59 results about "Compressive test" patented technology

The utility model belongs to the technical field of composite material structure test, and discloses an axial compression test fixture, which comprises a base, two side support pieces, a first clamping assembly and an anti-instability assembly, the two side support pieces are oppositely arranged on the base, a composite material is arranged between the two side support pieces, and the anti-instability assembly comprises two first anti-instability pieces and two second anti-instability pieces. Each first anti-instability piece comprises two separated first abutting parts, the distance between the two first abutting parts is larger than the damage range of the side face of the composite material, the two first anti-instability pieces are arranged on the two sides, in the second direction, of the composite material and close to the impacted side face of the composite material, and the second anti-instability pieces correspond to the first anti-instability pieces in a spaced mode; the first anti-instability piece and the second anti-instability piece are fixed to the two side supporting pieces respectively. The first clamping assembly can clamp the top of the composite material. The axial compression test clamp can be used for clamping a composite material subjected to side impact, and the problem that the accuracy of compression test data obtained after the composite material is subjected to side impact is not high is solved.

The invention belongs to the technical field of structural material design, and particularly relates to a method for determining an allowable value of an aviation composite material structure. The method mainly comprises the following steps: correcting a tension-compression strength allowable value according to a first ratio of the breaking strength of a single-side lap joint tension-compression test to the breaking strength of a single composite material tension-compression test; a plurality of second ratios of the shear failure strength of the composite materials with different thicknesses to the shear failure strength of a single composite material are formed through bonding, and the shear strength allowable value is corrected; correcting the allowable value of the tensile strength according to a plurality of third ratios of the tensile breaking strength of the composite materials with different thicknesses formed by screw connection to the tensile breaking strength of a single composite material; and correcting the allowable value of the compression strength according to a plurality of fourth ratios of the compression breaking strength of the composite materials with different thicknesses after impact breaking to the compression breaking strength of a single composite material. A basis is provided for relatively reasonable, safe and effective design of the composite material structure.

This invention proposes a simulation material for mechanical testing of press-loaded explosives, which, by weight, is made from the following raw materials: 65.5% ammonium sulfate, 27%–33% aluminum powder, 1.5%–4% microcrystalline wax, 1%–2% butadiene rubber, and 0.2%–0.8% graphite. The compressive and tensile strengths of the explosive charge formed by this simulation material are essentially consistent with those of the charge charge formed from polyaluminum black-2 (JHL-2) explosive. It can realistically reflect the trend and limit of strength changes during mechanical testing, and provides effective reference data for mechanical performance evaluation. It also provides relatively realistic and reasonable model parameters for the digital design of the mechanical properties of press-loaded explosives. In aging tests, tensile tests, mechanical compression tests, and dynamic Brazilian tests, using this simulation material avoids contact with energetic explosive components, increasing test safety and reducing safety hazards.

The invention relates to a metal material strain rate effect measurement method based on multiple stress relaxation, which comprises the following steps: carrying out a standard quasi-static stretching or compression test on a material sample at a constant strain rate to obtain a stress-strain curve; analyzing a strain range according to a stress-strain curve, and determining a stress relaxation frequency N to be developed and a corresponding relaxation strain value sequence epsilon i, i = 1... N; a material sample is taken to be subjected to a tensile or compression test at a set strain rate, stress relaxation lasts for relaxation time delta t when the strain sequentially reaches values in each relaxation strain value sequence, and after each stress relaxation, the tensile or compression test is performed according to the set strain rate; obtaining a stress-plastic strain rate curve corresponding to each relaxation strain epsilon i; and obtaining a stress-strain curve corresponding to each strain rate. Stress-strain curves corresponding to different plastic strain rates in a quasi-static range can be obtained through a single sample.

