scholarly journals Development of a Morphing Landing Gear Composite Door for High Speed Compound Rotorcraft

Aerospace ◽  
2020 ◽  
Vol 7 (7) ◽  
pp. 88
Author(s):  
Antonio Chiariello ◽  
Salvatore Orlando ◽  
Pasquale Vitale ◽  
Mauro Linari ◽  
Raffaele Longobardi ◽  
...  
Keyword(s):  
High Speed ◽  
Landing Gear ◽  
Open Door ◽  
Load Step ◽  
Low Velocity ◽  
Structural Shape ◽  
Aerodynamic Surfaces ◽  
Novel Design ◽  
Stressed Field ◽  
Multiple Load

In the framework of fast rotorcraft, smoothness and flushness of external aerodynamic surfaces present challenges for high-speed conditions, where aerodynamics is the driver of helicopter performance. For AIRBUS-RACER helicopter the main landing gear trap doors are parts of the lower wing skins (in retracted configuration) affecting helicopter performance by minimizing the drag. Flushness requirements must not be in contrast with the functionally of the Landing gear system that must open and close the doors during the landing gear retraction-extension phases at moderately low velocity. To manage these goals, a novel design logic has been identified to support the trap doors development phase. The identified way to proceed needs of relevant numerical method and tool as well. This method is aimed at identifying the main landing gear composite compartment doors in pre-shaped configuration to match the smoothness and door-stopper engagements over each aerodynamic conditions. The authors propose a detailed non-linear Finite Element method, based on MSC Nastran (MSC Software, Newport Beach, US) SOL-400 solver in which the structure is modelled with deformable contact bodies in a multiple load step sequence, open door condition and pre-shaped, deformed under actuator pre-load, under flight load conditions. The method includes the entire pre-stressed field due to the preload and the actual door stiffness, considering the achieved large displacement to verify the most representative strain field during loads application. The paper defines a robust methodology to predict the deformation and ensure the most appropriate door “pre-bow” and pre-load, in order to achieve the desiderated structural shape that matches aerodynamic requirements. The main result is the identification of a pre-shaped doors configuration for the Airbus RACER Fast Rotorcraft.

Synthesis of Inertially Compensated Variable-Speed Cams

2003 ◽  
Vol 125 (3) ◽  
pp. 593-601 ◽  
Author(s):  
B. Demeulenaere ◽  
J. De Schutter
Keyword(s):  
High Speed ◽  
Design Procedure ◽  
Variable Speed ◽  
Speed Variation ◽  
Design Choice ◽  
Cam Follower ◽  
Speed Fluctuation ◽  
Novel Design

Traditionally, cam-follower systems are designed by assuming a constant camshaft speed. Nevertheless, all cam-follower systems, especially high-speed systems, exhibit some camshaft speed fluctuation (despite the presence of a flywheel) which causes the follower motions to be inaccurate. This paper therefore proposes a novel design procedure that explicitly takes into account the camshaft speed variation. The design procedure assumes that (i) the cam-follower system is conservative and (ii) all forces are inertial. The design procedure is based on a single design choice, i.e., the amount of camshaft speed variation, and yields (i) cams that compensate for the inertial dynamics for any period of motion and (ii) a camshaft flywheel whose (small) inertia is independent of the period of motion. A design example shows that the cams designed in this way offer the following advantages, even for non-conservative, non-purely inertial cam-follower systems: (i) more accurate camshaft motion despite a smaller flywheel, (ii) lower motor torques, (iii) more accurate follower motions, with fewer undesired harmonics, and (iv) a camshaft motion spectrum that is easily and robustly predictable.

scholarly journals Tactile Occupant Detection Sensor for Automotive Airbag

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5288
Author(s):  
Naveen Shirur ◽  
Christian Birkner ◽  
Roman Henze ◽  
Thomas M. Deserno
Keyword(s):  
High Speed ◽  
Tactile Sensors ◽  
Low Velocity ◽  
Speed Test ◽  
Multi Stage ◽  
The Matrix ◽  
Contact Data ◽  
Single Sensor ◽  
Matrix Sensor ◽  
Contact Position

Automotive airbags protect occupants from crash forces during severe vehicle collisions. They absorb energy and restrain the occupants by providing a soft cushion effect known as the restraint effect. Modern airbags offer partial restraint effect control by controlling the bag’s vent holes and providing multi-stage deployment. Full restraint effect control is still a challenge because the closed-loop restraint control system needs airbag–occupant contact and interaction feedback. In this work, we have developed novel single and matrix capacitive tactile sensors to measure the occupant’s contact data. They can be integrated with the airbag surface and folded to follow the dynamic airbag shape during the deployment. The sensors are tested under a low-velocity pendulum impact and benchmarked with high-speed test videos. The results reveal that the single sensor can successfully measure occupant–airbag contact time and estimate the area, while the contact position is additionally identified from the matrix sensor.

