A plastic tensile testing device

Abstract

The application relates to the technical field of material mechanical property detection equipment, and discloses a plastic tensile testing device which comprises an upper clamp assembly and a lower clamp assembly, the upper clamp assembly and the lower clamp assembly both comprise a clamp base body, the clamp base body is provided with a through inner cavity, the opening size of the front cavity opening of the clamp base body is larger than that of the rear cavity opening, a guide groove is formed in the back outer wall of the clamp base body and communicates with the inner cavity, and a guide column is slidably connected in the guide groove. The application is provided with a sample centering limiting assembly A and a sample centering limiting assembly B, the sample centering limiting assembly B is connected with a sliding block through the guide column to establish a linkage relationship, is directly driven by a clamping mechanism to realize opening and closing movement, and does not need an additional independent driving source; the two sets of assemblies form a front-rear cooperative constraint link along the sample axial direction, respectively constrain the front section and the tail of the sample, can limit swing deflection in the sample clamping process, and reduce additional bending moments caused by eccentric loading.

Description

Technical Field

[0001] This invention relates to the field of equipment for testing the mechanical properties of materials, specifically a plastic tensile testing device. Background Technology

[0002] Tensile property testing of plastic materials is a routine test item in the physical and chemical testing of materials. It involves applying axial tensile force to a plastic sample to determine its key mechanical properties such as tensile strength and elongation at break. During the test, the alignment of the sample clamping directly affects the accuracy of the test data. If the sample is laterally offset or the clamping sides move asynchronously, additional lateral stress will be introduced, resulting in large dispersion of test results and data distortion. In severe cases, it may even lead to premature and abnormal fracture of the sample.

[0003] The lateral limiting structure of existing conventional tensile clamps is mostly a fixed rigid stop, which can only achieve simple blocking at the extreme position and cannot correct the slight deviation of the specimen. The limiting method is also limited. At the same time, the sliding guide structure of existing clamps generally has assembly gaps, which makes the clamping parts of the clamp prone to wobble and shaking during opening and closing movements and under force, further aggravating the problem of specimen clamping skew and deviation. Summary of the Invention

[0004] The purpose of this invention is to provide a plastic tensile testing device to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a plastic tensile testing device, comprising an upper clamp assembly and a lower clamp assembly, both the upper clamp assembly and the lower clamp assembly comprising a clamp base, the clamp base having a through inner cavity, the opening size of the front cavity of the clamp base being larger than the opening size of the rear cavity, and a guide groove communicating with the inner cavity being provided on the outer wall of the back side of the clamp base, and a guide post being slidably connected within the guide groove;

[0006] The front cavity of the fixture base is provided with a sample centering limiting component A, and the rear cavity of the fixture base is provided with a sample centering limiting component B.

[0007] The sample centering limiting component A includes a limiting seat, an inclined guide rod, and a pair of cantilevered elastic thin fins A. The limiting seat is fixedly installed on the front of the inner cavity of the fixture base, and the limiting seat has a wedge guide groove. The inclined guide rod passes through the wedge guide groove to form a positioning constraint. The lateral stop is slidably sleeved on the outside of the inclined guide rod. The mating inclined surface of the lateral stop and the main driving inclined surface of the wedge guide groove form a wedge pair sliding contact structure. Relying on the wedge action of the inclined surface, the axial displacement of the lateral stop along the inclined guide rod is converted into a horizontal centering clamping displacement and a self-increasing force effect.

[0008] Preferably, the inclined wedge guide groove has a limiting groove in its groove wall, and a limiting guide rod is built into the limiting groove. The two ends of the limiting guide rod are respectively connected to a sliding block and a lateral stop.

[0009] The cantilevered elastic thin fin is fixedly installed on the side of the lateral block near the gap using a cantilever constraint method with root connection and head suspension, forming an elastic floating limit structure.

[0010] The sample centering and limiting component B includes a movable groove opened on the side wall of the rear cavity of the fixture base and a pair of cantilevered elastic thin fins B. A movable block is slidably connected inside the movable groove, and the movable groove forms a sliding guide constraint on the movable block. The movable block transmits force through the connecting arm and the guide post. A pin clamp is fixedly connected to the bottom of the movable block.

