Fatigue Loading and Life Prediction in Three Fretting Fatigue Fixtures

Three fixtures for conducting laboratory fretting fatigue tests are described and their respective testing methods and the results of the analysis are compared. Each of these fixtures has been used to investigate the effects of various parameters of interest in fretting fatigue. These fixtures include a unique apparatus in which all load applied to the specimen is transferred to the fretting pads, an apparatus similar to many found in the literature where partial load transfer occurs across the pads, and a simplified dovetail fixture in which the clamping load, P, and the shear load, Q, are varied in phase. Select test conditions from prior experiments performed on identical material and resulting in similar lives ranging from one to ten million cycles from these fixtures are identified. The various testing conditions were used to compute the unique stress field for each case. The resulting contact stresses were used to calculate crack initiation based criteria, and to calculate stress intensity factors. The three fixtures were shown to be able to accommodate a range of loads, fretting pad contours, and specimen geometries that produced a variety of stress fields. A crack-initiation-based criterion was shown to predict the failure lives of thinner specimens accurately. The stress intensity factor calculations showed the possibility of a crack arresting for a stress field that decays rapidly and the possibility of a local minimum for K as a function of depth. The fixtures are shown to be complementary in generating data for development of robust fretting fatigue models that use these criteria.     

THE NBELC AND NWELC CLASSES OF LIFE DISTRIBUTIONS

ＴＨＥＮＢＥＬＣＡＮＤＮＷＥＬＣＣＬＡＳＳＥＳＯＦＬＩＦＥＤＩＳＴＲＩＢＵＴＩＯＮＳ￥ＣＡＯＪＩＮＨＵＡ；ＷＡＮＧＹＵＥＤＯＮＧ（ＩｎｓｔｉｔｕｔｅｏｆＡｐｐｌｉｅｄＭａｔｈｅｍａｔｉｃｓ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅ，Ｂｅｉｊｉｎ...     

含间断项的非线性积分、微分方程极解的存在性

在不涉及紧型条件和耗散型条件的情形下，证明了Ｂａｎａｃｈ空间中含间断项的非线性积分、微分方程极解的存在性，推广了文［１］、［２］和［３］中的结果．     

Time-resolved study of the AΠ state of CaH by laser spectroscopy

A time-resolved experiment on the A²Π state of gaseous calcium hydride has been performed by applying laser spectroscopic methods. The following zero-pressure lifetime was obtained for the CaH A²Π state: τ_υ´=0 = 33.2 (±3.2) ns and τ_υ´=1 = 33.7 (±5.2) ns. The lifetime was found to be the same for the A²Π_½ and A²Π_3/2 states.     

水杨醛缩邻氨基苯酚的合成及铅荧光反应的研究和应用

合成了荧光试剂水杨醛缩邻氨基苯酚,在NH4Cl-NH3·H2O缓冲溶液介质中,铅离子能使其荧光强度增强,荧光增强的程度随铅离子含量的增加而增大.据此建立了测定痕量铅离子的直接荧光分析方法.并研究此试剂与铅荧光反应的最佳条件,在λex/λem=386/502nm处,铅离子含量在0.0-200.0μg·L-1范围内与△F呈良好的线性关系,方法的检出限为1.62μg·L-1.该方法操作简便快速,具有极高的灵敏度.用于蓄电池废水中铅含量的测定,结果与火焰原子吸收光谱法基本一致,效果令人满意.     

系统健康管理中的寿命模型仿真研究

在航空、航天、通信等领域,高可靠性和长寿命设计的产品所占比重逐渐增大。性能退化状态评估和剩余使用寿命预测技术在提高该类产品安全性和维护效率、降低全寿命周期成本等方面意义重大。针对当前国内健康管理研究中缺乏寿命及可靠性基础数据的现状,介绍了系统寿命预测的典型过程,重点分析了寿命模型研究和仿真中存在的若干问题,旨在建立实现简单且与实际系统运行过程相似度高的寿命模型的建模方法,为后续系统性能状态评估提供有效的数据支持。     

基于数据驱动的卫星锂离子电池寿命预测方法

锂离子电池由于具有工作电压高、体积小、质量轻、比能量高、寿命长和自放电率小等优点,成为 替代传统镍氢、镍镉电池的第三代航天器用储能电源。寿命预测是锂离子电池健康管理的重要方面,是掌 握电源衰退的重要手段。锂离子电池剩余使用寿命预测问题已成为电子系统健康管理领域的研究热点和具 有挑战性的问题之一。本文基于NASA埃姆斯中心的锂离子电池地面试验采集数据,首先分析了3种类型 的锂离子电池预测方法,之后重点研究了几种有效的数据驱动的锂离子电池寿命预测方法,并对各种预测 方法的效果进行了评价。实验结果表明,本文提出的方法能够有效的用于基于数据驱动的锂离子电池寿命 预测中,具有较强的工程应用价值。     

Green chemistry and sustainability metrics in the pharmaceutical manufacturing sector

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The enormity of the zinc deficiency problem and available solutions; an overview

The societal cost of micronutrient deficiency (MND) or the “hidden hunger” is in millions of dollars/year, reducing the GDP of some countries by as much as 11%. Zn is an important micronutrient for both plants and animals. An estimated 17% of the world population, or around 1.1 billion people, are at the risk of zinc (Zn) deficiency. The deficiency has been related to adverse pregnancy outcomes, stunted growth, premature deaths, immune system dysfunctions, neuro-behavioral disorders, and recently with the failure to recover from COVID-19. These health risks associated with Zn deficiency have compelled FAO and WHO to recommend Zn fortification of diet. Correcting Zn deficiency is a challenge due to several reasons. Close to half of the agricultural soils are Zn deficient, and chemical Zn fertilizers are costly and ineffective. Developing Zn-rich crops through plant breeding and genetic engineering is challenging. Zn-dense diet is costly and cannot be implemented in the low-income region most affected by Zn deficiency. Lack of consensus among regulatory bodies on defining and diagnosing Zn deficiency in plants and Humans. Awareness and other sociocultural issues. Among the most important available solutions are zinc biofortification of the cereal crops, use of zinc biofertilizers, development of Zn-efficient crops with reduced phytate content. The use of Zn supplements, dietary modification, and diversification, especially with fish, are proposed as the most accessible and affordable solutions. Awareness programs in areas suffering the most from Zn deficiency are required. Despite the suggestions from FAO and WHO, global efforts to combat Zn deficiency matching those for combating diseases like HIV are not in place. Coordinated efforts of the international community, especially policy-makers, agricultural scientists, dieticians, physicians, and others, are required to address the issue of hidden hunger.