Structural Optimization of Landing Gears Using STARSTRUC

<div class="htmlview paragraph">The frequent use of large transport aircraft on soft and rough airfields in or near battle zones requires that they be fitted with landing gears having increased capability for ground flotation and shock absorption.</div> <div class="htmlview paragraph">Design and parametric studies of aircraft landing gears show feasible approaches to the problems associated with soft and rough airfields. Landing gear concepts, analytical methods, and design parameters are presented for airplanes of 110,000–750,000 lb gross weight.</div> <div class="htmlview paragraph">Landing gear weights, sizes, and configurations are compared, and their soft and rough field capabilities are evaluated.</div> <div class="htmlview paragraph">Structural and dynamic aspects of rough field operations are discussed for bare soil fields and for fields covered with landing mats.</div>

<div class="htmlview paragraph">The exploration of substantial money-saving areas of suitable usage for ECM (Electrochemical Metallizing) on aircraft components which are not in the purview of the original equipment manufacturer. The focus of the paper is upon the less spectacular maintenance opportunities rather than the much discussed repair of landing gear and engine components, all of which are strictly controlled by manufacturer's specifications because of safety considerations. Non-critical parts only require documented engineering specifications which are controlled by internal corporate engineering management.</div> <div class="htmlview paragraph">Our objective is to present areas of cost savings available to maintenance departments which have frequently been overlooked in the past. The perceived need is for some presentation of examples of applications which can be found in the normal day-to-day operations of aircraft maintenance activities so that similar opportunities may be identified and acted upon.</div> <div class="htmlview paragraph">General categories to be focused upon will be: Instrument Casings - Electrical Connectors - Printed Circuit Board Contacts - Servo-Motor Shaft and Bearing Fits - Hydraulic Seal Surfaces - Electrical Ground Connectors - EMI and RFI Shielding - Various Anodize Patch Procedures - Slip Rings - Commutators - Actuator Cylinders and Bores - Mechanical Components of Ground Support Equipment -Blower Motor Bearing Refits - Pump Repairs - Cooling Fan Motor Shafts and Bearings - Generator End Bells - Pneumatic Valve Stems and Bores - Compressor Shafts - Accessory Drives and Gear Box Assemblies.</div> <div class="htmlview paragraph">In conclusion, although this audience has been exposed to a full range of Technical papers dealing with more technical accomplishments of ECM, we think that a lot of valuable hardware has been neglected and money lost in areas which are less exciting than plating landing gear without hydrogen embrittlement. The excitement we would like to generate with these ideas has more to do with day-to-day money savings year in and year out. Aircraft maintenance is plagued by more red tape than most industries, but in the area of Avionics and small accessory hardware you have a lot more freedom to accomplish your goals without an inspector breathing down your neck at every move. Our industry has been involved in all the discussed repairs with a variety of manufacturers and military overhaul shops, and we are eager to share them with all of you for our mutual benefit.</div>

<div class="htmlview paragraph">A general purpose computer program DADS has been used to study the landing gear response on battle damaged, repaired runways during aircraft landing, taxing and take off. Two types of gears have been modeled. One is a cantilever type gear, the other is an articulated gear. The hydraulic orifice damping, pneumatic air spring, bearing friction forces in the shock strut and the tire-load deflection curve are all included in the models. The output includes the tire-ground reaction force, the shock strut dynamic load and the forces in each members of the gear.</div> <div class="htmlview paragraph">These two gear models are built in a three dimensional space, and they can be used either as a single gear running over a runway repair mat, or combined together to simulate a whole aircraft operating on a rough field.</div> <div class="htmlview paragraph">The study shows the great capability of DADS in the modeling, simulation and analysis of aircraft ground operations. Rather than writing a generic FORTRAN source code, using the DADS is much easier and more flexible for the user to model and study most types of landing gear systems in a much shorter time frame.</div>

