Ultra-large pressure stress jam-free hydrogen-induced delayed cracking experiment device and method

Abstract

The invention belongs to the technical field of testing devices, and relates to an ultra-large pressure stress jam-free hydrogen-induced delayed cracking experiment device and method. The device comprises a four-point bending clamp, the four-point bending clamp is arranged to clamp a bending sample and comprises a base, a pressing block, a bearing plate, a force transmission column and a clamp fastening bolt, the base defines a cavity with a downward opening, the pressing block is contained in the cavity and matched with the base to clamp the bending sample in a four-point supporting mode, and the bearing plate is arranged on the base; the force transmission column penetrates through the base to be supported between the pressing block and the bearing plate, and the clamp fastening bolt detachably locks the base and the bearing plate. The auxiliary bending bracket is arranged to support the four-point bending clamp; and the loading mechanism is arranged to apply stress to the bending sample. The device solves the problems that the sample for the ultra-large hydrogen-induced delayed cracking experiment is difficult to pre-bend, and the stud is blocked and the loading block falls off in the using process of the existing four-point bending device.

Description

Technical Field

[0001] The invention belongs to the technical field of testing devices, and relates to an ultra-large compressive stress non-stuck hydrogen-induced delayed cracking experimental device and method. Background Art

[0002] In the automotive industry, 1000MPa grade steels such as hot stamping steel (PHS), CP steel, DP steel, etc. are ultra-high strength steels with a high risk of hydrogen-induced delayed cracking (hydrogen embrittlement). Every year, 500 million ultra-high strength steel parts are used in automobiles around the world, using more than 6 million tons of materials. The potential hydrogen-induced delayed cracking of automotive steel parts with strengths above 1000MPa is one of the most worrying issues for OEMs, and is a difficult, focal, and hot issue in the current automotive manufacturing industry. Therefore, hydrogen-induced delayed cracking (hydrogen embrittlement) performance has become an indispensable performance evaluation indicator for ultra-high strength steel.

[0003] The four-point bending test is one of the commonly used methods for testing the mechanical properties of materials. It can be used to determine the material's performance parameters such as bending strength and elastic modulus. Compared with three-point bending, four-point bending can form a pure bending area in the middle section of the specimen, reducing the influence of shear force and allowing the test results to more accurately reflect the true bending characteristics of the material. In the experiment, the specimen is placed on a fixture with four support points, and external forces are applied at two loading points to cause the specimen to bend and deform.

[0004] Patent CN207423661U discloses a four-point bending test fixture device, which includes a fixture base, and both ends of the bottom of the fixture base are symmetrically arranged with "L"-shaped support parts downward, and an accommodating cavity is formed between the upper part of the two support parts and the fixture base, and a loading block is arranged in the accommodating cavity. Two parallel semicircular upper grooves are correspondingly arranged at both ends of the bottom surface of the loading block, and two parallel semicircular lower grooves are correspondingly arranged on the bottom surfaces of the two support parts, and quartz rods can be placed in the upper grooves and the lower grooves. Patent CN207623155U discloses a four-point bending test device, including a fixed seat and a loading member, wherein a cavity for placing a specimen is arranged in the fixed seat, a loading cavity is arranged above the cavity, the loading member is arranged in the loading cavity, two supports are symmetrically arranged on the loading member, a loading screw is arranged on the fixed seat, the loading screw end passes through the fixed seat and extends into the loading cavity, the loading screw and the fixed seat are connected by a thread, support seats are symmetrically arranged on both sides of the lower end of the fixed seat, the support seats are symmetrically arranged on the fixed seat toward the cavity direction, and a support is respectively arranged on the support seats.

[0005] The above-mentioned existing typical four-point bending test fixture devices all use the loading screw as the pressure transmission element, and the specimen is bent by rotating the loading screw. However, in the actual ultra-high strength automotive steel hydrogen embrittlement evaluation process, some automobile OEMs have put forward more stringent requirements for hydrogen embrittlement test specimens, and the specimens have been increased from the original 15*115*thickness (mm) to 25*125*thickness (mm). With the increase in the strength of ultra-high strength steel, the bending force required for its hydrogen embrittlement test will increase significantly, making it difficult for conventional hydrogen embrittlement four-point bending devices to carry out relevant tests. This is mainly because the stress applied to the specimen is too large, and it is difficult to bend the specimen by twisting the bolts with tools such as wrenches. At the same time, the conventional four-point bending equipment for evaluating hydrogen embrittlement often has the hydrogen embrittlement device bolts or pressure blocks stuck and falling off when applying or unloading stress, which brings many inconveniences to the implementation of the experiment.

