513 results about "Strain measurement" patented technology

The invention provides an indoor crustal stress test device and method based on optical strain measurement, the test device comprises a stress simulation device, the stress simulation device can perform real three-dimensional crustal stress environment simulation on a test rock mass as far as possible; the drilling releasing device is provided with a hollow drill bit used for drilling the optical strain measurer installed in the test rock mass, and the drilling hole and the hollow drill bit are coaxially arranged. Thus, according to the method, pressure is applied to the test rock mass from multiple directions through the multiple hydraulic loading columns, the real three-dimensional crustal stress environment can be more accurately simulated, speckle image changes in the speckle coating can be continuously recorded in real time through the optical strain measurer, and hole wall strain data are obtained; and converting the strain data into stress by applying an elastic theoretical formula, and accurately calculating the stress state of the experimental rock mass.

The invention discloses a multi-scale strain measurement method for a metal material at an ultralow temperature, and the method combines a DIC technology and HR-EBSD analysis, and achieves the precise strain measurement from a macro scale to a micro scale. Macroscopic strain distribution on the surface of a sample is accurately captured through a DIC technology, and HR-EBSD analysis is utilized to further go deep into a microscopic level, so that a microscopic deformation mechanism of a material in an ultralow-temperature environment is disclosed. The overall strain of the material is researched from the macroscopic perspective, the specific region of interest in the macroscopic strain state is further deepened, the microscopic strain distribution of the region of interest is explored, and the deformation behavior and the mechanical property of the material at the ultralow temperature can be more comprehensively understood. Besides, a non-direct contact type heat exchange mode is adopted, so that accurate temperature control is realized, and meanwhile, the influence of water mist or condensation and the like generated by evaporation and condensation of a cooling medium on a test result is avoided.

The invention discloses a creep test system of a turbine rotor blade film hole simulation piece and a test method of the creep test system. Comprising a clamping assembly used for fixing a test piece, a loading assembly used for applying a load to the test piece, a strain measuring assembly used for measuring the strain rate of the test piece, a heating assembly used for covering the test piece to form a heating channel, and a cooling assembly used for manufacturing and conveying cooling airflow to flow through the interior of the test piece, the strain measurement assembly is used for measuring the external temperature of the test piece and the internal temperature of the test piece, the control assembly is connected with the strain measurement assembly, the heating assembly, the cooling assembly and the temperature measurement assembly, and the heating assembly is used for manufacturing and conveying high-temperature airflow to flow through the heating channel so as to heat the outside of the test piece to a first set temperature; the cooling assembly is used for cooling the interior of the test piece to a second set temperature, and the heating assembly and the cooling assembly are used for forming a dynamic convection environment around the test piece.

The invention belongs to the field of material mechanical property testing and strain measurement, and particularly relates to a local strain measurement method and system based on a four-point bending and digital image correlation (DIC) technology, and the method specifically comprises the following steps: cutting to prepare a sample, carrying out surface electrolytic polishing, preparing speckles on the surface of the sample to be tested, and carrying out a four-point bending experiment; speckle images of the lower surface of the sample are collected, displacement correction is conducted in combination with bending deflection calculation, the bending load and the strain of the upper surface of the sample are obtained in real time, the stress-strain relation and local strain distribution of the lower surface of the sample are obtained through calculation, and finally deformation and failure mechanism analysis is conducted in combination with surface deformation and crack morphology. The method provided by the invention combines four-point bending and DIC plane strain measurement technologies, can realize stretching, compression and dynamic fatigue loading on the surface of the sample, is suitable for performance test and failure analysis of tension, compression and fatigue deformation of brittle metal materials such as intermetallic compounds and amorphous materials, and has the characteristics of convenience, rapidness and low cost.

