126 results about "Fracture mechanics" patented technology

The invention discloses a three-dimensional speckle strain measurement method, comprising: (1) speckle preparation; (2) camera calibration; (3) state information acquisition; (4) computational domaindesignation; (5) initial point setting; (6) speckle matching; (7) three-dimensional reconstruction; and (8) strain computation. By the above operation steps, the invention provides a three-dimensionalspeckle strain measurement method, which can effectively obtain high preciseness measurement results in measurements of material characteristic parameters such as full-field vibration measurement, dynamic strain measurement, high speed deformation measurement, fracture mechanics, impact excitation and dynamic material experiments. The invention has the characteristics of convenient measurement operation, high automation degree, exact and reliable results, high efficiency and non-contact measurement.

The object of the invention is to make available implant elements or other medical products made of biological material with optimum mechanical and biological properties for a wide group of materials by introduction of a specially designed surface layer onto a strong core, where the surface layer is densified by means of hot isostatic pressing and dimensioned according to the basic fracture mechanics equation so that the thickness of the surface layer is less than c in the equation KIC=Ysigma c½, where Klc is the fracture toughness, Y a position and shape factor, c the critical defect size, and sigma the permitted stress for the actual material and the chosen design stress.

The present invention relates to a method for measuring steel structure bridge life by utilizing fracture mechanics. It includes an ultrasonic inspection process of steel structure bridge member, and utilizes actually-measured data to correct analog data so as to raise accuracy of structural calculation. Said measurement method includes seven steps: structural mechanics modeling, mechanical model correction, traffic load modeling, traffic load correction, ultrasonic inspection, member fracture mechanics model modeling and bridge structure technical state judgment.

The invention relates to the calculation of parameters to inform hydraulic stimulation of non-conventional hydrocarbon-bearing rock formations, such as shales. Unlike conventional formations, non-conventional formations tend to display elastic-plastic behavior and have stress-strain characteristics which with substantial non-linear regions. A parameter which has been termed Elastic Index (EI) is proposed, together with a demonstration of how this parameter, when coupled with principles of fracture mechanics, may be used to extract meaningful calculated or estimated values for e.g.; total required volume of fracturing fluid; treating pressure; fracturing fluid viscosity; proppant size; and proppant concentration.

The invention discloses a single-shaft tensile overall true stress-true strain curve testing technique. According to the technique, a single-shaft tensile test is performed on a round rod sample, and an equivalent true stress-true strain curve which can really reflect the tensile overall deformation characteristics of a material can be solved through finite element simulation iteration. The testing technique disclosed by the invention can realize the overall equivalent true stress-true strain curve of the single-shaft tensile until fracture of the material, can be used for the deformation analysis of a large structure and the fracture mechanics analysis of a component comprising cracks and has important engineering values for promoting the theory development of mechanics, the optimization design of an engineering structure and the material performance evaluation.

The invention discloses a method for measuring the J integration of cracks on the basis of digital-image correlation, belongs to the field of fracture mechanics and engineering application and relates to the method for measuring the J integration of cracks on the basis of digital-image correlation. The method comprises the following steps: by a digital-image correlation technology, measuring and calculating a displacement field and a strain field under different loads on the surface containing crack defects, acquiring information of the displacement field and the strain field, and storing into an Excel; writing an MATLAB program, calling data information in the Excel, carrying out numerical-integration calculation and further obtaining the J integration value of the cracks. The method disclosed by the invention has the advantages that the digital-image correlation, an MATLAB technology and J-integration calculation are combined, the strain of a test piece with the cracks is acquired by the digital-image correlation technology, a calculation result of digital-image correlation is extracted by MATLAB, and numerical integration is calculated; the method has the advantages of high efficiency and strong practicability, is suitable for calculating various test pieces which contain micro-deformation cracks and have elasticity and small-range yield, and is strong in universality.

