Universal testing machine for testing engineering materials

Abstract

The invention is suitable for the technical field of detection equipment, and provides a universal testing machine for testing engineering materials. Comprising a base; the mounting table is mounted on the base; the lifting mechanism is arranged between the mounting table and the base; the lifting platform is mounted at the output end of the lifting mechanism; the first clamping sleeve is mounted on the lifting table; wherein the first clamping sleeve comprises a shell, a circular opening is formed in the bottom of the shell, a clamping component is arranged in the shell, and the clamping component comprises two moving plates and a driving mechanism for driving the two moving plates to get close to each other or get away from each other; each moving plate is provided with a center clamping block, the two center clamping blocks are oppositely arranged and are elastically and slidably arranged on the moving plates in the moving linear direction of the moving plates, and the two sides of each moving plate are each provided with a first clamping block; the second clamping sleeve is arranged under the first clamping sleeve and is the same as the first clamping sleeve in structure, and the second clamping sleeve is fixedly installed on the base.

Description

Technical Field

[0001] The invention relates to the technical field of detection equipment, in particular to a universal testing machine for testing engineering materials. Background Art

[0002] In a broad sense, a testing machine is an instrument that verifies the quality or performance of a product or material according to design requirements before it is put into use. Testing machines are mainly used to measure the physical properties of materials or products, such as the yield strength, tensile strength, and impact toughness of steel.

[0003] Existing engineering material tensile testing equipment usually clamps the two ends of the bar on the adjacent side clamps during the tensile test. However, the existing technology requires the use of clamps of different specifications for bars of different diameters to ensure the clamping effect. Therefore, it is often necessary to replace the clamps during operation, which is troublesome. In order to solve this technical problem, a universal testing machine for engineering material testing is now provided. Summary of the invention

[0004] The object of the present invention is to provide a universal testing machine for testing engineering materials to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A universal testing machine for testing engineering materials, comprising: a base;

[0007] a mounting table mounted on the base;

[0008] A lifting mechanism disposed between the mounting platform and the base;

[0009] A lifting platform installed at the output end of the lifting mechanism;

[0010] A first clamping sleeve installed on the lifting platform; wherein the first clamping sleeve includes a shell, a circular opening is provided at the bottom of the shell, a clamping component is provided inside the shell, and the clamping component includes two movable plates and a driving mechanism for driving the two movable plates to move closer to or away from each other; a central clamping block is installed on each movable plate, the two central clamping blocks are arranged opposite to each other, the two central clamping blocks are elastically slidably installed on the movable plate along the linear direction of movement of the movable plate, a first clamping block is provided on both sides of the movable plate, the first clamping block is fixedly installed on one end of the mounting bent rod, a third gear is fixedly installed on the end of the mounting bent rod away from the first clamping block, a mounting shaft is fixedly installed at the center position of the third gear, the mounting shaft is elastically rotatably installed on the shell, and the mounting shaft is meshed with a rack at an adjacent position on the outer side of the central clamping block;

[0011] and a second clamping sleeve which is arranged directly below the first clamping sleeve and has the same structure as the first clamping sleeve, and the second clamping sleeve is fixedly mounted on the base.

[0012] As a further solution of the present invention: the driving mechanism includes two lead screws and a rotating assembly that drives the two lead screws to rotate, threaded holes are set at both ends of the movable plate, the lead screw is set through the threaded holes at the same end of the two movable plates, and two sections of threads with opposite rotation directions are set on the lead screw, and the two ends of the lead screw are respectively rotatably installed in the mounting circular holes on the adjacent mounting plates inside the shell.

[0013] As a further solution of the present invention: the rotating assembly includes a rotating motor fixedly mounted on the housing, the output end of the rotating motor is transmission-connected to a second gear, both sides of the second gear are meshed with a first gear, and the first gear is fixedly sleeved on an adjacent lead screw.

[0014] As a further solution of the present invention: a mounting sleeve is fixedly mounted on the side of the central clamping block away from the rod material, two racks are fixedly mounted on both sides of the mounting sleeve, and the mounting sleeve is elastically slidably mounted on the mounting column of the movable plate.

[0015] As a further solution of the present invention: a first elastic member is arranged inside the mounting sleeve, and two ends of the first elastic member are fixedly mounted on the mounting sleeve and the mounting column respectively.

