Aluminum Blades Research Articles

$^{10}{\rm B}_{4}{\rm C}$ Multi-Grid as an Alternative to $^{3}{\rm He}$ for Large Area Neutron Detectors

Despite its present shortage, 3He continues to be the most common neutron converter for detectors in neutron scattering science. However, it is obvious that the development of large area neutron detectors based on alternative neutron converters is rapidly becoming a matter of urgency. In the technique presented here, grids each comprising 28 10B4C layers (each 1 μm thick) are used to convert neutrons into ionizing particles which are subsequently detected in proportional gas counters. The total active area of the prototype is 8 cm × 200 cm. To instrument this detector 4.6 m2 of 10B-enriched boron carbide were coated onto aluminium blades using a DC magnetron sputtering machine.

RESPONS GETARAN TORSIONAL POROS MODEL TURBIN ARUS LAUT SUMBU VERTIKAL AKIBAT EKSITASI MOMEN PUNTIR

Shaft Torsional Vibration Response of Vertical Axis Ocean Current Turbine Model Due to Torque Excitation. The current research aimed to study the torsional vibration response of Vertical Axis Ocean Current Turbine due torandomly torque excitation pattern, owing to the variety of ocean current velocity. The turbine model is composed of 3 aluminum blades of NACA 0018 connected to steel shaft. Turbine dimensions are 10 cm of chord, 1.8 cm of chamber and 100 cm of span. The variation of ocean current velocity is 0.5 m/s, 1.0 m/s, 1.5 m/s, 2.0 m/s, 2.5 m/s and 3.0 m/s. The Model has 2 degree of freedom which is described into two 2nd order differential equations. The eigenvalue solution yields the model’s natural frequencies; 201,38 rad/s and 457.91 rad/s. Fourier series is used to define the equation of torsional excitation, whilst the vibration equation is solved using Laplace Transform. According to analysis, there is no resonance occur. That because of the system’s natural frequencies is diverse to the magnitude of excitation frequencies. Model will be statically twisted first before vibrated. The response will be transient first then constantly steady. Furthermore, the bigger torque excitation will cause the bigger angular displacement as well the amplitude.

Experimental Study on Carbide Tool Wear Characteristics Test for High Speed Finish Milling Aluminum Blades

According to the condition of the high speed milling aluminum (al) blades, the wear characteristics of the carbide tool was observed, whose wear characteristics mainly were flank wear, micro-tipping, exfoliation and so on. With the increase of the cutting time, the tool wear became larger according to the increment of the spindle speed. At the condition of the same feed per tooth, applying high speed finish milling for al alloy blades whose cutting efficiency increased remarkably, surface roughness decreased, high speed machining was adopted in real applications to achieve high economical benefits.

Brace technology thematic series: the dynamic derotation brace.

BackgroundThe dynamic derotation brace (DDB) was designed in Greece in 1982, as a modification of the Boston brace. It is a custom-made, underarm spinal orthosis featuring aluminium blades set to produce derotating and anti-rotating effects on the thorax and trunk of patients with scoliosis. It is indicated for the non-operative correction of most curves, barring the very high thoracic ones, (when the apex vertebra is T5 or above). The purpose of this article is to familiarize physicians with the DDB, analyze the rationale behind its design, and present the published results of its application.Description & PrinciplesThe key feature of the DDB is the addition of the aluminium-made derotating blades posteriorly. These function as a force couple, which is added to the side forces exerted by the brace itself. Corrective forces are also directed through pads. One or more of previously proposed pathomechanical models of scoliosis may underline the corrective function of the DDB: it may act directly on the apical intervertebral disc, effecting correction through the Heuter-Volkman principle; the blades may produce an anti-rotatory element against the deforming "spiral composite muscle trunk rotator"; or it may alter the neuro-motor response by constantly providing new somatosensory input to the patient.ResultsBased on measurements of the Cobb and Perdriolle angles, up to 82% of patients remained stable or improved with the use of the DDB. Results have varied, though, depending on the type/location of the deformity. The overall results showed that 35% of the curves improved, 46% remained stable and 18% became worse, as assessed by measuring the Cobb angle. The DDB has also been shown to improve cosmesis (except for right thoracic curves) and leave several aspects of patient quality of life unaffected during use.ConclusionConservative treatment of idiopathic scoliosis using the DDB has shown favorable results. Thoracic curves appear more resistant to both angular and rotatory correction. The published outcome data on the DDB support our belief that the incorporation of aluminium blades to other orthoses would likely improve their efficacy.

