287 results about "Crack initiation" patented technology

The invention relates to the technical field of machine vision structure health monitoring, and discloses a steel structure weld fatigue cracking real-time monitoring system based on machine vision. The system comprises a space-time registration and fusion module, a multi-scale feature analysis module, a health monitoring module, a crack deduction calculation module and a regulation and control strategy generation module. Performing space-time registration and pixel-level fusion through the visual data of the plurality of image sensors to generate a synchronous multi-source image stream; a multi-level welding seam characteristic spectrum is constructed through multi-scale characteristic analysis, and a welding seam structure knowledge base is dynamically updated; the knowledge base and the real-time characteristic spectrum are used for monitoring the welding seam health state, and abnormity is recognized; deducing a crack initiation position and an evolution path in combination with historical damage data; and real-time load information is fused to pre-estimate the remaining service life, and a structural integrity regulation and control strategy is generated online. According to the invention, high-precision fusion of the multi-source visual data and active prediction of the crack trend are realized, and the monitoring accuracy and the early warning capability are improved.

The invention provides a method for evaluating the crack resistance of tunnel body concrete, and belongs to the technical field of wind tunnels, and the method comprises the steps: uniformly arranging multiple types of sensors on the surface of a tunnel body concrete structure to form a high-density monitoring network, employing a concrete circular ring constraint test piece to establish an anti-crack reference database, and constructing a multi-working-condition temperature stress database; acquiring multi-dimensional data such as strain, temperature and acoustic emission in real time, inputting the monitoring data into a liquid adaptive neural network model to predict crack initiation probability and expansion risk, establishing a crack risk assessment function, formulating a corresponding processing strategy according to a risk coefficient range, and starting an intelligent spray maintenance system; a closed-loop control system from monitoring perception to risk early warning to active protection is formed, and the technical problem that crack initiation and expansion risks of a hole body concrete structure cannot be accurately predicted under complex working conditions is solved.

The invention discloses a concrete anti-cracking method and system based on fiber reinforcement, and belongs to the technical field of concrete anti-cracking. The method comprises the following steps: acquiring real-time strain data in concrete through a distributed optical fiber sensor; analyzing the data to obtain a three-dimensional crack propagation path containing a crack initiation position, a propagation angle and a tip position; identifying the dominant development direction of the crack and a fan-shaped potential expansion interval which extends at an expansion angle by taking the tip as a vertex based on the path data; in the potential expansion interval of the to-be-poured area, a fiber distribution layer arranged in the dominant development direction is formed through directional arrangement equipment; and the fiber-reinforced anti-cracking structure is formed through vibrating and compacting treatment. According to the invention, directional blocking of fibers to crack expansion is realized, the problem of disordered expansion of cracks is effectively solved, and the anti-cracking efficiency of concrete is improved.

The invention provides a rock porosity adaptive modeling and blasting crack expansion calculation method based on key-type near-field dynamics, and the method comprises the steps: constructing a unified near-field dynamics model containing pore adaptive generation and blasting dynamic response; dynamic simulation of the rock blasting process is realized through pore distribution control, blasting load time history application and crack evolution judgment, and crack initiation, expansion and penetration rules can be accurately reproduced while the calculation stability is ensured. By introducing a pore adaptive discrete algorithm, the construction of rock models under different porosity conditions is automatically realized, and the initiation, expansion and penetration processes of cracks in the rock mass are accurately predicted in combination with near-field dynamics mechanical calculation under the action of an explosion load. According to the method, the heterogeneous characteristic of the rock and the discontinuous effect of the blasting load can be considered at the same time under a unified dynamic framework.

