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The wear behaviour and chemical composition of orthodontic components influence the mechanical characteristics of a fixed orthodontic treatment. The purpose of this paper is to evaluate the surface alterations of different types of brackets (aesthetic, metallic, and conventional self-ligating) and archwires (superelastic and thermal) subjected to wear tests through optical microscopy and, subsequently, to identify the chemical elements of accessories by X-ray fluorescence. The cycles (5000 for each bracket and 10,000 for each wire) of the tribological test were carried out in dry conditions inside a machine that allows alternating sliding. The results of the study highlighted different wear behaviours even within the same type of brackets and archwires. The monocrystalline sapphire brackets maintain their aesthetic properties despite traces of wear inside the slots and contain minimal amounts of nickel. Superelastic NiTi archwires have a better overall rating than thermal wires, as they do not show significant surface wear alterations.

Titanium dental implants have had new competitors in recent years, such as fixtures made of zirconia, which promise better aesthetics. The purpose of this study is to evaluate their mechanical performance in silico (Finite Element Analysis). The investigation was performed on a single tooth Patent™ Dental Implant (Zircon Medical®, Altendorf, Switzerland) in two configurations: without offset (Test I) and with offset (Test II, 1.5 mm within the cortical bone). The Patent Implant system consists of two components: the implant with integrated abutment and the fibreglass post. The components of the dental implants were tested using a compression load of 400 N along the implant axis. The results showed that the chewing load generates stress distribution on the bone, therefore, the offset configuration should be avoided.

A correct reproduction of a motorcycle rider’s movements during driving is a crucial and the most influential aspect of the entire motorcycle–rider system. The rider performs significant variations in terms of body configuration on the vehicle in order to optimize the management of the motorcycle in all the possible dynamic conditions, comprising cornering and braking phases. The aim of the work is to focus on the development of a technique to estimate the body configurations of a high-performance driver in completely different situations, starting from the publicly available videos, collecting them by means of image acquisition methods, and employing machine learning and deep learning techniques. The technique allows us to determine the calculation of the center of gravity (CoG) of the driver’s body in the video acquired and therefore the CoG of the entire driver–vehicle system, correlating it to commonly available vehicle dynamics data, so that the force distribution can be properly determined. As an additional feature, a specific function correlating the relative displacement of the driver’s CoG towards the vehicle body and the vehicle roll angle has been determined starting from the data acquired and processed with the machine and the deep learning techniques.

The purpose of this paper is to investigate the variation in the coefficient of friction (CoF) and also the wear in a lead bronze coating under different texture conditions. The tribological tests were performed using a tribometer with pin on disk configuration. Several kinds of textures, realised by a surface laser texturing, were tested by varying the diameter, depth, and density of the dimples under severe working conditions. The innovative aspect concerns the behaviour of the textured lead bronze coating and the lubrication conditions when the sample is subjected to extreme load conditions. Confocal microscopies and SEM (Scanning Electron Microscopy)/EDS (Energy Dispersive X-Ray Spectroscopy) analyses were performed to evaluate the texture behaviour and also the surface deterioration of the coating. The results show that the application of texture processing leads to an improvement in the tribological properties of the coating. By analysing separately the variation of the different geometric parameters of the dimples, it has been shown that the best results are obtained with a diameter of 50 μm, a density of 5%, and a depth of 5 μm.

Background: Repairing a restoration is a more advantageous and less invasive alternative to its total makeover. The aim of this study was to analyze the effects of chemical and mechanical surface treatments aimed at increasing the roughness of a supra-nano composite resin. Methods: 27 cylindrical blocks of microhybrid composite were made. The samples were randomly divided into nine groups (n = 3). The samples&rsquo, surface was treated differently per each group: acid etching (35% H3PO4, 30 s and 60 s), diamond bur milling, sandblasting and the combination of mechanical treatment and acid etching. The samples&rsquo, surface was observed by a scanning electron microscope (SEM) and a confocal microscope for observational study, and surface roughness (Ra) was recorded for quantitative analysis. Results: The images of the samples sandblasted with Al2O3 showed the greatest irregularity and the highest number of microcavities. The surfaces roughened by diamond bur showed evident parallel streaks and sporadic superficial microcavities. No significant roughness differences were recorded between other groups. The difference in roughness between the control group, diamond bur milled group and sandblasted group was statistically significant. (p &lt, 0.01). Comparison between the diamond bur milled group and the sandblasted group was also significant (p &lt, 0.01). Conclusion: According to our results, sandblasting is the best treatment to increase the surface roughness of a supra-nano composite.