[0016] As a further solution of the present invention: the first clamping sleeve is installed at the output end of the load limiting component, and the load limiting component is fixedly installed on the lifting platform.

[0017] As a further solution of the present invention: the load limiting component includes a cylinder body, a piston is elastically slidably arranged inside the cylinder body, and the piston divides the inner part of the cylinder body into an upper chamber and a lower chamber. A connecting rod is fixedly installed at the bottom of the piston, and the connecting rod passes through the through-hole housing at the bottom of the cylinder body and is fixedly installed on the connecting rod. An unloading valve is installed on the cylinder body, and a buffer sleeve is provided on the outer side of the cylinder body. The inside of the buffer sleeve is connected to the lower chamber of the cylinder body located below the piston through a one-way valve. The flow direction of the one-way valve is from the buffer sleeve to the inside of the lower chamber of the cylinder body. The cylinder body is filled with hydraulic medium during descent, and there is also some hydraulic medium inside the buffer sleeve.

[0018] As a further solution of the present invention: a valve core is arranged inside the unloading valve, and the valve core is connected to the connecting rod through an elastic telescopic rod. The connecting rod passes through the lower end of the unloading valve and is connected to the matching column. The lower end of the connecting rod abuts against the limiting step inside the unloading valve. In this way, in the initial stage, the connecting rod is maintained at the lower end under the action of the elastic telescopic rod.

[0019] As a further solution of the present invention: a connecting structure is provided between the mounting shaft and the matching column, and the connecting structure is used to adjust the height of the connecting rod according to the rotation angle of the mounting shaft.

[0020] As a further solution of the present invention: the connecting structure includes a rotating sleeve rotatably installed at the lower end of the unloading valve and a first sliding key fixedly installed on both sides of the mounting shaft, the first sliding key is slidably arranged in a guide groove on the side walls of the rotating sleeve, and the guide groove is located on the lower side of the rotating sleeve; a second sliding key is arranged on both side walls on the upper side of the rotating sleeve, and the second sliding key is slidably installed in an inclined sliding groove on the outer side wall of the adjacent matching column.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: the two ends of the bar material that needs to be stretched and measured are respectively inserted into the first clamping sleeve and the second clamping sleeve, and the outer side of the bar material contacts the four first clamping blocks. The four first clamping blocks are distributed on the outer side of the bar material. When the two movable plates are close to each other, the first clamping blocks on both sides move outward at the same time. The first clamping block drives the central clamping block to move toward the outer side of the bar material by installing a bending rod. When the central clamping block contacts the outer side of the bar material, the bar material is clamped. In this way, bars of different diameters can be clamped to ensure the stability of the clamping. The problem of the prior art that the clamp needs to be replaced when performing a tensile strength test on bars of different diameters during the test is solved. By setting the first clamping block and the central clamping block, multiple positions on the outer side of the bar material can be clamped, so that it is more convenient to clamp bars of different specifications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a schematic structural diagram of a universal testing machine for testing engineering materials according to an embodiment of the present invention.

[0023] Figure 2 The present invention is a schematic structural diagram of a first clamping sleeve in a universal testing machine for testing engineering materials according to an embodiment of the present invention.

[0024] Figure 3 for Figure 2 Enlarged view of point A in the middle.

[0025] Figure 4 The present invention is a schematic structural diagram of a central clamping block in a universal testing machine for testing engineering materials according to an embodiment of the present invention.

[0026] Figure 5 The present invention is a schematic structural diagram of a load-limiting component in a universal testing machine for testing engineering materials according to an embodiment of the present invention.

[0027] Figure 6 for Figure 5 Enlarged view of point B in the middle.

[0028] Figure 7 The present invention is a schematic structural diagram of a matching column in a universal testing machine for testing engineering materials according to an embodiment of the present invention.

[0029] Figure 8The present invention is a schematic structural diagram of a rotating sleeve in a universal testing machine for testing engineering materials according to an embodiment of the present invention.

