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通过计算裂纹尖端应力强度因子及疲劳裂纹扩展速率da/d N,由C.Paris模型推导出安全寿命Nf,由Bathias公式计算"哑铃"状钛合金试样的裂纹扩展寿命。通过理论计算和有限元分析超声疲劳"哑铃"状试样,得出应力最大位置。利用有限元仿真和实验数据分析TC4钛合金疲劳寿命。在20 k Hz的超声疲劳试验中,试样的断口位置表明:TC4钛合金材料内部缺陷是试样萌生裂纹使断裂位置偏离最大应力处的主要原因。并得出疲劳裂纹萌生阶段寿命决定"哑铃"状试样的疲劳寿命。 相似文献
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为研究钢丝绳在拉伸载荷下的疲劳寿命预测问题,以6×36 WS结构钢丝绳为研究对象,建立了钢丝绳的有限元模型,仿真分析了其在轴向拉伸载荷下的应力分布。对仿真结果中应力最大的钢丝进行拉伸疲劳试验,得到钢丝试件的载荷寿命曲线。在此基础上进行了钢丝绳疲劳寿命的仿真分析,并通过钢丝绳的疲劳试验进行了验证。钢丝绳疲劳仿真结果表明,在轴向拉伸载荷作用下,最大应力位于相邻两个绳股接触区域,对应的此处区域疲劳寿命最短。钢丝绳疲劳寿命仿真与试验结果具有较好的吻合度,由仿真数据拟合的载荷寿命曲线为钢丝绳疲劳寿命的预测提供了依据。 相似文献
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以铰销式碳纤维增强基复合材料(CFRP)环带为研究对象,基于SWT疲劳寿命预测模型,推导了服从威布尔分布的概率疲劳寿命预测方法.在给定的荷载条件下,建立ANSYS有限元模型,获得最不利破坏点处的应力、应变数值,并将其代入SWT模型计算微动疲劳损伤参量.根据微动疲劳寿命实验结果,采用最大似然估计法,建立在双参数威布尔分布下微动疲劳寿命与损伤参量的函数关系,得出在一定可靠度下的微动疲劳寿命预测值.结果表明:有限元的数值模拟结果与实验结果具有一致性,在四个荷载工况下,SWT模型损伤参量和威布尔分布参数值的三次项插值函数均方误差最小,得出95%可靠度下的疲劳寿命循环次数预测值均小于疲劳实验最小测量值,可作为工程设计值使用,同时说明了此疲劳寿命预测模型的正确性. 相似文献
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为解决实际工况中飞机管道疲劳性能问题,研究飞机管道安装应力环境下的疲劳寿命分析方法,首先,建立飞机管道有限元模型;然后,利用有限元软件ANSYS Workbench对不同轴向装配偏差情况下的管道进行模态分析以及谐响应分析;进而,提取出管道危险点应力幅值,利用材料的S-N曲线进行疲劳寿命预测。最后,设计不同安装应力情况下的管道共振疲劳试验,并对仿真结果进行验证。仿真和试验的对比结果表明:根据仿真和试验得到的管道发生断裂的位置一致,两者管道疲劳寿命循环次数契合,随着轴向装配偏差增大,管道疲劳寿命逐渐下降。 相似文献
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接触压力是电接触测试系统的重要参数。电接触测试系统对接触压力的控制指标主要是加载精准度和保持稳定度。本文讨论了三种不同的接触压力加栽保持方案,并针对精密定位电接触系统和微动电接触系统的特点提供接触压力加载保持方案选择的建议。 相似文献
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Yangzhi Zhu Rohollah Nasiri Elham Davoodi Shiming Zhang Sourav Saha Matthew Linn Lu Jiang Reihaneh Haghniaz Martin C. Hartel Vadim Jucaud Mehmet R. Dokmeci Anna Herland Ehsan Toyserkani Ali Khademhosseini 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(11):2207017
The contact lens (CL) industry has made great strides in improving CL-wearing experiences. However, a large amount of CL wearers continue to experience ocular dryness, known as contact lens-induced dry eye (CLIDE), stemming from the reduction in tear volume, tear film instability, increased tear osmolarity followed by inflammation and resulting in ocular discomfort and visual disturbances. In this article, to address tear film thinning between the CL and the ocular surface, the concept of using a CL with microchannels to deliver the tears from the pre-lens tear film (PrLTF) to the post-lens ocular surface using in vitro eye-blink motion is investigated. This study reports an eye-blink mimicking system with microfluidic poly(2-hydroxyethyl methacrylate) (poly(HEMA)) hydrogel with integrated microchannels to demonstrate eye-blink assisted flow through microchannels. This in vitro experimental study provides a proof-of-concept result that tear transport from PrLTF to post-lens tear film can be enhanced by an artificial eyelid motion in a pressure range of 0.1–5 kPa (similar to human eyelid pressure) through poly(HEMA) microchannels. Simulation is conducted to support the hypothesis. This work demonstrates the feasibility of developing microfluidic CLs with the potential to help prevent or minimize CLIDE and discomfort by the enhanced transport of pre-lens tears to the post-lens ocular surface. 相似文献