The invention discloses an ejector pin anti-fatigue strengthening method based on multi-section variable-temperature treatment, and relates to the technical field of ejector pin anti-fatigue strengthening, and the ejector pin anti-fatigue strengthening method comprises the following steps: austenitizing high-temperature quenching: heating an ejector pin to an austenitizing temperature, and then carrying out zoned cooling on the ejector pin; medium-temperature tempering and thermal-state mechanical strengthening are conducted, specifically, the ejector pin is tempered at the medium-temperature tempering temperature, and thermal-state shot blasting or laser shock is conducted on the ejector pin in the heat preservation period or after heat preservation is completed; intermediate low-temperature plasma nitriding: carrying out plasma nitriding in a nitrogen-hydrogen gas environment; subzero treatment: placing the ejector pin in liquid nitrogen; and finally, low-temperature tempering and cold-state mechanical strengthening are conducted. Through multi-section temperature gradient treatment, phase change distribution control over different temperature sections is achieved, too high internal stress and brittleness generated by one-time quenching are avoided, sudden size change and hot cracks induced by phase change are prevented, a controllable surface-core hardness and toughness gradient is formed, the surface crack initiation tendency is reduced, and the surface quality is improved. And the consistency and controllability of anti-fatigue basic conditions are improved.

The invention discloses a method for evaluating damage evolution of an underground structure under the action of a sudden explosion load, and relates to the technical field of civil engineering and engineering disaster prevention, and the method is characterized by comprising the following steps: S1, simulating the underground structure based on an explosion load, a geometric boundary and material parameters, and constructing a unified constitutive model; and S2, introducing a pressure-related strength criterion of a Dwark-Prasugrel criterion into the unified constitutive model so as to describe the influence of confining pressure on the shear strength. The technical problem to be solved by the invention is to provide the method for evaluating the damage evolution of the underground structure under the action of the burst explosion load, so that the key pain points such as pressure correlation, high strain rate effect, material random discreteness, damage softening energy consistency and the like are difficult to consider at the same time in the existing analysis method. A set of damage evolution evaluation method and implementation system which can be implemented from the material level to the structure level is established, and quantitative prediction and engineering grading judgment of the whole process of crack initiation, expansion to instability failure of the underground structure are supported.

The application discloses a super-soft austenitic stainless steel and a preparation method thereof. The super-soft austenitic stainless steel is composed of carbon C, nitrogen N, silicon Si, manganese Mn, chromium Cr, nickel Ni, copper Cu and iron Fe. The mass percentage of each component in the super-soft austenitic stainless steel is as follows: C: 0.005%-0.02%, N: 0.05%-0.2%, Si: 0.01%-0.1%, Mn: 1.5%-6.5%, Cr: 15.5%-19.6%, Ni: 7.5%-13.5%, Cu: 1.8%-5.3%, and the balance is iron. The super-soft austenitic stainless steel has the characteristics of low tensile strength and hardness, low strain-induced martensite in the bending process, low crack initiation rate and low failure fracture.

The invention relates to the technical field of material science, and discloses a slurry valve erosion-resistant multi-layer coating with gradient function design and a preparation method thereof.The coating comprises a bonding layer, a gradient function layer and an erosion-resistant surface layer which are sequentially arranged from inside to outside, the bonding layer is composed of nickel-based alloy or cobalt-based alloy, the thickness of the bonding layer is 50-100 micrometers, and the thickness of the gradient function layer is 50-100 micrometers. The gradient functional layer is made of composite powder of metal and ceramic, the metal is nickel or cobalt, the ceramic is tungsten carbide or chromium carbide, and the components of the gradient functional layer are from the bonding layer side to the erosion-resistant surface layer side; the bonding layer is arranged and forms firm metallurgical bonding with the matrix, the interface stress is reduced, the basic reliability of bonding of the coating and the matrix is guaranteed, meanwhile, the gradient functional layer with the metal and ceramic volume fraction gradually changing continuously is adopted, the problem that the thermal expansion coefficients of the coating and the matrix are not matched is solved, and the service life of the coating is prolonged. And the crack initiation and expansion risk caused by internal stress concentration is reduced, so that the long-term stability of the coating structure is ensured.

The invention discloses a tight-lock coupler intelligent tensile testing machine and a testing method thereof, and belongs to the technical field of tight-lock coupler test.The tight-lock coupler intelligent tensile testing machine comprises a mounting bottom plate and an electric control cabinet, and a support for supporting a tight-lock coupler to be detected is mounted on the surface of the mounting bottom plate; a tensile connecting frame for connecting the tight-lock coupler is mounted on the surface of the bottom plate on one side of the support, an integrated design of'tensile force detection and visual detection 'is innovatively adopted, mechanical parameter acquisition and visual deformation observation are combined, traditional mechanical data such as tensile force and displacement are obtained, and visual characteristics such as fine deformation and crack initiation are captured; precise synchronization of pulling force application, displacement collection and camera shooting is achieved through the synchronous controller, the real-time corresponding relation of pulling force-displacement-visual deformation is established, the problems that an existing device is single in detection dimension and poor in data relevance are solved, and the potential quality hazard checking capacity and the persuasion of a detection result are improved.