The utility model provides a kind of cord fabric pressure test device, the lower part of the clamp is provided with compression testing machine platform, the upper part of the clamp is provided with down device, the clamp includes clamp main body, the lower part of the clamp main body is provided with connecting flange, connecting pin passes from the inside of connecting flange, the clamp main body is surrounded with cord fabric, large clamp piece is installed in the both sides of the cord fabric, the large clamp piece is fixed in the clamp main body with cord fabric, small clamp piece is installed in the both sides of the upper side of the cord fabric, the small clamp piece is compacted in the upper side of cord fabric, spring is installed between the large clamp piece and clamp main body, the top of the clamp main body is provided with pressure head, connecting pin passes from the top of pressure head;The utility model can make contrastive analysis to data by a series of standardization test to cord fabric, prevent the risk of structural failure in advance, to reduce the risk of tire burst.

The utility model discloses a composite material compression test piece positioning tool which comprises a positioning block assembly, the positioning block assembly comprises an upper positioning block and a lower positioning block, and opposite plate surfaces of the upper positioning block and the lower positioning block are respectively provided with positioning raised lines corresponding to an upper notch and a lower notch; reinforcing sheet placing areas are respectively formed on two sides, corresponding to the positioning raised lines, of the upper positioning block and the lower positioning block; the baffle assembly comprises a left side baffle and a right side baffle, and the left side baffle and the right side baffle are arranged on the left side and the right side of the positioning block assembly respectively and connected with the upper positioning block and the lower positioning block through fasteners respectively; the positioning pin assembly comprises a plurality of positioning pins, a plurality of vertically corresponding positioning grooves are formed in the front ends and the rear ends of the upper positioning block and the lower positioning block respectively, and the positioning pins are inserted into the corresponding positioning grooves. According to the utility model, the symmetry of two reinforcing sheets is ensured, the stability of the reinforcing sheets in the positioning process is ensured, and the precision of a test piece is improved.

The utility model discloses an expandable compression testing machine, and relates to the technical field of compression testing machines. The device comprises a bottom plate, a compression mechanism is arranged on the bottom plate, the compression mechanism comprises a [-shaped frame fixedly connected to the top of the bottom plate, an electric push rod is fixedly connected to the top of the [-shaped frame, and an output shaft of the electric push rod extends into the [-shaped frame and is in sliding connection with the [-shaped frame. Accurate control over the moving path of the hold-down device in the compression process can be achieved through the compression mechanism, the possibility that the hold-down device deviates in the operation process is fundamentally eradicated, the accurate control enables the hold-down device to be kept highly stable in the moving process, and therefore when pressure is applied to a sample piece, the sample piece is not prone to deviation. The pressure can be ensured to uniformly and accurately act on the sample piece, the test error caused by non-uniform pressure or deviation is effectively avoided, the reliability and precision of the test result are remarkably improved, and more valuable data support is provided for scientific research and production.

The utility model relates to the technical field of geopolymer-foundation concrete combined test piece tests, in particular to a loading device for a tension and compression test of a geopolymer-foundation concrete combined test piece, which comprises a testing machine body, a test piece is arranged on a bottom supporting plate of the testing machine body, a top pressing plate is arranged right above the bottom supporting plate, and a top pressing plate is arranged right above the top pressing plate. The vertical surfaces of the bottom supporting plate and the top pressing plate are square; the loading device further comprises two right-angle plates and a driving part for driving the two right-angle plates to be synchronously close to or away from each other, and the direction in which the two right-angle plates are synchronously close to or away from each other is parallel to the diagonal line of the square surface of the bottom supporting plate; the maximum value of the distance between the two right-angle plates is larger than the length of the diagonal line of the square surface of the top pressing plate. According to the utility model, the test piece is ensured to be positioned at the central position of the bottom supporting plate during each test, so that the eccentric compression of the test piece is effectively avoided.