[0030] In the figure:

[0031] 100-base, 200-mounting table, 300-lifting mechanism, 400-load limiting component, 500-first clamping sleeve, 600-second clamping sleeve, 700-lifting platform, 800-rod, 401-cylinder, 402-buffer sleeve, 403-piston, 404-connecting rod, 405-second elastic member, 406-check valve, 407-unloading valve, 408-connecting rod, 409-valve core, 410-elastic telescopic rod, 411-matching column, 412-rotating sleeve, 413-inclined slide groove, 414-second slide key, 415-guide groove, 501-housing, 502-mounting plate, 503-moving plate, 504-screw, 505-first gear, 506-second gear, 507-rotating motor, 508-first clamping block, 509-mounting bent rod, 510-third gear, 511-mounting shaft, 512-center clamping block, 513-mounting sleeve, 514-first elastic member, 515-first slide key, 516-rack. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] See also Figures 1 to 8 , a structural diagram of a universal testing machine for testing engineering materials provided in Example 1 of the present invention, the universal testing machine for testing engineering materials comprising: a base 100, a mounting platform 200 mounted on the base 100, a lifting mechanism 300 is installed between the mounting platform 200 and the base 100, a lifting platform 700 is installed on the output end of the lifting mechanism 300, a first clamping sleeve 500 is installed on the lifting platform 700, a second clamping sleeve 600 with the same structure as the first clamping sleeve 500 is arranged directly below the first clamping sleeve 500, and the second clamping sleeve 600 is fixedly mounted on the base 100.

[0035] The first clamping sleeve 500 includes a shell 501, a circular opening is provided at the bottom of the shell 501, a clamping component is provided inside the shell 501, and the clamping component includes two movable plates 503 and a driving mechanism for driving the two movable plates 503 to move closer to or away from each other; a central clamping block 512 is installed on each movable plate 503, the two central clamping blocks 512 are arranged opposite to each other, and the two central clamping blocks 512 are elastically slidably installed on the movable plate 503 along the linear direction of movement of the movable plate 503, and a first clamping block 508 is provided on both sides of the movable plate 503, the first clamping block 508 is fixedly installed on one end of the mounting bent rod 509, and a third gear 510 is fixedly installed on the end of the mounting bent rod 509 away from the first clamping block 508, and a mounting shaft 511 is fixedly installed at the center position of the third gear 510, and the mounting shaft 511 is elastically rotatably installed on the shell 501, and the mounting shaft 511 is meshed with a rack 516 at an adjacent position on the outer side of the central clamping block 512.

[0036] It should be noted that the first clamping block 508 and the central clamping block 512 are vertical in order to increase the contact area and ensure the clamping effect.

[0037] When in use, the two ends of the bar 800 that needs to be stretched and measured are respectively inserted into the first clamping sleeve 500 and the second clamping sleeve 600, and the outer side of the bar 800 contacts the four first clamping blocks 508, which are distributed on the outer side of the bar 800. When the two movable plates 503 are close to each other, the first clamping blocks 508 on both sides move outward at the same time, and the first clamping block 508 drives the central clamping block 512 to move outward of the bar 800 by installing the bending rod 509. When the central clamping block 512 contacts the outer side of the bar 800, the bar 800 is clamped, so that bars 800 of different diameters can be clamped to ensure the stability of the clamping. The problem of the prior art that the clamp needs to be replaced when performing a tensile strength test on bars 800 of different diameters during the test is solved. By providing the first clamping block 508 and the central clamping block 512 , multiple positions on the outside of the bar 800 can be clamped, so that it is more convenient to clamp the bars 800 of different specifications.

[0038] like Figure 2 , Figure 3 and Figure 4As shown, in some embodiments, in order to drive the two moving plates 503 to move closer to or farther from each other, the driving mechanism includes two lead screws 504 and a rotating assembly for driving the two lead screws 504 to rotate. Both ends of the moving plates 503 are provided with threaded holes. The lead screws 504 are arranged through the threaded holes at the same end of the two moving plates 503, and the lead screws 504 are provided with two sections of threads with opposite rotation directions. The two ends of the lead screws 504 are respectively rotatably mounted in the mounting circular holes on the adjacent mounting plates 502 inside the housing 501. In this way, when the rotating assembly rotates, the two lead screws 504 rotate simultaneously, and when the bar stock 800 needs to be clamped, the two moving plates 503 move closer to each other, and when the bar stock 800 needs to be released from clamping, the two moving plates 503 move away from each other. The two sections of threads with opposite rotation directions are respectively matched with a threaded hole.