The invention discloses a research method for a crack evolution law of fractured rock under thermal-mechanical coupling, and belongs to the technical field of rock mechanics. Aiming at the problem that most indoor tests and numerical simulation at present still lack systematic research on crack initiation, polymerization and failure behaviors of cracks in a multi-crack rock mass under the action of high temperature-stress coupling, the method comprises the following steps: defining an interaction coefficient and a thermal damage influence coefficient between the cracks on the basis of a tangential stress distribution theory around the cracks; establishing a tangential stress model sum of the inner and outer surfaces of the crack comprehensively considering the coupling effect of the two to predict a potential crack initiation position; based on a crack mode displacement decomposition method, defining a displacement ratio coefficient gamma, and quantifying a displacement field of rock material cracks; on the basis, the rock sample is subjected to mechanical test and PCF numerical simulation, and the crack evolution law of the rock sample containing the prefabricated crack under thermal-mechanical coupling is researched. Theoretical support and experimental basis can be provided for stability evaluation and safety control of deep high-temperature rock mass engineering.

The invention discloses a method for evaluating a fatigue weak area of a welded joint based on crystal plasticity, which aims at the problem of fatigue failure of the welded joint caused by complex microstructures such as grain orientation difference and uneven grain size distribution, establishes a quantitative correlation model of grain orientation and size evolution through CPFEM, and combines a macro-micro cross-scale analysis method to evaluate the fatigue weak area of the welded joint. And precise prediction of local stress concentration and crack initiation behaviors of the welding joint under a real fatigue load working condition is realized, so that scientific evaluation of a fatigue weak region is completed. According to the method, an innovative framework of fatigue weak area evaluation is constructed through load working condition reduction and grain characteristic multi-scale coupling, so that excessive simplification of a traditional method on real load conditions is made up, the limitation that a traditional model is difficult to couple a microstructure and a real load is overcome, and the fatigue weakening quantization precision is remarkably improved; and a high-precision analysis technology is provided for anti-fatigue design, process optimization and service life evaluation of the engineering welding structure.

The invention relates to the technical field of composite film strength detection, and discloses a composite film peel strength testing device which comprises a testing platform, two pulling sliding plates slidably mounted in the two extending parts respectively and capable of being synchronously and mutually close to or away from each other for adjustment, and the two pulling sliding plates are arranged on the testing platform. The opposite ends of the two pulling sliding plates are each provided with a clamp used for clamping a single-layer film of a composite film separation section. The clamping assembly is arranged in the test platform and is used for clamping and limiting the fitting section of the composite membrane and enabling the separation section and the fitting section of the composite membrane to form a Y-shaped state; and two groups of test assemblies. Through the Y-shaped constant-angle stripping design, the stripping surface of the composite film is uniquely locked, the stripping angle is kept unchanged in the whole testing process, and the effects that stripping cracks are stably limited to a specified unique interface, crack initiation is controllable and deviation is avoided are achieved.

The invention relates to the technical field of state monitoring, in particular to a ship main transmission device wear state real-time monitoring and maintenance system which comprises a load path recognition module, an abrasive particle distribution monitoring module, a thermal field response judgment module, a crack evolution tracking module and a maintenance adjustment module. According to the method, the strain data of the front end and the rear end of the main shaft are subjected to time sequence comparison, so that the strain transfer trend in a transmission path can be dynamically captured, and path parts in an abnormal abrasive particle peak value state can be screened out in combination with the mapping relation between the number of particulate matters and the particle size grade; according to the method, a potential thermal response imbalance area in a local structure is identified by combining the change trend of the difference between the axial temperature rise rate and the radial temperature rise rate, meanwhile, pre-judgment of a crack initiation section is completed by combining the peak sudden change characteristic of the number of structural node strain fluctuation times, and real-time identification, trend study and judgment and risk early warning of the running state of the main transmission device are achieved. And timeliness and accuracy of maintenance response are improved.