The present application relates to the technical field of clamp loading and unloading, and particularly relates to an automatic loading and unloading system and method of a hole compression test clamp. In the system, a positioning mechanism, a discharging mechanism, a gripper and a mechanical arm are included, the mechanical arm is used to drive the gripper to clamp the hole compression test clamp with a test piece; the hole compression test clamp includes two long clamping plates, two short clamping plates and two support plates, one long clamping plate, one short clamping plate and one support plate are fixed to each other through fasteners, the other long clamping plate, the other short clamping plate and the other support plate are fixed to each other through fasteners, and the two long clamping plates and the two short clamping plates are used to clamp the test piece made of fiber composite material; the positioning mechanism is used to position the hole compression test clamp by abutting against the side surfaces of the long clamping plates and the short clamping plates; and the discharging mechanism is used to dismount the test piece from between the two long clamping plates and between the two short clamping plates. The scheme can improve the loading and unloading efficiency of the hole compression test clamp.

The utility model discloses a compression test device for composite material thin-walled structure sample piece, including: clamps, anti-instability baffle and compression loading structure, the clamps are divided into two groups, are arranged at interval and are used for clamping the two side edges of the sample piece, each group of clamps comprises two support frames and two clamping plates, the two clamping plates in each group of clamps are respectively connected to the opposite sides of the two supporting frames in the group of clamps, and the opposite end surfaces of the two clamping plates in each group of clamps and the front and rear end surfaces of the corresponding side edges of the sample piece are designed in a shape following manner; the anti-instability baffles are correspondingly attached to the front portion and the rear portion of the sample piece, the two ends of each anti-instability baffle are connected with the two clamps respectively, and the compression loading structure is located over the position between the two clamps and used for applying compression loads to the sample piece. According to the compression test device, effective clamping of the sample piece can be guaranteed, instability and deformation of the sample piece in the compression process can be prevented, and the precision and reliability of a compression test are guaranteed.

The invention discloses a method for testing uniaxial compression mechanical properties of prefabricated fractured rock under the action of acid etching, which comprises the following steps: S1, preparing a sample, and taking deteriorated sandstone; s2, preparing a rock sample, namely preparing the modified sandstone into a standard cylindrical sample of phi 50 mm * 100 mm, and making a prefabricated fracture in the geometric center of the sample; s3, preparing a corrosive liquid with the pH value of 2; s4, dividing the rock samples prepared in the step S2 into two groups according to a fracture inclination angle alpha, wherein each group comprises four rock samples; wherein one group is used as a control group, is placed in air at room temperature for 48 hours and then is subjected to a uniaxial compression test; the other group of samples are immersed in the acidic solution with the pH value of 2 obtained in the step S3, four samples are obtained under each condition, and the samples are immersed for 20 d under the condition that the container is sealed; s5, performing a uniaxial compression test on a uniaxial compression testing machine; and S6, observing the rock sample damaged in the compression test by using Axia Chemi SEM to obtain the fracture development condition.

The invention discloses a filling body in-situ multi-field performance active monitoring and age-based mechanical testing device, and relates to the technical field of mine filling engineering in-situ testing and monitoring. Comprising a device body used for being immersed in underground filling slurry; the sample forming mold array is used for accommodating filling slurry in the same batch as the underground filling slurry to form a filling body sample; the multi-field environment communication structure is used for enabling the filling slurry to be in heat, water, force and chemical field communication with an external filling body; the in-situ multi-field monitoring system is used for synchronously monitoring multiple environmental parameters of the external filling body; and the age-based mechanical testing system is used for carrying out in-situ uniaxial compression tests on the filling body samples at different curing ages. According to the invention, on the premise of keeping heat-water-force-chemical communication between an underground filling body and an external filling body and establishing a pore pressure transmission condition, sample curing maintenance can be carried out, demolding can be completed in the same device without manual coring / block taking, and uniaxial compression and other mechanical data can be obtained in batches according to the age.

The invention discloses an ancient building brick masonry surface deterioration repair material and a weather resistance evaluation method thereof, and belongs to the technical field of brick masonry ancient building repair, the repair material contains three optimization systems: a lime-fly ash system (S-F), a cement mortar-fly ash system (L-F) and a calcium hydroxide-silica fume mixing system (C-S. The preparation process is simple and convenient. According to the evaluation method, the mass loss rate, the innovatively defined wave velocity degradation rate and the compressive strength are integrated, an extreme environment is simulated through a freeze-thaw cycle test, ultrasonic flaw measurement and compression test are combined, a full-dimension evaluation system is formed, and a long-term damage prediction curve is constructed through data fitting. Tests show that the cement mortar-fly ash system is optimal and meets the repair requirements. The internal damage is quantified according to the wave velocity degradation rate, a scientific basis is provided for material screening and long-term maintenance, and the method has engineering value and cultural heritage protection significance.

