1614 results about "Fatigue damage" patented technology

The invention relates to a material fatigue-life predicting method based on a support vector machine, and discloses a method for predicting the fatigue service life of a structural material, which comprises the steps of: obtaining material fatigue performance data, selecting a proper input and output parameter to construct a training sample set, establishing a fatigue-life predicting model based on the support vector machine, preprocessing a fatigue load, and calculating the fatigue life. The material fatigue-life predicting method has the advantages of realizing the nonlinear accumulation of fatigue damages by using less material fatigue performance data, and improving the accuracy of predicting the life. The method provided by the invention is suitable for the structural material fatigue life estimation and the life prolonging analysis, and has an important theoretical significance and an actual application value in formulating a reasonable maintenance plan for prolonging the service life of the material.

The invention provides a forecasting method for creep-fatigue life of a material. The method comprises the following steps: respectively performing a creep test, a fatigue test and a creep-fatigue interaction test for the material at a same test temperature; establishing a relation between the failure strain energy density wf and a non-elastic strain energy density dissipation rate of the material under a log-log coordinate according to the creep test; acquiring the fatigue damage df of the material per period according to the fatigue test; acquiring a hysteresis loop under a half-life period according to the creep-fatigue interaction test and establishing a function relation of the change of the stress Sigma (t) of the material under the half-life period within the maximum tensile strain maintaining time along with the change of time t; calculating the creep damage dc under the half-life period by combining with the hysteresis loop and based on the relation between wf and the function as shown in the specification and the relation of change of the fatigue damage df and the stress Sigma (t) along with the change of time t; and utilizing a linear accumulating damage rule to forecast the creep-fatigue life of the material under a creep-fatigue interaction. According to the method provided by the invention, the life of the material under the creep-fatigue interaction can be accurately forecasted.

The invention relates to a device and a method for a multi-axis fretting fatigue test of a steel wire. The device comprises a base frame, a pull-torsion fatigue system, a swing loading system and a condition monitoring system, wherein the base frame comprises a base, support stand columns, bearing beams and support fixture blocks, the support stand columns are symmetrically arranged on the base; the bearing beams are respectively arranged on the tops of the support stand columns; the support fixture blocks are respectively arranged in the middle parts of the support stand columns; the pull-torsion fatigue system comprises a support system, a torsion driving system and a pull-pull fatigue system; the swing loading system comprises a swing driving system and a loading system; the condition monitoring system comprises a fretting measurement system, an axial fatigue load measurement system, a torsion measurement system and a swing measurement system. The torsion angle of the fatigue steel wire can be obtained through a crank-link mechanism by adjusting the eccentric position of an eccentric block; the multi-axis fretting fatigue test of the steel wire can be realized in the composite motion modes such as pull-pull fatigue, torsion and variable crossing angle swing and the like; the device and the method are used for disclosing the multi-axis fretting fatigue fracture mechanism of the steel wire, and carrying out quantitative evaluation on multi-axis fretting fatigue damage evolution and multi-axis fretting fatigue life of the steel wire.

The invention relates to a low-cycle creep and fatigue life evaluation method under the conditions of high temperature and multiaxial spectrum load. The method comprises the following steps of reading a stress strain history in a multiaxial loading spectrum data block, working out equivalent strain, and finishing a loading history; repeatedly extracting by adopting a relative equivalent strain multi-axis counting method; working out all repeated fatigue damage by adopting a unified multiaxial fatigue damage life prediction model; accumulating the fatigue damage to work out the total fatigue damage; working out equivalent creep stress by utilizing the original loading history; working out creep damage Dc according to the equivalent creep stress and the stress history by combining a creep lasting equation; working out the total damage D caused by a multiaxial load spectrum block at the high temperature; and estimating the multiaxial creep and fatigue life. According to the method, the fatigue damage under the multiaxial stress and the creep damage under the multiaxial stress can be respectively calculated in the whole loading spectrum data block, the fatigue material constant at the room temperature is adopted in the calculation of the fatigue damage, and lasting equation material constant recommended by specification is adopted in the calculation of the creep damage; through experimental verification, the method has a good prediction effect.

