135 results about "Stress time" patented technology

The invention relates to an assembly digital field based on a flexible array pressure sensor and a method for training gait. Parameters of an athlete including action time sequence, action frequency, position calibration, stress center point, stress time and flight time can be acquired through acquiring information including pressure of foot soles of the athlete contacted with the flexible array pressure sensor unit in the assembly digital field. The digital field and the method have the advantages that the requirement of real time can be met in longer distance; the module of the assembly digital field can be disassembled and assembled arbitrarily, and can extract gait characteristics on multiple sports training events; and the athlete can correctly recognize the training effect of the athlete self through a sports effect evaluation system and an expert system, and adjust the training plan in real time. The digital field and the method can also be applied in the field of mode recognition.

A method of dynamic durability analysis and fatigue area identification using modal techniques for a structure includes the steps of simulating a finite element model of the structure to determine modal stresses and modal displacements for an element of the structure and performing a modal transient analysis using the modal displacements. The method also includes the steps of determining a stress bound for the element from the modal stresses and modal transient analysis, determining if a stress bound for the element is greater than a predetermined value and identifying the element as a critical element if the stress bound for the element is greater than the predetermined value. The method further includes the steps of determining a stress time history for the critical element and using the stress time history to perform a fatigue analysis to identify an area of fatigue within the structure.

The present invention is directed to a number of improvements in methods for hot-carrier device degradation modeling and extraction. Several improvements are presented for the improvement of building device degradation models, including allowing the user to select a device parameter used to build the device degradation model independent of the device parameter selected. The user can also select the functional relation between stress time and degradation level. To further improve accuracy, multiple acceleration parameters can be used to account for different regions of the degradation process. Analytical functions may be used to represent aged device model parameters, either directly or by fitting measured device parameters versus device age values, allowing devices with different age values to share the same device model. The concept of binning is extended to include device degradation. In addition to a binning based on device width and length, age is added. In an exemplary embodiment, only devices with minimum channel length have degraded models constructed. The present invention also allows the degradation of one device parameter to be determined based on an age value derived from another parameter. In yet another aspect, a degraded device is modeled as a fresh device with a voltage source connected to a terminal.

The invention provides a method and a system for predicting random vibration life of a PCB solder point. Based on a sinusoidal vibration test and harmonic response simulation analysis, a stress-life curve of the PCB solder point is determined; According to a stress-time curve of a random vibration fatigue dangerous part of the PCB solder point or a strain-life curve of a PCB, the cycle number, stress amplitude and mean distribution of the random vibration fatigue dangerous part of the PCB solder point are determined with a rain-flow counting method; the random vibration fatigue loss of the PCB solder point is determined; and finally based on a Miner rule, according to the random vibration fatigue loss of the PCB solder point, the random vibration life of the PCB solder point is predicted. The whole process is based on precise data processing, the operability is strong, and a stress and time response signal is subjected to cycle number statistics and sorting with the rain-flow counting method, so that the data acquisition accuracy in the process for predicting the random vibration life of the PCB solder point is ensured.

The invention belongs to the technical field of bridges, and discloses a method for identifying damage on inhaul cables of long-span cable-stayed bridges. The method includes building finite element models of cable-stayed bridges; applying simulated wind load to the finite element models and acquiring wind speed time-history curves of the inhaul cables; computing stress time histories of the inhaul cables under wind load effect on the basis of the wind speed time-history curves; carrying out lifting wavelet packet decomposition on the stress time histories and stress time histories of bridge inhaul cables in non-damage states, extracting wavelet packet signal component energy and utilizing energy accumulation variation values as characteristic values for identifying damage positions of thestay cables; acquiring lifting wavelet packet component energy difference, building BP-AdaBoost models for identifying structural damage degrees and computing the fatigue reliability of the inhaul cables on the basis of the structural damage degrees. The method for identifying the damage on the inhaul cables of the long-span cable-stayed bridges has the advantages of excellent adaptability and identification reliability.

The invention discloses a brittle material crack initiation stress measurement system and a brittle material crack initiation stress measurement method. The brittle material crack initiation stress measurement system comprises a loading device, a CCD camera, a synchronizer trigger, a load-time signal receiving device and a digital image signal receiving device. The brittle material crack initiation stress measurement method includes synchronously triggering the loading device and the CCD camera by the synchronizer trigger, loading a sample and outputting a load-time signal; shooting sample surface images by the CCD camera in real time; not stopping shooting until the sample is destroyed; selecting a first frame of images shot by the CCD camera, marking 2 measurement points on the circumference of a through hole, continuously measuring tensile strain-time curves of the 2 measurement points in a whole loading process, and determining stress values, namely crack initiation stress sigmaci,on the stress-time curves corresponding to tensile crack initiation time T. The brittle material crack initiation stress measurement system and the brittle material crack initiation stress measurement method have the advantages that the position and the expansion direction of brittle material crack initiation can be controlled, the crack initiation time and the crack initiation stress can be determined objectively, precisely and quantitatively, authenticity and reliability of brittle material crack initiation stress measurement are improved effectively, and the method simple to operate, reliable in result and objective in quantization is provided for measuring crack initiation stress of rock-like brittle materials with prefabricated holes under uniaxial compression.

