•We analysed the influence of flexible component dynamics in random fatigue.•The relation between the Gaussianity or not of loads and outputs was analysed.•The influence of loads stationarity on ...outputs non-Gaussianity was showed.•The activity was faced to simple flexible body characterized by bi-modal behaviour.
Even if in fatigue application it is common to assume stationary and Gaussian excitation, the impact of non-Gaussian and non-stationary loadings on the service life of a mechanical component is known. Non-Gaussian and non-stationary excitations are generally observed in several industrial applications (i.e. automotive, aeronautical, etc.) and for this, the assessment of the effect of such loads results necessary. From this assumption, the activity herein presented starts from experimental results, previously obtained, that analysed the influence of non-Gaussianity (generally evaluated by kurtosis) and of non-stationarity of inputs on the fatigue life of an Y-shaped specimen. In the present paper the finite element model of the sample and its full validation obtained by numerical/experimental comparison is presented. Moreover, due to the relevant effect of the system’s dynamics on the stress/strain response previously observed, a wider assessment of non-Gaussianity and non-stationarity influence on the fatigue life has been numerically analysed together with the influence of the multi modal behaviour of the component by adopting an excitation frequency range that excites two modes of the model.
Abstract
The use of driving-simulator is increasing wide-spreading in the whole automotive sector. The adoption of driving simulator indeed allows evaluating the design choices directly during the ...design stage thought the man-machine interaction, where “man” means the driver while “machine” means the mathematical model of the car traduced to the driver thought a different machine: the driving simulator. In this research activity a questionnaire was developed to evaluate the performances of a driving simulator focusing on two main aspects. The first one regards the ability of the driving simulator to accurately reproduce the driving feelings without inducing motion sickness sensations. The second instead regards the ability of the driver to objectively judge the vehicle performances throughout a set of parameters. All these aspects were firstly numerically investigated implementing different models showing different dynamics characteristics and successively verified by experimental test at the driving simulator. The drivers scores, about both the accuracy of the mathematical model and the driving simulator, were analysed in order to understand if their feelings match the real behaviour imposed to the car.
Abstract
Explicit simulation is an extensively tool used by automotive designer both for car-performance analysis in standard operating condition and both in drive-simulator, whom exploits the ...computational ability of this codes to operate in real-time. The computational capability of these simulation tools however implies a reduced set of information available in simulation results. Regards automotive sector, with a particular focus on suspension system, the confined number of information in structural terms (states of solicitation on components and constraint) can be a strong limitation in their massive use. In this context, the objective of this activity is to propose a calculation method, as simple as accurate, that foresees to characterize the suspension by an implicit multibody model, and then using the information already available in explicit multibody model (wheel motion and external forces at the contact patch) allows estimating whichever force in all points of the suspension. The results obtained with the proposed method were compared with those outcoming from ADAMS/Car supplying in all cases, good results.
Abstract
Over the past two decades, government space organizations have provided university-level inexpensive access to space that has prompted the design of miniaturized versions satellites for ...research scope: the ”CubeSats”. If on one hand, the standard specifications of this pico-satellite are widely defined to provide easy access to space for educational and research institutions, on the other hand, the design phases of the mechanical and electronic structures are however a very complex and delicate moment of fundamental importance for the success of the launch. The purpose of this document is to provide an exhaustive and critical picture, derived from a broad and in-depth literary analysis of all the critical phases to be faced in order to structurally verify a CubeSat 1U. Starting from the design phase, passing through the simulation and construction of the nano-satellite up to the effective execution of the experimental tests. The aim is to define a linear and efficient path underlining the possible errors and critical moments of the structural verification of a CubeSat.
The dynamic simulation of satellite components requires the ten inertia parameters (mass, mass center three coordinates and inertia tensor, 3×3 matrix). The aim of the present work is the design and ...the realization of a testing machine able to determine all these parameters for small components (assumed to have a rigid body behavior), with particular attention to space scientific experiments. The authors, by an analysis of the state of the art and by an analytical classical approach, have determined a measuring methodology which doesn't currently find application in industry. A testing machine was designed and realized to implement the abovementioned methodology. Its structural integrity and dynamic behavior were investigated by finite element modeling and analysis (FEA) and multi body modeling and simulation (MBS). The machine functionality and precision were tested by a first test campaign conducted on a simple device.
