32 results about "Threshold stress" patented technology

The invention provides a gear bending fatigue life forecast method and a device. The gear bending fatigue life forecast method comprises the steps that a fatigue limit amendment model is built based on the surface roughness, and the fatigue limit of materials is amended according to the amendment model, the fatigue limit after the amendment is obtained; the threshold crack length is determined according to the threshold stress strength factor range and the amended fatigue limit; a fatigue crack size initiation model is created, and gear fatigue crack initiation life is forecasted based on the fatigue crack size initiation model; gear fatigue crack propagation life is forecasted based on the linear elastic fracture mechanics guidelines; according to the gear fatigue crack initiation life and gear fatigue crack propagation life, a gear bending fatigue calculation model is built, to calculate the gear bending fatigue life.

A crack arrest process and device thereof for removing fine cracks on alloy surfaces, relates to laser impulse processing application technique field. Oxide layers and pollutants on alloy surfaces which affect surface bonding force are removed to obtain good glue-joint strength and permanent stability; a flexible film is adhered to the alloy surface as a crack arrest patch, and a layer of black lacquer coating is applied on the crack arrest patch; laser pulse with following parameters: pulse energy of 15-40J, pulse width of 20-30ns, light spot size of 4-10mm, repetition frequency of 0.5-10Hz is selected to performing laser impact crack arrest according to damage status of the cracks; laser crack arrest is performed by selecting crack arrest route, and crack effects are inspected by using no-damage technique during crack arrest process. The invented method and device can increase alloy surface fatigue threshold value, the existing of residual compressive stress on metal surface after laser impulse enhances fatigue threshold stress on material surface greatly.

This invention discloses one current load metal film stretching stress value test describing method, which comprises the following steps: processing current load and micro force stretching on the good metal film of interface; during this process recording the metal film stress curve and resistance change curve; acquiring the crack percentage stress curve through micro analysis by observing metal film. The current load metal film and flexible base board system invalid threshold system is composed of three threshold stress, such as the stress from resistance change to stress curve from linear phase to non-linear conversion; micro crack percentage stress curve back reducing as zero theory into threshold extension stress; resistance change to stress curve resistance runaway time into threshold crack unstable stress.

An energy absorbing device for carrying a passenger seat; the device comprises a base fixed to a vehicle; a member displaceable from base; at least one energy-absorbing arrangement interconnecting base and displaceable member. The energy-absorbing arrangement comprises a plastically deformable absorbing element in response to stresses greater than a predetermined threshold stress. In some embodiments the plastically deformable absorbing element is a helically configured ribbon having spaced-apart ribbon laps. In other embodiments the plastically deformable absorbing element is compressible, and/or extendable. A method of attenuating the acceleration applied to a passenger due to impact is disclosed; the method comprises steps of: providing an energy absorbing device fixedly attaching the base to the vehicle; fixedly attaching the passenger seat to the base; accidently applying the impact to the vehicle; displacing the displaceable member relative to the base; attenuating the effect of the impact on the passenger.

The invention discloses a method for constructing forming limit stress diagram of metal sheet, belonging to the technical field of forming metal sheets. The method comprises the following steps: printing grids or speckles on a metal sheet material by using an electrolyte corrosion method; applying prestrain to the sheet; then measuring the main strain and secondary strain of a prestrain test sample; preparing a second-stage test sample from a pre-deformed test sample by adopting a linear cutting manner, and bulging by adopting a semispherical rigid convex die, until the test sample has necking or fracture, and measuring the main strain and secondary strain of a second-stage deformation test sample; and acquiring the strain values of two stages, and acquiring the forming limit stress diagram by adopting corresponding yield criterion and conversion formula. The method has the advantages that the forming limit stress diagram of metal sheet can be rapidly and accurately obtained, and the problem that the stress is difficult to measure directly can be solved.

