46 results about "Nominal stress" patented technology

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 novel method for measuring compact tension specimen fracture parameters by using double extensometers. The novel method comprises the following steps of: measuring two opening displacements by using the double extensometers; obtaining a crack tip opening displacement (CTOD) of a compact tension test through calculation by using a triangular relation; and calculating a CTOD value under each load and a nominal stress corresponding to the CTOD value, and obtaining a relation between the nominal stress and the CTOD, thereby obtaining a CTOD design curve of the compact tension test. The fracture parameter test method disclosed by the invention has the characteristics of simpleness, easy operation, simpleness for processing data, high precision of a critical CTOD value, comprehensive data, large information quantity, freeness from test precision influences of other parameters, such as strength, Young modulus, rotary factor and load, capabilities of obtaining the CTOD data of the whole test loading process and obtaining the CTOD design curve of the compact tension test under an actual board thickness condition.

The utility model discloses a method using a spherical indenter for measuring the phase transition properties of shape memory alloy (SMAs). The phase transition is induced under the pressure of the spherical indenter pressed into the surface of the shape memory alloy; the load signals and the displacement signals in the unloading process are detected by a sensor at the same time, and the ht curve of the load F-displacement is obtained; the load-displacement curve obtained in the test is transformed to a corresponding nominal stress Sigmam-nominal stress Epsilonm curve according to the analysis; then properties of the transformation stress, the elastic modulus and other aspects of the SMAs can be obtained. The test method has advantages that the method is easy in operation, and the nondestructive measurement of the materials can be elementally realized; the method not only can be widely used in the measurement of the phase transition properties of various super-elastic and shape memory SMAs, but also is particularly suitable for the phase transition measurement of the SMAs films with the low thickness only up to a plurality of micrometers or the SMAs micro devices with the micrometer order typical structure size; the method has accurate and precise measured value, which can supply the reliable measurement basis of the phase transition property for the application of the SMAs in the micro-electro-mechanical system.

The invention discloses a method for predicting the fatigue life of a straw throwing impeller. The method comprises: fluid-solid coupling and throwing impeller stress analysis; a two-parameter nominalstress model; a two-parameter nominal stress model of the throwing impeller; and a Mine fatigue accumulation damage model. The method disclosed by the invention has the benefits that: the method forpredicting the fatigue life of the throwing impeller that the two-parameter (the average stress Sa Sm and the stress amplitude Sa) nominal stress model, the Miner fatigue accumulation damage model anda fatigue life logarithmic normal distribution model are combined is adopted; simultaneously, to accurately obtain the random cycle load of the throwing impeller, the stress thereof is calculated andanalyzed by adoption of a fluid-solid coupling method; and thus, on this basis, prediction of the fatigue life of the throwing impeller is carried out.

The invention discloses a fatigue life calibration method suitable for a structural connection piece, and belongs to the technical field of aircraft strength design. The method comprises the steps of1, establishing a stress spectrum of a key connection part; 2, calculating and establishing a stress severity coefficient of the connection part; 3, obtaining an S-N curve corresponding to the stressseverity coefficient of the key part; 4, determining a most sensitive parameter theoretical fatigue limit C in a nominal stress method; 5, performing optimization on the theoretical fatigue limit C; and 6, performing verification on the determined stress severity coefficient and the corresponding theoretical fatigue limit C. The life prediction under a load spectrum is performed by utilizing parameters obtained by optimization and a stress severity coefficient method, and the predicted and calculated stop life t' under the load spectrum and the actually measured life mid-value under the load spectrum are subjected to error comparison; and the life prediction under other load spectrums is performed by adopting the parameters obtained by the optimization and a nominal stress method through the verification, so that life calculation results under other load spectrums have relatively high precision.

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 relates to a cooperative optimization method for the bearing position and the thickness of a rotary-kiln cylinder. The cooperative optimization method is characterized by including the steps that firstly, a relationship model between the bearing position, the cylinder thickness and bearing force is obtained according to the distribution condition of loads and the rigidity of the cylinder, the constraint condition of cylinder-load balancing distribution is considered, and a cylinder-load balancing distribution optimization model is established; secondly, stress-time courses of all cross sections of the cylinder are acquired through contact finite element analysis between the cylinder and a rolling ring, the fatigue life is forecasted with the nominal stress method, a constraint is the transverse-rigid-and-longitudinal-soft design rule of the cylinder and non-exceeded cylinder-cross-section deformation, and an equal-life optimization model of all the cross sections is established; finally, the cylinder-load balancing distribution optimization program and the cylinder equal-life optimization program are continually called, the loads of the cylinder are distributed on all bearings accordingly, and the service life of all the cross sections of the cylinder tends to be coincident. According to the cooperative optimization method, the potency of all parts of a rotary kiln can be fully developed, the number of kiln stopping is reduced, and the production benefits of the rotary kiln are improved.