<div class="htmlview paragraph">A chemical and physical characterization of particulate emitted in undiluted exhaust of single cylinder direct injection (D.I.) diesel engine was made by an optical technique.</div> <div class="htmlview paragraph">On-line scattering and extinction measurements in the spectral range from 200 to 500nm were carried out in the exhaust ofthe engine operating under steady-state conditions. These measurements provided a useful tool for the comprehension of chemical and physical structure of the particulate. They allowed the evaluation in real time of the size, the concentration and also the optical properties. Preliminary results of size and mass concentration of particulate are presented.</div> <div class="htmlview paragraph">A good agreement was observed comparing the results with those obtained by gravimetric measurements, TEM and X-ray diffraction.</div> <div class="htmlview paragraph"><b>HIGH EFFICENCY OF DIESEL ENGINES</b> and their ability to burn heavy fuels make them ofgreat interest in the transportation field. On the other hand, present exhaust emission levels produced by this type ofengine will not satisfy stringent international regulations on environ- menta protection.</div> <div class="htmlview paragraph">The studies of the chemical and physical structure of diesel particulate in the exhaust of the engine help manufacturers both to optimize the efficiency of the combustion process and give useful information to designers of after-treatment devices.</div> <div class="htmlview paragraph">Historically, most studies on the particulate in the engine exhaust were carried out by electron microscopy and chemical analysis [<span class="xref">1</span>,<span class="xref">2</span>]<span class="xref">*</span>. These conventional techniques are time consuming, not real time, and not useful in transient operating conditions. Because the composition of the particulate materia depends on the collection system the data can be influenced by sampling procedures.</div> <div class="htmlview paragraph">Size distribution measurementtechniques of particulate based on electrical mobility, diffusion and inertial separation were proposed by Dolanetal.[<span class="xref">3</span>]. These techniques are real time but intrusive and can change the size distribution through collisions between particles.</div> <div class="htmlview paragraph">The recent advances in non-intrusive optical diagnostic techniques have made it possible to study on-line the evolution of particulate emitted in the exhaust with good temporal and spatial resolution.</div> <div class="htmlview paragraph">In the last decade, the optical measurements carried out in the exhaust, were made by nephetometry, transmissiometryor opacimetry, generally at a single wavelength in the visible range or in the infrared by photoacoustic and absorption measurements, These measurements are used to determine both the mass of particulate and the amount of dry soot and SOF [<span class="xref">4</span>,<span class="xref">5</span>,<span class="xref">6</span>,<span class="xref">7</span>.]</div> <div class="htmlview paragraph">In particular, simultaneous light scattering and extinction measurements at a single wavelength in the visible have provided a fast method to determine the dimension and concentration of soot particles i n flame [<span class="xref">8</span>].</div> <div class="htmlview paragraph">The purpose of the present study is to demonstrate the feasibility and flexibility of a new optical technique applied in the undiluted exhaustof a D.I. diesel engine. The technique consists of the use of simultaneous spectral measurements of scattering and extinction coefficients from the near ultraviolet to visible. These measurements allow the on-line simultaneous evaluation of the size, concentration and particulate mass as well as estimating the optical properties of the particulate. In particular, optical measurements in the near ultraviolet region are particularly promising because both graphite and large aro- maticmolecules exhibit absorption bands between 200 and 350nm [<span class="xref">9</span>,<span class="xref">10</span>].</div>

<div class="htmlview paragraph">This paper presents the experience of an air transport operator with landing gear design and operation. Similar landing gear problems seem to recur with each new model airplane. These problems are explained from an airline viewpoint in hopes of improving design for better maintenance and performance of future landing gears.</div>

<div class="section abstract"><div class="htmlview paragraph">Current transport aircraft are mature systems, thus require increased fidelity at the beginning of the design process to allow further optimization. Furthermore, a desire exists to explore unconventional aircraft configurations at the conceptual level. This has motivated the development of a tool which effectively manages the trade-off between high-fidelity levels, flexibility and short turn-around times. This paper presents a CATIA V5-based parametric aircraft geometry modeler developed by Bombardier Aerospace. The aim of the tool is to provide consistent high-fidelity geometric data early in the conceptual aircraft design process.</div><div class="htmlview paragraph">The intended near-term use of the modeler is two-fold: during the early design phase, the modeler computes geometric data such as areas, volumes, ESDU aircraft parameters, etc. In the competitive analysis domain, the tool provides a high-quality three-dimensional model with manageable effort. In both cases, the engineer is presented with a fully parametric three-dimensional CATIA V5 aircraft model. In the medium-term, use by expert departments is envisioned. </div><div class="htmlview paragraph">Moreover, the geometrical data extracted from CATALIST can be saved into a standard database and fed to various analysis codes to compute aircraft performance characteristics. As aircraft models are in native CATIA V5 format, this fits seamlessly into the established design process at Bombardier Aerospace. Additionally, this approach allows critical analyses to be performed earlier in the conceptual design phase.</div><div class="htmlview paragraph">Aircraft exterior and interior modules are in use today along with systems modules and a basic structural representation. An overview of the key features of the tool is presented along with sample applications. Tool usability and modeling quality have been extensively validated with selected regional aircraft and business jets from Bombardier.</div></div>

