222 results about "Structural fatigue" patented technology

The invention relates to a fatigue life prediction system for a vehicle body structure of a vehicle in the technical field of vehicle design. The prediction system adopts a road spectrum fitting module to establish a combined road spectrum suitable for a field test; a vehicle body loading spectrum acquisition module is adopted to establish an entire vehicle multi-body rigid-flexible coupled model so as to extract the load-time-history at a connecting passage of the vehicle body and a chassis as the input of vehicle body excitation; an automobile body structure dynamic response analysis module is adopted to establish a finite element model of the vehicle body so as to obtain the static stress history generated by gravity and the dynamic stress history generated by road surface excitation of the vehicle body when the vehicle is under the excitation of the combined road spectrum; a dangerous position identifying module of low fatigue life of the vehicle body is adopted to quickly search dangerous positions of low fatigue life through an S-N method and a Miner linear accumulated damage model, and determine the multiaxial stress state of the dangerous positions by using 'biaxiality' analysis; and a fatigue life prediction module of the vehicle body structure is adopted to predict the fatigue lives of the dangerous positions accurately. The fatigue life prediction system for the vehicle body structure can improve the speed and the precision of the fatigue life prediction for the vehicle body structure so as to provide a reference for a real vehicle test.

A method of determining the fatigue life of a structure includes the steps of:associating a mathematical equation for total strain amplitude with the structure:Δɛ2=σf′E(2Nf)b+ɛf′(2Nf)c,where: Δε / 2=strain amplitude, σf′=fatigue strength coefficient associated with a material of the structure, b=fatigue strength exponent of the material, E=cyclic modulus of elasticity of the material, 2Nf=number of cycles, εf′=fatigue ductility coefficient of the material, and c=fatigue ductility exponent of the material;reducing the fatigue strength exponent (b) such that an elastic portion of a total strain amplitude curve associated with the equation has a reduced slope to account for variable amplitude loading for the structure;generating a total strain amplitude curve, based upon the mathematical equation:Δɛ2=σf′E(2Nf)breduced+ɛf′(2Nf)c,where (breduced) is now the reduced fatigue strength exponent; anddetermining a fatigue life of the structure, based on the total strain amplitude curve with the reduced fatigue strength exponent.

The present invention is a system for monitoring, storing, and reporting the accumulation of fatigue occurrences experienced by an aircraft. The system according to the present invention uses existing aircraft instrumentation to monitor fatigue occurrences. Data is collected on the magnitude and cycles of any turbulence encounters; magnitude and number of gloading accrued by aircraft maneuvering; the number of pressurization cycles that the aircraft has experienced; and the number of takeoffs / landing cycles that have occurred. These data are stored in electronic memory for later review by the flight crew or maintenance personnel. Additionally, the number of accumulated wing flap cycles and landing extensions / retractions may also be monitored to facilitate the maintenance operations of these two critical flight controls.

A shore bridge structure wind vibration fatigue life forecasting method based on accumulated damage of probability includes the following steps: step 1 adopting a harmonic superposition method to simulate time domain waveform of wind load borne by a shore bridge structure and according with davenport power spectrum characteristics; step 2 enabling the wind load to be acted on a finite element model of the shore bridge structure, and calculating a stress response time interval of fatigue calculation points of the shore bridge structure; step 3 adopting a rain flow counting process to deal with the stress response time interval so as to obtain fatigue statistical characteristics of amplitude stress spectrum; and step 4 adopting a probability accumulated damage model and a method of a probability theory to forecast wind vibration fatigue life of the shore bridge structure at a certain degree of reliability. The shore bridge structure wind vibration fatigue life forecasting method has the advantages of applying to a complex shore bridge structure, and being wide in scope of application, high in calculating accuracy and capable of calculating reliability fatigue life of a wind resisting structure under the action of any random wind load.

The invention relates to a method for determining allowable defects of a helicopter composite main rotor blade and belongs to the technical field of structural fatigue design of helicopters. The method comprises the following steps: determining forms and easily occurring areas of a defect according to the function and structure of each area of a main rotor blade and process control and other conditions in the manufacturing process; predicting the maximum allowable size of the defect based on the principles such as detection simplicity, statistics and process controllability, and prefabricating on a full-sized test piece; determining the rationality of defect parameters by adopting a test of simulating fatigue and residual strength in a real load environment, determining the defect types in critical prevention and control of the composite main rotor blade, and establishing the defect allowable standard. According to the method, a technical basis can be provided for treatment of the various defects in the production, usage and maintenance processes.

