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

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

VHCF Response of H13 Steels Produced with Different Manufacturing Processes

Experimental results have recently shown that failures at stress amplitude below the conventional fatigue limit and at Very High Cycle Fatigue (VHCF) are possible. In case of high-strength steels, VHCF failures generally originate from defects/inclusions present within the material and, consequently, the defect population properties (size and quantity) significantly affect the VHCF response of high-strength steels. Different refinement processes are commonly adopted in order to improve steel cleanliness: among the other, the ElectroSlag Remelting (ESR) process allows to obtain very clean high-strength steels, thus possibly inducing a significant enhancement of the VHCF response. The present paper aims at investigating the actual effect of the ESR process on the VHCF behavior of an AISI H13 steel. Fully reversed ultrasonic tension-compression tests are carried out on hourglass specimens manufactured with and without the ESR process. The estimated P-S-N curves highlight the positive effects of the ESR process on the VHCF response of the investigated H13 steel

Modal dynamic analysis of a synchronizer mechanism: A numerical study

The present paper shows the modal dynamic behaviour of a single cone synchronizer mechanism. A 3D finite element model is proposed to calculate the natural frequency of the system. By using an efficient method, the natural frequencies of every single component as well as the full system are extracted under different boundary conditions. The natural frequencies of the system in neutral and engaged conditions are extracted and the effective modes are identified. The finite element model is extended to evaluate transient response of the synchronizer mechanism. The effect of different boundary conditions on the modal response is presented. The results show that changing the actuator position can have a significant effect on the dynamic responses of the system. This methodology can be implemented to examine the transient behaviour of other shifting mechanisms

VHCF response of heat-treated SLM Ti6Al4V Gaussian specimens with large loaded volume

Abstract Among the materials used for the production of components through Additive Manufacturing (AM) processes, the Selective-Laser-Melting (SLM) Ti6Al4V alloy is widely employed in aerospace applications for its high specific strength and in biomedical applications for its good biocompatibility. Actual structural applications are generally limited to static loading conditions where the large defects originating during the SLM process do not play a significant role for the static failure. On the contrary, the same defects strongly affect the fatigue response of the parts since they act as crack initiation sites that rapidly lead to fatigue failure. In the literature, a lot of research has been carried out to investigate the quasi-static and the High-Cycle Fatigue properties of the SLM Ti6Al4V alloy but there are still few studies on its Very-High-Cycle Fatigue (VHCF) response. In the paper, the VHCF response of Ti6Al4V specimens, which are vertically orientated during the SLM building and then subjected to a conventional heat treatment (2 hours heating in vacuum at 850°C), is experimentally assessed. Ultrasonic VHCF tests are carried out on Gaussian specimens with a large risk-volume (2300 mm3). Fracture surfaces are investigated for revealing the defect originating the fatigue failure. The Stress Intensity Factor Threshold associated to the experimental failures is finally estimated

Working length transfer in the endodontic clinical practice: A comparative study

8The present paper evaluated the accuracy of two different methods for transferring working length (WL) between manual endodontic instruments and nickel–titanium (NiTi) shaping files. Thirty root canals of extracted permanent teeth were used. Root canals were divided according to canal length (CL) and canal curvature (CC). The reference cusp and the root end were flattened to provide reproducible and accurate measurements. During shaping, the WL measurements were obtained with manual k-files (KF) and transferred to WaveOne (W1) NiTi reciprocating files using the traditional method with the endodontic ruler (method I) and an alternative clinical procedure based on the comparison of the instruments side by side from tip to shank (method II). For each file and each tested method, two measures were taken by two examiners using Rhino (ver. 4.0, McNeel, Seattle, WA, USA) software for a total of 360 (30 × 3 × 2 × 2) measures. Analysis of variance was performed by taking the difference in length (Delta WL, DWL) between files used for the same canal. The difference between methods I and II for WL transfer was found to be statistically significant (df = 1; F = 71.52; p < 0.001). The DWL absolute values obtained with method II were found to be closer to 0 mm (i.e., same length as corresponding KF) than those obtained with method I. Both CL (df = 2; F = 1.27; p = 0.300) and CC (df = 1; F = 2.22; p = 0.149) did not significantly influence WL measurements. With respect to WL transfer, method II seemed to better preserve the correct WL transfer between instruments during the clinical endodontic procedures.openopenMario Alovisi; Mario Dioguardi; Massimo Carossa; Giuseppe Troiano; Maria Chiara Domini; Davide Salvatore Paolino; Giorgio Chiandussi; Elio BeruttiAlovisi, Mario; Dioguardi, Mario; Carossa, Massimo; Troiano, Giuseppe; Chiara Domini, Maria; Paolino, DAVIDE SALVATORE; Chiandussi, Giorgio; Berutti, Eli

Comparison between dog-bone and Gaussian specimens for size effect evaluation in gigacycle fatigue

Gigacycle fatigue properties of materials are strongly affected by the specimen risk volume (volume of material subjected to a stress amplitude larger than the 90% of the maximum stress). Gigacycle fatigue tests, performed with ultrasonic fatigue testing machines, are commonly carried out by using hourglass shaped specimens with a small risk volume. The adoption of traditional dog-bone specimens allows for increasing the risk volume, even if the increment is quite limited. In order to obtain larger risk volumes, a new specimen shape is proposed (Gaussian specimen). The dog-bone and the Gaussian specimens are compared through Finite Element Analyses and the numerical results are validated experimentally by means of strain gages measurements. The range of applicability of the two different specimens in terms of available risk volume and stress concentration effects due to the cross section variation is determined

VHCF response of AISI H13 steel: assessment of size effects through Gaussian specimens

The paper aims at assessing the influence of the Size-Effect (SE) parameter on the VHCF response of the AISI H13 steel. Ultrasonic tests were performed on Gaussian and hourglass specimens characterized by different risk-volumes (volume of material subjected to an almost uniform stress amplitude). Experimental results showed that a significant difference exists between the VHCF strengths of the investigated material obtained by using specimens with different risk-volumes