Computer analysis of semi-monocoque shell sections

In the preliminary design phase of aircraft design, estimating the production cost accurately is a challenging task. At this stage, many design parameters that affect the overall cost are still undefined. This paper establishes cost-estimation models for civil, commercial aircraft using a parametric cost analysis (PCA) approach. Aircraft are characterised based on their size, ranging from a wide body to executive jets, into four categories. Key design parameters, such as maximum take-off weight, number of passengers, range, wing area, span, fuselage length, to name a few, are likely to be available in the preliminary design stage and significantly impact the aircraft design. These variables either directly or indirectly affect the overall production cost or performance. The PCA approach includes both correlation and multiple linear regression techniques. The empirical models thus developed were able to predict the aircraft cost with an error of less than ±4% for all aircraft categories considered. Two aircraft in each defined category were not part of the PCA models and were used to verify the models. The proposed models provide the ability to estimate the aircraft cost quickly in the early stages of the preliminary design phase and provide the possibility of performing parametric studies involving the key variables to determine the cost sensitivity to the main design parameters.

A decision support system for assessing landfill performance

The finite element method (FEM) is established as one of the most popular and powerful tools in analysis and design of engineering systems. However, the method can only be used at an advanced (or detail) design stage when a designer has developed sufficient confidence in the design scheme. In the early (or conceptual/ preliminary) design phase, the method can not be used directly due to the existence of uncertainties of various types. In this work, a procedure is proposed for the FEM to handle engineering systems in the presence of hybrid uncertainties that are characterized by randomness (or stochastic uncertainty) and fuzziness (or design imprecision). The proposed scheme utilizes the techniques of stochastic and fuzzy FEMs in a unified manner to investigate the effects of both input random and fuzzy uncertainties on the output system response. Interpretations of the generated solution space and guidelines in selection of an appropriate solution, according to specific design requirements, are discussed. Two numerical examples are presented to illustrate the computational aspects of the proposed scheme. The current procedure is expected to enhance the understanding of designers regarding the effects of uncertainties in an evolutionary design process, especially in the conceptual or preliminary design phase.

In preliminary design, the details of a structure are insufficient to warrant the use of numeric tools traditionally used in structural analysis. However, an accurate prediction of the behavior of a structure and its components in the preliminary design phase can have a significant effect on the final design process in reducing the number of alternative solutions, avoiding the costly design revisions, and improving the quality of design. Presently, there are few tools available for preliminary analysis of structures. This study represents an initial effort towards the development of a tool that can be used in the conceptual design stage to qualitatively evaluate the behavior of a structure.This paper describes a prototype system, QStruc, for qualitative structural analysis, which combines first principles in structural engineering and experiential knowledge of structural behavior. The purposes of QStruc are: (1) to generate qualitative models from the schematics of a structure; and (2) to infer the qualitative response of the structure in terms of deflected shape, moments, and reactions. The qualitative analysis strategy employs: (1) a greedy depth-first approach that tries to expand the derived response as much as possible from known parameter values; (2) a causal ordering mechanism, which enables the system to identify the solution path for the qualitative analysis; (3) qualitative calculus, which enables the qualitative evaluation of the physical quantities of the causal model that describes the behavior of the structure; and (4) Quantity Lattice (Simmons, 1986) which enables the system to reason about partial ordering among physical quantities and to reduce some of the ambiguous conclusions caused by the impreciseness of the information. Examples are provided to illustrate the effectiveness and limitations of the prototype system.

This work presents structural optimization studies of aluminum and composite material horizontal tail plane of a helicopter by using MSC. NASTRAN SOL200 optimization capabilities. Structural design process starts from conceptual design phase, and structural layout design is performed by using CATIA. In the preliminary design phase, study focuses on the minimum weight optimization with multiple design variables and similar constraints for both materials. Aerodynamic load calculation is performed using ANSYS and the finite element model of the horizontal tail plane is created by using MSC.PATRAN. According to the characteristics of materials, design variables are chosen. For the aluminum horizontal tail, thickness and flange areas are used as the design variables; and for composite horizontal tail, attention is mainly focused on the ply numbers and ply orientation angles of the laminated composite panels. By considering the manufacturability issues, discrete design variables are used. For three different mesh densities, different initial values of the design variables, and similar design constraints, optimizations are repeated and the results of optimizations are examined and compared with each other. In the optimizations performed, constraints are taken as strength and local buckling constraints. It is shown that the optimization methodology used in this study gives confident results for optimizing structures in the preliminary design phase.