[0006] Therefore, it is urgent to invent a non-blocking hydrogen-induced delayed cracking experimental device and method that can implement ultra-large compressive stress. Summary of the invention

[0007] In view of this, the present invention proposes an ultra-large compressive stress non-stuck hydrogen-induced delayed cracking test device and method to solve the problems of difficulty in pre-bending specimens for ultra-large hydrogen-induced delayed cracking experiments and stud sticking and loading block falling off during the use of existing four-point bending devices.

[0008] In order to solve at least one of the above technical problems, the present invention adopts the following technical solution: According to one aspect of the present invention, there is provided an ultra-large compressive stress non-blocking hydrogen-induced delayed cracking experimental device, comprising: a four-point bending fixture, configured to clamp a bending specimen, comprising: a base, a pressure block, a bearing plate, a force transfer column and a fixture fastening bolt, wherein the base defines a downwardly open cavity, the pressure block is accommodated in the cavity and cooperates with the base to clamp the bending specimen in a four-point support manner, the force transfer column passes through the base and is supported between the pressure block and the bearing plate, and the fixture fastening bolts can detachably lock the base and the bearing plate; an auxiliary bending bracket, configured to support the four-point bending fixture; and a loading mechanism, configured to apply stress to the bending specimen.

[0009] According to one embodiment of the present invention, the base is provided with a pair of first support points extending upward toward the cavity; the pressing block is provided with a pair of second support points extending downward on the lower surface, wherein the distance between the first support points is greater than the distance between the second support points; and the bending specimen is arranged between the first support points and the second support points to form a four-point support.

[0010] According to one embodiment of the present invention, the force transmission column is a finely polished column having a hollow columnar structure and internal threads are respectively provided at both ends, and the four-point bending fixture also includes: a first fixing bolt, which is configured to pass through the threaded connection between the bearing plate and one end of the force transmission column to fix the bearing plate to the force transmission column; and a second fixing bolt, which is configured to pass through the threaded connection between the pressure block and the other end of the force transmission column to fix the pressure block to the force transmission column.

[0011] According to one embodiment of the present invention, the auxiliary bending bracket comprises: a support base, comprising a bottom plate and a U-shaped frame extending vertically perpendicular to the bottom plate, the U-shaped frame having an upper opening and defining a cross-shaped groove to accommodate the four-point bending fixture and at least a portion of the loading mechanism; and A cover plate is detachably fixedly connected to the top of the U-shaped frame to close its opening, and a through hole is provided in the middle of the cover plate to allow a part of the loading mechanism to pass through the cover plate to apply stress to the bending specimen.

[0012] According to one embodiment of the present invention, the auxiliary bending bracket also includes: a clamp positioning mechanism, including a positioning mechanism body and a clamp positioning bolt, wherein the positioning mechanism body is relatively fixed to the U-shaped frame, and the clamp positioning bolt passes through the positioning mechanism body and is connected to the four-point bending clamp.

[0013] According to one embodiment of the present invention, the loading mechanism includes: a pressure core shaft, which is configured to pass through the cover plate and abut against the supporting plate; a sleeve, which is circumferentially sleeved on the outside of the pressure core shaft and fixedly connected to the cover plate; and a pressure component, which is configured to apply pressure to the pressure core shaft so that the pressure core shaft moves downward relative to the sleeve.

[0014] According to an embodiment of the present invention, the pressure component is a pressure rod, one end of which is pivotally connected to the top of the sleeve, and the middle portion of the pressure rod abuts against the top of the pressure mandrel.

[0015] According to one embodiment of the present invention, the pressure component is a hydraulic press, and the output end of the hydraulic press abuts against the top of the pressure mandrel.

[0016] According to one embodiment of the present invention, the device also includes a displacement measuring mechanism, which is configured to measure the change in deflection of the bending specimen during the bending process. The displacement measuring mechanism includes: a measuring instrument, which is arranged below the middle position of the bending specimen to measure the vertical displacement of the middle position of the bending specimen; and a measuring frame, which supports the measuring instrument.

