scholarly journals Based on Damage Mechanics of Ladle Crane Dynamic Reliability Research

2015 ◽  
Vol 9 (1) ◽  
pp. 196-204 ◽  
Author(s):  
Xiaogang Qu ◽  
Gening Xu ◽  
Xiaoning Fan
Keyword(s):  
Damage Mechanics ◽  
Random Variable ◽  
Cyclic Stress ◽  
Structural Dynamic ◽  
Dynamic Reliability ◽  
Reliability Calculation ◽  
Changing Trends ◽  
Physical Experiments ◽  
Distribution Parameters ◽  
The Times

Based on the damage mechanics theory, summarized a new dynamic reliability calculation method with explicit physical meaning, which is used for researching structural dynamic reliability on cyclic stress. By using of the model of stress-strength interference, ignoring the effects of erosion and aging on the strength degradation, only consider that the change of damage leads to the effective stress increasing. Take the intensity as a random variable, view stress as a random variable which was changed with the times of loading, combine physical experiments and simulation with sampling, analog the dynamic reliability curve of the casting crane hook on the beam with the change of loading times. Analyze the changing trends of dynamic reliability under the condition of different distribution parameters of cross section at the 420 °C. The results suggested that the reliability showing a downward trend when the life is about 85%, the dynamic reliability curve has a typical bathtub curve of the latter two steps.

The Reliability of a Component Under Multiple Cyclic Stress Levels With Distributed Cyclic Numbers

2016 ◽  
Author(s):  
Xiaobin Le
Keyword(s):  
Fatigue Life ◽  
Probabilistic Models ◽  
Random Variable ◽  
Fatigue Loading ◽  
Cyclic Stress ◽  
Initial Crack ◽  
Stress Levels ◽  
Single Constant ◽  
Unsolved Issue ◽  
Loading Spectrum

Fatigue damage is initiated through some “defects” on the surfaces of and/or inside the component and induced by the fatigue cyclic loadings. These “defects” are randomly scattered in components, and one of these “defects” will be randomly “activated” and finally developed to become the initial crack which causes the final fatigue failure. Therefore, the fatigue strength is inherently a random variable and should be treated by probabilistic models such as typical P-S-N curves. The fatigue cyclic loading could be presented or described in any form. But the fatigue loading spectrum can generally be grouped as and described by these five models: (1) a single constant cyclic stress (loading) with a given cyclic number, (2) a single constant cyclic stress with a distributed cyclic number, (3) a distributed cyclic stress (loading) at a given fatigue life (cyclic number), (4) multiple constant cyclic stress levels with given cyclic numbers, and (5) multiple constant cyclic stress levels with distributed cyclic numbers. The approaches for determining the reliability of components under fatigue loading spectrum of the models 1∼4 are available in literature and books. But few articles and books have addressed an approach for determining the reliability of components under the fatigue loading spectrum of the model 5. This paper will propose two approaches for addressing this unsolved issue. Two examples will be presented to implement the proposed approaches with detailed procedures.

Dynamic Reliability Evaluation by First-Order Reliability Method Integrated with Stochastic Pseudo Excitation Method

2020 ◽  
pp. 2150024
Author(s):  
Siyu Zhu ◽  
Tianyu Xiang
Keyword(s):  
Random Variable ◽  
Random Excitation ◽  
Pseudo Excitation Method ◽  
First Order Reliability Method ◽  
Dynamic Reliability ◽  
First Order ◽  
Reliability Method ◽  
Uncertain Structure ◽  
Pseudo Excitation ◽  
Excitation Method

The stochastic pseudo excitation method (SPEM), which is based on the principle of pseudo excitation method (PEM), is introduced to represent the randomness of dynamic input in which the amplitude of excitation is adopted as a random variable. Based on the mathematic definition of power spectral density, a physical interpolation of the SPEM is discussed. Even if one random variable is involved in calculation, the effects of the uncertainties are required to be investigated. The SPEM offers a simple but quite effective way to solve the dynamic reliability problem. Through integrating the new algorithm into first-order reliability method (FORM), the dynamic reliability of uncertain structure subjected to random excitation is studied. A linear oscillator with three types of white noise is adopted to verify the SPEM for dynamic reliability of linear random vibration analysis. Also, the accuracy and efficiency of SPEM to handle the multi-degree-of-freedom structure is investigated in this paper.

