136 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.

A method for analyzing vortex vibration and fatigue of a depth tension-type vertical pipe, which relates to the field of depth vertical pipe design, comprises the following specific steps of: step 1. obtaining flow field data; step 2. substituting the flow field data into vertical pipe vibration equations 6 and 7; step 3. solving the equations 6 and 7 by using a finite element method, and obtaining calculation results including displacement, velocity, accelerated velocity and stress time interval; and step 4. counting stress cycle number n(i) of an amplitude within a certain time by adopting a rain-flow counting method according to the calculation results, and substituting the n(i) into a fatigue damage calculation formula 8 to calculate the fatigue damage. The method for analyzing vortex vibration and fatigue of the depth tension-type vertical pipe improves the accuracy of stress calculation by adopting a practical pipe-in-pipe model and simultaneously considering direct flow vibration and cross flow vibration.

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 present invention is directed to a number of improvements in methods for reliability simulations in aged circuits whose operation has been degraded through hot-carrier or other effects. A plurality of different circuit stress times can be simulated within a single run. Different aging criteria may be used for different circuit blocks, circuit block types, devices, device models and device types. The user may specify the degradation of selected circuit blocks, circuit block types, devices, device models and device types independently of the simulation. Device degradation can be characterized in tables. Continuous degradation levels can be quantized. Techniques are also described for representing the aged device in the netlist as the fresh device augmented with a plurality of independent current sources connected between its terminals to mimic the effects of aging in the device. The use of device model cards with age parameters is also described. To further improve the circuit reliability simulation, a gradual or multi-step aging is used instead of the standard one step aging process. Many of these features can be embedded within the circuit simulator. A user data interface is also presented to implement these techniques and further allow users to enter their device models not presented in the simulator. For example, a proprietary model of, say, the substrate current in an NMOS could used be with a SPICE simulator employing a different model to simulate the aging of the circuit.

In hydroforming of hollow metal articles in a die, such as pressure-ram-forming procedures, a method of decreasing cycle time of the forming process, while ensuring acceptable product properties and avoiding failures, by modeling the process using finite element analysis to establish a pressure-time history that optimizes the forming operation and applies failure limits to selected variables such as minimum wall thickness or maximum strain rate, and transferring this pressure-time history to a computer controlling the forming process. Thermocouple and / or continuity sensors are incorporated into the die wall and connected to the computer so as to provide active feedback from the die to the control of the process.

The invention discloses a stress-gradient-based method for dividing a coal impact ground pressure danger area. The method comprises the following steps: collecting geological data; simulating a mining value; calculating stress space distribution data and stress time distribution data; dividing an impact danger area; simulating the divided impact danger area according to the above values after a working surface is mined, monitoring stress of the area on line in real time to obtain a stress filed of the monitoring area, repeating the above steps, collecting geological data, dividing, forecasting and early warning the impact ground pressure danger area according to stress data. According to the stress-gradient-based method for dividing the coal impact ground pressure danger area, an impact ground pressure is forecasted and early warned due to a coupling relation existing between the stress gradient of the area and the coal rock impact damage condition; the impact danger area is divided according to the abnormal stress gradient; the method is strong in applicability and high in accuracy, is capable of accurately forecasting and early warning the impact ground pressure danger area and ensuring the property safety of mine and the life safety of workers, and has great significance to the coal mine safety.

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 discloses an anti-collision device for a bridge pier. The anti-collision device comprises an inner buffering cushion, a rotating assembly and an outer anti-collision assembly which are coaxially arranged from inside to outside. The pier is tightly wrapped by the inner buffering cushion, the outer anti-collision assembly can rotate around the axial central line through the rotating assembly, the rotating assembly comprises an inner ring, an outer ring and spherical rolling bodies evenly distributed between the inner ring and the outer ring, the outer ring can rotate relative to the inner ring, and the inner ring can be matched with the inner buffering cushion in a relatively rotating mode. Not only can the aims of prolonging stress time and reducing impact force borne by the pier be achieved through the outer anti-collision assembly, but also the outer anti-collision assembly can rotate around the axial central line through the rotating assembly when the pier is impacted, so that the impact force caused by objects of ships and the like is guided to shift away from the pier, the remaining huge impact force after buffering of the outer anti-collision assembly is shifted away as much as possible, and safety of a bridge is greatly improved. In addition, the inner ring of the rotating assembly further can rotate relative to the lateral face of the outer circumference of the inner buffering cushion to generate a secondary rotating effect, and the effect of shifting the impact force away from the pier is further improved.

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.

The invention relates to a frequency domain analysis method of bridge fatigue life on the basis of a dynamic weighing system. The frequency domain analysis method comprises the following steps: collecting data including the vehicle weight, the vehicle speed and the axle distance of each vehicle which passes through a bridge; calculating the collected data, and carrying out curve fitting; according to a fitting probability density curve, establishing a cellular automata simulation model of the vehicle, and generating a random traffic flow; simulating load time history under different vehicle flow density conditions, and loading the load time history to a bridge influence line to obtain stress time history data; carrying out FFT (Fast Fourier Transform) on the stress time history, obtaining PSD (Power Spectral Density), and calculating relevant parameters; using a Dirlik method to establish an experience form of a PDF (Probability Distribution Function); and calculating residual service life. Calculation time is greatly shortened.

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.