[0039] like Figure 2 As shown, in some embodiments of the present invention, the rotating assembly includes a rotating motor 507 fixedly mounted on the housing 501, the output end of the rotating motor 507 is transmission-connected with a second gear 506, both sides of the second gear 506 are meshed with a first gear 505, and the first gear 505 is fixedly sleeved on the adjacent lead screw 504. In this way, when the rotating motor 507 is powered on and rotated, the second gear 506 can be driven to rotate, and the synchronous second gear 506 can drive the first gears 505 on both sides to rotate synchronously.

[0040] like Figure 3 and Figure 4 As shown, in some embodiments of the present invention, a mounting sleeve 513 is fixedly mounted on the side of the central clamping block 512 away from the bar 800, two racks 516 are fixedly mounted on both sides of the mounting sleeve 513, and the mounting sleeve 513 is elastically slidably mounted on the mounting column on the moving plate 503. In this way, the central clamping block 512 is elastically slidably mounted left and right in the housing 501.

[0041] like Figure 2 and Figure 3 As shown, in some embodiments of the present invention, a first elastic member 514 is provided inside the mounting sleeve 513, and the two ends of the first elastic member 514 are fixedly mounted on the mounting sleeve 513 and the mounting column, respectively. In this way, the central clamping block 512 is elastically slidably mounted. The first elastic member 514 is provided to facilitate the central clamping block 512 to return to its initial state. The first elastic member 514 is a coil spring.

[0042] like Figure 1 and Figure 5 As shown, in some embodiments of the present invention, the first clamping sleeve 500 is installed at the output end of the load limiting component 400, and the load limiting component 400 is fixedly installed on the lifting platform 700. By setting the load limiting component 400, the tensile strength measurement can be accurately achieved.

[0043] like Figures 5 to 8 As shown, in some embodiments of the present invention, the load limiting component 400 includes a cylinder body 401, and a piston 403 is elastically slidably arranged inside the cylinder body 401, and the piston 403 divides the inside of the cylinder body 401 into an upper chamber and a lower chamber. A connecting rod 404 is fixedly installed at the bottom of the piston 403, and the connecting rod 404 passes through the through-hole housing 501 at the bottom of the cylinder body 401 and is fixedly installed on the connecting rod 404. An unloading valve 407 is installed on the cylinder body 401, and a buffer sleeve 402 is sleeved on the outer side of the cylinder body 401. The inside of the buffer sleeve 402 is connected to the lower chamber inside the cylinder body 401 located below the piston 403 through a one-way valve 406. The flow direction of the one-way valve 406 is from the buffer sleeve 402 to the inside of the lower chamber of the cylinder body 401. The lower chamber of the cylinder body 401 is filled with hydraulic medium, and there is also some hydraulic medium inside the buffer sleeve 402. During the stretching process, when the stretching measurement limit of the bar 800 is reached, the unloading valve 407 will release the pressure to transport the medium in the lower chamber to the buffer sleeve 402, so as to protect the bar 800.

[0044] Specifically, a second elastic member 405 is further provided inside the cylinder 401, one end of the second elastic member 405 is fixedly mounted on the piston 403, and the other end of the second elastic member 405 is fixedly mounted on the top wall inside the cylinder 401. In this way, the piston 403 is elastically slidably mounted in the cylinder 401.

[0045] like Figures 5 to 8 As shown, in some embodiments of the present invention, the rotating angles of the mounting shaft 511 are different for different diameters of the bar 800, so a mounting shaft 511 on the housing 501 can be connected to the valve core of the unloading valve 407, so that the pressure relief pressure of the unloading valve 407 can be automatically adjusted according to the diameter of the bar 800. A valve core 409 is arranged inside the unloading valve 407, and the valve core 409 is connected to the connecting rod 408 through an elastic telescopic rod 410. The connecting rod 408 passes through the lower end of the unloading valve 407 and is connected to the matching column 411. The lower end of the connecting rod 408 abuts against the limiting step inside the unloading valve 407, so that the connecting rod 408 is maintained at the lowest end under the action of the elastic telescopic rod 410 in the initial stage. When the tensile pressure on the rod 800 reaches the set pressure, the valve core 409 overcomes the elastic force of the elastic telescopic rod 410, the valve core 409 moves downward, and the unloading valve 407 connects the lower chamber of the cylinder body 401 with the inside of the buffer sleeve 402, unloading the pressure in the lower chamber of the cylinder body 401 into the buffer sleeve 402.

