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霍尔电流传感器的退化机理复杂,退化具有波动性,非线性等特征,对高可靠、长寿命的霍尔电流传感器准确进行寿命预测是一个难点。本研究通过对霍尔电流传感器进行加速退化试验,利用性能退化数据,预测了传感器的可靠性及寿命。首先分析了霍尔电流传感器工作原理和退化机理,确定将输出电流漂移作为其性能退化参数。然后由试验数据推导得到Wiener过程漂移参数和扩散参数的约束关系,结合阿伦尼乌斯模型推导得到漂移参数和扩散参数的加速模型。从而得到霍尔电流传感器在正常工作温度条件下的可靠度函数和可靠寿命。将结果与基于加速退化轨迹法的可靠性预测结果进行对比,验证了本方法的可行性。 相似文献
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在向无铅化过渡的过程中,封装材料与工艺改变所带来的最突出的问题之一就是无铅焊点的可靠性问题。由于焊点区非协调变形导致的热疲劳失效是电子封装焊点的主要失效形式。到目前为止,仍无公认的焊点寿命和可靠性的评价方法。本文采用统一型粘塑性本构模型描述SnAgCu焊点的变形行为,在对焊点可靠性分析的基础上采用基于能量的寿命模型进行焊点寿命预测;在有限元方面采用子模型的处理技术,并采用节点平均化以及体积平均化方法计算寿命模型相关参数。力图从理论方面和有限元处理技术方面改进以达到提高焊点寿命预测效率及预测精度的目的。 相似文献
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完成了依据有限元疲劳分析为基础的传感器寿命预测研究工作。阐述压力传感器工作原理,定义影响系统寿命的参数组,既包含力学环境参数,亦包括材料属性、几何形式等结构参数。针对不同参数属性,依据疲劳强度计算需求,构建有限元数值计算模型;根据影响传感器寿命的传感单元单晶硅S-N(应力-循环)分布,完成变载荷输入条件下模型疲劳分析,依据数值计算结果完成该压力传感器寿命预测工作。结果表明:压力传感器使用寿命在7.068E8次数以上。本课题研究提出的新方法,摆脱了传统依靠试验完成多种材料组成结构体的疲劳分析及寿命预测窘境,具有通用性。 相似文献
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加速寿命试验是预测产品可靠性的重要方法,在实践中得以广泛应用。本文简要分析加速寿命试验的原理,并探讨它在电子产品中的应用。 相似文献
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高分子材料在使用过程中,由于受各种环境因素作用,会逐步出现性能下降,甚至丧失使用价值的老化现象,不仅造成资源浪费,更形成安全隐患。为应对老化问题,研究者以各种宏观性能或微观结构、组份的变化来表征老化过程,针对高分子材料的环境适应性开展了大量研究工作,并在此基础上提出了不同的老化机理和服役寿命预测方法。从高分子材料老化过程表征的视角,综述了近年来高分子材料服役寿命预测方法的最新进展。 相似文献
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针对安装于某型固体火箭发动机的天然橡胶、硅橡胶、氟橡胶三类材料开展加速老化试验,获得贮存质量变化规律,并对其寿命退化趋势对比分析。根据三类材料装配时所受不同敏感应力的特点,分别设计压缩永久变形试样、哑铃型试样开展恒定应力加速试验方法对比研究。通过对各力学性能测试数据进行退化分析,评估得到天然橡胶、硅橡胶、氟橡胶的库房贮存性能退化规律和常温(25℃)退化速率,并科学比较了三类橡胶退化规律的差异性。对比评估过程,给出性能数据的线性相关性差别,提出了不同材料最合适的评估模型,为其他型号相似产品的寿命预测提供支撑。评估结果,获得寿命薄弱环节,从而帮助型号应用时改进设计、增大失效判据,有助于延长导弹的贮存寿命。 相似文献
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首先陈述了贮存寿命加速试验的基本原理,介绍电磁阀的结构组成,分析了失效模式和失效机理后,采取恒定应力加速试验方法,然后运用极大似然估计和最小二乘法对数据进行处理,最后得出其贮存寿命等结论。 相似文献
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某电容器加速贮存寿命试验设计研究 总被引:1,自引:0,他引:1
加速贮存寿命试验设计是设计一个最优的试验指导方案.一个好的试验方案可以提高模型参数估计精度和寿命外推的准确性,可以缩短试验时间、提高试验效率.本文在探讨该电容器的失效机理分析的基础上,在从应力加载方式、应力类型、水平、参试样品、截尾方式、测试、判据等多方面开展试验方案的设计. 相似文献
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Concerns over non-renewable fossil fuel supply and climate change have been driving the Renaissance of bio-based materials. To substantiate environmental claims, the impacts of bio-based materials are typically quantified by applying life cycle assessment (LCA). The internationally agreed LCA standards provide generic recommendations on how to evaluate the environmental impacts of products and services but do not address details that are specifically relevant for the life cycles of bio-based materials. Here, we provide an overview of key issues and methodologies explicitly pertinent to the LCA of bio-based materials. We argue that the treatment of biogenic carbon storage is critical for quantifying the greenhouse gas emissions of bio-based materials in comparison with petrochemical materials. We acknowledge that biogenic carbon storage remains controversial but recommend accounting for it, depending on product-specific life cycles and the likely time duration of carbon storage. If carbon storage is considered, co-product allocation is nontrivial and should be chosen with care in order to: (i) ensure that carbon storage is assigned to the main product and the co-product(s) in the intended manner and (ii) avoid double counting of stored carbon in the main product and once more in the co-product(s). Land-use change, soil degradation, water use, and impacts on soil carbon stocks and biodiversity are important aspects that have recently received attention. We explain various approaches to account for these and conclude that substantial methodological progress is necessary, which is however hampered by the complex and often case- and site-specific nature of impacts. With the exception of soil degradation, we recommend preliminary approaches for including these impacts in the LCA of bio-based materials. The use of attributional versus consequential LCA approaches is particularly relevant in the context of bio-based materials. We conclude that it is more challenging to prepare accurate consequential LCA studies, especially because these should account for future developments and secondary impacts around bio-based materials which are often difficult to anticipate and quantify. Although hampered by complexity and limited data availability, the application of the proposed approaches to the extent possible would allow obtaining a more comprehensive insight into the environmental impacts of the production, use, and disposal of bio-based materials. 相似文献
