Estimation of the Synchronization Time of a Transmission System through Multi Body Dynamic Analysis

The essential component in transmission system is synchronizer. Synchronizer developed to obtain gear changing smoothly. Reducing the transmission time will increase the efficiency of the transmission system and minimize the energy loss during the shifting process. In order to achieve the optimized design, the time estimation for synchronizing process is necessary. In this present study, the multi body dynamic model is proposed to predict the synchronization time. For validation of the results two different synchronizer types, single cone and double cone were used in the test rig machine under different loading conditions. The results of multi body dynamic analysis were compared to experimental and analytical results and show that there is a good agreement between simulation and experimental results. Using the multi body dynamic analysis makes more accurate result to predict the synchronization dynamic behavior, especially synchronization time

Numerical differentiation for local and global tangent operators in computational plasticity

A simple method to automatically update the finite element mesh of the analysis domain is proposed. The method considers the mesh as a fictitious elastic body subjected to prescribed displacements at selected boundary points. The mechanical properties of each mesh element are appropriately selected in order to minimize the deformation and the distortion of the mesh elements. Different selection strategies have been used and compared in their application to simple examples. The method avoids the use of remeshing in the solution of shape optimization problems and reduces the number of remeshing steps in the solution of coupled fluid–structure interaction problems

Uncertainty in fatigue loading: Consequences on statistical evaluation of reliability in service

A design-by-reliability approach is ever more required and accurate design inputs are needed to meet reliability targets while reducing costs. Different models have been proposed in the literature to describe fatigue life variation with respect to the applied stress by assuming the applied stress as a deterministic independent variable and the fatigue life as a dependent random variable. In the paper also the applied stress is considered as a random variable with its own uncertainty and the procedure to valuate the error on the estimation of parameters usually adopted in service reliability assessment of structural components is shown. Exact equations are proposed for some special cases and an illustrative example showing the reliability errors originated by applying the ASTM recommendations is give

Osteointegrazione di impianti ossei in titanio con diverse finiture superficiali

2007/2008Lo scopo del progetto di ricerca è stato quello di valutare, tramite studi in vivo su animale, il comportamento di guarigione del tessuto osseo a contatto con superfici di impianti in titanio bioattive. E’ stata valutata, in particolare, l’osteointegrazione a quattro settimane dall’inserimento di impianti alloplastici trattati con diverse pectine. Il modello utilizzato è stato scelto per un’analisi a breve termine in grado di verificare l’effetto del rivestimento della superficie sulla velocità del processo di guarigione. Lo studio è stato svolto in cieco ed ha previsto l’esecuzione di analisi istologiche e prove biomeccaniche. In particolare, l’istomorfometria è stata utilizzata per quantificare la percentuale di osso neoformato a diretto contatto con l’impianto, mentre l’analisi della microdurezza e la valutazione della forza necessaria alla rimozione dell’impianto stesso sono risultati indicativi della qualità dell’osso neoapposto. Inoltre, il microscopio elettronico a scansione e la microtomografia computerizzata hanno permesso di ottenere immagini delle viti circondate dal tessuto osseo in modo da poter condurre una valutazione qualitativa dell’interfaccia osso/impianto.XXI Cicl

VHCF strength decrement in large H13 steel specimens subjected to ESR process

Failures at very high number of cycles (Very-High-Cycle Fatigue, VHCF) generally originate from inclusions or defects present within the material. VHCF response of materials is therefore strongly affected by the defect population and, in particular, by the characteristic defect size, which statistically increases with the material volume. According to this well-known dependency, Size Effects were found to significantly affect the VHCF strength of high-strength steels. The paper aims at assessing the influence of Size Effects on the VHCF response of a high performance AISI H13 steel subjected to Electro Slag Remelting (ESR) refinement process. Ultrasonic VHCF tests were carried on specimens characterized by different loaded volumes (hourglass and Gaussian specimens). Experimental results showed that Size Effects strongly influences the VHCF response of the investigated high performance steel, even if it is characterized by a high degree of purity and by a population of inclusions with limited size

Effect of defect size on P-S-N curves in Very-High-Cycle Fatigue

It is well-known that internal defects play a key role in the Very-High-Cycle Fatigue (VHCF) response of metallic materials. VHCF failures generally nucleate from internal defects, whose size strongly affects the material strength and life. Therefore, S-N curves in the VHCF regime are defect size dependent and the scatter of fatigue data is significantly influenced by the statistical distribution of the defect size within the material. The present paper proposes an innovative approach for the statistical modeling of Probabilistic-S-N (P-S-N) curves in the VHCF regime. The proposed model considers conditional P-S-N curves that depend on a specific value of the initial defect size. From the statistical distribution of the initial defect size, marginal P-S-N curves are estimated and the effect of the risk-volume on the VHCF response is also modeled. Finally, the paper reports a numerical example that quantitatively illustrates the concepts of conditional and marginal P-S-N curves and that shows the effect of the risk-volume on the VHCF response