The invention relates to a risk evaluation method for a self-elevating type ocean platform. The risk evaluation method includes steps of structural reliability analysis under extreme load, reliability analysis of structural fatigue, structural reliability analysis of platform piles, risk analysis of ship collision and risk analysis of fire disaster explosion. The risk evaluation method for the self-elevating type ocean platform effectively fills the blank in risk evaluation methods for the self-elevating ocean platform in the prior art, provides technical support for determining and policy making in design and construction stage of ocean engineering, and guarantees safety and reliability of the self-elevating platform to the greatest extent.

A method for determining a dual-layer top cover of a motor coach with a top-positioned gas cylinder comprises topology optimization, initial structure design, section optimization, anti-overturn stability analysis and fatigue analysis. According to the design requirement, the topology optimization design based on conditions such as bearing capability, shape, power distribution and the like is carried out, thus obtaining an initial space structure of the top cover; subsequently, the section optimization is carried out to the initial space structure and the structure improving design is carriedout so that the improved structure meets the low-order vibration performance and static performance on stiffness and strength; subsequently, the anti-overturn analysis and fatigue analysis are carriedout on the improved structure so as to ensure nonoccurrence of gas leakage problem due to damaged gas cylinder under the overturn working condition of the motor coach with top-positioned gas cylinder, ensure the fatigue durability of the structure of the whole coach, and ensure that the top cover of the motor coach with the top-positioned gas cylinder meets the low-order vibration performance, static performance on stiffness and strength and safety and durability under the overturn working condition. The method simplifies the workload, improves the success rate of product development and shortens development period.

A fatigue testing machine for lifetime measurement of cantilever parts comprises a base, a motor, an eccentric mechanism, a loading mechanism and a test piece clamping device. Rotation of the motor is converted into variable amplitude constant-amplitude reciprocating motion by the eccentric mechanism and the loading mechanism. The front end and bottom of a cantilever test piece to be tested are fixed by the test piece clamping device, so that the front end of the cantilever test piece is allowed to fatigue by reciprocating swing. The defect that commercially available instruments are not applicable to structural fatigue lifetime measurement of practical cantilever parts but applicable to material fatigue lifetime measurement of standard parts only is overcome, test conditions that existing commercial products cannot achieve can be achieved, serving actual lifetimes of the cantilever parts are predicted more accurately, and more reliable basis for structural design and modeling of the cantilever parts.

The invention discloses a welding process used for a marine water-jet propulsion chute grate. The process comprises the following steps: firstly, grate components are processed well and the margins are pre-preserved; the actual mounting is carried out to define the actual mounting positions and the final sizes of the components; the components are pre-fixed through spot welding; and after checked and passed, the components are welded in the ship chute to form a complete grate. The proper sequence and process parameters are adopted in the welding so as to reduce the internal stress as much as possible; after welding, the whole grate is demounted to repair welding seams and carry out aging treatment and then the grate is remounted so as to further enhance the strength of the grate and reduce internal stress. The invention can better satisfy the technical requirement and precision requirement of manufacturing, mounting and welding the chute grate so as to avoid the cracks or breaking of grate strips caused by the wearing of the grate structure due to ship vibration.

The invention discloses an equivalence coefficient method of vehicle structure fatigue damage calculation under combined road conditions. The method includes the steps of firstly, testing the stress load of a vehicle structure under selected combined road conditions and compiling a load spectrum; secondly, calculating vehicle damage value under each road condition; thirdly, according to the damage equivalence principle, using one road condition as reference to calculate the equivalence coefficients of vehicle structure damage under other road conditions; fourthly, using the equivalence coefficients to adjust the combined road conditions according to users' needs, and analyzing corresponding vehicle structure damage. The method has the advantages that the method is based on established fatigue load test data, and the equivalence relation of fatigue damage of each road surface can be conveniently and accurately determined during automobile fatigue durability research; mileage recombination can be performed in road tests according to users' application requirements and targets; fatigue damage value of vehicles can be estimated, and comparative analysis of fatigue damage can be performed conveniently.