[0011] Preferably, the upper clamp assembly and the lower clamp assembly further include a pair of limiting blocks and a pair of sliding blocks for the electric telescopic rod; the sliding blocks are assembled in the inner cavity of the clamp base, the back of the sliding blocks are connected to the guide post, the outer side of the sliding blocks is provided with an inclined surface that matches the inner cavity wall of the clamp base, a sample clamping pressure block is provided on the opposite side of the sliding blocks, a pressure sensor is provided on the sample clamping pressure block, the top of the sliding blocks is fixedly connected to the limiting blocks by a fixing pin, an intermediate force transmission block is provided between the limiting blocks, the top of the intermediate force transmission block is fixedly connected to the telescopic end of the electric telescopic rod, and the electric telescopic rod is fixedly installed on the top of the inner cavity of the clamp base. The electric telescopic rod serves as the clamping power source, driving the intermediate force transmission block to feed downwards. The outer side of the sliding slider is provided with an inclined surface that is adapted to the inner cavity wall of the fixture base. Under the vertical downward pressure load of the intermediate force transmission block, the inclined surface cooperates with the inner cavity wall to decompose the vertical downward driving force applied by the intermediate force transmission block into a horizontal clamping component force, which drives the two sliding sliders on both sides to close towards each other, so that the sample clamping pressure block clamps the sample.

[0012] Preferably, a movable gap is provided between the intermediate force transmission block and the limiting block, so that the intermediate force transmission block only presses down on the sliding slider during its downward movement and does not contact or interfere with the limiting block. This movable gap allows for an independent feed stroke of the intermediate force transmission block, ensuring that all the force from the intermediate force transmission block is applied downwards to the sliding slider, and the force is not transmitted to the limiting block. The limiting block only serves a connecting and positioning function and does not bear the downward pressure load of the wedge block; this avoids deformation of the limiting block under stress and prevents the limiting block from interfering with the downward feeding action of the intermediate force transmission block.

[0013] Preferably, the lateral blocks are uniformly provided with elastic soft limiting pads on their inner sidewalls. The elastic soft limiting pads on both sides fit together as the lateral blocks slide and close, achieving circumferential locking and positioning after the lateral blocks are closed and in place, eliminating lateral swaying gaps. During the pre-centering of the sample, the lateral blocks maintain a pre-reserved gap with the sample surface to avoid the initial lateral prestress generated by rigid preloading. After the elastic soft limiting pads engage, they restrict the lateral misalignment of the two lateral blocks, eliminate the fitting gap in the closed state, and maintain the coaxiality of the V-shaped guide slope. During the pre-centering stage, the lateral blocks do not directly contact the sample and will not apply lateral pressure during the sample loading stage, thus avoiding the initial prestress from changing the internal stress state of the sample.

[0014] Preferably, the cantilevered elastic thin fins A and B are provided with elongated weight-reducing grooves. By changing the moment of inertia of the fin cross section, the bending stiffness of the cantilever fin is adjusted to achieve a mechanical match between limiting and correcting deviation and elastic yielding.

[0015] Preferably, the limiting ends of the cantilevered elastic thin fins A and B on both sides form an integral V-shaped guide slope structure through the alignment and engagement of the fitting protrusions and fitting grooves. When the sample experiences lateral displacement, the wedge force principle of the V-shaped slope is used to convert the lateral displacement disturbance of the sample into an axial return force pointing towards the center of the fixture, achieving passive correction and limiting without power. The fitting protrusions and fitting grooves are aligned and engaged, aligning the ends of the two thin fins to form a continuous and complete V-shaped guide slope, avoiding misalignment of the ends of the two fins and the resulting positioning steps. When the sample is fed in, if there is any lateral displacement, the outer wall of the sample contacts the slope, and the slope decomposes the lateral displacement load into a centripetal force, automatically pushing the sample back to the central axis without the need for additional power. When the sample is stretched and experiences a slight lateral swing, the cantilevered fins can elastically bend and retract, without locking the sample.

[0016] Preferably, the cantilevered elastic thin fin B is disposed between the two needle clamps. The cantilevered elastic thin fin B is fixed to the needle clamps using a cantilever constraint method with the root connected and the head suspended, forming an elastic floating limiting structure. The sample centering limiting component A and the sample centering limiting component B form a front-to-back cooperative constraint link along the sample axis. The sample passes through the needle clamp of component B and the cantilevered elastic thin fin of component A in sequence along the axial direction, forming a dual-point centering constraint at the tail and front of the sample. The two-point positioning can limit the swing deflection of the sample, overcome the defect of single-point centering that the sample easily deflects around a single point, ensure that the sample axis coincides with the tensile loading axis of the whole machine, and eliminate the additional bending moment caused by eccentric tension.

