A clamp and a testing method for stress corrosion testing

Abstract

The embodiment of the present application discloses a kind of stress corrosion test fixture and test method.The fixture includes stress simulation component and stress adjusting component.Stress simulation component includes needle valve unit, spring seat and telescopic spring, both sides of spring seat are respectively connected with telescopic spring and needle valve unit, the side of needle valve unit away from spring seat is used to be mutually abutted with test piece.Stress adjusting component includes fixture shell and stress loading unit connected on fixture shell, fixture shell and stress loading unit form the cavity of containing stress simulation component, stress loading unit includes sliding mechanism and positioning mechanism.The fixture provides preload according to stress simulation component, and controls telescopic spring telescopic feed quantity by stress adjusting component, to ensure that test piece is subjected to always stable preload, guarantee the consistency and accuracy of stress corrosion test.The method can accurately and effectively evaluate the stress corrosion resistance of valve seat and valve sleeve welding assembly of oil sprayer.

Description

Technical Field

[0001] This invention relates to the field of stress resistance testing technology, and in particular to a fixture and testing method for stress corrosion testing. Background Technology

[0002] Stress corrosion cracking is a common failure mode in metallic materials and one that the industry must avoid during product development and design. It is primarily related to three factors: material properties, stress level, and corrosive environment. In the operation of high-pressure fuel injectors, if stress corrosion cracking of the valve seat occurs, fuel leaks will occur, potentially leading to engine shutdown and other problems.

[0003] Therefore, in the development and design of high-pressure direct injection injectors, it is necessary to evaluate the stress corrosion resistance of the valve seat and valve sleeve welded components to design a reliable and safe high-pressure injection injector product. Existing test fixtures cannot guarantee that multiple test groups maintain the same preload force precisely during testing, thus failing to ensure the consistency and accuracy of stress corrosion testing. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to provide a precise preload force for stress corrosion testing fixtures to ensure the consistency and accuracy of multiple test pieces in stress corrosion tests.

[0005] This invention discloses a fixture for stress corrosion testing, comprising a stress simulation component and a stress adjustment component. The stress simulation component includes a needle valve unit, a spring seat, and a telescopic spring. The two sides of the spring seat are respectively connected to the telescopic spring and the needle valve unit. The side of the needle valve unit away from the spring seat is used to abut against the test piece. The stress adjustment component includes a fixture housing and a stress loading unit connected to the fixture housing. The fixture housing and the stress loading unit form a cavity for accommodating the stress simulation component. The stress loading unit includes a sliding mechanism and a positioning mechanism. The sliding mechanism can move downwards along the axial direction of the fixture housing to apply stress to the test piece. The positioning mechanism can abut against or separate from the fixture housing to restrict the movement of the sliding mechanism.

[0006] The stress simulation component in the stress corrosion test fixture is used to apply a first preset stress (i.e., preliminary preset stress) to the test piece, and the stress adjustment component is used to adjust the stress of the test piece to obtain a second pre-stress (i.e., precise preset stress) applied to the test piece. Thus, it can provide a precise preload force to ensure the consistency and accuracy of multiple test pieces in the stress corrosion test.

[0007] Furthermore, a pad is provided between the stress loading unit and the telescopic spring. When the stress loading unit moves downward, one end of the pad can abut against the stress loading unit, and the other end can abut against the telescopic spring.

[0008] Specifically, both the stress loading unit and the pad block have interconnected through holes at their centers, and the maximum diameter of the pad block is larger than the diameter of the through hole in the stress loading unit.

[0009] Furthermore, the stress loading unit is a loading nut, the sliding mechanism is a nut sleeve, the positioning mechanism is the thread on the nut sleeve, and the loading nut is threadedly connected to the fixture housing.

[0010] Furthermore, the needle valve unit includes a rod and a valve ball portion disposed at one end of the rod, with the end of the rod away from the valve ball portion connected to a spring seat.

[0011] Furthermore, a connecting part is provided at one end of the rod, and a connecting groove matching the shape of the connecting part is provided in the middle of the spring seat. The rod is inserted into the spring seat through the connecting part and the connecting groove, and the diameter of the connecting part is larger than the diameter of the rod.

[0012] Furthermore, the connecting part is also provided with a positioning protrusion, which cooperates with the connecting part to form a positioning step surface, and the positioning step surface abuts against the spring seat.

[0013] Furthermore, a spring groove is provided on the end face where the spring seat connects to the telescopic spring, and the telescopic spring is connected in the spring groove.

[0014] Furthermore, a support protrusion is provided on the middle end face where the spring seat connects to the telescopic spring, and the telescopic spring is sleeved on the support protrusion.

[0015] Furthermore, the needle valve unit is integrally formed with the spring seat.

[0016] The present invention further discloses a testing method, comprising the following steps:

[0017] S1: Install the test piece in the fixture and apply a preset stress to the test piece;

[0018] S2: Prepare the stress corrosion test solution and pour the stress corrosion test solution into the test container;

[0019] S3: Place multiple prestressed fixtures on a tray, and place the tray containing the test fixtures into a test container containing stress corrosion test solution, so that the corrosion test solution covers the test position of the test sample.

