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91.
92.
A series of naphthopyrans with hydrazone unit ( 8a – 8m ), were synthesized and characterized by 1H NMR, 13C NMR, IR and HRMS. The photochromic properties were investigated under continuous irradiation, in particular regard to the fatigue resistance and the lifetime of the colored open form in solution and polymers. The results showed that these compounds had both good photochromic properties and high fatigue resistance. Detailed studies showed that representative compound 8d (3,3‐di‐4‐methoxybenzoic acid methylenehydrazino‐[3H]‐naphtho [2,1‐b]pyran) had good photochromic properties in THF solution, in solid state, and in polymers, and exhibited a significant bathochromic shift in the spectra of the open forms compared to known naphthopyrans 9 (3,3‐diphenyl‐[3H]‐naphtho[2,1‐b]pyran). On the other hand, the higher melting points of target compounds are promising for the polymer film preparation through hot‐melt method. 相似文献
93.
DIGITAL IMAGE CORRELATION STUDIES FOR FATIGUE MICRO-CRACK INITIATION AND PROPAGATION OF NI BASED SUPERALLOY 总被引:2,自引:0,他引:2
An experimental investigation on the mechanical mechanisms of fatigue micro-crack initiation and propagation of a nickel-based superalloy is presented. By coupling digital image correlation method and scanning electron microscope, the fatigue residual strain distribution at the grain scale has been obtained. The results showed that there is a trend of accumulation for the residual strain. Micro-cracks are more likely to initiate in or near the areas with particularly large residual strain, and propagate along the large-strain paths. 相似文献
94.
深水钢悬链线立管触地区疲劳实验系统设计 总被引:2,自引:0,他引:2
深水钢悬链线立管(steel catenary riser, SCR)触地区易发生疲劳破坏, 且疲劳寿命预测问题是
目前理论计算与数值分析的难点, 通过实验能更好地促进理论和数值研究. 因此在相关理论
研究基础上, 设计一套SCR触地区疲劳实验系统, 模拟实际工作状况, 考虑张力、弯曲、内
外压与管土相互作用等因素的变化组合. 该实验系统为以后开展深水立管疲劳实验、研究SCR
触地区疲劳破坏机理以及准确预测SCR触地区的疲劳寿命奠定基础. 相似文献
95.
96.
Luis Alberto Rodríguez‐Picn Anna Patricia Rodríguez‐Picn Alejandro Alvarado‐Iniesta 《商业与工业应用随机模型》2019,35(3):504-521
Most modern products that are highly reliable are complex in their inner and outer structures. This situation indicates quality characterization by the interaction of multiple performance characteristics, which motivates the utilization of robust reliability models to obtain robust estimates. It is paramount to obtaining substantial information about a product's life cycle; therefore, when multiple performance characteristics are dependent, it is important to find models that address the joint distribution of performance degradation of such. In this paper, a reliability model for products with 2 fatigue‐crack growth characteristics related to 2 degradation processes is developed. The proposed model considers the dependence among degradation processes by using copula functions considering the marginal degradation processes as inverse Gaussian processes. The statistical inference is performed by using a Bayesian approach to estimate the parameters of the joint bivariate model. A time‐scale transformation is considered to assure monotone paths of the degradation trajectories. The comparison results of the reliability analysis, under both dependent and independent assumptions, are reported with the implementation of the proposed modeling in a case study, which consists of the crack propagation data of 2 terminals of an electronic device. 相似文献
97.
To develop design rules for dynamically loaded composite structures, extensive static and cyclic tension/compression-torsion
tests were carried out on carbon-fibre-reinforced composites, in which especially the important influence of multiaxial loading
conditions on their fatigue behaviour was investigated. Physically based failure criteria for static loadings are modified
for multiaxial cyclic loadings, and a good agreement with experiments is achieved.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 5, pp. 631–641, September–October, 2006. 相似文献
98.
Fatigue crack propagation tests on annealed and quenched medium-density polyethylene showed the annealed specimens to have much lower resistance to crack initiation and subsequent propagation. Although the same fracture mechanism, in which the brittle crack gradually becomes more ductile, prevailed in both cases, the voided and fibrillated crack tip root craze in the annealed material was much weaker that the nonfibrillated quenched root craze. Microstructural analyses indicate that the annealed material had separate crystallite populations, whereas the quenched material had a more homogeneous morphology. The highest melting fraction of the annealed material was composed of lamellae that were about 270 Å thick, and the quenched lamellae were estimated to be 160 Å thick. The reduced fatigue crack propagation resistance of the annealed material was suggested to be a result of a lower concentration of tie molecules and its reduced damping capability, compared to the quenched material. © 1995 John Wiley & Sons, Inc. 相似文献
99.
This paper describes a methodology for adapting the acoustoultrasonic technique for use in monitoring structures or mechanical
components. As a practical example, the adaptation of the technique for monitoring fatigue tests on front suspension arms
is considered. From this particular example, it will be shown that the procedure is suitable for application to more general
cases. The results of a number of fatigue tests carried out at the Fiat Research Center on a typical component test rig are
also presented. 相似文献
100.
给出了数据处理的方法,通过对试验数据的分析,给出了裂纹扩展速率与ΔK的关系,为油田的安全生产提供了依据。 相似文献