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Advances in simulation of gerotor pumps: An integrated approach
No full textThe paper describes a multi-domain simulation of a gerotor oil pump. Three different analysis tools have been used in synergy to predict the pump flow rate, in both conditions of complete and incomplete filling, and the pressure ripple. The computational fluid dynamics software PumpLinx® has been used for the determination of the discharge coefficients, while a finite element model analysis performed with ANSYS® has allowed the evaluation of the deflection of the pump cover under the action of the delivery pressure. The data calculated with the 3D tools have been utilized as input for a lumped parameter model of the pump developed in LMS Amesim® with customized libraries. The aim of the study is to supply the guidelines for tuning the models using a reduced number of computational fluid dynamics simulations. The results collected in the experimental campaign have demonstrated that a lumped parameter approach can be suitable, if properly calibrated, to predict the pressure oscillations in conditions of defective filling. Moreover, it was found that the cover deflection has a significant importance not only on the leakages, but also on the pressure ripple
Information provision in public transport: Indicators and benchmarking across Europe
No full textThe measurement of the quality of transport services has been the object of an intensive research activity in the last decades. The EU project METPEX aims at advancing the state of the art in this crucial research area through a targeted survey proposed in eight European cities. The dataset is then analyzed to identify latent constructs that can measure the quality of the traveler experience. Several different indicators are proposed to represent detailed aspects related to the perceived quality of transport services. In this paper, we concentrate on those indicators capturing the quality of information provision services in different travel stages: before starting the journey, when passing through stations or stops and while travelling. The results show the added value of separately considering the quality of information provision at different stages of the journey experience, for which different entities could be responsible (e.g. infrastructure managers versus service operators)
Empathy Workshop: When Project Team and Pilot Users Exchange Experiences
No full textEmpathizing with user, has been considered by many design researchers as one of the important factors that help to understand the final user's needs and wishes during the design process. Hence there are still many design projects that do not consider that important basis for design of products and services. In fact, if we look into the psychological process of the ways people communicate and build relationships, we can approve that empathy is fundamental and applying that might seem as an obvious matter in design process. This paper aims to be one another contribution to the field and seeks to emphasize the important role of the empathy in design process. In particular, this paper focus on developing empathy between developers and trial users through a participatory session. We believe this is relevant because we sought to bring the experience of using Internet of Things (IoT)-based devices by trial users in their real homes. It will illustrate the process and results of the participatory session conducted for a pilot project INTrEPID. The whole process of workshop has been built on the fundamental theories about empathy in psychology and the value of its application during the early phases of design process. We suggest to apply the Empathy workshop method when the project team and the final users meet each other, for understanding not only the user's experience and needs, but also the technical team's efforts. It is also proved a good way for fostering the creativity and involving all stakeholders into the design of new services
Re-use in asphalt pavements of fillers from natural stone sawmilling sludge
No full textThe experimental investigation reported in the paper focused on the use in asphalt pavements of fillers originated from natural Stone Sawmilling Sludge (SSS). Performance characteristics of bituminous mastics and mixtures prepared with two types of SSS fillers, differing in mineralogical origin of stones and in stone cutting techniques, were compared with those of reference mastics and mixtures containing standard mineral filler. In the case of mastics, the testing program included the evaluation of their rheological properties at different temperatures and loading conditions. In the case of corresponding mixtures, laboratory characterization was based on the evaluation of their workability, volumetric characteristics, stiffness, and rutting potential. Experimental results indicated that SSS fillers can be conveniently used in asphalt pavements yielding satisfactory levels of performance
Pressure Control in a Low-Pressure Casting Furnace
No full textThe casting of light alloy components is a technology commonly used in aeronautic industry. This operation is possible, for example, using a low-pressure casting system, where it is important to control the temperature but also the maximum value and the time history of the pressure inside the furnace. For this reason it becomes important to study the pressurization circuit. In this paper a theoretical and experimental study of the pressurization circuit of a low-pressure casting furnace is presented, to individuate the temporal behaviour of the pressure inside the furnace. Particular attention has been paid to the experimental characterisation of the proportional valve with current-driven electro-pneumatic pilot. The opening of the principal valve is a function of the current of the pilot-valve. The characteristics, in terms of flow coefficients and response time, have been evaluated as a function of the upstream pressure and of the pilot current. A lumped parameters model has been developed, in which it is possible to vary the following parameters: type of valve and its coefficients, volume and temperature of the furnace, size of connecting pipes and supply pressure. The resistive and capacitive effects have been considered for the tube model but the inductive effect has been neglected. For the furnace only the capacitive effect has been take into account. The influence of the different parameters on the furnace pressure has been evaluated; experimental results obtained from tests on single components have used to find the parameters of the numerical model. The validation of the whole pressurizing furnace circuit model has been made with an experimental set-up properly realised. For every working condition, a good agreement between numerical and experimental time history of the pressure inside the furnace has been obtained. A further model validation has been made by using experimental results obtained by an existing foundry circuit. Also in this case good agreement has been obtained
Incoming windblown sand drift to civil infrastructures: A probabilistic evaluation
No full textThe accurate prediction of windblown sand drift events approaching human infrastructures and activities is fundamental in arid lands. In both scientific literature and technical practice sand drift estimation is carried out in mean terms. Typically, sand drift net direction and intensity are assessed by means of the resultant drift potential. However, windblown sand suffers a number of epistemic and aleatory uncertainties, related to both the wind and the sand fields. The windblown sand drift estimation in probabilistic terms is useful in the infrastructure design perspective and allows to obtain characteristic values of windblown sand transport. In this study windblown sand is considered as an environmental action in analogy to wind action. Several uncertainties involved in the phenomenon are considered: threshold shear velocity and 10-min average wind velocity are assumed as random variables. Monte Carlo approach is adopted within a bootstrapping technique in order to assess sand drift in probabilistic terms. The proposed approach is applied to five sites in the Arabian Peninsula. Directional statistics of the sand drift are given for each site
On Design Optimization of a Composite Impact Attenuator Under Dynamic Axial Crushing
No full textMotorization brings two significant challenges to the modern society. Firstly, road and vehicle safety becomes increasingly important, which has notably heightened legislative requirements by introducing more effective protective systems to the vehicle. Secondly, there is an ever-growing concern in environment and sustainability, which largely push up the lightweight standards to reduce fuel consumption. For these reasons, the automotive industry has devoted a substantial effort to deliver more crashworthy vehicles for addressing these two competing issues simultaneously. Over the past two decades design optimization has been developed as a powerful tool to seek the highest possible crashworthiness and lightest possible structure for various vehicles, therefore becoming an important topic of research. In crashworthiness optimization, direct coupling method may be inefficient since iterative non-linear FEA during optimization usually require huge computational efforts and take the high risk of premature simulation failure prior to a proper convergence. As a result, surrogate models (or metamodels) are more often used as an alternative for formulating the design criteria in terms of an explicit function of design variables in advance of optimization, which has proven an effective and sometimes a unique approach. The idea of surrogate modeling is to construct an approximate function based on a series of sampling evaluations, in which design space is typically sampled using the design of experiment methods. Then, the FEA is performed at these sample points to establish surrogate models with a certain confidence of approximation for crashworthiness optimization. This paper provides the results obtained from an optimization procedure on a composite impact attenuator, under dynamic axial crushing, using two different metamodels, such as Radial Basis Function and Kriging. In particular the sizing optimization for some geometric parameters was solved combining the commercial solver LS-DYNA with the optimizer LSOPT. In order to measure the fitness of results and do a comparison between different surrogates, global error parameters were used, such as root mean squared error, maximum residual error and coefficient of determination