The invention provides a multifunctional rock test system under a multi-field coupling condition, which is internally provided with a reaction cabin, a rock sample is placed in the reaction cabin, and the system is internally provided with an axial force loading control system, a confining pressure oil circulation system, a high-temperature heating and control system, an injection pump system and a temperature and strain measurement system. The subsystems are respectively in communication connection with the computer display and control system and are respectively used for controlling the pressure or temperature in the reaction cabin; the test method based on the system comprises the following steps: 1) processing a rock sample; 2) assembling a rock sample; 3) loading the rock sample into a reaction cabin; the method comprises the steps of (1) preparing a rock sample, (2) assembling a reaction cabin, (5) initializing a system and fixing the rock sample, (6) providing a confining pressure environment for the rock sample, (7) providing a high-temperature environment for the rock sample, (8) providing a triaxial high-pressure environment for the rock sample, (9) providing a chemical field and osmotic pressure environment for the rock sample, (10) providing water pressure for the rock sample and monitoring pressure, temperature and strain changes, (11) relieving pressure, cooling and recovering confining pressure oil, and (12) sorting and processing data.

The invention relates to a method for dynamically measuring a composite material under an ultra-high-temperature working condition, which comprises the following steps of: constructing a composite material high-temperature strain dynamic detection platform, and respectively acquiring speckle images of a tested piece under a cold state condition and an ultra-high-temperature working condition as data sets; constructing a supervised network model for eliminating speckle image thermal radiation and thermal disturbance influence, wherein the supervised network model comprises a multi-scale feature extraction module, a dual convolutional neural network and a polarization self-attention mechanism; constructing a joint loss function L for the supervised image restoration network model; training the model to obtain an optimal image restoration network model; an ultra-high-temperature speckle image serves as input, a speckle image restoration result is output through the image restoration network model, and a displacement field is obtained through DIC calculation; according to the invention, the influence of thermal radiation, thermal disturbance and haze phenomena in an ultra-high temperature environment on image quality is effectively eliminated, and the dynamic strain measurement precision of the composite material under an ultra-high temperature working condition is remarkably improved.

The invention relates to the technical field of structural deformation shape reconstruction, in particular to a novel inverse finite element deformation reconstruction method based on virtual deformation field physical constraint. According to the method, a virtual displacement field obtained by sparse strain through inverse finite element reconstruction is used as a strain extrapolation physical constraint; and an iteration thought is adopted, extrapolated strain and measured strain are used for inverse finite element deformation reconstruction again, a new virtual displacement field is obtained, and therefore strain extrapolation can be restrained again. And continuously iteratively reconstructing virtual deformation and extrapolation strain in this way, and finally reconstructing real structural deformation. And determining the accuracy rate of the deformation characterization values based on a plurality of actually measured actual deformation characterization values and a plurality of deformation characterization values determined by the extrapolation strain data, and determining the deformation reconstruction state based on the accuracy rate. According to the method, the strain measurement points are extrapolated through iteration in the deformation reconstruction process, and the virtual displacement field is used as physical constraint, so that the accuracy of deformation reconstruction is improved.

The invention discloses a corrugated steel web bridge deformation monitoring temperature lag compensation method and system, and the method comprises the steps: constructing time sequence data of a corrugated steel web, the time sequence data comprises a time sequence composed of a wave crest temperature, a wave trough temperature, a strain measurement value, a wind speed and solar radiation intensity in any fold period of the corrugated steel web at any moment; according to the time sequence data, calculating the temperature lag time of the temperature to the structure response by using a sliding cross correlation coefficient algorithm of the frequency domain energy weight; time sequence data are reconstructed according to the temperature lag time, and the reconstructed time sequence data are obtained to serve as state vectors of the corrugated steel web; the state vector of the corrugated steel web is input into the strategy network of reinforcement learning, an optimal action instruction of the next step is output and obtained, and the optimal action instruction comprises the step that a compensation signal is applied to time sequence data; according to the optimal action instruction, the predicted state vector of the corrugated steel web at the next moment is obtained; and obtaining a strain prediction value of the corrugated steel web according to the state vector of the corrugated steel web at the next moment. Dynamic and high-precision compensation of the corrugated web bridge temperature hysteresis effect is achieved for the first time.