[0017] According to another aspect of the present invention, a method for testing delayed hydrogen-induced cracking under ultra-large compressive stress without blocking is provided, and any of the above-mentioned devices is used for the experiment. The method comprises the following steps: clamping the bending specimen between the base and the pressure block of the four-point bending fixture; placing the assembled four-point bending fixture into the auxiliary bending bracket, and completing the assembly of the loading mechanism and the auxiliary bending bracket; starting the loading mechanism to apply stress to the bending specimen, and after the bending specimen is bent to a predetermined state, using the fixture fastening bolts to lock the base and the load-bearing plate of the four-point bending fixture; taking the four-point bending fixture out of the auxiliary bending bracket, placing it in the hydrogen embrittlement test solution, and recording the cracking of the specimen.

[0018] By adopting the above technical solution, the present invention has at least one of the following advantages compared with the prior art: (1) The device according to the present invention uses a hydraulic loading device as a pressure source, and can implement the bending of super-large hydrogen-induced delayed cracking test specimens. The hydraulic loading device is extremely easy to operate, avoiding the bending of the specimen by twisting the studs with tools such as wrenches, saving effort and time, and easily achieving the bending of larger specimens.

[0019] (2) According to the device of the present invention, a measuring frame is designed to fix the measuring instrument for adjusting the deflection of the sample, thereby achieving adjustment of different deflections.

[0020] (3) The device according to the present invention breaks the conventional screw-type force transmission mode for advanced bending. The force transmission column is a finely polished column obtained by fine grinding of the outer surface. The whole column is smooth and has no obstruction. It can smoothly transmit force to the pressing block to implement sample bending, effectively avoiding the sticking phenomenon in the bending loading and unloading process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A schematic diagram of a super-large compressive stress non-stuck hydrogen-induced delayed cracking experimental device according to an embodiment of the present invention is shown; Figure 2 Shows Figure 1 The front view of the ultra-large compressive stress non-blocking hydrogen-induced delayed cracking experimental device shown; Figure 3 Shows Figure 1 The side view of the ultra-large compressive stress non-blocking hydrogen-induced delayed cracking experimental device shown; Figure 4 Shows Figure 1 The top view of the ultra-large compressive stress non-stuck hydrogen-induced delayed cracking experimental device shown; Figure 5 Shows Figure 1 The cross-sectional view of the ultra-large compressive stress non-stuck hydrogen-induced delayed cracking experimental device shown; Figure 6 A schematic diagram of a four-point bending fixture according to an embodiment of the present invention is shown; Figure 7 Shows Figure 6 A front view of the four-point bending fixture is shown; Figure 8 Shows Figure 6 A side view of the four-point bending fixture is shown; Fig. 9 Shows Figure 6 A cross-sectional view of the four-point bending fixture shown; Fig.10 A schematic diagram of a base according to an embodiment of the present invention is shown; Fig.11 A schematic diagram of a pressing block according to an embodiment of the present invention is shown; Fig.12 A schematic diagram of a carrier plate according to an embodiment of the present invention is shown; Fig.13 A schematic diagram of a force transmission column according to an embodiment of the present invention is shown; Fig.14 A schematic diagram of a support base according to an embodiment of the present invention is shown; Fig.15 A schematic diagram of a cover plate according to an embodiment of the present invention is shown; Fig.16 Shows Fig.15 a cross-sectional view of the cover plate shown; Fig.17 A schematic diagram of a measuring mechanism according to an embodiment of the present invention is shown; Fig.18 A schematic diagram of a measuring frame according to an embodiment of the present invention is shown.

[0023] In the figure, 10. Bending specimen; 100, four-point bending fixture, 110, base, 111, first groove, 112, lower support column, 113, first through hole, 114, first threaded hole, 115, protrusion, 120, pressing block, 121, second groove, 122, upper support column, 123, second through hole, 130, bearing plate, 131, third through hole, 132, fourth through hole, 140, force transmission column, 141, upper threaded hole, 142, lower threaded hole, 150, first fixing bolt, 160, second fixing bolt, 170, fixture fastening bolt, 180, flat round head screw; 200, auxiliary bending bracket, 210, support seat, 211, bottom plate, 212, U-shaped frame, 220, cover plate, 221, fifth through hole, 222, sixth through hole, 223, bracket fastening bolt, 230, fixture positioning mechanism, 231, positioning mechanism body, 232, fixture positioning bolt, 300, loading mechanism, 310, pressure mandrel, 320, sleeve, 330, pressure rod; 400. displacement measuring mechanism, 410. measuring instrument, 420. measuring frame, 421. strip hole, 422. fixing hole. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0025] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are only illustrative. Although only a few embodiments are described in detail in the present invention, it is easy for those skilled in the art to appreciate that multiple modifications are feasible without actually departing from the teaching of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Without departing from the gist of the present invention, other replacements, modifications, changes and deletions may be made to the design, operating conditions and parameters of the following exemplary embodiments.