The invention belongs to the field of crustal stress measurement, and provides a crustal stress measurement method based on a nonlinear mechanical theory, which comprises the following steps: firstly, measuring a stress-strain curve of a strain hardening material to obtain mechanical parameters, and then constructing a measurement platform comprising a concrete cube, an elastic-plastic thick-wall cylinder and a precise range finder; the thick-wall cylinder is embedded into a concrete through hole and is internally provided with a precise range finder to monitor the change of the inner diameter. A compression test is carried out through multiple groups of horizontal pressure stresses, numerical simulation is combined, and a nonlinear model about the horizontal pressure and mechanical parameters and geometric parameters of the thick-wall cylinder is constructed by applying a Bayesian neural network and a data augmentation technology. The method comprises the following steps: placing a crustal stress observation instrument in an underground soft rock area or a fracture zone deep hole, continuously monitoring the change of the inner diameter of a thick-wall cylinder after coupling with concrete, and determining maximum and minimum principal stress and directions according to a nonlinear model; by means of the method, scientific and technical support can be provided for deep ground scientific exploration and underground engineering construction.

The invention discloses a method for synchronously characterizing mechanical properties and microscopic deformation of an explosive at a high temperature, which is suitable for synchronously characterizing mechanical properties and microscopic deformation of explosive granular mixtures, grains and other energetic material crystals or granular materials. The test process comprises the steps of sample preparation, sample installation, connection of a fatigue testing machine and a scanning electron microscope, parameter adjustment of the scanning electron microscope and the fatigue testing machine, temperature rise, temperature-mechanical-electron microscope synchronous test and the like. And a set of special compression test tool is designed, so that real-time dynamic characterization of mechanical properties and microstructure deformation under a high-temperature condition is realized. According to the method, the deformation characteristics of the explosive in the pressing process can be dynamically monitored in real time, the test process is observable, the test conditions are more scientific and reasonable, the microscopic morphology monitoring of the explosive in the deformation process is realized, the characterization accuracy is improved, and meanwhile, the method is simple to operate and has low requirements on experimenters.

The utility model discloses an energizable bidirectional tension and compression mechanical testing machine chuck device, which belongs to the field of material mechanical property testing, and comprises a plurality of machine tools, the plurality of machine tools are oppositely arranged, the number of the machine tools is four, the machine tools are arranged in a cross shape, a mounting plate 102 is integrally arranged at the tail end of the upper surface of each machine tool 100, and a driving assembly 201 is mounted on the mounting plate 102. The output end of a coupler on the driving assembly is connected with a ball screw, the ball screw is slidably sleeved with a sliding table, a connecting plate is arranged at the front end of the sliding table, a mounting hole is formed in the middle of the front surface of the connecting plate, a tension sensor is fixedly inserted into the mounting hole, and the front end of the tension sensor is connected with a clamp. According to the utility model, the yield process of the material in different stress states can be more comprehensively observed by carrying out two-way tension and compression tests on the material under the electrifying condition, and a new yield criterion suitable for the complex loading condition can be established by analyzing the two-way tension and compression test data under the electrifying condition; and the prediction capability on the yield behavior of the material is improved.

The application relates to the technical field of battery materials, in particular to a paste charging material compression test device and a test method thereof, which comprises a testing machine support, a sample box mounted on the testing machine support, a compression test box and a protective gas source box, the inside of the sample box is provided with a temperature control room, and the inside of each layer of the separated rooms is provided with an automatic feeding mechanism and a heating plate. The application prevents the external environment from affecting the test results through the settings of the sample box, the temperature control room, the lifting chamber and the compression test box, reduces the influence of the temperature accuracy reduction caused by manual operation through the settings of the multiple separated rooms in the temperature control room, realizes rapid testing of multiple samples, and also facilitates the control test, so that the device has high universality, the settings of the automatic feeding mechanism, the vertical lifting support, the first electric push rod and the second electric push rod do not need manual feeding and discharging, reduce manual intervention and external influence, and further improve the accuracy of the test.