The invention discloses a ballastless track damage analysis method performing combined solution based on definite element expansion and fatigue analysis. The method includes the following steps that a definite element model of a ballastless track is built; needed loads and boundary conditions are applied to the definite element model, and stress analysis is performed on the definite element model; a stress analysis result is imported into fatigue analysis software, and fatigue performance analysis of the definite element model is performed; based on a definite element expansion method, fracture mechanics parameters of materials of the track structure are defined in the definite element model, service life critical portions obtained during fatigue performance analysis are selected as damaged regions, and generation of damage and a continuous development evolution rule are calculated; a train wheel track coupling model is added on the definite element model, damage is applied to the truck structure, the transverse acceleration, the vertical acceleration, the derailment coefficient and the wheel weigh load reducing rate of a train are calculated after the damage happens to the track structure, and influences of the damage on running of the train are analyzed.

A finite element method for predicting crack opening and propagation entails defining a succession of overlapping interface elements at a potential crack plane, each element having a bound node pair and side node pairs spaced from the bound node pair to sense approach of a crack. An energy-based fracture mechanics criterion determines whether release occurs at the bound nodes and, if so, the displacement between the bound nodes is calculated based on a strain softening law. The process is repeated for each element in sequence.

The invention relates to the field of rock fracture prediction, in particular to a shale hydraulic fracture propagation prediction method. The method comprises the steps that 1, the normal direction,tangential stress and effect stress of an inclined fracture under the action of the external stress and water pressure are calculated; 2, a strain energy density function is obtained according to thetype of the fracture; 3, a strain energy density factor is obtained according to the strain energy density function; 4, the propagation direction and propagation angle of the fracture are judged according to a strain energy density criterion; 5, influences of stratification, natural fractures and the like on the propagation direction of hydraulic fractures are obtained through numerical simulation, so that fracture propagation under the effect of shale hydraulic pressure is predicted. The prediction method is based on fracture mechanics, a hydraulic condition factor is introduced, and the influences of different stratification directions on the propagation direction of the shale hydraulic fractures are obtained by researching the relation between the fracture propagation direction and themagnitude of the hydraulic pressure and utilizing an extended finite element method, so that accurate prediction of hydraulic fracture propagation is achieved, and higher prediction accuracy is obtained.

The invention provides a helicopter moving part service life management method based on digital twinning. The helicopter moving part service life management method comprises the steps of load data collection, structural stress analysis, crack parametric modeling, fracture mechanics simulation, agent model construction of fracture mechanics parameter prediction, probabilistic prediction of crack propagation, structural risk evaluation and dynamic adjustment of a maintenance inspection plan. The invention relates to an electronic device and a storage medium, which are used for executing a helicopter moving part life management method based on digital twinning. According to the invention, multiple scales of the structure are considered and multiple models are fused; and establishing a digitaltwinning body of the typical moving part structure of the helicopter, performing high-performance real-time simulation according to the flight parameters of the helicopter and the load and damage data of the key part of the structure, dynamically updating the damage state of the typical moving part of the helicopter, and adjusting the residual life and the maintenance and inspection plan of the structure.

The invention relates to a test system for the extension of a multi-axis and salt-spray corrosion fatigue crack. The test system comprises a fatigue tester for providing I-type, II-type, III-type and compound fatigue loads required by a test for a test sample through a pull-cut-twist multi-axis loading fixture, and further comprises a salt-spray corrosion environmental box, wherein the salt-spray corrosion environmental box comprises a salt-spray corrosion box body and a salt-spray pre-occurrence box body which are mutually communicated through a pipeline; the salt-spray pre-occurrence box body conveys air and salt water required by salt-spray forming to the salt-spray corrosion box body; the salt-spray corrosion box body provides a required salt-spray corrosion environment for the fatigue crack extension test; both the pull-cut-twist multi-axis loading fixture and the fatigue crack extension test sample are positioned in the salt-spray corrosion box body. Through the adoption of the test system, the fatigue crack extension rate and other fracture mechanics parameters under the combined action of multi-axis loads and the salt-spray corrosion environment can be measured relatively well, and thus the material selection design and the service life evaluation for marine engineering equipment serving in the salt-spray corrosion environment and under a complex stress state can be supported.