The invention belongs to the field of structural design and safety assessment of high towers and particularly relates to a method for designing fatigue life of a windproof and shockproof high tower. The method specifically comprises the following steps: setting reference wind speed and determining a discrete wind speed and direction joint probability distribution interval; designing various structural forms of dangerous section parts and solving stress concentration factors thereof; simulating a nominal stress time-history response of a dangerous section of the high tower in different directions at each reference wind speed in unit time; calculating the wind-induced fatigue life of the high tower with the dangerous section part in different structural forms and at different defect assessment levels; judging whether the life meets a requirement or not, determining a design scheme if the requirement is met, redesigning the overall structure of the high tower if the requirement is not met and performing the processes again. The method provided by the invention can provide a reference for the reasonable design and the safe operation of the high towers in coastal windy areas.

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.

The present invention provides an electrolytic copper foil which is excellent in the extension property and can endure the change in the expansion and contraction at the fine units while having high strength, and a method of producing the same. Specifically, the electrolytic copper foil for a negative electrode collector in a secondary battery, wherein in a nominal stress strain curve, a tensile strength is 45 to 70 kg/mm², and a value of the tensile strength is greater than a value of a breaking stress, and an extension rate is 5% or more.

The invention discloses a notch part local stress-strain calculation method under high-temperature multi-axis loading. The notch part local stress-strain calculation method comprises the steps of analyzing and determining a notch part local stress-strain state under high-temperature multi-axis loading; Reading seven real stress strains and constitutive model variable parameters in the previous step, and calculating a yield function f1 in the previous step; Calculating nominal stress and strain, and determining loading; Judging whether the current loading is elastic loading or plastic loading by utilizing the yield function in the last step; Calculating a yield function f2 under the current loading step and judging; And storing all real stress strains and constitutive model variable parameters, and returning to carry out next-step solving calculation until the loading is finished. According to an algorithm program prediction result and a finite element simulation result of the method, it is found that the stress-strain peak-valley value is close to the shape of the hysteresis loop. The prediction result shows that the method can be used for well calculating the local stress-strain response of the notched part under the high-temperature multi-axis loading.

The invention relates to a safety analysis method of an axis system during variable frequency operation of a motor. The method comprises steps of 1), testing dynamic torque signals on a rotation shaft near a diaphragm coupling during variable frequency operation of the motor, and acting the dynamic torque signals to a diaphragm of the diaphragm coupling and the rotation shaft so as to obtain torsional stress borne by the rotation shaft and dynamic tension and compression stress borne by the diaphragm; and 2), according to working features of the rotation shaft and the diaphragm coupling, using a nominal stress method to calculate fatigue life of the rotation shaft under the effect of high cycle load, and using a local stress method to calculate the fatigue life of the diaphragm under the low cycle load, and using a quite small value of the two kinds of calculated life to estimate the fatigue life of the axis system. Compared with the prior art, the safety analysis method is advantageous in that the safety analysis method is simple and feasible, and effects of steady-state and dynamic torque on the rotation shaft of a variable frequency driving motor are considered.

The invention discloses a method for predicting the multi-axis constant-amplitude thermal mechanical fatigue life of a notched part based on a Kf method, and the method can consider the influence of a notch on the fatigue life under multi-axis constant-amplitude thermal mechanical loading, namely the influence of the notch on a damage mechanism, including the influence of the notch on fatigue damage, oxidative damage and creep damage. The fatigue notch coefficient Kf changing along with the temperature is calculated through the stress-strain history of the notch piece root under the multi-axis isothermal constant-amplitude load, the Kf changing along with the temperature is combined with the nominal stress load spectrum increment, and then the stress-strain history of the notch root is obtained through calculation. The comparison error between the prediction result of the multi-axis constant-amplitude thermal mechanical fatigue life of the notched part calculated by adopting the method and the test result is dispersed within 3 times of the band, which is of great significance to the accurate prediction of the life of an actual engineering component.