The invention relates to a winding spray pipe forming process internal temperature strain measurement method and a winding spray pipe, and the method comprises the steps: winding first winding cloth on the surface of a winding core mold, laying a grating fiber sensor between the first winding cloth to form an inner layer structure, and enabling a part of the grating fiber sensor to be located in the inner layer structure, the other part extends out of the inner layer structure; vacuumizing the inner-layer structure, then transferring the inner-layer structure into an autoclave for curing, and carrying out a conduction test on the grating optical fiber sensor; the inner layer structure is taken out of the autoclave, second winding cloth is used for winding the surface of the inner layer structure, a grating optical fiber sensor is laid between the second winding cloth, a spray pipe winding piece is formed, part of the grating optical fiber sensor is located in the second winding cloth, and the other part of the grating optical fiber sensor extends out of the second winding cloth; vacuumizing the spray pipe winding piece, then moving the spray pipe winding piece into an autoclave for curing, and performing a conduction test on the grating fiber sensor; and the spray pipe winding piece is taken out of the autoclave for demolding.

The invention belongs to the technical field of metamaterial sensors, and particularly relates to a metamaterial multi-parameter sensor for a complex environment, which comprises a dielectric substrate, a temperature sensor, a pressure sensor and a strain sensor, and is characterized in that the dielectric substrate is made of high-temperature co-fired alumina ceramic; the temperature sensor is arranged at the left end of the dielectric substrate; the pressure sensor is arranged in the middle of the medium substrate; and the strain sensor is arranged at the right end of the dielectric substrate and comprises a metal sheet structure capable of generating relative displacement. According to the invention, long-distance signal monitoring is realized by adopting a microwave scattering technology, and the problem that a traditional wired sensing transmission line is damaged at a high temperature is solved; the high-temperature-resistant aluminum oxide HTCC ceramic is used as the dielectric substrate, temperature measurement within the range of 25 DEG C to 1200 DEG C, pressure within the range of 0 kPa to 700 kPa and strain measurement within the range of-400 mu epsilon to + 400 mu epsilon are achieved, the sensor is smaller in size and higher in sensitivity, and application of a traditional sensor in the multi-metal environment is expanded.

The disclosure relates to monitoring blades of a wind turbine rotor shaft. Example embodiments include a computer-implemented method of monitoring blades of a wind5 turbine (100), the wind turbine (100) having a plurality of blades (103a, 103b) mounted to a hub (102), each blade (103a) comprising one or more strain sensors (109a1-3) mounted to the blade (103a) at corresponding respective distances from the hub (102, 201) along the blade (103a), the method comprising: i) recording (1301) strain measurements from the strain sensors (109a1-3) on each of the plurality of blades10 (103a); ii) recording (1302) a rotor speed of the wind turbine (100); iii) calculating (1303) a statistical measure of each of the recorded strain measurements; iv) calculating (1304) a difference in the statistical measure for strain sensors at corresponding positions on each of the plurality of blades over a range of rotor speeds; and v) identifying (1305) the presence or absence of damage in one of the plurality of blades15 based on the calculated difference.

The invention discloses a rock shear seepage coupling true triaxial test system, which relates to the technical field of rock mechanical tests, and comprises a host, a sigma 1 / sigma 2 direction loading module, a sigma 3 direction confining pressure module, a pressure chamber auxiliary system, a sample clamp, a pore water seepage system, a temperature system, a control module and a data acquisition and processing module, through servo closed-loop linkage double-pump loading in the sigma 1 / sigma 2 direction, synchronous output of the double pumps and coordination of pressure supply of the two oil cylinders by the controller, a strain correction algorithm is combined, stability of a stress loading center is guaranteed, strain measurement accuracy is improved, confining pressure is accurately controlled in the sigma 3 direction through a double-balance pressure chamber and a pressure regulation algorithm, and the stress measurement accuracy is improved. The pressure chamber is in full-automatic operation, manual steps are omitted, errors are reduced, efficiency is improved, a stress-free blank angle clamp eliminates friction interference, a seepage system supports a double-loading mode, a control module achieves multi-control-mode impact-free switching, a data processing module is combined with an elastic modulus calculation algorithm, rock mechanical parameters are accurately obtained, and the multi-field coupling test requirement is met.

