1,721,011 research outputs found
Trifilar pendulum: Non-small oscillations and calibration
No full text• Motivation • Trifilar pendulum linear model • Trifilar pendulum non-linear model • Period estimation in large oscillations • Numerical validation • Moment of inertia measurement with large oscillations • Experimental tests
Concurrent topological optimization of two bodies sharing design space: problem formulation and numerical solution
Full text linkTopology optimization is a widely used technique for deriving efficient structural layouts for components in many engineering fields. The optimization process deals with the definition of the optimal material distribution of single components subjected to specified loads and boundary conditions, in case made of different materials or with embedded regions corresponding to other components or actuators. In this paper, a novel topology optimization problem is proposed. The case of the concurrent topological optimization of two different components sharing a part of the design spaces is considered. The design problem represents a design situation in which more than one component has to be fitted in an enclosed space and each component has its own load carrying function. In the paper, the problem is solved by a numerical technique able to allocate the common part of the design space to each component. Inside the allocated space, the actual material distribution of the component is optimized by a standard topological optimization algorithm. Numerical examples are provided to show the potentialities of the method. A (simplified) practical design problem is also considered
MASS MANAGEMENT OF A HIGH ENERGY-EFFICIENT BATTERY ELECTRIC VEHICLE
No full textThe paper presents a detailed analysis of the mass-induced power demand of an ultra-efficient battery electric vehicle. The vehicle belongs to a special class of lightweight quadricycles, designed for participating to efficiency competitions. The influence of reducing the mass of the entire vehicle and the mass of the wheels on the vehicle energy consumption is assessed. A sensitivity analysis is performed by exploiting a “tank-to-wheel” multi-physics model of the vehicle. The model includes the main vehicle subsystems and the principal sources of power dissipation are modelled. A three-step sensitivity analysis is carried out: firstly, the influence of the mass reduction on the energy saving is analysed for two different race tracks; then, two different driving behaviour on the same track are compared; finally, the potential energy saving due to actual lightweighting interventions performed on the vehicle is computed. In this phase, secondary mass reduction effects (battery downsizing) are included in the simulation. Results are expressed in terms of Energy Reduction Value (ERV), a parameter widely used in the literature to quantify the correlation between mass reduction and energy saving. The vehicle studied in this paper shows an ERV due to vehicle mass reduction ranging from 0.23 to 0.36 kWh/(100 km∙100 kg), while wheel lightweighting leads to an ERV ranging from 1.03 to 1.74 kWh/(100 km∙100 kg)
A study on the stress gradient reconstruction in finite elements problems with application of radial basis function networks
Full text linkThe recovery of the stress gradient in finite elements problems is a widely discussed topic with many applications in the design process. The stress gradient is related to the second derivative (Hessian) of the nodal displacements and numerical techniques are required for its calculation. Particular difficulties are encountered in the reconstruction of the stress gradient in the boundary regions of the domain. This is of particular concern in most applications, especially in mechanical components, where the maximum values of stresses are often located in these regions and the stress gradient has a strong influence on the fatigue life of the component. This paper presents a comparison between some already published, partially modified, recovery techniques and a different approach based on radial basis function networks. The aim of the paper is to compare the performances of the different approaches for a number of element types with particular focus on the boundary regions. Some examples of mechanical interest are considered
A Portable device for measuring the cog: Design, error analysis and calibration
No full textThe paper is devoted to the design, error estimation and calibration of a portable device for the measurement of the centre of gravity of rigid bodies. The device consists in a simple but effective implementation of the knife edge method. The design of the device including safety considerations is fully described. An error estimation approach is employed in the very early stage of the design to assess the required instrumentation accuracy and the manufacturing tolerances. A calibration of the portable device is performed by means of proper calibrated masses. After calibration, the accuracy of the device corresponds to the target accuracy defined in the a-priori error analysis. The design procedure described in the paper shows a straightforward approach for the design of devices for the measurement of the inertia properties. By such a procedure, it is possible to identify the most critical design areas and make the correct choices in the early stage of the design process. Also, a deep understanding of the measuring process can be gained allowing the definition of an effective calibration procedure