The invention provides a method for detecting the compressive strength of a solid propellant in a viscous state. The method comprises the following steps: step 1, processing the size of a sample: processing the solid propellant to be detected into a medicine column; step 2, heat preservation treatment: putting the grain prepared in the step 1 into an environmental box, and preserving heat, so that the solid propellant to be detected in the grain is in a viscous state. The grain subjected to heat preservation treatment in the second step is put into an environment box of a universal material testing machine, the temperature of the environment box is the same as the heat preservation temperature, and the compression resistance test is conducted till the compression resistance value reaches 102% or above of the qualified value required by the product. And 4, flaw detection test: sending the grain pressed in the step 3 into an industrial CT, and carrying out DR imaging scanning in the industrial CT to obtain a DR scanning picture. And 5, result judgment: observing whether damage such as cracks and gaps occurs in the DR scanning picture, if not, judging that the compressive strength of the product is qualified, otherwise, judging that the compressive strength of the product is unqualified. The method solves the problems that the compressive strength value of the solid propellant in the viscous state cannot be directly obtained through a compressive test, and then whether the product is qualified cannot be judged, and has the advantages of being visual, reliable, accurate in result and the like.

This invention provides a high-temperature compression test fixture device for composite materials suitable for DIC strain testing, belonging to the field of composite material mechanical property testing technology. The device includes a front clamping block assembly and a rear clamping block assembly, each comprising an upper clamping block and a lower clamping block, connected by a guide rod. Each upper and lower clamping block includes a main body for clamping the side of the test specimen and a lateral extension extending from one side of the main body, such that both the upper and lower clamping blocks have an L-shaped cross-section. The main bodies of the front and rear clamping block assemblies are connected by fasteners to clamp and fix the test specimen. The guide rod is disposed on the lateral extension to ensure that it does not obstruct the working area surface of the test specimen. This invention enables accurate measurement of the full-field high-temperature compressive strain of composite materials through a DIC strain testing system.

The application belongs to the technical field of strength test of single lug joint of vertical tail wall plate root of an airplane, and particularly relates to a radial compression test loading structure of a single lug joint shaft hole of a vertical tail wall plate root of an airplane, when strength test is performed by using the radial compression test loading structure, a test machine can apply a pressure load on a wall surface of a loading pressure platform, the pressure load can be transmitted to a shaft hole of a single lug joint of a single lug joint test piece through a support bushing and a loading shaft, a radial compression load is applied in the shaft hole of the single lug joint, in the process, two support bushings can support the single lug joint of the single lug joint test piece from two sides, two support plates can support a transition section of the single lug joint test piece from two sides, lateral deviation of the single lug joint test piece is prevented, and the two support bushings and the support plates can follow the loading pressure platform to follow the support, the stress environment of the single lug joint can be well ensured, and the accuracy of a test result can be ensured.

The utility model discloses a clamp for a compression test of a composite material foam sandwich structure, which comprises a base plate, two angle plates, a bottom guide plate, a side guide plate and a top guide plate, the four side face guide plates are correspondingly installed on the opposite end faces of the two angle plates in pairs and used for restraining the edges of the two sides of a sample piece, the front-back distance between the two side face guide plates installed on the same angle plate is adjustable, the two bottom guide plates are installed on the base plate in a front-back spaced mode, and the distance between the two bottom guide plates is adjustable. The two top guide plates are arranged on the end part loading plate in a front-and-back spaced manner, and the distance between the two top guide plates is adjustable, and the two top guide plates are used for restraining the top edge of the sample piece. The compression test device is simple in structure, can adapt to sample pieces with different thicknesses, and can effectively restrain the sample pieces.