The invention discloses a method for determining allowable defects of a honeycomb sandwich layer of a helicopter, belongs to the technical field of structural fatigue design of helicopters and particularly relates to a method for determining honeycomb sandwich layer structure defects of a helicopter body with defects. By prearranging internal and external defects on a honeycomb sandwich layer test piece and determining the rationality of defect parameters by adopting static strength, fatigue and remaining strength comparative tests under real load-bearing environments, bases are provided for the design and handling of such manufacturing deviations, the manufacturing and using costs of the honeycomb sandwich layer structure can be decreased and the risk in use of the defective structure is reduced.

The invention relates to a device and a method for testing the structural fatigue of an H-shaped vertical shaft wind turbine blade. The device comprises a support base component, a distribution beam, a loading hoop, a support connecting rod and an eccentric motor, wherein the distribution beam, the loading hoop and the support connecting rod are connected together by using bolts so as to form a whole load distribution system, so that the fatigue load which acts in an upper and lower reciprocation manner can be effectively conducted. When the device is used for experiment, the fatigue bending moment distribution of the blade under various working conditions can be simulated by adjusting the length L of the distribution beam and the position B of the loading hoop, and the fatigue stress state of the blade in axial torsion and multiple attack angles can be simulated by adjusting the structural modes of the support base component and the loading hoop; the strain distribution of the blade under the fatigue loaded condition can be measured, and furthermore, the fatigue structural property of the blade can be evaluated; by only exerting one external fatigue load to the device, combined fatigue loading modes such as bending, torsion and multiple attack angles of the blade can be achieved, and the device is simple and convenient to operate, accurate and reliable in result and relatively high in universality.

The invention discloses a nonlinear ultrasonic mixing method for testing in the structural fatigue crack direction, and belongs to the field of non-destructive testing. The method comprises the following steps: firstly, according to a tested object and a nonlinear ultrasonic mixing harmonic condition, determining the testing parameters such as the mode, frequency, incident angle and the like of two fundamental frequency waves; performing the nonlinear ultrasonic mixing testing of the structural fatigue crack; performing continuous wavelet transformation on testing signals in each annular receiving point, extracting the amplitudes of mixing waves, and performing the mixing sound field directivity analysis; finally, calculating the fatigue crack direction according to the change rule of thereflecting mixing wave propagation direction along with the fatigue crack direction.

The invention belongs to the technical field of crane fatigue data processing, discloses a crane fatigue analysis system and method. The method includes: establishing a crane structure random fatiguelife intelligent evaluation system based on the combination of static testing and random dynamic testing of an operation process; performing crane structure fatigue source positioning and stress correction based on finite element simulation analysis; cyclically including load lower than the fatigue limit in the load spectrum, and evaluating the fatigue life and safety of the structure through thepiecewise linear damage accumulation theory. Experiments, simulation and theoretical analysis are combined, the actual load process and working conditions of the tested crane metal structure can be reflected, the real weak link of the tested crane and the influence of the real weak link on the safety of the metal structure can be reflected, and safe production is guaranteed; crane overhaul and maintenance plans can be reasonably made for use units, and a large amount of manpower and material resources are saved. The disordered production rhythm is avoided as much as possible and the productionefficiency is improved.

The invention belongs to the technical field of seaborne renewable energy utilization, and discloses a novel floating wind energy-wave energy combined electricity generation system. The system is based on a semi-submersible-oscillating water column wave energy integrated electricity generation platform without supporting stand columns, and comprises a seaborne wind electricity device and an oscillating water column wave energy electricity generation device. By means of the wave energy electricity generation device, vertical reciprocating motion of a water column is converted into reciprocating motion of a gas, and then electricity generation of wave energy is completed through an air turbine generator. According to the system, a bottom floating box and anchor chains of the semi-submersible platform are fully utilized; as the wave energy electricity generation device vertically moves with waves, the electricity generation efficiency is reduced, and the floating box can slow down vertical vibration; the anchor chains can further prevent the wave energy electricity generation device from vertically moving. According to the system, the structure of the supporting stand columns is not used, the construction process is simplified, and the problem of structural fatigue produced by the supporting stand columns is avoided. Compared with a traditional three-stand column semi-submersible blower, the waterplane area of the system is increased, thus steady moment of inertia is large, and the whole stability of a floating basis is improved.