The invention provides an anti-counterfeit label film coating tension control method and system, and relates to the technical field of film coating tension control. The method comprises the following steps: acquiring surface image data of a substrate film; identifying and acquiring real-time coordinates of the feature points; calculating the local strain of the substrate film according to the real-time coordinates of the feature points; calculating to obtain a strain deviation; calculating the time required by the film section corresponding to the strain deviation to reach the film coating station as the adjustment time; calculating a tension compensation amount according to the strain deviation; and within the adjusting time, the tension control unit adjusts the tension applied to the substrate film according to the tension compensation amount. According to the method, through accurate local strain measurement and prospective tension adjustment, it is ensured that each section of film is kept in an ideal strain state at the moment of film coating, so that the integrity and functional effectiveness of optical microstructures such as diffraction gratings are thoroughly protected, and the technical problems in anti-counterfeit label film coating production are effectively solved.

The invention provides a surgical robot tail end three-dimensional force sensing mechanism and a force measurement method, and relates to the technical field of force measurement, and the surgical robot tail end three-dimensional force sensing mechanism comprises a first connecting end used for connecting a surgical instrument, a second connecting end used for connecting a surgical robot mechanical arm, and a first strain measurement unit arranged between the first connecting end and the second connecting end. The first strain measurement unit comprises a strain structure and a measurement assembly, the strain structure is provided with a first strain part, a second strain part and a third strain part, and the three strain parts are elastically deformed under acting force in a first direction, a second direction and a third direction which are perpendicular to one another; a first strain assembly, a second strain assembly and a third strain assembly of the measuring assembly are correspondingly installed on three strain parts, and the three components are matched to measure acting force borne by the surgical instrument in the first direction, the second direction and the third direction. The measurement limitation of a one-dimensional sensor is broken through, and the measurement of the acting force borne by the surgical instrument in three dimensions is realized.

The invention relates to the technical field of mechanical property testing of metal materials, and provides an unsteady-state in-situ high-temperature forming property testing device and method. A punch constant strain rate loading model is arranged in the device, the punch moving speed is adjusted in real time to realize punch constant strain rate loading, and the rheological behavior of a constant strain rate sensitive material in a complex stress state is accurately tested; a rapid cooling system is arranged, so that accurate simulation of complex unsteady-state forming processes such as actual hot stamping and warm forming is realized, and the unsteady-state in-situ high-temperature forming performance of the material is obtained; in combination with a DIC dynamic strain measurement technology, a strain field and deformation force are collected in real time in a plate high-temperature plane stress bulging test, and local necking strain and main strain and secondary strain change paths are determined. According to the method, the reliability of researching macroscopic rheological behaviors such as strain field distribution, flow behavior, hardening mechanism, forming limit and fracture limit of the plate in a complex stress state can be remarkably improved.

A monocular three-dimensional-based visual deformation measurement system provided by the present invention comprises an integrated platform, the upper surface of the integrated platform is provided with an image acquisition assembly, a light splitting assembly, two groups of light reflecting assemblies and two groups of light supplementing lamps, the image acquisition assembly is arranged on the rear side of the light splitting assembly, and the two groups of light reflecting assemblies are arranged on the left and right sides of the light splitting assembly in a bilateral symmetry manner. The two light supplementing lamps are arranged on the sides, away from the light splitting assembly, of the two light reflecting assemblies correspondingly and rotationally connected to the upper surface of the integrated platform. Compared with a contact type strain gauge, three-dimensional full-field deformation and strain measurement can be achieved, and meanwhile the response speed is higher. Compared with a binocular three-dimensional DIC technology, the calibration difficulty is reduced, meanwhile, the demand quantity of CCD cameras is reduced, and the hardware cost is greatly reduced.