The application provides a kind of composite material curing process mechanics performance time-varying characteristic characterization method and device, the method comprises the following steps: step one: obtaining the reaction enthalpy released by unit mass of the measured prepreg complete curing;Step two: obtain a plurality of compression samples and DSC samples;Step three: using composite material repair instrument simultaneously to cure compression sample and DSC sample, terminate curing process at different preset time for each group of samples, and record the temperature T of each group of samples at the time of curing termination;Step four: for each group of samples, the compression modulus of compression sample after step three at corresponding temperature T is measured by using mechanical testing machine, and the curing degree of DSC sample after step three is obtained;Step five: according to a plurality of curing degrees and compression modulus, the modulus of resin under different curing degrees is obtained by using self-consistent field micromechanics model, and then the mechanics performance time-varying characteristic of composite material curing process can be obtained.The application fully combines the characteristics of composite material repair instrument, which can terminate the curing process of composite material safely and controllably at any time, the mechanical properties in the thickness direction of composite material, and the easy implementation of compression test, solves the problems of difficult processing of mechanical samples of composite material under different curing degrees and different temperatures, difficult measurement of mechanical properties, and realizes the accurate measurement of the mechanics performance time-varying characteristic of composite material.

The present application relates to the method for determining the shear strength of calcareous sand under different stress paths quickly, comprising the steps of using the same initial porosity, grading, sample preparation method, saturation method, preparing multiple calcareous sand samples; performing isotropic compression test; obtaining particle size distribution curve, calculating relative breakage rate; again performing isotropic compression test; performing three different stress path tests; recording the deviatoric stress and axial strain in the three different shear processes; obtaining the maximum value of deviatoric stress; obtaining particle size distribution curve, calculating total relative breakage rate; calculating the relative breakage rate of three shear stages; drawing data scatter plot; obtaining fitting parameters, obtaining the fast prediction equation The present application is more suitable for predicting the shear strength of calcareous sand foundation under complex engineering environment; only through simple screening test, the shear strength of calcareous sand can be obtained; it is more suitable for actual engineering; it is more practical; and it provides valuable theoretical basis.

A laminated film 10 is provided with a base film 11 and a rubber layer 12 that is laminated on the base film 11 and contains an elastomer as a main component. The amount of deformation in the thickness direction as measured by the compression test A mentioned below is 14.5 μm or more.　<Compression Test A> A pressure of 5 MPa is applied in the thickness direction from the rubber layer 12 side of the laminated film 10 under the conditions of a temperature of 25°C and a compression speed of 50 g / min by using a cylindrical compression probe having a diameter of 1 mm.

The invention belongs to the technical field of composite material structural strength tests, and discloses an edge restraint device and method for a residual strength test of a composite material sheet after impact, and the device comprises a base, a side support, a top plate and a set of edge distributed clamping system. The system is composed of a bottom clamping module, a top clamping module and a plurality of pairs of lateral clamping modules which are arranged side by side and can be independently adjusted, and the bottom edge, the top edge and the two side edges of a test piece can be accurately and adjustably clamped in a distributed mode. Through adjusting mechanisms such as strip-shaped holes, screw holes and puller bolts on each module, optimized attachment with each edge of the test piece and clamping force control can be realized, crushing of the edge of the test piece and premature overall buckling instability in the compression test process are effectively prevented, and the accuracy and reliability of a residual strength test result after impact are ensured. The device is particularly suitable for testing the large-size composite material thin plate.

The invention belongs to the technical field of compression strength testing, and discloses a compression test method for a composite laminated board after arc edge impact, which comprises the following steps: determining the design configuration of a test piece; determining boundary constraint conditions of the test piece based on the design configuration of the test piece; carrying out simulation analysis of a compression test on the test piece according to the design configuration and the boundary constraint condition of the test piece; if the simulation result meets the test requirement, executing the step S4; if the simulation result does not meet the test requirement, the step S1 to the step S3 are executed again until the simulation result meets the test requirement; according to the design configuration of the test piece, manufacturing the test piece and introducing impact damage to the arc edge of the test piece; clamping and fixing the test piece according to the boundary constraint condition of the test piece, and carrying out a compression test; and obtaining test data obtained by the compression test, and processing and analyzing the test data. According to the method, instability can be effectively prevented, and the actual compression breaking strength can be accurately obtained.