[0020] S4: Place the test container containing the tray and test solution into the temperature chamber, turn on the temperature chamber, set the ambient temperature inside the temperature chamber to the required temperature, and start the stress corrosion test.

[0021] S5: Collect test data and analyze the stress corrosion resistance level of the test piece based on the test data.

[0022] Furthermore, step S1 also includes: S11: applying a preset loading force to the pad block through an external loading device to control the spring seat below the telescopic spring to drive the needle valve unit to apply a first preset stress to the test piece; S12: screwing in the stress loading unit so that the stress loading unit and the pad block abut against each other, and then continuing to screw in the stress loading unit so that the spring seat below the telescopic spring drives the needle valve unit to apply a second preset stress to the test piece.

[0023] Furthermore, a probe is used to pass through the through-hole of the stress loading unit and the through-hole of the pad, and the end of the probe is made to make vertical contact with the second bottom surface; a first distance from the second bottom surface to the first upper surface or a second distance from the second bottom surface to the upper surface of the stress loading unit is measured; the sliding depth of the stress loading unit is adjusted by the first distance or the second distance.

[0024] The stress corrosion testing fixture of the present invention provides a preload force based on the stress simulation component and controls the extension and retraction feed of the telescopic spring through the stress adjustment component, thereby ensuring that the test piece is subjected to a stable preload force at all times, and guaranteeing the consistency and accuracy of the stress corrosion test.

[0025] The testing method of this invention can simulate real working conditions and accurately and effectively evaluate the stress corrosion resistance of the valve seat and valve sleeve welded assembly of the injector. Attached Figure Description

[0026] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein:

[0027] Figure 1 A schematic diagram of the structure of a high-pressure fuel injector provided in the prior art;

[0028] Figure 2 for Figure 1 Cross-sectional view of region A in the middle;

[0029] Figure 3 This is a cross-sectional view of the stress corrosion testing fixture provided in Embodiment 1 of the present invention;

[0030] Figure 4 This is a schematic diagram of a stress corrosion test provided in Embodiment 2 of the present invention;

[0031] Figure 5 This is a flowchart illustrating the testing method provided in Embodiment 2 of the present invention;

[0032] Figure 6This is a cross-sectional view of the needle valve unit provided in Embodiment 3 of the present invention;

[0033] Figure 7 This is a cross-sectional view of the needle valve unit provided in Embodiment 4 of the present invention;

[0034] Figure 8 This is a cross-sectional view of the needle valve unit and spring seat provided in Embodiment 5 of the present invention;

[0035] Figure 9 This is a cross-sectional view of the needle valve unit and spring seat provided in Embodiment 6 of the present invention;

[0036] Figure 10 This is a cross-sectional view of the spring seat provided in Embodiment 7 of the present invention;

[0037] Figure 11 This is a cross-sectional view of the pad block provided in Embodiment 8 of the present invention.

[0038] Icons: 01-Valve seat; 011-Sealing surface; 012-Welding area;

[0039] 02-Valve sleeve;

[0040] 03-Fuel conduit;

[0041] 04-Fuel take-off;

[0042] 05-Needle valve; 051-Head;

[0043] 06-Clamp housing; 061-Housing step; 062-Housing through hole; 063-Housing inner cavity; 064-Housing lower end face; 067-Threaded part;

[0044] 07-Loading nut; 071-Nut through hole; 072-Nut inner end face; 073-Nut inner cavity; 074-Nut upper end face;

[0045] 08-Needle valve unit; 081-Valve ball; 082-Connecting part; 083-Positioning protrusion; 085-Flat-headed cylinder; 086-Slot; 087-First bottom surface; 088-First top surface;

[0046] 09-Spring seat; 091-Spring groove; 092-Second bottom surface; 093-Positioning groove; 094-Connecting groove; 095-Base protrusion; 096-First step surface; 097-Lower end surface of protrusion; 098-Supporting protrusion; 099-Supporting step;

[0047] 10 - Extension spring;

[0048] 11-Padded block; 111-First side end face; 112-First upper end face; 113-First contact surface; 114-Padded block through hole; 115-Padded block circular groove end; 116-Circular groove bottom surface. Detailed Implementation

[0049] To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0050] It should be understood that the terms “system,” “device,” “unit,” and / or “module” used herein are one method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other words can achieve the same purpose, they may be replaced by other expressions.

