83 results about "Creep fatigue" patented technology

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 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 on-line safety evaluation method for water-cooled walls. The method comprises the following steps: arranging a small amount of test points in the pipeline section with typical flow heat transfer in each radiation zone, combining with the existing test points at the entrance and exit outside the furnace, calculating and checking the characteristic parameters of the inner wall of the water-cooled wall of the station boiler, inputting to a computer for calculation, performing the on-line real-time calculation of the Parameters such as pipeline flow, entrance and exit pressures, enthalpy value, lengthwise furnace inner wall temperature of each pipeline section and stress change value, to judge whether the dangerous factors exist, such as hydrodynamic instability, over-temperature and creep fatigue, displaying the calculation results in real time, recording the data as judgment basis of safe operation of the water-cooled wall. The invention realizes the optimal operation of equipment, manages the repair and maintenance based on the operational state, and ensures the state maintenance and repair of equipment.

A high-temperature creep fatigue test system, which consists of a fatigue testing machine, specimen holders, a high temperature furnace, a sample, a high temperature extensometer, a cooler and host computer. Upper and lower specimen holders are in threaded connection to ensure the uniform axial loading of the specimen; the specimen holders are connected to the fatigue testing machine; the high-temperature extensometer is connected with the specimen through a jaw; a high temperature furnace mounted on the fatigue testing machine moves to a corresponding position, and wraps the specimen inside; the cooler through inlet and outlet pipes is respectively connected to the upper and lower specimen holders; the fatigue testing machine and the high-temperature extensometer are connected to the host computer; the host computer by reading real-time measurement strain of the high-temperature extensometer controls the fatigue testing machine, so as to conduct strain-controlled high-temperature creep fatigue test. The present invention has the beneficial effects that deformation of the material in high-temperature creep fatigue test can be measured, and has the characteristics of easy operation and high measurement accuracy.

The invention relates to a creep deformation-fatigue crack growth testing device and a corresponding testing method. The device comprises a loading system, a temperature control system and a measurement and collection system, wherein the measurement and collection system comprises a load linear displacement measurement system and a crack length measurement system; the upper and lower ends of a test sample are fixedly connected with an upper clamp and a lower clamp respectively; a high temperature furnace is connected with the temperature control system and the measurement and collection system; the test sample is loaded by an alternating current servo motor and a controller. The invention further relates to the corresponding testing method. The testing device provided by the invention is compact in structure and convenient to operate; the testing device adopts an insulating chuck and the insulating chuck ensures that constant-current current passing through the test sample is stable; aiming at the test sample of a creep deformation-fatigue crack growth test, the clamps are designed and machined; the temperature in the furnace is high so that a high-temperature clamping type extensometer is used for introducing load linear displacement out of a heating furnace to be measured. The testing method is simple and convenient to operate; the crack length is measured by using an electric potential method and the continuous test can be carried out for long time.

The invention discloses a subminiature minimal invasion high-temperature creep fatigue testing machine and the application thereof. The subminiature minimal invasion high-temperature creep fatigue testing machine mainly includes a driving system, a loading device, a constant temperature atmosphere furnace, a temperature control system, a high temperature gas protection system, a measurement control system and a water cooling system, wherein the loading manner of the machine is top vertical loading; a testing sample is positioned between an upper fixing platform and a lower fixing platform; and when loading is performed, a servo motor controls a lower loading rod to move upwards, a jumper bar is contacted with an upper loading rod, the lower end of the jumper bar is used for testing sample stamping through a pressure head. Aiming at an existing structure and a domain structure at a high temperature, the testing machine provided by the invention can be used for obtaining various high temperature performance of the material and estimating residual service life creep, safety operation state and the like of the high temperature structure, is convenient to operate, is uniform in testing temperature and high in testing precision, can be used for testing various high temperature performances such as high-temperature creep performance, high-temperature relaxation performance, high-temperature creep fatigue performance and high-temperature breaking toughness of the material.

The invention relates to a method for predicting the creep-fatigue service life of an aluminum alloy piston of a high-power diesel engine, belonging to the field of material science and engineering application technologyies. The influences of large-range and periodic working condition change of the high-power diesel engine on the fatigue service life of the piston structure are taken into account in the method, a new fatigue period is defined to predict the service life of the piston; considering that the engine works under a long-time variable working condition, and the non-linear coupling action between the creep damage and the fatigue damage generated inside a material can be effectively overcome through a creep-fatigue service life prediction model which is built on the basis of damage mechanics.