scholarly journals Risk factors and preventive measures for C5 palsy after cervical open-door laminoplasty

2020 ◽  
Vol 32 (4) ◽  
pp. 592-599
Author(s):  
Hideaki Nakajima ◽  
Hiroyuki Kuroda ◽  
Shuji Watanabe ◽  
Kazuya Honjoh ◽  
Akihiko Matsumine
Keyword(s):  
Spinal Cord ◽  
High Speed ◽  
Facet Joint ◽  
Patient Characteristics ◽  
Lateral Side ◽  
Intervertebral Foramen ◽  
Open Door ◽  
C5 Palsy ◽  
Articular Process ◽  
Preoperative Ct

OBJECTIVEThe pathomechanism of C5 palsy after cervical open-door laminoplasty is unknown despite the relatively common occurrence of this condition postoperatively. The aim of this study was to review clinical and imaging findings in patients with C5 palsy and to propose countermeasures for prevention of this complication.METHODSBetween 2001 and 2018, 326 patients with cervical myelopathy underwent cervical laminoplasty at the authors’ hospital, 10 (3.1%) of whom developed C5 palsy. Clinical features and radiological findings of patients with and without C5 palsy were analyzed.RESULTSIn patients with C5 palsy, the width of the C5 intervertebral foramen was narrower and the position of the bony gutter was wider beyond the medial part of the C5 facet joint. The distance between the lateral side of the spinal cord and bony gutter was significantly greater in patients with C5 palsy. Patient characteristics, disease, cervical alignment, spinal canal expansion rate, anterior protrusion of the C5 superior articular process, high-intensity area in the spinal cord on T2-weighted MR images, posterior shift of the spinal cord, and operative time did not differ significantly between patients with and without C5 palsy.CONCLUSIONSThe position of the bony gutter may have a central role in the pathomechanism of postoperative C5 palsy, especially in patients with a narrow C5 intervertebral foramen. Making an excessively lateral bony gutter might be a cause of C5 nerve root kinking at the intervertebral foramen. To prevent the occurrence of C5 palsy, it is important to confirm the medial line of the facet joint on the preoperative CT scan, and a high-speed burr should be started from inside of the facet joint and manipulated in a direction that allows the ligamentum flavum to be identified.

scholarly journals Experimental Technique for Dynamic Fragmentation of Liquid-Driving Expanding Ring

2018 ◽  
Vol 183 ◽  
pp. 02034 ◽  
Author(s):  
Jia Zhang ◽  
Yuxuan Zheng ◽  
Fenghua Zhou ◽  
Jun Liu
Keyword(s):  
High Speed ◽  
Fracture Morphology ◽  
Hydraulic Cylinder ◽  
Low Velocity ◽  
Ductile Materials ◽  
Dynamic Fragmentation ◽  
Circumferential Tensile Stress ◽  
Metallic Ring ◽  
Pressure Bar ◽  
Experimental Technology

Expanding ring experiment is an important method for dynamic fragmentation of solid under 1D tensile loading. Based on the split Hokinson pressure bar (SHPB), a liquid-driving experimental technology was developed for conducting expanding ring tests. The loading fixture includes a hydraulic cylinder filled with water, which is pushed by a piston connected to the input bar. As the water is driven, it expands the metallic ring specimen in the radial direction. The approximately incompressible property of the water makes it possible to drive the specimen in very high radial velocity by low velocity movement of piston, according to the large sectional area ratio of the cylinder to specimen. Using liquid-driving expanding ring device, 1060 aluminum rings (ductile materials)/PMMA rings (brittle materials) were fragmented and the fragments were recovered. Impact deformation of free-flying fragments was avoided through the use of “sample soft-capture” technology. The fragmentation process was observable by high speed camera through modifying the driving direction of the water. From the observations of the fracture morphology and the residual internal cracks of the recovered fragments, it is concluded that the fracture of the rings is caused by the circumferential tensile stress.

scholarly journals Distribution of cyprinids in the stream during their spring upstream migration

2020 ◽  
Vol 164 ◽  
pp. 07029
Author(s):  
Andrey Chemagin
Keyword(s):  
High Speed ◽  
Western Siberia ◽  
Fish Population ◽  
Upstream Migration ◽  
Low Velocity ◽  
Body Sizes ◽  
Velocity Characteristic ◽  
Irtysh River ◽  
Distribution Of Fish ◽  
Correlative Relationship

The researches were carry out by stationary and mobile hydroacoustic computerized complexes in the floodplain-riverbed complex of the Irtysh River (Western Siberia, Russian Federation). It was established that during the migration period during the spring flood, patterns of distribution of fish in the stream are observe due to the size-taxonomic characteristics of the fish population and the physiological capabilities of the organism of fish. With an increase in the flow velocity characteristic from the near bank part of the river to its midstream, the proportion of cyprinids in the watercourse decreases, and the proportion of fish with body sizes> 15 cm increases. The number of fish smaller at high-speed sections of the river increases with an increase in water temperature, which in turn indicates the increasing physiological capabilities of representatives of Cyprinidae family. Absolute numerical dominance of migratory fish and the largest proportion of cyprinids were observed in the low velocity section of the river, located closer to the shore. The indicator of the proportion of cyprinids have a direct strong correlative relationship with the temperature factor (0.70-0.73, P<0.05).

