Abstract: With the improvement of performance requirements for modern aircraft, such as speed and leak tightness, the posture alignment of large components without clearance is now extremely required in the aircraft industry. Nevertheless, the inherent errors of both the components themselves and the posture alignment system lead to high risk of collision during the inserting stage, among which the positional errors of spherical joints that connecting the large component to the numerical controlled locators are identified as the primary error source by existing studies. In this paper, a novel method for on-line correction and uncertainties evaluation of the positions of spherical joint centers (SJCs) is presented. Firstly, the rough positions of SJCs are identified based on the nominal model, and the finite element analysis (FEA) method is applied to preliminarily compensate the self-weight deformation of the component. Secondly, the on-line correction model of SJCs is further established, majorly on the basis of the displacements of locators and the relative postures between the initial posture and the new posture after each motion. Thirdly, to improve the correction accuracy, a new relative posture evaluation model considering the anisotropic measurement uncertainties of key points is suggested and solved by particle swarm optimization, and the correction uncertainties are then analyzed using Monte Carlo simulation. According to the numerical experiments, the proposed relative posture evaluation method has demonstrated more robustness evaluation results than the conventional approaches, and also leads to lower correction uncertainties of SJCs. Moreover, since the relative posture evaluation is a common problem in robot calibration, it also provides a promising alternative or supplement for the conventional optimal posture selection method to improve calibration accuracy. The practical application for a wing to fuselage assembly has verified the effectiveness of the correction method, in which the largest positional error of SJCs has decreased from about 14.2 mm to less than 0.4 mm after correction, and the displacement calculation error has been accordingly reduced from 0.1 mm to smaller than 0.01 mm. Therefore, the security of posture adjustment in confined clearance has been largely enhanced.

Abstract: A post-buckling failure analysis framework was established to accurately and thoroughly capture the post-buckling deformation paths and failure processes as well as bearing capacities of composite stiffened panels under uniaxial compression. In this framework, the progressive damage method to thoroughly track the intra- and inter-laminar damage in laminates, the cohesive zone method to accurately examine the stiffener debonding damage, and the arc-length iteration algorithm to tracking the geometrical nonlinear post-buckling path, were all introduced. Post-buckling failure processes of a blade-stiffened panel and a large-scale hat-stiffened panel under uniaxial compression were systematically investigated. Computation cases with various damage models were designed and implemented, and the effects of intra- and inter-laminar damage, stiffener debonding, and their potential interactions on the post-buckling failure process of the stiffened panel were clarified. The predicted post-buckling failure processes of both panels were highly consistent with their experimental outcomes, thus giving evidence of the effectiveness of the failure analysis framework. It follows that a comprehensive failure mode characterization including intra- and inter-laminar damage, stiffener debonding should be all considered in a failure analysis framework for accurately predicting the failure of composite stiffened panels in engineering applications.

Abstract: In this paper, a combination process of automated fiber placement (AFP) of dry fiber and vacuum assistant resin infusion (VARI) was developed, that is firstly a dry fiber preform was fabricated by AFP, and then following a VARI and oven curing process to manufacture the final composite structures, which is expected to be an alternative proposal to the traditional autoclave process, thus making the manufacturing of high performance out-of-autoclave composite structures possible. This research devotes to analyze the character of AFP fabricated preform and its influence on the resin infusion process and the obtained composite. Firstly, the features of dry fiber tapes were analyzed, and a structure model was proposed to illustrate the key factors and issues during the coupled AFP/LCM process. Secondly, the effects of AFP fabricated preform on the resin infusion process and composite performance were analyzed by comparing with manually layup competitors using the same epoxy resin system. It has been demonstrated that the AFP processed preform helps to decrease the porosity from 2.00% to 0.6% and coefficient of thickness variation from 8.11% to 3.75% while improve the fiber volume fraction from 47.80% to 56.30%, however, it prolongs the injection time by 107.71% in this experiment due to lower permeability. Reasonable design of resin flow path and precise control of resin dosage are important for a successful resin infusion process based on AFP fabricated preform. The research can provide preliminary data accumulation and technical basis for further research and future application of AFP based LCM technology in airplane structures.