The invention discloses a component multi-dimensional information measurement method and system based on multi-source information fusion, and the method comprises the steps: 1, obtaining a fluorescence speckle image and a texture image before deformation, and decomposing the two images into low-frequency features and high-frequency features through discrete wavelet transform; 2, fusing low-frequency features of the fluorescence speckle image and the texture image before deformation; fusing the high-frequency features of the fluorescent speckle image and the texture image before deformation; 3, reconstructing the fused low-frequency features and high-frequency features through inverse wavelet transform to obtain a fused image before deformation; 4, acquiring a fused image after deformation; 5, the three-dimensional shape of the component is obtained through an FPP method; then calculating a sub-pixel-level displacement field, and constructing a three-dimensional displacement field according to the three-dimensional morphology and the sub-pixel-level displacement field; and extracting a partial derivative of the three-dimensional displacement field to the pixel coordinate, and calculating the Green strain tensor. According to the invention, the interference of environmental factors on displacement and strain measurement is effectively overcome, and the measurement precision and robustness are improved.

The invention discloses a chip carrier plate flexible leveling system and a control method, and relates to the technical field of photoetching machine parts and chip production. According to the scheme provided by the invention, a parallelism detection device constructed based on a strain detection device is utilized, and a mapping relation between a strain value and an inter-plate distance is established; during use, a plurality of parallelism detection devices are arranged between a chip carrier plate and a target substrate, high-precision parallelism measurement and feedback adjustment are realized through a mapping relation between strain values and inter-plate distances and based on numerical value differences of strain measurement values, accurate inter-plate parallelism adjustment is realized, and the accuracy of the inter-plate parallelism is improved. The technical problem that an existing leveling system is large in parallelism detection and leveling effect error is solved.

The invention discloses a composite strain sensing network which comprises FBG sensors and a flexible fabric strain sensor, and the multiple FBG sensors are located on an optical fiber. The optical fibers are transversely and longitudinally arranged on the surface of the tank body; each strain sensor is arranged next to the FBG sensor, and the pasting direction is consistent with the pasting direction of the FBG sensor. The invention further discloses a tank deformation measuring method. The method comprises the following steps: carrying out strain measurement on the tank; establishing a coordinate system, and calculating coordinate values of all sensor position points through a mathematical relationship between strain and deformation according to the positions of the measuring points of the composite strain sensing network; dividing the surface of the tank body into n sub-regions, establishing a quadric surface function for each sub-region, weighting according to the strain of each point, solving an equation by using a weighted least square method, and obtaining a curved surface function of each sub-region; and integrating the curved surface functions of all the sub-regions to obtain the overall deformation condition of the tank body. The method has the advantages of comprehensive and accurate measurement and the like.

A strain measurement apparatus (100) for measuring mechanical strain in a sample (1) comprises a sample holder device (10) being arranged for accommodating the sample (1) to be investigated, an indenter device (20) including an indenter tip (21) and an actuator stage (22) carrying the indenter tip (21), wherein the actuator stage (22) is arranged for an application of a localized mechanical load along a load axis z1 via the indenter tip (21) at an indentation zone (2) of the sample (1) accommodated by the sample holder device (10), when the sample holder device (10) is in a load application position, a confocal Raman microscopy device (30) having an imaging axis z2 and being arranged for collecting at least one Raman spectrum in the indentation zone (2) of the sample (1), and a calculation device (40) being arranged for calculating at least one strain parameter based on the at least one Raman spectrum, wherein the sample holder device (10), the indenter device (20) and the confocal Raman microscopy device (30) are arranged such that the confocal Raman microscopy device (30) is capable of collecting the at least one Raman spectrum, while the sample holder device (10) is in the load application position, and the indenter device (20) and the confocal Raman microscopy device (30) are arranged such that the load axis z1 of the actuator stage (22) and the imaging axis z2 of the confocal Raman microscopy device (30) coincide. Furthermore, a strain measurement method for measuring mechanical strain in a sample (1) is described.