The invention discloses a fatigue short crack propagation life prediction method under multi-axis variable amplitude loading, and relates to the multi-axis fatigue strength theory field. The algorithmincludes the following steps: (1) using the Wang-Brown multi-axis cycle counting under stress loading to obtain a plurality of half cycles, and realizing multi-axis constant amplitude loading of eachhalf cycle; (2) using the weighted average maximum shear stress method to determine a weight critical surface for the characteristic that the critical surface is not fixed; (3) obtaining the crack propagation amount of a single variable amplitude load block by using a multi-axis fatigue short crack propagation model on the weight critical surface; and (4), performing plastic zone size correctionon crack tips, and calculating the short crack propagation life by the fracture mechanics method. The method can well describe the influence of multi-axis variable amplitude loading on crack propagation. The results show that the method can predict the short crack propagation life under multi-axis variable amplitude loading.

The invention relates to a life-based design method for the fatigue strength of an ultrahigh-pressure container. The design method comprises the following steps: firstly carrying out primary structure designing; then carrying out an optimal design of self-enhanced treatment according to the principle of minimum shearing stress; then calculating by utilizing finite element software so as to obtain largest local equivalent stress, and comparing with the designed fatigue strength, if the designed fatigue strength is met, calculating the minimum initial fatigue crack length according to a design pressure and a threshold value of fatigue crack propagation of materials; determining the maximum fatigue crack length by utilizing the fracture toughness of the materials and establishing an accurate description equation on the basis of data of a fatigue crack propagation test; and carrying out iterative calculation on the basis, judging whether the fatigue design life is met, if so, finishing the structure design. The design method has the advantages that multiple risk factors in the process of manufacture and operation of the ultrahigh-pressure container are considered and controlled at a design phase, and the fatigue design life is given according to a modern numerical calculation technology; the designing method is safer compared with a conventional elastic-plastic design method and is more accurate and reasonable compared with the existing fracture-mechanics design method.

The invention relates to the technical field of safety assessment of pressure vessels with defects, in particular to a method for determining defects of a multilayer binding vessel by acoustic emission. Acoustic emission detection is carried out according to the structural features of the vessel so as to determine the defects. The method comprises the following steps of: (1) activating defects under overpressure, synchronously monitoring the defects in the vessel by acoustic emission, determining the overpressure during activating the defects and positioning the activated defect parts; (2) simplifying activated defects which cannot be determined by ultrasonic phased array rechecking according to the development direction of an acoustic emission event; (3) obtaining the stress distribution of the simplified defect parts by utilizing finite element calculation or a nomogram obtained on the basis of the finite element calculation so as to ensure that the simplified defects are on a maximum stress wall surface vertical to the simplified defects; and (4) based on defect simplification conditions, the stress of the simplified defect parts and material fracture toughness, reversely reasoning nominal initial sizes and tolerance sizes of the defects according to a fracture mechanics theory. The method has reliable detection means and reasonable simplification process and provides a foundation for the safety assessment of multilayer binding vessels.

The invention relates to a method for constructing non-penetrated jointed rock mass damage constitutive models under a plane compressive shear stress. The method comprises the following steps of: associating additional strain energy increments caused by crack in fracture mechanics with damage mechanics strain energy burst sizes, and importing the additional strain energy increments and the damagemechanics strain energy burst sizes into a non-penetrated crack extension criterion so as to put forward an external force-considered calculation formula for jointed rock mass damage variables; and finally obtaining a crack parameters (internal causes) and stress conditions (external causes)-considered non-penetrated jointed rock mass damage tensor calculation method, so as to establish a corresponding damage constitutive model. According to the method, the condition of considering external force is suitable for influences caused to rock mass damage variables by common stress states (not comprising positive stress and comprising shearing stress, and suitable for single-axis or double-axis stress states only comprising positive stresses), so that the defect that only rock damage variable calculation under double-axis pressure, namely, influences caused by rock damage variables by confining pressure , is considered in variable calculation of rock mass damages caused to cracks by externalforce in the prior art is overcome.

