Characterization and evaluation of brittleness of deep bedded sandstone from the perspective of the whole life-cycle evolution process

The quantitative determination and evaluation of rock brittleness are crucial for the estimation of excavation efficiency and the improvement of hydraulic fracturing efficiency.Therefore,a“three-stage”triaxial loading and unloading stress path is designed and proposed.Subsequently,six brittleness indices are selected.In addition,the evolution characteristics of the six brittleness indices selected are characterized based on the bedding effect and the effect of confining pressure.Then,the entropy weight method(EWM)is introduced to assign weight to the six brittleness indices,and the comprehensive brittleness index Bcis defined and evaluated.Next,the new brittleness classification standard is determined,and the brittleness differences between the two stress paths are quantified.Finally,compared with the previous evaluation methods,the rationality of the proposed comprehensive brittleness index Bcis also verified.These results indicate that the proposed brittleness index Bccan reflect the brittle characteristics of deep bedded sandstone from the perspective of the whole life-cycle evolution process.Accordingly,the method proposed seems to offer reliable evaluations of the brittleness of deep bedded sandstone in deep engineering practices,although further validation is necessary.

Degradation process assessment of prestressed concrete continuous bridges in life-cycle

To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.

Attitude Analysis in Process Conflict for C919 Aircraft Manufacturing

Based on the option prioritization in graph model for conflict resolution of two decision makers(DMs),new logical and matrix representations of four stability concepts for DMs′attitude are proposed.The logical representation of attitude is defined,and converted to the matrix form in order to develop a decision support system(DSS)efficiently.Compared with existing definitions of DMs′attitude based on states,the proposed definitions of attitude based on options are convenient and more effective to generate preferences since that of states can be significantly larger than that of options in a large conflict.In addition,it is easier to obtain the information of the prioritization of option statements than to obtain preference of states for users.The proposed representations are applied to the process conflict during aircraft manufacturing to demonstrate the efficiency of the new approach.

Grey Incidence Analysis Applied to Civil Aircraft Customization Process

The airlines need to select the optional equipment according to their individual development demands and the manufacture′s standard specification manual when purchasing a new airplane.For this customization process,the selection theory is mainly based on qualitative analysis and quantitative analysis.The grey incidence analysis(GIA)is used for modeling,which evaluates the correlations between optional equipment and airlines′individual demands.Meanwhile,the customization demands are quantitatively processed as different weights in evaluation index system with analytical hierarchy process.Then,the value of grey incidence degree is obtained which shows whether the optional equipment is on the purchasing list or not.Finally,two airlines′customization demands are applied in the example of aircraft cabin′s seats,so two different purchasing priorities and equipment installation lists can be obtained.The results and comparisons verify the reasonable of modeling,which provides an objective scheme of aircraft equipment selection.

Hierarchical Colored Timed Petri Nets for Maintenance Process Modeling of Civil Aircraft

Civil aircraft maintenance process simulation model is an effective method for analyzing the maintainability of a civil aircraft. First, we present the Hierarchical Colored Timed Petri Nets for maintenance process modeling of civil aircraft. Then, we expound a general method of civil aircraft maintenance activities, determine the maintenance level for decomposition, and propose the methods of describing logic of relations between the maintenance activities based on Petri Net. Finally, a time Colored Petri multi-level network modeling and simulation procedures and steps are given with the maintenance example of the landing gear burst tire of a certain type of aircraft. The feasibility of the method is proved by the example.

INVESTIGATIONS ON LASER SHOCK-PROCESSING (LSP) TO IMPROVE FATIGUE LIFE OF SMALL HOLE IN AIRCRAFT STRUCTURES

Laser shock-processing (LSP) is of particular advantage for improving fa-tigue behavior of small holes and blind holes. Because there are not good accessibility andpassage, these holes cannot be treated by shot peening or cold extrusion. The fatigue livesof aircraft aluminum alloy 2024-T62 are increased greatly by means of optimization oflaser shocking parameters. With 95 % confidence, the mean fatigue life of LSP specimensis 4. 35~7, 75 times larger than that of the un-shocked ones.

Joint optimization of maintenance inspection and spare provisioning for aircraft deteriorating parts

With the wide application of condition based maintenance(CBM) in aircraft maintenance practice, the joint optimization of maintenance and inventory management, which can take full advantage of CBM and reduce the aircraft operational cost, is receiving increasing attention. In order to optimize the inspection interval, maintenance decision and spare provisioning together for aircraft deteriorating parts, firstly, a joint inventory management strategy is presented, then, a joint optimization of maintenance inspection and spare provisioning for aircraft parts subject to the Wiener degradation process is proposed based on the strategy.Secondly, a combination of the genetic algorithm(GA) and the Monte Carol method is developed to minimize the total cost rate.Finally, a case study is conducted and the proposed joint optimization model is compared with the existing optimization model and the airline real case. The results demonstrate that the proposed model is more beneficial and effective. In addition, the sensitivity analysis of the proposed model shows that the lead time has higher influence on the optimal results than the urgent order cost and the corrective maintenance cost, which is consistent with the actual situation of aircraft maintenance practices and inventory management.