Fatigue damage resistant metal or metal alloy wires have a submicron-scale or nanograin microstructure that demonstrates improved fatigue damage resistance properties, and methods for manufacturing such wires. The present method may be used to form a wire having a nanograin microstructure characterized by a mean grain size that is 500 nm or less, in which the wire demonstrates improved fatigue damage resistance. Wire manufactured in accordance with the present process may show improvement in one or more other material properties, such as ultimate strength, unloading plateau strength, permanent set, ductility, and recoverable strain, for example. Wire manufactured in accordance with the present process is suitable for use in a medical device, or other high end application.

A method for the non-linear ultrasonic online detection of early fatigue damage to a metal material belongs to the field of nondestructive detection. The method comprises the following steps: determining an excitation signal parameter according to the thickness of a tested piece and inputting the parameter to an arbitrary function generator to generate a sound signal; determining a threshold value of an acoustic emission instrument according to the amplitude of a no-load noise signal; performing fatigue loading on the tested piece, continuously detecting an acoustic emission signal in real time with an acoustic emission sensor, amplifying the acoustic emission signal, inputting the acoustic emission signal into the acoustic emission instrument, and judging ring with the acoustic emission instrument when the amplitude of the acoustic emission signal exceeds the preset the threshold value of the acoustic emission instrument; detecting a non-linear ultrasonic signal at equal time interval if the acoustic emission instrument does not display the ring or the times of the continuous ring is not more than an empirical value; and stopping detection if the displayed ring times is more than the empirical value, because fatigue cracks are generated and develop. On the basis of non-linear ultrasonic nondestructive detection, the method of the invention introduces acoustic emission technique, so the method does not make incorrect judgment when detecting the early fatigue damage to the metal material and realizes continuous online detection.

The invention discloses a bridge fatigue damage state and residual life evaluating method which is used for evaluating fatigue damage states of a bridge on the basis of acquired strain data of a large-span bridge health testing system and estimating the residual life of the bridge through prognostic estimation. The bridge fatigue damage state and residual life evaluating method includes mutually linked steps of P1) analysis of bridge structure; P2) evaluation of the current damage state of the bridge; P3) prognostic estimation of the bridge damages; P4) evaluation of the residual life of the bridge, wherein the fatigue damage state obtained in the P2) and the residual fatigue life obtained in the P4) are evaluation results. The bridge fatigue damage state and residual life evaluating method can regularly evaluate and update the fatigue damage states of the bridge and simultaneously estimates the residual life of the bridge in the bridge operating environment, and provide reference for decision making of bridge operators. Furthermore, the evaluation results are beneficial for verification and correction design requirements.

The invention relates to a damage calculation method for low-cycle fatigue and high-strength impact coupling based on a local stress strain method. The damage calculation method comprises the following steps of: (1) analyzing a fatigue load spectrum, calculating nominal stress strain of each stage of multiple stages of amplitude-variable fatigue load spectra, and converting the nominal stress strain into local stress strain; (2) calculating fatigue life and damage corresponding to each stage of fatigue load local strain when a product is impacted; (3) calculating the fatigue life and the damage corresponding to each stage of the fatigue load local strain when the product is impacted and the impact is in an influence range, and considering the damage probability in a fatigue circulation unit when the product is impacted; (4) calculating impact performance influenced by fatigue accumulated damage; and (5) calculating comprehensive degree of reliability. Compared with a conventional fatigue damage calculation method, the damage calculation method has the advantages that the influence of high-strength impact on the fatigue damage, the influence of fracture failure caused by direct impact to the life of the product and the influence of the fatigue accumulated damage to the shock resistance of the product are considered, and the fatigue-impact life and the degree of reliability of the product can be well evaluated under a complex environment.