The invention discloses a CO2 directional fracturing target layer crack propagation simulation control method based on flow regulation and control. The method comprises the steps that a plurality of experimental coal samples are manufactured, and drill holes are formed; the fracturing pump inputs CO2 with set flow into the coal sample through the CO2 injection pipeline; the high-frequency dynamic pressure sensor collects fluid pressure data in the coal sample crack; the acoustic emission sensor monitors and obtains the crack initiation moment and crack initiation pressure of the coal sample; the method comprises the following steps: carrying out cracking and crack width monitoring on a coal sample, calculating a theoretical value of crack initiation pressure and a theoretical value of CO2 injection flow of the coal sample, injecting supercritical CO2 fluid into the coal sample, obtaining a first-stage correction coefficient and a second-stage correction coefficient of the CO2 injection flow, and calculating a corrected CO2 injection flow value. According to the method, under the multi-physical-field coupling environment, the crack initiation pressure of the coal body can be accurately measured and calculated, the correlation between the CO2 injection flow and the crack width of the coal body is established, and the CO2 injection flow better meets the actual requirements of field operation through a CO2 injection flow grading correction mechanism.

The invention relates to the technical field of mechanical fatigue testing, in particular to rotary bending fatigue testing equipment for a rotor shaft, which comprises a base, a rotary driving module, a loading module, a dynamic balance module, a crack monitoring module and an adjusting module, and is characterized in that the rotary driving module drives the rotor shaft to rotate through a belt transmission assembly; the loading module adopts a lever type force reversing mechanism to realize accurate bending moment loading; the dynamic balance module automatically counteracts eccentric vibration through a free disc and a symmetrical bearing seat; the crack monitoring module captures vibration abnormity and internal crack initiation in real time; and the adjusting module is automatically adapted to different shaft lengths by driving a threaded screw rod through a motor. Anti-slip lines are arranged on the inner sides of the clamps at the two ends to ensure stable clamping; the levers are symmetrically arranged and matched with the locking nuts, so that switching of translation force or bending force applied by the levers is facilitated, the equipment realizes high-precision and full-period fatigue test, and the device is suitable for reliability evaluation of key rotor parts of aero-engines and steam turbines.

The invention discloses an equivalence evaluation method for testing the fracture behavior of an irradiation metal material based on a small sample, belongs to the field of mechanical property testing, and deeply researches the size effect problems of non-uniform deformation and crack initiation of the metal material under the irradiation condition through three research means of experiments, theories and simulation. And a powerful basis is provided for performance evaluation of the metal material under the irradiation condition. In the aspect of experiments, micro-stretching and micro-cantilever beam experiments of samples with different sizes under irradiation conditions are carried out, and a correlation mechanism between irradiation material crack initiation and sample sizes is analyzed. On the theoretical aspect, a dislocation channel-grain boundary interaction model is established, and prediction of fracture toughness of irradiation samples of different sizes is achieved. In the aspect of simulation, a finite element simulation system for non-uniform deformation, crack initiation and size effect of the metal material under the irradiation condition is established, and the influence of irradiation and sample size on microstructure evolution and macroscopic fracture behavior of the material is explored.

The invention discloses coal rock hydraulic fracturing crack dynamic evolution monitoring equipment and method, and the method comprises the steps: firstly applying three-way independent stress to a coal rock test piece through a true triaxial loading module, and simulating an underground true stress environment; then an ultrasonic excitation module is started, an ultrasonic physical field excitation environment is applied to the coal rock test piece, and development of microcosmic fractures in the coal body is promoted; and the high-pressure pump injection module is started, high-pressure water is injected into the coal rock test piece at constant flow or constant pressure, and more efficient hydraulic fracturing is achieved under excitation of the ultrasonic physical field. In the whole process, the acoustic emission monitoring module captures an elastic wave signal generated by coal rock fracture in real time, and the microcrack initiation position is accurately positioned; the CT scanning module obtains the three-dimensional expansion morphology of the macroscopic crack through scanning; and finally, through a multi-physical field cooperative loading and multi-scale monitoring technology, the whole-process dynamic representation from microcrack initiation to macroscopic crack penetration is realized, and a theoretical support and a technical means are provided for efficient development of coal bed gas.