The invention discloses a fatigue life calibration method based on a nominal stress method and belongs to the technical field of aircraft strength design. The method comprises the steps that first, for test pieces of the same material with different surface quality, values of parameters alpha and A of an S-N curve are basically identical, and a theoretical fatigue limit C is determined as a uniquesensitive parameter needing optimization; second, according to a load stress spectrum designated in advance, mid-value life t<50> corresponding to the load stress spectrum is determined as an objective for optimization, an initial value is set, the value of the theoretical fatigue limit C is continuously adjusted, the nominal stress method is repeatedly utilized to calculate the mid-value life till the calculated life is equal to a set target mid-value t<50>, and the corresponding C value at the moment is a corrected C value in a three-parameter expression of the S-N curve; and third, the determined nominal stress method and the corresponding theoretical fatigue limit C are verified, the parameters obtained through optimization and the nominal stress method are adopted through verification to perform life prediction under other load spectra, and therefore life calculation results under other load spectra have high precision.

Provided is a laminated body of at least one metal foil and resin layers, which is suitable for drawing. The laminated body includes at least one metal foil and at least two resin layers. The laminated body has a thickness of 25 to 500 μm. In the laminated body, both surfaces of each metal foil are closely laminated to the resin layers, and the relationships: 60≤σY≤150, and 1.4≤σb/σY are satisfied, in which σY represents a nominal stress (MPa) at a nominal strain of 5% when a tensile test according to JIS K 7127: 1999 is performed on the laminated body, and σb represents a nominal stress (MPa) at a nominal strain at which the metal foil in the laminated body is broken when a tensile test according to JIS K 7127: 1999 is performed on the laminated body.

The invention relates to a small eccentric tension reinforced concrete, steel reinforced concrete or steel plate concrete shear wall medium earthquake repairable checking calculation method, which isused for solving the technical problems of nominal stress and maximum crack width control of a wall limb in a high-rise structure. According to the technical scheme, the method comprises the steps that firstly, nominal tensile stress and nominal shear stress standard values of wall limbs are linearly superposed to form nominal combined stress standard values, the nominal combined stress standard values are compared with concrete tensile strength standard values, and nominal tensile stress item coefficients are determined; Secondly, checking according to a nominal combination stress formula, and when a nominal tensile stress standard value is not greater than a corresponding numerical value, not configuring section steel or a steel plate; Thirdly, steel bars (including section steel and steel plates) and other effective forces in the concrete wall column are controlled to be not larger than the corresponding steel bar stress of the maximum crack width; And finally, comprehensively judging and adjusting the repairable state. The method is suitable for checking when various concrete shear walls are under small eccentric tension, is well connected with specifications, can be widely applied to the field of high-rise structures, and has good technical and economic benefits.

The invention discloses an arm frame structure fatigue strength monitoring method, device and system and a fire truck. The monitoring method comprises the following steps: receiving stress value of at least one detection point of an arm frame structure in working state; for each detection point, calculating accumulated fatigue nominal stress frequency thereof according to the stress value thereof; and determining maintenance and/ or scrapping of the arm frame according to the accumulated fatigue nominal stress frequency and preset maintenance frequency and/ or preset scrapping frequency. The method can prevent the fatigue strength of the arm frame from being misjudged, and the arm frame can be maintained and/or scrapped in time, thereby improving usage efficiency and work security of the arm frame.

The invention provides a method and device for establishing an HBPRC constitutive model, and relates to the technical field of civil engineering. The method comprises the following steps: establishing a first calculation relationship among nominal stress, mechanical damage variables, elastic modulus and axial strain of HBPRC according to a damage mechanics theory and a strain coordination principle; obtaining a second calculation relationship among the mechanical damage variable, the axial strain, the dimension parameter of the Weber distribution and the shape parameter of the HBPRC; obtaining a third calculation relationship among the enhancement effect parameter, the reference elastic modulus and the elastic modulus of the HBPRC according to the effects of the BF and the PF. According to the first calculation relation, the second calculation relation and the third calculation relation, an HBPRC constitutive model is established, the constitutive model is the calculation relation between the nominal stress of the HBPRC and the reference elastic modulus, the axial strain and the total damage variable, and the total damage variable is obtained by calculating the mechanical damage variable and the enhancement effect parameter. The method is used for establishing a constitutive model of HBPRC.