[0051] As indicated in this specification and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0052] Flowcharts are used in this specification to illustrate the operations performed by the system according to embodiments of this specification. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0053] Example 1

[0054] High-pressure fuel injectors are one of the important components in modern gasoline direct injection engines. They can accurately supply the fuel required by the engine under various operating conditions and fully atomize the fuel to form a good combustible mixture. Their performance and reliability have a crucial impact on the engine's power performance and safety. Figure 1 The diagram shown is a structural schematic of a high-pressure fuel injector. Figure 2 for Figure 1Cross-sectional view of area A (the area within the solid line frame). When the high-pressure injector is activated, fuel enters through the inlet of fuel connector 04, flows through fuel conduit 03, then into valve sleeve 02, and finally into the inner cavity of valve seat 01, where it is injected to the outside through the nozzle at the bottom of valve seat 01. The injector's valve seat 01 and valve sleeve 02 are typically welded together. During operation, the welded assembly of valve seat 01 and valve sleeve 02 is subjected to forces from the head 051 of needle valve 05 and the oil pressure within its cavity. In contrast, high-pressure direct injection injectors are mounted on the engine cylinder head, with the welded assembly of valve seat 01 and valve sleeve 02 extending directly into the engine cylinder. The fuel in the engine cylinder contains small amounts of corrosive elements such as sulfur and chlorine, some of which adhere to the welded assembly of valve seat 01 and valve sleeve 02 after combustion. Therefore, the welded assembly of valve seat 01 and valve sleeve 02 is subjected to stress from the internal needle valve and oil pressure, as well as the external high-temperature corrosive environment, during long-term operation of the injector. This satisfies the influencing factors of stress corrosion cracking. The material properties of the welded area 012 of valve seat 01 and valve sleeve 02, and the heat-affected weld area 012, are relatively weak (the location of weld area 012 is only illustrative and can also be located at the contact end face of valve seat 01 and valve sleeve 02). This weak area may experience stress corrosion cracking. Once stress corrosion cracking failure of valve seat 01 occurs, the injector will leak oil, leading to problems such as engine shutdown.

[0055] Therefore, in the development and design of high-pressure direct injection injectors, it is necessary to evaluate the stress corrosion resistance of the welded assembly of the valve seat 01 and valve sleeve 02 of the injector in order to design a reliable and safe high-pressure injector product.

[0056] Figure 3 This is a cross-sectional view of the stress corrosion testing fixture provided in Embodiment 1 of the present invention.

[0057] Please refer to Figure 3 This invention provides a stress corrosion testing fixture, which includes a stress simulation component and a stress adjustment component. The stress simulation component includes a needle valve unit 08, a spring seat 09, and a telescopic spring 10. The two sides of the spring seat 09 are respectively connected to the telescopic spring 10 and the needle valve unit 08. The side of the needle valve unit 08 away from the spring seat 09 is used to abut against the test piece. The stress adjustment component includes a fixture housing and a stress loading unit connected to the fixture housing 06. The fixture housing and the stress loading unit form a cavity for accommodating the stress simulation component. The stress loading unit includes a sliding mechanism and a positioning mechanism. The sliding mechanism can move downwards along the axial direction of the fixture housing to apply stress to the test piece. The positioning mechanism can abut against or separate from the fixture housing to restrict the movement of the sliding mechanism.

[0058] It is worth noting that the stress loading unit in this embodiment can be a loading nut 07, the sliding mechanism is a nut sleeve, and the positioning mechanism is the thread on the nut sleeve. The loading nut is threadedly connected to the fixture housing. Depending on the specific implementation environment, the stress loading unit can also have other structures, as long as it can slide relative to the fixture housing 06 while also being self-locking onto the fixture housing 06. For example, the stress loading unit can be a sliding sleeve with a locking bolt for positioning.

[0059] Furthermore, the loading nut 07 has an interconnected nut through hole 071 and nut inner cavity 073.

[0060] It is worth noting that the stress corrosion testing fixture of the present invention is used to apply test stress to the test piece. The stress corrosion testing fixture provides a preload force according to the stress simulation component, and controls the extension and retraction feed of the telescopic spring 10 through the stress adjustment component, thereby ensuring that the test piece is subjected to a stable preload force at all times, and ensuring the consistency and accuracy of the stress corrosion test.

[0061] It is also worth noting that both the loading nut 07 and the clamp housing 06 have ridges on their outer sides. The number of ridges can be 2, 4, 6, etc., so as to facilitate clamping the loading nut 07 and the clamp housing 06 when the loading nut 07 is screwed in.

[0062] like Figure 3 As shown, the fixture housing 06 has a housing step 061 and a housing through hole 062 penetrating the housing step 061, through which the needle valve unit 08 passes. It is understood that both the test piece and the needle valve unit 08 extend to the outside through the housing through hole 062 to facilitate subsequent corrosion testing and avoid corrosion of the stress corrosion testing fixture. Furthermore, the housing step 061 at the bottom of the fixture housing 06 contacts the step on the valve sleeve 02, which can be used to support the test piece. Under the action of gravity, the test piece is abutted and locked against the housing step 061.