[0017] Preferably, it also includes a frame, the frame having a drive mechanism inside, and a crossbeam that can slide vertically along the frame between the frames. The lower clamp assembly is fixedly connected to the lower part of the frame, and the upper clamp assembly is connected to a tension sensor via a connecting seat. The tension sensor is fixedly connected to the bottom of the crossbeam.

[0018] Preferably, a control base is provided at the bottom of the frame, and the control base is equipped with a touch screen and an adjustment knob. The control base is equipped with a measurement and control unit, which is electrically connected to the drive mechanism, the tension sensor, and the pressure sensor of the sample clamping block, respectively, for controlling the tensile action and collecting the tensile test data of the sample.

[0019] This invention provides a plastic tensile testing device, which has the following advantages:

[0020] 1. The present invention sets up a sample centering limiting component A and a sample centering limiting component B. The sample centering limiting component B establishes a linkage relationship with the sliding slider through the guide column, and is directly driven by the clamping mechanism to realize the opening and closing movement without the need for an additional independent driving source. The two sets of components form a front and rear cooperative constraint link along the sample axis, respectively constraining the front and rear of the sample, which can limit the swing deflection during the sample clamping process and reduce the additional bending moment caused by eccentric loading.

[0021] 2. The centering and limiting component A of the present invention adopts a wedge pair structure composed of a lateral stop and a wedge guide groove. When the lateral stop slides obliquely, it relies on the geometric transmission relationship of the wedge pair to convert the oblique feed displacement into a horizontal centering displacement, generating a wedge self-amplifying force. After the lateral stop is closed in place, the elastic soft limiting pads on both sides fit together, which can constrain the lateral misalignment between the lateral stops and eliminate the shaking caused by the assembly gap.

[0022] 3. The cantilevered elastic thin fin of this invention adopts a cantilever constraint form with the root fixed and the head suspended. It relies on the V-shaped guide slope to convert the lateral displacement of the sample into a push force pointing towards the center, thereby achieving passive correction. The thin fin has a long strip-shaped weight reduction groove, and by changing the moment of inertia of the cross section, it can adjust its own bending stiffness, which can simultaneously meet the requirements of sample correction and elastic yielding during the stretching stage. During the stretching process, the thin fin can undergo elastic bending, releasing the lateral hard constraint on the sample and avoiding the continuous application of lateral additional force to the sample.

[0023] 4. This invention isolates the downward pressure load by setting an movable gap between the intermediate force transmission block and the limiting block, so that the downward pressure load of the intermediate force transmission block only acts on the sliding block, and the limiting block does not bear the downward impact load, reducing the possibility of the limiting block being deformed by pressure and ensuring that the motion reference of the sliding block does not shift; by cooperating with the outer inclined surface of the sliding block and the inner cavity wall of the fixture base, the vertical downward pressure load output by the intermediate force transmission block is decomposed into a horizontal clamping component force, thereby realizing sample clamping.

[0024] 5. The fixture base of the present invention adopts a through-cavity structure with a larger front and a smaller rear. The larger front cavity facilitates sample placement and provides assembly and movement space for the sample centering and limiting component A. The smaller rear cavity provides an installation reference for the sample centering and limiting component B, limits the components, and reduces axial movement of the components after assembly. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall three-dimensional structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the front sectional view of the clamping assembly of the present invention;

[0027] Figure 3 This is a three-dimensional schematic diagram of the back of the fixture base of the present invention;

[0028] Figure 4 This is a side sectional view of the clamp assembly of the present invention;

[0029] Figure 5 For the present invention Figure 1 Enlarged 3D schematic diagram of the structure at point A in the middle;

[0030] Figure 6 This is a top-section schematic diagram of the centering and limiting component A of the present invention;

[0031] Figure 7 This is a top-section schematic diagram of the centering and limiting component B of the present invention;

[0032] Figure 8 For the present invention Figure 6 Enlarged 3D schematic diagram of the structure at point B;

[0033] Figure 9 For the present invention Figure 7 Enlarged 3D schematic diagram of the structure at point C.

