材料的微动疲劳机理及防护措施的研究进展

论述了微动疲劳的概念及对其研究的必要性。对微动疲劳研究的4个主要部分即微动疲劳的机理研究、影响因素、寿命预测和防护方法的发展过程进行了论述,尤其对当前的研究现状及所取得的成果做了重点阐述,并说明了一些尚待研究的问题。从微动疲劳机理研究、研究方法和防护方法等几个方面概述了微动疲劳研究的发展趋势。

热作模具钢SDH3热疲劳机理

采用自约束热疲劳试验方法,对比研究了SDH3与H13钢的热疲劳性能,应用扫描电镜研究了SDH3热疲劳过程中裂纹的萌生和扩展,应用透射电镜分析了SDH3钢热疲劳前后显微组织和结构的变化。结果表明:经常规热处理后,SDH3钢热疲劳性能优于H13钢;对SDH3钢来讲,热疲劳裂纹由三叉晶界处萌生,并沿晶界扩展;SDH3钢的马氏体板条间存在薄膜状残留奥氏体,可有效释放裂纹尖端的应力并阻碍裂纹扩展;热疲劳过程中,基体组织发生回复再结晶,碳化物粒子发生粗化。

hcp金属塑性变形与疲劳机理

概述了ｈｃｐ金属的力学性能与变形行为．重点总结了Ｔｉ的滑移和孪生变形机理，报道了Ｔｉ的疲劳研究新结果．指出，应力轴位向是决定ｈｃｐ金属变形行为的一个重要因素．理论预测和实验分析均表明，在ｈｃｐ金属中，Ｔｉ与Ｚｒ不但具有高的强度，而且具有良好的塑性．

基于IGBT栅极疲劳机理的阈值电压可靠性模型研究

基于绝缘栅双极型晶体管(IGBT)栅极疲劳机理,提出采用阈值电压对IGBT健康状态进行监控的可靠性评估方法。该方法通过研究阈值电压随疲劳程度的变化规律。建立了IGBT阈值电压可靠性评估模型。仿真和实验验证了该模型的正确性与准确性。通过该模型可以对IGBT的健康状况进行准确评估。

发动机活塞销孔座机械疲劳机理的研究

随着发动机爆发压力的不断提升,高功率发动机活塞销孔部位疲劳开裂失效事故频发。为此,本文中采用液压机械疲劳试验系统,对活塞销孔座分别进行"载荷"、"步进载荷"和"步进压力"3种方案的加速疲劳试验,为活塞机械疲劳机理研究提供依据。另外,通过建立活塞销孔寿命公式和评估铝硅合金的裂纹扩展速率,可有效预测活塞的使用寿命。

基于IGBT芯片疲劳机理的关断时间可靠性模型

基于绝缘栅双极型晶体管(IGBT)芯片疲劳机理,提出采用关断时间对IGBT健康状态进行监控的可靠性评估方法。采用理论分析与解析描述相结合的方法,建立了IGBT关断电流下降时间模型,进而通过研究IGBT关断时间特征量疲劳机理,建立了IGBT关断时间可靠性评估模型。仿真和实验验证了该模型的正确性与准确性。通过该模型可对IGBT的健康状况进行准确评估。