[0063] In this embodiment, the inner surface of the clamp housing 06 is provided with a first internal thread, and the outer surface of the loading nut 07 is provided with a first external thread that mates with the first internal thread. The mating portion of the first internal thread and the second external thread is the threaded portion 067. At this time, the diameter of the inner cavity 073 of the loading nut 07 is smaller than the diameter of the inner cavity 063 of the clamp housing 06, and the maximum outer diameter of the spring seat 09 is smaller than the diameter of the inner cavity 063 of the clamp housing 06. Alternatively, the maximum outer diameter of the spring seat 09 can be larger than the diameter of the inner cavity 073 of the loading nut 07. In this case, the spring seat 09 is installed in the inner cavity 063 of the clamp housing 06, and the inner cavity 063 of the clamp housing 06 serves to guide and straighten the spring seat 09. Conversely, the maximum outer diameter of the spring seat 09 can be smaller than the diameter of the inner cavity 073 of the loading nut 07. In this case, the spring seat 09 is installed in the inner cavity 073 of the loading nut 07, and the inner cavity 073 of the loading nut 07 serves to guide and straighten the spring seat 09. Understandably, depending on the specific implementation environment, the outer surface of the clamp housing 06 is provided with a second external thread (not shown in the figure), and the inner surface of the loading nut 07 is provided with a second internal thread (not shown in the figure) that mates with the second external thread. In this case, the diameter of the inner cavity 073 of the loading nut 07 is larger than the diameter of the inner cavity 063 of the clamp housing 06, and the maximum outer diameter of the spring seat 09 is smaller than the diameter of the inner cavity 073 of the loading nut 07. Alternatively, the maximum outer diameter of the spring seat 09 can be larger than the diameter of the inner cavity 063 of the clamp housing 06, in which case the spring seat 09 is installed in the inner cavity 073 of the loading nut 07, and the inner cavity 073 of the loading nut 07 serves to guide and straighten the spring seat 09. Conversely, the maximum outer diameter of the spring seat 09 can be smaller than the diameter of the inner cavity 063 of the clamp housing 06, in which case the spring seat 09 is installed in the inner cavity 063 of the clamp housing 06, and the inner cavity 063 of the clamp housing 06 serves to guide and straighten the spring seat 09.

[0064] In this embodiment, the needle valve unit 08 includes a rod and a valve ball 081 disposed at one end of the rod, and the end of the rod away from the valve ball 081 is connected to the spring seat 09.

[0065] It is worth noting that a needle valve unit 08 is installed inside the cavity of the test piece. The valve ball 081 of the needle valve unit 08 has a spherical structure, which contacts the sealing surface 011 of the valve seat 01's inner cavity. Optionally, to simulate the actual stress distribution of the welded assembly between the valve seat 01 and the valve sleeve 02 in the injector, the valve ball 081 of the needle valve unit 08 has the same dimensions as the injector's valve ball. This structural design improves the accuracy of stress simulation and further ensures the accuracy of the test.

[0066] Please refer to this again. Figure 3The needle valve unit 08 also includes a columnar connecting part 082, which is located at the end of the rod away from the valve ball part 081. The rod is connected to the spring seat 09 through the connecting part 082, and the diameter of the connecting part 082 is larger than the diameter of the rod.

[0067] Furthermore, the needle valve unit 08 also includes a positioning protrusion 083, which is located on the side of the connecting part 082 away from the rod body. The positioning protrusion 083 and the connecting part 082 cooperate to form a positioning step surface, and the positioning step surface abuts against the spring seat 09.

[0068] Furthermore, the spring seat 09 includes a connecting groove 094 and a spring groove 091 located on both sides and not connected to each other. The connecting groove 094 is provided with a positioning groove 093 that is adapted to the positioning protrusion 083. The inner surface of the connecting groove 094 abuts against the outer surface of the connecting part 082. The telescopic spring 10 is connected in the spring groove 091.

[0069] It is worth noting that the connecting part 082 at the tail end of the needle valve unit 08 is inserted into the corresponding connecting groove 094 at the bottom of the spring seat 09. The side of the connecting groove 094 serves to position and straighten the needle valve unit 08. The step surface positioning protrusion 083 at the tail end of the needle valve unit 08 contacts the positioning groove 093 in the connecting groove 094 at the bottom of the spring seat 09.

[0070] It is also worth noting that a telescopic spring 10 is installed in the spring groove 091 at the upper end of the spring seat 09. The spring groove 091 serves to position and straighten the telescopic spring 10. One end face of the telescopic spring 10 contacts the second bottom surface 092 in the spring groove 091 at the upper end of the spring seat 09.

[0071] Please refer to this again. Figure 3 The stress simulation component also includes a pad 11, one end of which is connected to the telescopic spring 10, and the other end of the pad 11 away from the telescopic spring 10 is close to the loading nut 07.

[0072] The pad 11 includes an embedded end, which is embedded in the extension spring 10.

[0073] It is worth noting that when the stress corrosion test fixture is not used, the upper end face of the pad 11 contacts the inner end face 072 of the loading nut 07, and the maximum outer diameter of the pad 11 and the outer diameter of the telescopic spring 10 are both smaller than the diameter of the inner cavity 073 of the loading nut 07. The first side end face 111 is then inserted into the telescopic spring 10.