[0026] According to one aspect of the present invention, an embodiment of the present invention provides an ultra-large compressive stress non-stuck hydrogen-induced delayed cracking experimental device, such as Figure 1-5 As shown, it generally comprises: a four-point bending fixture 100 configured to clamp the bending specimen 10 , an auxiliary bending bracket 200 configured to support the four-point bending fixture 100 , and a loading mechanism 300 configured to apply stress to the bending specimen 10 .

[0027] Figure 6-13The schematic diagram of a four-point bending fixture 100 and some of its components according to an embodiment of the present invention is shown. In this embodiment, the four-point bending fixture 100 generally comprises: a base 110, a pressure block 120, a bearing plate 130, a force transmission column 140 and a fixture fastening bolt 170. The base 110 defines a cavity opening downward, the pressure block 120 is accommodated in the cavity and cooperates with the base 110 to clamp the bending specimen 10 in a four-point support manner, and the force transmission column 140 passes through the base 110 and is supported between the pressure block 120 and the bearing plate 130. The fixture fastening bolt 170 detachably locks the base 110 and the bearing plate 130.

[0028] Specific as Fig.10 As shown, the base 110 is generally composed of a main body portion extending laterally and L-shaped structures extending downward symmetrically from both ends of the main body portion and opposite to each other, and defining a downwardly open cavity. The main body portion of the base 110 is provided with a first through hole 113 in the middle for the force transmission column 140 to pass through. Preferably, a pair of protrusions 115 extend symmetrically downward from the main body portion of the base 110. The distance between the pair of protrusions 115 is smaller than the distance between the bottoms of a pair of L-shaped structures, and the space formed by the protrusions 115 and the bottom surface of the main body portion of the base 110 can be used to accommodate the pressing block 120. Furthermore, the base 110 is provided with a pair of first support points extending upward toward the cavity. In combination Figure 6 and Fig.10 The bottom of the L-shaped structure may be provided with a first groove 111 which is recessed downwards, and a first support point is provided by detachably installing a lower support column 112 in the first groove 111. The lower support column 112 may be a ceramic rod or a rod-shaped component made of other insulating high-strength materials.

[0029] like Fig.11 As shown, the pressing block 120 is provided with a pair of second support points extending downward on the lower surface. The distance between the first support points is greater than the distance between the second support points, and the bending specimen 10 is provided between the first support points and the second support points to form a four-point support. Figure 6 and Fig.11 The bottom sides of the pressing block 120 may be provided with second grooves 121 that are recessed upwards, and a second support point is provided by detachably installing an upper support column 122 in the second groove 121. Similar to the lower support column 112, the upper support column 122 may also be a ceramic rod or a rod-shaped component made of other insulating high-strength materials.

[0030] Combination Fig. 9 and Figure 12-13, the force transmission column 140 is a finely ground column, specifically a cylindrical structure with a high-precision grinding of the outer surface. On the one hand, the surface of the finely ground column is very smooth, which can ensure that the pressure can be evenly distributed on the contact surface when transmitting pressure, avoiding the situation of excessive local pressure, making the pressure distribution uniform, and completely avoiding the occurrence of blocking; on the other hand, the smooth surface makes the light column have less energy loss when transmitting pressure, which can effectively improve the transmission efficiency. Just like in a hydraulic system, the finely ground column can well transmit the liquid pressure and reduce pressure loss. Further, the force transmission column 140 can have a hollow columnar structure and be provided with internal threads at both ends, forming an upper threaded hole 141 and a lower threaded hole 142, so as to fix and connect the bearing plate 130 and the pressure block 120 at both ends. In an embodiment of the present invention, the four-point bending fixture 100 also includes a first fixing bolt 150 and a second fixing bolt 160. A second through hole 123 is provided through the middle of the pressure block 120, and a third through hole 131 is also provided through the middle of the bearing plate 130. The apertures of the second through hole 123 and the third through hole 131 are both smaller than the diameter of the force transmission column 140. The first fixing bolt 150 is configured to pass through the upper threaded hole 141 of the bearing plate 130 and the force transmission column 140 to be threadedly connected, so as to be fixedly connected to the third through hole 131 of the bearing plate 130 and the force transmission column 140; the second fixing bolt 160 is configured to pass through the second through hole 123 of the pressing block 120 and the lower threaded hole 142 of the force transmission column 140 to be threadedly connected, so as to be fixedly connected to the pressing block 120 and the force transmission column 140.

