Numerical Modelling of the Impact Behaviour of High Aspect Ratio Aluminium Foam Filled Sections

2009 ◽  
Author(s):  
F. Teixeira-Dias ◽  
V. Miranda ◽  
J. Pinho-da-Cruz
Keyword(s):  
Aspect Ratio ◽  
Numerical Modelling ◽  
High Aspect Ratio ◽  
Aluminium Foam ◽  
Impact Behaviour ◽  
Foam Filled ◽  
The Impact

Impact Response and Energy Absorption of Aluminium Foam-Filled Tubes

2012 ◽  
Vol 152-154 ◽  
pp. 436-439 ◽  
Author(s):  
Yang An ◽  
Cui E Wen ◽  
Peter D. Hodgson ◽  
Chun Hui Yang
Keyword(s):  
Energy Absorption ◽  
Experimental Test ◽  
Computational Simulation ◽  
Aluminium Foam ◽  
Impact Response ◽  
Composite Tubes ◽  
Impact Behaviour ◽  
Foam Filled ◽  
The Impact

The effect of foam fillers on the impact behaviour and energy absorption of an aluminium tube is investigated. Both experimental test and computational simulation are employed in current study. For comparison, hollow tubes and foams are also tested, respectively. Foam filler is found to be ineffective in increasing the crushing loads of the composite tubes over the simple superposition of the crushing loads of hollow tube and foam. Also, foam filler increases the tendency for the concertina mode of folding. The foam fillers of tubes additionally result in increasing the SAE values over those of hollow tubes.

The Effect of Structural Geometric Nonlinearities on the Flutter of the Straight and Swept Wing Configurations

2012 ◽  
Vol 189 ◽  
pp. 306-311 ◽  
Author(s):  
Qing Guo ◽  
Bi Feng Song
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Swept Wing ◽  
Geometric Nonlinearities ◽  
Air Vehicle ◽  
Structural Nonlinearity ◽  
Flutter Analysis ◽  
Long Endurance ◽  
The Impact ◽  
Straight Wing

High altitude and long endurance (HALE) vehicle always adopt straight or swept configuration, which leads to the problem that the wings of UAV have high aspect ratio and are very flexible. This kind of flexible wing exhibits large deformation when aerodynamic forces are loaded on them and the structural nonlinearity should be considered. So the dynamic and flutter characteristics will be changed. In the engineering applications, the effects of structural geometric nonlinearities on the air vehicle design are the most concerns of aeroelasticity before a systematic flutter analysis for the air vehicle. because the solution for nonlinear flutter speed based on the CFD-CSD method is complex and time consuming. In this paper, we propose a simple and efficient approach that can analyze the effect of structural geometric nonlinearities on the flutter characteristics of high aspect ratio wing quickly. And a straight wing and a straight-swept wing are analyzed to verify the feasibility and efficiency of the proposed method. It is found that the effect of structural geometric nonlinearities has a strong effect on the flutter characteristic of the straight wing, but is weak on the straight-swept wing. And finally the impact of swept angle on the dynamic and flutter characteristics of straight-swept wing is also discussed.

The Use of Turbulent Inlet Boundary Conditions for the Modelling of High Aspect Ratio Free Jets

2004 ◽  
Author(s):  
Arne E. Holdo̸ ◽  
Govert de With
Keyword(s):  
Aspect Ratio ◽  
Numerical Modelling ◽  
Boundary Conditions ◽  
High Aspect Ratio ◽  
A Priori ◽  
Velocity Signal ◽  
Eddy Simulation ◽  
Boundary Velocity ◽  
Mesh Resolution ◽  
Inlet Conditions

There are many practical situations when jets are emanating from non-axis-symmetric apertures. The complexities associated to the numerical modelling of a high aspect ratio jet is embedded in its physical complexity. Consequently, the numerical modelling does not only require a high mesh resolution, but furthermore it requires a careful construction of the inlet boundary velocity. The present work consists of a series of Large Eddy Simulation (LES) simulations using different inflow boundary conditions. This work is aimed to find suitable inlet boundary conditions which resemble the turbulent features that can be expected near the jet orifice. The turbulent inlet conditions are constructed by means of a variable velocity. The velocity profile is constructed such that the statistical quantities for turbulence are satisfied, this includes a correct turbulent intensity of the velocity signal and an ‘a priori’ selected frequency spectrum. Experimental work of Quinn et al. (5) is used to validate the computational data.

scholarly journals The Capabilities of Electrodischarge Microdrilling of High Aspect Ratio Holes in Ceramic Materials

2015 ◽  
Vol 6 (3) ◽  
pp. 61-69 ◽  
Author(s):  
Sebastian Skoczypiec ◽  
Magdalena Machno ◽  
Wojciech Bizoń
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Efficiency ◽  
Ceramic Materials ◽  
Good Alternative ◽  
Discharge Voltage ◽  
Drilling Speed ◽  
Electrically Conductive ◽  
Side Gap ◽  
The Impact

Abstract In the first part of the article the review of ceramic materials drilling possibilities was presented. Among the described methods special attention is paid to electrodischarge drilling. This process have especially been predicted for machining difficult-to-cut electrically conductive materials. The second part consist of the results analysis of electrodischarge microdrilling of siliconized silicon carbide. The experiment involves the impact of current amplitude, discharge voltage and pulse time on the hole depth, side gap, linear tool wear and mean drilling speed. The results shows that electrodischarge drilling is a good alternative when machining inhomogeneous ceramic materials and gives possibility to drill high aspect ratio holes with relatively high efficiency (the drilling speed >2 mm/min).

