Abstract: This paper reports the ballistic penetration behavior of 2D basalt fiber plain woven composite (2DPWC). The residual velocity vs. strike velocity curve was recorded. The dissipated energy was also calculated for each strike velocity. Furthermore, the impact damage morphologies of the tested 2DPWC coupons were given to indicate the damage modes and the mechanisms of energy absorption.

Abstract: This paper investigates the feasibility and capability of the prediction error identification for modal parameter estimation and flutter prediction. The prediction error identification is effective for the construction of AutoRegresive eXogeneous (ARX), AutoRegresive Moving Average eXogeneous (ARMAX), and Box-Jenkins models. Because of the polynomial matrix format of these model structures, the physical modes contained in the processed signals can be easily estimated and extracted with the correct setting of the parameter constraints and using the stabilization diagram during the modal parameter estimation. In addition, severalflutter prediction methodologies such as Zimmerman-Weissenburger flutter margin, damping trends extrapolation, peaking-holding subcritical response method are discussed and further evaluated with the application to the Aerostructure Test Wing.

Abstract: A unified robust structural, trim relationship and controller design methodology is presented for a MIMO aeroservoelastic system. It contains two stages in an iterative procedure: (1) robust structure and trim relationship optimization, and (2) robust controller design based on the optimal structure. The objective of the unified robust aeroservoelastic design is to obtain a minimum structure weight, under constraints on stability and performance specifications, and with structural and trim parameter uncertainties. Robustness is reflected in the fact that the weight variance is restricted to a small range and all the constraints are met when the design variables are uncertain. A genetic algorithm and sensitivity data were used in this open loop robust design stage. For the robust controller design, the well-known linear fractional transformation is used to interconnect uncertainty models for the structure and trim parameters with the other nominal aeroservoelastic model. Finally, the μ synthesis is applied to design a robust controller, which provides robust stability and instaneous closed-loop performance, under reasonable stress limitations. A flight vehicle with four control surfaces was tested to validate this methodology. After robust aeroservoelastic design, the aircraft is 3.62% heavier than the structure optimized by nominal method without consideration of uncertainty. However all the constraints are satisfied by the robust optimization, when the design variables are perturbed in a 5% uncertainty range. Hence, the structure is more robust to resist design variable uncertainties. The robust controller provided simultaneous high roll-rate performance and reduced the wing-root stress by 58.3% , when compared with the performance and stress of the openloop aeroelastic system.

Abstract: . The mean flow properties agree well with the experimental measurements. The characteristics of aerodynamic noise are investigated at various angles of attack. The obtained results show that inclining the airfoil could enlarge turbulent intensity and produce larger scale of vortices. Noise sources are identified in the region of flow separation and reattachment and also in the wake flow. The sound radiation is mainly towards the upper and lower directions of the airfoil surface. At higher angle of attack, the tonal noise tends to disappear and the noise spectrum displays broad-band features.

Abstract: This paper describes a methodology developed for calibrating optical detector for light engineering, especially for devices used at low level light, including auroral imager, star sensor, astronomical camera and similar optical instruments. In order to know the physical meaning of optical sensor output, calibration is the first and most important process in a complete analysis of observed data. It is found that optical sensors, like CCDs, are not perfectly linear systems as they were assumed. After bias frame subtraction, the number of ADU counts is not exactly proportional to the number of incident photons. A key component of this paper is non-linearity correction. One of current applications using this method is auroral imager which is used for measuring aurora, high-altitude clouds, and other atmospheric optical objects light intensity, which is the first step to complete an optical object tomography simulation.

Abstract: This paper describe a design of aircraft drilling end-effector (ADEE) based on flexible railway which is mainly used for drilling on the surface of fuselage and wing of aircraft. The whole system is composed of several different modules. Flexible railway module (FRM) make ADEE move to any places where need to be drilled. Framework and Z axis module (FZM) uses high-rigidity framework and linear slide guide to guarantee the precision and stability of the drilling action. Compression and absorbing chipping module (CACM) adopts symmetric double-cylinder structure and generates 1000N compressing forces that can compress three layers aircraft skin and is increased by demand. Vacuous absorbing chipping mechanism uses high flow vacuum generator as vacuum air source and filters metal shavings by filter. Visual inspection module (VIM) can precisely calculate the distance between three points around drill bit and finished surface by calculating, and then achieves verticality deviation value through normal detection algorithm. Binary angular adjustment module (BAAM) revises angle deviation that is caused by the differences of adsorption position diameter of two rows of rack. ADEE is more flexible and better adaptable; meanwhile, it can greatly improve the efficiency and precision of the holes. It does not use drilling fluids in the whole manufacturing process and fundamentally eliminates the pollution problem of the drilling fluid. In conclusion, experiments show that ADEE can meet the requirements of automatic drilling of departments of aircraft and greatly enhance the quality and speed of drilling holes.