The invention belongs to the technical field of strain sensing, and particularly relates to a high-precision strain sensor based on a hollow optical fiber, which comprises an optical fiber Fabry-Perot interference cavity, and the optical fiber Fabry-Perot interference cavity is formed by welding a section of hollow optical fiber between a first optical fiber bragg grating and a second optical fiber bragg grating; and the PDH high-precision demodulation module is used for carrying out real-time demodulation on a reflected signal of the optical fiber Fabry-Perot interference cavity and outputting a strain measurement result. The system is simple in structure and convenient to implement, the PDH demodulation technology is introduced, the change of dependent variables is monitored in real time, and integration is facilitated; the sensing degree of a strain signal is increased by utilizing the characteristics of the hollow optical fiber; the resonant cavity is stable in interference phenomenon and convenient for long-term detection; and by adopting an all-fiber optical path, the device has the advantages of high measurement precision, small size, easiness in embedding into a to-be-measured structure and the like.

A sensor apparatus includes at least one substrate layer of an elastically deformable material, the substrate layer extending longitudinally between spaced apart ends thereof. A conductive layer is attached to and extends longitudinally between the spaced apart ends of the at least one substrate layer. The conductive layer includes an electrically conductive material adapted to form a strain gauge having an electrical resistance that varies based on deformation of the conductive layer in at least one direction.

The invention relates to a contact type heating high-temperature tensile test system suitable for plates in the technical field of material high-temperature mechanical property testing, and the system comprises a loading module which is used for being connected with a testing machine and cooperating with a clamping module to apply an acting force to a sample so as to realize a tensile process; a heating block of the heating module is controlled by an air cylinder with a free stroke to move so as to be tightly attached to the sample for heating, and a window for observing the sample is formed in the external heat preservation box; according to the device, a contact type heating mode is adopted to achieve heating of a sample piece, the heating speed is high, the sample is heated evenly, the sample can rotate by 90 degrees, heating and strain measurement are achieved respectively, laser temperature measurement and the heating rod are coupled through the temperature controller, accurate control over the temperature is achieved, and the device is simple in structure, convenient to operate and high in practicability. The high-temperature area and the normal-temperature area are separated by a thermal insulation material, and the high-temperature area adopts clearance fit to ensure sufficient thermal expansion space of the pin, so that high-temperature adhesion is prevented.

The invention discloses a resistance strain gauge sensitivity coefficient measuring device, which belongs to the technical field of resistance strain measurement and comprises a support, a displacement generation mechanism, a displacement detection mechanism and a steel ruler. The displacement generation mechanism comprises a swing arm and a mounting seat, the swing arm is mounted on the support and forms a lever structure, two ends of the straight steel ruler are detachably connected with the short arm end of the swing arm and the support respectively, and a strain gauge pasting area is arranged on the surface of the straight steel ruler; the displacement detection mechanism comprises at least one displacement sensor. The upper end of the steel ruler can be driven to generate axial displacement of a corresponding distance through the lever action of the swing arm, so that the strain gauges synchronously generate telescopic deformation, the real strain of the steel ruler and the strain gauges can be directly measured through the displacement sensor, and finally the sensitivity coefficient can be obtained according to the resistance change rate of the strain gauges. And the reliability and the effectiveness of a measurement result are improved.

The invention provides a strain measurement method based on a GCN neural network, and the method comprises the steps: collecting a speckle image and a speckle displacement field of a tested piece according to the actual working condition demands, and forming a data set for the subsequent training and testing of a measurement model; building a speckle displacement measurement model according to the GCN neural network; inputting the data set into a speckle displacement measurement model for training to obtain optimal measurement model configuration, and performing displacement measurement on deformation of the speckle image to obtain a prediction result of speckle displacement; and calculating the strain of all points in the speckle image based on the obtained speckle displacement prediction result, and gathering to form a surface strain field of the measured object. According to the method provided by the invention, the deformation stress of the high-temperature material component can be accurately measured by building the speckle displacement measurement model based on the GCN neural network, and high-precision and real-time strain measurement in a high-temperature environment is realized.