The invention discloses a non-contact uniaxial compression test infrared strain meter and a use method thereof, and belongs to the field of rock mechanics and engineering testing. The objective of the invention is to solve the prominent problems of low measurement precision, easy influence by characteristics of a test object, difficulty in comprehensively and accurately reflecting full-field strain distribution and the like of a traditional contact type strain measurement device in a uniaxial compression test. A non-contact infrared imaging measurement technology is adopted, a high-speed infrared camera is matched with a DIC algorithm, real-time mapping of full-field strain distribution is accurately achieved, transient behaviors such as crack initiation and expansion are clearly captured, strain field data and temperature field data can be synchronously obtained, measurement of the strain field data and the temperature field data are organically combined, and by means of the infrared technology and an environment control device, the measurement accuracy is improved. The device can stably work in severe environments such as high temperature and corrosivity, and is suitable for various complex samples; according to the method, the accuracy and comprehensiveness of measurement are effectively improved, the test efficiency is greatly improved, the method can be widely expanded to multiple fields of civil engineering, aerospace and the like, and powerful support is provided for research on mechanical properties of materials.

The invention provides an FDEM-based rock blasting process simulation method and system considering blasting gas, and the method comprises the steps: building a jointed rock blasting numerical model comprising a blast hole, a rock mass and a joint network based on a finite element-discrete element coupling method; setting a static-dynamic unified boundary condition for the jointed rock mass blasting numerical model, and applying a blasting stress wave load; constructing an explosion gas action model, and dynamically calculating a transient explosion cavity area and transient gas pressure; transient gas pressure is coupled and applied to the boundary of the crack and the surface of the isolated rock; and operating the solver, simulating the whole process from stress wave propagation, joint attenuation effect, crack initiation and propagation to blasting gas driven crushing and throwing, and analyzing the result. The method provided by the invention overcomes the defect that the existing method is difficult to simultaneously and accurately characterize the joint effect and the action of the blasting gas, obviously improves the authenticity and reliability of the simulation of the blasting rupture process of the jointed rock mass, and provides an effective tool for blasting mechanism research and engineering optimization design.

The invention relates to the technical field of metal material surface engineering and equipment remanufacturing, in particular to an early acoustic emission diagnosis and laser cladding repair method for thermal fatigue cracks in a mold service process, which comprises the following steps: S1, synchronously acquiring and preprocessing multi-source heterogeneous data; stress wave signals are collected in real time through a broadband acoustic emission sensor array permanently integrated on the surface of a mold cavity, the frequency response range of the sensor is 100 kHz to 1 MHz, and the sensitivity is not lower than 95 dB. According to the method, accurate identification and positioning can be realized at the initial stage of crack initiation through multi-modal sensing fusion and a deep learning algorithm, the diagnosis accuracy is remarkably higher than that of a traditional offline detection method, and precious time is won for subsequent repair.

The invention is suitable for the technical field of remanufacturing of key parts of aero-engines and gas turbines, and provides a laser strengthening composite cladding high-performance repairing method for an engine supporting plate. Comprising the following steps of pretreatment and damage evaluation, uncoated laser shock peening pretreatment, composite cladding material design and preparation, coaxial powder feeding laser cladding repair, post-treatment and performance recovery and final inspection and performance evaluation. According to the method, by means of a synergistic structure of coating-free LSP pretreatment and laser cladding, a pre-compressive stress layer pre-constructed on a base body is pretreated, tensile stress generated by rapid heating and cooling in the cladding process can be effectively counteracted, and crack initiation and extension of the interior of a cladding layer and a bonding interface are inhibited from the source; meanwhile, thermal stress accumulation is further reduced through partition staggered scanning and interlayer temperature control in S4, and the crack rate of a repaired area is remarkably reduced through the dual effects; performing performance transcendental recovery; and the method is pollution-free, high in reliability and good in manufacturability.