The invention provides a creep-fatigue life design method for a complex geometric structural member. The method comprises the steps: establishing a turbine disc three-dimensional solid model and a temperature field; determining a constitutive model and material parameters of the material of the turbine disc; considering the centrifugal force of the turbine disc, and applying centrifugal loads according to the load condition of the structural member in actual work; respectively selecting a fatigue damage model and a creep damage model, and writing the fatigue damage model and the creep damage model into a subprogram UVARM; substituting the subprograms to obtain a total damage cloud chart, and further obtaining a service life distribution cloud chart of the turbine disc; seeking the optimalsolution of long service life and high load by changing the temperature field and centrifugal load of the turbine disc in the load maintaining stage. According to the service life design method, temperature distribution, fatigue damage and creep damage of the structural member are considered in simulation, the service life of the load structural member under different service temperatures and loadhistories can be predicted, and the method has the advantages of being visual, wide in application range and high in accuracy.

The invention relates to an on-line safety assessment method of a water wall, comprising the following steps: firstly arranging a few test points at the pipe section with flow heat transfer representativeness in each radiated area for being combined with the existing inlet and outlet test points outside the furnace, monitoring characteristic parameters in the water wall pipes of the station boiler as calculation and checking point, inputting the characteristic parameters into a computer for processing, and computing the parameters such as the flow rate, the pressure of the inlet and outlet, the enthalpy value, the temperature value of furnace inner wall of each section of pipe along the length, the amplitude value of the variation of stresses and the like of all pipes in the group on line and in real time through a flow heat transfer law so as to judge whether unsafe factors including the instable hydrodynamic force, excess temperature, creep fatigue damage and the like occurs. The computed result is displayed in real time, and the related data is recorded as the basis for judging whether the water wall is in safe operation, thereby realizing optimized running of the equipment, arranging examination and maintenance management according to the state and fully implementing the examination and reparation based on the condition of the equipment.

The invention relates to a high-temperature large-load test fixture and test method for a turbine blade joggle joint structure, which can be used for test loading of thermal mechanical fatigue, creep-fatigue, low-cycle fatigue, creep and the like of the turbine blade joggle joint structure. The upper end and the lower end of the fixture are respectively connected with a fatigue testing machine through a clamping component, and the clamping components are connected with a turbine blade upper fixture and a turbine blade lower fixture through dovetail-shaped joggle joint structures; the turbine blade upper fixture is mainly composed of two components, a cold water channel is formed in the turbine blade upper fixture, a turbine blade is installed in an inner cavity formed by the two components, and the installation and positioning of the turbine blade and the blade upper fixture and the transmission of an axial load are achieved through a pair of inclined planes of the root extending section; the lower fixture is made of a high-temperature alloy material and is matched with a turbine blade tenon through a longitudinal tree-shaped mortise, and the blade joggle joint structure can be heated by using an induction heating coil. According to the invention, stable clamping of the turbine blade is realized, and the test requirements of applying a temperature load ranging from room temperature to 500 DEG C and a mechanical load from 0N to 150kN to the joggle joint structure can be met.

The invention relates to an aeroengine combustion chamber service life prediction method. The method comprises following steps: aeroengine combustion chamber CFD analysis; aeroengine combustion chamber elastoplastic static analysis; aeroengine combustion chamber load spectrum compilation; aeroengine combustion chamber base alloy fatigue test piece design: designing hastelloy alloy creep-fatigue experimental standard pieces; aeroengine combustion chamber base alloy fatigue test load design; aeroengine combustion chamber base alloy test; using a combination of support vector machine (SVM) and genetic algorithm (GA), a model of alloy damage prediction for aeroengine combustor is established; aeroengine combustion chamber service life prediction is achieved.

The invention provides a creep fatigue life prediction method based on a crystal plasticity theory. The method comprises the following steps: establishing a representative unit model of ABAQUS based on an electron back scattering diffraction technology; correcting the back stress model and writing the back stress model into a subprogram UMAT to obtain a creep fatigue hysteresis loop; fitting a creep fatigue hysteresis loop through a test parameter method to obtain material parameters; calculating a stress-strain value of each integral point and averaging the stress-strain values to obtain a creep fatigue hysteresis loop and a post-processing cloud atlas; extracting maximum plastic slippage and energy dissipation from the creep fatigue hysteresis loop and the post-processing cloud atlas, analyzing the change rule of the maximum plastic slippage and energy dissipation along with circulation cycles, and providing creep and fatigue indication factors; and predicting the creep fatigue crackinitiation life according to the indication factor. According to the creep fatigue life prediction method, plastic slippage and energy dissipation are used as fatigue and creep indication factors, the creep fatigue damage evolution rule can be better reflected, the crack initiation position can be accurately predicted, and the method has the advantages of being visual, high in applicability and high in accuracy.

