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Repaired composite laminate with rectangular cut-out is studied by tensile experiments and FEM simulation in this paper. A user damage subroutine is implemented to ABAQUS to simulate the damage of laminate. Good agreements between experimental data and numerical results are reached. From the experiment and FEM simulation results, the integrality of composite structure is destroyed due to the existence of cut-out. However, the asymmetry of repair gets this effect farther. From damage simulation, the initiation and development of three types of damages are predicted. The matrix cracking occurs at first, fiber–matrix shear and fiber break are subsequent. The effect of matrix cracking to the carrying capacity of structure is very small, but when fiber–matrix shear and fiber break occur, dangerous to structure, the carrying capacity of structure loses rapidly. 相似文献
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This work concerns notched composite plates repaired with external circular patches. Their load carrying capability and failure process under tensile loading were investigated experimentally. In the case of a strong adhesive joint, the stiffness of the patches has to be optimized to release high stress concentration and obtain the best repair performance. It was found that the damage progression of the repairs depends not only on the patch stiffness but also on the stacking sequence. With visual inspection and acoustic emission, three modes of damage and failure process for patch repaired specimens were identified. Theses damage models are essential for the development of a numerical design tool for the optimization of external patch repairs. 相似文献
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Sarah Klingler Benedikt Bagemihl Dr. Alexander K. Mengele Dr. Simon Kaufhold Dr. Pasi Myllyperkiö Dr. Jussi Ahokas Prof. Dr. Mika Pettersson Prof. Dr. Sven Rau Prof. Dr. Boris Mizaikoff 《Angewandte Chemie (International ed. in English)》2023,62(44):e202306287
Currently, most photosensitizers and catalysts used in the field of artificial photosynthesis are still based on rare earth metals and should thus be utilized as efficiently and economically as possible. While repair of an inactivated catalyst is a potential mitigation strategy, this remains a challenge. State-of-the-art methods are crucial for characterizing reaction products during photocatalysis and repair, and are currently based on invasive analysis techniques limiting real-time access to the involved mechanisms. Herein, we use an innovative in situ technique for detecting both initially evolved hydrogen and after active repair via advanced non-invasive rotational Raman spectroscopy. This facilitates unprecedently accurate monitoring of gaseous reaction products and insight into the mechanism of active repair during light-driven catalysis enabling the identification of relevant mechanistic details along with innovative repair strategies. 相似文献
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In this paper, the optimal replacement problem is investigated for a system with two types of failures. One type of failure is repairable, which is conducted by a repairman when it occurs, and the other is unrepairable, which leads to a replacement of the system at once. The repair of the system is not “as good as new”. The consecutive operating times of the system after repair form a decreasing geometric process, while the repair times after failure are assumed to be independent and identically distributed. Replacement policy N is adopted, where N is the number of repairable failures. The system will be replaced at the Nth repairable failure or at the unrepairable failure, whichever occurs first. Two replacement models are considered, one is based on the limiting availability and the other based on the long-run average cost rate of the system. We give the explicit expressions for the limiting availability and the long-run average cost rate of the system under policy N, respectively. By maximizing the limiting availability A(N) and minimizing the long-run average cost rate C(N), we theoretically obtain the optimal replacement policies N∗ in both cases. Finally, some numerical simulations are presented to verify the theoretical results. 相似文献
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Shey-Huei Sheu Chin-Chih Chang Yu-Hung Chien 《European Journal of Operational Research》2012,216(2):503-508
A system is subject to shocks that arrive according to a non-homogeneous pure birth process. As shocks occur, the system has two types of failures. Type-I failure (minor failure) is removed by a general repair, whereas type-II failure (catastrophic failure) is removed by an unplanned replacement. The occurrence of the failure type is based on some random mechanism which depends on the number of shocks occurred since the last replacement. Under an age replacement policy, a planned (or scheduled) replacement happens whenever an operating system reaches age T. The aim of this note is to derive the expected cost functions and characterize the structure of the optimal replacement policy for such a general setting. We show that many previous models are special cases of our general model. A numerical example is presented to show the application of the algorithm and several useful insights. 相似文献
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通过聚二甲基硅氧烷(PDMS)与碳纤维织物复合, 采用模板法在PDMS聚合物表面构筑微阵列结构, 制备了一种具有可重复粘贴性的超疏水薄膜. 研究结果表明, 该薄膜微结构表面的接触角为154°, 滚动角为14°, 具有低黏附的超疏水特性. 而PDMS与碳纤维织物的紧密结合, 赋予了超疏水薄膜较高的黏接力和力学性能, 断裂强度达到116.96 MPa. 所制备的超疏水薄膜可粘贴于多种材料表面, 同时经过30 d的长时间粘贴以及50次的循环粘贴后, 该薄膜依然保持着较高的黏附性能及超疏水特征, 表明超疏水薄膜具有良好的力学稳定性及耐久性, 满足长时间可重复使用的要求, 可应用于对破损超疏水涂层的快速、 大面积粘贴修复. 相似文献
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Igor N. Kovalenko 《Mathematical Methods of Operations Research》1997,45(3):387-409
A repairable system is composed of components ofI types. A component can be loaded, put on standby, queued or repaired. The repair facility is here assumed to be a queueing system of a rather general structure though interruption of repairs is not allowed. Typei components possess a lifetime distributionA
i
(t) and repair time distributionB
t
(t). The lifetime of componentj is exhausted with a state-dependent rate
j
(t). A Markov process Z(t) with supplementary variables is built to investigate the system behaviour. An ergodic result, Theorem 1, is established under a set of conditions convenient for light traffic analysis. In Theorems 2 to 6, a light traffic limit is derived for the joint steady state distribution of supplementary variables. Applying these results, Theorems 7 to 10 derive light traffic properties of a busy period-measured random variable. Essentially, the concepts of light traffic equivalence due to Daley and Rolski (1992) and Asmussen (1992) are used. The asymptotic (light traffic) insensitivity of busy period and steady state parameters to the form ofA
i(t) [given their means and (in some cases) values of density functions for smallt], is observed under some analytic conditions.Some abbreviations & notations LHS, RHS
lefthand side, righthand side
- w.r.t.
with respect to
- (i.i.d.) r.v.
(independent identically distributed) random variables
-
A
c
complement event
- d.f., p.d.f.
distribution function, probability density function
- m.g.f.
moment generating function
-
I
A
indicator function of eventA
-
(t)
=1–A(t) 相似文献
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Random fixed points for nonexpansive and pseudocontractive random multivalued operators defined on unbounded subsets of a Banach space are obtained 相似文献