numerical evaluation of internal heat generation of roller coaster polyurethane wheels

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sine sweep qualification test for engine components the choice of simulation technique

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The importance of dynamic behaviour of vibrating systems on the response in case of non-Gaussian random excitations

Abstract Dynamic response of vibrating system subjected to non-Gaussian random loads was investigated through a set of numerical simulation on several lumped systems aimed to determine whether and in what form the dynamic behaviour of a vibrating system transfers or masks non-Gaussianity features of the input to the output response. Indeed, in several numerical and experimental activities performed on a Y-shaped specimen it was observed how the system response, both in terms of displacement or stress, changed according to an input variation (stationary and non-stationary Gaussian and non-Gaussian load time histories) and according to a change of the system frequency response function. Moreover, it was observed that even if the system was excited in its frequency range, the response remains unchanged and similar to the input in case of non-stationary and non-Gaussian load, removing preliminarily the possibility to use spectral methods for damage evaluation, going necessarily back to a more "expensive" time-domain analysis. Since the system response characteristics may change significantly according to the input excitation features and to the dynamic system parameters allowing, in some cases, the use of spectral techniques for fatigue damage evaluation also in case of non-Gaussian input loads, the aim of this paper is to understand whether and how the dynamic behaviour of a generic mechanical system transforms the non-Gaussian input excitations into a Gaussian response. To this aim several numerical displacement responses of 1-dof lumped systems characterized by different frequency response functions (resonance frequency position and damping) were analysed and investigated for different stationary and non-stationary Gaussian and non-Gaussian excitations. In such a way, it was possible to a-priori establish under what circumstances the frequency-domain approaches can be adopted to compute the fatigue damage of real mechanical systems

mechanical behaviour of wind turbines operating above design conditions

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The use of spectral method for fatigue life assessment for non-gaussian random loads

Abstract The well-known problem with the fatigue lifetime assessment of non-Gaussian loading signals with the use of spectral method has been presented in the paper. A correction factors that transform the non-Gaussian signal into an equivalent Gaussian signal proposed by Bracessi et al. (2009) has been used for the purpose of lifetime calculations together with Palmgren-Miner Hypothesis. The calculations have been performed for the 10HNAP steel under random non-Gaussian load with four dominating frequencies. The signal has been generated on the test stand SHM250 for random tension-compression tests. The results with zero and non-zero mean stresses have been used to calculate the fatigue life with the frequency domain method based on Dirlik's model and with a time domain method with the use of the rainflow cycle counting algorithm. The obtained calculation results have been compared with experimental results

piezoresistive dynamic simulations of fdm 3d printed embedded strain sensors a new modal approach

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a multibody simulation of a human fall model creation and validation

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Numerical Simulation of an Intramedullary Elastic Nail: Expansion Phase and Load-Bearing Behavior

The Marchetti-Vicenzi's nail is an intramedullary device where six curved nails are kept straight by a closing ring in order to allow their insertion into the medullary canal of a long bone; in a following step, these nails stabilize the fracture due to the ring withdrawal and to the consequent elastic expansion of the nails. Pre-clinical testing of this sort of device is strongly advocated in order to be able to foresee their stability inside the medullary canal and to quantify their stiffening action on a broken bone. In this numerical work, an MB (Multi Body) model of the device has been developed, with the dual purpose of evaluating forces between the bone and the system components during its progressive opening and verifying the behavior of the stabilized bone when it undergoes external loading. Different solutions, for flexible body modeling (discretization with lumped parameters, “flexible body,” “FE Part”), have been analyzed and compared in terms of accuracy of results and required computational resources. Contact parameters have been identified and criteria to simplify geometries and therefore to reduce simulation times have been given. Results have allowed to demonstrate how a moderate lateral force is able to dislocate the fracture and how the final position of the retention nut can be optimized. On the whole, a tool for the pre-clinical testing of elastic intramedullary nails has been given

Single-process 3D-printed structures with vibration durability self-awareness

The recent advances in additive manufacturing technology allow the realization of single-process thermoplastic material extrusion (TME) 3D-printed embedded sensors, leading to the easy and inexpensive production of smart structures. While single-process TME dynamic strain sensors have already been researched, vibration durability self-awareness is more than just an additional 3D printed strain sensor and several questions need to be answered. Is the durability self-aware sensors position structure-specific? Is the fatigue life of the sensory element longer than the base structure? Does the fatigue influence the self-awareness capability? Those and several other questions are theoretically and experimentally addressed in this research. Two different fatigue identification methods are researched (i.e. the peak-response and the frequency-drop methods). It was found that the vibration durability self-aware structure printed in a single process is viable and the frequency-drop based method gives reliable fatigue estimationthe fatigue damage was correctly identified even in the case the sensory element was 3D printed in the fatigue zone and already significantly damaged. This research opens up new capabilities for self-aware TME 3D-printed structures