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排序方式: 共有2591条查询结果,搜索用时 15 毫秒
71.
分析德士古气化炉中的激冷室的工艺状况,再结合某厂德士古气化炉的实际生产情况分析下降管的损坏原因及其避免手段。 相似文献
72.
Sensitivity and analysis GPS signals based bridge damage using GPS observations and wavelet transform 总被引:1,自引:0,他引:1
This paper uses GPS monitoring system on the Yonghe Bridge. After a year from re-construction of this bridge, cracks were pronounced 48.2 m far from the beginning of the abutment. To analyze the movements of bridge tower, the current operational safety, the cause of bridge cracks and sensitivity of GPS signals, and its movements were observed under different stress factors such as wind speed, temperature change and traffic loads. The observed lateral, longitudinal of bridge’s towers were studied. Two analytical methods namely; DWT and FT were used for the analysis of observation data. The analysis of test results indicates that: (1) The STFT is a significant step forward from the traditional FFT in terms of structural response analysis. (2) The sensitivity of GPS signals does not depend on the position of GPS antenna; and (3) the cracks of bridge deck bring out the frequency of the bridge tower movement transient characteristics. 相似文献
73.
Michele Dilena Marta Fedele Dell’Oste Antonino Morassi 《Mechanical Systems and Signal Processing》2011,25(8):3186-3197
This paper deals with the identification of a single open crack in a straight pipe containing fluid under pressure by frequency measurements. The crack is assumed to be a transverse partial cut of the pipe wall thickness with straight front and it is simulated by an equivalent elastic spring. It is shown that the measurement of the damage-induced shifts in a pair of natural frequencies of the bending vibration can be used to formulate and solve the diagnostic problem. In particular, it is shown that the change in the first two frequencies in a simply supported uniform pipe is sufficient to localize a small crack, except for a symmetrical position, and to determine the damage severity. Closed-form expressions are provided for damage location and severity. An extension of the method to simply supported uniform pipe with two cracks of equal severity is also presented. The analysis is based on an explicit expression of the frequency sensitivity to damage and allows to consider pipes under general set of boundary conditions. Analytical results agree well with the numerical tests. 相似文献
74.
Andrzej Katunin 《Mechanical Systems and Signal Processing》2011,25(8):3153-3167
In this paper the construction of general order two-dimensional B-spline wavelets was presented and applied for damage identification in polymeric composite plates. At the very beginning the algorithm of one- and two-dimensional discrete wavelet transform and formulation of one- and two-dimensional B-spline wavelets with examples were presented. The fully clamped square layered composite plate was modeled using finite element-based software. Estimated natural modes of vibration with various damage configurations were analyzed using the two-dimensional sixth-order B-spline wavelet, and the method of damage identification was presented. The effective damage identification is based on the evaluation of the singularities in horizontal, vertical and diagonal details coefficients. Results obtained based on the numerical data were verified experimentally. Research results show the effectiveness of B-spline wavelets in application to the diagnostics and structural health monitoring. 相似文献
75.
A finite-element model of the interaction of an elastic-plastic asperity junction based on cylindrical or spherical asperities is used to predict sliding friction coefficients. The modelling differs from previous work by permitting greater asperity overlaps, enforcing an interface adhesional shear strength, and allowing material failure. The results of the modelling were also used to predict friction coefficients for a stochastic rough surface. The asperities were based on the titanium alloy Ti-6Al-4V, and the magnitudes of the predicted friction coefficients were generally representative of experimental measurements of sliding friction. The results suggest that friction arises from both plasticity and tangential interface adhesion. 相似文献
76.
Maciej RadzieńskiMarek Krawczuk Magdalena Palacz 《Mechanical Systems and Signal Processing》2011,25(6):2169-2190
The objective of this paper is to introduce a new method for structural damage detection based on experimentally obtained modal parameters. The new method is suitable for detection of fatigue damage occurring in an aluminium cantilever beam. The damage has been practically realised as saw cuts of different sizes and at different locations. The first step of analysis included an attempt of damage identification with the most often used damage indicators based on measured modal parameters. For that purpose special signal processing technique has been proposed improving the effectiveness of indicators tested. However the results obtained have not been satisfactory. That was the motivation for defining new damage indicators (frequency change based damage indicator, Hybrid Damage Detection method), utilising the change of natural frequencies and any mode shape (measured or modelled) as the measurement of frequencies is much less time consuming in comparison to total mode shape measurement. It has been shown that the proposed technique is suitable for damage localisation in beam-like structures. 相似文献
77.
引入描述双变量损伤条件下的本构关系,进而以热力学原理为基础,引入损伤驱动力,建立损伤演化准则。构建一般情况下的时间型损伤演化方程和循环型损伤演化方程。利用分离变量方法再对损伤演化方程积分,得到光滑试件在恒幅应变交变载荷作用下寿命预估方法。根据损伤力学守恒积分原理,得到有缺口试件在恒幅应变交变载荷作用下寿命预估方法。利用上述寿命预估方法,由KT=1与KT=3的标准试件中值疲劳试验数据确定损伤演化方程中的材质参数。在此基础上给出不同KT下的理论中值疲劳曲线,为采用损伤力学方法来描述构件的疲劳寿命提供一种可行的方法。 相似文献
78.
多年来,"城市道路破路、占道施工管理" 问题一直困扰着城市建设管理部门.如何有效解决"城市道路破路、占道施工管理"问题,就必须认真分析成因,并从中找到加强管理和根治的办法. 相似文献
79.
R. Luri C.J. Luis PérezD. Salcedo I. PuertasJ. León I. PérezJ.P. Fuertes 《Journal of Materials Processing Technology》2011,211(1):48-56
In this study, the influence of the die geometry on the introduced damage of the processed parts by ECAE is studied. It will be shown experimentally and by FEM simulations that the die geometry greatly influences the imparted damage, if the die geometry is not selected adequately. This could lead to obtain processed materials which could be useless for posterior mechanical applications because of cracks nucleated inside of them, which will decrease the mechanical properties such as fatigue resistance and formability among others.Several FEM models have been solved in order to obtain a mathematical model to predict the influence of the die geometry.Moreover, several parts have been processed using different die geometries in order to determine the damage within the processed material experimentally and also to validate FEM simulations. A 5083 aluminium alloy in (O) state, which means that has been fully annealed, has been selected and different die geometries have been manufactured for processing this aluminium alloy. 相似文献
80.
The compressive mechanical properties of three dimensional (3D) braided composites are of key concern for design in actual engineering application. A representative volume cell (RVC) is chosen to study the uniaxial compressive mechanical properties of the braided composites with different braid angles by combing damage theory and finite element method. The fiber misalignment and longitudinal shear nonlinearity of braid yarn are considered in the computation model. And their influences on the compressive behavior of the braided composites are also evaluated. The damage development of constituents within the braided composites are obtained and analyzed. The main damage and failure modes and their interaction of braid yarn are provided as well. The numerical results are found that the compressive mechanical behavior of the braided composites with lower braid angle is sensitive to the fiber initial imperfection of braid yarn. The strength of the braided composites with different braid angle is controlled by the different microscopic failure modes. 相似文献