The Maunakea Spectroscopic Explorer project’s preliminary design phase start coincides with planned and unplanned events in the national and international astronomy landscape. As the decade draws to a close, most MSE participants are undergoing national strategic planning for key future astronomical development. There are processes similar to the Decadal Survey on Astronomy and Astrophysics in the US. Much of the Project Office activities since our last 2018 report have been aligned in supporting these strategic plans. A vital activity related to the Maunakea Observatories (MKO), including the Canada France Hawaii Telescope (CFHT) Corporation and Maunakea Spectroscopic Explorer, is to secure future access to the mountain for astronomy as affected by the current protest over the Thirty Meter Telescope. Much of the MKO activities have been centered on ensuring the long-term success of astronomy on the mountain beyond 2033. However, the most significant unplanned activity has been managing progress through the ongoing COVID pandemic and anticipating its effects on the timeline and efficacy of upcoming national strategic planning recommendations for astronomy among other national priorities. This paper provides a status report of MSE as it enters the preliminary design phase, and our plan to progress and manage changes in an evolving national and international astronomy landscape.

The design process of new air- and rotorcraft is commonly separated into three different consecutive phases. In the conceptual design phase, the viability of different designs is investigated with respect to customer requirements and/or the market situation. It usually ends with the identification of a basic aircraft lay-out. In the subsequent preliminary design stage the various disciplines are introduced, thus redefining the design process as a multidisciplinary optimization (MDO) task. The objective of this design stage is to enhance the initial aircraft configuration by establishing an advanced design comprising a loft provided with primary structure. This updated aircraft configuration represents a global optimum solution for the specified requirements which will then be optimized on a local level in the concluding detailed design phase with particular regard to manufacturing aspects. The investigations in the preliminary design phase comprise the generation of numerous similar but still different analytical and finite element (FE) models. Even though computational power is constantly increasing the model generation process is still a time-consuming task. Moreover, it is also a potential source of errors which — in the worst case — may lead to time- and cost-intensive redesign activities during the detailed design. As the preliminary design stage, therefore, is of particular importance during the overall design process the model generation process benefits from parametric models and automated process chains. The presented paper overviews the tools used for the automated generation of FE models developed and used at the Institute of Structures and Design (BT) of the German Aerospace Center (DLR) for the subsequent use in numerical simulations. Furthermore, basic requirements for the effective use of parametrization and automation like a common data format and infrastructure will be introduced. Exemplary models and applications will be presented to illustrate the positive impact on efficiency in aircraft design. Concluding, future development steps and possible applications will be discussed.

The Structured Design Methods such as Quality Function Deployment (QFD) and Pugh’s concept generation and selection methods have been shown in the industry to improve the problem definition and design synthesis for the new products hence resulting in the better product design. The application is however limited in the aerospace industry, because the decisions are mostly based on the intuition, simplified back-of-the-envelope calculations and few hand-drawn sketches instead of any higher-fidelity design data using Computer Aided Design and Engineering (CAD/CAE) tools. This leads to the skepticism about the findings of such design methods and reduces their wider acceptance and application in the aerospace design. The examples showing significant improvements in the product definition solely based on the computationally supported design methods are almost negligible. This paper describes work undertaken to add quantitative analysis to these methods in order to reduce such deficiencies. A comprehensive approach has been applied to integrate the mission analysis with high fidelity CAD, CFD and FEA tools that in return provide high fidelity data to enter in the QFD matrix or Pugh’s Concept generation and selection matrix. MS Excel spreadsheet coupled to high level CAD and CAE tools has integrated several aircraft design disciplines for the preliminary design phase. The objective is to demonstrate that the application of Design Methods results in better problem specification and solution synthesis when the scores and rankings are based on the CAD and the high fidelity multidisciplinary design data from aerodynamics and structures. The integration methodology is also used to illustrate the unification of two distinct design phases in the traditional design process i.e. the conceptual and preliminary design into one Preliminary design phase. It is suggested that with the integration of CAD and CAE tools, one can perform all the activities and tasks in one unified phase with reduced design cycle time as compared with two separate design phases comprising of two separate teams. The Pugh’s Method is applied to generate, analyze and select the design concepts for a Medium Altitude Long Endurance (MALE) UAV utilizing high fidelity information.

