Antonino Risitano

Thermographic methodology for rapid determination of the fatigue limit of materials and mechanical components

Abstract By analysing the temperature of the external surface during the application of cyclic loading, it is possible to evaluate the dynamic behaviour of an element and to determine the fatigue limit. The methodology (Risitano method) does not need any particular testing machine and allows reliable results to be obtained using a very limited number of specimens in a very short time. This methodology also yields information on the energy retained by the specimen and mechanical components. The results of 15 years of research into a new methodology for the determination of the fatigue limit of materials or mechanical components are reported.

Product Design for the Environment : A Life Cycle Approach

FROM SUSTAINABLE DEVELOPMENT TO DESIGN FOR ENVIRONMENT Sustainable Development Industrial Ecology Design in the Context of the Environmental Question Design for Environment Concepts, Tools and Approaches to the Environmental Question: Overview Standards and Regulations Oriented Towards Environmental Quality of Products Summary References PART I - LIFE CYCLE APPROACH LIFE CYCLE APPROACH AND THE PRODUCT-SYSTEM CONCEPT AND MODELING Life Cycle Concept and Theory Life Cycle and the Product-System Concept Product-System and Environmental Impact Life Cycle Modeling Product Life Cycle: Reference Model Summary References LIFE CYCLE DESIGN AND MANAGEMENT Life Cycle Approach in Product Design Life Cycle Design Oriented toward Environmental Performance of Products Life Cycle Management Summary References LIFE CYCLE ASSESSMENT Environmental Analysis and Evaluation of the Life Cycle Premises, Properties and Framework of Life Cycle Assessment Fields of Application and Limitations of Life Cycle Assessment Overview of Practical Approaches and Tools for Life Cycle Assessment Summary References LIFE CYCLE COST ANALYSIS Cost Analysis and the Life Cycle Approach Product Life Cycle Cost Analysis Evolution of Models for Product Life Cycle Cost Analysis Reference Standards and Codes of Practice Summary References INTEGRATED ECONOMIC-ENVIRONMENTAL ANALYSIS OF THE LIFE CYCLE Life Cycle Cost Analysis and Environmental Aspects Environmental Costs and Environmental Accounting Integration Between LCCA and LCA Other Approaches to Economic-Environmental Analysis: Eco-Cost Models Summary References PART II - METHODOLOGICAL STATEMENT PRODUCT DESIGN AND DEVELOPMENT PROCESS Product Design and Development Product Design Methodological Evolution in Product Design Summary References INTEGRATION OF ENVIRONMENTAL ASPECTS IN PRODUCT DESIGN Orientation toward Environmental Aspects in the Design Process Environmental Strategies for the Life Cycle Approach Tools and Techniques for Environmental Requirements of the Life Cycle Integration in Product Development: Proposed Framework Toward an International Standard: The ISO/TR 14062 Technical Report Summary References LIFE CYCLE ENVIRONMENTAL STRATEGIES AND CONSIDERATIONS FOR PRODUCT DESIGN Strategies for Improving Resources Exploitation and Determinant Factors Strategies for Extension of Useful Life and Design Considerations Strategies for Recovery at End-of-Life and Design Considerations Product Modularity as a Key Concept for the Application of Environmental Strategies Summary References ENGINEERING METHODS FOR PRODUCT DURATION DESIGN AND EVALUATION Durability of Products and Components Fatigue of Materials Damage Thermography and the Risitano Method Summary References PART III - METHODS, TOOLS, AND CASE STUDIES PRODUCT CONSTRUCTIONAL SYSTEM DEFINITION BASED ON OPTIMAL LIFE CYCLE STRATEGIES Aims and Approach Method and Tools for Analysis and Design Optimal Life Cycle Strategy Evaluation Tool Case Study: System Analysis and Redesign of a Household Refrigerator Final Remarks Summary References ENVIRONMENTAL CHARACTERIZATION OF MATERIALS AND OPTIMAL CHOICE Materials Selection and Environmental Properties Environmental Characterization of Materials and Processes Summary of Selection Method Analysis of Production Feasibility Analysis of Performance Life Cycle Indicators Analysis of Results and Optimal Choice Case Study: Selection of Material for an Automobile Brake Disk Acknowledgements Summary References DESIGN FOR DISASSEMBLY AND DISTRIBUTION OF DISASSEMBLY DEPTH Design for Disassembly and Disassembly Level Distribution of Disassembly Depth Objectives and Approach to the Problem Method Statement Evaluation of Disassembly Depth Efficiency of Ease of Disassembly Distribution Case Study: Electromechanical System Summary References OPTIMAL DISASSEMBLY PLANNING Disassembly Planning Objectives and Approach to the Problem Common Structure of the Proposed Tools Development of the First Tool: Goals of Servicing Development of the Second Tool: Goals of Recovery Simulations and Analysis of Results Summary References PRODUCT RECOVERY CYCLES PLANNING AND COST-BENEFIT ANALYSIS OF RECOVERY Approach to the Recovery Problem Method for Recovery Cycles Planning Calculation Models for Recovery Cycles Planning Case Study: Analysis and Optimization of Heat Exchanger Constructional Systems Cost-Benefit Analysis of Recovery Cycles Acknowledgements Summary References METHODOLOGICAL FRAMEWORK AND ANALYSIS MODELS FOR SIMULATION OF PRODUCT LIFE CYCLE Simulation and the Life Cycle Approach Approach to the Problem and Methodological Framework Product Model and Analysis Tools Definition of Objective Functions Simulation and Analysis of Results Summary References

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.