The invention discloses a fatigue stress spectrum analysis method and system of a longitudinally connected ballastless track on a bridge for improving the simulation accuracy of the fatigue stress spectrum of the longitudinally connected ballastless track on the bridge during service and providing important support for the fatigue design of the longitudinally connected ballastless track on the bridge. The method comprises the following steps: independently establishing a longitudinally connected ballastless track-bridge temperature field calculation model, a high speed train-longitudinally connected ballastless track-bridge three-dimensional finite element coupling dynamics model and a longitudinally connected ballastless track-bridge-bridge abutment longitudinal interaction model; utilizing the models to research the stress time travel curve and the fatigue stress spectrum of the longitudinally connected ballastless track on the bridge during the service under the composite actions of loads including a train vertical load, a train longitudinal load, a ballastless track concrete temperature load, a ballastless track concrete temperature gradient load, a ballastless track concrete contraction load, a ballastless track prestress load and the like. The mechanical model of the invention is finer, and a load model is more perfect.

The invention discloses a method for predicting a negative bias temperature instability (NBTI) service life of a pMOSFET (P-channel Metal Oxide Semiconductor Field Effect Transistor) device. The method comprises the following steps of: S1, before applying negative bias stress, measuring initial characteristics of the pMOSFET device to obtain initial parameters of the device; S2, applying a stress condition to a grid of the device, wherein drain voltage is normal working voltage; performing stress aging test to the device within a pre-set time interval; S3, testing the parameters of the device to obtain device parameters related to the aging time until the total stress time is ended; S4, when the drain voltage is the normal working voltage, repeating the steps S2 and S3; testing different stress conditions; referencing to the device parameters retrograded to a critical point; obtaining failure times of the pMOSFET device under the relative stress conditions; and S5, using the failure times of the pMOSFET device under the different stress conditions, predicting the reliability service life of the device when the gate voltage is the normal working voltage. Because the failure time of the device obtained by the method in the invention is shorter than that obtained by the conventional method, the NBTI service life of the pMOSFET device can be well reflected.

A method for testing temperature instability under negative bias relates to the field of semiconductor technology processing procedure. The method comprises the following steps: 1. the method for testing temperature instability under negative bias is characterized in that step 1, stress is applied to gate voltage to lift the gate voltage to gate voltage and then the gate voltage is reduced to an absolute value smaller or equal to working voltage in t; step 2, when the recovery stage finishes and before the next stress stage begins, an MOS transistor is measured; step 3, step 1 and step 2 are circularly executed until the accumulated stress time reaches reliability test standard. The method has the advantages of accurately testing temperature instability effect under negative bias, improving the accuracy of reliability assessment of semiconductor products, being beneficial to improving the technology of temperature instability under negative bias, shortening the cycle of product development and saving production cost.

The invention relates to the stress evaluation of a laser cladding layer and in particular relates to a nondestructive evaluation method of the stress of a cladding layer based on a critical refraction longitudinal wave. According to the invention, the nondestructive evaluation of the cladding layer stress is realized through selecting a double critical refraction longitudinal wave probe with a suitable central frequency; an optimum propagation distance is determined as the spacing distance between a propagation probe and a receiving probe to be fixed by combining the law that the energy of the critical refraction longitudinal wave in the cladding layer decays; the time difference between the critical refraction longitudinal signals is used for representing the change amount of the propagation speed of the cladding layer in the critical refraction longitudinal wave caused by the stress and taken as the characteristic parameter to evaluate the stress of the cladding layer to build a stress-time difference relation; a liner function is adopted to fit results to obtain an acoustoelastic equation used for representing the stress of the cladding layer, and therefore the nondestructive evaluation of the stress of the cladding layer based on the critical refraction longitudinal wave is realized.

The invention, a testing method for mode I crack dynamic fracture overall process parameters under blast loading, discloses the testing method for the dynamic crack initiation toughness, dynamic expansion toughness and dynamic crack arrest toughness of mode I crack under blast loading, and belongs to the technical field of geotechnical engineering. The configuration of an internal single crack disc specimen with a large size is an autonomous design; testing results cannot be influenced by reflected extension waves and transmission waves; and the method is suitable for researching the crack growth rate and growth behavior of the whole process. Blast loading adopts an 8# detonator; numeral calculation adopts a finite element difference software AUTODYN; and a result basically accords with atest. A load stress time history curve can be input into a finite element program ABAQUS; the time history curve of a dynamic stress intensity factor can be obtained; and the dynamic fracture toughness of a material can be determined through the fracture time of a crack. The specimen is simple in configuration and easy in processing; the test is concise and clear in process and convenient in operation; and researches on crack dynamic growth behavior and tests on the dynamic fracture toughness can be realized.

