Papers by Giorgio Chiandussi
Applied Sciences
The present paper evaluated the accuracy of two different methods for transferring working length... more The 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 le...
Applied Sciences
The aim of this study was to evaluate the contact pressure distribution of two different nickel-t... more The aim of this study was to evaluate the contact pressure distribution of two different nickel-titanium (NiTi) endodontic rotary instruments against the root canal walls and to virtually predict their centering ability during shaping with finite element analysis (FEA). Resin blocks simulating root canals were used. One was shaped with ProGlider and ProTaper Next (PTN) X1-X2 and one with ScoutRace and BioRace (BR) 1, 2 and 3. Both resin blocks were virtually replicated with computer-aided design (CAD) software. The endodontic instruments ProTaper Next (PTN) X2 and BioRace BR3 were also replicated with CAD. The NiTi instruments and the shaped blocks geometries were discretized and exported for FEA. The instrument rotation in the root canals was simulated. The finite element simulation was performed by applying an insertion and extraction force of 2.5 N with a constant rotational speed (300 rpm). To highlight possible differences between pressure distributions against the root canal p...
Fatigue & Fracture of Engineering Materials & Structures
Applied Sciences
It is well-known that many manufacturing parameters affect the quasi-static and the fatigue respo... more It is well-known that many manufacturing parameters affect the quasi-static and the fatigue response of additive manufacturing (AM) parts. In particular, due to the layer-by-layer production, the load orientation, with respect to the building direction, plays a fundamental role for the fatigue response. This paper investigates the fatigue response up to 109 cycles (very high cycle fatigue (VHCF)) of selective laser melting (SLM) AlSi10Mg specimens built in a vertical direction. Ultrasonic tension-compression tests (stress ratio of –1) are carried out on as-built Gaussian specimens with a large loaded volume (2300 mm3). Fracture surfaces are investigated with the scanning electron microscope to analyze the defects originating the VHCF failure. Probabilistic S-N curves are estimated and analyzed. Experimental results confirm that the defect size controls the VHCF response, thus highlighting the importance of testing large risk volumes for a reliable assessment of VHCF behavior. The av...
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering
The synchronizer mechanism represents the essential component in manual, automatic manual, and du... more The synchronizer mechanism represents the essential component in manual, automatic manual, and dual-clutch transmissions. This paper describes a multibody dynamic model for analysis of a synchronizer mechanism subjected to different operational conditions. The three-dimensional multi-dynamic model is developed to predict the dynamic response of synchronizer, especially for calculation of synchronization time. For the purpose of validation, three different synchronizers (single-cone, double-cone, and triple-cone synchronizers) were used on the test rig machine. For the purpose of synchronizing time estimation, an analytical formulation is proposed. The results of the analytical and multibody dynamic analyses were compared with the experimental data, showing a good agreement. The results of analytical and numerical approaches show that the predicted time of synchronization is more precise than previous works. A sensitivity analysis was performed on the single-cone synchronizer, and th...
Procedia Structural Integrity
During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
Frattura ed Integrità Strutturale
Comparison between dog-bone and Gaussian specimens for size effect evaluation in gigacycle fatigu... more Comparison between dog-bone and Gaussian specimens for size effect evaluation in gigacycle fatigue / Tridello A.; Paolino D.S. ; Chiandussi G.; Rossetto M.
Engineering Computations
Head injuries are one of the main causes of death or permanent invalidity in everyday life. The m... more Head injuries are one of the main causes of death or permanent invalidity in everyday life. The main purpose of the present work is to build and validate a numerical model of human head in order to evaluate pressure and stress distributions in bones and brain tissues due to impact. Geometrical characteristics for the finite element model have been extracted from CT and MRI scanner images, while material mechanical characteristics have been taken from literature. The model is validated by comparing the numerical results and the experimental results obtained by Nahum in 1977. The proposed numerical model is promising even if some quantitative differences with the experimental results can be found due to the fact that all the inner organs are considered as a continuum (without sliding interfaces or fluid elements) and due to the geometrical difference between the head used in the experimental test and the head used as reference to build the numerical model. The protecting action of the ventricles and of several membranes (dura mater, tentorium and falx) has been evaluated taking into account known injury mechanisms.
Procedia Structural Integrity
During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
Procedia Structural Integrity
During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
Key Engineering Materials, Jan 6, 2015
Experimental tests investigating very-high-cycle fatigue (VHCF) properties of materials are commo... more Experimental tests investigating very-high-cycle fatigue (VHCF) properties of materials are commonly performed with ultrasonic testing machines, which allow for a significant reduction of testing time. In order to evaluate the effect of tested material volume (size-effect) on VHCF properties, the Authors recently proposed to adopt Gaussian specimens for VHCF tests. Investigation of size-effect with Gaussian specimen induces large mechanical power dissipation and temperature increment that must be taken into account. The present paper proposes an analytical model, which allows to approximately predict the dissipated mechanical power and the temperature increment in Gaussian specimens. The analytical model is also numerically verified through a Finite Element Analysis.
Key Engineering Materials, 2014
Research activities on gigacycle fatigue properties of materials have recently focused on the inf... more Research activities on gigacycle fatigue properties of materials have recently focused on the influence of specimen size used for ultrasonic fatigue tests. In order to increase the volume of material subjected to the maximum stress (risk volume) a new specimen shape with a Gaussian profile is proposed. An approximation of the Gaussian profile with an arc of circle is presented in the paper, in order to simplify the Gaussian specimen manufacturing process. The effect of the approximation is evaluated analytically and through a finite element analysis.
International Journal of Fatigue, Jun 1, 2005
ABSTRACT The point and line methods proposed by Taylor have been used to predict the fatigue stre... more ABSTRACT The point and line methods proposed by Taylor have been used to predict the fatigue strength of notched specimens with different stress ratios R by using literature experimental results. Predictions have been carried out by taking advantage of several equations describing the material fatigue strength dependence on the mean stress and the results obtained by using the Goodman and the Smith–Watson–Topper (SWT) equations are shown. Predicted and experimental fatigue strengths have been compared showing that the effectiveness of the point and line methods can be increased by introducing equivalent mean and alternating stresses and by introducing the dependence of the El Haddad parameter a0 on the stress ratio R. Also with these corrections, the gap between predicted and experimental fatigue strengths for high R stress ratios still keeps being large. It is shown that the gap between predicted and experimental fatigue strengths for high R stress ratios can be reduced by introducing the experimentally evaluated mechanical properties of the material at different stress ratios R and/or by introducing the SWT fatigue strength approximating equation.
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Papers by Giorgio Chiandussi