5,645 research outputs found
On the Deflexion of Anisotropic Structural Composite Aerodynamic Components
This paper presents closed form solutions to the classical beam elasticity differential equation in order to effectively model the displacement of standard aerodynamic geometries used throughout a number of industries. The models assume that the components are constructed from in-plane generally anisotropic (though shown to be quasi-isotropic) composite materials. Exact solutions for the displacement and strains for elliptical and FX66-S-196 and NACA 63-621 aerofoil approximations thin wall composite material shell structures, with and without a stiffening rib (shear-web), are presented for the first time. Each of the models developed is rigorously validated via numerical (Runge-Kutta) solutions of an identical differential equation used to derive the analytical models presented. The resulting calculated displacement and material strain fields are shown to be in excellent agreement with simulations using the ANSYS and CATIA commercial finite element (FE) codes as well as experimental data evident in the literature. One major implication of the theoretical treatment is that these solutions can now be used in design codes to limit the required displacement and strains in similar components used in the aerospace and most notably renewable energy sector
Systemic Innovation in a Distributed Network Paradox or Pinnacle?
Previous research has suggested that there is a dichotomy of organisational practices: companies involved in autonomous or modularised innovations, it is argued, benefit from decentralised approaches where coordination primarily takes place through the marketplace, whereas the benefits of systemic innovation are said to be appropriated best by centralised organisations. However, case studies of subcontractors to the Danish wind turbine industry suggest that the ability to meet heterogeneous demands plays an important role for the success of different forms of organisational practices in relation to innovation. The modularised versus systemic architecture approach therefore appears to be a too sweeping dichotomy for describing what can better be perceived as an array of different practices for balancing innovation contribution with the ability of individual firms to appropriate innovation benefits – and a heterogeneous market perception is a core element in building and sustaining this ability.Organisational Forms, Innovation System, Knowledge Complementarities, Value Appropriation
A topological hierarchy-based approach to layered manufacturing of functionally graded multi-material objects
This paper presents an approach based on topological hierarchy to representation and subsequent fabrication of functionally graded multi-material (FGM) objects by layered manufacturing. The approach represents an FGM object by material control functions and discretisation of slice contours. Based on the topological hierarchy of slice contours, material control functions are associated with contour families of some representative layers across the X-Y plane and along the Z-plane. The material composition at any location is calculated from the control functions, and the slice contours are discretised into sub-regions of constant material composition. The discretisation resolution can be varied to suit display and fabrication requirements. In comparison with pixel- or voxel-based representation schemes, this approach is computationally efficient, requires little memory, and facilitates fabrication of large and complex objects, which can be assemblies of FGM and discrete materials. The proposed approach has been incorporated with a virtual prototyping system to provide a practical and effective tool for processing FGM objects. © 2009.postprin
Progress in materials and structures at Lewis Research Center
The development of power and propulsion system technology is discussed. Specific emphasis is placed on the following: high temperature materials; composite materials; advanced design and life prediction; and nondestructive evaluation. Future areas of research are also discussed
Integrated Optimal Design of a Passive Wind Turbine System: An Experimental Validation
This work presents design and experimentation of a
full passive wind turbine system without active electronic part(power and control). The efficiency of such device can be obtained only if the system design parameters are mutually adapted through an Integrated Optimal Design (IOD) method. This approach based on multiobjective optimization, aims at concurrently optimizing the wind power extraction and the global system losses for a given wind speed profile while reducing the weight of the wind turbine generator. It allows us to obtain the main characteristics (geometric and energetic features) of the optimal Permanent Magnet Synchronous Generator (PMSG) for the passive wind turbine. Finally, experiments on the PMSG prototype built from this work show a good agreement with theoretical predictions. This validates the design approach and confirms the effectiveness of such passive device
Nonlinear structural analysis for fiber-reinforced superalloy turbine blades
A computational capability for predicting the nonlinear thermomechanical structural response of fiber-reinforced superalloy (FRS) turbine blades is described. This capability is embedded in a special purpose computer code (COBSTRAN) developed at the NASA Lewis Research Center. Special features of this computational capability include accounting for: fiber/matrix reaction, nonlinear and anisotropic material behavior, complex stress distribution due to local and global heterogeneity, and residual stresses due to initial fabrication and/or inelastic behavior during subsequent missions. Numerical results are presented from analyses of a hypothetical FRS turbine blade subjected to a fabrication process and subsequent mission cycle. The results demonstrate the capabilities of this computational tool to; predict local stress/strain response and capture trends of local nonlinear and anisotropic material behavior, relate the effects of this local behavior to the global response of a multilayered fiber-composite turbine blade, and trace material history from fabrication through successive missions
An overview of aerospace gas turbine technology of relevance to the development of the automotive gas turbine engine
Technology areas related to gas turbine propulsion systems with potential for application to the automotive gas turbine engine are discussed. Areas included are: system steady-state and transient performance prediction techniques, compressor and turbine design and performance prediction programs and effects of geometry, combustor technology and advanced concepts, and ceramic coatings and materials technology
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