The invention relates to the technical fields of oil reservoir research and oil reservoir classified evaluation, in particular to a method for performing comprehensive classified evaluation on an ultralow-permeability oil reservoir. Relation between a stratum rock compressible coefficient and a crude oil reservoir permeability coefficient is established by analyzing various parameters such as therock fracture mechanics of the ultralow-permeability oil reservoir, the flow characteristic of the crude oil and geological reserve scale. A relation chart between the compressible coefficient of crude oil reservoir rock and the reservoir permeability coefficient of the crude oil under different single-well productivity by statistics of various related parameters of the same kind of oil reservoirdevelopment zone which has finished drilling, and oil reservoir comprehensive evaluation and productivity prediction analysis can be carried out by the chart. Through establishment of the comprehensive classified evaluation chart, basis is provided for rapid zone selection and productivity prediction of the same kind of ultralow-permeability oil reservoir, so that a good guiding function of realizing new zone production and efficient development is achieved. The method has the characteristics of simplicity, practicability and high operability and can be applied to other ultralow-permeability oil reservoir classified evaluation research.

The invention provides a pitch fatigue performance evaluation method based on a fracture mechanic theory. The method comprises the following steps: performing a fatigue test on pitch by use of a dynamic shear rheometer; calculating crack length data and accumulative dissipated energy data based on basic test parameters, and drawing an accumulative dissipated energy-crack length curve; analyzing to determine turning points of changing a crack development slow expansion period into an unstable dynamic expansion period under stress and strain control modes, namely a third turning point of the accumulative dissipated energy-crack length curve; taking loading times corresponding to a crack length at the turning point as pitch fatigue life, thereby finishing evaluation on pitch fatigue performance. The method is capable of evaluating the pitch fatigue performance under the stress and strain control modes, and analyzing and disclosing a pitch fatigue performance damage mechanism from internal structure changes, and has great significance in evaluation on the fatigue performance of a pitch material and pitch material production and application.

Improvements in the aesthetic appearance and performance properties of heterophasic polymers is obtained through the breaking up and dispersion of large gels. According to the current invention, a novel process is provided for filtration of heterophasic polymers using a fiber metal felt (FMF) media. Molded articles made from impact copolymers prepared according to the present invention have improved appearance and fracture mechanics relative to impact copolymers produced according to prior art methods.

The invention discloses a physical and non-physical mixture-based complex scene fluid-solid coupling efficient simulation method. The method comprises the steps of 1) performing incompressible fluid simulation, combining an Euler method and a Lagrange method, and proposing an implicit particle method-based zero-divergence smooth particle fluid dynamics method; 2) performing dynamics problem solving in fluid-solid coupling, subdividing a motion problem of a simulation object into three sub-problems according to object attributes, and solving the three sub-problems by using different methods respectively to realize a multi-dimensional classification combination computing framework; and 3) combining a strain energy density concept in fracture mechanics with Voronoi spatial segmentation to realize a physical perception-based crushing method. The simulation efficiency problem difficult to solve in complex fluid-solid coupling scene simulation is solved. Compared with a conventional fluid-solid coupling method, the method can simulate a fluid scene with richer details under the same system resources, and can meet the demand of simulating solid crushing under fluid impact.

The invention relates to a detection method for the quick estimation based on the inherent frequency of a damaged beam. The method comprises the steps: proposing an estimation formula for estimating the inherent frequency of a structure through the inherent frequency of a good beam structure and a vibration model by employing the Rayleigh quotient during a single damage or multiple damages according to the theory of fracture mechanics; just employing the inherent frequency estimation formula to complete the building of a relation database of the inherent frequency of the damaged beam, the position of the single damage, the positions of the damages and the damage degree, and completing the direct problem solving based on a model; employing an exciting hammer shock excitation modal experiment to obtain the inherent frequency of an actual damaged beam structure as the input, solving the relation database through a back-propagating neural network method, and quantitatively detecting the damage position and degree of the beam structure. The method solves a problem that a conventional damaged beam structure detection method based on a model is complex in calculation of the inherent frequency of the damaged beam structure, quickly gives the relation database of the inherent frequency of the damaged beam, the position of the single damage, the positions of the damages and the damage degree, and brings great convenience to the detection of the damaged beam structure based on the model.