scholarly journals INSPECTION PROGRAM DEVELOPMENT FOR FATIGUE CRACK GROWTH MODEL WITH TWO RANDOM PARAMETERS/APŽIŪRŲ PROGRAMOS KŪRIMAS NUOVARGIO PLYŠIO AUGIMO MODELIUI SU DVIEM ATSITIKTINIAIS PARAMETRAIS

Aviation ◽  
2008 ◽  
Vol 12 (2) ◽  
pp. 33-40 ◽  
Author(s):  
Yuri Paramonov ◽  
Andrey Kuznetsov
Keyword(s):  
Critical Size ◽  
Fatigue Cracks ◽  
Random Variable ◽  
Fatigue Curve ◽  
Exponential Approximation ◽  
Random Parameters ◽  
Distribution Parameters ◽  
Estimation Of Distribution ◽  
Set Function ◽  
Crack Growth Model

To keep the fatigue failure probability of an aircraft fleet at or below a certain level, an inspection program is appointed to discover fatigue cracks before they decrease the residual strength of some structurally significant item of the airframe lower than the level allowed by regulations. In this article, the p‐set function for random vector, which, in fact, is a generalization of p‐bound for random variable, and minimax approach to the problem of inspection number choice are used. It is supposed that the exponential approximation of a fatigue curve with two random parameters can be used in the interval when the fatigue curve becomes detectable and then grows to critical size. For estimation of distribution parameters, results of an approval test are used. A numerical example is given. Santrauka Šiame tyrime nagrinėtas apžiūrų, skirtų surasti nuovargio įtrūkimus jėginiuose elementuose iki liekamojo stiprumo sumažėjimo žemiau leistinos ribos, programos planavimas. Čia apžiūrų skaičiui nustatyti buvo naudojamas mini-maksimalus statistinis sprendinys ir atsitiktinio vektoriaus p-aibės sąvoka, kuri yra atsitiktinio vektoriaus p-ribos apibendrinta sąvoka. Taikyta prielaida, kad nuovargio įtrūkimo didėjimo kreivę galima aproksimuoti eksponentiškai laiko intervale nuo to momento, kai plyšys tampa matomas ir iki kritinio dydžio. Parametrų pasiskirstymo įvertinimui naudoti bandymo rezultatai. Daroma prielaida, kad jei bandymo rezultatai yra nepatenkinami, tuomet turi būti ruošiamas naujas, labai pagerintas bandomojo gaminio projektas. Pateikti ir skaitiniai pavyzdžiai.

Dynamic Reliability Sensitivity Design of Cutting Tool with Arbitrary Distribution Parameters

2013 ◽  
Vol 816-817 ◽  
pp. 201-205
Author(s):  
Xin Gang Wang ◽  
Bao Yan Wang ◽  
Chang You Li ◽  
Chun Mei Lv
Keyword(s):  
Cutting Tool ◽  
Theoretical Data ◽  
Computational Method ◽  
Design Parameters ◽  
Arbitrary Distribution ◽  
Random Load ◽  
Reliability Design ◽  
Dynamic Reliability ◽  
Reliability Sensitivity ◽  
Distribution Parameters

The variation rules of strength, load, and reliability of cutting tool are studied with a change in time, and a model is established for dynamic reliability of cutting tool under the random load acting. By combining the theory of reliability design with the method of sensitivity analysis, the computational method of dynamic reliability sensitivity design with arbitrary distribution parameter is proposed based on the methods Edgeworth and perturbation, and the problem of dynamic reliability sensitivity design of cutting tool distributed arbitrary distribution is solved as well as the variation rules of dynamic reliability sensitivity are given. The variation of reliability is studied as design parameters change a little, which provides theoretical data for dynamic reliability design of cutting tool