The invention belongs to the relevant technical field of the fatigue life calculation of a metal structure, and discloses a fatigue life assessment method based on an engineering machinery structure.The method comprises the following steps that: carrying out finite element analysis on the engineering machinery structure, and combining with a practical operating situation to determine a fatigue dangerous area; carrying out a dynamic stress testing experiment to obtain the stress time history of the fatigue dangerous area in multiple practical operating circulations; carrying out rain-flow counting, average stress correction and equivalent damage conversion on the stress time history in each operating circulation in sequence to obtain equivalent stress and equivalent circulation frequency corresponding to each operating circulation; and for the equivalent stress and the equivalent circulation frequency obtained each time, through a nonlinear cumulative damage theory, calculating the cumulative damage and the fatigue life of a bucket rod structure. By use of the method, the rain-flow counting method and the nonlinear cumulative damage theory are organically combined, the influence ofa loading sequence between the operating circulations is considered, a calculation process is simplified, calculation accuracy is improved, and the method is suitable for engineering application.

The invention provides a coating service life prediction method based on a stress and bonding strength evolvement mechanism and relates to a coating service life prediction method. The coating service life prediction method aims at solving the problem a comprehensive and objective coating service life prediction method is not disclosed at present. The coating service life prediction method comprises the steps that firstly, residual stress-time change relation and oxidation layer stress-time change relation are established, and a coating stress evolutionary physical model is established; secondly, a thermal-cycle sample aging acceleration test is performed, and the acceleration times of artificially accelerating sample aging are obtained according to the coating stress evolutionary physical model and sample stress value-time relation; thirdly, a scratch test instrument is adopted to test the bonding strength of the sample artificially accelerated in aging, the bonding strength-ageing time relation is fit and is drawn into a changing curve, the time corresponding to the intersection point of the changing curve and a timeline serves as the service life 1 of the sample artificially accelerated in aging, and L is equal to sample service life 1* final acceleration times k and serves as the predicted service life. The coating service life prediction method is applicable to the field of coating service life prediction.

According to the present invention, mistaken detection of a gas leak can be prevented even when using an appliance which has been newly installed in a dwelling receiving a gas supply, and whereby a gas leak can be detected rapidly, efficiently and accurately. The characteristics extraction means 5 extracts characteristics of a gas flow including a combination of the instantaneous flow volume data and the instantaneous flow volume time differential value, on the basis of the data obtained by the flow volume measurement means 1, pressure measurement means 2, instantaneous flow volume time differential operation means 3 and pressure time differential operation means 4. The leak detection means 7 compares the characteristics data for respective types of gas appliance or for a gas leak registered in the storage means 6 with the characteristics extracted by the characteristics extraction means 5, and if a matching is not achieved, further judges whether there is a flow volume variation or nozzle variation, and whereby it judges whether there is a gas leak or whether an unregistered appliance is in use. If occurrence of a gas leak, the warning means 9 issues a warning. If an unregistered appliance is in use, the characteristics data forming the basis of the judgment is registered as a new characteristics data in the storage means 6 by the characteristics data registration means 8.

The invention relates to a method for testing the axial fatigue of a flexible plate assembly, which can effectively test the axial fatigue resistance capability of the flexible plate assembly. The method adopts the technical proposal that the method for testing the axial fatigue of the flexible plate assembly is characterized in that a microcomputer is adopted in the test to control an electro-hydraulic servo fatigue testing machine; a displacement sensor, a load sensor and a stress detector are arranged on the electro-hydraulic servo fatigue testing machine controlled by the microcomputer; signals output through the displacement sensor, the load sensor and the stress detector are transferred to a single-chip microcomputer; the signals are output through the single-chip microcomputer, so that an externally connected display displays a load-time curve, a displacement-time curve and a stress-time curve.

The invention relates to a method for acquiring evaluation point stress time domain values by utilizing tower crane operating data, belonging to a method for acquiring the evaluation point stress time domain values by utilizing large-batch load data collected by a tower crane operating data recorder. The invention mainly solves the technical difficulties of small collected data sample size, limited collected structure position and the like in the traditional methods. The method for acquiring the evaluation point stress time domain values by utilizing the tower crane operating data comprises the following steps of: (1) collecting real-time operating data of the hoisting capacity and the like of the tower crane by using the data recorder; (2) processing the collected data; (3) establishing a structural calculation model of the tower crane; (4) calculating the internal force and the stress of structural rod pieces at a certain moment; (5) enabling the stress value at the certain moment obtained in the step 4 added or subtracted by a corrected value to obtain the corrected stress value; and (6) repeating the steps to obtain structural internal force and stress data corresponding to multiple moments, and collating the data into stress spectrum data.