[0031] Combination Fig.10 and Fig.12 , the bearing plate 130 is symmetrically provided with a pair of fourth through holes 132 on both sides of the third through hole 131 for the clamp fastening bolts 170 to pass through; the base 110 is symmetrically provided with a pair of first threaded holes 114 on both sides of the first through hole 113 for threaded connection with the clamp fastening bolts 170. Thus, the clamp fastening bolts 170 pass through the fourth through holes 132 of the bearing plate 130 and are screwed into the first threaded holes 114 of the base 110 to achieve locking of the bearing plate 130 and the base 110. Further preferably, a plurality of limiting bolt holes are evenly arranged on the bearing plate 130 for screwing in limiting bolts to limit the position of the bearing plate 130 during the loading process to prevent it from rotating.

[0032] like Figure 6-8 As shown, the four-point bending fixture 100 can be provided with a plurality of threaded holes at the junctions of the adjacent base 110 and the pressing block 120, the base 110 and the lower support column 112, and the pressing block 120 and the upper support column 122. After the various parts are assembled, a flat round head screw 180 is screwed into the threaded hole, and the screw head of the flat round head screw 180 is used to press the two adjacent parts to limit the lateral displacement of the two parts.

[0033] Figure 14-16FIG. 2 is a schematic diagram of an auxiliary bending bracket 200 and some of its components according to an embodiment of the present invention. The auxiliary bending bracket 200 includes a detachably connected support base 210 and a cover plate 220. Fig.14 As shown, the support base 210 includes a bottom plate 211 and a U-shaped frame 212 extending vertically perpendicular to the bottom plate 211. The U-shaped frame 212 has an opening on the top and defines a cross-shaped groove to accommodate the four-point bending fixture 100 and at least a portion of the loading mechanism 300. The four-point bending fixture 100 can be clamped at a wider position in the middle of the cross-shaped groove. Figure 15-16 As shown, a fifth through hole 221 is provided in the middle of the cover plate 220 to allow a portion of the loading mechanism 300 to pass through the cover plate 220 to apply stress to the bending specimen 10. The cover plate 220 is detachably fixedly connected to the top of the U-shaped frame 212 to close its opening. For example, a pair of sixth through holes 222 are symmetrically provided on both sides of the fifth through hole 221, and the bracket fastening bolts 223 pass through the sixth through holes 222 and are screwed into the threaded holes on the top of the U-shaped frame 212 to achieve the fixation of the two. Further, as shown in FIG. Figure 3-4 As shown, the auxiliary bending bracket 200 also includes a clamp positioning mechanism 230. The clamp positioning mechanism 230 may include a positioning mechanism body 231 and a clamp positioning bolt 232. The positioning mechanism body 231 is relatively fixed to the U-shaped frame 212, or may be integrally formed with the U-shaped frame 212. The clamp positioning bolt 232 passes through the positioning mechanism body 231 and is connected to the four-point bending fixture 100.

[0034] Combination Figure 1-5 As shown, the loading mechanism 300 includes a pressure mandrel 310, a sleeve 320 and a pressure component. The pressure mandrel 310 is configured to pass through the cover plate 220 and abut against the carrier plate 130. The sleeve 320 is circumferentially sleeved outside the pressure mandrel 310 and is fixedly connected to the cover plate 220. The pressure component is configured to apply pressure to the pressure mandrel 310 so that the pressure mandrel 310 moves downward relative to the sleeve 320. In one embodiment of the present invention, the loading mechanism 300 may be a manual loading mechanism, and its pressure component is a pressure rod 330, one end of the pressure rod 330 is pivotally connected to the top of the sleeve 320, and the middle part of the pressure rod 330 abuts against the top of the pressure mandrel 310. In another embodiment of the present invention, the loading mechanism 300 may be a mechanical loading mechanism, and its pressure component is a hydraulic press, and the output end of the hydraulic press abuts against the top of the pressure mandrel 310.