Abstract: The mechanical properties, especially the yield behavior, of AZ31B and ZK61 M magnesium alloys were comparatively investigated in this study. Series of uniaxial tension, uniaxial compression, shear and through-thickness compression (equi-biaxial tension) tests were conducted to obtain yield strengths and Lankford ratios (r values) under different strains and angles to their rolling directions and further the anisotropic characteristics as well as the tension-compression asymmetric features of the materials were analyzed. Furthermore, different yield criteria were adopted to represent yield behaviors of two magnesium alloys and their applicability on such magnesium alloys were compared. Results show that both magnesium alloys show apparent anisotropic and tension-compression asymmetric yield behavior. Compared with AZ31B, ZK61 M performs more remarkably in the anisotropic behavior and more intricately in tension-compression asymmetry and hardening features with changes of angles to the rolling direction and strain. The associated yield criteria of Hill1948, Yld2000-2D and CPB06 cannot concurrently represent anisotropic plastic yield and flow behaviors of AZ31B and ZK61 M magnesium alloys well; while the corresponding yield criteria based on non-associated flow rule can ideally describe these two aspects meantime. Among them, under tension and shear conditions, the non-associated Yld2000-2D criterion provided the most accurate predicting results than the other criteria. Regarding the tension-compression asymmetric characteristics of magnesium alloys, the non-associated model based on the CPB06 was introduced which makes concurrent prediction of tension-compression yield stress and Lankford ratio of these two materials possible. As a result, the comprehensive prediction capability of this model is fairly outstanding among all of three models. This study can provide basis for selection of plastic models, calibration technique and further application in numerical modeling.

Abstract: In order to realize automation of the pollutant emission tests of vehicles, a pedal robot is designed instead of a human-driven vehicle. Sometimes, the actual time-speed curve of the vehicle will deviate from the upper or lower limit of the worldwide light-duty test cycle (WLTC) target curve, which will cause a fault. In this paper, a new fault diagnosis method is proposed and applied to the pedal robot. Since principal component analysis (PCA), t-distributed stochastic neighbor embedding (t-SNE), and Autoencoder cannot extract feature information adequately when they are used alone, three types of feature components extracted by PCA, t-SNE, and Autoencoder are fused to form a nine-dimensional feature set. Then, the feature set is reduced into three-dimensional space via Treelet Transform. Finally, the fault samples are classified by Gaussian process classifier. Compared with the methods using only one algorithm to extract features, the proposed method has the minimum standard deviation, 0.0078, and almost the maximum accuracy, 98.17%. The accuracy of the proposed method is only 0.24% lower than that without Treelet Transform, but the processing time is 6.73% less than that without Treelet Transform. These indicate that the multi-features fusion model and Treelet Transform method is quite effective. Therefore, the proposed method is quite helpful for fault diagnosis of the pedal robot.

Abstract: The scattering coefficient, μs, the anisotropy factor, g, the scattering phase function, p(θ), and the angular and wavelength dependences of scattering intensity distributions of discrete particles in different size were systematically investigated from spectral range of 400 to 2400 nm as a function of wavelength, scattering angle, and scattering particle size using Mie theory and experimental parameters. The MATLAB-based codes using Mie theory for both spherical and cylindrical models were developed and applied for studying the light propagation and the key scattering properties of the discrete particles. The optical and structural parameters of tissue such as the index of refraction of cytoplasm, size of nuclei, and the diameter of the nucleoli for cancerous and normal human tissues obtained from the previous biological, biomedical, and bio-optic studies were used for Mie theory simulation and calculation. The wavelength dependence of scattering coefficient, anisotropy factor, and reduced scattering coefficients were investigated in the wide spectral range from 300 to 2400 nm. The scattering particle size dependence of μs, g, and scattering angular distributions was studied. The results show that larger size scattering particles have more contribution to the forward scattering in comparison with the smaller particles. In addition to the conventional simulation model that approximately considers the scattering particles as spheres, the cylinder model that is more suitable for fiber-like tissue frame components such as collagen and elastin was used for developing a computation code to study angular dependence of light scattering in turbid particle media and tissue for the first time.

Abstract: The effect of matrix cracking on the delamination morphology inside carbon fiber reinforced plastics (CFRP) laminates during low-velocity impact (LVI) is an open question. In this paper, the relationship between matrix cracking and delamination is studied by using cross-ply laminates. Several methods, including micrograph, C-scan, and visual inspection, were adopted to characterize the damage after LVI experiments. Based on the experimental results, finite element (FE) models were established to analyze the damage mechanisms. The matrix cracking was predicted by the extended finite element method (XFEM) and the Puck criteria, while the delamination was modeled by cohesive elements. It was revealed that the matrix crack in the bottom ply not only promoted the outward propagation of delamination but also contributed to the narrow delamination beneath the impact location. Multiple matrix cracks occurred in the middle ply. The ones close to the plate center initiated the delamination and prevented large-scale delamination beneath the impact location. For the cracks that were far away, no significant effect on delamination was found. In conclusion, the stress redistribution caused by the crack opening determines the delamination.

Abstract: The swept-and-leaned vanes and acoustic liners can both be used to reduce the turbofan noise. In this work, an analytical model was proposed under an idealized condition, in which an annular stator...

