Saab Automobile AB

About: Saab Automobile AB is a based out in . It is known for research contribution in the topics: Radar & Signal. The organization has 760 authors who have published 890 publications receiving 11811 citations.

Zur Bestimmung der Temperaturverteilung in dünnen Platten mit anliegender Überschallgrenzschicht

Abstract: Bei kompressiblen Grenzschichten sind bekanntlich Geschwindigkeits- und Temperaturfelder wegen der Temperaturabhangigkeit der Stoffwerte voneinander abhangig. Manchmal lassen sich fur das Temperaturprofil einfache Randbedingungen an der Wand angeben: z. B. wenn hier die Temperaturen vorgegeben sind oder der Warmeflus verschwindet. In vielen Fallen gehort aber die Wand, die den einen Rand der Grenzschicht bildet, zu einem festen Korper, dessen Temperaturverteilung einschlieslich Wandtemperatur sich aus den Warmestromen in seinem Inneren bestimmt. Im allgemeinen sind also nicht nur die Grenzschichtgleichungen, sondern auch die Warmeleitungsgleichung im angrenzenden Korper zu losen, vor allem, wenn die Wandtemperatur selbst interessiert. Im. Beharrungszustand hangt die durch Reibungswarme hervorgerufene Eigentemperatur des Korpers (gleich seiner Temperatur bei verschwindendem konvektivem Warmeubergang) nur sehr wenig von dem Druckfall langs des Korpers ab, aber auch nur wenig von der Stromungsform: laminar oder turbulent. Deshalb treten im stationaren Zustand nur dann grosere Unterschiede in der Wandtemperatur auf, wenn die Warmestrahlung bedeutend wird. Anders bei instationaren Zustanden, mit denen wir uns im folgenden in erster Linie befassen wollen. Der Beharrungszustand in der Geschwindigkeitsverteilung tritt in der Grenzschicht schon nach Zeiten ein, die von der gleichen Grosenordnung sind wie die, die ein Gasteilchen braucht, um die Strecke vom Anfangspunkt der Grenzschicht bis zur betrachteten Stelle zuruckzulegen.

Spares provisioning strategy for periodically replaced units within the fleet retirement period

Abstract: Within aviation enterprises, the process of dismantling an aircraft at the end of its life is referred to as parting-out. Obviously, the asset value of the units and materials parted out from the retired airframes can be considerable. The benchmarked best practice within the aviation industry is to dismantle the retired aircraft and use the parted-out spares to support the remaining fleet or to offer them on the surplus market. Part-out-based spares provisioning (PBSP) has been a major focus of attention for aviation companies. The PBSP approach is a complex task that requires a multidisciplinary and integrated decision-making process. In order to control the stock level and fulfil the decision criteria within PBSP, it is necessary to make decisions on the termination, at specific times, of both the parting-out process and the maintenance and repair actions performed on the units. This paper considers repairable units and introduces a computational model to identify the applicable alternatives for repair termination times that will minimize the number of remaining spares at the end of the retirement period, while fulfilling the availability requirement for spares during the PBSP period, at the lowest possible cost. The feasible alternatives are compared with regard to their respective costs, and the most cost-effective solution is selected. The cost model uses estimates of future maintenance requirements, the turn-around times, and the cost of the various maintenance tasks, the future spares consumption, and the estimated salvage of spares from retired aircraft. The output of the model is a set of applicable alternatives which satisfy the availability requirements for spares for the active fleet. The method is illustrated using a case study performed on the Saab-105 training aircraft.

A Spinning Finite Beam Element of General Orientation Analyzed With Rayleigh/Timoshenko/Saint-Venant Theory

Abstract: Linear vibrations are studied for a straight uniform finite beam element of general orientation spinning at a constant angular speed about a fixed axis in the inertial space. The gyroscopic and circulatory matrices and also the geometric stiffness matrix of the beam element are presented. The effect of the centrifugal static axial load on the bending and torsional dynamic stiffnesses is thereby accounted for. The Rayleigh/Timoshenko/Saint-Venant theory is applied, and polynomial shape functions are used in the construction of the deformation fields. Non-zero off-diagonal elements in the gyroscopic and circulatory matrices indicate coupled bending/shearing/torsional/tensional free and forced modes of a generally oriented spinning beam. Two numerical examples demonstrate the use and performance of the beam element.Copyright © 1994 by ASME

Material characterization in partially filled waveguides using inverse scattering and multiple sample orientations

Abstract: We present a method aimed at reducing uncertainties and instabilities when characterizing materials in waveguide setups. The S-parameters for a rectangular waveguide loaded with a rectangular sample block are measured for three different sample orientations, and the corresponding geometries are modeled in a finite element program, taking any material parameters as input. The material parameters of the sample are found by minimizing the squared distance between measured and calculated S-parameters.