A new methodology for thermostructural topology optimization: Analytical definition and validation

In the last few years, the rapid diffusion of components produced through additive manufacturing processes has boosted the research on design methodologies based on topology optimization algorithms. Structural topology optimization is largely employed since it permits to minimize the component weight and maximize its stiffness and, accordingly, optimize its resistance under structural loads. On the other hand, thermal topology optimization has been less investigated, even if in many applications, such as turbine blades, engines, heat exchangers, thermal loads have a crucial impact. Currently, structural and thermal optimizations are mainly considered separately, despite the fact that they are both present and coupled in components in service condition. In the present paper, a novel methodology capable of defining the optimized structure under simultaneous thermomechanical constraints is proposed. The mathematical formulation behind the optimization algorithm is reported. The proposed methodology is finally validated on literature benchmarks and on a real component, confirming that it permits to define the topology, which presents the maximized thermal and mechanical performance

A general model for crack growth from initial defect in Very-High-Cycle Fatigue

It is well-known in the literature that internal defects play a major role in the Very-High-Cycle Fatigue (VHCF) response of metallic materials. Generally, VHCF failures nucleate from internal defects characterized by a limited size. Unexpectedly, it has been found that cracks can grow from the initial defect even if the Stress Intensity Factor (SIF) is quite below the characteristic threshold for crack growth. Even though researchers unanimously accept this singular experimental evidence, they still dispute about its physical justification. Different micromechanical explanations have been proposed in the literature: local grain refinement, carbide decohesion, matrix fragmentation, hydrogen embrittlement, numerous cyclic pressure and formation of persistent slip bands are the most famous proposals. Regardless of the specific micromechanical explanation, it is generally acknowledged that a weakening mechanism occurs around the initial defect, thus permitting crack growth below the SIF threshold. The present paper proposes an innovative approach for the quantitative modeling of the weakening process around the initial defect. The proposed model considers an additional SIF that reduces the SIF threshold of the material. Starting from a very general formulation for the additional SIF, possible scenarios for crack growth from the initial defect are also identified and described. It is theoretically demonstrated that, depending on the scenario, a VHCF limit may also be present and its final formulation recalls the well-known expression previously proposed by Murakami

Cultivo orgánico de frambuesa Valle de UCO Mendoza

Equipo de trabajo: Chiandussi, María Carla; Costella, María Laura; Lascano, María Belén; Panonto, Silvina; Quiroga, IvánDesde la AER La Consulta nos propusimos evaluar la factibilidad y el comportamiento de este cultivo [Frambuesa] en el marco de producción orgánica bajo las condiciones climáticas y de suelo del Valle de Uco. Para esto, instalamos en el campo experimental del INTA La Consulta, desde septiembre de 2019, una parcela compuesta por 5 variedades de frambuesa: 4 remontantes (Autum Bliss, Fruag Mecso, Polka e Himbotop) y 1 no remontante (Schoeneman). El siguiente informe tiene como objetivo compartir la experiencia, resultados y prácticas de manejo aplicadas a dicho cultivo.EEA La ConsultaFil: Chiandussi, María Carla. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria La Consulta; Argentin

Gaussian Specimens for Gigacycle Fatigue Tests: Damping Effects

Experimental tests investigating the gigacycle fatigue properties of materials are commonly performed with ultrasonic testing procedures, which allow for a significant reduction of testing time but induce a significant temperature increment in specimens. In order to evaluate the significance of size effects on the fatigue strength of materials, the Authors recently proposed to adopt Gaussian specimens for gigacycle tests. Fatigue specimens were designed without taking into account the hysteretic damping and its effects both on the stress distribution and on the heat power dissipation. However, in order to evaluate the temperature increment and the feasibility of ultrasonic fatigue tests with Gaussian specimens, the total dissipated heat power as well as the distribution of the dissipated heat power density along the specimen must be taken into account. The present paper proposes an analytical model validated through a finite element analysis, which permits to evaluate the effects of the hysteretic damping on the stress distribution, on the dissipated heat power density distribution and on the total dissipated heat power in Gaussian specimens