The aim of the present work is to investigate the possibility to evaluate the fatigue limit of such a component through the so-called Static Thermographic Method (STM). This new approach has been proposed in 2013 by Risitano and Risitano to determinate the fatigue limit of metallic materials through static tensile tests. Investigating the trend of the surface temperature of the material during static tensile test, the method proposes to correlate the first deviation from linearity of the surface temperature to a damage limit that has been proven to have relation with the fatigue limit. Static tensile tests at different stress rate have been carried out on V-notched specimens. Stepwise fatigue tests have been carried out in order to apply the classic Thermographic Method that has been hugely validated to determinate the fatigue limit of metallic components. Static tests at different stress rate showed that the method is dependent on this parameter; anyway, this dependence does not affect the results achieved in terms of fatigue limit. The experimental results showed a good agreement with the energetic methods considered in the present work.

In the recent years, polyethylene, especially with its highest standard PE100, has been adopted in several industrial fields due to its good mechanical resistance and lightness, combined with low cost. On the other hand, the different manufacturing and working conditions severally affects its mechanical performances, hence extremely time-consuming fatigue tests have to be carried out in order to assess them. The Static Thermographic Method (STM) has been applied to a large set of engineering materials in order to evaluate the limit stress at which the material’s surface temperature trend deviates from the linearity during a static traction test. In the present work, the STM is applied on PE100 in order to investigate its fatigue properties. The limit stress is compared with the fatigue limit obtained by traditional fatigue tests showing good agreement. The STM is a rapid tests procedure able to derive the fatigue properties of the material in a very short amount of time and with a limited number of specimens.

The field of dental implantology has made progress in recent years, allowing safer and predictable oral rehabilitations. Surely the rehabilitation times have also been reduced, thanks to the advent of the new implant surfaces, which favour the osseointegration phases and allow the clinician to rehabilitate their patients earlier. To carry out this study, a search was conducted in the Pubmed, Embase and Elsevier databases; the articles initially obtained according to the keywords used numbered 283, and then subsequently reduced to 10 once the inclusion and exclusion criteria were applied. The review that has been carried out on this type of surface allows us to fully understand the features and above all to evaluate all the advantages or not related. The study materials also are supported by a manufacturing company, which provided all the indications regarding surface treatment and confocal microscopy scans. In conclusion, we can say that, thanks to these new surfaces, it has been possible to shorten the time necessary to obtain osseointegration and, therefore, secondary stability on the part of implants. The surfaces, therefore, guarantee an improved cellular adhesion and thanks to the excellent wettability all the biological processes that derive from it, such as increases in the exposed implant surface, resulting in an increase in bone-implant contact (BIC).

This paper regards the rapid determination of fatigue limit by using thermal data analysis. Different approaches available in the literature to estimate the fatigue limit of cold-drawn AISI 304L bars are analyzed and compared, namely, temperature- and energy-based methods. Among the temperature-based approaches, the Risitano Method (RM) and the method based on material temperature evolution recorded during a static tensile test were analyzed. Regarding the energy-based approaches, the input mechanical energy density stored in the material per cycle (i.e., the area of the hysteresis loop), the heat energy dissipated by the material to the surroundings per cycle, and the &ldquo, 2nd-harmonic-based&rdquo, methods were considered. It was found that for the material analyzed, all the considered energy-based approaches provided a very good engineering estimation of the material fatigue limit compared to a staircase test.

The present paper is the result of the collaboration between the Engineering Department of Messina University and the car company Maserati S.p.A. The aim of this paper is to determine the T-N torsion fatigue curve at R= -1 of the mechanical system "front halfshaft" of an existing car. In particular, experimental fatigue tests were carried out in the laboratories of the Engineering Department of the University of Messina. Torsion fatigue tests of the entire mechanical system were carried out on 15 different front halfshafts. Evaluations of the crack propagation and of failure analysis were made to determine the causes of breakage. In conclusion, the T-N fatigue curve of the mechanical system "front halfshaft" has been obtained.