[0034] In the diagram: 1-Frame, 11-Control base, 12-Tension sensor, 21-Upper clamp assembly, 22-Lower clamp assembly, 23-Crossbeam, 31-Electric telescopic rod, 32-Intermediate force transmission block, 33-Limiting block, 34-Sliding slider, 35-Sample clamping pressure block, 36-Clamping base, 38-Guide groove, 39-Guide column, 41-Limiting seat, 42-Wedge guide groove, 43-Side stop block, 44-Inclined guide rod, 45-Limiting groove, 46-Cantilever elastic thin fin A, 47-Limiting guide rod, 432-Elastic soft limiting pad, 461-Matching protrusion, 462-Matching groove, 463-Long strip weight reduction groove, 51-Moving groove, 52-Moving block, 53-Connecting arm, 54-Injector foot clamp, 55-Cantilever elastic thin fin B. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example: Figures 1 to 9 As shown, a plastic tensile testing device includes a frame 1, an upper clamp assembly 21, and a lower clamp assembly 22. The frame 1 is equipped with a drive mechanism, and a crossbeam 23 that can slide vertically along the frame 1 is provided between the frames 1. The crossbeam 23 is connected to the drive mechanism. The drive mechanism adopts a lead screw assembly, which is the prior art and will not be described in detail. The lower clamp assembly 22 is fixedly connected to the lower part of the frame 1. The upper clamp assembly 21 is connected to a tension sensor 12 through a connecting seat. The tension sensor 12 is connected to the bottom of the crossbeam 23.

[0037] A control base 11 is set at the bottom of the frame 1. The control base 11 is equipped with a touch screen and an adjustment knob. The control base 11 is equipped with a measurement and control unit. The measurement and control unit is electrically connected to the drive mechanism, the tensile sensor 12, etc., and is used to control the tensile action and collect the tensile test data of the sample.

[0038] Both the upper clamp assembly 21 and the lower clamp assembly 22 include a clamp base 36, an electric telescopic rod 31, a pair of limiting blocks 33 and a pair of sliding blocks 34. The clamp base 36 has a through inner cavity. The opening size of the front cavity of the clamp base 36 is larger than the opening size of the rear cavity. A guide groove 38 communicating with the inner cavity is opened on the outer wall of the back side of the clamp base 36. A guide post 39 is slidably connected in the guide groove 38. A sample centering limiting component A is provided at the front cavity of the clamp base 36 and a sample centering limiting component B is provided at the rear cavity.

[0039] In this embodiment, the fixture base 36 is the main bearing shell of the fixture, with a through-cavity serving as the installation and accommodating space for the sample clamping and centering mechanism. The front cavity is larger, facilitating the insertion of the sample from the front, while the rear cavity is smaller, used to assemble the rear centering mechanism and provide a limiting constraint on the tail of the sample. The size difference between the front and rear cavities forms an installation step, providing installation space for the sample centering limiting component A and the sample centering limiting component B. The guide groove 38 is arranged along the back of the fixture base 36, and the guide post 39 is embedded inside the guide groove 38. The groove wall of the guide groove 38 restricts the movement direction of the guide post 39, allowing it to slide only along the groove direction. The guide post 39 acts as a power transmission component, transmitting external driving force to provide power input for the sample centering limiting component B.

[0040] like Figures 2 to 4As shown, the sliding slider 34 is assembled in the inner cavity of the fixture base 36. The back of the sliding slider 34 is fixedly connected to the guide post 39. The outer side of the sliding slider 34 is provided with an inclined surface that matches the inner cavity wall of the fixture base 36. A sample clamping block 35 is provided on the opposite side of the sliding slider 34. A pressure sensor is installed on the sample clamping block 35. The pressure sensor is connected to the measurement and control unit. The pressure sensor is used to detect the clamping force of the sample clamping block 35 on the plastic sample. The top of the sliding slider 34 is fixedly connected to the limiting block 33 by a fixing pin. An intermediate force transmission block 32 is provided between the limiting blocks 33. The top of the intermediate force transmission block 32 is fixedly connected to the telescopic end of the electric telescopic rod 31. The electric telescopic rod 31 is fixedly installed on the top of the inner cavity of the fixture base 36.

[0041] An movable gap is provided between the intermediate force transmission block 32 and the limiting block 33 to limit the downward pressing object of the intermediate force transmission block 32, so that when the intermediate force transmission block 32 moves downward, it only contacts the downward sliding slider 34, and the entire downward load is borne by the sliding slider 34, and the load is not transmitted to the limiting block 33; the limiting block 33 only serves as a positioning connection and does not bear the impact downward load of the intermediate force transmission block 32, so as to avoid the limiting block being deformed by pressure and its position shifting, and to prevent the limiting block 33 from interfering with the downward stroke of the intermediate force transmission block 32.

[0042] When the electric telescopic rod 31 drives the middle force transmission block 32 to rise and lift, it releases the downward pressure constraint on the sliding slider 34, and pulls the two sliding sliders 34 to slide outwards and open. On the one hand, it drives the sample clamping block 35 to release the sample, realizing automatic release and making it easy to take out the sample; on the other hand, it drives the guide column 39 to move in the opposite direction, driving the rear sample centering limit component B to open and reset synchronously.