The invention discloses a numerical simulation method for a heat-fluid-solid multi-field coupling response characteristic, which relates to the technical field of mechanics and engineering simulation and comprises the following steps of: constructing an asynchronous sampling array, performing joint time-frequency acquisition on a periodic pressure pulsation signal of a fluid and a dynamic response signal of a solid structure, extracting a coupling phase fingerprint baseline, and calculating the coupling phase fingerprint baseline. As a unified reference for energy analysis; and performing coherent decomposition based on the coupling phase fingerprint baseline, calculating a phase-locked energy index, identifying an instantaneous resonance window in a dynamic evolution process, and determining a dangerous frequency band and an interface fragile area. According to the method, unified reference of heat-fluid-solid response data is realized by constructing a coupling phase fingerprint baseline; predicting a crack initiation threshold in combination with anti-fact playback and a risk cone; extracting a minimum disturbance set to construct an energy dissipation channel; time reversal micropulses are applied to cooperate with phonon band gaps and shadows for energy storage, phase lock release and vibration extinguishing control are completed, and closed-loop regulation and control of structure safety are achieved.

The invention relates to the technical field of rock mechanics and underground engineering, in particular to an anchored jointed rock mass multi-field coupling creep characteristic analysis method which comprises the following steps: preparing anchored rock mass samples which are corroded by inorganic salt and contain different joint occurrences, and installing different pre-stressed anchor rods. And carrying out a graded loading creep compression experiment, and synchronously collecting axial deformation and acoustic emission signals. And drawing a creep time-history curve based on deformation data, and determining long-term strength and a creep stage by adopting a steady-state creep rate method. And calibrating the crack initiation and expansion process of the crack at each stage of creep deformation by using an acoustic emission signal. And analyzing response differences between crack development and anchoring failure under different inorganic salt components, concentrations, joint occurrence and prestressing forces, and determining the influence degree of each factor on the anchor rod support effect in each creep deformation stage. According to the method, synchronous quantitative analysis of macroscopic creep characteristics and microscopic damage evolution is realized by coupling chemical corrosion and prestress action, and the accuracy of long-term strength prediction and anchoring failure mechanism understanding is improved.

The invention provides an LNG (Liquefied Natural Gas) conveying flexible pipeline crack initiation and extension prediction method, which comprises the following steps of: constructing a multilayer composite structure geometric model, and defining thermal parameters and mechanical parameters of each layer of material in the model; presetting an initial crack in the model, and establishing a thermal-mechanical coupling control equation containing an interface thermal resistance effect; applying an internal ultralow temperature boundary condition, an external environment temperature boundary condition and a mechanical load boundary condition; solving the thermal-mechanical coupling control equation to obtain temperature field distribution of the section of the pipeline, applying a temperature field as a body load to the multilayer composite structure geometric model, and calculating to obtain a stress field and a stress intensity factor of a crack tip; constructing a crack propagation criterion considering the interface thermal resistance effect; and comparing the stress intensity factor obtained by calculation with a crack propagation criterion, and judging whether the crack is propagated or not. According to the method, the physical authenticity and calculation precision of crack initiation and propagation prediction of the LNG flexible pipeline in the ultralow temperature environment are improved.

The application discloses a component fatigue micro-damage early identification method based on a nonlinear static component, and particularly relates to the technical field of material nondestructive testing and structural health monitoring, which comprises the following steps: arranging an excitation probe and a receiving probe on the surface of a component to be measured; selecting an excitation frequency based on a frequency dispersion curve and generating a Hanning window modulated wave; collecting a propagation response signal; extracting a static component amplitude A and a fundamental wave amplitude A through time-frequency processing; calculating a nonlinear static parameter beta=A / A²; further calculating a first derivative S(N) and a second derivative ΔS(N) of beta with respect to a fatigue loading cycle N; and identifying a dislocation dominant stage, a dislocation saturation or rearrangement stage, a micro-crack initiation stage and a macro-crack formation stage according to the first derivative S(N) and the second derivative ΔS(N). The application can be used for early stage identification of the evolution process of component fatigue micro-damage.