Abstract: This chapter focuses on the biological applications of optical-resolution photoacoustic microscopy (OR-PAM) system in brain in vivo label-free imaging. The OR-PAM system is mainly composed of photoacoustic (PA) imaging system and laser source. The solid-state nanosecond laser is widely used as the pumping source to generate efficient signal for PA effect. The application of OR-PAM system is presented to monitor the vascular disrupting agent (VDA) therapeutic effect of glioma tumor. This work illustrates the aspects of contrast agent–free, high spatial resolution and brain vascular imaging for OR-PAM in small animal model.

Abstract: Purpose This study tested the clinical implementation of the CoMac Communication System, an empirically validated tool for individualized Diabetes Self-Management Education and Support (DSMES). This system provides immediate feedback and guidance to health care providers (HCPs) to facilitate speaking with persons with type 2 diabetes mellitus in language reflecting patients' own worldviews and health beliefs. Patients and methods This 6-month implementation science study at an accredited diabetes care clinic in a Midwestern US hospital was conducted in two phases. Phase I consisted of CoMac implementation, qualitative interviews with HCPs, and evaluation of clinic flow among the diabetes education team. Seventy-two participants received CoMac's linguistically tailored patient-centric communication; a control group of 48 did not receive this intervention. In Phase II, glycosylated hemoglobin A1c (HbA1c) levels from the first visit to the follow-up visit for each group were compared. Results Interviews conducted during Phase I suggested that the system can be successfully implemented into DSMES practice. Knowing individual psychosocial profiles and participants' language use allowed for more effective patient counseling. In Phase II, multiple regression analysis with HbA1c change as the dependent variable showed that the key variable of interest, treated with the CoMac intervention, had a one-tailed t-value of -1.81, with a statistically significant probability value of 0.037. Conclusion Findings suggest that use of the CoMac System by diabetes care professionals has the potential for improved patient health outcomes. Patients receiving the CoMac intervention showed significantly improved HbA1c levels, suggesting that this approach has great promise for effective DSMES management.

Abstract: The proper tackling of rapid transients, such as voltage sags and swells, by protection systems of power grids that increasingly incorporate low-inertia renewable generators is a current concern in the power generation and metrology communities. In a previous paper, we have reported the characterization of a PMU calibration system that handles synchronized generation and sampling of signals with magnitude and phase step discontinuities. That calibrator employed an iterative parametric method that estimates the underlying phasor parameters, given a priori knowledge of the step location and an initial rough estimate of the phasor frequency. In this paper, we tackle the latter two problems and propose a method that blindly detects a step change from the phasor waveform and provides an accurate estimate of its location in time. Moreover, a simple method that yields a crude estimate of the phasor frequency is also proposed. We measured the accuracy of the estimates in simulated scenarios, including noisy signals,

Abstract: Airborne actuation system is one of the key flight control subsystems to realize flight attitude and trajectory control. Its performance directly affects the flight quality of aircraft. This paper discusses the influence of Electro-Hydrostatic Actuator (EHA) failure on flight performance of aircraft. This paper first describes the development of EHA, introduces its structure and working principle, decomposes the electro-hydrostatic actuator into the original component level, analyses and models them respectively, and proposes a fault injection scheme for possible faults. Finally, assuming that the actuator on the rudder of an aircraft fails, the impact on the flight performance of the aircraft is carried out. In this paper, the control performance of aircraft under different faults is simulated and analyzed, which provides a theoretical basis for fault-tolerant control of aircraft under faults.

Abstract: The present work focuses on the in-plane shear respond and failure mode of large size honeycomb sandwich composites which consist of plain weave carbon fabric laminate skins and aramid paper core. A special size specimen based on a typical element of aircraft fuselage was designed and manufactured. A modified in-plane shear test method and the corresponding fixture was developed. Three large size specimens were tested. The distributed strain gauges were used to monitor the mechanical response and ultimate bearing capacity. The results show that a linear respond of displacement and strain appears with the increase of the load. The average shear failure load reaches 205.68 kN with the shear failure occurring on the face sheet, and the maximum shear strain monitored on the composite plate is up to 16,115 μe. A combination of theoretical analysis and finite element method (FEM) was conducted to predict the shear field distribution and the overall buckling load. The out-of-plane displacement field distribution and in-plane shear strain field distribution under the pure shear loading were revealed. The theoretical analysis method was deduced to obtain the variation rule of the shear buckling load. A good agreement was achieved among the experiment, theoretical analysis, and FEM results. It can be concluded that the theoretical analysis method is relatively conservative, and the FEM is more accurate in case of deformation and strain. The results predicted by h element and p element methods are very close. The results of the study could provide data support for the comprehensive promotion of the design and application of honeycomb sandwich composites.

Abstract: In this paper, the emergence phenomenon in the assembly process was studied. First, we constructed the SIRS model of the assembly process and obtained the threshold condition of the extinction of defects through phase trajectory analysis. Second, we discretized the SIRS model and studied the emergence phenomenon during the assembly process. Third, the screening process was added to decrease the basic reproduction number in the SIRS model. It showed that the propagation of defects and emergence phenomenon could be suppressed to some extent through simulations. Finally, we found the relationship between the critical time point and other parameters during the assembly process, which is helpful for the assembly process.