[0074] In this embodiment, the maximum diameter of the pad 11 is greater than the diameter of the nut through hole 071. The pad 11 is also provided with a pad through hole 114 that communicates with the nut through hole 071.

[0075] It is understandable that the maximum diameter of the pad 11 being larger than the diameter of the nut through hole 071 can prevent the pad 11 from slipping off the loading nut 07. By creating a pad through hole 114 in the pad 11 that communicates with the nut through hole 071, when setting the loading force on the welded assembly (i.e., the test piece) of the valve seat 01 and valve sleeve 02 using a stress corrosion testing fixture, the loading force probe of the loading device can directly contact the first upper end face 112 of the pad 11 through the nut through hole 071 and apply the required force to the first upper end face 112 of the pad 11. The pad 11 transmits the force to the upper end face of the telescopic spring 10 through the first contact surface 113. The telescopic spring 10 compresses and deforms under force and transmits the force to the second bottom surface 092 of the spring seat 09 through its lower end face. The spring seat 09 transmits the force to the tail of the needle valve unit 08 through the lower positioning groove 093. The force is applied to the end positioning protrusion 083, and then the needle valve unit 08 transmits the force to the sealing surface 011 of the valve seat 01 through the valve ball part 081. Finally, the loading nut 07 is screwed in to a suitable depth so that the inner end face 072 of the nut cavity 073 just contacts the first upper end face 112 of the pad block 11, ensuring that the spring force of the telescopic spring 10 is the same as the required loading force. That is, the stress corrosion test fixture of this technical solution sets the required preload force for the welded assembly (i.e., test piece) of the valve seat 01 and valve sleeve 02 by controlling the compression of the telescopic spring 10. Finally, the loading force probe of the loading device is withdrawn to complete the preload force setting.

[0076] After the preload force is set, the loading force probe of the loading device can be re-contacted on the first upper end face 112 of the pad block 11 through the nut through hole 071 of the loading nut 07. Then, the loading force of the probe is gradually increased, and the spring force is measured by the loading force and the displacement change of the loading force probe to verify whether the preload force setting of the valve seat 01 and valve sleeve 02 welding assembly is accurate.

[0077] Furthermore, the through hole 114 in the center of the pad 11 can be used to calibrate the length of the spring after the required force is applied. The specific operation method is as follows: After the stress corrosion test fixture applies the required force to the welded assembly of valve seat 01 and valve sleeve 02, a probe is used to pass through the nut through hole 071 of the loading nut 07 and the pad through hole 114 of the pad 11. The end of the probe is perpendicularly contacted with the upper spring groove 091 of the spring seat 09. The distance from the second bottom surface 092 of the upper spring groove 091 of the spring seat 09 to the first upper surface 112 of the pad 11 or the upper surface 074 of the nut is measured and recorded. Subsequently, when the same loading force is set repeatedly, the screw-in depth of the loading nut 07 can be determined directly by measuring the distance from the second bottom surface 092 of the upper spring groove 091 of the spring seat 09 to the first upper surface 112 of the pad 11 or the upper surface 074 of the nut, so as to realize the application of the required force of the stress corrosion test fixture to the welded assembly of valve seat 01 and valve sleeve 02.

[0078] Example 2

[0079] Figure 4 This is a schematic diagram of a stress corrosion test provided in Embodiment 2 of the present invention; Figure 5 This is a flowchart illustrating the testing method provided in Embodiment 2 of the present invention.

[0080] Please refer to Figure 4 and Figure 5 This invention provides a testing method applicable to the stress corrosion testing fixture of any of Embodiments 1 and 3-8, comprising the following steps:

[0081] S1: Install the test piece in the fixture and apply a preset stress to the test piece.

[0082] Step S1 also includes steps S11 and S12, wherein:

[0083] S11: Apply a preset loading force to the pad block through an external loading device to control the spring seat below the telescopic spring to drive the needle valve unit to apply a first preset stress to the test piece;

[0084] S12: Screw in the stress loading unit so that the stress loading unit and the pad block abut against each other. Then continue to screw in the stress loading unit so that the spring seat below the telescopic spring drives the needle valve unit to apply the second preset stress to the test piece.

[0085] This method can simulate a precise stress environment through coarse and fine adjustments of the corresponding forces, and accurately and effectively evaluate the stress corrosion resistance of the valve seat 01 and valve sleeve welded assembly of the injector.

[0086] In addition, step S12 also includes using a probe to pass through the nut through hole 071 and the pad through hole 114, and making the end of the probe vertically contact the second bottom surface 092; measuring the first distance from the second bottom surface 092 to the first upper surface 112 or measuring the second distance from the second bottom surface 092 to the upper surface of the loading nut 07; and adjusting the sliding depth of the loading nut 07 by the first distance or the second distance.

[0087] S2: Prepare the stress corrosion test solution and pour it into the test container. It is understood that the test container in this embodiment can be a desiccant, etc.