The invention discloses a life prediction method suitable for various cyclic loads, which comprises the following steps: carrying out any cyclic load test on a to-be-tested material, such as a strain-controlled pure fatigue test, a strain-controlled creep fatigue test or a stress-strain hybrid-controlled creep fatigue test; calculating fatigue dynamic viscosity and creep dynamic viscosity according to the test input parameters and the hysteresis curve of the half-life cycle; calculating the total energy absorbed in the cycle process according to the hysteresis curve of the half-life cycle; andfinally, establishing a life prediction equation by utilizing the relationship that the accumulated dynamic viscosity related to the fatigue dynamic viscosity and the creep dynamic viscosity is equalto the absorbed total energy, and predicting the cycle life of the to-be-tested material under the rest two cyclic load tests. According to the method, the cycle life under various cyclic loads can be simultaneously predicted by using the same group of parameters, and the method is widely applied to different materials to be tested.

The invention relates to a creep-fatigue life prediction and reliability analysis method for Martensitic steel. According to the method, first, mechanical work density is defined; second, a creep-fatigue life prediction model based on the mechanical work density is derived, and the randomness of stress and life is considered; and last, a P-delta(W

)-N<f> curve of creep-fatigue life is proposed, and a creep-fatigue life reliability analysis model is given. Compared with the prior art, the method has the advantages that prediction is more accurate, and reliability is higher.

The invention provides a creep-fatigue interaction test device, which comprises a lever, wherein one end of the lever is connected with a sample arranged in a high-temperature heating furnace; the other end of the lever is connected with an upper suspender; the upper suspender is connected with a lower suspender; a loading and unloading tray is positioned under a lower weight tray; and the sample is connected with a leveling transmission mechanism through a tie rod. The creep-fatigue interaction test device is characterized in that: the end part, which is connected with the upper suspender, of the lever is connected with displacement sensor which is used for leveling; a programmable logic controller is connected with a variable frequency motor mechanism; and the leveling transmission mechanism and a loading and unloading transmission mechanism are respectively driven by the variable frequency motor mechanism. The invention adopts another technical scheme that: a method adopting the equipment is provided. The creep-fatigue interaction test device is relatively low in cost and easy to realize, and has the advantages of stable power value, reliable change and the like, of a lever type creep lasting tester. In addition, the displacement sensor is adopted to perform lever leveling control, so compared with the prior art in which photoelectric limit switch control technology is adopted, the creep-fatigue interaction test device is higher in control precision.

The invention discloses a newly developed lead-free solder, and in particular relates to a low-cost and high-performance lead-free solder for microelectronic package. The lead-free solder is characterized by comprising the following components by weight percentage: 0.5-1% of Ag, 0.3-0.7% of Cu, 1-3% of Bi, 0.0002-0.0005% of P, 0.01-1% of Ce, 0.01-0.15% of Ni and the balance of Sn. The lead-free solder meets the dual requirements of the market for no lead and benefit. The lead-free solder provided by the invention has the characteristics of no toxicity, good mechanical properties, good electrical properties, excellent oxidation resistance, excellent corrosion resistance, good creep fatigue resistance, good wettability, good spreadability, high solder joint reliability, low cost, good mechanical properties and the like.

A design method for creep-fatigue strength of a plate-fin heat exchanger. The method includes preliminarily designing the plate-fin heat exchanger according to its service requirements, making a primary stress assessment for the plate-fin heat exchanger, calculating the equivalent mechanical and thermophysical parameters of the plate-fin heat exchanger core to satisfy the allowable stress requirement, performing a thermal fatigue analysis for the plate-fin heat exchanger based on these parameters and then calculating the fatigue life and creep life of the plate-fin heat exchanger to accomplish the comprehensive design of the plate-fin heat exchanger in the high-temperature service. The design method provides an effective method for the high temperature design of the plate-fin heat exchanger.