<div class="section abstract"><div class="htmlview paragraph">This paper summarizes the outcome of an evaluation by capstone design teams from the Department of Mechanical and Materials Engineering at the University of Nebraska-Lincoln, of the Ecosystem for Design Assessment and Verification. The Ecosystem is a design decision support tool whose main goal is to identify design oversights, defined in terms of deviations from the design process or unfulfilled design requirements, early in the design process, guide designers through the design process, and teach proper design techniques. It is capable of automatically assessing students’ design work against ABET compliant learning outcomes. The Ecosystem offers many additional features found useful by capstone design teams, such as automatic generation of formatted project reports as well as interfaces to tools for team communications (Google Drive, Dropbox or OneDrive) or development (e.g., SolidWorks, CATIA, NX Unigraphics or AutoCAD).</div><div class="htmlview paragraph">The Ecosystem was recently evaluated by a capstone team working on an automated straw flattening machine and again during a following semester by a team designing a dynamometer used for measuring the engine power of a BAJA race car.</div><div class="htmlview paragraph">The paper draws upon the improvements of the Ecosystem software completed during the aforementioned time period, identifies the features the capstone teams found most useful, and compares the design experience (productivity) of the BAJA Dynamometer team to that of the a team not using the Ecosystem, but with the same faculty adviser. Through comparison of two such teams, it was found that the team using the Ecosystem managed to stay on schedule a little better.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Exhaust sound quality is one of the most important factors for attractive motorcycles. It is desirable to quantitatively and objectively examine the exhaust sound quality during the development process.</div><div class="htmlview paragraph">In our previous study, we developed evaluation models that could be applied to various exhaust sounds. However, due to the limitation of the model, it could not be applied to varying conditions, such as from acceleration to steady driving and then to deceleration. In this study, we developed more practical evaluation models that can be applied to various driving conditions.</div><div class="htmlview paragraph">To cover a wide variety of sounds under different driving conditions, we prepared more than 300 sound stimuli and collected subjective evaluation data on those sounds. As the evaluation method, we used a pairwise comparison method to make decision making easy for the participants. However, if the pairwise comparison was simply performed for such sample size, the experiment cannot be done in a realistic experimental scale because the number of evaluation pairs gets very large. To solve this issue, we allocated evaluating pairs among multiple participants and used the Bradley-Terry model for estimation of the subjective quality rate. With these methods, the number of evaluations per participant was reduced to 1/300 of that required with the naive method.</div><div class="htmlview paragraph">We constructed the models based on a multiple regression analysis on the subjective evaluation data with waveform feature values as independent variables. We confirmed that these models accurately predicted the motorcycle developers' subjective impression of the exhaust sound of actual vehicles under a wide range of driving conditions.</div></div>

<div class="section abstract"><div class="htmlview paragraph">As aircraft programs currently ramp up, productivity of assembly processes needs to be improved while keeping quality, reliability and manufacturing cost requirements. Efficiency of the drilling process still remains an issue particularly in the case of CFRP/metal stacks: hot and long metallic chips are difficult to remove and often damage the surface of CFRP holes.</div><div class="htmlview paragraph">Low frequency axial vibration drilling has been proposed to solve this issue. This innovative drilling process allows breaking up the metallic chips in such a way that jamming is avoided.</div><div class="htmlview paragraph">This paper presents a case of CFRP/Ti6Al4V drilling on a CNC machine where productivity must be increased. A comparison is made between the current regular process and the MITIS drilling process. First the analysis and comparison method is presented. The current process is analyzed and its limits are highlighted. Then the vibration process is implemented and its performances are studied. Both processes are compared according to the following criteria: chip morphology, thrust force, power consumption, tool life, cycle time, holes quality and manufacturing costs.</div><div class="htmlview paragraph">Results show that the vibration drilling process is more productive and reliable, while maintaining the quality as well as reducing manufacturing costs. The paper also shows that the vibration drilling allows simplifying cutting tool design and reducing lubrication.</div></div>