The invention provides a device for testing the circumferential tensile stress and strain curve of a pipe. The device comprises a circumferential tensile sample, an upper buckle, a lower buckle, an upper D-shaped block, a lower D-shaped block and a connecting rod. The testing method comprises the following steps: uniformly spraying speckles on the outer surface of the reducing section of the annular tensile sample before testing, and measuring the strain in the linear length and width directions of the reducing section of the annular sample by using a three-dimensional full-field strain measurement and analysis system in the annular tensile process. Adjusting the position of the circumferential tensile sample, so that the included angle between the central line of the reducing section and the tensile direction is 30 degrees, and the infrared spots of the high-resolution camera are emitted to the middle upper part of the reducing section of the sample. And finally, starting the universal testing machine to stretch at a fixed speed. The method has the advantages that the circumferential tensile stress and strain curve of the pipe can be directly and accurately tested, and the method has important theoretical and practical significance for accurately constructing an anisotropic thin-wall pipe plastic constitutive model and realizing high-precision simulation of thin-wall tubular member forming.

The present invention relates to systems and methods for monitoring microseismic activity in a geothermal well system using fiber optic sensing technology. The system includes fiber optic cables installed in multiple wells of the geothermal well system. The fiber optic cables enable simultaneous collection of distributed acoustic sensing (DAS) data, strain measurements, and temperature data. By detecting and localizing microseismic events during stimulation and operation of the geothermal well system, seismic activity is maintained within safety thresholds, providing for safe and effective extraction from the geothermal well system.

The invention relates to an extensometer returning device, an extensometer combination and a high-temperature strain measurement device, the high-temperature strain measurement device disclosed by the invention is equipped with the extensometer returning device, and the extensometer combination can slide on a guide rail according to requirements; the extensometer returning device is provided with a steering engine and a moving wheel, and the steering engine can be controlled to drive the moving wheel to slide on the longitudinal sliding rail; when the strain of the extensometer reaches the maximum value and the temperature exceeds a safety range, the extensometer returning device can release fixation according to a sensor signal and drive the steering engine to rotate reversely to drive the extensometer to be separated from the loading test device and reversely return to a starting point, so that the function of protecting a contact rod of the extensometer is achieved; the extensometer returning device is provided with a gear pump, and the maneuvering platform and the extensometer body are fixed on the guide rail through transmission of the connecting rod assembly, so that automatic separation of the extensometer and the sample is realized.

The invention relates to a fiber bragg grating strain sensor and a preparation method thereof. The method comprises the following steps: providing a metal substrate of which the surface is provided with a strain groove for accommodating a fiber bragg grating; placing a fiber bragg grating in the strain groove, and applying pre-strain to the fiber bragg grating; covering a packaging material on the strain groove area provided with the fiber bragg grating, wherein the packaging material comprises a mixture of metal powder and glass powder; and sintering the substrate covered with the packaging material to melt the glass powder and bond and solidify the metal powder to form a composite packaging body for packaging and fixing the fiber grating in the strain groove. According to the invention, the interface thermal stress caused by the difference of thermal expansion coefficients of materials is reduced, the temperature cross sensitivity of the sensor is effectively inhibited, and the strain measurement precision and long-term stability of the sensor in a wide temperature range are improved.

The invention relates to the technical field of strain measurement, and discloses a tunnel steel arch bearing capacity early warning method and system.The method comprises the steps that micro-strain pulses, curvature change voltage and high-frequency stress wave signals of key nodes of a steel arch are synchronously collected; fusing the strain change rate and the curvature acceleration to calculate a dynamic load gradient distribution parameter; stress wave energy abrupt change characteristics and voltage equivalents are extracted through wavelet packet decomposition and frequency domain differential; inputting the load parameters and the energy characteristics into a coupling damage evaluation model, and generating a real-time stress risk coefficient through exponential attenuation correction and convolution operation; and when the voltage equivalent exceeds a self-adaptive threshold value and the risk coefficient meets a critical condition, triggering a stress grading early warning instruction. According to the method, the problem of lack of a multi-physical-quantity cooperative monitoring and dynamic risk assessment coupling mechanism during early warning of the bearing capacity of the tunnel steel arch is solved, and the early warning precision and timeliness are remarkably improved.