Maturity assessment model for aircraft collaborative design software solution

In order to assure quality and control process in the development of the aircraft collaborative design software, a maturity assessment model is proposed. The requirements designing—house of quality is designed to evaluate the maturity degree of the solution, and the evaluation results can help to manage and control the development process. Furthermore, a fuzzy evaluation method based on the minimum deviation is proposed to deal with the fuzzy information. The quantitative evaluation result of the maturity degree can be calculated by optimizing the semantic discount factor aim for the minimum deviation. Finally, this model is illustrated and analyzed by an example study of the aircraft collaborative design software.

RESEARCH ON LASER DIRECT DEPOSITION PROCESS OF Ti-6Al-4V ALLOY

Laser direct deposition （LDD） of metallic components is an advanced technology of combining CAD/CAM （computer aided design/computer aided manufacturing）, high power laser, and rapid prototyping. This technology uses laser beam to melt the powders fed coaxiaUy into the molten pool by the laser beam to fabricate fuUy dense metallic components. The present article mainly studies the LDD of Ti-6Al-4V alloy, which can be used to fabricate aircraft components. The mechanical properties of the Ti-6Al-4V alloy, fabricated by LDD, are obtained using the tension test, and the oxygen content of used powders and deposited specimens are measured. In the present article, it can be seen that the mechanical properties obtained using this method are higher than the ones obtained by casting, and equal to those got by wrought anneal. One aircraft part has been made using the LDD process. Because of this aircraft part, with sophisticated shape, the effect of the laser scanning track on the internal soundness of the deposited part was discussed.

On the Efficiency of a CFD-Based Full Convolution Neural Network for the Post-Processing of Field Data

The present study aims to improve the efficiency of typical procedures used for post-processing flow field data by applying a neural-network technology.Assuming a problem of aircraft design as the workhorse,a regression calculation model for processing the flow data of a FCN-VGG19 aircraft is elaborated based on VGGNet(Visual Geometry Group Net)and FCN(Fully Convolutional Network)techniques.As shown by the results,the model displays a strong fitting ability,and there is almost no over-fitting in training.Moreover,the model has good accuracy and convergence.For different input data and different grids,the model basically achieves convergence,showing good performances.It is shown that the proposed simulation regression model based on FCN has great potential in typical problems of computational fluid dynamics(CFD)and related data processing.

Conceptual Architecture for Remotely Piloted Operation Mode in Commercial Aircraft

With the increasing civil aviation passengers and the rapid development of aviation logistics,the study on remotely piloted operation(RPO)mode has received extensive attention.RPO mode constructs the piloting decisionmaking mode which involves the tripartite collaboration among airborne automatic/autonomous system,remote ground-based crews and air traffic control.In this paper,we describe the organizing architecture for commercial remotely piloted aircraft(CRPA)system and its components.Compared with the current operation mode,the new air-ground collaborative decision-making mode has been established with six different situations based on the type of the flight and the condition of the remote pilot.Taking airport surface operation as an experimental example,we model the airport surface operation process and compare the advantages and disadvantages between RPO mode and the current dual-pilot mode from the perspectives of time and operation coverage,and draw conclusions that RPO mode can basically cover the flight operations of the dual-pilot,improve the accuracy of pilot operations and greatly reduce response time by 48%in pre-flight inspection.The above research would be the foundation for the RPO development of commercial aircraft in China.

Fuzzy Q learning algorithm for dual-aircraft path planning to cooperatively detect targets by passive radars

The problem of passive detection discussed in this paper involves searching and locating an aerial emitter by dualaircraft using passive radars. In order to improve the detection probability and accuracy, a fuzzy Q learning algorithrn for dual-aircraft flight path planning is proposed. The passive detection task model of the dual-aircraft is set up based on the partition of the target active radar＇s radiation area. The problem is formulated as a Markov decision process （MDP） by using the fuzzy theory to make a generalization of the state space and defining the transition functions, action space and reward function properly. Details of the path planning algorithm are presented. Simulation results indicate that the algorithm can provide adaptive strategies for dual-aircraft to control their flight paths to detect a non-maneuvering or maneu- vering target.

基于机器视觉的飞机故障检查系统

针对当前飞机维修检查工作以人工目视检查为主、效率低且存在人为因素影响的情况,设计一套基于图像识别与机器深度学习的飞机部件表面无损检测系统。收集并整理了某航空公司一线飞机维修员拍摄的飞机机身及发动机部件图片,对图片集进行预处理,包括通道提取、Sobel滤波处理及二值化;最后用Blob分析对处理后的图像进行特征提取与系统分析。系统运行速度快、准确率高且可连续自动识别图像。利用机器视觉技术对飞机部件表面进行无损检测不仅可以提高生产效率,同时可以去除人为因素对航空器飞行安全的影响,使得飞机的飞行安全得到进一步提升。实践证明,该系统性能稳定可靠,具有极高的推广应用价值。