Effect of stress triaxiality corrected plastic flow on ductile damage evolution in the framework of continuum damage mechanics

Abstract Most of the damage models derived from the theory of Lemaitre have been developed using the hypothesis based on “proportional loading” for the determination of some material parameters. This hypothesis is adopted in such a way that a material coefficient (a scale factor for damage values) can be evaluated from tensile tests on unnotched specimens, considering the triaxiality of the stress state to be that corresponding to perfect uniaxiality, over the entire load history, and so ignoring necking induced variations in the triaxiality. The present paper analyses the response of some continuum damage mechanics models which incorporate a correlation between the triaxiality factor and logarithmic plastic strain. These correlation laws, affecting also the true stress–true strain material curve, were derived from experimental data processed using the Bridgman method. Due to the lack of experimental data specifically related to damage evolution, the aim of the study was to evaluate the sensitivity of these models to the variability of the triaxiality parameter during the deformation history.

Stiffness of Variable Thickness Belleville Springs

The present study reports a theoretical analysis on Belleville springs with linearly variable thickness (radially tapered disk springs). The analysis aimed at the solution of two different problems: the realization of a spring with a zone of null slope in the stiffness curve (i.e. with the possibility of having different values of the deflection at a constant load, particularly useful in some regulation processes), and the definition of a disk spring with an almost constant stress state (with the stress linearly variable from the neutral axis to the upper and lower surfaces). Based on the hypothesis of Almen-Laszlo and Curti-Orlando-Podda, the theoretical analysis give the values of the stiffness curve and the stresses as a function of the geometrical parameters and allowed both problems to be resolved, clearly with different values of the geometric parameters. In order to compare the stresses obtained for large deflections, the authors constructed a numerical model which validated the theoretical analysis.

Determination of Fatigue Limit by Mono-Axial Tensile Specimens Using Thermal Analysis

In this work is indicated how it could be possible to evaluate the limit stress of the thermo-elastic phase of deformation by thermo-analysing the surface of the specimen during a static traction test. Adding the temperature curve measured on a small area of the surface (the hottest) to the classic stress-strain curve, it is possible to evaluate a limit temperature T0 coincident with the beginning of the non linear trend of the curve. The corresponding stress value is coincident with the fatigue limit of the analyzed component. As an example, the results of traction tests performed on two notched specimens, where the change of linearity in the temperature curve during static traction test was evident, are reported.

Determination of the fatigue limit of an austempered ductile iron using thermal infrared imagry

Previous work by the authors showed that the endurance limit of specimens, or mechanical components, can be predicted using thermal infrared imagery. The new technique enables the determination of the fatigue strength limit in a comparatively short period of time (few thousands cycles), and using very few specimens (theoretically only 1). The present work applies this technique to rotating-bending test specimens of austempered ductile iron, an alloy whose fatigue limit is, due to the high scatter dispersion of the data points and the long testing period required, generally difficult to determine by the traditional technique. This material exhibited higher fatigue strength than the familiar nodular cast iron. This was confirmed by the results derived from the traditional Wohler test and the new technique, and supported by the data gathered from literature.

The choice of thermal analysis to evaluate the monoaxial fatigue strength on materials and mechanical components

A historical review was carried out, in order to point out the phases leading to investigate the fatigue resistance of materials and mechanical components, using quick and direct methodologies. Starting from researches performed in the early 1980s, the progresses in the research conducted by the Catania group and other investigators, significantly contributing to the increasing interest in the thermographic analysis of the fatigue phenomenon and, more specifically, to the experimental evaluation of the energy release under fatigue loading, were described.

Proposta di utilizzo di metodologie termografiche per il controllo di qualità di componenti meccanici

In base all’esperienza maturata in anni di sperimentazione sull’analisi delle caratteristiche meccaniche dei materiali mediante indagine termografica, nel presente lavoro e proposta una procedura per il controllo di qualita di componenti meccanici in linea di produzione, che e gia stata argomento di brevetto. Lo sviluppo di questo lavoro si colloca nell’ambito del progetto FIRB “Sistemi di produzione intelligenti, flessibili e riconfigurabili”. L’attivita svolta dal DIIM riguarda il controllo avanzato dell’affidabilita di componenti meccanici per l’industria automobilistica. Viene proposta, quindi, la realizzazione di una cella di controllo in linea di produzione capace di valutare la presenza di eventuali componenti difettosi attraverso l’analisi termica degli stessi, sollecitati secondo un modello predefinito. L’attivita, svolta in questa prima fase in laboratorio, e facilmente trasferibile in linea di produzione, considerando la possibilita di realizzare celle di prova in ambiente controllato, con condizioni praticamente identiche a quelle di laboratorio, eliminando gli effetti di disturbo che possono influenzare la risposta dell’indagine termografica in ambiente non strutturato.

Bending of a pretwisted bar by terminal transverse load

Abstract The problem of bending of a pretwisted bar, cantilevered and loaded by transverse forces at the end, is dealt within the framework of the linear three-dimensional theory of elasticity. The stress components are assumed representable as a suitable series in the pretwist parameter k , whose coefficients can be determined by the solution of plane problems. This is possible if a suitable dependence on the axial coordinate is assigned. The boundary value problems which characterize the coefficients up to the second power are explicitly determined, and the solutions are calculated for an elliptical section. In this way we determine the approximate solution up to terms of order k 2 , to account for a moderate rate of pretwist. From the results of the mathematical analysis, some indications can be deduced regarding the effect of pretwist and a comparison can be made with the classical case of a straight bar.