Non-linear MSD crack growth by DBEM for a riveted aeronautic reinforcement

A special specimen is created cutting a rectangular notched area from the surrounding of the upper left corner of a wide body aircraft door. Then a constant amplitude fatigue traction load is applied by a special servo-hydraulic machine, in order to induce a Multi Site Damage (MSD) scenario.The Dual Boundary Element method (DBEM), as implemented in a commercial code, is adopted for a three-dimensional MSD crack growth simulation of such multi-layer and multi-material component. To this aim, the cracked part of a pre-existing global two-dimensional model is extracted and “extruded” in order to generate a three-dimensional submodel, whose boundary conditions are imposed displacements, calculated by the two-dimensional model, along a virtual line corresponding to the submodel boundary. Non-linear contact conditions are applied between the mating plate surfaces in the area surrounding the cracks, in order to precisely model the plate interactions in the area of interest.The three-dimensional approach is aimed to improve, with respect to the two-dimensional approach, the correlation between numerical and experimental results (e.g. by an accurate assessment of the secondary bending effects). The obtained improvements on crack growth rates, in the initial part of the crack propagation, justify the increased computational effort that a three-dimensional non-linear approach involves.The proposed numerical procedure, based on DBEM, is successfully validated for the virtual testing of a complex aeronautic reinforcement.     

Implementation of a crack propagation constraint within a structural optimization software

A crack propagation constraint related to the stress intensity factor is examined for the minimum-weight design optimization of a composite blade-stiffened panel. A low-fidelity approach uses a closed-form solution for the stress intensity factor, while a high-fidelity approach uses the stress distribution around the crack. Structural optimizations are performed by low- and high-fidelity approaches for a number of panels configured with different values of the load, crack length, and blade height. Response surface (RS) approximations are then constructed for the optimal weight as a function of the three configuration variables. The computational cost, numerical noise, and accuracy for the two approaches are compared. An additional constraint in the low-fidelity solutions is found to be active for some of the configurations, increasing the difference between the low-fidelity and high-fidelity optima. It is shown that outlier analysis helps to identify the configurations with the largest difference.     

Flat panel detector based on a shadow mask plasma display panel

A flat panel detector based on the structure of a shadow mask plasma display panel is analyzed in terms of the electron amplification factor when used in the Townsend mode. The detector consists of a metal shadow mask and two ultra‐thin glass substrates with electrodes depositing on them. The shadow mask divides the detecting area into arrays of independent cells. The electron gain and linearity of the device are investigated by simulation based on the particle‐in‐cell/Monte Carlo collision model. Similar experiments are carried out. Both experimental and simulation results show that the linearity of the detector is significant. The applied voltages and the effective cathode area are parameters affecting its gain. As the avalanche process in the center of the cell with small electric field strength is much smaller than that near the shadow mask edge, the gain increases exponentially with the anode voltage but decreases with the negative shadow mask voltage. The balance between effective cathode area and high electric field intensity near the shadow mask edge provides room for future optimization of the detector. In conclusion, the flat panel detector is a promising component in a detection system for high energy radiation, and the wide application of the device is expected.     

破片侵彻飞机机翼壁板的应急修理有限元分析

针对飞机机翼壁板遭受导弹破片侵彻后的应急修理问题,以某飞机机翼受损壁板为例,采用全机有限元模型对其铆接修理进行强度计算．计算模型中补片的单元类型采用壳单元,铆钉用梁单元．结果表明,在铆钉钉距、排距和边距一定的情况下,铆钉排数与修理后的承载能力有对应关系．该对应关系为战场上合理制定应急修理方案提供理论参考．     

Display panel design of a general utility helicopter by applying quantitative and qualitative approaches

The flight deck is the ultimate human–machine interface application. It uses human senses of touch and sight in a safety‐critical situation. Display systems, present on a flight deck, are complex environments causing excessive mental workload, and the consequences of errors can be catastrophic. To prevent any human error, a user‐friendly display panel must be designed. In this research the best natural dialog between the crew and interface is considered while reflecting user perspective to design by applying quantitative and qualitative approaches; in this way, proper positions of analogue indicators on the front of the display panel are determined. Multi‐Criteria Decision Making algorithms are employed as a quantitative approach. To test whether the decision‐making preferences are consistent with a quasi‐concave, a quasi‐convex, and a linear utility function, a combined algorithm is applied. Due to the form of utility function, an algorithm finding the most preferred alternative of decision making is used. The aim of this approach is to find an order in which to locate each indicator to suitable classes. Card‐Sorting methodology is used for the qualitative research of the same problem. Results of two different approaches are compared. © 2009 Wiley Periodicals, Inc.     

Location and orientation of panel on the screen as a structural visual element to highlight text displayed

Searching for information on the internet has become a daily activity. It is considered to be a complex cognitive activity that involves visual attention. Many studies have demonstrated that users’ information search are affected both by the spatial configuration of words and the elements displayed on the screen: elements that are used to structure web pages. One of these elements, the web panel, contains information. Web panel is a rectangular area with a colored background that was used to highlighting content presented in this specific rectangular area. Our general hypothesis was that the presence of a panel on a web page would affect the structure of a word display, as a result, information search accuracy. We carried out an experiment in which we manipulated the presence vs. the absence of a panel, as well as its orientation on the screen (vertical vs. horizontal). Twenty participants were asked to answer questions while their eye movements were recorded. Results showed that the presence of a panel resulted in reduced accuracy and shorter response times. Panel orientation affected scanpaths, especially when they were orientated vertically. We discuss these findings and suggest ways in which this research could be developed further in future.     

Contactless inspection of planar electronic devices by capacitive coupling: Development of a model describing the sensor signal and its impact on signal post-processing

With regard to a contactless inspection method for planar electronic devices, a model to derive the signal of the employed sensors has been developed. The measurement technique is exclusively based on capacitive coupling and, for instance, applied to the inspection of flat panel displays (FPDs) and printed electronics. To analyze the sensor signals, to evaluate the sensor performance, and to advance signal post-processing, a model of the capacitive coupling is essential. Focussing on configurations of conductor tracks arranged in parallel, the model approach is explained and illustrated in detail. Finite element (FE) simulations and measurements are used to derive the model parameters, to validate the model approach, and to evaluate the model performance. Possible applications to signal post-processing are discussed. As an example, the model is used to reconstruct the voltages applied to individual tracks of a configuration from the sensor signal. Furthermore, the model is extended to configurations of two-dimensionally arranged conductor tracks.