A shore bridge structure wind vibration fatigue reliability forecasting method based on probability accumulated damage comprises the following steps of 1 adopting a harmonic superposition method to simulate wind load time domain wave forms endured by a shore bridge structure and accorded with Davenport power spectrum characteristics; 2 enabling the wind load to act on a finite element model of the shore bridge structure and calculating a stress response time interval of a fatigued calculation point of the shore bridge structure; 3 adopting a rain flow counting method to process the stress response time interval so as to obtain the fatigue statistics characteristics of amplitude stress spectral; and 4 adopting a probability theory method to forecast the wind vibration fatigue reliability of the shore bridge structure in a certain serving period through a probability accumulated damage model. The shore bridge structure wind vibration fatigue reliability forecasting method has the advantages of being applicable to the complex shore bridge structure, wide in application scope, high in computational accuracy, and capable of calculating the fatigue reliability of a wind resisting structure under any random wind load effects.

The invention discloses a normalization method for fatigue characteristics of an asphalt mixture under different stress states. The strength yield surface of the asphalt mixture based on a yield criterion is established by combining strength and fatigue test at different loading speeds under different stress states with a Desai strength yield surface model, a fatigue characteristic analysis technology based on the yield criterion is provided, and a normalization model for the fatigue characteristics of the asphalt mixture in different stress states is obtained. The fatigue characteristic analysis technology and the normalization model can be used to eliminate a difference between the fatigue test results of the asphalt mixture under different test conditions and make up for the deficiencyof no accurate evaluation of the fatigue performances of the asphalt mixture in traditional S-N fatigue equation; and the method realizes the unified expression of the fatigue performances of the asphalt mixture under different test conditions, and provides a theoretical, technologic and technical basis for realizing the scientific transformation from material fatigue to structural fatigue.

The invention discloses an automobile headlamp structure fatigue life analysis method. The method comprises the steps that 1a, road spectrum data are collected and corrected; 1b, corrected road spectrums are simplified and calibrated; 2, environment temperatures in winter and summer are simulated respectively, and internal temperatures on the turn-on condition and the turn-off condition of a headlamp are simulated to obtain headlamp temperature field data on four conditions; the time scale between turn-on condition and turn-off condition of the headlamp is determined according to a market survey result, and temperature field combination data are established; 3, a headlamp assembly finite element model is established, thermo-physical properties and mechanical properties of all parts are input into the headlamp assembly finite element model, contact relations and assembly relations between all structures are defined, the temperature field combination data are imported, road spectrum simulation is applied, the thermo-mechanical coupling stress strain response of an automobile headlamp assembly structure within one cycle is calculated, and the thermo-mechanical fatigue life of the headlamp is calculated through fatigue analysis software. By means of the method, the fatigue life of the headlamp can be predicted at the design stage.

A method of assembling a lock and dam system is disclosed to minimize the rate of structural fatigue associated with closing of the lock and dam system. The lock and dam system includes one or more gates that may include a plurality of girders, plates and associated support or reinforcing members. The gate has a miter end and a quoin end. On the miter end a miter block, and thrust plate transfer impact forces associated with closing of the gate from the point of impact to the remainder of the gate. The thrust plate is preferably a substantially uniformly thick member that is secured vertically to the gate through a slot cut or formed in the end of the horizontal plate on the miter and quoin end. Preferably, the thrust plate is secured using a fillet weld.

The invention discloses a simultaneous monitoring method for welded steel truss structure fatigue failure process. The method comprises the following steps: step 1, damageable parts under structural material levels are confirmed through building a finite element model of a welded steel structure and conducting static analysis; step 2, feature response parameters of the damageable parts under each structural material level are confirmed and a corresponding testing scheme is set; step 3, a sensor location project and positions under each structural material level are confirmed, and measures of installing, debugging, noise reduction arrangement and disturbance releasing are finished; and step 4, fatigue loading is exerted to a structure, and welded steel truss materials, components, the failure process under the structural levels, the feature response and the evolution process with a fatigue cycle are monitored simultaneously through a plurality of testing technical means. Compared with a traditional and common structure failure assessment method, the simultaneous monitoring method is capable of reflecting the whole failure process of the structure and the feature response of each level comprehensively, and is beneficial for understanding and researching the failure process and failure mechanism of the structure.