[0043] The sample centering limiting component A cooperates with the sample clamping block 35 to pre-complete the lateral centering and positioning of the sample during the sample clamping and positioning stage, and can adaptively retract and release the lateral constraint during the tensile loading stage. The sample centering limiting component A includes a limiting seat 41, an inclined guide rod 44, and a pair of cantilevered elastic thin fins A46. The limiting seat 41 is fixedly installed on the front of the inner cavity of the fixture base 36, and a wedge guide groove 42 is provided on the limiting seat 41. The inclined guide rod 44 passes through the wedge guide groove 42 to form a positioning constraint. The lateral stop block 43 is slidably sleeved on the outside of the inclined guide rod 44. The mating inclined surface of the lateral stop block 43 and the main driving inclined surface of the wedge guide groove 42 form a wedge pair sliding contact structure. Relying on the wedge action of the inclined surface, the axial displacement of the lateral stop block 43 along the inclined guide rod 44 is converted into a horizontal centering and clamping displacement and forms a self-increasing force effect.

[0044] In this embodiment, as Figure 5 , 6As shown in Figure 8, the limiting seat 41 is the carrier of the wedge guide groove 42 and is fixed to the inner cavity of the front end of the fixture base 36 with bolts, serving as the installation reference for the entire A assembly. The wedge guide groove 42 is an inclined long groove structure, with the inclined guide rod 44 arranged along the inclined direction of the groove, providing oblique sliding guidance for the lateral stop 43. The lateral stop 43 can slide along the inclined guide rod 44, and the mating inclined surface of the lateral stop 43 is tightly fitted with the main driving inclined surface of the wedge guide groove 42 to form a wedge transmission pair. When the lateral stop 43 slides downward along the inclined direction, the wedge pair uses the geometric relationship of the inclined surface to convert the oblique feed displacement into a horizontal opposing displacement, and obtains self-amplifying force by relying on the wedge amplification effect, thereby improving the clamping force for centering and positioning.

[0045] The inclined wedge guide groove 42 has a limiting groove 45 in its groove wall, and a limiting guide rod 47 is built into the limiting groove 45. The two ends of the limiting guide rod 47 are connected to the sliding block 34 and the side stop 43, respectively. When the electric telescopic rod 31 drives the middle force transmission block 32 to rise, it releases the downward pressure load on the sliding block 34, pulls the two sliding blocks 34 away from each other, and the sample clamping pressure block 35 opens to release the sample. At the same time as the sliding block 34 opens, it drives the limiting guide rod 47 to slide in the opposite direction. The limiting guide rod 47 drives the side stop 43 to separate.

[0046] The lateral stop 43 is uniformly provided with elastic soft limiting pads 432 on its inner sidewall. The elastic soft limiting pads 432 on both sides fit together with the closing sliding movement of the lateral stop 43, realizing circumferential locking and positioning after the lateral stop 43 is closed in place, eliminating lateral shaking gaps. Under the condition of sample pre-centering, the lateral stop 43 maintains a reserved gap with the sample surface to avoid the initial lateral prestress generated by rigid pre-compression.

[0047] In this embodiment, as Figure 5 , 6 As shown in Figure 8, the elastic soft limiting pad 432 is installed on the inner wall of the side stop 43. When the left and right side stops 43 close to each other to the designated position, the elastic soft limiting pads 432 on both sides contact and compress, limiting the horizontal misalignment between the two side stops 43, eliminating the shaking caused by the assembly gap of the parts, and ensuring that the left and right side stops 43 are coaxial after closing. The elastic soft limiting pad 432 is made of soft elastic material, which will not cause problems such as rigid jamming or wear and scratches. In the pre-alignment state, the side stops 43 do not directly contact the sample, and a reserved gap is maintained. Correction is completed only by the front cantilever elastic thin fin A46. This avoids the side stops 43 directly squeezing the sample to generate initial lateral prestress, prevents additional stress from being generated inside the sample before formal tensioning, and ensures that the original mechanical properties of the material are not disturbed.

[0048] The cantilevered elastic thin fin A46 is fixedly installed on the side of the lateral stop 43 near the gap using a cantilever constraint method with root connection and head suspension, forming an elastic floating limit structure. The cantilevered elastic thin fin A46 has a long strip-shaped weight reduction groove 463. By changing the moment of inertia of the fin section, the bending stiffness of the cantilever fin is adjusted to achieve mechanical matching between limit correction and elastic yielding. The limit ends of the cantilevered elastic thin fins A46 on both sides form an integral V-shaped guide slope structure through the alignment and fitting of the fitting protrusion 461 and the fitting groove 462. When the sample deviates laterally, the wedge force principle of the V-shaped slope is used to convert the lateral deviation disturbance of the sample into an axial return force pointing towards the center of the fixture, realizing passive correction and limit without power.