Dynamic segmentation model to divide bottom hole net pressure curve into different stages based on slope of curve includes: step S1, establish calculation model of bottom hole net pressure: according to wellhead pressure during hydraulic fracturing in shale gas reservoir, calculate bottom hole net pressure based on fluid dynamics theory; step S2, establishing dynamic segmentation model to divide bottom hole net pressure curve into different stages based on slope of curve by numerical analysis theory; step S3, establish recognition model to recognize extension behavior of underground fracture network based on rock mechanics and fracture mechanics; and step S4, combine step S1, S2, and S3 to realize automatic diagnosis for wellhead pressure curve of hydraulic fracturing in shale gas horizontal well. A diagnosis and analysis method of the wellhead pressure curve of hydraulic fracturing in shale gas horizontal well is described.

The invention discloses a ceramic based friction material and a preparation method thereof. The ceramic based friction material has improved mechanical properties, fracture mechanical properties, thermal shock stability, stable chemical properties, excellent friction performance and wide field of use, and is composed of the following raw materials: an inorganic macromolecular polymeric binder, a reinforcing material, a friction performance conditioning agent and other materials. With the advantages of high temperature resistance, high pressure resistance and impact resistance, good anti-thermal decay performance, unique function, environmental protection and energy saving, light weight, no harm to a dual equivalent, long service life and strong environmental adaptability, the high performance friction material has a service life increased by over 2 times than that of existing products.

The invention belongs to the technical field of composite material tensile strength prediction, and particularly relates to a method for predicting the tensile strength of a woven ceramic matrix composite material. On the basis of considering the temperature and oxidation influence, a fiber / matrix interface debonding length equation and a fiber slippage length equation are established by adoptinga fracture mechanics method, and a stress distribution equation after matrix cracking and interface debonding damage of the woven ceramic matrix composite is considered; on the basis of total load bearing criterion, by combining the equations, a fiber / matrix interface oxidation area fiber fracture probability equation, a fiber / matrix interface debonding area fiber fracture probability equation anda fiber / matrix interface bonding area fiber fracture probability equation are established respectively, to obtain a fiber fracture probability and stress relation equation. The method is used for predicting the tensile strength of the woven ceramic matrix composite material, and the prediction result is higher in accuracy.

The invention discloses a preparing method of magnesium-base big block non-crystalline material in metallic material technical domain, which comprises the following steps: supplying 33.5-42.4% magnesium, 7.4-27.0% copper, 6.2-13.7% nickel and 33.3-36.5% gadolinium; melting metal gadolinium repeatedly; purifying; allocating metallic copper, gadolinium and nickel with agreed mass percent; melting until the alloy melts evenly; generating nickel-copper-gadolinium alloy cast ingot; bruising; evacuating with Efco-Northrup vacuum furnace; aerating argon gas; melting the bruising alloy cast ingot with magnesium block; melting evenly; getting mother alloy ingot; bruising; adopting eddy-current heating; remelting; getting the product through after-treatment. The compressed fracture dynamic property of this product can reach 900MPa.

The invention relates to a method to extract the coherent gradient sensitive interference fringe level number in fracture mechanics. Wherein, splitting the parallel light beam into two paths to generate coherent gradient sensitive interference fringe respectively; subtracting the background light intensity in two figures of coherent gradient sensitive interference fringe, calculating the fringe level number ml of the first figure. Wherein, the opposite device comprises: a laser, a beam expander, a convex lens, a semi-reflecting semi-transparent mirror, four gratings, two groups convex lens and diaphragms, and two cameras and computers. This invention can improve the calculation accuracy obviously without knowing the opposite load of fringe image.

