38 results about "Limit state function" patented technology

The invention provides an active reliability analyzing and evaluating method for highly-reliable mechanical products. The active reliability analyzing and evaluating method for the highly-reliable mechanical products includes: firstly, establishing ultimate state functions of mechanical products, utilizing a Monte Carlo simulation method to produce sample points conforming to parameter distribution, utilizing a Kriging meta-model to simulate the ultimate state functions, improving simulation precision and confirming an optimal sampling radius by automatically updating DOE (design of experiment), constructing important sampling density functions, producing random sample points through the important sampling density functions, updating the DOE continually, then extracting radius random sample points obeying chi-square distribution, confirming failure probability and failure coefficient of variation of the mechanical products, and limiting whether updating finishes or not by the failure coefficient of variation so as to obtain reliability of the mechanical products finally. The active reliability analyzing and evaluating method for the highly-reliable mechanical products has the advantages of high efficiency, good robustness and high simulation precision, comprehensive design and analysis of rail wear life and reliability to spatial mechanisms are achieved, and the active reliability analyzing and evaluating method for the highly-reliable mechanical products is significant to reliability design technology engineering of complex mechanisms of aerospace equipment.

The present invention discloses a method for calculating the rock failure probability in a rock slope. The method comprises: step 1, formulating a calculation parameter of a rock slope; step 2, establishing a limit state function of the rock slope; step 3, discretizing the rock slope by using rigid block elements; step 4, establishing an upper bound linear programming model for solving the rock failure probability; and step 5, solving the upper bound linear programming model by using a Monte Carlo method, and calculating the rock failure probability. According to the method disclosed by the present invention, a two-dimensional rock slope is taken as a research object, the upper bound theorem of plastic limit analysis, and the rigid block element discrete technology, the linear programmingmethod and the Monte Carlo method are combined to establish a mathematical programming model of the upper bound method for calculating the rock failure probability; and the model can be effectively used to calculate the rock failure probability and obtain the failure probability and the corresponding failure mode of all rock blocks in the rock slope.

The invention discloses a structural reliability method based on dynamic weight response surface under mixed uncertainty. The invention is applied to the field of reliability technical field, and aimsat structural reliability problems under mixed variables. The method comprises the following steps of determining a fitted sample of a current iterative response surface; fitting and getting the response surface of the current iteration by weighted least squares; getting the reliability design point of the current response surface according to the hybrid variable decoupling method; stopping the iteration, when the value of the random variable part of the reliability design point obtained by two adjacent iterations satisfies the convergence criterion; calculating the failure probability of thestructure by Monte Carlo simulation according to the response surface obtained from the last iteration. The invention constructs the response surface, so that the limit state function in the standardnormal space is explicitly approximated in the form of a quadratic response surface, which facilitates subsequent reliability analysis. And a double weighting mechanism is introduced to effectively improve the accuracy and computational efficiency of the response surface method.

The present invention relates to the technical field of probability statistical analysis and prediction of concrete temperature fields, and discloses a bridge-ballastless track structure extreme temperature prediction method and system, so as to avoid subjectivity of the conventional experience distribution method and the cumbersome derivation process of the first-order second-moment method and to obtain a relatively preciser temperature extremum in the case of a certain amount of data. The method disclosed by the present invention comprises: forming a statistical sample by means of measured bridge-ballastless track structure temperature data; calculating firt to fourth moments of the stastical sample to obtain a statistical feature of the sample; constructing virtual distribution by means of standard regular distribution to indirectly describe a distribution condition of the sample; solving a key parameter and feature estimation of the virtual distribution; constructing an extreme state function considering an extreme temperature, and giving an exceedance probability; and calculating first to fourth moments of the extreme state function by means of a reliability indicator formula, and reversing an extreme temperature value corresponding to the exceedance probability and giving a corresponding reoccurrence period.

The invention discloses a fuzzy intelligent multiple response surface method for a blade reliability optimization design. The method specifically comprises the processes of comprehensively considering joint action of non-linear material attribute and mechanical load of a blade material and finding out the maximum output response point of the blade by statics analysis; selecting the input random variable, extracting an input random variable sample by applying a Latin hypercube sampling (LHS) technology and solving finite element basic equation for each sample to obtain corresponding output response; constructing a fuzzy intelligent multiple response surface function (FIMRSF) to finish reliability sensitivity analysis of the blade structure; establishing a fuzzy reliability optimization design model (FRBDO) by taking a high sensitivity parameter as a design variable; and performing fuzzy reliability optimization design by replacing the limit state function of the blade structure with FIMRSF and solving the FRBDO model by means of a multi-target genetic algorithm. The method disclosed by the invention is a quick and efficient multi-failure mode structural reliability optimization design method.