<div class="htmlview paragraph">The requirements of the link between different applications in the automotive area have been increasing rapidly during the last years. Especially the reliability of the electric/optical interface device for MOST® (<u>M</u>edia <u>O</u>riented <u>S</u>ystem <u>T</u>ransport) applications, FOT (<u>f</u>iber <u>o</u>ptical <u>t</u>ransceiver), is very important and of concern.</div> <div class="htmlview paragraph">The compliance of the required specification (for electrical or optical parameters in the entire environment) is proven by an unique and innovative procedure for automotive components. For the FOT this means also a specific and dedicated qualification procedure to evaluate the portion of the optical data transfer. Today's qualification procedures for semiconductor devices consider electrical and assembly (package) related parameters. The special optical part of the FOT (LED and photodiode) and the accompanying circuits represent a new class of parameters that have to be qualified. Presently, there is no defined standard to get an answer about the quality and reliability of those parts. Therefore, it is necessary to establish an unique standard procedure to qualify MOST devices.</div> <div class="htmlview paragraph">It is important and very useful to examine the requirements for car environment during the qualification procedure as well as the design and production process and also a parameter that represents the desired function. Otherwise it will end up into fundamental consequences for the following product development process (redesign / time shift).</div> <div class="htmlview paragraph">With the experiences from well known qualification standards and with the view of the special requirements of the FOT, there is the distinctive opportunity to establish a procedure that accommodates the particular technical demands in the application. The high benefit of this procedure is a very precise proposition about the expected product quality and reliability level.</div> <div class="htmlview paragraph">This newly developed method can be used in every area where new technologies or new processes are introduced for the first time.</div>

<div class="section abstract"><div class="htmlview paragraph">In recent years the automotive industry has been using an increasing number of high powered engines with fewer cylinders, with the goal to reduce weight and fuel consumption and hence to achieve lower CO2 emissions. In the following paper, an overview about the currently existing methods and products within the exhaust development is given which follow automotive lightweight trend.</div><div class="htmlview paragraph">Continuous innovations in new materials, structural design and manufacturing process as well as mastering the integration of the components and modules within the system with a thorough understanding and optimization of the system behavior is enabling the reduction of weight in exhaust system.</div><div class="htmlview paragraph">Another possibility to reduce the weight is the use of additional components such as valves. In the following, a discussion about the different types of valves is presented. These valves can be implemented within the exhaust system in order to bring a constraint in the system and consequently additional acoustic damping.</div><div class="htmlview paragraph">Due to engine downsizing, many premium vehicles lost their class-representing sound signature. An active system can be used in order to enhance the sound according to the customer demands. In addition to that, an active system can help reducing muffler volume.</div></div>

<div class="htmlview paragraph">In comparison with current production diesel engines the next generation will need to have better fuel consumption, lower noise and reduced emissions both gaseous and visible.</div> <div class="htmlview paragraph">Research over the last ten years has shown that higher rates of injection, coupled with a sharp end of injection and precise timing control will give considerable benefits.</div> <div class="htmlview paragraph">The Lucas CAV response to this requirement is the development of an electronically controlled unit injector system which provides these characteristics.</div> <div class="htmlview paragraph">This paper describes the operating principles and looks at the main performance parameters, including design considerations for continuous operation at pressures up to 1500 Bar.</div> <div class="htmlview paragraph">As the unit injector is a new concept to many engine manufacturers, Lucas CAV has developed a suite of computer programmes to assist in the design and engine application process in terms of a complete hydraulic simulation, unit injector drive train analysis and cam design.</div>