The invention relates to a straight gear meshing stiffness calculation method considering complex matrix and crack propagation, and the method comprises the steps: obtaining an overall flexibility matrix of a driving wheel and a driven wheel of a meshing gear based on a finite element theory, and determining an overall flexibility matrix of a possible contact point at each meshing position; Introducing a nonlinear Hertz contact theory, and calculating a contact flexibility matrix of possible contact points at each meshing position; And introducing the overall flexibility matrix, the contact flexibility matrix and the initial gap vector of the possible contact point into a deformation coordination equation, and calculating the meshing stiffness of the meshing position. According to the method, crack propagation paths obtained through fracture mechanics can be considered at the same time, and the influence of a complex matrix structure (including a web structure and a lightening hole structure) on the meshing rigidity of the straight gear can be considered at the same time. According to the method, the straight gear meshing stiffness considering the gear web structure, the lighteninghole structure and the crack propagation path can be calculated at the same time. The result of the method is verified by adopting a three-dimensional contact finite element method, and the result shows that the method disclosed by the invention has higher precision for calculating the meshing stiffness of the crack-containing complex matrix gear.

The invention provides a method for analyzing change of force applied to a fractured rock slope along depth under a heavy seismic load. The method comprises: a. establishing a fractured-rock-slope equivalent model, and presetting cracks of different angles in the fractured-rock-slope equivalent model; b. inputting simulated seismic waves into the fractured-rock-slope equivalent model; c. according to a force application result of the fractured-rock-slope equivalent model after the simulated seismic waves are input, acquiring an effect of the cracks on an slope internal force under a seismic load. The invention discloses, from a micro perspective, a mechanism in which a rock slope deforms and breaks under a dynamic load, and proposes a new dynamic rock breaking strength criterion based on fracture mechanics, to help propose a reasonable and economical protecting and retaining system, so as to reduce an impact of a broken slope on a surrounding environment in a disaster. According to an analysis method provided by the invention, a standard slope design method is established, and a perfect research foundation and basis are laid for applications in projects such as landslide control, high and steep slope protection, and so on.

The invention discloses a mold of which the surface is coated with a TiN coat, wherein the surface is coated with a TiN coat, and the three-strong-peak phase of the coat is a TiN phase and also has partial TiO, TiO2 and Ti3O oxide phases. The coat has laminar distribution of dark-and-light phases, and the joint of the laminar structure inside and laminar structure is provided with a small amount of pores. The joint of the coat and base does not have crack or any other microdefect, is well combined. By using ultrasonic plasma to spray the TiN coat, the coat has higher hardness (up to 1210HV0.1), and the high hardness can enhance the wear resistance of the coat; the coat has higher fracture toughness which can enhance the interior fracture mechanical properties of the coat and prolong the fatigue life of the coat.

The invention relates to a test method for the adhesion strength of the intrinsic coating for the expansion resistance of a boundary crack in the detection technical field. A wedge block inserted into a substrate is pushed by external force, so that a coating attached on a common surface of the wedge and the substrate deflects, hence the crack expands in the boundary between the coating and the substrate; by a microscopic observing device, the geometry of the crack is directly observed from the side or surface of the specimen, and the adhesion strength of the coating is calculated by the mechanics of fracture. The test method overcomes the shortcomings of prior test method for adhesion strength of coating such as complex preparation of specimen, pollution of the coating and substrate boundary, and impossibility for observing direct the crack at film-substrate boundary, etc., and provides a simple and rapid way for measuring the adhesion strength of coatings quantitatively.

The invention discloses a method for evaluating the characteristic life of a metal structure of a foundry crane based on track joint defects. Through a rigid body motion dynamics model, an impact coefficient caused by the crane running on a joint track with high and low dislocation and horizontal clearance is calculated; a load spectrum according with engineering practice is compiled; an allowablestress method which is combined with finite element simulation is used for determining the fatigue dangerous section and dangerous point of the metal structure of the foundry crane, and a first principal stress-time history after dangerous point mutation caused by the track defects is obtained; a dual-parameter stress spectrum is extracted by adopting a rain-flow counting method, and combined with a Pairs formula in fracture mechanics, the service life and fatigue residual life of the dangerous point are calculated. Through a life characteristic assessment result, continued use, maintenance or scrapping of the foundry crane are judged, the security problem is solved that parent metal and weld failures are caused by foundry crane metal structure stress-time history mutation due to the carttrack defects, and a theoretical support is provided for the development of the national standard 'scrap conditions for foundry cranes'.