The invention discloses a service life based high-temperature container creep fatigue strength design method. The method comprises the steps of 1, performing structure preliminary design; 2 determining load and temperature conditions and the design service life requirement; 3, determining dangerous sections; 4, calculating the equivalent stress and strain range; 5, calculating reference stress; 6, determining whether plastic collapse occurs; 7 determining whether the plastic ratchet occur; 8, determining whether creep damage is important; 9, estimating fatigue damage of each cycle when the creep damage is not important; 10, determining whether the fatigue damage is important; 11, estimating the creep damage when the fatigue damage is not important; 12, estimating damage of each cycle when the creep damage and the fatigue damage are non-ignorable; 13, estimating creep-fatigue total damage; 14, performing result analysis and structural design improvement; 15, completing structural design. According to the method, the foundation is laid for national establishing of creep and fatigue failure mode based high-temperature pressure container design standards and achieving design and manufacture of high-temperature pressure containers according to the service life.

The invention relates to an asphalt mixture life prediction method considering a fatigue-creep interaction damage effect, and belongs to the field of road engineering. The method comprises the following steps: (1) determining a complex modulus of an asphalt mixture under the action of a period load; (2) determining a damage variable of the asphalt mixture; (3) building a creep damage equation and a fatigue damage equation of the asphalt mixture respectively; (4) building an asphalt mixture life prediction model under the combined action of creep damage and fatigue damage. Compared with a conventional asphalt mixture life prediction method, the viscoelastic behavior of the asphalt mixture is considered and a more accurate prediction model is built. The method accurately describes asphalt mixture damage failure process and rule, has the advantages of wide application range and reliable calculation results, and provides a more reliable method for structural design of an asphalt pavement.

The invention provides a pearlite steel rail of high internal hardness type which is excellent in both wear resistance and fatigue failure resistance and a process suitable for the production of the rail. Specifically, a pearlite steel rail which has a composition containing by mass C: 0.73 to 0.85%, Si: 0.5 to 0.75%, Mn: 0.3 to 1.0%, P: 0.035% or below, S: 0.0005 to 0.012% and Cr: 0.2 to 1.3% with the balance consisting of Fe and unavoidable impurities and having a ¢%Mn!/¢%Cr! ratio of 0.3 or above and below 1.0 (wherein ¢%Mn! is Mn content and ¢%Cr! is Cr content) and whose railhead exhibitsan internal hardness of Hv380 or above and below Hv480 in terms of Vickers hardness (Hv)in a depth range of at least 25mm from the railhead surface.

A fatigue life management system for determining a remaining fatigue life of a component of an aircraft. The fatigue life management system may generate probability density functions of minimum load, maximum load, and timeframe damage for predetermined time intervals based on selected flight data of the aircraft and regression models for probabilistic prediction of minimum load, maximum load, and timeframe damage of the component. The fatigue life management system may further compute an accumulated fatigue damage estimation based on the probability density functions and a probabilistic fatigue strength model. The fatigue life management system may then generate a distribution of the accumulated fatigue damage estimation of the component. If desired, the processing circuit may compare the distribution of the accumulated fatigue damage estimation with a reliability requirement to determine the remaining fatigue life of the component.

The invention relates to a fretting fatigue testing method allowing a contact load to be adjusted in real time and a testing machine adopting the fretting fatigue testing method. The testing machine comprises an electronic-hydraulic servo fatigue testing machine, fretting supporting platforms, a fretting device and a computer testing and controlling system, wherein the fretting supporting platforms are fixed on supporting stand columns of the fatigue testing machine; the fretting device is horizontally arranged on the fretting supporting platform; the fatigue testing machine comprises an upper clamp and a lower clamp which are used for fixing a test piece; a contact load sensor, a motor drive signal and a displacement signal of the fretting device are connected with a computer data acquisition control system. Two fretting pad clamps are fixed in middles of two lead screw cross beams, and two opposite fretting pads are mounted at two ends of each fretting pad clamp. A fretting fatigue test with the contact load changing in real time is performed through the fretting fatigue testing machine, influences of the contact load on fretting fatigue damage are researched, meanwhile, fretting fatigue tests at different amplitudes and frequencies can be researched, and an experiment method is provided for deeper understanding of a fretting fatigue damage mechanism.