The invention discloses an unginned cotton compression test device and method. The unginned cotton compression test device comprises a rack, a rolling and pressing belt, a pressing head and a camera, the rolling and pressing belt and the pressing head are respectively arranged on the rack or the force application element to realize a seed cotton rolling and pressing test and a flexible boundary compression test; the rolling and pressing belt comprises a packing belt, a left clamping head and a right clamping head, the two ends of the packing belt are connected with the left clamping head and the right clamping head into a whole through tooth-shaped openings respectively, and a film pressure sensor is pasted to the surface of one side of the packing belt in the radial direction; the right clamping head is provided with a long-strip-shaped opening, and the left clamping head and the packing belt penetrate through the long-strip-shaped opening so that the packing belt can be rolled into a cylindrical structure. The pressing head comprises an upper pressing head and a lower pressing head; cylindrical tension and compression sensors with threads are arranged on the left chuck, the upper pressure head, the right chuck and the lower pressure head; the camera is fixed on the rack through threaded connection; the seed cotton rolling and pressing test and the flexible boundary compression test are completed by changing the placing mode of the rolling and pressing belt and the pressing head, the two tests are achieved through the same device, combination of the two test devices is achieved, and operation is easy.

The invention discloses a small-diameter pipe joint sealing device and method. The sealing device comprises a piston and an O-shaped sealing ring. The piston is a rotary body and comprises a head portion located at the first axial end and a tail portion located at the second axial end, an annular groove for assembling an O-shaped sealing ring is formed between the head portion and the tail portion, and the head portion is a smooth curved surface. The tail part comprises a conical surface which is used for sealing and is relative to a piston rotation axis and a pair of flat surfaces which are parallel and symmetrical about the piston rotation axis; and through holes are formed in the flat surfaces. Before a pressing test, a metal wire penetrates into the through hole, the length of the metal wire is reserved, and then the head of the piston is pressed into an inner cavity of the small-diameter pipe joint until the conical surface of the tail is attached and the O-shaped sealing ring is compressed. After the test is finished, the piston is pulled out by pulling the metal wire. The sealing device is safe and reliable in sealing, good in sealing effect and convenient to assemble and disassemble.

The present application relates to the technical field of rock mechanics test monitoring and safety early warning, and specifically discloses a failure early warning device and method for rock uniaxial compression test, which comprises the following steps: real-time acquisition of load data and displacement data of rock samples in the process of rock uniaxial compression test; preprocessing of the load-displacement data and determination of the optimal sliding window length; calculation of real-time tangent stiffness and stiffness degradation rate of the rock samples in the process of loading; conversion of the load-displacement data into stress-strain data, obtaining of dissipated energy and dissipated energy change rate; construction of continuous damage variable and obtaining of damage evolution rate; weighted combination of the stiffness degradation rate, the dissipated energy change rate and the damage evolution rate, obtaining of a comprehensive early warning index and analysis of the evolution trend, determination of whether the rock sample enters the instability early warning range, and output of early warning information. The present application can realize early identification of the instability development trend of rock, significantly improve the safety of the test, and has a wide range of application.

The present application relates to the technical field of composite material testing, and particularly relates to a compression clamp after edge impact. The clamp comprises: a support seat for supporting a test piece to be compressed after edge impact, the test piece being a composite laminated plate; two clamping plates for clamping the test piece, each of the clamping plates being provided with a first avoiding groove and a second avoiding groove facing the test piece, the first avoiding groove being used for avoiding a protrusion formed by the test piece after edge impact, and the second avoiding groove being used for avoiding a strain gauge installed on the surface of the test piece. The scheme can meet the requirements of end loading compression test after edge impact.