1,720,967 research outputs found
On the strength weakening effect of stiffening ribs in the design of machine components
No full textThe bending stress in beams may often be reduced by adding material to the cross section. In some paradoxical cases, however, the bending stress increases by adding material from zones far away, or close to, the neutral axis. Similarly, the bending stress of rectilinear or curved beams may often be reduced by adding ribs to the initial beam section. However, such ribs may sometimes cause a both undesired and unexpected stress increase, although they still produce a beneficial stiffening effect. The aim of this paper is twofold: A) to examine this unexpected result within the context of the paradoxical behaviour of some known beam sections, and especially of a recently noted paradox; b) to provide a preliminary rule of thumb for the mechanical design of ribs sometimes added to the outer surface of an eye, with particular regard to the small end of a connecting rod
Structural Analysis of the Forming Process for Hairpin Windings for Electric Motor Applications: Torsional-Flexural Instability Issues
No full textElectric motor manufacturing technology is
evolving due to automotive transport development. Besides,
environmental issues and the need of CO2 emission reduction
have led to an increasing demand for electric drives efficiency.
Permanent magnet synchronous machines are widely
employed for traction systems and distributed windings
produced by using insert techniques are growing in popularity.
These methods require preformed wires such as the well-known
hairpin shape.
The advantages of hairpins are discussed in the pertinent
literature. In the present paper, the manufacturing process of a
hairpin is investigated by analysing its mechanical behaviour
via Finite Element simulations. In fact, many problems might
occur during the forming of a hairpin, depending on the shape
required.
In particular, this study aims at describing the influence of
the geometry of the wire cross-section on the resulting final
shape of the formed hairpin. Suitable ranges of geometrical and
manufacturing parameters are identified to avoid torsionalflexural
instabilities
A MATLAB script and a methodology for the powertrain design of a fuel cells-battery hybrid electric supercar
Full text linkThe urgency to decarbonize the transportation sector covers all kinds of vehicles, here included highperformance competition vehicles. Among the technologies able to guarantee zero emissions during the use phase, fuel cells (FCs) and energy storage systems (ESS), e.g. batteries, offer a great and still largely underexplored potential for complementary and synergic use in hybrid powertrains. Vehicles based on such technologies are cells-battery hybrid electric vehicles (FCHEV), and a niche of these are electric supercars (FCHES). In this context, the degrees of freedom of hybrid powertrains design and the different requirements of FCs and batteries frame the highly complex task of defining a clear and objective methodology to identify an optimal ratio among FC-battery power sources, whose lack jeopardizes a rigorous decision process as well as a general consensus and leads to the acceptance of sub-optimal solutions. In this study an energy/power-based methodology is developed in MATLAB environment considering the longitudinal vehicle dynamics of a typical high-performance parallel FCHES, using telemetry data from a real racetrack as common target for all the evaluated powertrain candidates and using realistic mass values. Under the constraint of equal performance (i.e., equal lap time), several FC-battery parallel hybrid powertrains are numerically evaluated with varying relative energy, power, weight, and under different regenerative braking levels. The set of obtained results allows to draw an objective rightsizing on the FC-battery power share and on the required energy capacity for a parallel FCHEV, as well as mass, hydrogen consumption, etc. The presented methodology offers a general use workflow applicable to any category of vehicles, supporting the engineering of hybrid FC-battery high-performance propulsion systems. The developed code will be made available upon request under the FAIR (Findable, Accessible, Interoperable, Reusable) guidelines
A Homogenization-Based Technique for a Simplified Numerical Finite Element Approach to Describe the Structural Behaviour of Cylindrical Cells Battery Pack
No full textInvestigation on the Dynamic Behaviour of a Torque Transmission Chain for an Innovative Hybrid Power Unit Architecture
No full textIn this contribution, the mechanical torque transmission between the Electric Motor (EM) and the Internal Combustion Engine (ICE) of a P0 architecture hybrid power unit is analysed. In particular, the system is made up of a brand new, single-cylinder 480cc engine developed on the basis of the Ducati 959 Panigale V90 2-cylinders engine. The thermal engine is assisted by a custom electric motor (30 kW), powered by a Li-Ion battery pack. The Ducati 959 Panigale engine is chosen because of its high power-to-weight ratio, and for taking advantage of its V90 2-cylinders layout. In fact, the proposed hybridization process considers to remove the vertical engine head and to replace it by the electric motor directly engaged to the crankshaft using the original valvetrain transmission chain, thus achieving a very compact package. This solution could be suitable for many V-type engines and it aims to obtain a small hybrid power unit for possible motorcycle/small vehicle applications. The original timing chain object of this study is a silent chain, which is commonly employed as a transmission component in hybrid power units because it can operate at high speeds transmitting high loads and ensuring noise reduction. For this reason, the aim of this study is to assess the possibility of using the original chain to couple the EM and the ICE. This investigation allows the replacing of the minimum number of components during the hybridization process leading to a real plug&go solution. Therefore, the mechanical behaviour of the chain is investigated performing a dynamic analysis of the whole crank mechanism. In particular, the original twin cylinders model considering the original valvetrain system is compared with the single cylinder model engaged with the EM. The dynamic analysis provides the maximum load on the single chain link in both configurations, allowing the evaluation of a relative fatigue safety factor