The invention discloses a test method for the fatigue damage and the service life of a horizontal axis wind turbine blade, aiming to obtain a more exact blade fatigue performance parameter by adopting a test detection and computational analysis means having low cost and high efficiency so as to meet the requirements of blade design, research and development and detection. The method is characterized in that on the basis of the characteristic that the impeller speed of a horizontal axis wind turbine is lower, and the period change frequency of various fatigue loads is also lower, a series of steps of carrying out static loading testing on the wind turbine blade to obtain a stress/strain amplitude distribution condition under the effect of various fatigue loads and analyzing by combining a material property curve and a cumulative damage theory are adopted to realize the evaluation to the blade fatigue performance. Compared with the traditional horizontal axis wind turbine blade fatigue testing technology, the method has the advantages of short period, low cost, capability of obtaining a final service life parameter of the blade, and the like.

The present invention provides a multiaxial short crack propagation life prediction method based on a critical surface method, and relates to the field of multiaxial fatigue strength theory. The algorithm comprises the steps of: (1) selecting a plane, which contains the maximum shearing strain range, as a critical surface, and using the damage parameters on the critical surface to characterize a short crack propagation driving force; (2) based on the shear-type multiaxial fatigue damage parameters, establishing an equivalent crack stress intensity factor applicable to the multiaxial stress state; (3) fitting the short crack propagation rate data under uniaxial loading to obtain an uniaxial short crack propagation curve; and (4) carrying out plastic zone size correction on the crack tip, and calculating the short crack propagation life by a fracture mechanics method. The method can well descript the influence of non-proportional loading on crack propagation. The results show that the method can well predict the short crack propagation life under multiaxial proportional and non-proportional loading.

The invention provides a fatigue analysis method and a fatigue analysis device of a structural member in a wind generating set. The method comprises the following steps: establishing a finite element model for a to-be-measured structural member involving bearing connection and related structural members thereof; applying load to the finite element model according to various preset load working conditions respectively; acquiring each node stress result of the to-be-measured structural member under each load working condition through finite element analysis; scaling down the acquired stress results by taking a fatigue load sequence which is pretreated through regularization as a coefficient; synthesizing the stress results under the different load components after scaling down to obtain a stress spectrum of each node of the finite element model of the to-be-measured structural member; calculating a fatigue damage value of the to-be-measured structural member according to the stress spectrum of each node and the stress-life curve of the to-be-measured structural member. By applying the method and the device, the fatigue analysis result of the structural member in the wind generating set is more accurate.

The invention discloses a low-temperature fatigue property characterization and life estimation method. The method comprises three major steps of step 1, through considering the influence of a stress ratio, deriving an S-N-R curved surface characterizing the fatigue property by adopting a Goodman equilife curve based on a three-parameter power function expression, and performing data processing by virtue of a linear regression theory; step 2, through considering an interaction effect of loads under spectrum loading, proposing a corrected spectrum loading fatigue life estimation model based on a Willenborg/Chang model and a crack tip plastic zone theory, and giving out a fatigue damage increment representation method; and step 3, calculating the low-temperature spectrum loading fatigue life of a material by adopting an accumulative damage theory. The method is simple and practical; and a low-temperature fatigue property characterization model can be constructed only by a constant-load fatigue property curved surface and an actually measured flight load spectrum of the material in a low-temperature environment, and the spectrum loading fatigue life is estimated, so that the method has important academic meanings and engineering application values.

