一种新的疲劳可靠寿命计算方法

疲劳可靠寿命的计算方法中,存在模型误差、计算烦琐,使可靠寿命计算误差较大等问题·在分析现有问题的基础上考虑疲劳试验数据获得后绘制PSN曲线的实际过程,讨论了PSN曲线的绘制,给出了拟合的曲线方程·利用实际拟合的PSN曲线提出一种新的疲劳寿命计算方法,并由此建立了在恒幅应力作用下机械零件疲劳可靠性寿命预测的模型·利用该模型推导出工作应力服从指数分布、正态分布、对数正态分布和威布尔分布,寿命服从对数正态分布时疲劳可靠寿命的计算公式,供设计计算时使用·与原有计算模型相比,本文给出的计算模型不但消除了系统误差,还使计算大为简便     

有限寿命疲劳可靠度计算的新方法

根据疲劳强度和可靠性理论,利用条件概率给出了有限寿命疲劳强度的可靠度计算公式。当随机变量服从正态分布时,可用数值积分求解;当随机变量不全为正态分布时,可用蒙特卡洛法求解。同时,利用本文给出的公式用迭代法可求出应力为随机变量时的可靠寿命。     

截尾分布的应力寿命模型

根据应力寿命模型和截尾分布理论,建立了截尾分布的应力寿命模型,对工程上常用的金属材料疲劳寿命多服从对数正态分布这一事实,工作应力服从对数正态分布的情况下,推导出疲劳可靠度计算公式·对工作应力服从其它分布的情况也可以利用本文给出的方法推导出·所建模型消除了疲劳可靠性计算的系统误差,使结果更符合实际情况·通过实例计算表明,给出的计算方法是可行的     

载荷共享并联系统疲劳累积损伤可靠性模型

针对存在载荷传递、分担的并联系统,传统的并联系统可靠性模型已不适用.为了有效处理载荷共享并联系统的可靠性问题,首先分析了并联系统的相关失效,并分步计算并联系统可靠度,应用全概率公式和Miner理论对并联系统进行了疲劳累积损伤可靠性建模.其次,运用Monte Carlo方法对零件寿命服从Weibull分布的并联系统可靠度进行了模拟计算,同时对零件寿命服从对数正态分布的并联系统可靠度显式计算公式进行了推导.建立了变应力作用下并联系统疲劳累积损伤可靠性模型.     

滚轮接触疲劳可靠性分析

针对工程上典型运动机构中常用的滚轮滑轨,在已知滚轮额定载荷、额定失效概率及其对应的额定寿命的前提下,基于Basquin关系,考虑滚轮疲劳寿命服从对数正态分布,建立了滚轮接触疲劳寿命可靠性分析模型,提出了一种滚轮在实际使用环境中不同使用寿命下计算滚轮失效概率的可靠性分析方法。最后,结合飞机型号进行了实例计算,其计算结果可为确定滚轮维修及更换周期提供有益参考。     

基于模糊优化的零部件疲劳寿命可靠性分析

针对服从对数正态分布的疲劳寿命,进行了模糊优化意义上的零部件疲劳寿命可靠性分析,计算了基于优化模糊λ－截集水平的疲劳寿命可靠度。     

试验与服役数据融合的飞机结构安全寿命分析

针对飞机结构安全寿命分析中样本容量偏少的问题,综合考虑结构分散性和载荷分散性的飞机结构疲劳寿命是否服从对数正态分布或威布尔分布的情况,根据等损伤原理,将服役飞机实际飞行小时数等效转化为在同一试验载荷谱下的当量飞行小时数,以实现飞机结构试验疲劳寿命与服役使用数据的融合,采用随机右截尾情形下的极大似然估计方法估算疲劳寿命分布函数的参数,进行飞机结构安全寿命分析;最后以飞机结构疲劳寿命服从对数正态分布为例进行了算例分析,分析结果表明:在相同的可靠度和置信水平下,利用试验数据与服役使用数据融合方法可以显著增大样本容量,从而充分挖掘飞机结构可靠性的储备。     

Г—minimax估计在可靠性理论中的一个应用

本文在先验分布满足一些矩限制Г时，给出了寿命服从对数正态分布时平均寿命的Г－ｍｉｎｉｍａｘ估计。     

服役海底管道钢疲劳可靠性试验与海底管道寿命预测

针对波浪力下海底管道悬空段的疲劳寿命问题,从某服役X60钢海底管道悬空段上取样进行拉-拉成组多级疲劳试验,获得服役X60钢海底管道试件在不同应力水平下的疲劳寿命及其概率统计分布,利用参数假设检验法确定X60钢管道试件的疲劳寿命分布特征,由此外推出不同存活率下的疲劳对数寿命与等效循环应力之间的线性关系式.通过引入"疲劳极限复合修正系数"和"等价非对称循环度系数"对X60钢试件的P-S-N曲线进行修正,得出X60钢海底管道悬空段的疲劳寿命预测公式.结合试验结果分析表明:X60钢海底管道试件的疲劳寿命服从对数正态分布;疲劳对数寿命与等效循环应力之间近似为线性关系;海底管道疲劳寿命预测公式计算结果与试验数据吻合良好.     

基于加速寿命试验的IGBT模块寿命预测和失效分析

针对IGBT可靠性分析与寿命预测问题,提出了一种利用加速寿命试验对IGBT模块使用寿命进行预测的新方法.论述了加速寿命试验的原理与方法,提出采用对数正态分布描述IGBT模块的寿命分布,以阿伦尼斯模型为基础,利用极大似然估计法对试验数据进行统计与分析,建立了IGBT模块的寿命预测模型,实现了对正常应力下模块寿命的科学估计,并对IGBT模块的失效机理进行了详细分析.结果表明,IGBT模块寿命服从对数正态分布,纠正了以往认为其服从Weibull分布的错误思想.随结温差和平均结温的增大,IGBT模块寿命逐渐减小,并且当模块到达寿命终点时,其最终失效形式为热失效.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

正~~     

Brief Introduction to “Journal of Jilin University( Science Edition) ”

<正>"Journal of Jilin University(Science Edition)"is a comprehensive academic journal in the fields of science sponsored by Jilin University and administrated by the Ministry of Education of the Peoples Republic of China.The journal started publication in 1955.The original name at starting publication was"Journal of Natural Science of Northeast People University",which was changed into"Acta Scientiarum Naturalium Universitatis Jilinensis"in 1958 owing to the name change of the university.The present journal name has