Since its introduction in pipe applications more than 40 years ago, polyethylene (PE) has been taking a growing place in gas and water distribution due to its low cost, lightness and good corrosion resistance. Besides, long-term properties have been steadily rising due to the development of novel PE-based materials. The present highest standard is the PE100 class. Several laboratory tests are used to extract design data for long-term failure-type prediction based on stress and time to failure relationship. It remains difficult to assess the relation between creep and fatigue loadings on the one side. On the other side, the manufacturing process of the test specimens influences considerably the obtained performance for viscoelastic materials subjected to working conditions. In present paper, the mechanical properties of high-density polyethylene (HDPE), PE 100 class, for pipes were investigated using experimental techniques. Thermographic technique was used during the static tests in order to identify the maximum stress zone and also during the fatigue tests to study the temperature evolution of the specimen. The aim of this study is the application of the Thermographic Method for the fatigue assessment of PE100.

The aim of this paper is to create a new ABS (Antilock Braking System) control system of a Soft-Computing type, on the grounds of the excellent results obtained in the field of automobiles in former studies [1]. Such a system should make it possible to enhance performance in all conditions. The novelty lies in the fact that the system improves not only the physical nature of the hydraulic and electronic components used [2,3], but also the functioning of these, by means of a new control strategy based on a fuzzy-type algorithm optimised with genetic algorithms. In this way the performance of the system may be improved or alternatively the control logic may be simplified for the same degree of performance, offering satisfactory results in all possible conditions. The target performance aimed at may be summarised in two points: reduction in braking distance and improved directional control of the vehicle. The study was optimised on a monocorner model, subsequently to be extended to a complete vehicle model.

The objective of the present investigation was to evaluate how dental implant positioning can influence the masticatory stress distribution over screwed mandibular prosthodontics restoration and over the surrounding bone tissue. Moreover, the dental implant components and overdenture bar strengths under masticatory cycles have been investigated in order to evaluate possible screw and prosthesis breakage. A &ldquo, virtual jaw&rdquo, model and 3D dental implant were reproduced to realise finite element analysis in order to underline the parameters and the mechanical characteristics of the bone and of the dental implants connected to the overdenture bar. The distribution of a nonspecific chewing phase, analysing the overall load on the fixtures of the lower jaw, was performed. The study investigating frontal and horizontal planes and vertical directions of occlusal forces showed how position and perspective of fixtures strongly influenced the stress distribution and the consequent jawbone tissue remodelling. Prostheses elements such as cantilever, passing screws, and dental implants are strictly related to the correct selection of dental implant position. This study suggested a virtual method to guide the surgeon in the choice of implant number, position, diameter, and length, and cantilever length and shape, and to evaluate the prospective stress distribution of chewing strengths for a correct prosthesis rehabilitation.

In this work, more specimens were tested at equal conditions (static compression test) and, during the tests, the released heat for irreversible phenomena was monitored by means of the analysis of the temperature surface of the specimen. In this way, it was possible to estimate the average value of the macroscopic stress (“critical stress”) for which local micro cracks begin. The compression static tests (load - machine time) and the related thermal analysis (temperature-machine time) of spots located on the specimen face of the specimens, highlighted the possibility to estimate the value of the compressive load to which there was loss of linearity in the temperature - machine time diagram (Δt-t). This effect is due to internal heat generated for irreversible phenomena (internal micro fractures). The results show that the “critical stress” has values practically coincident for the points (spots) located in different zones (center or corners of the specimens' surface).

The traditional methods of fatigue assessment of metallic and composite materials are extremely time consuming. The thermographic measurements during static tests can be used to predict the fatigue limit. This procedure has been already applied to composite materials. The aim of this study is the application of this procedure for the fatigue assessment of steel welded joints. Static tensile and fatigue tests were carried out on butt welded specimens, made of S355 steel. Two full-field techniques were applied during the tests: digital image correlation and infrared thermography techniques. Fatigue tests at increasing loads were performed by a stepwise succession in order to apply the Thermographic Method. The value of the fatigue limit, obtained by the traditional procedure, was compared with the values predicted by means of the Thermographic Method during stepwise succession fatigue tests and by means of the infrared thermography technique during static tensile tests. The predicted values are in good agreement with the experimental values of fatigue life.

Estimation of the fatigue limit for steel ductile materials using non-destructive methods is a topic of great interest to researchers today. In recent years, the method adopted has implemented infrared sensors to detect the surface temperature and correlate it with the fatigue limit. In previous paper, a new energy approach was proposed to investigate the fatigue limit during tensile test. The numerical procedure proposed by Chrysochoos is adopted to clean infrared images and applied to analyse the surface heat sources during tensile test. AISI 304 specimens with rectangular cross-sections are tested. Moreover fatigue tests at increasing loads were carried out on steel by a stepwise succession, applied to the same specimen, for applying the thermographic method. The predictions of the fatigue limit, obtained by the analysis of the energy evolution during the static tests, were compared with the predictions obtained applying the thermographic method during fatigue tests.