[0046] In some embodiments of the present invention, a connecting structure is provided between the mounting shaft 511 and the matching column 411, and the connecting structure is used to adjust the height of the connecting rod 408 according to the rotation angle of the mounting shaft 511, so that the connecting rod 408 can adjust the opening pressure of the valve core 409 in height.

[0047] In some embodiments of the present invention, the input end of the unloading valve 407 is installed on the connecting hole at the bottom of the cylinder body 401 , and the output end of the unloading valve 407 is connected to the inside of the buffer sleeve 402 .

[0048] like Figures 5 to 8 As shown, as some embodiments of the present invention, the connection structure includes a rotating sleeve 412 rotatably installed at the lower end of the unloading valve 407 and a first sliding key 515 fixedly installed on both sides of the mounting shaft 511, the first sliding key 515 is slidably arranged in the guide groove 415 on the side walls on both sides of the rotating sleeve 412, and the guide groove 415 is located on the lower side of the rotating sleeve 412; a second sliding key 414 is arranged on both sides of the upper side of the rotating sleeve 412, and the second sliding key 414 is slidably installed in the inclined sliding groove 413 on the outer side wall of the adjacent matching column 411, the rotation angle of the mounting shaft 511 is determined according to the diameter of the bar 800, and the mounting shaft During the rotation of 511, the rotating sleeve 412 is driven to rotate, and the second sliding key 414 on the rotating sleeve 412 also rotates. Under the action of the second sliding key 414, the height of the matching column 411 changes, and the rising height of the matching column 411 is proportional to the rotation angle of the mounting shaft 511, so that the unloading limit can be increased automatically according to the diameter of the bar 800; the matching column 411 is fixedly installed on the connecting rod 408, and the connecting rod 408 can only move upward. Due to the existence of the elastic telescopic rod 410, it cannot rotate along the center line. Therefore, when the second sliding key 414 rotates around the center line of the connecting rod 408, the connecting rod 408 and the matching column 411 will not rotate. The elastic telescopic rod 410 is a prior art, so it is not described in detail here.

[0049] In some embodiments of the present invention, the rotating sleeve 412 is arranged concentrically with the matching column 411, and the rotating sleeve 412 is rotatably sleeved on the circular step outside the unloading valve 407. The rotating sleeve 412 can be installed by a bearing.

[0050] The working principle of the present invention is:

[0051] The two ends of the bar 800 that needs to be stretched and measured are respectively inserted into the first clamping sleeve 500 and the second clamping sleeve 600, and the outer side of the bar 800 contacts the four first clamping blocks 508. The four first clamping blocks 508 are distributed on the outer side of the bar 800. When the two movable plates 503 are close to each other, the first clamping blocks 508 on both sides move outward at the same time. The first clamping block 508 drives the central clamping block 512 to move toward the outer side of the bar 800 by installing the bending rod 509. When the central clamping block 512 contacts the outer side of the bar 800, the bar 800 is clamped. In this way, bars 800 of different diameters can be clamped to ensure the stability of the clamping. During the clamping process, the rotating shaft 511 is installed to rotate to drive the rotating sleeve 412 to rotate. The second sliding key 414 on the movable sleeve 412 also rotates, and under the action of the second sliding key 414, the height of the matching column 411 changes, and the rising height of the matching column 411 is proportional to the rotation angle of the mounting shaft 511, so that the unloading limit can be automatically increased according to the increase in the diameter of the rod 800, and then the load limiting component 400 is driven by the lifting mechanism 300 to move the load limiting component 400 upward to perform a tensile test on the rod 800. When the tensile measurement limit of the rod 800 is reached, the unloading valve 407 will release pressure and transport the medium in the lower chamber to the buffer sleeve 402, so that the rod 800 can be protected. After the tensile test is completed, under the action of the second elastic member 405, the piston 403 automatically returns to its initial position for a second tensile test.