The invention provides a method for synthesizing for non-probability time-varying reliability of a link mechanism containing a hinge gap. Firstly, according to the rod length and initial position of the link mechanism and specific characteristics of the hinge gap, a mathematic expression of a mechanism motion error function is obtained in combination with a vector method; secondly, rod length and hinge uncertainty information is introduced into an interval process model for establishing mechanism motion errors, and the time-varying uncertainty characteristic quantity of a mechanism motion precision limit state function is quickly calculated; thirdly, based on the first crossing theory and the dispersed strategy, index definition and solution of crossing failure possibility in any micro cyclic loading increment segment are completed, and then a time-varying reliability model is constructed; finally, the non-probability time-varying reliability index of motion precision serves as a target, non-probability reliability of mechanism existence conditions serves as a constraint condition, and synthesis of the non-probability time-varying reliability of the link mechanism containing the hinge gap is completed. In the process of mechanism synthesis, synthetic effects of uncertainty on the mechanism in a motion period are reasonably represented, and the time-varying reliability of the mechanism can be effectively improved.

The invention discloses a reliability analysis method for a heat transfer system containing fuzzy parameters. The method comprises the following steps that: carrying out the finite element modeling of a heat transfer system; utilizing a fuzzy variable to represent uncertain input parameters, and establishing the fuzzy finite element equation of the heat transfer system; selecting a cut set level, and converting the fuzzy variable into an interval variable so as to obtain one group of interval finite element equations; utilizing a perturbation theory to solve the interval finite element equations to obtain the upper and lower bounds of interval temperature response; according to the temperature response, establishing an ultimate state function which represents system reliability, and calculating the upper and lower bounds of the ultimate state function; utilizing an interval sorting method to process the ultimate state function to obtain an interval reliability index under each cut set level; and carrying out integral computation on the interval reliability index under the cut set level, and finally, obtaining the fuzzy reliability index of the heat transfer system. On a premise that calculation efficiency is guaranteed, by use of the method, the fuzzy reliability calculation accuracy of the heat transfer system can be effectively improved, which can not be realized by general commercial software.

The invention discloses a gear reliability analysis method. According to the parameters of the gear, a function function corresponding to a failure mode of the gear is constructed. The function function is used for expressing the relationship between the limit state function of the gear and the gear parameters under the failure mode. The limit state equation of the function is obtained, and the mean and standard deviation of the limit state equation are obtained. A reliability index of the gear in the failure mode is obtained by using an improved first-order second-moment method and the mean value and the standard deviation. The fourth-order moment method and the reliability index are used to obtain the failure probability of a single failure mode. The gear reliability analysis method provided by the invention is low in computational complexity and is high in precision.

The invention discloses a method for determining proportion of influence of space manipulator parameters on movement reliability, comprising the steps of: firstly, obtaining influence factors of a space manipulator on movement reliability; secondly, establishing a limit state function which aims at representing minimal operating space pose deviations of the space manipulator; then establishing response surface function representing relations between the influence factors and the pose deviations; and at last working out the movement reliability sensitivity of each influence factor. According to the method provided by the invention, the coupling relation between the on-orbit task constraint and each influence factor of the space manipulator is comprehensively considered, the problem about multidimensional integral continuous partial derivatives during the analysis process of the movement reliability sensitivity is avoided, coupling and nonlinearity among the influence factors are reduced, the problem that the movement reliability analysis needs a lot of samples is avoided, the computing efficiency is improved, and the requirement on on-orbit real-time application is met.

The invention discloses an in-service structure optimal maintenance design method based on convex model time-variation reliability. The method comprehensively considers the influence of uncertainty under the time effect to the in-service structural mechanic behavior. At first, time-variation uncertainty parameters are characterized by defining the convex model process, and the explicit expression of the limit state function characteristic quantities is deduced; based on the spanning theory of vibration mechanics and the structure non-probabilistic reliability model, the time-variation reliability index of the in-service structure based on the convex model is defined; furthermore, by taking the relationship between the maintenance cost and the service life of the structure into account, an in-service structure reliability design model is built based on the optimal maintenance decision; and by taking the reliability as the optimization target and maintenance time as the design variable, and repeating iterations through an intelligent optimization algorithm, the optimal maintenance and reinforcement design scheme for the drafted service period structure can be finally obtained.

