Spherical zinc sulfide window low-stress glue joint sealing structure and method

Abstract

The invention belongs to the technical field of cementing technologies and adhesives, and discloses a low-stress cementing sealing structure of a spherical zinc sulfide window, which is used for realizing butt joint of an aluminum alloy outer cover (2) and the spherical zinc sulfide window (1), and cementing sealing of the lower part of the outer wall of the spherical zinc sulfide window (1) and the upper part of the inner wall of the aluminum alloy outer cover (2). After the sealing assembly is used for sealing the zinc sulfide window, the overall leakage rate of the window (the sealing assembly is placed in a metal sealing container, a standard leakage opening is formed in the container, and the leakage rate is tested at the leakage opening through a helium mass spectrometer) is reduced to 10 <-8 > Pam < 3 > / s from 10 <-7 > Pam < 3 > / s sealed through traditional silicon rubber, the order of magnitude is reduced, and the sealing qualification rate is increased to 98% or above from 80%; compared with traditional epoxy resin sealing, the risk that the window deforms and even cracks is greatly avoided.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology and bonding technology, and relates to a low-stress, high-performance sealing structure and method for a spherical zinc sulfide window. Specifically, it involves the interface design between heterogeneous materials, the selection of adhesives, and the sealing process. Background Technology

[0002] The bonding technology between zinc sulfide windows and metal structures represents a deep integration of surface science, polymer chemistry, and mechanics. Specifically, it involves research on material surface energy, viscoelasticity, matching of thermal expansion coefficients, and stress concentration at the bonding interface. Interface sealing methods include welding, sealing rings, and adhesive sealing. Given the low strength of zinc sulfide materials and the impact of changes in surface stress on optical performance, adhesive sealing offers the lowest stress, but it is more complex and has lower reliability than other methods. Adhesives can be categorized by their physical form (solid, liquid, or gaseous) and curing methods (natural curing, temperature-controlled curing, and photocuring).

[0003] This method employs the natural curing of liquid adhesives, using either rubber-based adhesives with good viscoelasticity or epoxy-based adhesives with poor elasticity and low linear expansion coefficients. In actual mass applications and production, adhesive bonding exhibits significant uncertainty, primarily influenced by a combination of factors including adhesive type and thickness, interface geometry, surface treatment quality, and construction techniques. This ultimately leads to high bonding stress, poor process stability, and difficulty in accurately predicting sealing performance. The method is also affected by process reproducibility and strength dispersion. For example, Liu Qiang and He Xin et al., in "Calculation and Control of Adhesive Layer Thickness in Heated Assembly of Reflectors," mentioned a tendency to use large bonding areas to balance bonding stress, but this increases the mass of the optomechanical structure system and causes excessive thermal stress leading to changes in surface shape. Dong Deyi and Li Zhilai et al., in "Simulation and Experiment of the Influence of Adhesive Layer Curing on the Surface Shape of Reflectors," discussed the issue of adhesive layer thickness and changes in surface shape after curing. Using adhesives with good viscoelasticity, such as silicone adhesives, results in lower stress but poor bonding and sealing reliability, and a high coefficient of thermal expansion. Using adhesives with low expansion coefficients, such as epoxy resin, provides high sealing reliability but has low elasticity and high bonding stress. Summary of the Invention

[0004] (a) Purpose of the invention The purpose of this invention is to address the problems of unreliable sealing and high thermal stress caused by liquid adhesive bonding, and to propose a low-stress adhesive sealing structure and method with an "elastic" beveled spherical zinc sulfide window.

[0005] (II) Technical Solution To solve the above-mentioned technical problems, the present invention provides a low-stress adhesive sealing structure for a spherical zinc sulfide window, which is used to connect the aluminum alloy outer cover 2 and the spherical zinc sulfide window 1, and to adhesive seal the lower part of the outer wall of the spherical zinc sulfide window 1 with the upper part of the inner wall of the aluminum alloy outer cover 2.

[0006] Furthermore, at the junction of the aluminum alloy outer cover 2 and the spherical zinc sulfide window 1, the lower part of the outer wall of the spherical zinc sulfide window 1 is milled into an outer annular vertical surface, and an inner annular vertical surface is milled on the inner wall of the aluminum alloy outer cover 2. The outer annular vertical surface and the inner annular vertical surface are in contact.

[0007] Furthermore, an annular elastic groove II5 is opened on the inner wall of the aluminum alloy outer cover 2 below the inner annular vertical surface, and an elastic retaining ring or nut positioning pressure ring is installed in the elastic groove II5.