An object is to suppress reduction of energy production as much as possible while ensuring an expected lifetime. There is provided a device of adjusting a curtailment strategy for a wind turbine, the device including: a fatigue equivalent load calculation unit that calculates a fatigue equivalent load for evaluating a fatigue damage of the wind turbine in a predetermined time period by using load data of the wind turbine; and a setting value update unit that compares the fatigue equivalent load with a reference load determined by an expected lifetime of the wind turbine, and, when a difference between the fatigue equivalent load and the reference load exceeds a predetermined threshold value, updates the condition setting value for the curtailment that is currently employed according to the difference.

Threaded connections are provided with a thread form that permits the construction of enlarged root radii between adjacent threads. Relatively coarse thread leads formed along conical surfaces with relatively extended tapers cooperate with relatively tall thread heights and an enlarged root radius (or radii) to produce a fatigue resistant, rotary-shouldered connection that can be assembled with reasonably attainable high torque forces. The ratios between the thread lead, measured in threads per inch, as the numerator, and denominators comprising the untruncated thread height of the thread, and/or the root truncation and/or the root radius (or radii) are maintained at low values compared to those existing in conventional prior art connections. The ratio of the untruncated thread height to the root radius (or radii) is also retained at a relatively low value as compared to that existing in many prior art configurations. The connection design produces an unexpectedly high resistance to fatigue damage or failure. The connection may be employed in any rotary-shouldered connection and is particularly effective in preventing fatigue damage in the stiffer components of drill stem assemblies including single shoulder and double shoulder drill collar connections.

The invention relates to a turbine rotor blade accelerated life test load design method taking regard of flight damage. The method includes: 1) conducting frequency mixing treatment and rain flow counting on aeroengine flight missions and training subjects to acquire the frequency and time of each rotation speed cycle in actual flight, thus obtaining the load basic data of an engine within certain flight hours; 2) acquiring the temperature field and stress strain distribution of the blade under all states by finite element method, analyzing the blade static strength and endurance, and determining a lifetime testing part of the blade; 3) calculating the fatigue damage and creep damage of the blade testing part under a true flight load to acquire a ratio of creep damage and fatigue damage during rise and fall of a flight; and 4) designing a accelerated life test load spectrum of a full-size blade, and determining a conversion coefficient of the blade test load spectrum relative to out-field flight. The method provided by the invention can be used for acquiring the technical life of the blade and studying the remaining life of the blade, and saves time and economic cost for the fatigue-creep lifetime test of the blade.

The invention discloses a transmission gear fatigue life assessment method based on defect modeling. The method includes the following steps that (1), crack occurrence rules and reasonable crack forms are analyzed, and the method for introducing cracks into a gear model is researched; (2), material fatigue characteristic parameters are obtained through test data fitting or a numerical value estimation method; (3), a stress spectrum under the condition of working situations of a gear containing the cracks is calculated by using a finite element method, and the stress spectrum is corrected according to obtaining conditions of the material fatigue characteristic parameters; (4), fatigue life under the condition of working situations of a gear containing the cracks is calculated by using the reasonable fatigue damage accumulation theory. The fatigue life assessment method based on defect modeling is provided for the transmission gear, and an effective detection basis is provided for the remanufacturing process of a gear recycled part.

The invention discloses a life prediction method used for a nickel-base superalloy blade under a thermal mechanical fatigue load. The problems of life prediction and joint representation of low cyclefatigue damage, creep damage and oxidation environment damage of the nickel-base superalloy blade under the TMF load are effectively solved; according to isothermal low cycle fatigue life data of nickel-base alloy under the condition of not causing high-temperature effects of creep, oxidation and the like, fitting is performed to obtain a strain life equation; in combination with a fatigue damagelinear accumulation theory, a fatigue damage model is obtained; a creep damage model is represented as temperature, stress and time functions; the oxidation environment damage is modeled based on an oxidation-cracking mechanism with a continuous oxidation layer at a crack tip; a continuous damage accumulation mechanism is adopted for the three models; and by virtue of stress, strain and temperature data of dangerous position points of the blade, accurate and reliable unified representation of fatigue, creep and oxidation interactive damage, and life prediction of a combined damage model to a nickel-base superalloy member under the thermal mechanical fatigue load is realized.