The invention relates to the field of aircraft structure corrosion fatigue, in particular to a method for establishing a structure fatigue life pre-corrosion influence coefficient curve of an aircraft, which can solve the problem of an inaccurate structure fatigue life pre-corrosion influence coefficient curve established with an existing method. The method for establishing the structure fatigue life pre-corrosion influence coefficient curve of the aircraft comprises the following steps: designing a simulated test part of a fatigue key part structure; constructing a lab accelerated environment spectrum and an equivalent accelerated relationship for the simulated test part; setting environment test time of the simulated test part; performing an environment test on the simulated test part, then performing a fatigue test, and recording the fatigue life; obtaining a ground parking corrosion correction coefficient of the simulated test part; and finally obtaining an accurate structure fatigue life pre-corrosion influence coefficient curve of the simulated test part.

The invention relates to an energy conversion device, in particular to a rotating wheel non-contact excitation type fluid kinetic energy conversion device. The device solves the problems that an existing fluid kinetic energy conversion device cannot easily adapt to a complex fluid environment, and is complex in mechanical structure, low in energy harvesting efficiency, hard to become micro or portable, prone to structural fatigue failure and short in service life. The device comprises a rotating wheel, two fixing bases, two rotating shafts, 2N excited magnet pieces and 2N excitation magnet pieces. The rotating wheel comprises a supporting shaft frame and N wheel plates. Each fixing base comprises a cylindrical housing, a hubbed flange base and N piezoelectric composite cantilever beams. Each piezoelectric composite cantilever beam comprises an elastic metal plate and two piezoelectric ceramic plates. The cylinder wall of the cylindrical housing and the base plate of the hubbed flange base of each fixing base are connected into a whole. The rotating wheel non-contact excitation type fluid kinetic energy conversion device is used in the field of new energy power generation.

The invention discloses a method for identifying a key structural fatigue component, wherein a united framework which can contain different fatigue accumulation theories is provided, i.e. the effective stress amplitude is provided and serves as an identification standard for judging the key structural fatigue component. The method comprises steps: 1, traversing all the components, selecting representative standard samples from a strain database acquired from health monitoring, and converting the standard samples to a hot spot stress time interval according to the hot pot stress analysis results of the components; 2, carrying out operations such as preprocessing and rainwater metering on the hot spot stress time interval so as to obtain the extracted stress amplitude sequence; and 3, computing the effective stress amplitudes of all the components, and setting the component with the relatively large value as the key fatigue component. By utilizing the method, the problem of relating variable amplitude fatigue to constant amplitude fatigue is solved, the component with quick fatigue accumulation speed can be conveniently found out on the basis of the strain data which is obtained by a structural health testing system, and accordingly, the key fatigue component is identified.

The invention discloses a method for characterizing the a fatigue damage state of a prestressed concrete beam. The method comprises the following steps that initial dynamic parameters of the prestressed concrete beam are determined, and a first-time static load test is conducted; in the fatigue loading process, a static load test and power testing are conducted on the prestressed concrete beam; vibration modal parameters of the prestressed concrete beam are analyzed; and the fatigue damage state of the prestressed concrete beam is evaluated. The invention further discloses a measuring device for realizing the method. According to the method, power testing is carried out in the structural fatigue testing process of the prestressed concrete beam structural fatigue testing process, the fatigue damage position and the damage degree of the prestressed concrete beam are analyzed based on the vibration modal parameters, thus the fatigue damage state of the prestressed concrete beam is characterized based on the modal parameters, and a new idea is provided for study and testing of fatigue performance of the prestressed concrete beam.

The invention belongs to the technical field of fatigue tests and relates to a construction method of an equivalent analysis spectrum of a fatigue cracking structure. The construction method is based on field data and accordingly the field reality can be reflected by the obtained equivalent analysis spectrum of the fatigue cracking structure. The spectral pattern is a uniform amplitude spectrum and accordingly the equivalent analysis spectrum can be applied to the improvement analysis and a contrast test without simplifying work of a load spectrum, the effectiveness of the improved scheme can be determined, and accordingly the test circle of a test can be significantly shortened. According to the construction method of the equivalent analysis spectrum of the fatigue cracking structure, the problem that structure fatigue load spectrum data are not complete or too complicated in field fatigue crack troubleshooting is solved.