[0008] Furthermore, an annular elastic groove I4 is opened in the middle of the inner annular vertical surface, and the elastic groove I4 is filled with liquid silicone rubber.

[0009] Furthermore, the inner wall of the aluminum alloy outer cover 2 above the inner annular vertical surface is an inwardly inclined inner slope, which is opposite to the spherical surface above the outer annular vertical surface and is fitted with a clearance.

[0010] Furthermore, above the gap between the inner inclined surface and the spherical surface, the opening end face of the aluminum alloy outer cover 2 is an upward and outward inclined surface, and a bevel 3 is formed between the outer inclined surface and the spherical surface.

[0011] Furthermore, liquid epoxy resin was filled at three bevel locations.

[0012] Furthermore, the surface roughness of the elastic groove I4 is less than 1.6, and the surface roughness at the bevel is greater than 6.3.

[0013] Furthermore, the liquid silicone rubber has a hardness range of 20 Shore A to 30 Shore A, a tensile strength of not more than 3 MPa, and a peel strength of not less than 5 N / mm; the liquid epoxy resin, after mixing, has a viscosity of less than 500 mPa·s, a Shore hardness of less than 80, a glass transition temperature of less than 60℃, a linear expansion coefficient of less than 65 ppm / ℃ below the glass transition temperature, an elongation at break of not less than 65%, and a Young's modulus of not more than 550 MPa.

[0014] The present invention also provides a low-stress adhesive sealing method for a spherical zinc sulfide window, which includes the following steps: S1. Use tooling to support the zinc sulfide window and complete the positioning; S2. Fill the elastic groove I4 with liquid silicone rubber. Use an automatic or semi-automatic dispensing machine, set the nozzle shape, dispensing air pressure and moving speed parameters, and then fill the groove. S3. Fill the bevel with epoxy resin. Use an automatic or semi-automatic dispensing machine, set the nozzle shape, dispensing air pressure and moving speed parameters, and then fill the bevel completely. S4. After the adhesive dries naturally for 72 hours, remove the aluminum alloy outer cover 2 and the spherical zinc sulfide window 1 assembly. S5. Install an elastic retaining ring or nut positioning ring at the elastic groove II5 to complete the final positioning and assembly of the zinc sulfide window. S6. After assembly, bake for 48 hours above the glass transition temperature of the epoxy resin to release the bonding stress of the epoxy resin; after baking, cool to room temperature with the oven before normal use.

[0015] (III) Beneficial Effects The spherical zinc sulfide window low-stress adhesive sealing structure and method provided by the above technical solution, after sealing the zinc sulfide window, reduces the overall leakage rate of the window (by placing the sealing assembly into a metal sealing container with a standard leak port on the container, and testing the leakage rate at the leak port using a helium mass spectrometer) by 10% compared to traditional silicone rubber sealing. -7 Pam 3 / s, reduced to 10 -8 Pam 3 The seal quality was reduced by an order of magnitude, and the sealing pass rate increased from 80% to over 98%. Compared with traditional epoxy resin sealing, this greatly reduced the risk of window deformation or even breakage. Using the improved structure and method, the glass remained undamaged for 5 cycles under conditions of high temperature (70℃) for 4 hours, low temperature (-50℃) for 4 hours, and a temperature change rate greater than 5℃ / min during the high-low temperature transition. The total time exceeded 48 hours. In contrast, under the same test conditions, zinc sulfide windows using traditional epoxy resin bonding all cracked or broke. The improved structure and method significantly improved the adaptability and reliability of the window in extreme environments. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall bonding structure according to an embodiment of the present invention.

[0017] In the picture: 1. Zinc sulfide window, 2. Aluminum alloy casing.

[0018] Figure 2 This is an enlarged view of the interface in an embodiment of the present invention.

[0019] In the diagram: 3. Bevel, 4. Elastic groove I, 5. Elastic groove II. Detailed Implementation

[0020] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0021] Zinc sulfide windows have lower strength and softer texture than other sapphire windows. Using low-elasticity epoxy resin for bonding can easily lead to high stress and cracking of the glass. Using viscoelastic silicone rubber for bonding has low reliability. The large difference between the expansion coefficient and the substrate being bonded can cause the adhesion between the adhesive layer and the bonding surface to deteriorate, the sealing performance to decrease, or the adhesive layer to bulge after temperature changes.

[0022] like Figure 1 and Figure 2 As shown, in this embodiment, the low-stress adhesive sealing structure of the spherical zinc sulfide window is used to achieve the docking of the aluminum alloy outer cover 2 and the spherical zinc sulfide window 1, and the lower part of the outer wall of the spherical zinc sulfide window 1 is adhesively sealed to the upper part of the inner wall of the aluminum alloy outer cover 2.

