Michele Moretti

Measurement on Rotating Mechanical Component by Thermoelasticity

In this paper a new measurement technique to perform thermoelastic stress analysis on rotating mechanical component is proposed. The idea is to use a particular realization of the Dove prism optical system, optimized to work width infrared radiation, able to give a fixed output image of a rotating surface on where a normal thermoelastic measurement system can be applied. The realization of a first prototype of this optical system is described. First results on a test case are illustrated.

Image Analysis Technique for Material Behavior Evaluation in Civil Structures

The article presents a hybrid monitoring technique for the measurement of the deformation field. The goal is to obtain information about crack propagation in existing structures, for the purpose of monitoring their state of health. The measurement technique is based on the capture and analysis of a digital image set. Special markers were used on the surface of the structures that can be removed without damaging existing structures as the historical masonry. The digital image analysis was done using software specifically designed in Matlab to follow the tracking of the markers and determine the evolution of the deformation state. The method can be used in any type of structure but is particularly suitable when it is necessary not to damage the surface of structures. A series of experiments carried out on masonry walls of the Oliverian Museum (Pesaro, Italy) and Palazzo Silvi (Perugia, Italy) have allowed the validation of the procedure elaborated by comparing the results with those derived from traditional measuring techniques.

Advanced Data Mining Techniques for Power Performance Verification of an On-Shore Wind Farm

The monitoring of wind energy production is fundamental to improve the performances of a wind farm during the operational phase. In order to perform reliable operational analysis, data mining of all available information spreading out from turbine control systems is required. In this work a Supervisory Control and Data Acquisition (SCADA) data analysis was performed on a small wind farm and new post-processing methods are proposed for condition monitoring of the aerogenerators. Indicators are defined to detect the malfunctioning of a wind turbine and to select meaningful data to investigate the causes of the anomalous behaviour of a turbine. The operating state database is used to collect information about the proper power production of a wind turbine, becoming a tool that can be used to verify if the contractual obligations between the original equipment manufacturer and the wind farm operator are met. Results demonstrate that a proper selection of the SCADA data can be very useful to measure the real performances of a wind farm and thus to define optimal repair/replacement and preventive maintenance policies that play a major role in case of energy production.

Thermoelasticity for the Evaluation of Fatigue Behaviour of 6061/AL

In this study, the effect of Friction Stir Welding on a 6061 aluminium alloy reinforced with 20% of alumina particles metal matrix composite was analysed. The sheets were joined by employing a tool rotating speed of 700 RPM and a welding speed of 250 mm/min. The optical and scanning electron microscopy observations performed on the different zones of FSW joints cross section revealed the different structures of the nugget, the thermo‐mechanical affected zone and the heat affected zones thanks to the difference in reinforcing particles dimensions as a consequence of friction process. After FSW the material was aged in a 3.5% NaCl solution for 1, 10 and 90 days. The aim of this work is to apply thermoelastic stress analysis to the study of crack formation and propagation of friction stir welded MMC sheets, during cyclic fatigue tests. Fatigue tests were carried out under the axial total stress‐amplitude control mode with R=omin/omax = 0.1 using a resonant electro‐mechanical testing machine (TESTRONICTM 50 25 KN by RUMUL (SUI)). All the mechanical tests were performed on as‐FSW and aged samples up to failure. The TSA measurement system allowed the crack evolution to be observed in real‐time during fatigue cycles and stress fields to be derived on the specimens from the temperature variation measured.

A New Measurement and Testing Procedure Based on Thermoelasticity for Motorcycle Frame Prototype Development

Motorcycle frames are mechanical components that need to be optimised in terms of performance and costs but with a limited amount of resources compared to, for example, car frames. Fatigue testing of the component is required for qualification and this is typically performed by using rotating drums with steps or servo-controlled hydraulic actuator based test benches. Therefore a fast and simple measurement and testing technique that operates during the fatigue tests will be a very useful tool. In this paper the possibility of analysing these components by measuring the stress levels and stress concentration in critical parts by thermoelasticity is investigated. The development of a multibody model, useful to simulate the typical working conditions of the motorcycle frame, is also described.

Relating Vibration and Thermal Losses Using the Damping Heat Coefficient

Damping of vibrating systems converts the vibrational energy into other forms, such as heat and sound radiation. Heating of the material is often assumed to be one of the biggest drains of energy; however, it is very hard to experimentally identify how much of the damped energy is converted to heat. This manuscript introduces the damping heat coefficient and via high-speed cameras (optical and thermal) identifies that, for the selected material, approximatelly 30% of the damped energy is converted to heat.

Point cloud processing techniques and image analysis comparisons for boat shapes measurements

The design and modelling of a boat involve complex freeform geometric shapes, difficult to measure and survey with traditional metrology methods. Scan data allow creating precise 3D models that can be used by naval designers and engineers to ensure the quality of interior and exterior construction, as well as for simulation and inspection purposes. For this purpose, the paper describes photomodelling technique, a recent and fast image processing and alignment method that leads to the reconstruction of three-dimensional models, starting from the simple acquisition of photographic images. Close to photogrammetry, the result obtained is a 3D point cloud, a set of x,y,z space coordinates, first form of the object surveyed [1]. A point cloud can be identified as a pixel cloud, because of the direct relationship between photomodelling and photography: each pixel of an image corresponds to a point of the cloud, thus preserving the chromatic characteristics of the object surveyed [2]-[6].

Identification of individual features in areal surface topography data by means of template matching and the ring projection transform

Starting from areal surface topography data as provided by current commercial three-dimensional (3D) profilometers and 3D digital microscopes, this work investigates the problem of automatically identifying and extracting functionally relevant, individual features within the acquisition area. Feature identification is achieved by adopting an original template-matching algorithmic procedure, based on applying the ring projection transform in combination with a parametric template. The proposed algorithmic procedure addresses in particular template-matching scenarios where significant variability may be associated with the features to be compared to the reference template. The algorithm is applied to a test case involving the characterization of the surface texture of a superabrasive polishing tool used in hard-disk manufacturing.

Analysis of 7005/Al2O3/10P MMC Sheets Joined by FSW by Thermoelasticity

Friction Stir Welding represents a very attractive technology in reducing residual stresses and distortion in joints compared to conventional fusion welding ones. In particular, FSW of Aluminium based metal matrix composites is less affected by the inconveniences deriving from debonding and segregation of reinforcing particles. In this study, the metal matrix composite under investigation was a 7005 aluminium alloy reinforced with 10% of alumina particles Friction Stir Welded (T6 condition) by employing a threaded tool rotating speed of 600 RPM and a welding speed of 250 mm/min. The optical and scanning electron microscopy observations performed on the different zones of FSW joints cross section revealed the different structures of the nugget, the thermo-mechanical affected zone and the heat affected zones thanks to the difference in reinforcing particles dimensions as a consequence of friction process. Such phenomenon is accompanied with a strong grain refinement due to a dynamic recrystallization acting during the severe plastic deformation to which the material is subjected during the welding process.