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Land use change and carbon exchange in the tropics: I. Detailed estimates for Costa Rica,Panama, Peru,and Bolivia 总被引:1,自引:0,他引:1
Charles A. S. Hall R. P. Detwiler Philip Bogdonoff Sheila Underhill 《Environmental management》1985,9(4):313-333
Our group, composed of modelers working in conjunction with tropical ecologists, 3 has produced a simulation model that quantifies the net carbon exchange between tropical vegetation and the atmosphere due to land use change. The model calculates this net exchange by combining estimates of land use change with several estimates of the carbon stored in tropical vegetation and general assumptions about the fate of cleared vegetation. In this report, we use estimates of land use and carbon storage organized into sixlife zone (sensu Holdridge) categories to calculate the exchange between the atmosphere and the vegetation of four tropical countries. Our analyses of these countries indicate that this life zone approach has several advantages because (a) the carbon content of vegetation varies significantly among life zones, (b) much of the land use change occurs in life zones of only moderate carbon storage, and (c) the fate of cleared vegetation varies among life zones. Our analyses also emphasize the importance of distinguishing between temporary and permanent land use change, as the recovery of vegetation on abandoned areas decreases the net release of carbon due to clearing. We include sensitivity analysis of those factors that we found to be important but are difficult to quantify at present. 相似文献
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Joris Koornneef Tim van Keulen Andr Faaij Wim Turkenburg 《International Journal of Greenhouse Gas Control》2008,2(4):448
In this study the methodology of life cycle assessment has been used to assess the environmental impacts of three pulverized coal fired electricity supply chains with and without carbon capture and storage (CCS) on a cradle to grave basis. The chain with CCS comprises post-combustion CO2 capture with monoethanolamine, compression, transport by pipeline and storage in a geological reservoir. The two reference chains represent sub-critical and state-of-the-art ultra supercritical pulverized coal fired electricity generation. For the three chains we have constructed a detailed greenhouse gas (GHG) balance, and disclosed environmental trade-offs and co-benefits due to CO2 capture, transport and storage. Results show that, due to CCS, the GHG emissions per kWh are reduced substantially to 243 g/kWh. This is a reduction of 78 and 71% compared to the sub-critical and state-of-the-art power plant, respectively. The removal of CO2 is partially offset by increased GHG emissions in up- and downstream processes, to a small extent (0.7 g/kWh) caused by the CCS infrastructure. An environmental co-benefit is expected following from the deeper reduction of hydrogen fluoride and hydrogen chloride emissions. Most notable environmental trade-offs are the increase in human toxicity, ozone layer depletion and fresh water ecotoxicity potential for which the CCS chain is outperformed by both other chains. The state-of-the-art power plant without CCS also shows a better score for the eutrophication, acidification and photochemical oxidation potential despite the deeper reduction of SOx and NOx in the CCS power plant. These reductions are offset by increased emissions in the life cycle due to the energy penalty and a factor five increase in NH3 emissions. 相似文献
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Xiaoyu Yan 《International Journal of Greenhouse Gas Control》2010,4(5):878-887