Mold taper optimization for continuous casting of H-beam blanks

2019 ◽  
Vol 116 (5) ◽  
pp. 505
Author(s):  
Wei Chen ◽  
Gaiyan Yang ◽  
Liguang Zhu ◽  
Gaoxiang Guo ◽  
Jiaqi Wang ◽  
...  
Keyword(s):  
Continuous Casting ◽  
Casting Process ◽  
Air Gap ◽  
Surface Cracks ◽  
Load Step ◽  
Narrow Face ◽  
Continuous Casting Process ◽  
Step Method ◽  
H Beam ◽  
Multiple Load

The objective of this study is to optimize the mold taper for continuous casting of H-beam blanks. A thermo-mechanical coupled mathematical model was established to analyze the heat transfer, solidification, and shrinkage of the strand in the mold based on the multiple load step method. Based on the simulation results of the air gap distribution in the mold, the mold taper was optimized at selected points on the surface of H-beam blank mold by minimizing the air gap thickness and the best taper scheme was proposed. The results show that the original mold tapers are relatively larger and the optimum mold tapers are as follows: (1) taper at the flange surface: 0.81%/m; (2) taper at the narrow face: 0.68%/m; (3) taper at the fillet: −1.44%/m. The optimum mold size obtained from taper optimization was used in the actual continuous casting process and based on the results, it can be concluded that the optimum mold taper scheme proposed in this study reduced the formation of surface cracks in H-beam blanks.

scholarly journals Stable hovering of a jellyfish-like flying machine

2014 ◽  
Vol 11 (92) ◽  
pp. 20130992 ◽  
Author(s):  
Leif Ristroph ◽  
Stephen Childress
Keyword(s):  
High Speed ◽  
Motion Tracking ◽  
The Body ◽  
Flapping Wings ◽  
Wing Size ◽  
Centre Of Mass ◽  
Hovering Flight ◽  
High Speed Video ◽  
Aerodynamic Model ◽  
Aerodynamic Surfaces

Ornithopters, or flapping-wing aircraft, offer an alternative to helicopters in achieving manoeuvrability at small scales, although stabilizing such aerial vehicles remains a key challenge. Here, we present a hovering machine that achieves self-righting flight using flapping wings alone, without relying on additional aerodynamic surfaces and without feedback control. We design, construct and test-fly a prototype that opens and closes four wings, resembling the motions of swimming jellyfish more so than any insect or bird. Measurements of lift show the benefits of wing flexing and the importance of selecting a wing size appropriate to the motor. Furthermore, we use high-speed video and motion tracking to show that the body orientation is stable during ascending, forward and hovering flight modes. Our experimental measurements are used to inform an aerodynamic model of stability that reveals the importance of centre-of-mass location and the coupling of body translation and rotation. These results show the promise of flapping-flight strategies beyond those that directly mimic the wing motions of flying animals.

Experimental Studies of the Behaviour at High Strain Rates of Unfilled and Filled Polypropylenes

2006 ◽  
Vol 3-4 ◽  
pp. 363-368 ◽  
Author(s):  
N. Temimi ◽  
Noelle Billon
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
High Strain ◽  
Experimental Studies ◽  
Young Modulus ◽  
Video Camera ◽  
Image Correlation ◽  
Strain Rates ◽  
High Strain Rates ◽  
Low Velocity

Thermo mechanical behaviour of unfilled and filled polypropylenes are studied in tension from 10-4 to 102 s-1. Complementary low velocity compression and shear tests are also performed. A high-speed video camera (up to 2500 frames/s) combined with image analysis, image correlation and an infra red pyrometer allow measuring 3D-strain fields and temperature during tests. Thus, data can be processed without restrictive assumptions. Beside usual (for polymers) temperature and strain rate sensitivities it is found that plastic deformation in these materials does not obey incompressibility assumption. Voiding damage is evidenced in the polymer matrix by SEM observations that result in volume change and significant decrease in Young modulus for both materials. Moreover, an increase in the temperature of more than 10 °C is observed and is likely to modify the behaviour of each material at high strain rates. Shear and compression measurements demonstrate that yield criteria and constitutive equation depend on loading. It is concluded that apparent yield stress in semi-crystalline polypropylene can be a result of a combination of “non strain rate sensitive” “non-cohesive mechanisms” and “strain rate sensitive” “cohesive mechanisms”. Experimental characterisation on polymers should then be revisited as most of the usual assumptions are invalid and non monotonic tests should be generalized.

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