驾驶疲劳机理及馈选模式研究

Driving fatigue demonstrates itself in many ways. This paper focuses on the cau ses, process and mechanism leading to driving fatigue and its effects on driving . It narrates the assessment and field test of the driving fatigue. It covers th e following: 1. Mathematic models are made to indicate the function of each factor, direct a nd indirect, and the interaction between individual factors that cause driving f atigue, based on in-depth study of driving behavior. 2. By using transfer function, the paper analyses driving fatigue in a quantiti ed, intensitied and modular way. Based on automatic control theory, driving fati gue is analogized as two parts: inertia and proportion differential. The result shows that the driving fatigue has the general characteristics of two-order sys tem. 3. According to the reliability theory, the paper discusses the compressive eff e ct of driving fatigue factors including their characteristics of fuzziness, rand omicity and interaction. As a result, the variables of the driving fatigue is a restriction condition, which is related to time factor, its relaxation character istic is obvious. While driving fatigue is assessed from the view of men-machin e-environment system, the value of driving fatigue factors are calculated. 4. The paper divides the work into five modes: muscle, sensation, information p rocessing, thinking and creativity modes, with their constituent components. Dri ving fatigue behaviour is mainly composed of the sensation and the operation fat igues. Therefore, a new concept of the driving fatigue formation, accumulation a nd variation is discussed in-depth. 5. Driving fatigue equilibrium testing system produced by our lab is applied in the research. It examines the driving fatigue by tracing the track of the cente r of gravity, which reflects the respective and cooperative capability of sensat ion, center and motor nerve system. Once the driving fatigue occurs, the driver will loose his balance due to the reduction of the above-mentioned capability. Based upon a great number of lab tests and field investigation, corresponding as sessment system is obtained. 6. The driving fatigue feedback and selection mode is built. It starts new idea s on filtering out the dangerous driving group and highly dangerous group, and a dopts the static and dynamic driving fatigue simulation system. In the research, a lot of samples in different age, sex, driving age, intension and workload, ar e investigated in the lab and the field. The analysis results are as follows: (1 ) the maximum continuous driving time is 3 hours; total driving time per day sho uld be less than 9 hours; continuous high speed driving time should be less than 2.5 hours. Other standards such as maximum continuous safety driving time, ave rage daily driving time, and maximum safety driving speed are also recommended. (2) As information becomes more complex and the driver′s capability of reacting and information processing drops, the driving fatigue will be more serious. Fur ther more, capability decreases with age increases. (3) The driver′s capability of equilibrium drops and his driving fatigue becomes serious with the increase of the tilting angle of the test platform and the vision workload. 7. Emphasizing on the driving fatigue effect pattern, the paper researches the driving fatigue′ characteristics and the causes. It brings forward the impulse effect and U-type effect of the information complexity acting on the driving fa tique. It analyzes that the continuity and discrete workload of driving tatigue are the theoretical foundation for optimized matching design in the people-vehi cle-road system and traffic accidents prevention. 8. The vision fatigue testing system is established and the vision tatique stat us is assested. For the first time, according to static and dynamic vision, the driving vision breaks down into four divisions, safety, fatigue, dangerous and c autious. 9. Eight matching modes are provided, which describe not only the relationship between the driving capability and driving

高强度硅基玻璃通信光纤的疲劳机理

用二氧化硅玻璃裂纹生长的实验数据和光纤延时破断的断裂机理，预测高强度硅基玻璃光纤的疲劳行为，结果表明用断裂机理的方法可以描述在室温和潮湿条件下观察到的高强度光纤的疲劳行为。合理解释高强度光纤疲劳行为有利于对光纤表面裂纹扩张速率随外部应力指数增加的断裂速率定律的应用。另外，还提出高强度光纤的断裂机理能区分在更苛刻环境中控制光纤断裂的其它过程。

海上风电灌浆连接段疲劳机理研究综述

海上风机基础灌浆连接段会受到自重及风浪作用产生的轴向荷载和弯矩荷载,由于风浪荷载的时变性,荷载的方向和大小具有随机性,在海上风机20年或25年的服役期内,会承受多达109次荷载效应,疲劳问题突出.对钢结构、灌浆材料、整体结构三方面进行疲劳性能评估,并着重描述了无剪力键与带剪力键灌浆连接段疲劳机理试验研究,最后总结了海上风电灌浆连接段的疲劳机理研究.

牛磺酸代谢及其抗疲劳机理(综述)

本文在查阅近年来国内外许多有关牛磺酸的研究报告的基础上,将牛磺酸代谢及其抗疲劳机理的资料进行收集整理,总结出牛磺酸在人体内的代谢规律及其抗疲劳的五种机理。

高强度二氧化硅玻璃光纤的疲劳机理

本文用二氧化硅玻璃裂纹生长的实验数据和光纤延时断裂机理预测高强度二氧化硅玻璃光纤的疲劳行为，结果表明用断裂机理的方法足以描述在室温和潮湿条件下观察到的高强度光纤的机械特性。合理解释高强度光纤疲劳行为的关键是应用光纤表面裂纹扩张速率随外部应力指数增加的断裂速率定律。本文还指出高强度光纤的断裂机理能区分在更苛刻环境中控制光纤断裂的其它过程。

国内外不锈钢车体点焊、弧焊缝疲劳机理与评估研究

基于不锈钢车体的研发生产过程,分析阐述了疲劳中最为关键的点焊、弧焊缝的疲劳机理。对比分析了国外相关标准中点焊、弧焊缝疲劳评估方法,并依据标准阐述了具体接头类型的评估。