This paper compares the GHG emissions of coal-to-liquid (CTL) fuels to the GHG emissions of electric vehicles (EVs) powered with coal-to-electricity in China. A life cycle model is used to account for full fuel cycle and use-phase emissions, as well as vehicle cycle and battery manufacturing emissions. It is found that the reduction of life cycle GHG emissions of EVs charged by electricity generated from coal, without utilizing carbon dioxide capture and storage (CCS) technology can be 3–36% when compared to petroleum-based gasoline car. The large range in emissions reduction potential is driven by the many different power generation technologies that are and could in the future be used to generate electricity in China. When CCS is employed in power plants, the GHG emission reductions increase to 60–70% compared to petroleum-based gasoline car. However, the use of coal to produce liquid transportation fuels (CTL fuels) will likely lead to significantly increased life cycle GHG emissions, potentially 30–140% higher than petroleum-based gasoline. When CCS is utilized in the CTL plant, the CTL fueled vehicles emit roughly equal GHG emissions to petroleum-based gasoline vehicles from the life cycle perspective. The authors conclude that policies are therefore needed in China in order to accelerate battery technology and infrastructural improvements for EV charging, increased energy efficiency management, and deployment of low-carbon technologies such as CCS. 相似文献
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ABSTRACT In this paper, an artificial neural network-based control strategy is proposed for low voltage DC microgrid (LVDC microgrid) with a hybrid energy storage system (HESS) to improve power-sharing between battery and supercapacitor (SC) to suit the demand-generation imbalance, maintain state-of-charge (SOC) within boundaries and thereby to regulate the dc bus voltage. The conventional controller cannot track the SCs current rapidly with the high-frequency component that will place dynamic stress on the battery, further resulting in shorter battery life. The significant advantage is that in the proposed control strategy, redirections of unwaged battery currents to SCs for fast compensations enhance battery life span. The proposed control strategy effectiveness was investigated by simulations, including a comparison of overshoot/undershoot and settling time in dc bus voltage with a conventional control strategy. The results have been experimentally verified by hardware-in-loop (HIL) on a field-programmable gate array (FPGA)-based real-time simulator. 相似文献
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Anna Korre Zhenggang Nie Sevket Durucan 《International Journal of Greenhouse Gas Control》2010,4(2):289-300
Due to its compatibility with the current energy infrastructures and the potential to reduce CO2 emissions significantly, CO2 capture and geological storage is recognised as one of the main options in the portfolio of greenhouse gas mitigation technologies being developed worldwide. The CO2 capture technologies offer a number of alternatives, which involve different energy consumption rates and subsequent environmental impacts. While the main objective of this technology is to minimise the atmospheric greenhouse gas emissions, it is also important to ensure that CO2 capture and storage does not aggravate other environmental concerns. This requires a holistic and system-wide environmental assessment rather than focusing on the greenhouse gases only. Life Cycle Assessment meets this criteria as it not only tracks energy and non-energy-related greenhouse gas releases but also tracks various other environmental releases, such as solid wastes, toxic substances and common air pollutants, as well as the consumption of other resources, such as water, minerals and land use. This paper presents the principles of the CO2 capture and storage LCA model developed at Imperial College and uses the pulverised coal post-combustion capture example to demonstrate the methodology in detail. At first, the LCA models developed for the coal combustion system and the chemical absorption CO2 capture system are presented together with examples of relevant model applications. Next, the two models are applied to a plant with post-combustion CO2 capture, in order to compare the life cycle environmental performance of systems with and without CO2 capture. The LCA results for the alternative post-combustion CO2 capture methods (including MEA, K+/PZ, and KS-1) have shown that, compared to plants without capture, the alternative CO2 capture methods can achieve approximately 80% reduction in global warming potential without a significant increase in other life cycle impact categories. The results have also shown that, of all the solvent options modelled, KS-1 performed the best in most impact categories. 相似文献