E. Guglielmino

Neural-Network-Based System for Novel Fault Detection in Rotating Machinery

The purpose of this research is the realization of a method for machine health monitoring. The rotating machinery of the Refinery of Milazzo (Italy) was analyzed. A new procedure, incorporating neural networks, was designed and realized to evaluate the vibration signatures and recognize the fault presence. Neural networks have replaced the traditional expert systems, used in the past for the fault diagnosis, because they are a dynamic system and thus adaptable to continuously variable data. The disadvantage of common neural networks is that they need to be trained by real examples of different fault typologies. The innovative aspect of the new procedure is that it allows us to diagnose faults, which are not considered in the training set. This ability was demonstrated by our analysis; the net was able to detect the presence of imbalance and bearing wear, even if these typologies of faults were not present in the training data set.

In plane compressive response and crushing of foam filled aluminum honeycombs

In this paper, the influence of foam filling of aluminum honeycomb core on its in-plane crushing properties is investigated. An aluminum honeycomb core and a polyurethane foam with densities of 65, 90, and 145 kg/m3 were used to produce foam filled honeycomb panels, and then experimental quasi-static compression tests were performed. Moreover, finite element model, based on the conducted tests, was developed. In the finite element analyses, three different polyurethane foams were used to fill three different honeycomb cores. The effects of foam filling of aluminum honeycomb core on its in-plane mechanical properties (such as mean crushing strength, absorbed energy, and specific absorbed energy) were analyzed experimentally and numerically. The results showed that the foam filling of honeycomb core can increase the in plane crushing strength up to 208 times, and its specific absorbed energy up to 20 times. However, it was found that the effect of foam filling decreases in heavier honeycombs, producing an increment of the above mentioned properties only up to 36 and 6 times, respectively.

Computed tomography-based reconstruction and finite element modelling of honeycomb sandwiches under low-velocity impacts

The honeycomb sandwiches are widely used in the transportation engineering for the realization of lightweight and crashworthy structures. However their application requires a better understanding of their impact response. Aims of this paper are the numerical investigation of aluminium honeycomb sandwiches subjected to low-velocity impact tests and the validation of finite element (FE) results. Before and after the low-velocity impact tests at different velocities, three dimensional (3D) reconstructions of the honeycomb panels have been carried out by a computed tomographic system in order to acquire exactly the dimension and the shape of the damage and to obtain information about geometry and cells defects. The FE models have been computed from CT data of the undamaged panels. The direct comparison has been done by superimposing the deformed images obtained from FE analyses and from 3D CT space reconstructions. The numerical model was also validated comparing the FE results with experimental data.

Low-velocity impact strength of sandwich materials

Sandwich materials have been widely used in weight-sensitive structures in many fields, especially in the transport industry. There are different classes of sandwiches with a wide range of materials and properties within each type. The aim of this article is the comparison of the impact strength between polymeric and aluminum sandwich structures. Impact tests were carried out by a drop test machine in order to investigate the structural response of the following different topologies of sandwich structures: PVC foam sandwiches and AFS panels. The failure mode and damage have been investigated using two experimental techniques: thermography and 3D Computed Tomography.

Numerical analysis of bone adaptation around an oral implant due to overload stress.

Abstract A finite element (FE) numerical model of an oral implant was implemented with the theory of bone adaptation to predict the response over time of the bone tissue to the implant and to explain a phenomenon regarding the clinical situation: the bone loss due to an overload stress. An adaptation routine [1], based on Beaupré theory, was developed to interface with the FE packages. The value of the mechanical stimulus, corresponding to the overload stress, was evaluated by applying the Taylor crack propagation theory. The predictions obtained by the numerical analyses demonstrated that the overload resorption is blocked only with spongy bone of ‘good quality’.

Infrared investigations for the analysis of low cycle fatigue processes in carbon steels

The infrared thermography has been applied in the past to investigate the high cycle fatigue and to predict the fatigue endurance limit of metals and welded joints. The aim of the present study was to investigate the low cycle fatigue process using an infrared scanner. Experimental tests have been carried out to analyse the low cycle fatigue process of three types of ASTM A 516 gr. 70 steels. The thermal increments during the fatigue life were correlated with the hysteresis loops derived from the traditional procedure. It was demonstrated that an asymptotic temperature increment corresponds to a stable hysteresis loop.

Finite element analysis of foam-filled honeycomb structures under impact loading and crashworthiness design

ABSTRACT The aim of this research is the investigation of foam-filled honeycomb sandwich panels under in-plane impact loading and the analysis of their crashworthiness. This paper presents a finite element analysis of foam-filled honeycomb sandwiches under in-plane impact loading. Three different aluminium honeycombs filled with three different polyurethane foams were considered in the numerical simulation, and results were compared with those obtained for bare honeycomb panels. For what concerns the crashworthiness analysis, the response of the foam-filled honeycomb panels under out-of-plane impacts was compared with those of unfilled honeycomb panels and circular tubes.

Influence of Heat Treatments on Mechanical Behavior of FV520B Steel

Experimental tests have been carried out in order to investigate the influence of the heat treatments on the microstructures and mechanical properties of FV520B stainless steel. The fatigue strength of the common and heat-treated FV520B steels was rapidly assessed using the lock-in infrared thermographic methodology. Good agreements were achieved between the predicted values and those obtained by the traditional testing procedures. The temperature increments during the fatigue tests were tightly linked with the internal microstructural changes. The features of the fatigue fracture surface were observed by the scanning electron microscope. It is found that the fatigue microcracks were initiated from the corner of the specimen surface. The metallographic analysis shows that the improvement of the mechanical properties of FV520B steel is attributed to the formation of the fine-tempered martensite along with the secondary phase particles uniformly distributed at the grain boundary.

A thermography-based approach for structural analysis and fatigue evaluation

The infrared thermography has been developed for Non-Destructive Testing (NDT), stress analysis, and in the last 10 years for metal fatigue assessment. The present research enables to realize these different research objectives all together thanks to an innovative experimental procedure, which includes NDT by lock-in thermography, thermoelastic stress analysis, and fatigue parameters assessment by Rapid Thermographic Method (RTM). The developed procedure has been performed on a set of hole-notched specimens, achieving good results and predictions in a relatively short time. Moreover, the fatigue strength reduction coefficients of the specimens were determined by RTM. This thermography-based approach is dedicated for structural analysis and fatigue evaluation; it is an interesting attempt to apply different thermographic methods to a common research topic.

Thermographic method for very high cycle fatigue design in transportation engineering

With the increasing progress of the technological development in the transport industry, the required fatigue life has increased, so it is very important to determine a safe fatigue strength for 109 cycles. Nowadays, the very high cycle fatigue constitutes one of the main fatigue design criteria for applications in transport industry. In this paper, the infrared thermography and an energetic approach were applied to investigate a tool steel in very high cycle fatigue regime. The traditional energetic approach was developed in order to extend it in very high cycle fatigue regime and to predict the S-N curves. The failure mechanism of the investigated steel was evaluated by means of scanning electron and optical microscopies in order to assess if the nature of microstructure and the metallurgical defects, in terms of inclusions and pores, can influence the crack initiation.