Development of a Hybrid Power Unit for Formula SAE Application: ICE CFD-1D Optimization and Vehicle Lap Simulation
No full textThe paper reviews the CFD optimization of a motorcycle engine, modified for the development of a hybrid powertrain of a Formula SAE car. In a parallel paper, the choice of the donor engine (Ducati 959 Panigale: 2-cylinder, V90, 955 cc, peak power 150 HP at 10500 rpm, peak torque 102 Nm at 9000 rpm) is thoroughly discussed, along with all the hardware modifications oriented to minimize the new powertrain dimensions, weight and cost, and guarantee full reliability in racing conditions. In the current paper, the attention is focused on two main topics: 1) CFD-1D tuning of the modified Internal Combustion Engine (ICE), in order to comply with the Formula SAE regulations, as well as to maximize the power output; 2) simulation of the vehicle in racing conditions, comparison with a conventional combustion car and a full electric vehicle. The stock engine has been strongly modified, since the head of the vertical cylinder has been replaced by the electric motor, and the intake system of the other cylinder now includes a 20 mm restrictor. Despite these constraints, the tuned ICE is able to deliver more than 70 HP. Finally, the study shows that the hybrid car is not only more efficient (-26% of specific CO2), but also 1.48 s faster on each lap than the corresponding Combustion single seater
Design of an Additive Manufactured Steel Piston for a High Performance Engine: Developing of a Numerical Methodology Based on Topology Optimization Techniques
Full text linkModern high performance engines are usually characterized by high power densities, which lead to high mechanical and thermal loadings acting on engine components. In this scenario, aluminium may not represent the best choice for piston manufacturing and steel may be considered as a valid alternative. In this paper, a methodology involving optimization techniques is presented for the design of an internal combustion engine piston. In particular, a design strategy is preliminary investigated aiming at replacing the standard aluminium piston, usually manufactured by forging or casting, with an alternative one made of steel and manufactured via an Additive Manufacturing process. Three different loading conditions are employed for the topology optimizations set up. Optimization results are then interpreted and the various structural features of the steel piston are designed starting from the density distribution contour plots. Different Finite Element thermo-mechanical models are finally prepared in order to correct and validate the designed geometry
Feasibility Study on MHEV Application for Motorbikes: Components Sizing, Strategy Optimization through Dynamic Programming and Analysis of Possible Benefits
Full text linkReducing CO2 emissions is becoming a particularly important goal for motorcycle manufacturers. A fully electric transition still seems far away, given the difficulties in creating an electric motorcycle with an acceptable range and mass. This opens up opportunities for the application of hybrid powertrains in motorcycles. Managing mass, cost, and volume is a challenging issue for motorcycles; therefore, an MHEV architecture represents an interesting opportunity, as it is a low-complexity and low-cost solution. Firstly, in this work, an adequate sizing of the powertrain components is studied for the maximum reduction in fuel consumption. This is performed by analyzing many different system configurations with different hybridization ratios. A 1D simulation of the motorcycle traveling along the homologation cycle (WMTC) is performed, and the powerunit use strategy is optimized for each configuration using the Dynamic Programming technique. The results are analyzed in order to highlight the impact of kinetic energy recovery and engine load-point shifting on fuel consumption reduction. The results show the applicability of MHEV technology to road motorcycles, thus providing a useful tool to analyze the cost/benefit ratio of this technology. The developed methodology is also suitable for different vehicles once a specific test cycle is known
Recovery of Interlaminar Tensile Stresses in Curved Laminates Subject to Biaxial Flexure: The Case of an Elastically Induced Curvature Purposely Misaligned with the Principal Directions of Initial Curvature
Full text linkInfluence of the crankshaft dynamic phenomena on the fatigue behaviour of a transmission chain in a hybrid power unit
No full textThis paper is part of an activity related to a specific hybridization process for an existing and commercialized motorcycle engine. The electric motor is mechanically connected to the engine using the original valvetrain transmission chain leading to a P0 hybrid architecture. The aim of this work is to analyse the structural behaviour of the chain now used as torque transmission device. Although on one side the maximum torque of the electric motor determines a stress state on the chain below its fatigue limit, on the other side, the dynamic behaviour of the system strongly influences the maximum stress on the chain. In fact, the main source of load on the chain derives from the torsional oscillation of the system. Engines rotational speed irregularity can be easily estimated through common analytical approaches which consider the contribution of combustion and inertial forces on the instantaneous torque produced by the crank mechanism and the overall inertia of the moving parts. However, more detailed lumped-parameters and Multibody dynamic models are here developed in order to estimate the actual instantaneous engine speed taking into account the arising of possible high order vibration phenomena. Specifically, the influence of the torsional vibration behaviour of the internal combustion engine is investigated on the resulting stress on the chain. Finally, the structural chain integrity is assessed by performing a fatigue analysis considering the actual operating conditions
- …