International audience

Multidisciplinary Design Optimization of Turbine Disks Based on ANSYS Workbench Platforms

Harmoni is the ELT's first light visible and near-infrared integral field spectrograph. It will provide four different spatial scales, ranging from coarse spaxels of 60 × 30 mas best suited for seeing limited observations, to 4 mas spaxels that Nyquist sample the diffraction limited point spread function of the ELT at near-infrared wavelengths. Each spaxel scale may be combined with eleven spectral settings, that provide a range of spectral resolving powers from R 3500 to R 20000 and instantaneous wavelength coverage spanning the 0.47 - 2.45 μm wavelength range of the instrument. The consortium consists of several institutes in Europe under leadership of Oxford University. Harmoni is starting its Final Design Phase after a Preliminary Design Phase in November, 2017. The CRAL has the responsibility of the Integral Field Unit design linking the Preoptics to the 4 Spectrographs. It is composed of a field splitter associated with a relay system and an image slicer that create from a rectangular Field of View a very long (540mm) output slit for each spectrograph. In this paper, the preliminary design and performances of Harmoni Image Slicer will be presented including image quality, pupil distortion and slit geometry. It has been designed by CRAL for Harmoni PDR in November, 2017. Special emphases will be put on straylight analysis and slice diffraction. The optimisation of the manufacturing and slit geometry will also be reported.

The preliminary design phase of any program is the key to its eventual successful development. The more advanced a design, the more this tends to be true. For this reason, the preliminary design phase is particularly important in the design of aerospace systems. Errors in preliminary design tend to be fundamental and tend to cause programs to be abandoned, or to be changed fundamentally, and at great cost later in the design development. In order to facilitate the identification of attractive design regimes, the NASA Ames Research Center initiated a project, supporting the 2/sup nd/ generation reusable launch vehicle (RLV) Program, to develop an advanced suite of conceptual design tools. The tool, called risk oriented program optimization tool (ROPOT) was developed for evaluation of reusable space transportation system (RSTS) conceptual analysis. The ROPOT tool is a modular lego-block approach that is built on risk drivers from the space shuttle. This paper illustrates how this tool was adapted and applied to the decision-making about future space transportation system architectures, including new orbital space plane designs that are to be launched on the new evolved expendable launch vehicles. ROPOT has been further developed to provide the capability to explore crew survival capabilities of the vehicles throughout the mission, and develop insights and concerning the key trades involving performance, cost, crew safety and developmental risk. The tool demonstrated the ability to capture the key trades necessary to make informed decisions concerning alternative vehicle concepts, clearly identify strengths and weaknesses of design alternatives, and identify the most fruitful areas for achieving overall benefits. The results of this effort demonstrate the ability of ROPOT to be easily adapted to evaluate a broad range of vehicle types ranging from fully-reusable advanced concepts of the 2/sup nd/ generation program, to near term expendable vehicles.

The design and the configuration of manufacturing systems, such as assembly lines layouts, are time consuming activities, mainly based on implicit knowledge and no definite rules. This complicated design process is associated with high costs, long lead times and high probability of risks and reworks. Knowledge Based Engineering (KBE) is a technique that can tackle these issues and support the engineers in the early design steps of a manufacturing system with a comprehensive and systematic approach, into the integrated design in a complex system and its related processes. The purpose of this research involve the use of KBE methodology in order to collect and formalize knowledge about the a case study, the design of an assembly line layout system for the cylinder head valve of a car engine. With the formalization of the case study is possible to create an application of configuration that supports the decision making process during the preliminary design phase. The possibility to extend the process to a multi objective optimization is considered. The methodology should be able to help manufacturing equipment providers to shrink design times, evaluating more alternatives and integrating different activities related to the preliminary design phase of a system. This research proposes a practical approach combining the current research state of the art and a real industrial environment for knowledge extraction and application.

Beech 1900D flight test to characterize propeller noise on the fuselage exterior

To reduce development cost and to avoid late design fixes in aircraft design, methods that are fast and economic in estimating the aerodynamic characteristics of complex flight vehicles at the preliminary design stage are desired. This work and thesis focus on the adaptive-fidelity CFD approach, with emphasis on the high end of the CFD tools available today. The core idea of the method is to use computationally cheap modeling in the part of the flight envelope where it is applicable. When the complexity in the flow field increases more details and realism is included in the mathematical model, at a computationally higher cost. A typical case where this would be required could be at the border of the flight envelope, where flow phenomena such as shocks, flow separation, and interacting vortex systems could occur. Since the number of cases needed to resolve the flight envelope could be in the order of ten thousands automation is required. The bottlenecks are the discretization of the fluid volume and evaluation of raw CFD data and post processing of the data. These issues are also discussed in this work. The method has been tested on two real flying aircraft, the X-31 delta-winged aircraft with vector thrust, and the Ranger 2000 Jet trainer, as well as on the SACCON preliminary wing-body UCAV design. The results provide improved understanding of the usefulness of this method as an analysis tool during the preliminary design phase all the way into the flight test diagnostic phase of a new aircraft.