[0052] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0053] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0054] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0056] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0057] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A universal testing machine for testing engineering materials, characterized in that: include: Base; a mounting table mounted on the base; A lifting mechanism disposed between the mounting platform and the base; a lifting platform installed at the output end of the lifting mechanism; A first clamping sleeve mounted on the lifting platform; Wherein, the first clamping sleeve comprises a shell, a circular opening is provided at the bottom of the shell, a clamping component is provided inside the shell, and the clamping component comprises two movable plates and a driving mechanism for driving the two movable plates to approach or move away from each other; a central clamping block is installed on each movable plate, the two central clamping blocks are arranged opposite to each other, and the two central clamping blocks are elastically slidably installed on the movable plate along the linear direction of movement of the movable plate, and a first clamping block is provided on both sides of the movable plate, the first clamping block is fixedly installed on one end of the mounting bent rod, a third gear is fixedly installed on the end of the mounting bent rod away from the first clamping block, a mounting shaft is fixedly installed at the center position of the third gear, the mounting shaft is elastically rotatably installed on the shell, and the mounting shaft is meshed with a rack at an adjacent position on the outer side of the central clamping block; and a second clamping sleeve which is arranged directly below the first clamping sleeve and has the same structure as the first clamping sleeve, wherein the second clamping sleeve is fixedly mounted on the base.

2. A universal testing machine for testing engineering materials according to claim 1, characterized in that: The driving mechanism includes two lead screws and a rotating assembly that drives the two lead screws to rotate. Threaded holes are provided at both ends of the movable plate. The lead screw is arranged to pass through the threaded holes at the same end of the two movable plates, and two sections of threads with opposite rotation directions are provided on the lead screw. The two ends of the lead screw are respectively rotatably installed in the mounting circular holes on the adjacent mounting plates inside the shell.

3. A universal testing machine for engineering material testing according to claim 2, characterized in that: The rotating assembly comprises a rotating motor fixedly mounted on the housing, the output end of the rotating motor is transmission-connected with a second gear, both sides of the second gear are meshed with a first gear, and the first gear is fixedly sleeved on an adjacent lead screw.

4. A universal testing machine for testing engineering materials according to claim 1, characterized in that: A mounting sleeve is fixedly mounted on one side of the central clamping block away from the bar material, two racks are fixedly mounted on two sides of the mounting sleeve, and the mounting sleeve is elastically slidably mounted on the mounting column of the movable plate.

5. A universal testing machine for testing engineering materials according to claim 4, characterized in that: A first elastic member is arranged inside the installation sleeve, and two ends of the first elastic member are fixedly mounted on the installation sleeve and the installation column respectively.

6. A universal testing machine for testing engineering materials according to claim 1, characterized in that: The first clamping sleeve is installed at the output end of the load limiting component, and the load limiting component is fixedly installed on the lifting platform.

7. A universal testing machine for testing engineering materials according to claim 6, characterized in that: The load limiting component includes a cylinder body, a piston is elastically and slidably arranged inside the cylinder body, and the piston divides the inner part of the cylinder body into an upper chamber and a lower chamber; a connecting rod is fixedly installed at the bottom of the piston, and the connecting rod passes through a through-hole shell at the bottom of the cylinder body and is fixedly installed on the connecting rod; an unloading valve is installed on the cylinder body, and a buffer sleeve is provided on the outer side of the cylinder body. The inside of the buffer sleeve is connected with the lower chamber inside the cylinder body located below the piston through a one-way valve. The flow direction of the one-way valve is from the buffer sleeve to the lower chamber of the cylinder body. The lower chamber of the cylinder body is filled with hydraulic medium, and there is also some hydraulic medium inside the buffer sleeve.

8. A universal testing machine for testing engineering materials according to claim 7, characterized in that: A valve core is arranged inside the unloading valve, and the valve core is connected to a connecting rod through an elastic telescopic rod. The connecting rod passes through the lower end of the unloading valve and is connected to a matching column. The lower end of the connecting rod abuts against a limiting step inside the unloading valve. In this way, the connecting rod is maintained at the lowest end under the action of the elastic telescopic rod in the initial stage.

9. A universal testing machine for testing engineering materials according to claim 8, characterized in that: A connecting structure is provided between the installation shaft and the matching column, and the connecting structure is used to adjust the height of the connecting rod according to the rotation angle of the installation shaft.

10. A universal testing machine for testing engineering materials according to claim 9, characterized in that: The connecting structure includes a rotating sleeve rotatably installed at the lower end of the unloading valve and a first sliding key fixedly installed on both sides of the mounting shaft. The first sliding key is slidably arranged in a guide groove on the side walls of the rotating sleeve on both sides, and the guide groove is located on the lower side of the rotating sleeve; a second sliding key is arranged on both side walls on the upper side of the rotating sleeve, and the second sliding key is slidably installed in an inclined sliding groove on the outer side wall of the adjacent matching column.

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