Abstract: An experimental and analytical study on ultimate tensile strength of composite double-lap joints with different adhesive thicknesses is employed in the paper，test results indicate the major failure mode of joints is adhesive shear failure and the ultimate strength of joints increasing with thicker adhesive. Analytical model is developed to investigate the adhesive failure of double-lap joint based on the experiments. The model takes into account anisotropy of each ply in the composite laminates and elastic-perfectly plastic behavior of the adhesive in the joints. The validity of analytical model for calculating shear strain/stress distribution is certified by comparing with finite model results. Maximum shear strain criterion is adopted in the analytical model to predict the ultimate tensile load of double-lap joint. Good agreement of the analytical predictions with the experimental results is obtained.

Abstract: The M219 cavity benchmark problem is used to compare the performance and the applicability of two commercial software, namely Ansys Fluent and Exa Powerflow. The computational domain is small and is concentrated around the cavity to limit the computation time and thus permit to assess the possibility of carrying out such simulations in an industrial context. Despite the small length of the domain, far-field conditions are imposed at the open boundaries which induces some unphysical pressure wave reflections. On the reference cavity case (Ma=0.85, P=62900), the second and third tones are well captured but the background noise and sound pressure level are higher than previously mentioned in the literature. Wave reflection and boundary layer features are thought to be the main causes of these discrepancies. A case at Mach number equal to 0.30 was carried out; Fluent and Powerflow present similar results in terms of acoustics characteristics. The mean flow computation shows slight differences which are certainly due to different boundary layers attacking the cavity leading edge.

Abstract: This paper reports on the design and implementation of an inverted pyramid display for group learning. It is composed of an image generation subsystem, an image reflection subsystem and a software rendering engine. Various 3D models can be loaded into the system and rendered in real-time by the software into four correlative images, each for one side of the inverted pyramid. The display is made of thin semi-transparent acrylic panels. The reflected images appear inside the pyramid and appear to float in mid-air. Users surrounding the display can view different sides of the 3D models and interact with them. Meanwhile, users can see through the display to communicate with each other easily. This kind of design provides an interactive platform for a group of learners to discuss and understand 3D structures and phenomena. This is quite different from existing reflection-based displays, which are mainly designed for exhibition and advertising. Our display system is designed for group learning and facilitates more user communication and interaction.

Abstract: The mechanical response and damage mechanism of a 3D multi-structured knitted composite under quasi-tensile loadings are investigated based on experimental results. The multi-structured knitted composite consists of two knitted fabrics with weft double-faced interlock knitted fabric as core material and biaxial warp-knitted fabric as surface layer in the above-mentioned composite system, respectively. The tensile stress against strain curve is obtained to analyze the mechanical behavior. Furthermore, the failure mechanisms of 3D multi-structured knitted composite are discussed from the experimental observations by the initiation and propagation of damaged zone in knitted composites.

Abstract: A self-learning fractal interpolation algorithm to construct synthetic fields with statistical properties close to real turbulence is proposed. Different from our previous work [Phys. Rev. E 84 (2011) 026328, 82 (2010) 036311], the position mapping and stretching factors between the adjacent large and small scales are learned from the initial information. Using this method, a turbulence-like field with K41 spectra and without dissipation is constructed well through a coarse grid velocity signal from one experiment's data. After filtering the interpolated signal appropriately, the probability distribution of velocity, velocity structure functions and the anomalous scaling law of the synthetic field are close to those of the original signal.

Abstract: This paper presents a new retrieval algorithm for unfolded sheet metal parts. The primary idea of this novel algorithm is based on the relative position relationships of features in sheet metal parts. After analyzing the data structure of sheet metal parts, some kinds of key features are abstracted and the relative position model is described to express the difference of features’ relative position. Further, detailed information about the position model and the formula of similarity developed for difficult sheet metal parts is given and described. Also an example is given at the last of paper to verify the validity of our algorithm. Obviously, our new algorithm meets the requirements of searching unfolded sheet metal parts.

Abstract: This paper proposes a new GPU method for the evaluation and LOD (Level of Detail) rendering of NURBS surfaces. Compared with the existing evaluation method of basis function, the approach simplifies the process by just one-pass and saves the graphics memory with only one texture array. The wavelet based LOD rendering method also saves the time to re-evaluate and re-transfer the data for rendering.