[0023] At the junction of the aluminum alloy outer cover 2 and the spherical zinc sulfide window 1, the lower part of the outer wall of the spherical zinc sulfide window 1 is milled into an outer annular vertical surface, and an inner annular vertical surface is milled on the inner wall of the aluminum alloy outer cover 2. The outer annular vertical surface and the inner annular vertical surface are in contact.

[0024] An annular elastic groove II5 is opened on the inner wall of the aluminum alloy outer cover 2 below the inner annular vertical surface. An elastic retaining ring or a nut positioning pressure ring is installed in the elastic groove II5.

[0025] An annular elastic groove I4 is opened in the middle of the inner annular vertical surface, and the elastic groove I4 is filled with liquid silicone rubber.

[0026] The inner wall of the aluminum alloy outer cover 2 above the inner annular vertical surface is an inwardly inclined inner slope, which is opposite to the spherical surface above the outer annular vertical surface and is fitted with a clearance.

[0027] Above the gap between the inner inclined surface and the spherical surface, the opening end face of the aluminum alloy outer cover 2 is an upward and outward inclined surface, forming a bevel 3 between the outer inclined surface and the spherical surface. The bevel 3 is filled with a liquid epoxy resin adhesive with good sealing properties.

[0028] The design of elastic grooves I4 and II5, and bevel 3, facilitates the reduction of stress concentration and enhances sealing performance. Elastic grooves I4 and II5 can release adhesive stress or mitigate the change in the shape of the spherical cover caused by stress concentration at the bonding area during temperature changes.

[0029] The surface roughness of the elastic groove I4 is designed to be less than 1.6, which enhances the bonding force of the adhesive surface. The interior is filled with liquid silicone rubber with good viscoelasticity to reduce the stress at the bonding point. Moreover, the internal space of the groove is relatively large compared with the traditional adhesive gap, which is conducive to the expansion or contraction of silicone rubber under temperature changes without affecting the bonding strength of the adhesive surface.

[0030] The silicone sealant is selected with a hardness range of 20-30 (Shore A), a tensile strength not exceeding 3MPa, and a peel strength not less than 5N / mm to enhance adhesion to the substrate. The amount of silicone rubber filler is appropriately increased without changing the bonding area to ensure reliable adhesion. Liquid epoxy resin with good sealing properties is filled at the bevel 3 to enhance sealing. The bevel's contact point with the zinc sulfide window is designed to be wider at the top and narrower at the bottom to facilitate epoxy resin filling and stress release. The surface roughness at the bevel is designed to be 6.3 or higher, combined with elastic grooves I4 and II5 to reduce the impact of high epoxy resin bonding stress on the glass's surface shape. The epoxy resin adhesive should have a viscosity of less than 500 mPa·s after mixing, good flowability for easy filling, Shore hardness (D) of less than 80, glass transition temperature of less than 60℃, linear expansion coefficient of less than 65 ppm / ℃ below the glass transition temperature, elongation at break of not less than 65%, and Young's modulus of not more than 550 MPa, in order to reduce bonding stress and stress-induced changes in the glass surface shape.

[0031] Based on the above-mentioned low-stress adhesive sealing structure for the spherical zinc sulfide window, the process of the low-stress adhesive sealing method for the spherical zinc sulfide window in this embodiment is as follows: 1. Use tooling to support the zinc sulfide window and complete the positioning; 2. In Figure 2 Fill serial number 4 (elastic groove I) with liquid silicone rubber. Use an automatic or semi-automatic dispensing machine, setting parameters such as nozzle shape, dispensing air pressure, and moving speed, and then fill the groove. If using manual dispensing, the distance protruding from the groove end face after filling should be a to 2a (a is the maximum design gap between the outer cover and the window). The closer the protrusion is to the maximum design gap, the better. Use a PTFE tooling with a corresponding groove shape to scrape off excess adhesive at the filling point. 3. Figure 1 Fill the bevel with epoxy resin using item 2, ensuring that the resin does not overflow to the narrowest part of item 3 (bevel). Immediately fill the bevel with epoxy resin using an automatic or semi-automatic dispensing machine, setting the nozzle shape, dispensing air pressure, and moving speed parameters. Fill the bevel completely (to the widest part of the bevel). If any overflow occurs, wipe it clean with a lint-free cloth and alcohol. 4. After the adhesive has dried naturally for 72 hours (according to the adhesive instructions), remove the components (the outer cover and the window bonding parts); 5. In Figure 2 Install the elastic retaining ring or nut positioning ring at serial number 5 (elastic groove II) to complete the final positioning and assembly of the zinc sulfide window; 6. After assembly, bake at a high temperature of 60℃ (higher than the glass transition temperature of the epoxy resin) for 48 hours to release the bonding stress of the epoxy resin. After baking, cool to room temperature with the oven before normal use.