The invention relates to a method for predicting the dual-scale creep fatigue life of a discontinuous structure. The method comprises the following steps: extracting a displacement field of a finite element model of the discontinuous structure; obtaining crystal plasticity model parameters, and establishing a crystal plasticity finite element model at the dangerous position of the discontinuous structure; taking a displacement field of the finite element model of the discontinuous structure as a boundary condition of a crystal plasticity finite element model, and constructing a dual-scale finite element model of the discontinuous structure; acquiring a creep indication factor and a critical value thereof, and a fatigue indication factor and a critical value thereof; and predicting the creep fatigue life of the discontinuous structure. According to the method, the stress condition of the discontinuous structure on the macro scale can be reflected, the damage evolution of the discontinuous structure on the micro scale can be revealed, the dangerous position of creep fatigue crack initiation can be effectively obtained, and therefore the creep fatigue life of the discontinuous structure can be accurately predicted; and theoretical support is provided for premature failure prevention and life extension of the discontinuous structure.

The invention discloses an aero-engine combustion chamber creep fatigue life prediction method. The method comprises: obtaining historical data and an initial feature subset of a to-be-predicted aero-engine combustion chamber; training the extracted initial feature subset by adopting an iterative decision tree algorithm to obtain a creep fatigue life prediction model of the aero-engine combustion chamber, and predicting the creep fatigue life of the aero-engine combustion chamber by utilizing the creep fatigue life prediction model of the aero-engine combustion chamber obtained in the step 2; and performing model calculation by taking the aero-engine combustion chamber load spectrum obtained in the step 1 as an input quantity of a prediction model so as to predict the creep fatigue residual life of the aero-engine combustion chamber. The invention further discloses a system for predicting the creep fatigue life of the aero-engine combustion chamber.

The invention discloses a high-precision creep fatigue crack propagation testing machine which comprises a direct-current bias power supply, a voltage instrument and a testing host. The testing host comprises a high-temperature CT stretching tool, a high-temperature furnace observation window, a split high-temperature furnace (1200 DEG C), a high-temperature furnace rotating bracket, an electronicuniversal test host, a CCD camera rotating bracket, a CCD camera, a temperature control box, a temperature control system, a test control system and software. A crack propagation test of a high-temperature alloy material in a high-temperature environment is realized by improving a conventional static electronic universal testing machine and adding software and hardware.

The invention relates to a creep-fatigue property testing system with a controllable oxygen partial pressure. The creep-fatigue property testing system comprises a mixed gas inflating subsystem, a mechanical loading main unit, an inflating high-temperature furnace and a circular water cooling subsystem, wherein the mixed gas inflating subsystem comprises a premixed inflating tank, an oxygen source and an argon source; the oxygen source and the argon source are respectively connected with the premixed inflating tank through mass flowmeters; the mass flowmeters control the oxygen source and the argon source to provide oxygen and argon with preset proportions to the premixed inflating tank according to the preset proportions provided by a computer industrial control subsystem; the inflating high-temperature furnace is arranged between a cabinet of the main unit and a cross beam of the main unit; the circular water cooling subsystem is connected with the inflating high-temperature furnace. The testing system disclosed by the invention is integrally redesigned, and is additionally provided with the mixed gas inflating subsystem, and all key parts are improved by aiming at an application occasion of an oxygenating environment, so that the testing system can meet the demand of a creep-fatigue property test with the controllable oxygen partial pressure, is high in testing precision and stable and safe in operation; the oxygen partial pressure is controllable in multiple stages.

The invention provides a creep fatigue damage assessment method for a superheater tube plate. The creep fatigue damage assessment method comprises the steps of correcting a steady-state cyclic analysis method; combining a CAE model, a yield stress and temperature related ideal elastic-plastic model and a temperature related creep constitutive equation, and analyzing the creep cycle plasticity behavior of the tube plate in the steady-state cycle; designing a fatigue curve to evaluate fatigue damage by adopting a general slope method; evaluating creep damage by adopting a time fraction method, a ductility depletion model or a strain energy density depletion model; and evaluating the creep fatigue damage according to a linear damage superposition criterion or a unified creep fatigue equation. According to the creep fatigue damage assessment method for the superheater tube plate, the non-isothermal creep effect, the multiple load holding periods and the stress-strain relaxation history in the load holding periods are considered, creep fatigue total damage assessment can be conducted on the superheater tube plate, and the creep fatigue damage assessment method has the advantages of being visual, high in applicability and high in accuracy.