G. Fargione

Rapid determination of the fatigue curve by the thermographic method

Abstract The available methods for the rapid determination of the fatigue limit (Metall. Ital. 27 (1935) 188; Rev. Metall. XVIII (1951) 11) and for the analysis of the dynamic parameters of crack mechanics (ASTM-STP 519, 246; J. Mater. 5 (1970) 4; J. Appl. Mech. 67 (1945) A159; Exp. Mech. 5 (1965) 193; Fatigue Engng Mater. Struct. 1 (1979) 37; J. Basic Eng. Trans. ASME, Ser. D 85 (1963) 528) require the determination of parameters which are highly specialised (KI, J-integral) and often too closely linked to the micro-mechanics of the material, downgrading the engineering aspects of the problem and its design definition. Following their research into the use of the thermographic method to determine the dynamic properties of materials and components commonly used in the industrial sector (hereafter called the Risitano method [Int. J. Fatigue Mater. Struct. Components 22/1 (1999) 65]), the authors now present a procedure for the definition of the whole fatigue curve.

Disassembly planning of mechanical systems for service and recovery: a genetic algorithms based approach

AbstractIn a perspective of improving the behavior of a product in its whole life cycle, the efficient planning of the disassembly processes acquires strategic importance, as it can improve both the product’s use phase, by facilitating service operations (maintenance and repairs), and the end-oflife phase, by favoring the recycling ofmaterials and the reuse of components. The present paper proposes an approach to disassembly process planning that supports the search for the disassembly sequence best suited for both aspects, service of the product and recovery at the end of its useful life, developing two different algorithms. Notwithstanding their different purposes, the two algorithms share the typology of modeling on which they operate, and the logical structure according to which the genetic search procedure is developed. The choice of implementing genetic algorithms was prompted by the intrinsic complexity of the complete mathematical solution to the problem of generating the disassembly sequences, which suggests the use of a non-exhaustive approach. As is shown in the results of a set of simulations, both algorithms may be used not only for the purposes related to disassembly process planning but also as supporting tools during the product design phases. This is especially so for the second algorithm, that deals with the problem of a recovery-oriented disassembly through an all-encompassing approach, combining economical and environmental considerations, and extending the evaluations to the whole life cycle of the product. This formulation gives this algorithm and autonomous decisional capacity on both the disassembly level to be reached, and the definition of the optimum recovery plan (i.e., the best destination for the disassembled components, based on some significant properties of them).

A soft computing approach to fuzzy sky-hook control of semiactive suspension

This paper describes a soft computing approach to control a semiactive sky-hook suspension system. The fuzzy controller has been optimized by means of a genetic algorithm and implemented using a dedicated hardware device. After a preliminary study on a quarter car, a seven degree-of-freedom (7-DOF) model was implemented and used for controller simulation and optimization. The proposed control system takes the vehicle heave into account, improving the opposing requirements of comfort and drivability. The following conditions were optimized: drivability over random test roads, sine-wave holes, and sleeper-plates at different speeds. Fuzzy control makes it possible to change the characteristic parameters of the sky-hook suspension in an optimal way according to the different road conditions. The number of fuzzy controller inputs is kept as small as possible, avoiding the use of expensive sensors that increase the overall cost of the system. The proposed system is also easily applicable to existing commercial suspension systems. In addition to the comfort features, the fuzzy controller allows a reduction in load fluctuation, abnormal behavior and tire consumption.

A soft-computing robotic shift for a hybrid vehicle

In the present paper we present a control system of robotic shift in hybrid vehicles that utilizes fussy logic as well as optimization techniques (genetic algorithms) aimed at improving, with the automatic choice of the shifting, the objective-functions previously chosen (minimum consumption, suitable dynamic performances). Following the working out of a model in Simulink environment, which is suitable for the simulation of the behavior of a hybrid vehicle equipped with different shifts (manual, robotic, robotic fussy-logic) we carried out tests in a virtual lab and compared the results with those obtained with models previously built by others (CRF) that had been validated on real vehicles. The results of the simulations have shown, on the one hand, the validity of the robotic shift relative to the manual shift, and, on the other hand, the effectiveness of the application of soft-computing for the development of the robotic shift relative to a vehicle equipped with a traditional robotic shift, in which the logic of shifting is managed by static maps

A cellular neural networks approach for non-destructive control of mechanical parts

An approach is proposed using cellular neural networks applied image processing, for the detection and characterisation of superficial faults in mechanical parts. There are above all two advantages deriving from an application of the proposed methodologies: the automization of a procedure, that of non-destructive tests (NDT), which is today carried out manually, and the possibility to reduce to a negligible amount the time spent on checking operations at present estimated to be in the order of a number of hours for each separate mechanical part.

Use of neural networks on parallel architecture for the classification of plane figures

The use of neural networks for recognizing and measuring objects is proposed. A review of the state-of-the-art of neural network systems and communicating sequential process formalizing was made, in order to select network type and topology. After a standard image acquisition step, the developed system prototype was implemented on parallel architecture, based on Transputer network following the same distribution of the nodes, that constitute the activation functions typical of all types of neural network. The realization of the prototype was carried out in C++ language,l for its portability to different platforms. Then, the developed algorithm was optimized by the translation into the original OCCAM language. The study constitutes the first effort of a research activity, intending to link recognition and measuring of objects to vectorial imagery, using different image acquisition systems (including those working in the infrared band) and the developed system prototype, with software dedicated to industrial drawing applications.

Study of deformations in objects under stress using digital image analysis

Deformations of a plate under different loading conditions were determined using remote sensing techniques. Imagery of the plate under investigation, acquired with a TV-camera based system, was analyzed, in order to measure electronically the average radiance over the plate through the digital numbers in each pixel. Moving from the knowledge of the radiant energy, it was possible to determine deformations, directly related to radiance, analyzing pixel-by- pixel image variations. Radiometric and geometrical considerations allowed determining deflections of the plate, after introducing a correction factor, to consider the response of the acquisition system. They were found in good accordance with those resulting from the use of traditional methods, and proved the working of the proposed technique.

The Remote Sensing Approach. A Modern Technique To Control Sea Pollution.

In the following pages, some of the most significant activities, developed at the Remote Sensing Group of the University of Catania in Italy over a near 20-year period in the field of remote sensing related applications for environmental control, are reported briefly. The remote sensing approach is proposed as a new modern technique, to control sea pollution, and more in general the marine environment, having proved its effectiveness as a means to integrate, and in a number of applications, to substitute conventional investigation techniques.