飞机火焰抑制器阻火测试中混合气体的适用性研究

文章对典型民用飞机油箱通气口飞机火焰抑制器火焰传播特性开展试验研究。根据SAEARP5416中规定的H_(2)、O_(2)、Ar3种混合气体的燃爆方案,借鉴ISO16852标准下的试验方法,自建燃爆试验台,并分别在不同H_(2)体积分数、阻火芯体内部孔径和芯体长度的情况下开展系列试验,并与现行商用阻火器特性进行对比,同时使用高速摄像机获得爆燃阻火现象及规律并开展仿真对比。试验结果表明,使用体积分数为5.0%~10.0%的H_(2)进行飞机火焰抑制器火焰传播试验时,试验阻火成功率极低,并得到H_(2)体积分数升高对火焰传播速度的影响规律。研究表明,H_(2)与航空煤油蒸气的特性差异是阻火失效的关键因素。该文对此次试验的混合气体局限性进行分析,试验结果也为H2类阻火器的研究提供一定的参考。

航空发动机弯管内表面磁力研磨技术的研究进展

航空发动机弯管的内表面质量影响发动机的整体性能和安全。磁粒研磨具有无须专用加工设备、精度高、柔性和仿形性好、易于实现自动化等优势,有望成为航空发动机弯管内表面精密加工的主要技术途径。介绍了磁粒研磨的方法和机理,总结了聚磁装置对磁粒研磨的影响,各因素及交互作用因素对表面粗糙度和材料去除的影响。提出了基于开槽磁极的离散法提高磁粒研磨精度和效率和基于遗传算法优化的BP神经网络预测最佳航空发动机弯管磁粒研磨工艺参数的优化思路,并归纳了磁粒研磨效果评价方法。列举了磁粒研磨技术在航空发动机弯管内表面精密加工中的应用,并对航空发动机弯管内表面磁力研磨技术的发展趋势进行了展望。

飞机碳纤维复合材料蒙皮激光除漆技术的研究进展

碳纤维复合材料是飞机蒙皮的重要材料,除漆是飞机碳纤维复合材料蒙皮再次涂装之前最为重要的工序。激光除漆具有高效、可控、分层、“绿色”的优势,有望成为飞机碳纤维复合材料蒙皮除漆的主要技术途径。介绍了激光分层可控除漆方法和机理,总结了激光能量密度、激光扫描速度、激光搭接率等工艺因素对飞机碳纤维复合材料蒙皮涂层去除的影响规律,提出了激光分层可控除漆工艺的优化思路,并归纳了激光除漆效果评价方法。列举了激光除漆技术在飞机复合材料表面涂层维修中的应用,并对飞机碳纤维复合材料蒙皮激光除漆技术的发展趋势进行了展望。

飞机线束装配螺栓螺距数量图像测量方法研究

飞机线束是电气线路互联系统(EWIS)的装配单元,重要的飞机线束常以线束捆的方式用P型金属带垫卡箍固定在飞机上。卡箍固定线束的装配质量检测要求之一是卡箍螺栓与螺母拧紧后,螺栓应露出螺母螺距数量大于规定值。为实现飞机线束装配检测智能化,提出一种基于图像自动识别P型卡箍螺栓伸出螺母螺距数量的方法。分析确立螺栓伸出螺母单侧牙顶中点为需要识别的图像特征点,并建立利用牙顶特征点计算螺距数量的公式;通过对图像进行预处理、边缘检测、轮廓提取及拟合、极值点检测等得到牙顶特征点个数;针对不同具体图像实例进行了实验验证。

考虑不确定工期的飞机定检工序鲁棒优化模型

航空定检维修是确保飞机适航安全性重要工作,也是决定航空维修效率和成本关键环节。针对飞机定检维修工期受多种外部因素影响问题,建立考虑不确定工期的飞机定检调度模型。该模型以最大化工序鲁棒值为目标函数,同时考虑优先级约束和可更新资源约束。采用改进的萤火虫算法进行求解,将该算法应用到规模分别为10、20和30的标准实际案例验证。结果表明,相比于随机搜索算法,改进萤火虫算法得到的工序鲁棒值分别提高20.87%、93.41%和219.40%。最后对某维修中心PA44飞机的500 h定检维修案例进行分析。结果表明与实际情况相比,项目的鲁棒值提高了0.1182,证明了该模型在飞机定检工序鲁棒优化上有较好适用性。

小模数航空锥齿轮全工序法铣齿印痕模拟研究

针对小模数航空螺旋锥齿轮全工序铣齿技术应用展开研究,采用KIMOS软件对齿轮印痕进行仿真,调整齿轮印痕,生成调整卡,采用国产机床加工,并参照测量结果进行大轮反调。加工后,通过验证实现小模数航空齿轮的全工序铣齿,取代五刀法,保证齿轮加工精度的同时提高加工效率。

航空导向器三维测点处理与喉道面积精确计算

导向器是航空发动机的重要部件,喉道面积作为其关键参数直接影响发动机动力性能。针对导向器喉道面积现有测量方法效率低、喉道面积估计不准的问题,提出了导向器三维测点处理与喉道面积精确计算的新方法,并在多联叶片导向器样件上开展了该方法与三坐标测量计算方法的对比实验。实验结果表明,所提方法得到的喉道面积更精确,且多次测量计算结果具有较高的一致性。