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-stress adhesive sealing structure for a spherical zinc sulfide window, characterized in that, This is used to connect the aluminum alloy outer cover (2) with the spherical zinc sulfide window (1), and the lower part of the outer wall of the spherical zinc sulfide window (1) is glued and sealed to the upper part of the inner wall of the aluminum alloy outer cover (2).

2. The low-stress adhesive sealing structure for the spherical zinc sulfide window as described in claim 1, characterized in that, At the junction of the aluminum alloy cover (2) and the spherical zinc sulfide window (1), the lower part of the outer wall of the spherical zinc sulfide window (1) is milled into an outer annular vertical surface, and an inner annular vertical surface is milled on the inner wall of the aluminum alloy cover (2). The outer annular vertical surface and the inner annular vertical surface are in contact.

3. The low-stress adhesive sealing structure for the spherical zinc sulfide window as described in claim 2, characterized in that, An annular elastic groove II (5) is opened on the inner wall of the aluminum alloy outer cover (2) below the inner annular vertical surface. An elastic retaining ring or nut positioning pressure ring is installed in the elastic groove II (5).

4. The low-stress adhesive sealing structure for the spherical zinc sulfide window as described in claim 3, characterized in that, An annular elastic groove I (4) is opened in the middle of the inner annular vertical surface, and the elastic groove I (4) is filled with liquid silicone rubber.

5. The low-stress adhesive sealing structure for the spherical zinc sulfide window as described in claim 4, characterized in that, The inner wall of the aluminum alloy outer cover (2) above the inner annular vertical surface is an inwardly inclined inner slope, which is opposite to the spherical surface above the outer annular vertical surface and is fitted with a gap.

6. The low-stress adhesive sealing structure for the spherical zinc sulfide window as described in claim 5, characterized in that, Above the gap between the inner inclined surface and the spherical surface, the opening end face of the aluminum alloy outer cover (2) is an upward and outward inclined surface, and a bevel (3) is formed between the outer inclined surface and the spherical surface.

7. The low-stress adhesive sealing structure for the spherical zinc sulfide window as described in claim 6, characterized in that, The bevel (3) is filled with liquid epoxy resin.

8. The low-stress adhesive sealing structure for the spherical zinc sulfide window as described in claim 7, characterized in that, The surface roughness of the elastic groove I (4) is less than 1.6, and the surface roughness of the bevel is more than 6.

3.

9. The low-stress adhesive sealing structure for the spherical zinc sulfide window as described in claim 8, characterized in that, The liquid silicone rubber has a hardness range of 20 Shore A to 30 Shore A, a tensile strength of not more than 3 MPa, and a peel strength of not less than 5 N / mm. The liquid epoxy resin has a viscosity of less than 500 mPa·s, a Shore hardness of less than 80, a glass transition temperature of less than 60℃, a linear expansion coefficient of less than 65 ppm / ℃ below the glass transition temperature, an elongation at break of not less than 65%, and a Young's modulus of not more than 550 MPa.

10. A method for low-stress adhesive sealing of a spherical zinc sulfide window based on the low-stress adhesive sealing structure of the spherical zinc sulfide window according to claim 9, characterized in that, Includes the following steps: S1. Use tooling to support the zinc sulfide window and complete the positioning; S2. Fill the elastic groove I (4) with liquid silicone rubber. Use an automatic dispensing machine or a semi-automatic dispensing machine, set the dispensing nozzle shape, dispensing air pressure and moving speed parameters, and then fill the groove. S3. Fill the bevel with epoxy resin. Use an automatic or semi-automatic dispensing machine, set the nozzle shape, dispensing air pressure and moving speed parameters, and then fill the bevel completely. S4. After the glue has dried naturally for 72 hours, remove the aluminum alloy outer cover (2) and the spherical zinc sulfide window (1) assembly. S5. Install an elastic retaining ring or nut positioning ring at the elastic groove II (5) to complete the final positioning and assembly of the zinc sulfide window; S6. After assembly, bake for 48 hours above the glass transition temperature of the epoxy resin to release the bonding stress of the epoxy resin; after baking, cool to room temperature with the oven before normal use.

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