[0035] Preferably, the device according to the present invention further includes a displacement measuring mechanism 400, which can be configured to measure the change in deflection of the bending specimen 10 during the bending process. Specifically, the displacement measuring mechanism 400 may include a measuring instrument 410 and a measuring frame 420 for supporting the measuring instrument 410. The measuring instrument 410 may be disposed below the middle position of the bending specimen 10 to measure the vertical displacement of the middle position of the bending specimen 10. In an embodiment of the present invention, the measuring instrument 410 may be an inverted dial indicator, micrometer, or a similar measuring instrument. During measurement, the measuring contact of the measuring instrument 410 may be placed against the middle part of the bending specimen 10. Figure 17-18 As shown, the measuring frame 420 may be in an inverted L-shape, with a fixing hole 422 for fixing the measuring instrument 410 provided at its bent end, and a longitudinal strip hole 421 provided at the other end. The operator may use a screw to pass through the strip hole 421 to fix the measuring frame 420 to the support seat 210, and adjust the specific height of the measuring instrument 410 by adjusting the specific position of the bolt passing through the strip hole 421.

[0036] According to another aspect of the present invention, an embodiment of the present invention provides a method for testing ultra-large compressive stress non-stuck hydrogen-induced delayed cracking, which specifically includes the following steps: S101, clamping the bending specimen 10 between the base 110 and the pressing block 120 of the four-point bending fixture 100; S102, placing the assembled four-point bending fixture 100 into the auxiliary bending bracket 200, and completing the assembly of the loading mechanism 300 and the auxiliary bending bracket 200; S103, starting the loading mechanism 300 to apply stress to the bending specimen 10, and after the bending specimen 10 is bent to a predetermined state, using the fixture fastening bolts 170 to lock the base 110 and the bearing plate 130 of the four-point bending fixture 100; S104, taking out the four-point bending fixture 100 from the auxiliary bending bracket 200, placing it in a hydrogen embrittlement test solution, and recording the cracking condition of the sample.

[0037] Taking 1500MPa grade hot-formed steel as an example, the tensile strength after tempering is about 1400MPa, the material thickness is 1.8mm, and the sample size is 40mm*120mm. The loading stress is 100% of the tensile strength, and the deflection y converted is 9.8mm.

[0038] The four-point bending fixture 100 is installed on the auxiliary bending bracket 200, and the bending specimen 10 is placed in the center of the lower support column 112 and the upper support column 122 of the four-point bending fixture 100. After the tip of the micrometer used as the measuring instrument 410 touches the surface of the bending specimen 10, fix the micrometer. Then reset the micrometer. Lock the pressure switch of the manual hydraulic pump and start pressurizing. During the pressure loading process, always pay attention to the micrometer reading, and the pressure loading speed should not be too fast. When the micrometer reading is close to the calculated deflection of 9.8mm, slowly pressurize to avoid overloading.

[0039] After the stress is loaded to the calculated deflection, turn the 4 limit bolts on the upper end of the fixture, lock the fixture fastening bolts 170, unload the manual hydraulic pump, and remove the four-point bending fixture 100. Load 2 more specimens in the same way.

[0040] Place the four-point bending fixture 100 loaded with three specimens into a hydrochloric acid solution with a pH of 1.5, and use a pH automatic acid meter to ensure that the pH value of the solution is maintained at 1.5±0.1. No more liquid is added or replaced after 96 hours. Record the specimen status at 0h, 24h, 168h, and 200h. If all specimens break before 200h, the test ends when the last specimen breaks. The specimen is sensitive to hydrogen embrittlement, and the time of the last specimen breaking is recorded; if all specimens are not broken after 200h, the specimen is not sensitive to hydrogen embrittlement.

[0041] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0042] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A super large compressive stress non-blocking hydrogen-induced delayed cracking experimental device, characterized in that: include: A four-point bending fixture (100) is configured to clamp a bending specimen (10), comprising: a base (110), a pressure block (120), a bearing plate (130), a force transmission column (140), and a fixture fastening bolt (170), wherein the base (110) defines a cavity opening downward, the pressure block (120) is accommodated in the cavity and cooperates with the base (110) to clamp the bending specimen (10) in a four-point support manner, the force transmission column (140) passes through the base (110) and is supported between the pressure block (120) and the bearing plate (130), and the fixture fastening bolt (170) detachably locks the base (110) and the bearing plate (130); an auxiliary bending support (200), configured to support the four-point bending fixture (100); and The loading mechanism (300) is configured to apply stress to the bending specimen (10).