The invention discloses a method for determining a design coefficient of a reinforced thermoplastic pipe (RTP). The method comprises the following steps: analyzing an internal pressure load, bending load, external pressure load, axial tension load, temperature difference load and combined load of the RTP, and analyzing the load resistance of the RTP; establishing a limit state function, load probability model and resistance probability model under different load conditions; determining an average value, standard difference and variation coefficient of the loads and the resistance; giving a target reliability index, and determining a partial load coefficient and partial resistance coefficient by virtue of a FORM method; determining the design coefficient by virtue of an LRFD method. The method has the beneficial effects that the loads of the RTP are classified into the internal pressure load, the bending load, the external pressure load, the axial tension load, the temperature difference load and the combined load; the target reliability index is combined to form a calculation method for the design coefficient by establishing a limit state equation and establishing the probability models, so that a foundation is laid for the future engineering application of the RTP to an oil and gas transmission pipeline.

The invention provides a complexity reliability calculation method based on an optimized learning machine. According to the method, firstly, a reliability important influence region is determined; then, new samples are selected to be calculated in a purposive way in the region according to a certain strategy, so the calculation times of a limit state function is reduced to the maximum degree, meanwhile, the limit state function is cyclically rebuilt at high efficiency and high precision, finally, the simulated reliability calculation is fast carried out on the basis of a rebuilt approximate limit state function model by using an important sampling method, and the goal of obtaining high-precision reliability calculation results by calculating the limit state function in fewer times is finally achieved. The defect that the calculation precision and the calculation efficiency cannot be simultaneously considered in the conventional reliability calculation method is overcome, so the practicability of the method in the engineering reliability analysis is improved.

The invention provides a time-variant reliability sensitivity analysis method and device. The method comprises the following steps: step 101, n-order PCE (Polynomial chaos expansions) operation is performed on a motion mechanism, and the MRF (maximum resistance force) of the nth order of the motion mechanism and an nth-order PCE functional expression are obtained, wherein n is a positive integer larger than 1; step 102, estimated MRF obtained on the basis of simulation model estimation is acquired; step 103, whether the absolute value of the difference between the nth-order MRF and the estimated MRF is smaller than a preset threshold is judged; step 104, when the absolute value of the difference between the nth-order MRF and the estimated MRF is smaller than the preset threshold, a time-variant limit state function is constructed according to the nth-order PCE functional expression, time-variant reliability sensitivity of the motion mechanism is obtained, so that time-variant reliability sensitivity analysis based on the long-period degeneration motion mechanism is realized, and support is provided for reliability-based design optimization of the long-period degeneration motion mechanism.

The invention relates to the technical field of pipeline evaluation, and discloses a method and a system for calculating a gas pipeline completeness evaluation period. According to the method and the system, a reliability index after the improvement of a strength design coefficient is calculated by establishing a gas pipeline corrosion thinning ultimate-state function, a mean value function of the gas pipeline corrosion thinning ultimate-state function, and a standard deviation function of the gas pipeline corrosion thinning ultimate-state function; a reliability index reduction ratio is further obtained through calculation; finally, the correction adjustment is implemented on the gas pipeline completeness evaluation period with a known strength design coefficient, so that the gas pipeline completeness evaluation period with a higher strength design coefficient is obtained; therefore suggestions are provided for the completeness management and maintenance of pipelines; the demands of gas pipeline completeness evaluation are met.

The invention discloses an interval model time varying reliability based on active service structure optimized maintenance design method taking into account dynamic uncertainty. According to the invention, influence on mechanical behaviors of an on active service structure by time varying uncertainty is taken into account comprehensively. First, through defining the uncertainty characteristics ofquantified basic variables of a non-probability interval model and through uncertainty propagation analysis, a limit state function of the structure taking into account a static-dynamic hybrid uncertainty condition is deduced; reliability indexes of the on active service structure based on the non-probability interval model are established based on a first-time passage theory; establishment of a maintenance cost model under a non-probability frame is tried by taking a maintenance cost formula proposed by Frangopol as the basis and an optimized maintenance design method for the on active service structure is constructed; the optimal scheme for maintenance in the service cycle of the on active structure is finally determined through repeated iteration of particle swarm optimization by takingthe structure maintenance total cost as the optimization target, taking the maintenance frequency, the type and the corresponding time points as design variables and taking the structure reliabilityas optimization constraints.