<div class="section abstract"><div class="htmlview paragraph">Aluminum alloy wheels are being widely used in the automotive industry since the last decade due to its superior styling and performance. Alloy wheel rim is one of the critical components and plays an important role in a frontal crash scenario. The wheel rim failure prediction in safety simulation is essential to ensure robust safety performance. Determining failure characteristics of an alloy wheel poses many difficulties considering its brittle nature, porosity and inhomogeneity in material properties across different regions of wheel rim due to mold design, cooling rate and other process parameters of the low-pressure die casting process.</div><div class="htmlview paragraph">This paper describes the modelling and simulation methodology developed to predict accurate wheel behavior. The methodology addresses two distinct areas of challenges such as alloy wheel rim failure prediction and associated tire blow out.</div><div class="htmlview paragraph">Alloy wheel rim material is characterized considering the inhomogeneity of material properties at different regions such as the rim, spokes and hub. The material model is developed, considering strain rate sensitivity, anisotropy due to the state of loading, ductile normal and shear fracture aspects. Scatter function is developed to simulate material property variations.</div><div class="htmlview paragraph">Radial tire characterization is carried out with detailed modelling of constituents such as rubber, steel beads, body plies and steel belts. Various physical tests and digital correlation studies are carried out at coupon and tire assembly level to represent the stiffness and deformation of the tire accurately. A novel approach was developed using sensors in digital models to detect the alloy wheel rim failure in real-time. This triggers rapid air leakage in the tire to simulate the blowout scenario during the crash event. The methodology has been validated at the subsystem and full vehicle level by carrying out multiple physical tests. This approach can be used for digital development and validation of alloy wheel rim design to ensure robust crash safety performance.</div></div>

<div class="htmlview paragraph">A novel design tool that produces solid model geometry from computer-generated sketches was developed to dramatically increase the speed of component development. An understanding of component part break-up and section shape early in the design process can lead to earlier part design releases. The concept provides for a method to create 3-dimensional (3D) solid models from 2-dimensional (2D) digital image sketches.</div> <div class="htmlview paragraph">The traditional method of creating 3-dimensional surface models from sketches or images involves creation of typical sections and math surfaces by referencing the image only. There is no real use of the sketch within the math environment.</div> <div class="htmlview paragraph">An interior instrument panel and steering wheel is described as an example. The engineer begins with a 2-dimensional concept sketch or digital image. The sketch is scaled first by determining at least three known feature diameters. For example, the diameters of a radio control knob, instrument cluster display, and steering wheel should be known. The steering wheel is framed and an ellipse of the wheel is created. A circle is then generated from the ellipse by using mathematical calculations. A scale factor is determined to properly size the image of the instrument panel to the steering wheel. Steering wheel centers are aligned between the sketch image and another math-based instrument panel of similar size. The sketch image is properly sized and then morphed using computer graphics into an orthographic view from a sketch perspective view.</div> <div class="htmlview paragraph">A future small vehicle instrument panel and steering wheel sketch image was morphed into an orthographic view using a similar instrument panel previously developed math model. The glove box and knee bolster surfaces were found to be not correctly located relative to the other math model. This information provided very early and quick feedback to the designer for correction. These components would have required full redesign if not found in the early stages.</div>

<div class="section abstract"><div class="htmlview paragraph">Recent developments in High-Pressure Thermochemical Recuperation technology in the Technion – Israel institute of Technology, were first to allow engines to work on a hydrogen-rich reformate as a stand-alone fuel by its direct injection (DI) to the combustion chamber.This was achieved by using a Magneti Marelli gasoline direct injector, IHP072, modified to enable the gaseous reformate injection. However, this injector , under the used working conditions, suffered from a low flow cross section, non-reliable closure and a non-optimized jet structure, which had a detrimental effect on engine performance. In order to optimize engine performance, i.e. to achieve higher flow rate, shorter open-close timing and higher backward pressure resistance (in the cylinder), an improved injector is needed. In the present work, a novel DI injector was designed producing over expanded reformate jet.</div><div class="htmlview paragraph">One of the main features of the new injector is an outward-opening valve)POPPET valve) with a relatively high flow cross section.Furthermore, a number of elements have been incorporated in the injector design to allow rapid and convenient calibration of the valve lift, sealing force and the magnetic force. Those in turn, enable optimized injector configuration that is well-suited for different working conditions (such as different in-line pressure or flow rates).</div><div class="htmlview paragraph">In this work, the direct-gaseous-injector design process is reported, and its operation is optimized and investigated.</div></div>