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S. V. Savel’kaev 《Measurement Techniques》2005,48(5):515-519
The coaxial device described can be used to connect both a microwave analyzer with standard coaxial measures for calibration of the analyzer and to connect microwave stripline circuits in measurements of their S-parameter. The proposed method of calibrating a device, using one or two rated stripline calibrators, transfers the results of the analyzer calibration by means of standard coaxial measures for measurement of S-parameters of stripline circuits.__________Translated from Izmeritel’naya Tekhnika, No. 5, pp. 65–68, May, 2005. 相似文献
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Nan Jiang Yunuen Montelongo Haider Butt Ali K. Yetisen 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(15)
Contact lens is a ubiquitous technology used for vision correction and cosmetics. Sensing in contact lenses has emerged as a potential platform for minimally invasive point‐of‐care diagnostics. Here, a microlithography method is developed to fabricate microconcavities and microchannels in a hydrogel‐based contact lens via a combination of laser patterning and embedded templating. Optical microlithography parameters influencing the formation of microconcavities including ablation power (4.3 W) and beam speed (50 mm s?1) are optimized to control the microconcavity depth (100 µm) and diameter (1.5 mm). The fiber templating method allows the production of microchannels having a diameter range of 100–150 µm. Leak‐proof microchannel and microconcavity connections in contact lenses are validated through flow testing of artificial tear containing fluorescent microbeads (Ø = 1–2 µm). The microconcavities of contact lenses are functionalized with multiplexed fluorophores (2 µL) to demonstrate optical excitation and emission capability within the visible spectrum. The fabricated microfluidic contact lenses may have applications in ophthalmic monitoring of metabolic disorders at point‐of‐care settings and controlled drug release for therapeutics. 相似文献
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An attempt was made to extract the thermodynamic work of adhesion from contact angle measurements and contact mechanics in
order to compare it with interfacial toughness values of a glass/epoxy interface. The three probe liquid method, in conjunction
with laser goniometry, yielded a value of the work of adhesion of 93 mJ/m2. This was an order of magnitude less than the value extracted from the Maugis solution for contacting spheres with surface
interactions. These work of adhesion values were both lower than the 1.5 J/m2 which was determined in a parallel study of interfacial fracture as a mode-mix independent component of the overall interfacial
toughness. Some of the reasons for these differences are explored.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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目的研究不同形态的食品接触材料及制品接触面积(S)与食品模拟物体积(V)的测量方法。方法食品接触材料及制品的检测一般先要准确地测定出S与V,但实际检测中由于样品结构的多样性以及某些样品S和V的计算公式不为人熟知,常采用估算方法,会造成较大的人为误差。以某些不锈钢制品为例,检索国内外数学手册,找到相关的计算公式并进行推导,同时综合测定非规则几何体S与V的方法。结果得到了圆环胎、螺旋弹簧、球台、椭球体、桶形体、抛物面体等常见规则几何体的表面积、体积计算公式,以及测定非规则几何体S与V的方法。结论由这些公式及方法可准确测定S和V,可避免人为误差,实现科学、准确的检测。 相似文献