A Statistically Load-Weighted Probabilistic Fatigue Life Model

2008 ◽  
Vol 44-46 ◽  
pp. 51-56 ◽  
Author(s):  
Li Yang Xie ◽  
Wen Qiang Lin
Keyword(s):  
Fatigue Life ◽  
Stress Amplitude ◽  
Random Variable ◽  
Cyclic Stress ◽  
General Situation ◽  
Statistical Average ◽  
Underlying Principle ◽  
Model Configuration ◽  
System Of Units ◽  
Life Model

By interpreting traditional stress-strength interference model as a statistical average of the probability that strength (a random variable) is greater than stress (another random variable) over its whole distribution range, the same model configuration, which was conventionally applied only to the case of same system-of-units parameters (e.g., stress and strength, both are measured in MPa), was applied to more general situation of different system-of-units parameters. That is to say, the traditional model was extended to more general situations of any two variables, as long as one of the variables can be expressed as a function of the other. Further more, the probabilistic fatigue life under random stress can be predicted, with known probabilistic fatigue lives under several deterministic cyclic stress amplitudes and known distribution of the random cyclic stress amplitude. The underlying principle is that the fatigue life under random stress is equal to the statistical average of the fatigue lives under cyclic stress of deterministic amplitudes which can be considered as the samples of the random stress.

The coupling of regenerative processes

1983 ◽  
Vol 15 (3) ◽  
pp. 531-561 ◽  
Author(s):  
Hermann Thorisson
Keyword(s):  
Initial Conditions ◽  
Random Variable ◽  
Total Variation Norm ◽  
Absolutely Continuous ◽  
Moment Conditions ◽  
Common Component ◽  
General State Space ◽  
Regeneration Times ◽  
The Times ◽  
Random Times

A distributional coupling concept is defined for continuous-time stochastic processes on a general state space and applied to processes having a certain non-time-homogeneous regeneration property: regeneration occurs at random times So, S1, · ·· forming an increasing Markov chain, the post-Sn process is conditionally independent of So, · ··, Sn–1 given Sn, and the conditional distribution is independent of n. The coupling problem is reduced to an investigation of the regeneration times So, S1, · ··, and a successful coupling is constructed under the condition that the recurrence times Xn+1 = Sn+1 – Sn given that , are stochastically dominated by an integrable random variable, and that the distributions , have a common component which is absolutely continuous with respect to Lebesgue measure (or aperiodic when the Sn's are lattice-valued). This yields results on the tendency to forget initial conditions as time tends to ∞. In particular, tendency towards equilibrium is obtained, provided the post-Sn process is independent of Sn. The ergodic results cover convergence and uniform convergence of distributions and mean measures in total variation norm. Rate results are also obtained under moment conditions on the Ps's and the times of the first regeneration.

A New Approach for Dynamic Reliability Analysis of Offshore Platforms

2003 ◽  
Author(s):  
Wei-Liang Jin
Keyword(s):  
Reliability Analysis ◽  
Failure Criterion ◽  
Offshore Platform ◽  
Seismic Action ◽  
Offshore Platforms ◽  
Structural Dynamic ◽  
Jacket Platform ◽  
Dynamic Reliability ◽  
Strength Failure ◽  
Offshore Jacket Platform

The theoretical framework of a new dynamic reliability analysis approach for offshore jacket platforms is constructed in this paper. In this approach, the structural dynamic reliability analysis integrates the structural dynamic response theory with the random sampling technique on stochastic variables of the platform. Offshore jacket platform is assumed as a shear type one and is controlled by its horizontal resistance bearing capacity. The failure criterion of offshore platform dynamic reliability includes two aspects: strength failure criterion and deformation failure criterion. The strength failure criterion is based on the double-damage criterion of ultimate dynamic analysis, while the deformation failure criterion depends on the requirement of the offshore oil production. The dynamic reliability formula of offshore platforms is gained on the basis of the first crossing theory. In this paper, uncertainties of offshore jacket platform dynamic reliability subjected to wave hydrodynamic and seismic action are studied respectively. The probabilistic distributions and its statistical characteristics of wave hydrodynamic and seismic action are given on the base of limit bearing state of the platform. The dynamic reliability analysis of an offshore platform W11-4C, located at the gulf of Weizhou, South China Sea, is carried out. Some valuable conclusions are summarized.

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