Le esperienze maturate nel campo dell’analisi termica di materiali utilizzati nelle costruzioni meccaniche [1,2,3] hanno permesso di evidenziare come il rilievo della temperatura (terzo parametro) in prove statiche e dinamiche costituisca un indicatore molto importante ai fini della caratterizzazione dinamica del materiale. Essendo il rilascio termico funzione dell’energia applicata per portare a rottura il materiale, il rilievo di parametri ad esso legati, induce a nuovi ipotesi e definizioni di limiti di fatica e resistenza a tempo. Mediante l’analisi termica è possibile valutare anche parametri correlabili con il valore limite di energia a rottura Eldel materiale. In [4] era stato già messo in evidenza da A. Risitano e Altri che, in prove statiche di trazione, l’inizio della zona di prima plasticizzazione del materiale, in termine di tensione, era osservabile dalla curva di variazione di temperatura ΔT con il procedere della prova. Nello stesso lavoro si evidenziava come la velocità di prova avesse poca influenza sui valori della variazione di temperatura specialmente durante la fase elastica. Operando con sensori sempre più precisi e per obbiettivi rivolti alla ricerca dell’energia limite a rottura è stato osservato dagli autori che il seguire la variazione della temperatura sulla superficie del provino, in prove statiche di trazione, permette di legare i classici valori di resistenza all’oscillazione σ0 con una “temperatura limite” T0 corrispondente all’inizio di andamenti non lineari della stessa. In questa sede si evidenzia un modello di comportamento fisico del materiale durante le prova di trazione che giustifica, in modo semplice, la capacità di risalire, attraverso la conoscenza sperimentale del limite di comportamento termo-elastico, ai classici parametri di resistenza a fatica. Viene riportato, a titolo di esempio, il risultato relativo a provini piatti forati in acciaio facenti parte di una serie utilizzati per altri scopi (formeranno oggetto di altra pubblicazione) con i quali anche mediante prova statica si è determinata la loro resistenza all’oscillazione.

A variety of technologies are employed to reduce ground borne vibrations near railway lines. In this paper, the performances of different signal-processing algorithms are discussed in an effort to define an optimized methodological approach for evaluating the reduction potential of mitigation techniques. Different post-processing analysis methods have been applied to acceleration data collected during the passage of a train in order to evaluate the performance of a trench realized to improve the quality of life near railway lines. RMS computation at steady-state and amplitude of frequencies in the averaged spectra were used as a first assessment procedure, while joint time–frequency analysis were used for the characterization of the signals during transients. The possibilities provided by wavelet techniques were then investigated and compared with those of the classical Fourier analysis. Experimental results show that the wavelet approach can be used both to evaluate the effectiveness of the mitigation techniques, and to analyze the structure of the acceleration signals generated by trains.

The mechanical properties of injection moulded short glass fibre-reinforced polyamide composites was investigated using experimental techniques. The Digital Image Correlation technique was applied during the tensile tests in order to obtain the stress–strain curves and to identify the fracture location at the early stages of the tests. Moreover, the thermographic technique was used during the static tests in order to identify the fracture zone and also during the fatigue tests, carried out at different frequencies, to study the temperature evolution of the specimen. A theoretical model was developed to analyze the temperature evolution during the fatigue test and the effect of the test frequency. The aim of this study is the application of the Thermographic Method for the fatigue assessment of short glass fibre-reinforced polyamide composites.

There are many studies in literature on the thermal response of composites during static tests for a prediction of the fatigue limit, but only few studies about the thermal response of steels during static tests, and, as far as the authors are aware, this study is the first one about the application of the Thermographic Method during static tensile tests for the fatigue assessment of steel welded joints. Tensile tests were carried out on base material and welded specimens, made of S690QL steel. The Digital Image Correlation and thermographic techniques have been used during all tests. Moreover fatigue tests at increasing loads were carried out on steel base material and welded specimens by a stepwise succession (applied to the same specimen) for applying the Thermographic Method. The predictions of the fatigue limit, obtained by the analysis of the temperature evolution during the static tests, were compared with the predictions obtained applying the Thermographic Method during fatigue tests.

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.