A testing system for testing fatigue performance of a helicopter main-rotor crossbeam is composed of a helicopter main-rotor crossbeam root test-piece, a process joint, a loading joint, a testing stand, a vibration exciter, a motor, an electric control cabinet, a hydraulic system, a hydraulic control cabinet, strain gages, a dynamic strain meter and a light-beam oscillograph. One end of the helicopter main-rotor crossbeam test-piece is installed on the process joint which is installed on the testing stand. The other end of the helicopter main-rotor crossbeam test-piece is installed on the loading joint. The vibration exciter and the loading joint are connected together and are installed on the testing stand. The motor is connected with the vibration exciter and the electric control cabinet. The hydraulic system is connected with the loading joint and the hydraulic control cabinet. The strain gages are adhered to corresponding positions of the helicopter main-rotor crossbeam test-piece. The dynamic strain meter is connected with the strain gages. The light-beam oscillograph is connected with the dynamic strain meter. The testing system has a simple structure, is convenient to operate and is used for testing fatigue performance of a helicopter main-rotor crossbeam. And a test result has important engineering application value for evaluation of structure fatigue life.

The invention discloses a mixed uncertainty structure fatigue life analysis method based on chaotic polynomial expansion. In the method, firstly, a structural fatigue life is expanded into a chaotic polynomial series form based on a Hermite polynomial, a random variable is contained in the Hermite polynomial, and an interval variable is contained in a polynomial coefficient; wherein the coefficient in the polynomial can be solved by using a sample method and a least square method, the sample point of the random variable is solved by using a sparse Clenshaw-Curtis point collocation method, andthe sample point of the interval variable is solved by using a Latin hypercube method. After the polynomial coefficient is determined, the response surface model of the structural fatigue life is constructed, and the mean value and variance of the structural fatigue life can be calculated on the basis. According to the method, under the condition that the precision of the calculation result is guaranteed, the number of samples required for analyzing the fatigue life of the hybrid uncertainty structure is reduced, the analysis efficiency is improved, and a new thought is provided for structuralfatigue reliability design.

The invention discloses a fatigue life prediction method for a CFRP-metal mixed bolt connection structure under competition failure. The method comprises the following steps: (1) predicting the fatigue life of the CFRP plate by adopting an improved progressive fatigue damage model; establishing a three-dimensional finite element model of the connection structure for stress analysis; calculating the mechanical property of the composite material which is gradually degraded under the fatigue load, checking the failure state of the composite material containing damage by applying the extended maximum strain criterion, carrying out rigidity degradation on the failed material, and finally obtaining the fatigue life of the CFRP plate according to the residual strength when the structure fails. (2) predicting a theoretical value of the fatigue life of the metal plate by adopting a nominal stress method; and (3) comparing the predicted fatigue life value of the CFRP laminated plate with the fatigue life value of the metal plate, and predicting the fatigue life and failure mode of the hybrid connection structure under the competitive failure. The method is suitable for engineering application, the fatigue life of the CFRP-metal mixed bolt connecting structure can be effectively predicted, and reference is provided for engineering practice.

The invention discloses a determination method for a steel bridge structure detail S-N curve considering welding residual stress. The method includes the following steps that the welding residual stress of steel bridge structure details is acquired through a thermal-structural coupling analysis method; the influences of mean stress on structure fatigue strength are considered through a Goodman formula, and a material S-N curve correction formula considering the welding residual stress is derived; the fatigue life of structure detail weld toes under different stress level fatigue loads is calculated according to the material S-N curve considering the welding residual stress, the corresponding relationship between structure detail nominal stress and the fatigue life of the weld toes is established, and the steel bridge structure detail S-N curve considering the welding residual stress is acquired. The influences of welding residual stress specific values on steel bridge structure detail fatigue characteristics are considered, the anti-fatigue design of a steel bridge is safer, and traditional full-size or reduced-scale fatigue model tests consuming a large quantity of manpower, material resources and financial resources are avoided.