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排序方式: 共有178条查询结果,搜索用时 15 毫秒
1.
Carlos Raimundo Andrade Lima Jefferson da Silva Martins Caroline Pinheiro Luis Fernando de Avila Roberto Rosas Pinho Maria Luiza Miranda Rocco Wilson de Souza Melo Fabio Zappa 《Journal of Polymer Science.Polymer Physics》2019,57(15):967-972
Photopolymerization is a phenomenon that is the basis of much of today's microfabrication technology and intense research is conducted to improve its control and the characteristics of end products for a variety of applications. The design of microscopic structures often relies on the accurate knowledge and modeling of photopolymer's behavior upon exposure, i.e. the Dill parameters, for each radiation species of interest and therefore the development of flexible characterization techniques is of great importance. SU‐8 is a popular compound that is representative of a whole class that relies on cationic polymerization, where an acid is obtained via photolysis of an onium salt during exposure. Here we report on the observation of SbF6? via laser desorption mass spectrometry on SU‐8 exposed to UV light at the wavelength of 365 nm and demonstrate that the yield of this counter‐anion as a function of exposure is consistent with the Dill C parameter value available in the literature. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 967–972 相似文献
2.
Residual stress field and reduction of stress intensity factors in cold-worked holes 总被引:1,自引:0,他引:1
S.T. Pinho H.B. Martins P.P. Camanho M.H. Santare P.M.S.T. de Castro 《Theoretical and Applied Fracture Mechanics》2005,44(2):168-177
Closed-form and semi-analytical solutions are obtained for the residual stress distributions in a plate caused by pressure acting on a central circular hole, representing the cold-work process. The material is elastic–perfectly plastic. Both Tresca and von Mises yield criteria are used and the corresponding residual stress distributions are compared. The relation between the dimension of the plastic zone and the value of internal pressure is presented. The relation between the magnitude of the residual stresses and the remote uniform tensile stress required to open symmetrical radial cracks is also presented. The reduction of the stress intensity factors of cracked open and riveted holes as a function of the internal pressure applied (or mandrel radial displacement) is investigated using numerical models for both an elastic–perfectly plastic material and for an Al 2024-T3 Alclad aluminum alloy. 相似文献
3.
Near-wall data for the strongly perturbed flow in a neutrally stable boundary layer encountering a steep, smooth, two-dimensional
hill are presented. Observations were made on the centerplane of a water channel at thirteen stations relative to the hill
by laser Doppler anemometry. The large reverse flow region that is formed on the lee of the hill was particularly scrutinized
through seven measuring stations. Results are presented for the mean and turbulent properties of the flow. Wall shear stress
was evaluated through fitting procedures that resorted to the near wall behavior of the velocity profile. Logarithmic fits
as well as predictions through the Reynolds stress profiles are also presented. 相似文献
4.
5.
A comprehensive review of techniques for the experimental characterisation of the fracture toughness associated with the translaminar (fibre-breaking) failure modes of continuously reinforced laminated composites is presented. The collection of work relating to tensile failure reveals a varied approach in terms of specimen configuration, size and data reduction, despite the existence of an ASTM standard. Best practices are identified and suggestions for extending the scope of the current standard are made. Works on compressive failure are found to be less comprehensive. Measurement of the toughness associated with initiation of the failure mode in isolation has been achieved, but this review finds that significant research steps need to be taken before a resistance curve can be fully characterised. 相似文献
6.
Flaviane A. de Sousa Anna Isabel G. Costa Maria Eliana L. R. de Queiroz Reinaldo F. Teófilo Gevany P. de Pinho Antônio A. Neves 《Chromatographia》2013,76(1-2):67-73
The pH effect of potato, apple, and soil matrices on the chromatographic response of nine pesticides was evaluated. All chromatographic analyses were performed in duplicate on a gas chromatograph with electron capture detection. The matrix effect observed in the chromatographic response of the pesticides was evaluated by comparison. We compared the chromatographic response of each pesticide in pure solvent and in organic extract obtained for the matrices. The organic extracts were obtained by solid–liquid extraction with partition at low temperature. Depending on the matrix pH, a greater or lesser amount of co-extractives can be extracted into the organic phase, which affects the matrix effect. The pH of the samples before the extraction process was modified in order to check their influence on pesticide responses. Statistical analyses involving principal component analysis and marginal means revealed that, in the potato and apple matrices, the co-extractives exerted positive effects on the chromatographic response of the analytes. At lower pH, the extraction of co-extractives from potato and apple was favored, thus increasing the matrix effect for these samples. 相似文献
7.
8.
A.R. Melro P.P. Camanho F.M. Andrade Pires S.T. Pinho 《International Journal of Solids and Structures》2013,50(11-12):1906-1915
This paper presents the application of a new constitutive damage model for an epoxy matrix on micromechanical analyses of polymer composite materials. Different representative volume elements (RVEs) are developed with a random distribution of fibres. Upon application of periodic boundary conditions (PBCs) on the RVEs, different loading scenarios are applied and the mechanical response of the composite studied. Focus is given to the influence of the interface between fibre and matrix, as well as to the influence of the epoxy matrix, on the strength properties of the composite, damage initiation and propagation under different loading conditions. 相似文献
9.