[0088] S3: Place multiple prestressed fixtures on a tray, and then place the tray containing the test fixtures into a test container filled with stress corrosion test solution, ensuring that the corrosion test solution covers the test position of the test sample.

[0089] S4: Place the test container containing the tray and test solution into the temperature chamber, turn on the temperature chamber, set the ambient temperature inside the temperature chamber to the required temperature (i.e., the preset temperature to be tested), and start the stress corrosion test.

[0090] S5: Collect test data and analyze the stress corrosion resistance level of the test piece based on the test data.

[0091] In addition, step S2 may also include S21-S22.

[0092] S21. Prepare the stress corrosion test solution and test its composition and pH value to ensure it meets the preset range (the preset range is related to the corrosive environment when the engine is operating). The stress corrosion test solution is prepared to simulate the corrosive environment when the fuel injector is installed on the engine cylinder head. It is prepared using deionized water and a certain amount of chemical substances, mainly including calcium sulfate, magnesium chloride, potassium chloride, acetic acid, sodium hydroxide, hydrochloric acid, sulfuric acid, and nitric acid.

[0093] S22, Pour the stress corrosion solution into the test container, ensuring that the liquid level is below the bottom of the tray placed inside the test container. The test container can be a glass container or other containers, provided that the test container does not undergo a physical / chemical reaction with the stress corrosion solution.

[0094] Step S3 may include S31-S32

[0095] S31, Place multiple prestressed stress corrosion test fixtures and test pieces (i.e. test components) into the tray.

[0096] Specifically, the test components (i.e., the preloaded test specimens and the stress corrosion test fixtures) are placed on a tray. The tray has a number of through holes, each holding one test component. Valve seat 01 and part of valve sleeve 02 extend through the through holes. The lower end face 064 of the fixture housing 06 contacts the upper surface of the tray. The test specimens are arranged on the tray as follows: Figure 4 As shown.

[0097] S32, Place the tray and the stress corrosion test fixture and test piece on the tray into the test container.

[0098] Specifically, the tray and the test components on it are placed into the test container. The valve seat 01 and part of the valve sleeve 02 are submerged in the stress corrosion test solution. The solution level is ensured to be a certain distance above the valve seat 01 and the welded area 012 of the valve seat 01 and valve sleeve 02, ensuring that the valve seat 01 and the welded area 012 are completely submerged in the stress corrosion test solution throughout the test. Simultaneously, the solution level must be lower than the bottom of the tray inside the test container to prevent the stress corrosion test solution from contacting the stress corrosion test fixture and corroding it, and also to prevent the stress corrosion solution from entering the inner cavity of the welded assembly of the valve seat 01 and valve sleeve 02.

[0099] S4. After sealing the test container, place it in the temperature chamber, adjust the temperature to the preset temperature, and start the stress corrosion test.

[0100] Specifically, the test container is covered, and the test container, its internal stress corrosion test solution, and test components are placed in the temperature chamber. Then, the temperature chamber is turned on, and the ambient temperature inside the chamber is set to the preset temperature before the stress corrosion test begins.

[0101] Step S5 also includes S51-S53, wherein:

[0102] S51 is the sampling procedure.

[0103] Specifically, during the test, samples need to be checked at regular intervals to record whether stress corrosion cracking occurs in each test component. The time spent checking samples after the temperature chamber is powered off and then opened should be less than 5 minutes, and the temperature chamber should be restarted immediately after the check to minimize the impact of the check on the test process. If, during the test, the stress corrosion solution level is still submerged in the valve seat 01 and the welded area 012 of the valve seat 01 and valve sleeve 02, but is already quite close to the welded area 012 of the valve seat 01 and valve sleeve 02, the same amount of stress corrosion test solution needs to be replenished in a timely manner to ensure that the valve seat 01 and the welded area 012 of the valve seat 01 and valve sleeve 02 are completely submerged in the stress corrosion test solution during the test.

[0104] S52. After the stress corrosion test is completed, the temperature chamber is powered off, the test specimens and equipment are removed and cleaned, and the stress corrosion solution is properly treated.

[0105] S53, analyze the stress corrosion cross-section of the failed sample and the time when stress corrosion fracture occurs, and evaluate the stress corrosion resistance level of the welded test pieces of valve seat 01 and valve sleeve 02.

[0106] It is worth noting that this testing method can simulate real working conditions and accurately and effectively evaluate the stress corrosion resistance of the welded components of the valve seat 01 and valve sleeve 02 of the injector.

[0107] Example 3

[0108] Figure 6 This is a cross-sectional view of the needle valve unit 08 provided in Embodiment 3 of the present invention.

[0109] In this embodiment 3, except for the different structure of the needle valve unit 08, the other structures are the same as in embodiment 1, and will not be described again here.

[0110] like Figure 6 As shown, the upper end of the needle valve unit 08 is designed as a straight rod, and the upper end of the needle valve unit 08 can directly extend into the slot 086 of the corresponding size at the lower end of the spring seat 09.

[0111] The needle valve unit 08 features a simple structure, which is conducive to mass production in industry.

