P.M. Lonardo

Quantitative Characterisation of Surface Texture

Abstract This paper reviews the different methods used to give a quantitative characterisation of surface texture. The paper contains a review of conventional 2D as well as 3D roughness parameters, with particular emphasis on recent international standards and developments. It presents new texture characterisation methods, such as fractals, wavelets, change trees and others, including for each method a short review, the parameters that the new methods calculate, and applications of the methods to solve surface problems. The paper contains a discussion on the relevance of the different parameters and quantification methods in terms of functional correlations, and it addresses the need for reducing the large number of existing parameters. The review considers the present situation and gives suggestions for future activities.

Progress in 3D Surface Microtopography Characterization

Abstract The recent advancements achieved in 3D analysis of surface micro-topography have raised a great interest of researchers and industrial users for the possibilities of the new techniques, in spite of their major complexity. In this paper the state-of-the-art in measurement methods, reference surfaces, visualisation techniques, definition and use of parameters is reviewed, considering advantages and limits of the 3D characterisation. The need to develop further studies on the functional meaning of parameters is highlighted. Finally, comments on traceability and standardisation are given.

Emerging trends in surface metrology

Abstract Recent advancements and some emerging trends in the methods and instruments used for surface and near surface characterisation are presented, considering the measurement of both topography and physical properties. In particular, surfaces that present difficulties in measurement or require new procedures are considered, with emphasis on measurements approaching the nanometre scale. Examples of new instruments and promising innovations for roughness measurement and surface integrity characterisation are presented. The new needs for tolerancing, traceability and calibration are also addressed.

Effect of Flushing and Electrode Material on Die Sinking EDM

Abstract The most important parameters of EDM are the removal rate, the electrode wear, accuracy and surface texture. In this paper the influence of electrode material, flushing, electrode dimension, depth of cut and planetary motion on EDM performance is discussed. An experimental analysis was carried out on a Cr, Mo, V steel for die casting by using both copper and graphite electrodes. Roughing and finishing operations were considered, by adopting for each condition the parameters commonly recommended in industrial production. The observed results show the importance of electrode material, injection flushing and geometry of cutting on removal rate, electrode wear and surface quality.

Measurement and Topography Characterisation of Surfaces Produced by Selective Laser Sintering

Abstract Selective Laser Sintering (SLS) permits to manufacture physical models, suitable to be used as sand moulds in the casting processes. SLS presents some technological limits as regards the dimensional precision and surface roughness, which require an accurate assessment. Unfortunately contact methods are not able to carry out these measurements. This paper investigates the possibility of using a new non-contact instrument based on conoscopic holography to measure both microgeometry and macrogeometry of SLS samples. The reliability of measures and its influence on roughness parameters is discussed. A procedure for characterising and identifying the sample edges is introduced.

Analysis of Machined Surfaces through Diffraction Patterns and Neural Networks

Abstract The analysis of diffraction patterns obtained from machined surfaces can be used to characterise the microgeometry and, consequently, the production process. Unfortunately, the analysis applied to real surfaces is rather complex. In this paper a new approach based on the technique of the neural networks is proposed to recognise turned surfaces. The diffraction images are acquired and the distributions of the light intensity are used as inputs to the networks. The ability of supervised networks of classifying the surfaces according to the received training is assessed. With unsupervised networks a classification of the surfaces in quality levels is performed.

Wavelet Analysis for Surface Characterisation: an Experimental Assessment

Abstract A new approach based on wavelets for the mathematical treatment of surface roughness is presented. Wavelet theory, firstly developed for the analysis, compression and subband filtering in signal processing, can be used as a tool for the treatment of profiles and surfaces. In this paper the effectiveness of this new application is discussed, considering either synthetic and real surfaces, with the aim of evidencing the peculiarities of this methodology. Moreover, an assessment of the descriptive capability of this approach to identify the main features of the profile is given.

Diffraction pattern analysis for real time monitoring of tool wear in turning processes

Surface micro-geometry is a very important source of information about the chip removal process. Cutting processes are inherently non-stationary due to irreversible changes of the cutting tool geometry. The diffraction patterns obtained by a laser beam illuminating the surface of a workpiece during turning provide useful information to monitor the cutting process. The analysis of diffraction images and the relationships between the image morphology and the geometry of the scattering surface is fundamental for the development of efficient real time control techniques. This paper reports the results of experimental tests indicating the possibility offered by a set of parameters related to the intensity of diffraction images.

CRITERIA FOR GAS NETWORK RENEWAL: EXPERIMENTAL ASSESSMENT OF TRAFFIC LOADS AND CAST IRON JOINT ESCAPES

Abstract Gas escapes from buried pipes depend on many controllable and uncontrollable factors. External mechanical loads, mainly due to traffic loads, are statistically significant especially for cast iron pipes. The assessment of the relationship between displacement of cast iron joints and the traffic load is studied in order to give some criteria for the design of renovation policy. In particular an experimental analysis of the principal traffic parameters, such as weight, speed and wheel-pipe distance, affecting the relative movement of the bell and spigot is carried out. The acquisition of the micrometric movement has been achieved by using a previously developed measurement system based on LVDT sensors. The statistical analysis of the data obtained indicates a strong correlation between weight and joint displacement. Speed of the autovehicles has been found to be not statistically significant.