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51.
热处理对金属基短纤维复合材料蠕变性能影响的试验和理论研究 总被引:2,自引:0,他引:2
采用试验和有限元方法研究了热处理制度对金属基短纤维复合材料(MMC)蠕变性能的影响,同时考虑了2种不同热处理制度和1种铸造状态。试验结果表明,MMC的蠕变响应与热处理制度有关。在相同蠕变应力时,铸态试样有最小的最小蠕变应变率和最长的蠕变寿命,而热处理制度2(试样在550℃保温24h后随炉冷却)具有明显的最大的最小蠕变应变率和最短蠕变寿命,热处理制度1(试样在550℃保温24h后水冷)具有中等的最小蠕变应变率和中等的蠕变寿命。用单胞模型结合有限元方法模拟分析了热处理的影响,结果表明,热处理制度的影响可以归于热处理引起的残余应力和残余应变以及它们的历史,具体可以归于基体的蠕变耗散能、纤维轴向力和纤维—基体界面力。同时考虑了单胞模型的参数对上述分析结果的影响。 相似文献
52.
双剪切试样在镍基单晶合金蠕变变形损伤和寿命研究中的应用 总被引:3,自引:0,他引:3
在对不同滑移系的双剪切试样进行蠕变实验的基础上,结合单向应力拉伸蠕变实验,并利用晶体滑各向异性蠕变损伤本构模型和有限元程序,对双剪切蠕变试样进行了研究。结果表明,对剪切试样受剪区域的应力状态基本为均匀分布且随蠕变时间变化很小,大部分受剪区域为单滑移系开动,提出的基于蠕变γ′相筏化规律的蠕变损伤本构模型,结合有限元(FEM)分析可以很好地描述双剪切试样的蠕变损伤规律,并可以和单向应力状态的实验结果联系起来,双剪切试样可以用来研究镍基单晶合金蠕变性能的晶体取向相关性,实验表明这种晶体取向相关性与开动滑移系类型及γ′相符代规律相关。 相似文献
53.
镍基单晶超合金中孔洞长大的试验和有限元分析 总被引:1,自引:0,他引:1
在高温状态下,镍基单晶超合金的变形、损伤及断裂分析中,孔洞的长大都起着主要的作用。本研究进行了系列的蠕变、疲劳及热机械疲劳(TMF)试验。对试件的断面进行的SEM观察表明,所有的断面都是有许多小断面构成,在断面的中心,至少有一个孔洞。孔洞的尺寸与加载的条件相关。使用晶体塑性有限元程序对单胞模型进行分析,模拟孔洞的长大规律。给出了蠕变和弹塑性两种条件下的模拟结果及不同的晶体取向对孔穴长大的影响结果。对孔洞长大的有限元分析有助于对实验结果的理解。 相似文献
54.
基于动强度可靠性的输流管道动力优化设计 总被引:1,自引:0,他引:1
建立以支撑(位置、刚度)和截面几何特性为设计变量,以结构重量极小化为目标,以动强度可靠性指标和固有频率为约束的管道动力优化模型.针对某类管道,对支撑位置、刚度和管径进行优化分析,得到了支撑、截面参数和管道动力特性之间的关系.计算结果表明此优化方式是合理有效的.经过优化,提高了首超可靠度,减轻了结构重量,降低了动应力,增强了管道的抗振能力. 相似文献
55.
56.
Bending creep test (based on overhang beam geometry) is investigated by incorporating the important contribution of residual stress. Finite element simulations considering the residual stress is employed to investigate the residual stress behavior of bending creep specimen. We propose several methods to determine the creep parameters directly from the bending creep tests. We considered two cases of residual stress, one is tensile residual stress. The other is compressive residual stress. The present work may shed some light on the influences during bending creep, as well as provide an efficient way to determine material residual stress characteristics. 相似文献
57.
58.