Through-Silicon-Via Copper Deposition for Vertical Chip Integration

2006 ◽  
Vol 970 ◽  
Author(s):  
Bioh Kim
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Seed Layer ◽  
Copper Deposition ◽  
Process Conditions ◽  
Through Silicon Via ◽  
3D Packaging ◽  
Wafer Thinning ◽  
The Impact ◽  
Deposition Conditions

ABSTRACTConsumers are demanding smaller, lighter electronic devices with higher performance and more features. The continuous pressure to reduce size, weight, and cost, while increasing the functionality of portable products, has created innovative, cost-effective 3D packaging concepts. Among all kinds of 3D packaging techniques, through-silicon-via (TSV) electrodes can provide vertical connections that are the shortest and most plentiful with several benefits (1). Connection lengths can be as short as the thickness of a chip. High density, high aspect ratio connections are available. TSV interconnections also overcome the RC delays and reduce power consumption by bringing out-of-plane logic blocks much closer electrically.The technologies engaged with TSV chip connection include TSV formation, insulator/barrier/seed deposition, via filling, surface copper removal, wafer thinning, bonding/stacking, inspection, test, etc. Process robustness and speed of copper deposition are among the most important technologies to realize TSV chip integration. There are generally three types of via filling processes; lining along the sidewall of vias, full filling within vias, and full filling with stud formation above the via. Here, the stud works as a mini-bump for solder bonding. Two methodologies have been generally adopted for via filling process; (a) via-first approach : blind-via filling with 3-dimensional seed layer, followed by wafer thinning and (b) thinning-first approach : through-via filling with 2-dimensional seed layer at the wafer bottom after wafer thinning. Currently, the first approach is more popular than the second approach due to difficulty in handling and plating thinned wafers (2).We examined the impact of varying deposition conditions on the overall filling capability within high aspect ratio, deep, blind vias. We tested the impacts of seed layer conformality, surface wettablity, bath composition (organic and inorganic components), waveform (direct current, pulse current, and pulse reverse current), current density, flow conditions, etc. Most deposition conditions affected the filling capability and profile to some extent. We found that reducing current crowding at the via mouth and mass transfer limitation at the via bottom is critical in achieving a super-conformal filling profile. This condition can be only achieved with a proper combination of aforementioned process conditions. With optimized conditions, we can repeatedly achieve void-free, bottom-up filling with various via sizes (5-40μm in width and 25-150μm in depth).

Post Titanium Silicide Processing

1995 ◽  
Vol 402 ◽  
Author(s):  
G. Grynkewich ◽  
V. Ilderem ◽  
M. Miller ◽  
S. Ramaswami
Keyword(s):  
Aspect Ratio ◽  
Contact Resistance ◽  
Process Parameters ◽  
High Aspect Ratio ◽  
Film Formation ◽  
Titanium Silicide ◽  
Fluorocarbon Polymer ◽  
Sidewall Angle ◽  
The Impact ◽  
Etch Profile

AbstractDecreasing contact dimensions coupled with the need for planarization to accommodate multiple layers of metal have created many challenges for the contact etch module. For example, contact etch processes are often required to stop on thin titanium silicide while at the same time forming high aspect ratio, straightwalled contacts. In this paper, the impact of various dielectric compositions and contact etch process parameters on etch profile, selectivity, and contact resistance is presented for the formation of high aspect ratio, submicron contacts to thin TiSi2 layers. The etch profile is formed by RIE using a mixture of CHF3 and various amounts of CF4. Surprisingly, the sidewall angle and selectivity to silicide showed little dependence on the percent CF4. Contact resistance measurements, however, varied greatly with percent CF4 and contact aspect ratio. The variation of contact resistance with etch chemistry was attributed to a variation in the extent of fluorocarbon polymer film formation, which in turn depends on the ratio of carbon to fluorine in the plasma. Finally, post contact etch treatments were examined for efficiency in removing the polymer films from the high aspect ratio contacts.

scholarly journals Analysis of the impact of inhomogeneous emissions in a semi-parameterized street canyon model

