioning groove 2012. The first thin plate member 101 is mounted in the positioning groove 2012, and the second thin plate member 102 is located in the mounting cavity 2011 and has a set distance from the inner wall of the mounting cavity 2011. Figure 6 If the gap between the second thin plate 102 and the mounting cavity 2011 is too large, a bending moment will be generated at the bottom edge of the first cylindrical surface E, affecting the stiffness of the specimen; if the gap is too small, it will affect the blanking. Considering the above two factors, the gap is selected to be 0.2mm.

[0035] As an optional implementation, Figure 5 As shown, the positioning fixture 2 also includes a pressure plate 202, which is pressed against the upper end surface of the base 201 and has a guide hole 2021 formed along its thickness for the loading ram 3 to pass through. The axes of the mounting cavity 2011, positioning groove 2012, guide hole 2021, thin plate specimen 1, and loading ram 3 coincide. The guide hole 2021 controls the coaxiality of the axes of the loading ram 3, thin plate specimen 1, and positioning fixture 2 to reduce errors during testing.

[0036] Example 1 1. Use 1mm and 2mm thick TC4 sheets, cut into 170mm×100mm pieces, and make test pieces after pickling, sealing, vacuuming, diffusion bonding and other processes. Figure 6 As shown, the total thickness of the test piece is 3 mm, and the diffusion bonding test process parameters are 890°C / 1.5 MPa / 120 min.

[0037] 2. Basis Figure 6-7 Substitute the TC4 material parameters into formula (1) to calculate the specific structural parameters of the thin plate specimen. The calculated parameters of the thin plate specimen are as follows: Figure 8-9 As shown, the diffusion connection width is 0.5 mm.

[0038] 3. After aligning the thin plate specimen, base, pressure plate, bolts, and loading head, place it on the electronic universal tensile test piece work platform and set the loading rate to 1 mm / min. Then, activate the loading module and apply a displacement load to the loading head until the thin plate specimen fails. Record the pressure at failure, which is 11083.29 N.

[0039] 4. The connection strength calculated according to formula (2) is 830.52 MPa, which is the measured normal connection strength of the diffusion bonding interface.

[0040] It should be noted that the various embodiments in this specification are described in a progressive manner. References to the same or similar parts between the various embodiments are sufficient. Each embodiment focuses on the differences from the other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and technologies are omitted here.

[0041] The above are merely embodiments of the present application and are not intended to limit the present application. Various modifications and variations are possible for those skilled in the art without departing from the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for testing the normal connection strength of titanium alloy thin plate diffusion bonded components, characterized in that: The thin plate specimen includes a first thin plate member and a second thin plate member stacked in sequence and diffusion-connected, the first thin plate member having a through hollow portion along its thickness direction, the diffusion-connected interface between the first thin plate member and the second thin plate member being an annular region, the lower end surface region of the first thin plate member located outside the annular region being a first concave surface, and the upper end surface region of the second thin plate member facing the hollow portion being a second concave surface; the method comprises the following steps: applying pressure along the normal direction of the diffusion bonding interface to the upper end surface of the second thin plate through the hollow portion until the thin plate sample is destroyed; The normal connection strength of the thin plate sample is determined according to the loading pressure value and the area of ​​the diffusion bonding interface.

2. The method for testing the normal connection strength of titanium alloy thin plate diffusion bonded components according to claim 1, characterized in that: The thin plate specimen is installed on a positioning fixture, which includes a base having a mounting cavity and a positioning groove. The first thin plate member is installed in the positioning groove, and the second thin plate member is located in the mounting cavity and has a set distance from the inner wall of the mounting cavity.

3. The method for testing the normal connection strength of titanium alloy thin plate diffusion bonded components according to claim 2, characterized in that: The positioning fixture further comprises a pressing plate, which is pressed on the upper end surface of the base and has a guide hole for the loading press head to pass through opened along the thickness direction of the pressing plate.

4. The method for testing the normal connection strength of titanium alloy thin plate diffusion bonded components according to claim 3, characterized in that: The axes of the installation cavity, the positioning groove, the guide hole, the thin plate sample and the loading pressure head coincide with each other.

5. The method for testing the normal connection strength of titanium alloy thin plate diffusion bonded components according to claim 3, characterized in that: The pressing plate is mounted on the base via fasteners.

6. The method for testing the normal connection strength of titanium alloy thin plate diffusion bonded components according to claim 2 or 3, characterized in that: The weak positions of the thin plate specimen include a first position, a second position and a third position, the first position being the annular area, the second position being the first cylindrical surface of the first thin plate member in contact with the positioning fixture and closest to the hollow portion, and the third position being the second cylindrical surface at the pressure boundary position applied to the second thin plate member; the ratios of the shear stress to the shear strength of the material at the second position and the third position are both smaller than the ratio of the tensile stress to the tensile strength of the material at the first position.

7. The method for testing the normal connection strength of titanium alloy thin plate diffusion bonded components according to claim 3, characterized in that: The loading rate of the loading head is a set value.

8. The method for testing the normal connection strength of titanium alloy thin plate diffusion bonded components according to claim 6, characterized in that: The tensile stress applied to the first position is positively correlated with the loading pressure, and is inversely correlated with the square difference between the diameter of the second thin plate and the inner diameter of the hollow portion.

9. The method for testing the normal connection strength of titanium alloy thin plate diffusion bonded components according to claim 6, characterized in that: The shear stress at the second position is positively correlated with the loading pressure, and is inversely correlated with the distance from the second position to the axis of the thin plate sample and the thickness of the first thin plate member at the fixed end.

10. The method for testing the normal connection strength of titanium alloy thin plate diffusion bonded components according to claim 6, characterized in that: The shear stress at the third position is positively correlated with the loading pressure, and inversely correlated with the distance from the boundary of the loading pressure to the axis of the thin plate sample and the difference between the maximum thickness of the thin plate sample and the depth of the hollow portion.

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