Qi Chang Changcong Zhou Haodong Zhao Wenxuan Wang Zhufeng Yue 《Quality and Reliability Engineering International》2023,39(1):382-411
This paper studies the effect of the dependence state between basic events (BEs) on fault tree analysis (FTA) when the probabilities of events are characterized by interval values. The well-known Frèchent bounds are extended for modeling six different types of dependence states between BEs. Three indices, called average dependence effect (ADE), location effect (LE) and size effect (SE), are defined for evaluating the effect of the dependence states between BEs on the probability of top event (TE) and identifying influential and non-influential dependence states. Then, the proposed method is applied to fault tree (FT) examples, thereby explaining the dependence problem in FTA. To further verify the practicability of the method, FTA of the unilateral asymmetric movement failure of an aircraft flap mechanism is performed. The results show that: (i) the opposite and negative dependence contribute to the reliability of a parallel system while the perfect and positive dependence reduce it, (ii) the perfect and positive dependence contribute to the reliability of a series system while the opposite and negative dependence reduce it, and (iii) parallel systems are more reliable than series systems regardless of the dependence between BEs. 相似文献
59.
Shuaihua Zhang Jiayu Wang Nagy L. Torad Wei Xia Muhammad Aamir Aslam Yusuf Valentino Kaneti Zhufeng Hou Zejun Ding Bo Da Amanullah Fatehmulla Abdullah M. Aldhafiri Wazirzada Aslam Farooq Jing Tang Yoshio Bando Yusuke Yamauchi 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(12)
2D transition metal dichalcogenides (TMDs) have received widespread interest by virtue of their excellent electrical, optical, and electrochemical characteristics. Recent studies on TMDs have revealed their versatile utilization as electrocatalysts, supercapacitors, battery materials, and sensors, etc. In this study, MoS2 nanosheets are successfully assembled on the porous VS2 (P‐VS2) scaffold to form a MoS2/VS2 heterostructure. Their gas‐sensing features, such as sensitivity and selectivity, are investigated by using a quartz crystal microbalance (QCM) technique. The QCM results and density functional theory (DFT) calculations reveal the impressive affinity of the MoS2/VS2 heterostructure sensor toward ammonia with a higher adsorption uptake than the pristine MoS2 or P‐VS2 sensor. Furthermore, the adsorption kinetics of the MoS2/VS2 heterostructure sensor toward ammonia follow the pseudo‐first‐order kinetics model. The excellent sensing features of the MoS2/VS2 heterostructure render it attractive for high‐performance ammonia sensors in diverse applications. 相似文献
60.
Zongpeng Ma Shiyao Wang Qixin Deng Zhufeng Hou Xing Zhou Xiaobo Li Fangfang Cui Huayan Si Tianyou Zhai Hua Xu 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(16)
Research on transition metal dichalcogenides (TMDs) has been accelerated by the development of large‐scale synthesis based on chemical vapor deposition (CVD) growth. However, in most cases, CVD‐grown TMDs are composed of randomly oriented grains, and thus contain many distorted grain boundaries (GBs), which seriously degrade their electrical and photoelectrical properties. Here, the epitaxial growth of highly aligned MoS2 grains is reported on a twofold symmetry a‐plane sapphire substrate. The obtained MoS2 grains have an unusual rectangle shape with perfect orientation alignment along the [1‐100] crystallographic direction of a‐plane sapphire. It is found that the growth temperature plays a key role in its orientation alignment and morphology evolution, and high temperature is beneficial to the initial MoS2 seeds rotate to the favorable orientation configurations. In addition, the photoluminescence quenching of the well‐aligned MoS2 grains indicates a strong MoS2?substrate interaction which induces the anisotropic growth of MoS2, and thus brings the formation of rectangle shape grains. Moreover, the well‐aligned MoS2 grains splice together without GB formation, and thus that has negligible effect on its electrical transport properties. The progress achieved in this work could promote the controlled synthesis of large‐area TMDs single crystal film and the scalable fabrication of high‐performance electronic devices. 相似文献