[0049] In this embodiment, as Figure 8 As shown, the cantilevered elastic thin fin A46 is a cantilever beam structure, with its root connected to the lateral stop 43 and the other end unsupported and suspended. This constraint allows the head of the cantilevered elastic thin fin A46 to undergo elastic bending, providing adaptive elastic yielding capability. A long strip-shaped weight-reducing groove 463 is formed on the plate of the cantilevered elastic thin fin A46. The groove alters the cross-sectional profile of the fin, reducing the moment of inertia and thus adjusting the fin's bending stiffness. This allows for adaptation to the correction requirements of plastic samples with different hardness and thicknesses without changing the fin material, simply by adjusting the groove length and width. The interlocking protrusions 461 and interlocking grooves 462 at the ends of the two thin fins interlock, aligning the ends of the two cantilevered elastic thin fins and forming a continuous, smooth V-shaped guide slope, eliminating end steps. Once the sample deviates from the axis and contacts the V-shaped inclined plane during the sample feeding process, the inclined plane decomposes the lateral contact load into a component force pointing towards the central axis, automatically correcting the sample position without requiring additional power throughout the process; when the sample enters the tensile stage and produces a slight lateral sway, the cantilevered elastic thin fins can bend and yield elastically, without continuously applying lateral restraint force to the sample.

[0050] The sample centering limiting component B includes a movable groove 51 located on the side wall of the rear cavity of the fixture base 36. A movable block 52 is slidably connected inside the movable groove 51, and the movable groove 51 provides sliding guidance constraint for the movable block 52. The movable block 52 transmits force through the connecting arm 53 and the guide post 39. A needle clamp 54 is fixedly connected to the bottom of the movable block 52. A cantilevered elastic thin fin B55 is installed between the two needle clamps 54. The cantilevered elastic thin fin B55 is fixedly set in the needle clamp 54 using a cantilever constraint method with the root connected and the head suspended. Above, an elastic floating limiting structure is formed. The cantilever elastic thin fin B55 and the cantilever elastic thin fin A46 have the same structure. The sample centering limiting component A and the sample centering limiting component B form a front and rear cooperative constraint link along the sample axis. When the sample is loaded, the front cantilever elastic thin fin A46 uses the V-shaped guide slope to convert the lateral offset of the sample into a push force pointing towards the center to achieve passive correction. The rear pin clamp 54 slides along the moving groove 51 with the moving block 52. The cantilever elastic thin fin B55 simultaneously applies a centering constraint force to the rear end of the sample.

[0051] In this embodiment, as Figure 9 As shown, the moving groove 51 is directly formed on the side wall of the rear cavity of the fixture base, serving as the linear sliding track for the moving block 52. The groove wall restricts the movement direction of the moving block 52, ensuring that the moving block 52 only moves along the groove direction, preventing deflection and jamming. The moving block 52, connecting arm 53, and guide post 39 form a linkage structure. The sliding movement of the guide post 39 is transmitted to the moving block 52 through the connecting arm 53, causing the left and right moving blocks 52 to move synchronously towards or away from each other. The needle clamp 54 moves synchronously with the moving block 52, achieving centering of the sample tail. In terms of axial arrangement, the cantilevered elastic thin fin B55 is arranged in the middle section of the two sets of pin clamps of component B. The sample passes through the pin clamp 54 from back to front and then enters the V-shaped section enclosed by the cantilevered elastic thin fin B55, forming a dual-point constraint of rear-end centering and front-end coarse correction. The two-point positioning can constrain the swing and deflection of the sample, overcoming the defect of single-point positioning that the sample is prone to deflection around the fixed point and generate eccentric bending moment. During the sample loading stage, the two sets of mechanisms are synchronously centered. During the tensile loading stage, both sets of mechanisms can yield and release the lateral constraint to ensure that the sample only bears pure axial tensile force and eliminates the test error caused by eccentricity.

[0052] A plastic tensile testing device, in use, a plastic sample is fed into the inner cavity through the larger front cavity of the clamp base 36, the sample passes sequentially between the V-shaped guide slopes formed by a pair of cantilevered elastic thin fins A46 of the sample centering limiting component A, and then passes between the two sets of pin clamps 54 of the rear sample centering limiting component B.