建筑混凝土材料选用及疲劳机理研究

目前,为缓解住房以及商业用房紧张问题,高层建筑出现得越来越多,而且呈现出高度逐年增加的趋势。本文就建筑混凝土材料在选用时的原则以及对应的疲劳机理进行了研究,以期能够科学指导高层建筑施工,延长高层建筑使用寿命。

浅析NiTi形状记忆合金的疲劳机理

由于NiTi形状记忆合金具有可逆的热弹性马氏体相变效应等不同与一般金属的特性,使得其疲劳机理也不同于一般的工程材料。为此,本文侧重分析了温度变化对NiTi形状记忆合金疲劳机理的影响和应力诱发马氏体相变等特征相变过程,以及相关的研究方法与主要结果,将为进一步研究其疲劳过程及增韧工艺提供理论参考依据.

头皮针抗疲劳机理及应用的探讨

探讨了头皮针抗运动疲劳的作用机理,并在训练比赛中进行实际应用,介绍了应 用的方法及手段,并指出与中草药粉配合使用的效果。

疲劳机理新探——Ach量变论的设想

一、问题的提出 运动中,运动员常有“力不从心”之感,特别是在百米,二百米、四百米赛跑的后程,运动员自我感觉很兴奋,很想跑,但腿却抬不起来或频率减慢,一般认为这是疲劳的结果。但是,在生理学中,原有的疲劳理论只提到过在神经与肌肉接点处易疲劳,可惜无进一步的论述。为此,本文拟从分子生物学角度,按剧烈运动导致“运动终板”的一系列生理生化变化,

软-硬互层岩体节理峰前循环剪切疲劳损伤机理研究

三峡库区频发微小地震下岩体节理循环剪切疲劳损伤对边坡动力稳定性具有重要影响。通过室内峰前循环剪切试验和PFC2D细观数值计算,研究了考虑一阶起伏角、含水率、剪切速率、剪切幅度、法向应力及循环剪切次数影响的软-硬互层岩体节理宏细观疲劳损伤机理。研究表明:①岩体节理剪切应力-剪切位移曲线历经初始非线性压剪变形、近似线弹性压剪变形、循环剪切疲劳损伤变形、应力缓升压剪变形、应力陡升压剪变形及应力脆性跌落压剪变形六个演化阶段。②岩体节理峰值(残余)剪切强度和疲劳剪切(法向)位移在相同一阶起伏角、含水率、剪切速率、剪切幅度或法向应力下随循环剪切次增多而分别降低和增大;且其在相同循环剪切次数下随一阶起伏角或法向应力变大而分别增大和降低,而随含水率、剪切速率或剪切幅度变大则分别降低和增大。③宏细观结果总体上吻合较好,且岩体节理细观剪切疲劳损伤裂纹数量随剪切位移变化呈前期微增-陡增、中期缓增及后期陡增-缓增-陡增的发展特征,而其随循环剪切次数变化则呈前期陡增和后期缓增的发展特征。④岩体节理宏细观剪切疲劳损伤典型演化过程可概述为压密-起裂破坏、循环错动-贯通破坏及分离-啃断破坏3个渐进性发展阶段,且宏细观剪切疲劳损伤裂纹近似呈“倒U形”密集分布于岩体节理附近。

基于硅凝胶灌封温循载荷下的键合丝疲劳失效机理仿真分析

针对某型混合集成电路在温度循环试验后出现的硅凝胶灌封区域键合丝疲劳失效,对键合丝的键合强度和疲劳断裂失效进行了试验分析,建立了单根键合丝和硅凝胶局部灌封区域的有限元简化模型,拟合了硅凝胶材料的本构模型参数,基于ANSYS Workbench软件对不同胶体材料参数条件和温循载荷作用下的键合丝应力分布情况进行了热力耦合仿真分析,并基于仿真结果对混合集成电路的硅凝胶灌封工艺进行了优化和加严温度循环试验。仿真和实验结果表明,键合丝第一键合点颈部和第二键合点根部的应力值较大,存在明显的塑性应变,与疲劳断裂失效分析一致;通过减小硅凝胶的热膨胀系数和灌封体积的方式进行工艺优化后,键合丝的应力值显著减小,样品经过温度循环试验后实测良率从167%提升至100%。研究结果对于提高硅凝胶灌封区域中的金丝键合疲劳强度有一定的指导意义。