The invention relates to a continuous loading indentation stress corrosion tester and a test method therefor. The continuous loading indentation stress corrosion tester is used for researching hysteresis growth and related mechanical behaviors of material cracks and especially for researching rules of the influence produced by different stresses, environmental mediums and temperatures on crack nucleation and growth, and clearly expounds the rule and the mechanism of material invalidation under the stress-environment coupling condition. The test method comprises the following steps of 1, through contact between a pressure head and a test sample under a certain load, determining fracture toughness of a brittle material, and observing the influence produced by the environment on crack growth under the continuous loading condition, 2, determining threshold stress of hysteresis growth of cracks of the brittle material by radial cracks having certain length under a certain environmental condition, 3, in a solution medium, researching crack growth of a toughness material by indentation, and 4, observing a change of electrochemical parameters in crack growth by connection with an electrochemical workstation. The continuous loading indentation stress corrosion tester can be operated conveniently and simply, realize control of an experimental environment and a load, is especially suitable for long-term loading in different environments, has a simple structure, is convenient for operation and has a large application prospect.

The invention discloses a method for measuring stretching stress corrosion of a deforming aluminium alloy. The method comprises the following steps: removing an alclad layer on the surface of a sample; measuring stress corrosion sensitivity through relative change of same mechanics parameters of the same sample exposed under contrast test environment and exposed under inertia environment; and measuring the threshold stress of stress corrosion according to a binary search method. The method for measuring the stretching stress corrosion of the deforming aluminium alloy is capable of performing quantification measurement on stress corrosion sensitivity of the aluminium alloy.

In a method of determining a fatigue crack lifetime of a low-alloy steel material coming in contact with high-pressure hydrogen in a high-pressure hydrogen environment, estimate a fatigue crack acceleration starting point K_max^T of the low-alloy steel material using a crack-growth threshold stress intensity factor K_IH-R obtained through a rising load test on the low-alloy steel material in a high-pressure hydrogen environment. The high-pressure hydrogen environment of the rising load test is a high-pressure hydrogen environment which has the same pressure and atmosphere as in the high-pressure hydrogen environment in which K_max^T is estimated and in which the test temperature tolerance between both environments is ±5° C.

An analysis model control unit disposes at least two component models, which are to be used in assembly of a product to be evaluated, in virtual space displayed in a screen. A virtual glove controller which functions as a virtual operation control unit moves and operates component models, which are disposed in virtual space, in accordance with an input operation signal of a user by a virtual glove. When the two component models are brought into contact with each other, a model conversion unit converts them into component analysis models. A deformed structure analysis unit executes structure analysis calculations with respect to the relative movement caused along with assembly of the two component analysis models after contact so as to calculate deformation and deformation stresses. An evaluation processing unit compares the deformation stress obtained as a result of the structure analysis calculations of the component analysis models with a threshold stress of the material so as to evaluate whether assembly can be performed without breaking the components.

A method for defining a threshold stress curve utilized in fatigue and/or damage tolerance analysis, the method including conducting a direct test method on a plurality of specimens with a notch to generate raw data, the notch in each of the specimens having a notch dimension; determining a plurality of analyzed data points based upon the raw data; determining a regression line based upon the plurality of data points, the regression line including an exponential portion and a power law portion; and connecting the exponential portion and the power law portion of the regression line to form a threshold stress curve based on the regression line.

The invention relates to a method for protecting the safety and stability of a movable museum collection in an earthquake. The method comprises the following steps: a museum collection imitation is subjected to a material characteristic test in a laboratory, so that tensile and compression resistance limit stress, shear resistance limit stress and a dynamic modulus of elasticity and a dynamic modulus of shearing of a material are obtained; after a stress reduction factor K is fetched, the tensile and compression resistance limit stress and the shear resistance limit stress of the imitation are multiplied by the K, and the product serves as allowable dynamic stress of the museum collection; allowable acceleration is calculated according to the D'Alembert's principle; the stability of the museum collection is classified into three stability levels according to the allowable acceleration, the friction factor and the height-width ratio (namely the allowable vibration index)of the museum collection; finally, an exhibition stand is designed and arranged, and the museum collection is placed according to a classification result. The discriminating method is simple and practicable, and the result is accurate; the allowable vibration index provides a scientific basis and a quantitative criterion for control cover the safety guarantee of the museum collection in an earthquake.