[0053] When the electric telescopic rod 31 drives the intermediate force transmission block 32 to feed vertically downward, an movable gap is set between the intermediate force transmission block 32 and the limiting block 33. During the downward movement of the intermediate force transmission block 32, it only presses down the sliding slider 34, and the force is not transmitted to the limiting block 33. The outer inclined surface of the sliding slider 34 cooperates with the inner cavity wall of the clamp base 36 to convert the vertical downward driving force applied by the intermediate force transmission block 32 into a horizontal clamping component force, which drives the two sliding sliders 34 to close towards each other. When the pressure sensor detects that the pressure has reached the set value, the sample clamping block 35 completes the clamping and fixing of the sample.

[0054] As the sliding slider 34 closes towards each other, it drives the connected limiting guide rod 47 and guide post 39. On the one hand, the limiting guide rod 47 drives the side stop 43 to slide towards each other along the limiting groove 45. The side stop 43 slides obliquely along the wedge pair formed by the inclined guide rod 44 and the wedge guide groove 42, driving the elastic soft limiting pads 432 on both sides to fit together with the side stop 43 as they close and slide, thus achieving circumferential locking and positioning after the side stop 43 closes in place. On the other hand, the guide post 39 slides synchronously along the guide groove 38. The guide post 39 drives the moving block 52 to slide towards each other along the moving groove 51 via the connecting arm 53, driving the needle clamp 54 to retract synchronously and applying a centering constraint force to the tail of the sample.

[0055] If the sample has a lateral offset, the side wall of the sample touches the V-shaped guide slope formed by the cantilever elastic thin fins A46 and B55. Relying on the wedge force component effect of the slope, the lateral offset disturbance of the sample is converted into a centering force pointing towards the center of the fixture, thereby achieving passive correction of the front end of the sample.

[0056] When the specimen undergoes a slight lateral oscillation during the tensile process, the cantilevered elastic thin fins rely on their cantilever structure to elastically bend and yield. At the same time, the pin clamp 54 of the rear B component follows the sliding slider 34 and has follow-up space. The two sets of centering mechanisms release lateral constraints synchronously, which will not form a rigid lock on the specimen and avoid generating additional lateral loads that will interfere with the tensile test results. The long strip-shaped weight reduction groove 463 opened on the cantilevered elastic thin fins adjusts the bending stiffness of the fins by changing the moment of inertia of the cross section, taking into account both passive correction capability and elastic yield performance.

[0057] During the tensile loading stage, the internal drive mechanism of the frame 1 drives the crossbeam 23 to move vertically upward. The upper clamp assembly 21 moves upward synchronously with the crossbeam 23, while the lower clamp assembly 22 remains fixed. The upper and lower clamps generate relative displacement, applying axial tension to the clamped plastic sample. The measurement and control unit inside the control base 11 collects the load signals of the tension sensor 12 and the pressure sensor in real time, and synchronously collects the displacement signal of the crossbeam 23. The tensile test is completed according to the set tensile rate, and test data such as tensile strength and elongation at break are recorded until the sample breaks, at which point the drive mechanism stops running.

[0058] Upon completion of the sample unloading stage, the electric telescopic rod 31 lifts the intermediate force transmission block 32 upwards, releasing the downward pressure load on the sliding slider 34. This pulls the two sliding sliders 34 apart, causing the sample clamping block 35 to open and release the sample. Simultaneously, the opening of the sliding sliders 34 drives the limiting guide rod 47 and guide post 39 to slide in the opposite direction. The limiting guide rod 47 causes the lateral stop block 43 to separate, and the guide post 39, via the connecting arm 53, drives the moving block 52 and the needle clamp 54 to separate synchronously, releasing the sample from its position. At this point, the entire centering mechanism is fully reset, and the operator can remove the tested sample from the front cavity of the fixture, completing a full tensile test procedure.