This invention discloses a rapid generation method for rectangular disks suitable for structured meshes. This method simplifies crack propagation calculations of the disk into a parametric fracture mechanics model, enabling the calculation of stress intensity factor and crack propagation life. Specifically, finite element modeling is employed to extract the geometric boundaries of the disk and its partitions, considering the influence of geometric dimensions and boundary effects on crack propagation. Based on coordinate system transformation, using the crack initiation point and stress gradient direction as a reference, the rectangular plate can be accurately located, improving modeling efficiency. This invention simplifies the crack propagation plane into a finite-size rectangular plate. Based on boundary intersection point capture, it achieves high-fidelity equivalence between the rectangular plate model and the actual complex contour of the disk, reducing calculation errors in the boundary region using traditional methods. Furthermore, by extracting the crack-free stress distribution along the crack propagation direction on the rectangular plate, the stress intensity factor at the crack tip and crack propagation life can be calculated using the weighted function method.

The closure member is configured for use in a valve. These configurations can have a coating or conformal layer that can cover most, if not all, of the underlying material. This layer can include pre-propagated cracks that form through thermal cycling prior to use. These pre-propagated cracks act as stress relief to accommodate thermal stresses that may arise due to different thermal expansion rates between the underlying closure member and the coating. In one implementation, the layer can include a crack profile designed to direct the formation of pre-propagated cracks and to prevent crack initiation to a certain depth in order to maintain at least some integral layer of material above the underlying plug (118). This feature can extend the useful life of the plug, especially in aggressive process fluids, such as particulate-laden fluids common in hydrocracking and refining operations.

This invention discloses a method for improving the low-temperature impact toughness of high-strength heat-treated steel rails, comprising the following steps: composition control, smelting and refining, rare earth modification treatment, continuous casting / billing and heating homogenization, two-stage controlled rolling forming, online heat treatment with graded cooling and residual heat recovery, slow cooling on a cooling bed and straightening finishing. This invention determines the composition window based on the common constraint range of two sets of steel chemical composition standards for rails, and through the synergistic control of purification, effective rare earth modification, two-stage controlled rolling for grain refinement, and the online graded cooling and residual heat recovery heat treatment path, it reduces the sensitivity to low-temperature crack initiation, constrains the phase transformation path, and weakens the coupling between residual stress and microstructure embrittlement. Thus, while meeting the requirements for high strength, hardness, and wear resistance, it achieves qualified and stable low-temperature impact toughness.

The invention belongs to the technical field of structural health monitoring, and particularly provides a fiber grating displacement sensing-based crack propagation real-time monitoring and early warning method and system, and the method comprises the steps: carrying out the real-time monitoring and early warning of crack propagation on the basis of strain wavelength signals collected by a fiber grating sensor array which is arranged on a miter gate in a fan shape, and employing a finite element digital twin database and a signal matching algorithm; and multi-dimensional characteristic values such as crack length, opening displacement and stress intensity factors are extracted, and the accuracy of crack state recognition is improved by combining multi-measuring-point signal fusion and fracture mechanical analysis. Through combination of gate operation load characteristics and crack propagation rules, a mapping relation between sensor data characteristics and a database is matched, and accurate identification of crack initiation, propagation paths and danger levels is realized. The monitoring and early warning system provided by the invention can realize full-life-cycle online automatic diagnosis, quantitative evaluation and early warning positioning of gate cracks from microscopic expansion to macroscopic failure, and is expected to solve the problem that the hydraulic metal structure cracks are difficult to quantitatively monitor and safely predict in real time.

The application discloses a high-durability micro-nano structure carbon ceramic composite brake disc and a preparation method thereof. Gradient nanoparticle distribution is used to realize the synergistic optimization of surface protection and core Si infiltration efficiency. A high SiC concentration is used in the surface layer to inhibit the corrosion of molten Si through a double mechanism of physical blocking and chemical passivation, and the friction coefficient fluctuation is significantly reduced. A low SiC concentration is used in the outer layer to reduce the penetration resistance of molten Si, ensure the uniformity of Si infiltration, and reduce the difference in the thermal expansion coefficient. Meanwhile, the lamination needling process improves the performance through a double mechanism of mechanical interlocking and fiber orientation optimization. The needling density of 12-20 needles per unit area makes the barb of the needle penetrate the carbon fiber layer to form a physical anchor, the needling process optimizes the Si infiltration channel, the interlayer gradient structure and the three-dimensional network formed by needling disperse the braking stress, and the interface debonding risk is reduced. In the high-strength frequent braking scene, the crack initiation probability is reduced, the local stress of the brake disc is reduced, the wear rate is effectively reduced, and the braking process is more stable.