Abstract: The development of modern civil jets is a complicated task accompanied with the processing of various requirements, the use of large quantities of new advanced technologies and the intense integration of systems. To focus the critical issues at the beginning of the design, the civil jet top level design requirements should be identified and defined reasonably. Based on systems engineering method, the civil jet top level design requirements are researched, including the purpose, the position in the requirements system, the basic contents, the requirements validation process and the setup of work team. So far, the research results have been successfully applied in civil jet development in China, and effectively improve the efficiency of civil jet product development.

Abstract: In order to establish the basic data architecture for aircraft in-service configuration management, ensuring efficient implementation of it, the characteristics of configuration change caused by various maintenance and support operation during the service phase of large civil aircraft were analyzed. On this basis, formal classification of in-service aircraft configuration data was carried out. Based on the product structure tree, the architecture of the aircraft configuration data was constructed. The in-service aircraft configuration data schema was defined. By introducing the idea of Skyline query, the configuration change information filtering method was designed and implemented. Finally, method validation was performed by the maintenance and support data of an airline company. The results show that, the automatic extraction of configuration change information is realized effectively, ensuring the full integration of the in-service aircraft configuration data schema and production and maintenance information management, and ensuring the real-time and consistency of in-service aircraft configuration data management.

Abstract: A new rotational field planar eddy current probe is proposed. The probe is combined with two orthogonal driver traces and a pickup coil that includes two-circular sector windings with series connection. Rotational eddy currents are induced by driver traces of the same amplitude and frequency, but fed with 90° phase different alternating exciting currents. An experimental demonstration using prototypes of the probes and artificial defects showed that the probe with a two-circular sector pickup coil is more sensitive for detecting the short defects than the probe with a circular pickup coil.

Abstract: This paper rigorously establishes that, by increasing the number of dendritic branches, we can achieve an infinite approximation to any continuous function with any accuracy. In other words, the accuracy can be improved by using one neuron with more dendritic branches under the premise of using the backpropagation neural network theory.

Abstract: Quasi-static 4-point bending behaviors and failure characteristics of a large scale composite C-beams fastened with multi-bolt joints were investigated experimentally and numerically. Strain gauge measurement and acoustic emission (AE) monitor system were used to monitor the mechanical response and damage development during loading process. The global and local characteristics of damage are presented and analyzed. A nonlinear numerical model with simplified bolt joints on ABAQUS platform was also established which could be used to efficient analyze the load distribution of bolts and accurately predict the nonlinear response of the composite C-section beams. The numerical results were verified by the experimental results within 10% error. From the finite element (FE) model results, the bolt load distribution and load transfer path were discussed. The results show that the surface skins of the beam take a higher portion of the load than beam web under pure bending load. The beam catastrophic failure is due to the bending load matches the compressive strength of the top composite skin. The FE model is capable to well catch mechanical response details of multi-bolts joint structures for engineers.

Abstract: In this paper, the design concept of the aileron with a fixed connector and a moving connector has been explored due to the improvement of aileron effectiveness. As usual, aileron reversal or the blocking phenomenon of multijoint fixed ailerons is a hard nut to crack. In the present research, in order to improve aileron effectiveness, several examples are studied. The connection position influences the stress, displacement, load distribution, and control effectiveness of the aileron or critical flutter speed. As the joint positions are different, the wing-aileron connection stiffness is also changing. The sample of the beam shows the weight reduction. The plate simulation indicates the decreased deformation and the better load distribution. The aileron trimming demonstrates the improvement of aileron effectiveness. And the flutter speed coupled with the aileron is different. All of these examples indicate the feasibility of this new concept of the aileron design, which means improving aileron effectiveness based on changing the position of aileron connectors. Finally, three different modes for wing-aileron connections are suggested for reference.

Abstract: Fault detection of rotating machinery is very important for its performance degradation assessment. In this work, an effective feature learning and detecting method based on the ensemble empirical mode decomposition (EEMD) and Gaussian process classifier (GPC) is put forward. Compared with the traditional parameter optimization methods of GPC, this work proposed a bacterial foraging optimization as the optimal solution of the hyperparameters of GP model. To find a valid feature vector, this work also utilized EEMD to decompose the vibration signals and get some time‐frequency features. Then, treelet transform is proposed to reduce the feature dimension. The results of some applications indicate that the EEMD has stronger processing capability of the status signals of rotating machinery. Treelet can transform the high‐dimensional vector to low‐dimensional space, which is used as the input of the proposed BFO‐GP model. The proposed diagnosis method can identify not only the optimal feature vector but also the fault locations.