The invention discloses a method for calculating the reliability of long-span bridge members under the action of a windmill load. The method comprises the steps of firstly, determining parameter typesof a target bridge structure limit state function, collecting parameter data, randomly grouping the collected data, and performing normalization processing on the data; secondly, establishing an optimized limit state function fitting program based on a thought evolution algorithm and a neural network, performing calculation by adopting the thought evolution algorithm in the program to obtain an optimal individual as an initial weight value and a threshold value of the next-step calculation, substituting input data of a test set into a trained neural network for performing simulation prediction, comparing load effect data obtained by prediction with expected data, calculating an error, and evaluating a fitting effect of the obtained neural network; and finally, combining the trained network with a Monte Carlo method optimized by a particle swarm algorithm, thereby establishing an optimized reliability calculation method for finishing the calculation of the reliability of the long-spanbridge members under the action of the windmill load.

The invention discloses a non-backfill arch open-cut tunnel structure probability reliability degree design method under fallen rock impact. The method comprises the steps that a limit state function of an arch open-cut tunnel structure ultimate bearing capacity model, an impact load model of an arch open-cut tunnel by fallen rocks and a non-backfill arch open-cut tunnel structure under the fallen rock impact is built; according to the limit state function, a JC method of a first-order quadric moment method is adopted to calculate a structure reliability index of the arch open-cut tunnel; when the structure reliability index is equal to a target reliability index, and the structure reliability index is larger than the target reliability index and the value which exceeds the target reliability index is smaller than or equal to a set threshold valve, the arch open-cut tunnel structure probability reliability degree which is designed by a selected structure design parameter meets design requirements; when the structure reliability index is smaller than the target reliability index, and the structure reliability index is larger than the target reliability index and the value which exceeds the target reliability index is larger than a set threshold value, the structure design parameter is adjusted until the arch open-cut tunnel structure probability reliability degree which is designed by the selected structure design parameter meets the design requirements.

The invention discloses an expansion line sampling method for efficient structure failure probability function solving, and relates to structure reliability optimization design. The method comprises the steps of constructing an auxiliary sampling density function: for a design variable situation, selecting the proper auxiliary sampling density function phi(x); solving a corresponding important direction: when variables obey phi(x) distribution, solving the corresponding important direction alpha; extracting variable samples: generating sample points {x(j):j=1,2,...N} corresponding to the variables according to the variable distribution phi(x); calculating a corresponding intersection point: calculating the intersection point, defined in the specification, corresponding to a lower limit state function of line sampling through three-point quadratic interpolation; and calculating failure probability function estimation: according to an intersection point value, calculating the failure probability function estimation by reference to a formula.

The invention discloses a bridge crane reliability optimization design method which comprises the following steps: S1, defining uncertain structure parameters in a crane, and describing the uncertainparameters as interval variables; S2, establishing a limit state function according to the structural failure form, and solving a reliability index in the optimization model by adopting a Vparalove function in MATLAB based on an interval analysis method; S3, introducing a non-probabilistic reliability index, and establishing a non-probabilistic reliability optimization design model by taking a given required reliability index as a constraint condition; S4, solving an optimization problem;. According to the method, the reliability index can be effectively, quickly and accurately solved; Secondly, the common defects of low iteration rate, low optimization precision, large storage space and the like of an optimization algorithm in the actual solving process are considered; On the basis of researching a traditional moth flame algorithm, the method is effectively improved, and the convergence rate and the convergence precision of the outer layer optimizer are remarkably improved. And the method has an important value in structural reliability optimization design in engineering practice.

According to a non-probabilistic interval interference time-varying reliability analysis method provided by the invention, the time-varying reliability of a structure can be evaluated without specificdistribution of parameters, and a reference is provided for structural time-varying reliability analysis. Firstly, based on a non-probability interval theory, structural stress and strength at any moment are converted into an interval variable form; secondly, in combination with a stress-strength interference theory, structural stress and strength interval are converted into a standardized interval, and a relationship between a structural limit state function and the standardized interval is changed at different moments; and an interval interference time-varying reliability index eta belonging to [0, + infinity] is defined according to the relationship between the structure limit state function and the standardized interval. Wherein eta = 0 indicates that the storage tank is in a failurestate, 0 < eta < 1 indicates the reliability of the storage tank, and eta > = 1 indicates the safety margin of the storage tank. Finally, comparative analysis is made with an interval reliability andstress-intensity interference reliability method to verify the effectiveness of the non-probabilistic interval interference time-varying reliability evaluation method provided by the invention.