[0112] Example 4

[0113] Figure 7 This is a cross-sectional view of the needle valve unit 08 provided in Embodiment 4 of the present invention.

[0114] In this embodiment 4, except for the different structure of the needle valve unit 08, the other structures are the same as in embodiment 1, and will not be described again here.

[0115] like Figure 7 As shown, the needle valve unit 08 also includes a cylindrical flat-headed cylinder 085, which is located at the end of the rod away from the valve ball 081. The rod is connected to the spring seat 09 through the flat-headed cylinder 085, and the diameter of the flat-headed cylinder 085 is larger than the diameter of the rod.

[0116] Specifically, to increase the stability of the assembly of the stress corrosion test fixture and the force transmission of the needle valve unit 08, a flat-headed cylinder 085 with a diameter slightly larger than that of the middle rod of the needle valve unit 08 can be used at the upper end of the needle valve unit 08. The flat-headed cylinder 085 of the needle valve unit 08 can be directly inserted into the slot 086 of the corresponding size at the lower end of the spring seat 09. The flat-headed cylinder 085 of the needle valve unit 08 can also adopt a non-cylindrical structure design, such as a polygonal prism design.

[0117] Compared to embodiment 3, the needle valve unit 08 has better force transmission due to the flat-headed cylinder 085, and can be more stably engaged with the spring seat 09.

[0118] Example 5

[0119] Figure 8 This is a cross-sectional view of the needle valve unit 08 and spring seat 09 provided in Embodiment 5 of the present invention.

[0120] In this embodiment 5, except for the different structures of the needle valve unit 08 and the spring seat 09, the other structures are the same as in embodiment 1, and will not be described again here.

[0121] like Figure 8 As shown, the needle valve unit 08 also includes a slot 086, which is located at the end of the rod away from the valve ball 081, and the rod is connected to the spring seat 09 through the slot 086. The spring seat 09 includes a base protrusion 095 and a spring groove 091 that are connected to each other and located on both sides, and the base protrusion 095 and the slot 086 are adapted to each other.

[0122] Specifically, the tail end of the needle valve unit 08 adopts a slot 086 design, and the lower end of the corresponding spring seat 09 adopts a base protrusion 095 design. The base protrusion 095 of the spring seat 09 extends into the slot 086 of the needle valve unit 08. The lower end face 097 of the protrusion of the base protrusion 095 of the spring seat 09 contacts the first bottom surface 087 of the tail end slot 086 of the needle valve unit 08, or the first stepped surface 096 of the spring seat 09 contacts the first top surface 088 of the needle valve unit 08.

[0123] Example 6

[0124] Figure 9 This is a cross-sectional view of the needle valve unit 08 and spring seat 09 provided in Embodiment 6 of the present invention.

[0125] In this embodiment 6, except for the different structures of the needle valve unit 08 and the spring seat 09, the other structures are the same as in embodiment 1, and will not be described again here.

[0126] like Figure 9 As shown, the needle valve unit 08 and the spring seat 09 are integrally formed or fixedly connected.

[0127] It's worth noting that one-piece molding is primarily used in manufacturing, meaning a part is manufactured in a single process, eliminating the need for secondary or subsequent processing. The entire process completes the manufacturing of a part in a single step. One-piece molding and non-one-piece molding are two different manufacturing processes. The resulting product or part is a single unit without any connections, resulting in higher quality and longer lifespan compared to non-one-piece molding. Here, a one-piece molded needle valve unit 08 and spring seat 09 can be used to improve its overall service life.

[0128] Example 7

[0129] Figure 10 This is a cross-sectional view of the spring seat 09 provided in Embodiment 7 of the present invention.

[0130] In this embodiment 7, except for the different structure of the spring seat 09, the other structures are the same as in embodiment 1, and will not be described again here.

[0131] like Figure 10As shown, a support step 099 is provided in the spring groove 091, and the support protrusion 098 of the support step 099 passes through the telescopic spring 10. The step surface of the support step 099 abuts against the telescopic spring 10.

[0132] Specifically, the structure of the upper end of the spring seat 09 contacting the telescopic spring 10 can adopt a stepped structure design with a central protrusion. The lower end face of the spring contacts the supporting step 099 at the upper end of the spring seat 09. The supporting protrusion 098 at the center of the upper end of the spring seat 09 extends into the center of the telescopic spring 10, which plays the role of straightening and positioning the telescopic spring 10.

[0133] Example 8

[0134] Figure 11 This is a cross-sectional view of the pad 11 provided in Embodiment 7 of the present invention.

[0135] In this embodiment 8, except for the different structure of the spring seat 09, the other structures are the same as in embodiment 1, and will not be described again here.

[0136] like Figure 11 As shown, the pad 11 includes a pad groove end 115, which is sleeved on the telescopic spring 10.

[0137] Specifically, the lower end of the pad 11 can adopt a circular groove structure design, that is, the upper end face of the extension spring 10 extends into the circular groove end 115 of the pad 11 and contacts the bottom surface 116 of the circular groove. The wall surface of the circular groove end 115 of the pad serves to position and straighten the spring. The through hole 114 of the pad is an optional design and is used for spring compression height calibration.