Aerodynamic Entropy Generation Rate in a Boundary Layer With High Free Stream Turbulence

Aerodynamic Entropy Generation Rate in a Boundary Layer With High Free Stream Turbulence

Cold pressing of copper single crystals for a large-area doubly focusing monochromator

The design for a large-area doubly focusing neutron monochromator consists of a large number of small square copper single crystals mounted onto thin aluminium blades that both buckle and rotate independently. This avoids the need for large individual alignment mechanisms for each crystal that introduce unacceptably high levels of background. However, it does require that the crystals be oriented such that the diffracting crystallographic planes are parallel to the crystal face. Cold pressing broadens the natural narrow mosaic of the virgin crystal discs to increase the diffracted intensity. This introduces anisotropy into the crystal that determines its orientation in the final monochromator. The alignment procedure used for each crystal before cutting out the square tile in the correct orientation is described. A few crystals are characterized in detail by neutron diffraction at various stages of the operation, revealing the variation in the mosaic width and the angular position of the reciprocal-lattice vector as a function of the azimuthal angle by rotating the crystal about the normal to its face. The twofold symmetry of the mosaic width of the pressed crystal is modulated by the 2π periodicity introduced by the precession of the reciprocal-lattice vector around the crystal face normal. Satisfactorily aligned crystals have a variation in the angular position for diffraction within the allowed tolerance.

An elastic, low-background vertical focusing element for a doubly focusing neutron monochromator

A novel, variable radius of curvature, device for the focusing of neutrons is presented. This elastic element consists of a thin variable thickness, constant width, aluminum blade to which diffracting crystals can be attached. When buckled, the blade assumes a circular focal shape, the radius of which is easily controlled by the relative displacement of supporting pivots. Precision electromechanical and optical measurements show that the slope of the buckled blade conforms to a circular arc to within 0.15° for radii in the range 900 mm< R<10 000 mm. This easily scalable, low mass mechanism is well suited for use in a focusing neutron monochromator, as the parasitic scattering typically associated with traditional lead screw and lever mechanisms is greatly reduced.

Equipment

Hartzell has been selected to provide an improved propeller system for the first new aircraft introduced by Piper since the company's reorganization. The system consists of aluminium blades and hub with a redesigned airfoil to optimize cruise performance and efficiency.

Eddy current turbocharger blade speed detection

A commercially available magnetic reluctance sensor is used to determine the angular velocity of turbocharger impeller blades from outside the aluminum housing. Eddy currents are induced in the aluminum blades by blade motion through the magnetic field projected by an externally mounted Samarium-Cobalt permanent magnet. Experiments show that secondary eddy currents and associated ac magnetic fields generated in the aluminum housing provide the prime excitation for a sensor coil located outside the housing. The coil output voltage spectrum shows a strongly peaked structure with peak locations at multiples of the blade passage frequency in the range 1-10 kHz. The sensor output signal decreases with increasing frequency above 2 kHz because of increasingly effective attenuation by the housing. Test results show that a circuit designed to track the blade signal gives an analog voltage output proportional to the frequency of blade passage over the operating range of the Cummins VT-903 and Detroit 8V-71T turbocharged diesel engines. Suggestions are made for the design of a sensor appropriate for both magnetic reluctance and eddy current sensing applications.