2. The device according to claim 1, characterized in that The base (110) is provided with a pair of first support points extending upwards towards the cavity; The pressing block (120) is provided with a pair of second supporting points extending downward on the lower surface, wherein the distance between the first supporting points is greater than the distance between the second supporting points; The bending specimen (10) is arranged between the first supporting point and the second supporting point to form a four-point support.

3. The device according to claim 1, characterized in that The force transmission column (140) is a finely polished column having a hollow columnar structure and having internal threads at both ends. The four-point bending fixture (100) further comprises: A first fixing bolt (150) is arranged to pass through the threaded connection between the bearing plate (130) and one end of the force transmission column (140) so as to fix the bearing plate (130) to the force transmission column (140); and A second fixing bolt (160) is arranged to pass through the threaded connection between the pressing block (120) and the other end of the force transmission column (140) so as to fix the pressing block (120) to the force transmission column (140).

4. The device according to claim 1, characterized in that The auxiliary bending bracket (200) comprises: A support base (210) comprising a bottom plate (211) and a U-shaped frame (212) extending vertically perpendicular to the bottom plate (211), wherein the U-shaped frame (212) is open at the top and defines a cross-shaped groove to accommodate the four-point bending fixture (100) and at least a portion of the loading mechanism (300); and A cover plate (220) is detachably fixedly connected to the top of the U-shaped frame (212) to close its opening, and a through hole is provided in the middle of the cover plate (220) to allow a portion of the loading mechanism (300) to pass through the cover plate (220) to apply stress to the bending specimen (10).

5. The device according to claim 4, characterized in that The auxiliary bending bracket (200) further comprises: The clamp positioning mechanism (230) comprises a positioning mechanism body (231) and a clamp positioning bolt (232), wherein the positioning mechanism body (231) is relatively fixed to the U-shaped frame (212), and the clamp positioning bolt (232) passes through the positioning mechanism body (231) and is connected to the four-point bending clamp (100).

6. The device according to claim 4, characterized in that The loading mechanism (300) comprises: A pressure mandrel (310) is arranged to pass through the cover plate (220) and abut against the bearing plate (130); A sleeve (320) is circumferentially sleeved on the outside of the pressure core shaft (310) and is fixedly connected to the cover plate (220); A pressure component is configured to apply pressure to the pressure core shaft (310) so as to move the pressure core shaft (310) downward relative to the sleeve (320).

7. The device according to claim 6, characterized in that The pressure component is a pressure rod (330), one end of which is pivotally connected to the top of the sleeve (320), and the middle of the pressure rod (330) abuts against the top of the pressure core shaft (310).

8. The device according to claim 6, characterized in that The pressure component is a hydraulic press, and the output end of the hydraulic press abuts against the top of the pressure core shaft (310).

9. The device according to claim 1, characterized in that The device further comprises a displacement measuring mechanism (400) configured to measure the amount of change in deflection of the bending specimen (10) during bending, the displacement measuring mechanism (400) comprising: a measuring instrument (410) disposed below the middle position of the bending specimen (10) to measure the displacement of the middle position of the bending specimen (10) in the vertical direction; and A measuring frame (420) supports the measuring instrument (410).

10. The method for testing the delayed hydrogen-induced cracking under ultra-large compressive stress without blocking is characterized by: The experiment was carried out using the device described in any one of claims 1 to 9, and the method comprises the following steps: S101, clamping a bending specimen (10) between a base (110) and a pressing block (120) of a four-point bending fixture (100); S102, placing the assembled four-point bending fixture (100) into the auxiliary bending bracket (200), and completing the assembly of the loading mechanism (300) and the auxiliary bending bracket (200); S103, starting the loading mechanism (300) to apply stress to the bending specimen (10), and after the bending specimen (10) is bent to a predetermined state, using a fixture fastening bolt (170) to lock the base (110) and the bearing plate (130) of the four-point bending fixture (100); S104, taking the four-point bending fixture (100) out of the auxiliary bending bracket (200), placing it in a hydrogen embrittlement test solution, and recording the cracking condition of the sample.

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