[0059] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A plastic tensile testing device, comprising an upper clamp assembly (21) and a lower clamp assembly (22), characterized in that: Both the upper clamp assembly (21) and the lower clamp assembly (22) include a clamp base (36). The clamp base (36) has a through cavity. The opening size of the front cavity of the clamp base (36) is larger than the opening size of the rear cavity. A guide groove (38) communicating with the inner cavity is provided on the outer wall of the back side of the clamp base (36), and a guide post (39) is slidably connected in the guide groove (38). The front cavity of the fixture base (36) is provided with a sample centering limiting component A, and the rear cavity of the fixture base (36) is provided with a sample centering limiting component B. The sliding slider (34) is assembled in the inner cavity of the fixture base (36). The back of the sliding slider (34) is connected to the guide post (39). The outer side of the sliding slider (34) is provided with an inclined surface that matches the inner cavity wall of the fixture base (36). A sample clamping pressure block (35) is provided on the opposite side of the sliding slider (34). A pressure sensor is provided on the sample clamping pressure block (35). The top of the sliding slider (34) is fixedly connected to the limiting block (33) by a fixing pin. An intermediate force transmission block (32) is provided between the limiting blocks (33). The top of the intermediate force transmission block (32) is fixedly connected to the telescopic end of the electric telescopic rod (31). The electric telescopic rod (31) is fixedly installed on the top of the inner cavity of the fixture base (36).

2. The plastic tensile testing device according to claim 1, characterized in that: The intermediate force transmission block (32) and the limiting block (33) are provided with an movable gap, so that the intermediate force transmission block (32) only presses down the sliding block (34) during the downward movement and does not contact or interfere with the limiting block (33).

3. The plastic tensile testing device according to claim 2, characterized in that: The sample centering limiting component A includes a limiting seat (41), an inclined guide rod (44), and a pair of cantilevered elastic thin fins A (46). The limiting seat (41) is fixedly installed on the front of the inner cavity of the fixture base (36), and the limiting seat (41) has a wedge guide groove (42). The inclined guide rod (44) passes through the wedge guide groove (42) to form a positioning constraint. The lateral stop (43) is slidably sleeved on the outside of the inclined guide rod (44). The mating inclined surface of the lateral stop (43) and the main driving inclined surface of the wedge guide groove (42) form a wedge pair sliding contact structure.

4. The plastic tensile testing device according to claim 3, characterized in that: The inclined wedge guide groove (42) has a limiting groove (45) on its groove wall. The limiting groove (45) has a limiting guide rod (47) built in it. The two ends of the limiting guide rod (47) are connected to the sliding slider (34) and the side stop (43) respectively.

5. A plastic tensile testing device according to claim 3, characterized in that: The sample centering limiting component B includes a movable groove (51) opened on the side wall of the rear cavity of the fixture base (36) and a pair of cantilevered elastic thin fins B (55). A movable block (52) is slidably connected inside the movable groove (51). The movable groove (51) forms a sliding guide constraint on the movable block (52). The movable block (52) transmits force through the connecting arm (53) and the guide post (39). A needle foot clamp (54) is fixedly connected to the bottom of the movable block (52).

6. The plastic tensile testing device according to claim 5, characterized in that: The lateral stop (43) is uniformly provided with elastic soft limiting pads (432) on the inner sidewall. The elastic soft limiting pads (432) on both sides fit together with the lateral stop (43) during the closing sliding movement. The cantilever elastic thin fin A (46) and cantilever elastic thin fin B (55) are provided with long strip-shaped weight reduction grooves (463). The cantilever elastic thin fin A (46) is fixedly set on the side of the lateral stop (43) near the gap by a cantilever constraint method with root connection and head suspension, forming an elastic floating limiting structure.

7. A plastic tensile testing device according to claim 6, characterized in that: The limiting ends of the cantilevered elastic thin fins A (46) and B (55) on both sides form an integral V-shaped guide slope structure through the alignment and fitting of the fitting protrusion (461) and the fitting groove (462).

8. A plastic tensile testing device according to claim 5, characterized in that: The cantilevered elastic thin fin B (55) is disposed between two needle clamps (54). The cantilevered elastic thin fin B (55) is fixedly disposed on the needle clamp (54) by a cantilever constraint method with the root connected and the head suspended, forming an elastic floating limit structure.

9. A plastic tensile testing device according to claim 1, characterized in that: It also includes a frame (1), which is equipped with a drive mechanism inside and a crossbeam (23) that can slide vertically along the frame (1) between the frames (1). The lower clamp assembly (22) is fixedly connected to the lower part of the frame (1), and the upper clamp assembly (21) is connected to a tension sensor (12) through a connecting seat. The tension sensor (12) is fixedly connected to the bottom of the crossbeam (23).

10. A plastic tensile testing device according to claim 1, characterized in that: The frame (1) is provided with a control base (11) at the bottom. The control base (11) is provided with a touch screen and an adjustment knob. The control base (11) is provided with a measurement and control unit. The measurement and control unit is electrically connected to the pressure sensors of the drive mechanism, the tension sensor (12), and the sample clamping block (35).

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