Nowadays, many components and structures are subjected to fatigue loading with a number of cycles higher than 107. In this scientific work, the behaviour of two kinds of tool steel was investigated in very high cycle fatigue regime. The fatigue tests were carried out at the frequency of 20 kHz and in fully reversed tensioncompression mode (R = -1) by means of an ultrasonic fatigue testing equipment. The radiometric surface temperature was detected during all the test by means of an IR camera in order to extend the Thermographic Method and the Energetic Approach in very high cycle fatigue regime. The failure mechanism of the investigated steels was evaluated by means of several experimental techniques (scanning electron microscopy, Energy Dispersive X-ray spectroscopy and Optical Microscopy).

The quickly identify of fatigue limit of a mechanical component with good approximation is currently a significant practical problem not yet resolved in a satisfactory way. Generally, for a mechanical component, the fatigue strength reduction factor ( ? i) is difficult to evaluate especially when it is in service. In this paper, the procedures for crack paths individuation and consequently damage evaluation (adopted in laboratory for stressed specimens with planned load histories) are applied to mechanical components, already failed during service. The energy parameters, proposed by the authors for the evaluation of the fatigue behavior of the materials [1-5], are defined on specimens derived from a flange bolts. The flange connecting pipes at high temperature and pressure. Due to the loss of the seal, the bolts have been subjected to a hot flow steam addition to the normal stress. The numerical analysis coupled experimental analysis (measurement of surface temperature during static and dynamic tests of specimens taken from damaged tie rods), has helped to determine the causes of failure of the tie rods. The determination of an energy parameter for the evaluation of the damage showed that factors related to the heat release of the material (loaded) may also help to understand the causes of failure of mechanical components.

Partendo dalla osservazione che provini precedentemente danneggiati hanno un limite di fatica differente (vedi Miner) viene esaminato il comportamento di un acciaio soggetto a serie di carichi affaticanti al fine di verificare la conseguente risposta termica. L’esame, mediante analisi termica, delle prove di fatica su provini di acciaio C40 danneggiati a diverso grado, da interessanti indicazioni sul ruolo dei carichi applicati in relazione alla possibilita di produrre danno nel materiale. Viene messo in evidenza come la temperatura, conseguenza dell’energia consumata dal provino, possa essere elemento indicativo dello stato del materiale. Vengono riportate le curve di fatica e le curve di temperatura di provini lisci sottoposti a storie di carico diverse. Da esse si puo evincere che mentre e valida la legge di linearita del danno (?ini/Ni= cost), la curva definita secondo la regola del Miner-Manson (?ini/Ni=1), che tiene solo conto del numero di volte in cui la tensione supera il limite di fatica del materiale (provini lisci), invece, non sempre rispecchia il reale stato di danno. Questo specialmente quando si e in presenza di carichi prossimi al limite di fatica che, per la sequenza dell’applicazione, possono diventare carichi affaticanti.

This work reports fatigue stress test results for AISI 304 steel ( R = −1) that has been subjected to a high cycle number. It shows that the energetic effect (employing different temperature increments for equal loading of uniaxial stress) can be used to evaluate the cumulative damage caused by any prior loading. Various load histories were applied to AISI 304 specimens, and the resulting damage was evaluated in reference to the energy factor, Φ , which is dependent on the maximum temperature at the sample surface when irreversible plastic deformation begins. The time curves (Wohler curves) and the damage ratio based on the consumed energy were compared to those obtained according to Palmgren–Miner rules; this comparison served to show how under-evaluations can occur with high damage ratios.

Parkinson's disease (PD) is a progressive neurodegenerative disorder related to the loss or absence of dopaminergic neurons in the brain. These deficits result in slowness of movement, tremor, rigidity, and dysfunction of behaviour. These symptoms negatively influence the patient’s capability to carry out the daily oral hygiene manoeuvres. The aim of this work is to record the oral health condition of PD patients evaluated at the IRCSS Bonino-Puleio in Messina. The oral health of 45 consecutive PD patients (study group) with neurologic diagnosis based on United Kingdom Brain Bank Criteria has been compared with that of another 45 no PD patients of the same age (control group). The evaluation of the general oral condition was recorded underlining tooth loss, active periodontal disease, and presence of untreated caries. The frequency of untreated caries, periodontal diseases, and missing teeth of the study group was significantly higher than in control group. Based on the data results, clinicians should direct high attention to the oral hygiene of patients with PD, above all at the early stages of the caries or periodontal disease, in order to prevent serious evolution of those pathologic dental conditions that may finally result in the tooth extraction event.