2015 ◽  
Vol 8 (2) ◽  
pp. 935-977
Author(s):  
T.-B. Ottosen ◽  
K. E. Kakosimos ◽  
C. Johansson ◽  
O. Hertel ◽  
J. Brandt ◽  
...  
Keyword(s):  
Air Pollution ◽  
Aspect Ratio ◽  
Theoretical Calculation ◽  
Real World ◽  
High Aspect Ratio ◽  
Street Canyon ◽  
The Other ◽  
Width Ratio ◽  
Improved Performance ◽  
The Impact

Abstract. Semi-parameterized street canyon models, as e.g. the Operational Street Pollution Model (OSPM®), have been frequently applied for the last two decades to analyse levels and consequences of air pollution in streets. These models are popular due to their speed and low input requirements. One often used simplification is the assumption that emissions are homogeneously distributed in the entire length and width of the street canyon. It is thus the aim of the present study to analyse the impact of this assumption by implementing an inhomogeneous emission geometry scheme in OSPM. The homogeneous and the inhomogeneous emission geometry schemes are validated against two real-world cases: Hornsgatan, Stockholm, a sloping street canyon; and Jagtvej, Copenhagen; where the morning rush hour has more traffic on one lane compared to the other. The two cases are supplemented with a theoretical calculation of the impact of street aspect (height / width) ratio and emission inhomogeneity on the concentrations resulting from inhomogeneous emissions. The results show an improved performance for the inhomogeneous emission geometry over the homogeneous emission geometry. Moreover, it is shown that the impact of inhomogeneous emissions is largest for near-parallel wind directions and for high aspect ratio canyons. The results from the real-world cases are however confounded by challenges estimating the emissions accurately.

Investigation of Computational Non-Linear Aeroelastic Response of High Aspect Ratio Wing

2013 ◽  
Vol 419 ◽  
pp. 55-61
Author(s):  
Hammad Rahman ◽  
Min Li
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Parametric Design ◽  
Aerodynamic Load ◽  
Linear Deformation ◽  
Aeroelastic Response ◽  
Simplified Approach ◽  
Strip Theory ◽  
Non Linear ◽  
The Impact

Aircrafts with high aspect ratio wings are most eligible candidates for high altitude and long endurance flights. Such wings show a non-linear deformation behavior because of structural geometric non-linearity. In the present study both linear and non-linear static aeroelastic behaviors of a high aspect ratio rectangular flat plate wing are analyzed using a simplified approach. The main emphasis lies in the tremendous change of lift distribution on the flexible high aspect ratio wing when large deflections are incorporated in the static aeroelastic analysis. The computational static aeroelastic simulations are performed in the finite element method based commercial software ANSYS-14. The aerodynamic load is calculated using the strip theory. Since the aero-load changes with the twisting deformation hence a user defined script is written using ANSYS parametric design language (APDL). The computationally achieved divergence velocity results are compared with the analytical results. The results of parametric study at different flight load conditions and angles of attack have highlighted the role of geometric nonlinearities in both bending and twisting deformations. The impact of follower pressure forces on the aeroelastic response is also investigated.

scholarly journals Stability Analysis and Augmentation Design of a Bionic Multi-Section Variable-Sweep-Wing UAV Based on the Centroid Self-Trim Compensation Morphing

2021 ◽  
Vol 11 (19) ◽  
pp. 8859
Author(s):  
Hang Ma ◽  
Yuxue Ge ◽  
Bifeng Song ◽  
Yang Pei
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Speed ◽  
Stability Margin ◽  
Static Stability ◽  
Sweep Angle ◽  
Stability Performance ◽  
Angle Change ◽  
Stability Change ◽  
The Impact

In this study, a design scheme for a high-aspect-ratio bionic multi-section variable-sweep wing unmanned aerial vehicle (UAV) that utilizes the reverse coordinated change in the sweep angle of the inner and outer wing sections is proposed, which improves the aerodynamic performance and realizes the self-trim compensation of the wing’s centroid. According to the layout characteristics of this type of UAV, a reasonable distribution design of the wingspan ratio of the inner and outer sections is explored, to reduce the impact of aerodynamic center movement and moment of inertia change. The calculation and analysis results show that the coordinated variable-sweep scheme can significantly improve the influence of sweep angle change on the longitudinal static stability margin of UAVs with a high aspect ratio. The coordinated sweep angle change in the inner and outer wing sections can not only reduce the drag during high-speed flight, but also play a significant role in improving the performance of the aircraft at different stages in the mission profile. Appropriately increasing the wingspan proportion of the inner section can reduce the trim resistance of the V-tail, reduce the thrust of the engine, and increase the range and duration of the UAV. From the perspective of stability change, the multi-section variable-sweep wing UAV with a wingspan ratio of the inner and outer sections that is between 1.41 and 1.78 has better dynamic stability performance. Among them, the UAV with a wingspan ratio of the inner and outer sections that is equal to 1.41 has better longitudinal stability performance, while the UAV with a wingspan ratio of the inner and outer sections that is equal to 1.78 has better lateral/directional stability performance.

Sign in / Sign up

Export Citation Format

Share Document