A sensitivity interpolation algorithm for the concurrent optimization of bodies sharing a common design space
Full text linkIn this paper the problem of the concurrent topological optimization of two different bodies sharing a region of the design space is dealt with. This design problem focuses on the simultaneous optimization of two bodies (components) where not only the material distribution of each body has to be optimized but also the design space has to be divided among the two bodies. This novel optimization formulation represents a design problem in which more than one component have to be located inside a limited allowable room. Each component has its own function and load carrying requirements. In the paper a novel development solution algorithm is presented. With respect to previously published papers, the new algorithm comprises an interpolation of the density fields which allows a complete independence of the meshes of the two bodies. As the bodies can be meshed with any arbitrary mesh, this new algorithm can be applied to any real geometry. The developed algorithm is used to design a complex three dimensional system, namely a multi-component arm for a tube bending machine
Beams on elastic foundation: A variable reduction approach for nonlinear contact problems
Full text linkBeams on elastic foundations are applied to a vast number of engineering problems. Several elastic foundation models are available, from the simplest Winkler element with one parameter to complex models with more parameters and nonlinear characteristics. Analytical and numerical approaches have been developed in the literature for the solution of this problem, often specialized for a particular application. In this paper, a novel numerical approach that can be applied to any combination of beam and foundation models is presented. The method is based on independent meshes for the beam and for the foundation. The independent discretization of the foundation opens the possibility to model any kind of foundation behaviour, including nonlinearities, discontinuities and space-dependent properties. The two meshes are then connected by a variable reduction approach, formulated by standard finite element procedures. Such an approach allows to refine the discretization of the foundation without affecting the dimension of the solving system, i.e. with a limited effect on the computational time. Additionally, a relevant advantage of the presented method is that, contrary to most approaches described in the literature, gaps between the beam and the foundation can be straightforwardly included by an energy-based formulation. Examples of applications to linear, nonlinear, and foundation with gaps are reported in the paper. This innovative approach not only simplifies the modelling process but also offers significant computational advantages, making it a versatile and efficient tool for a wide range of engineering applications involving beam–foundation interactions
Wires for spring construction: full scale fatigue experimental tests
Full text linkThe paper deals with the experimental assessment of the fatigue life of wires for spring construction. Fatigue testing of full-scale wires is not a well established procedure. The aim of the paper is to demonstrate that the fatigue properties of full-scale wires for spring construction can be assessed with a level of accuracy comparable with tests performed on standard small-scale specimens. For this purpose, a new bench able to perform high frequency tests for the characterization of the wires in the high and very high cycle fatigue regions is designed, built and employed. The failure mechanism of the tested wires is described by an in-depth analysis of the fractured surfaces. By a comparison with available literature data, the difference with respect to similar tests performed on smallscale specimens is highlighted. Performing the tests on the full-scale wires allows the assessment of the effectiveness of the manufacturing process. The effect of the actual surface finishing on the fatigue life of wires can be assessed
Introduzione di un giovane scimpanzé adolescente (Pan troglodytes) all'interno di un gruppo di piccoli allevati a mano
No full textMulti-Disciplinary Optimisation of Road Vehicle Chassis Subsystems
Full text linkTwo vehicle chassis design tasks were solved by decomposition-based multi-disciplinary optimisation (MDO) methods, namely collaborative optimisation (CO) and analytical target cascading (ATC). A passive suspension system was optimised by applying both CO and ATC. Multiple parameters of the spring and damper were selected as design variables. The discomfort, road holding, and total mass of the spring–damper combination were the objective functions. An electric vehicle (EV) powertrain design problem was considered as the second test case. Energy consumption and gradeability were optimised by including the design of the electric motor and the battery pack layout. The standard single-level all-in-one (AiO) multi-objective optimisation method was compared with ATC and CO methods. AiO methods showed some limitations in terms of efficiency and accuracy. ATC proved to be the best choice for the design problems presented in this paper, since it provided solutions with good accuracy in a very efficient way. The proposed investigation on MDO methods can be useful for designers, to choose the proper optimisation approach, while solving complex vehicle design problems
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