•We analyzed inertia parameters measure techniques.•We analysed the state of the art.•We developed a new procedure to measure the ten inertia parameters.•We designed and realized the testing machine.•We validate the measure procedure and machine functionality by tests campaign.
Polymeric materials find extensive applications across various engineering sectors. Among these, a particularly critical application for these materials is in the field of roller coasters. The wheels ...are typically made with an aluminum hub and a dense polyurethane coating, which, being in contact with the track, endures dynamic loads at high speeds. Due to the viscoelastic behavior typical of polymeric materials, these loads induce overheating of the coating leading to rapid degradation of the wheel. This results in machine downtime and a significant waste of time and money. In this manuscript, a methodology for finite element thermal-structural analysis has been developed. This method allows for the rapid evaluation of temperatures reached during operational cycles if compared to classical coupled-field thermal-structural analysis. The proposed methodology proves to be useful in selecting the appropriate type of wheels during the design phase requiring short computational time. The study first involved the development of the methodology, followed by validation through a comparison of analysis results with data obtained from experimental tests conducted by the manufacturer.
•Development of a FE method for temperature evaluation of polyurethane coated wheels.•The proposed FE method speeds up temperature calculation compared to standard methods.•The proposed FE method helps to choose the wheel that maximizes the operating life.•The experimental-numerical comparison shows a good agreement of the results.
•We developed a design procedure for Roller Coaster rails.•The concept of Influence Line is extended to that of Influence Surface.•The procedure was validated on an industrial test case.
In this ...paper a procedure for the design of the structures of a generic roller coaster (RC) is described. This activity is part of a partnership that the authors are entertaining with one of the major European amusement park industries. The full procedure, developed on theoretical bases and under simplified hypotheses, aims to make designers able to properly and quickly size the complete structure (for complete structure authors mean rails and support structures). In the present paper the design of the rails is presented. The data, needed by this procedure, are the rail track tridimensional geometry and the time histories of contact forces between vehicles and rails. The procedure has been subsequently verified by applying it to an existing RC in order to test all its capabilities and foresee future development and improvement, aiming to insert it in a consolidated general procedure, ever growing and expanding.
•Multiaxial random experimental fatigue tests realized with a new specimen geometry are presented.•The proposed specimens' modal approach was numerically and experimentally validated.•The ...experimental results data are compared with that came from the proposed BVM method.•Fractography analyses of the tested specimens were performed.
Multiaxial random experimental fatigue tests realized with a new specimen geometry are presented. Setting the circular specimen, it was possible to test ASTM A-105 material with a frequency resonance system. The proposed specimens' modal approach was numerically and experimentally validated. The goal of this work was to demonstrate to be able to define the Wöhler curve of the component made, using forecasts data came from the proposed BVM method. To complete the investigation, fractography analyses of the tested specimens were performed.
Abstract
The health monitoring of mechanical components and systems is a technique known and applied for decades in almost all fields of engineering since it allows a drastic reduction of the risks ...associated with any unexpected failure of components and at the same time allows reducing the plant maintenance and management costs. Several monitoring techniques exists and all of them are based on the acquisition and processing on-field measurements aimed to evaluate possible changes in the behavior of the component. Among these, in recent years a method able to monitor in real-time the fatigue damage or the potential damage of a structure with few information has been developed. In this paper, this method, implemented and tested only numerically, has been implemented in an acquisition board, expressly developed, and its ability to operate in real-time by monitoring the failure of a real component subjected to random vibrations has been tested.
Abstract Commonly used in structural applications since the ’90s, composite materials represent a valid alternative to metallic solutions. An intense research activity accompanied the spread of this ...technology to the point that, nowadays, a large variety of modeling techniques and tools are at the designers’ disposal. Although the literature on this topic is vast, detailed, and thorough, the need for new, faster, and more efficient design tools and methodologies remains. In this context, this work covers the development of an Open-Source computational laminate analysis toolbox, its structure, and its validation. The objective of the research was the creation of a simple and accessible mean for the calculation of laminates’ stresses in complex structural components with a reduced computational cost. To this end, the authors implemented the basics of micro, meso, and micromechanics in a Python-based toolbox and then performed a validation campaign against the results of an FE analysis. The work resulted in an input-generation/output-analysis instrument to be used by designers alongside the FEA.
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