A method for monitoring and estimating the carrying capacity of a pre-stressed ferromagnetic metal armature element of a metal-concrete load-bearing structure is proposed, comprising the steps of: preliminary calibrating the element by passing electric current therethrough and measuring its electrical resistance with respect to the tension stress applied to the element, determination of an ultimate resistance value corresponding to a predetermined ultimate limit stress value permitted to the element, saving the ultimate resistance value in a computer memory, passing electric current through the element during construction or exploitation of the load-bearing structure being in a loaded state, measuring altered resistance of the element, comparing the altered resistance with the ultimate resistance value, and warning when the altered resistance reaching the ultimate resistance value. Additional embodiments disclose deployment of two types of electric current: alternating and direct. The method allows significantly increasing safety of metal-concrete structures and reducing electric energy consumption.

The invention discloses a high-temperature structural member service life prediction method based on nonlinear creep-fatigue interaction, and the method comprises the following steps: constructing a service life prediction model which is used for carrying out the service life prediction of a high-temperature structural member through obtaining first creep damage based on threshold stress and second fatigue damage based on average stress; the method comprises the following steps: acquiring first creep damage by acquiring creep fracture strain energy, elastic modulus, stress level and peak strain retention time of a high-temperature structural member; second fatigue damage is obtained by obtaining the plastic strain range and average stress of the high-temperature structural part under the creep-fatigue condition, the plastic hardening index of the high-temperature structural part under the pure fatigue condition and the material constant of the high-temperature structural part; based on a life prediction model, according to the first creep damage and the second fatigue damage, life prediction is conducted on the high-temperature structural part; according to the method, the limitation of a bilinear creep-fatigue life prediction method is solved, and the prediction precision of the creep-fatigue life of the material is relatively high.

The invention discloses a creep life prediction method based on threshold stress and tensile strength, and the method comprises the following steps: 1, carrying out the high-temperature tensile test of a material at different temperatures T, and obtaining the tensile strength sigma b at the corresponding temperature; 2, carrying out a plurality of groups of high-temperature creep tests under different stress conditions at different temperatures to obtain the minimum creep rate and the creep life tf under the corresponding temperature stress conditions; 3, obtaining threshold stress sigma th corresponding to different temperatures according to the minimum creep rate; 4, establishing a function relationship between the threshold stress and the temperature based on the threshold stress sigma th at different temperatures; 5, on the basis of the threshold stress and the tensile strength, establishing a creep life prediction formula; and predicting the creep life under different stress temperature conditions through a creep life prediction formula. According to the method, the common influence of the threshold stress and the tensile strength is considered, the life prediction precision is high, and the extrapolation capability is high.

The invention discloses a method for predicting creep damage and deformation evolution behaviors along with time, which comprises the following steps of: obtaining tensile strength sigma b through a high-temperature tensile test of a material; a corresponding creep strain curve, the minimum creep rate and the creep life tf are obtained through a high-temperature creep test; obtaining threshold stress sigma corresponding to different temperatures; establishing a function relationship between the tensile strength sigma b and the temperature T and between the threshold stress sigma th and the temperature T; respectively establishing a minimum creep rate and creep life tf prediction formula based on the threshold stress sigma and the tensile strength sigma ; establishing a creep damage constitutive model, wherein the creep damage constitutive model comprises a strain rate formula and a damage rate formula; obtaining an evolution behavior of strain deformation along with time by solving a strain rate formula; and obtaining the evolution behavior of the damage along with time by solving a damage rate formula. According to the method, the defect that a traditional creep damage constitutive model is difficult to extrapolate is overcome, accurate extrapolation can be achieved, and the prediction precision is high.