[0138] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

[0139] Finally, it should be understood that the embodiments in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments in this specification are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments in this specification are not limited to those explicitly described and illustrated herein.

Claims

1. A fixture for stress corrosion testing, characterized in that, include: A stress simulation assembly includes a needle valve unit, a spring seat, and a telescopic spring. The two sides of the spring seat are respectively connected to the telescopic spring and the needle valve unit. The side of the needle valve unit away from the spring seat is used to abut against the test piece. The needle valve unit includes a rod and a valve ball portion disposed at one end of the rod. The end of the rod away from the valve ball portion is connected to the spring seat. The test piece is a welded assembly of a valve seat and a valve sleeve. A stress adjustment assembly includes a fixture housing and a stress loading unit connected to the fixture housing. The fixture housing and the stress loading unit form a cavity for accommodating the stress simulation assembly. The stress loading unit includes a sliding mechanism and a positioning mechanism. The sliding mechanism is capable of moving downward along the axial direction of the fixture housing to apply stress to the test piece. The positioning mechanism is capable of abutting against or separating from the fixture housing to limit the movement of the sliding mechanism.

2. The stress corrosion testing fixture according to claim 1, characterized in that, A pad is also provided between the stress loading unit and the telescopic spring. When the stress loading unit moves downward, one end of the pad can abut against the stress loading unit, and the other end can abut against the telescopic spring.

3. The stress corrosion testing fixture according to claim 2, characterized in that, Both the stress loading unit and the pad have interconnected through holes at their centers, and the maximum diameter of the pad is larger than the diameter of the through hole in the stress loading unit.

4. The stress corrosion testing fixture according to claim 1, characterized in that, The stress loading unit is a loading nut, the sliding mechanism is a nut sleeve, the positioning mechanism is the thread on the nut sleeve, and the loading nut is threadedly connected to the fixture housing.

5. The stress corrosion testing fixture according to claim 4, characterized in that, The rod body has a connecting part at one end, and the spring seat has a connecting groove in the middle that matches the shape of the connecting part. The rod body is inserted into the spring seat through the connecting part and the connecting groove, and the diameter of the connecting part is larger than the diameter of the rod body.

6. The stress corrosion testing fixture according to claim 5, characterized in that, The connecting part is also provided with a positioning protrusion, which cooperates with the connecting part to form a positioning step surface, and the positioning step surface abuts against the spring seat.

7. The stress corrosion testing fixture according to claim 1, characterized in that, The end face of the spring seat that connects to the telescopic spring is provided with a spring groove, and the telescopic spring is connected in the spring groove.

8. The stress corrosion testing fixture according to claim 1, characterized in that, The middle end face of the spring seat connected to the telescopic spring is provided with a support protrusion, and the telescopic spring is sleeved on the support protrusion.

9. The stress corrosion testing fixture according to claim 1, characterized in that, The needle valve unit is integrally formed with the spring seat.

10. A test method using the stress corrosion testing fixture according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Install the test piece in the fixture and apply a preset stress to the test piece; S2: Prepare the stress corrosion test solution and pour the stress corrosion test solution into the test container; S3: Place multiple prestressed fixtures on a tray, and place the tray containing the test fixtures into a test container containing stress corrosion test solution, so that the corrosion test solution covers the test position of the test sample. S4: Place the test container containing the tray and test solution into the temperature chamber, turn on the temperature chamber, set the ambient temperature inside the temperature chamber to the required temperature, and start the stress corrosion test. S5: Collect test data and analyze the stress corrosion resistance level of the test piece based on the test data.

11. The test method according to claim 10, characterized in that, A pad is also provided between the stress loading unit and the telescopic spring. When the stress loading unit moves downward, one end of the pad can abut against the stress loading unit and the other end can abut against the telescopic spring. Step S1 also includes: S11: Apply a preset loading force to the pad block through an external loading device to control the spring seat below the telescopic spring to drive the needle valve unit to apply a first preset stress to the test piece; S12: Screw in the stress loading unit so that the stress loading unit abuts against the pad, and then continue to screw in the stress loading unit so that the spring seat below the telescopic spring drives the needle valve unit to apply a second preset stress to the test piece.

12. The test method according to claim 11, characterized in that, The end face of the spring seat that connects to the telescopic spring is provided with a spring groove, and the telescopic spring is connected in the spring groove; Step S12 also includes: Use a probe to pass through the through-holes of the stress loading unit and the pad through-holes, and make vertical contact between the end of the probe and the second bottom surface; Measure the first distance from the second bottom surface to the first top surface, or measure the second distance from the second bottom surface to the top surface of the stress loading unit; The sliding depth of the stress loading unit can be adjusted by the first distance or the second distance; Wherein, the second bottom surface is the bottom surface of the spring groove, and the first upper surface is the upper surface of the pad.

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