1,721,025 research outputs found
Fatigue limit prediction of a compression fork-pin coupling of a front motorbike suspension under fully reversed bending load
No full textA methodology to estimate the adhesive bonding defects and the final releasing moments in conical joints based on the acoustic emissions technique
No full textIt is widely demonstrated in literature that the presence and the density of adhesive bonding defects are difficult to estimate with conventional non destructive testing techniques once the parts are assembled together. For this reason it is very important to set up a new methodology capable of estimating the adhesive bonding defect and the final releasing moment of the assembled joints. The purpose of this paper is to verify the performance of the Acoustic Emissions technique when applied, as a non destructive one, in this field. Our investigation aimed to highlight the good correlation between the density of the adhesive defect (low, medium and high) and the cumulative counts of the Acoustic Emissions
Previsione di vita a fatica del perno dello sterzo di una sospensione anteriore motociclistica
No full textLa rottura del collegamento tra il perno di sterzo ed il trapezio di una sospensione anteriore motociclistica o dell’elemento debole (normalmente il perno) risulta estremamente pericolosa per il conducente e l’eventuale passeggero. La probabilità di rottura deve, dunque, essere mantenuta su valori prossimi a zero per tutto il ciclo di vita del prodotto attraverso una accurata caratterizzazione del materiale nelle diverse condizioni di utilizzo e di sollecitazione dei componenti. La conoscenza della resistenza a fatica del perno di sterzo sollecitato, prevalentemente, dal forzamento nel trapezio e da cicli di flessione in presenza di intagli, anche acuti, risulta di fondamentale importanza per una corretta valutazione del rischio di rottura di tale componente. In questo lavoro si è, dunque, deciso di iniziare la caratterizzazione dinamica di tale elemento partendo dalla condizione di carico a flessione alterna simmetrica in presenza del solo intaglio dovuto al forzamento. Tale situazione prevede una condizione di sollecitazione triassiale composta da una sollecitazione principale di flessione alterna simmetrica e da altre due tensioni principali statiche una circonferenziale ed una radiale. La caratterizzazione del materiale è stata verificata sperimentalmente eseguendo una serie mirata di prove di fatica per la determinazione sia del tratto a termine della curva bi-logaritmica σ-N che del limite di fatica a 106 cicli. In entrambi i casi è stato applicato il criterio di Sines ed il metodo Stair Case modificato (metodo Dixon) al fine di prevedere i limiti di fatica
Resistenza a fatica di perni di sterzo per sospensioni motociclistiche soggetti a uno stato di sollecitazione triassiale
No full textFatigue Life Characterisation of Interference Fitted Joints
No full textReversed bending fatigue tests to be performed on full scale assemblies, joined by interference fitting, are very complicated to set up, as well as very expensive to carry out, due to material costs and to low achievable testing frequencies. Moreover, along with the interference level and the shape of the hub edge, the method by which interference is created is deemed to influence the fatigue behaviour of the assembly. A quicker and cheaper way to obtain information about the fatigue behaviour of such assemblies could be performing fatigue tests on down scaled specimens, similar to those suggested by standard ISO 1143. Since no standardized specimen exists for characterising the fatigue behaviour of interference fitted shaft hub joints, the authors designed an ad-hoc specimen (“notched” specimen) and set up a convenient assembly procedure for performing rotating bending fatigue tests. The present investigation focuses on an interference fitted joint, made of EN 10083-2 C40 low carbon steel, whose hub bore edge is rounded. The rationale of the experimentation is retrieving the fatigue stress concentration factor by comparing the endurance limit results of the “notched” specimen to those of a plain specimen manufactured according to ISO 1143. Results were analysed according to standard ISO 12107. Furthermore, a three dimensional numerical model was developed, suitable for evaluating the local stress state of an axisymmetric interference fitted joint. The numerical model accounts for the effect of an external bending moment applied to the shaft. Experimental results are then compared to those given by finite elements analyses, in order to find out the relationship between the fatigue life and the local stress state of interference fitted components
An analytical approach to the structural design and optimization of motorbike forks
No full textFrom a structural standpoint, motorbike forks must withstand the most diverse loading conditions that the normal use of the vehicle implies. By means of experimental analyses, the authors found out the emergency braking to be the most severe loading case. This contribution presents a novel analytical model that, given a few geometric parameters of the motorbike and of the fork, allows calculating the stress field on the legs under braking. The analytical model was designed to account for the unequal stress distribution on the two legs, that arises from the geometrical asymmetry of single brake disc architectures. The model accuracy was tested by comparison with FEA and experimental stress analyses. Finally, the possibility of balancing the loads on the legs of single disc architectures was examined and some structural optimization strategies were proposed
Experimental Analysis of Static and Fatigue Strength Properties in Press-Fitted and Adhesively Bonded Steel–Aluminium Components
No full textPress-fitted and adhesively bonded joints (Hybrid Joints) are increasingly used as an alternative way to
traditional structural joining techniques. The main achievable benefits can be summarized in the possibility
of maximizing the load transfer (torque or axial) and reducing both the weight and the stress field of the
components, by taking advantage of the adhesive strength. Hybrid joints studies can be found in literature
mainly on steel–steel components (Steel Hybrid Joints). The aim of this paper is to provide some relevant
information on the static and fatigue strength properties in the case of steel–aluminium components (Mixed
Hybrid Joints), from the experimental tests performed on a high strength, single-component adhesive which
cures anaerobically. The use of the adhesive increases the press-fitted joint performances, with respect to
its release force: the adhesive static shear strength is about 9 MPa, whereas the adhesive endurance limit is
about 6 MPa, in presence of a stress ratio R = 0.1
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Environmental Management Systems: benefits and barriers to the implementation of ISO 14001:2015
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