A system and method for accurately estimating the fluctuating pressure loads on components, such as steam dryers, within a BWR steam dome using pressure time history measurements made on components of the BWR facility external to the steam dome. The method uses existing sensors to obtain the pressure time histories. An accurate determination of the fluctuating pressure loads within the steam dome may be obtained by modeling and analyzing the steam delivery system external to the steam dome, including all possible acoustic sources, using acoustic circuit methodology and pressure time histories, and then coupling these results, essentially as part of the boundary conditions, to the solutions for Helmholtz equation within the steam dome.

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 discloses a data processing method based on a separated Hopkinson press bar experiment technique. The method includes the steps: return-to-zero adjustment: performing a wavelike return-to-zero adjustment on a voltage-time curve acquired by a data acquisition unit, and namely, enabling an initial voltage value to keep zero; data smoothing: smoothing the voltage-time curve, and removing abnormal points; waveform selection: selecting head and tail positions of incident waves, reflected waves and transmitted wave, and intercepting waveforms; result calculation: calculating the intercepted waveforms to obtain engineering stress curve, a true stress-strain curve, a stress-time curve, a strain-time curve and a strain rate time curve; data storage: storing all acquired waveforms anddata. The data processing method is applicable to testing data for processing dynamic compressive mechanical properties and has high practicability.

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 present invention relates to shape memory alloy, and is especially the mechanical training method for Ti-Ni shape memory alloy. By means of stress control or strain control mode and through symmetrical pulling and pressing to load to reach the saturated circulation stress times at room temperature. Ti-Ni shape memory alloy with stable martensite phase change temperature is obtained. The present invention has short training time and no damage to the material, can save power and lower training cost, and is suitable for industrial application.

In a Valve, grid-patterned, fixed wall(s) and movable gate plate / plug are built in the hub to control the conduction area. Adjustable spring is applied to push the gate / plug firmly against the fixed wall(s). The structure alteration reduces the travel length required to switch the valve between open and closed states. Since the open / close state is self-sustaining at its last switched state due to friction, no holding energy is required in the actuator. Consequently, a small linear operation solenoid can be used in impulse mode to operate the valve. Due to its low cost, separate solenoids are used to respectively pull open and close the valve in lieu of applying an auto-direction-conversion mechanism. A bimetallic strip contact in series with a resister, packaged together in a thermal isolating tube, is used to prevent the low-duty solenoid from excessive stress-time.

The invention relates to a sealing life prediction method for flexible-packaging lithium-ion batteries and belongs to the technical field of sealing life prediction. The sealing life prediction method includes the steps of determining key degradation mechanism and building a bonding interface cohesive zone model based on consideration of degradation effect; determining a degradation trend that environmental degradation factor changes along with stress by building a degradation accelerating model; calculating to obtain a bonding interface strength time model on condition of different stress according to the initial bonding strength; determining a stress time model based on the function relationship between air pressure and time by a simulation method; and finally, predicting the sealing life of the flexible-packaging lithium-ion battery according to the generalized stress strength theory. According to the sealing life prediction method, the influence to the degradation process within the whole life circle of the outer packaging sealing material from the internal pressure of the lithium-ion battery is taken into consideration, variation trend of the sealing performance of the lithium-ion battery in actual use is simulated, the sealing life of the flexible-packaging lithium-ion battery on different environmental conditions can be calculated in theory, and the method has high engineering applicability.

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.

Disclosed herein is a method for predicting a reliable lifetime of a SOI MOSFET device. The method comprises: measuring a relationship of a gate resistance of the SOI MOSFET device varying as a function of a temperature at different wafer temperatures; performing a lifetime accelerating test on the SOI MOSFET device at different wafer temperatures, so as to obtain a degenerating relationship of a parameter representing the lifetime of the device as a function of stress time, and obtain a lifetime in the presence of self-heating when the parameter degenerates to 10%; performing a self-heating correction on the measured lifetime of the device by using the measured self-heating temperature and an Arrhenius model, so as to obtain a lifetime without self-heating influence; performing a self-heating correction on a variation of the drain current caused by self-heating; performing a self-heating correction on an impact ionization rate caused by hot carriers; and predicting the lifetime of the SOI MOSFET device under a bias. The embodiment of the invention prevents the self-heating effect from affecting the SOI MOSFET device in a practical logic circuit or in an AC analog circuit, which leads to a more precise prediction result.

The invention relates to an oxide semiconductor film transistor trap state density extraction method, belongs to the technical field of a semiconductor device and includes semiconductor and gate insulation layer interface trap state extraction and internal trap state extraction of a semiconductor. The method comprises steps that (1), forward bias stresses with different durations are applied to an oxide semiconductor film transistor, and a corresponding transfer characteristic curve is tested; 2), based on transfer characteristic change rules, a threshold voltage drift mechanism is analyzed, and the change relation of the threshold voltage drift along with the time is determined; 3), if the threshold voltage drift and the applied stress time satisfy an expansion index model, characteristic temperature of an internal trap state of the semiconductor is extracted; and 4), the relationship between sub threshold amplitude and the trap state is utilized, semiconductor and gate insulation layer interface state density and internal trap state density of the semiconductor are extracted. The method is advantaged in that the film transistor interface trap state and the internal trap state can be simultaneously extracted, the calculation process is simpler compared with methods in the prior art, restriction conditions are a few, and the application scope is wide.