Aerodynamic Performance of the DOE/Sandia 17-m-Diameter Vertical-Axis Wind Turbine

The aerodynamic performance of the DOE/Sandia 17-m-diam Darrieus wind turbine is presented for two rotor configurations: 1) two strutted composite structure blades using a NACA-0012 airfoil section with a 21-in. (0.533-m) chord; and 2) two unstrutted extruded aluminum blades with a 24-in. (0.610-m) chord NACA-0015 section. Significant increases in overall performance were obtained for the extruded blades which represent a currently viable low cost blade construction technique applicable to the Darrieus wind turbine.

Aerodynamic performance of a 5-m diameter Darrieus turbine

A 5-m-diam vertical-axis wind turbine has undergone continued testing since 1976 at the Sandia National Laboratories Wind Turbine Site. The latest tests of this machine have been with extruded aluminum blades of NACA-0015 airfoil cross section. The results of these tests at several turbine rotational speeds are presented and compared with earlier test results. A performance comparison is made with a vortex/lifting line computational code. The performance of the turbine with the extruded blades met all expectations.

Titanium UTTAS Main Rotor Blade

A description of the design philosophy leading to the development of a high performance rotor blade for the Army UTTAS helicopter is presented. The Army mission requirements of 550 fpm rate‐of‐climb at 4000 ft, 95° conditions and a 1.75 g maneuver at 150 knots translate into Figure of Merit and aeroelastic achievements beyond those of existing rotors. The roles played by high blade twist, advanced airfoils, and swept tips in providing a rotor system having an unprecedented Figure of Merit of 0.75 is discussed. The technology needed to successfully use a high twist blade and yet achieve forward flight and maneuvering requirements is embodied in the titanium spar, composite cover blade. It is shown that titanium with a bending strain allowable 2 times that of aluminum and a torsional stiffness 2.5 times that of fiberglass best meets the weight, stiffness and life design requirements. The composite cover provides the durability needed for the Army mission while the high specific strength of titanium exceeds the standards of safety set by Sikorsky aluminum blades.

The twin beam composite rotor blade

The use of advanced fibrous composites offers improvements in helicopter rotors due to improved aerodynamic geometry, improved dynamic tuning, good damage tolerance, and potential low cost. Weight reduction is also a potential advantage, but with an articulated rotor system, coning angle and autorotation considerations limit the potential rotor blade weight saving. The improved rotor performance, however, can provide substantial overall system weight savings for a given mission. The twin beam rotor blade derives its name from the fact that it incorporates two separate unidirectional glass fibre epoxy spar beams to carry centrifugal and bending loads. Each spar beam has its own titanium root end attachment, and the twin beams represent redundant load paths for improved reliability. The aerodynamic surface of the blade consists of ±45° graphite epoxy for torsional stiffness and strength and spanwise glass fibre epoxy for improved bending fatigue capability. The blade was designed to be fabricated in two halves for low cost manufacture. The cover and spar are cured together against a hard tool in an autoclave in order to ensure a sound laminate. Balance weights and low density core are bonded in, and the assembly is then machined to the chord line, thus eliminating the dimensional tolerance buildup. The two halves of the blade are bonded together with splices and erosion protection is added. Fatigue tests of full scale H-53-sized blade sections have verified the structural integrity of the twin beam blade construction and have indicated excellent damage tolerance. As predicted from small specimen testing, the composite blades exhibit twice the fatigue strain capacity of comparable aluminium blades. In addition, crack propagation is considerably slower and critical crack size larger in the composite blade. Although the initial cost of the composite blade is projected to be somewhat higher than that of aluminium blades, the longer fatigue life and projected lower maintenance cost should result in a lower cost of ownership.

Hollow Steel Airscrew‐Blade Production

HOLLOW steel airscrew‐blades which, it is claimed, are stronger, weigh no more, and are less susceptible to impact and abrasion than forged aluminium blades of the same size are being manufactured in quantity from seamless steel tubing by the American Propeller Corporation, a subsidiary of the Aviation Corporation. The conception of using tubing for blade making is logical, but the difficulties of putting it into practice were great and required the development of many new methods and production tools. For the following description and accompanying illustrations, the author is indebted to the Propeller Corporation and to supplemental information contained in an article in Steel written by A. H. Allen, Detroit editor of that journal.